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This study evaluates the impact of dietary supplementation of the blue-green alga Arthrospira platensis NIOF17/003 nanoparticles (AN) on the growth performance, whole-body biochemical compositions, blood biochemistry, steroid hormonal, and fry production efficiency of Nile tilapia (Oreochromis niloticus) broodstock, during the spawning season. After a 21-day preparation period to equip the females and ensure that their ovaries were filled with eggs, mating between the mature females and males took place in a 3:1 ratio during a 14-day spawning cycle. A total of 384 tilapia broodstock 288 females and 96 males with an initial body weight of 450.53±0.75, were divided into four groups; AN0: a basal diet as a control group with no supplementation of Arthrospira platensis, and the other three groups (AN2, AN4, and AN6) were diets supplemented with nanoparticles of A. platensis at levels of 2, 4, and 6 g kg─1 diet, respectively. The results found that fish-fed group AN6 showed the highest significant differences in weight gain (WG), final weight (FW), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed efficiency ratio (FER). Females fed the AN6 diet showed the highest significant fat content. Compared to the AN0 group, fish fed on the supplemented diets showed significant improvement (p < 0.05) in triglyceride, glucose, and aspartate aminotransferase (AST). A gradual increase in AN inclusion level resulted in a gradual increase in the concentrations of luteinizing hormone (LH), and follicle-stimulating hormone (FSH), testosterone, progesterone, and prolactin. The rates (%) of increase in fry production for females fed supplemented diets were 10.5, 18.6, and 32.2% for AN2, AN4, and AN6, respectively, compared to the control group. This work concluded that the inclusion levels of 6 g kg─1 of A. platensis nanoparticles in the diet of Nile tilapia broodstock significantly improved the growth performances, steroid hormone concentrations, and increased the fry production efficiency by 32.2%, respectively. These findings revealed that A. platensis nanoparticles resulted in a significantly enhanced female' reproductive productivity of Nile tilapia broodstock. [ABSTRACT FROM AUTHOR]

The sei whale (Balaenoptera borealis) is an important species among baleen whales in the North Pacific and plays a significant role in the ecosystem. Despite the importance of this species, information regarding its migration patterns and breeding locations remains limited. To enhance the understanding of the phenology of North Pacific sei whales, we deployed satellite-monitored tags on these whales in the western and central North Pacific from 2017 to 2023. We fitted 55 sei whale tracks to a state-space model to describe the whales' seasonal movements at feeding grounds and their migratory behavior. The whales typically leave their feeding grounds between November and December, with migration pathways extending from off Japan to the west of the Hawaiian Islands. These southward transits converge in the waters of the Marshall Islands and north of Micronesia between 20° N and 7° N, which appear to be breeding grounds. After a brief stay at these breeding grounds, the whales migrate northward from January to February, reaching their feeding grounds around 30°N by March. To the best of our knowledge, this is the first study to present the phenology of feeding and breeding seasons and the migration pattern of North Pacific sei whales. [ABSTRACT FROM AUTHOR]

Many marine organisms broadcast gametes for external fertilization, thus conspecifics need to concentrate the time of gamete release through synchronization with environmental factors. We investigated the timing of spawning in two sea urchin species, Tripneustes gratilla and Toxopneustes pileolus, by assessing the spawning potential of individuals using both surveys and experiments in southern Taiwan from March to November 2010. We developed a new method to observe the spawning potential without sacrificing any individuals, defining those individuals‐initiated spawning within 30 min after 10 s of exposure to air as having the spawning potential. We discovered that the percentage of individuals with spawning potential, that is, the spawning ratios of the population, varied greatly from 0% to 80% in To. pileolus and from 0% to 50% in Tr. gratilla within the reproductive seasons. We evaluated the possibility of a lunar/semilunar rhythm of spawning ratios of the population and tested three environmental factors, that is, light intensity, tide, and temperature that could potentially affect the spawning potential of the sea urchins by experiments. Individuals with spawning potential were neither randomly nor evenly distributed among days but were aggregated on certain days; however, no lunar/semilunar rhythm of the spawning ratios was detected within the reproductive season. The possible role of the tidal factor within a day was not found in experiments in either species. However, when water temperature was >27°C in our surveys, significantly higher spawning ratios were observed in To. pileolus, but not in Tr. gratilla in the reproductive season. A further temperature experiment in To. pileolus supported the positive role of high temperature on the spawning ratios of individuals. In addition, To. pileolus was more likely to spawn during the day than at night, and the light/dark experiments suggested that the spawning potential was controlled by an endogenous biological clock rather than by the ambient light conditions directly. The lack of rhythmic pattern and yet concentrated spawning of these sea urchins may be adaptive to avoid predation. [ABSTRACT FROM AUTHOR]

The Ophiuroidea, the most diverse echinoderm class, exhibits an array of life history patterns and larval forms, the evolution of which is poorly understood. With a robust phylogeny available for the major family, the Ophiocomidae, we undertook an assessment of the evolution of development in these ophiuroids. We spawned 15 species and documented larval development in 14 of these. In total, data on egg size or larval development were available for 27 species across the four recognized genera (Breviturma, Ophiocoma, Ophiocomella, and Ophiomastix). Ophiocomids have a bimodal egg size distribution. Species with small eggs (x̄ = 82 μm diameter, range 55–100 μm diameter) and large eggs (x̄ = 424 μm diameter, range 335–550 μm diameter) have planktotrophic ophioplutei and lecithotrophic vitellariae, respectively. The advanced ophiopluteus transforms into an armless vitellaria prior to metamorphosis through resorption of the larval arms and rearrangement of the ciliary tracts into series of transverse bands. Thus, the Type II pattern of development (which includes both the ophiopluteus and vitellaria) may be characteristic of the Ophiocomidae. This is not seen in other ophiuroid families. Evolution of nonfeeding (lecithotrophic) development through a vitellaria larva appears to have occurred only once in this family, in the genus Ophiomastix. Several traits appear to be specific to some species or genera, including an ornate fertilization envelope (Ophiocoma species), the presence of an early barrel‐shaped larva (Breviturma species), and the presence of vibratile lobes in advanced ophioplutei (Breviturma, Ophiocomella). In species with lecithotrophic development, the vitellaria is distinct, with prominent ciliated lobes around the developing juvenile rudiment. Larval form may assist with identification of ophiocomid larvae in plankton samples. [ABSTRACT FROM AUTHOR]

The coral Acropora spp., known for its reef-building abilities, is a simultaneous hermaphroditic broadcast spawning species. Acropora spp. release gametes into seawater, activating sperm motility. This activation is mediated by adenylyl cyclase (AC) and protein kinase A (PKA). Notably, membrane-permeable cAMP (8-bromo-cAMP) promotes sperm motility activation of Acropora florida. While the signal transduction for PKA-dependent motility activation is highly conserved among animals, the downstream signaling of PKA remains unclear. In this study, we used mass spectrometry (MS) analyses to identify sperm proteins in the coral Acropora digitifera, as well as the serine/threonine residues of potential PKA substrates, and then, we investigated the conservation of these proteins from corals to vertebrates. We identified 148 sperm proteins of A. digitifera with typical PKA recognition motifs, namely RRXT and RRXS. We subsequently used ORTHOSCOPE to screen for orthologs encoding these 148 proteins from corals to vertebrates. Among the isolated orthologs, we identified positive selection in 48 protein-encoding genes from 18 Acropora spp. Subsequently, we compared the conservation rates of the PKA phosphorylation motif residues between the orthologs under positive and purifying selections. Notably, the serine residues of the orthologs under positive selection were more conserved. Therefore, adaptive evolution might have occurred in the orthologs of PKA substrate candidates from corals to vertebrates, accompanied by phosphorylation residue conservation. Collectively, our findings suggest that while PKA signal transduction, including substrates in sperm, may have been conserved, the substrates may have evolved to adapt to diverse fertilization conditions, such as synchronous broadcast spawning. [ABSTRACT FROM AUTHOR]

Increasing ocean temperature will speed up physiological rates of ectotherms. In fish, this is suggested to cause earlier spawning due to faster oocyte growth rates. Over time, this could cause spawning time to become decoupled from the timing of offspring food resources, a phenomenon referred to as trophic asynchrony. We used biological data, including body length, age, and gonad developmental stages collected from >125,000 individual Northeast Arctic cod (Gadus morhua) sampled between 59 and 73° N in 1980–2019. Combined with experimental data on oocyte growth rates, our analyses show that cod spawned progressively earlier by about a week per decade, partly due to ocean warming. It also appears that spawning time varied by more than 40 days, depending on year and spawning location. The significant plasticity in spawning time seems to be fine‐tuned to the local phytoplankton spring bloom phenology. This ability to partly overcome thermal drivers and thus modulate spawning time could allow individuals to maximize fitness by closely tracking local environmental conditions important for offspring survival. Our finding highlights a new dimension for trophic match–mismatch and should be an important consideration in models used to predict phenology dynamics in a warmer climate. [ABSTRACT FROM AUTHOR]

Trophic polymorphism and temporal reproductive isolation are the drivers of sympatric differentiation in many fish taxa. We present a new case of ecologically based diversification of Arctic charr in a Transbaikalian mountain lake inhabited by reproductively isolated dwarf and normal forms. These forms differ in size, diets and morphology and breed, respectively, in April–May and in September–October representing a rare example of sympatric spring- and autumn-spawning charr pair. Microsatellite analysis reveals clear-cut genetic differences and low-level hybridization between them. Dwarf form charr are planktivorous and manifest uniform slow growth. Normal form charr, though genetically homogeneous, are highly heterogeneous in size-at-age. They are subdivided into omnivorous small-size and piscivorous large-size groups, which can be considered as incipient forms at an early divergence stage. As evidenced by back-calculated growth data, their size-at-age heterogeneity results from highly variable individual growth patterns, which include different combinations of slow and fast growth periods presumably associated with spawning and non-spawning years. Growth acceleration in late ontogeny may result in the transformation of some normal charr from the smaller into the larger group during their lifetime. [ABSTRACT FROM AUTHOR]

Seagrass habitats play a major role in fisheries productivity through nursery functions and feeding grounds for diverse fish species. However, little is known about the seasonal distribution of fish larvae at large spatial scales in coastal East Africa. We investigated drivers of the seasonal fish larvae abundance and composition in seagrass habitats in Kenya and Tanzania. We found a high diversity of fish larvae (54 families) inhabiting seagrass habitats that differed between sites and seasons. Fish larvae abundance were highest in Kenya, particularly during the northeast monsoon season. Overall, total larval abundances per site were low, reaching less than 190 individuals/100 m3 in Kenya and less than 40 individuals/100 m3 in Tanzania, likely related to the low productivity and strong hydrodynamic processes in this region. Our data suggests that most of the fish spawn year-round in these tropical waters as we did not find strong seasonal patterns. All sites had a high relative abundance of larvae from demersal spawning fishes, indicating that many fish species move to coastal sites for spawning. Primary productivity and dissolved oxygen, driven by hydrodynamics conditions are positively related to fish larvae productivity both in Kenya and Tanzania. These findings indicate that the occurrence of both resident and transient fish larvae in seagrass meadows is driven by strong hydrodynamic and tidal processes that transport fish larvae across adjacent habitats. [ABSTRACT FROM AUTHOR]

The sei whale (Balaenoptera borealis) is an important species among baleen whales in the North Pacific and plays a significant role in the ecosystem. Despite the importance of this species, information regarding its migration patterns and breeding locations remains limited. To enhance the understanding of the phenology of North Pacific sei whales, we deployed satellite-monitored tags on these whales in the western and central North Pacific from 2017 to 2023. We fitted 55 sei whale tracks to a state-space model to describe the whales' seasonal movements at feeding grounds and their migratory behavior. The whales typically leave their feeding grounds between November and December, with migration pathways extending from off Japan to the west of the Hawaiian Islands. These southward transits converge in the waters of the Marshall Islands and north of Micronesia between 20° N and 7° N, which appear to be breeding grounds. After a brief stay at these breeding grounds, the whales migrate northward from January to February, reaching their feeding grounds around 30°N by March. To the best of our knowledge, this is the first study to present the phenology of feeding and breeding seasons and the migration pattern of North Pacific sei whales. [ABSTRACT FROM AUTHOR]

The round goby (Neogobius melanostomus) is an invasive benthic fish first introduced to the Laurentian Great Lakes in 1990 that has negatively impacted native fishes through increased competition for food and habitat, aggressive interactions, and egg predation. While complete eradication of the round goby is currently not possible, intensive trapping in designated areas during spawning seasons could potentially protect critical native fish spawning habitats. Baited minnow traps were spaced 10 meters apart in shallow water along a 100-meter stretch of shoreline within the Duluth-Superior Harbor during the round goby breeding period (June to October) with captured round gobies removed from interior traps (N = 10) every 48 hours. These traps were bracketed by two pairs of reference traps deployed weekly for 48 hours, from which round gobies were also tagged and released. The number of round gobies captured in the interior traps declined by 67% compared to reference traps over the course of the study, with extended periods of no captures. The tagged round gobies showed high site affinity, with 82.8% of tagged fish recaptured at the previous release site. The results indicate that even at open water sites, which allow natural migration of round gobies into the area, extensive trapping could reduce local population numbers. [ABSTRACT FROM AUTHOR]

Oviposition is induced upon mating in most insects. Spawning is a physiological process that is fundamental for the reproduction of Scylla paramamosain. However, the molecular mechanisms underlying the spawning process in this species are poorly understood. Herein, comprehensive ovary transcriptomic analysis was conducted at the germinal vesicle breakdown stage (GVBD), spawning stage, 0.5 h post‐spawning stage, and 24 h post‐spawning stage of S. paramamosain for gene discovery. A total of 67,230 unigenes were generated, and 27,975 (41.61%) unigenes were annotated. Meanwhile, the differentially expressed genes (DEGs) between the different groups were identified, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was subsequently conducted. These results suggested that octopamine (OA) and tyramine (TA) could induce oviposition, while dopamine (DA) and serotonin (5‐hydroxytryptamine [5‐HT]) inhibit oviposition. The 20‐hydroxyecdysone (20E) and methyl farnesoate (MF) signal pathways might be positively associated with oviposition. Furthermore, numerous transcripts that encode neuropeptides and their G‐protein‐coupled receptors (GPCRs), such as CNMamide, RYamide, ecdysis‐triggering hormone (ETH), GPA2/GPB5 receptor, and Moody receptor, appear to be differentially expressed during the spawning process. Eleven unigenes were selected for qRT‐PCR and the pattern was found to be consistent with the transcriptome expression pattern. Our work is the first spawning‐related investigation of S. paramamosain focusing on the ovary at the whole transcriptome level. These findings assist in improving our understanding of spawning regulation in S. paramamosain and provide information for oviposition studies in other crustaceans. [ABSTRACT FROM AUTHOR]

Simple Summary: Environmental factors, maternal inheritance, and feeding success are influential factors in fish growth, especially during the larval stage, encompassing their early days of life. Growth rates play a crucial role in larval survival, particularly in species with high energy requirements such as the Atlantic bluefin tuna (ABFT). Our analyses of two patches of ABFT larvae collected in the Gulf of Mexico's spawning region during different years reveal variable larval growth, depending on prey availability. Larval growth also shows a direct relationship to maternal feeding. Estimates of larval trophic positions are primarily influenced by food web length and energy transmission efficiency, leading to differences in larval growth and underscoring the importance of considering trophic dynamics in interpreting results. These findings offer novel insights into how these factors affect ABFT larval growth, potentially informing conservation efforts and fisheries management strategies by governmental institutions. Two cohorts of Atlantic bluefin tuna (Thunnus thynnus) larvae were sampled in 2017 and 2018 during the peak of spawning in the Gulf of Mexico (GOM). We examined environmental variables, daily growth, otolith biometry and stable isotopes and found that the GOM18 cohort grew at faster rates, with larger and wider otoliths. Inter and intra-population analyses (deficient vs. optimal growth groups) were carried out for pre- and post-flexion developmental stages to determine maternal and trophodynamic influences on larval growth variability based on larval isotopic signatures, trophic niche sizes and their overlaps. For the pre-flexion stages in both years, the optimal growth groups had significantly lower δ15N, implying a direct relationship between growth potential and maternal inheritance. Optimal growth groups and stages for both years showed lower C:N ratios, reflecting a greater energy investment in growth. The results of this study illustrate the interannual transgenerational trophic plasticity of a spawning stock and its linkages to growth potential of their offsprings in the GOM. [ABSTRACT FROM AUTHOR]

The physiological state of mature brood fish is a determining factor for achieving and stimulating a successful spawning process in captivity. In this 2- year investigation, the physiology of mature Liza ramada females was examined throughout the day at various times (24 hours) to ascertain the most suitable time for obtaining mature females raised in both saline water and fresh water in addition to handling them during the spawning season. In addition, blood concentrations of hormones involved in growth, acclimatization, and response to stress, as well as the levels of glucose, total protein, albumin, and the albumin: globulin ratio of L. ramada mature females were all investigated with respect to the factor of time during a period of 24hours. The highest levels of growth hormone, thyroxine, triiodothyronine, prolactin, cortisol, total protein and albumin were recorded at 12 midday and 6 in the morning for mature L. ramada females raised in both saline water and fresh water, respectively. These recorded levels were suitable for attaining a successful spawning and concurrently stimulating the process for L. ramada raised in captivity. Average levels of glucose were recorded for these fish at the aforementioned times. Low levels of the mentioned hormones, total protein, and albumin were observed at 6PM in fish raised in both saline and fresh waters. These hormones play a significant role in growth, acclimatization, stress response during handling, and stimulating spawning of L. ramada. In conclusion, it was proved that the optimal times for obtaining and handling mature L. ramada females during spawning induction are at 12PM for fish raised in saline water and 6AM for fish raised in fresh water. [ABSTRACT FROM AUTHOR]

Pterygoplichthys pardalis is an invasive fish species that grows rapidly in Lake Tempe, Kabupaten Wajo, and has disturbed the existence of native, endemic, and introduced fish. This study aimed to analyze the reproductive biology of this species in terms of population control. The research was conducted from January to April 2023 at Tempe Lake, Wajo Regency, South Sulawesi. Fish samples were caught using gill nets, cleaned, and stored in a coolbox for observation in the laboratory. Reproductive biology observations began with the separation of male and female fish, measuring the length and weight of each with a fish measuring board and analytical scales. Samples were dissected for maturity gonad and fecundity observations. Length-frequency distribution of male fish ranged from10.08- 41.58cm, while that of female fish ranged from 10.08- 35.28cm. The overall sex ratio between male and female fish was 1:1 (balanced), while the sex ratio between mature males and females (maturity stage IV) was 1:2 (polygamy). The growth pattern exhibited a negative allometric trend, with a long spawning season reaching its peak in March. The species is considered a partial spawner. The length at first maturity of gonads (Lm) for male and female fish were 28,99 and 25.98cm, respectively. Moreover, the fecundity ranged from 201- 5,050 eggs with an average of 1,762± 966 eggs. [ABSTRACT FROM AUTHOR]

The thin-lipped grey mullet, Liza ramada, a commercially significant fish in Egypt, was studied for its expression patterns along the brain-pituitarygonad axis in female L. ramada during the spawning season of 2022 in both captive and wild habitats. The inspected genes included Kiss2, Gpr54, Gnrh1, and Drd2 genes in the brain and ovary, as well as Lhβ, Fshβ, and Slα genes in the pituitary and ovary. Relative expressions of all studied genes either in the brain, or pituitary, and ovary were higher in ripe females than in immature ones. Captive females had higher Drd2 gene expressions; nevertheless, mature wild females had higher expression values for the other investigated genes that were measured in the brain, or pituitary and ovary. The study found correlations between gene expression patterns in wild and captive females (P< 0.05), suggesting that confinement may affect reproductive physiology. The findings suggest focusing on hormones for artificial fertilization therapies in confined females. [ABSTRACT FROM AUTHOR]

Queen triggerfish Balistes vetula is an important reef-associated species for commercial fisheries in the U.S. Caribbean. It exhibits a relatively unique reproductive strategy as a nesting benthic spawner, investing substantial energy in territorial defense, building and maintaining nests, and caring for fertilized eggs during the reproductive season. Prior to this study, no comprehensive life history information existed in the literature for queen triggerfish. This study provides the first comprehensive documentation of age, growth, size/age at sexual maturity, reproductive seasonality, and reproductive output for a Balistes species in the Caribbean. From 2013 to 2023, we collected 2190 fish samples from fisheries-dependent and -independent sources from the waters of Puerto Rico and the U.S. Virgin Islands. Fish ranged from 67 to 477 mm fork length (FL). We documented that queen triggerfish is sexually dimorphic with males attaining larger mean sizes-at-age compared to females and the species is characterized by a moderately young age at median sexual maturity (A50 = 3.3 y). The maximum age for our U.S. Caribbean samples was 23 y based on increment counts from otoliths. Spawning season encompassed the months of December to August in the region, and female spawning frequency ranged from an estimated 2 to 84 times per year; female spawning frequency increased with increasing size and age of fish. We documented that commercial fishers in the U.S. Caribbean mainly target "plate-size" individuals, defined in our study as 235–405 mm FL, which appears to act as a self-imposed slot size range limit and results in the fishery not removing individuals in the smallest and largest size groups at high rates. The percentage of immature fish from fisheries-dependent sources was close to 0 (0.8%). Commercial fishing for queen triggerfish in the region currently appears to be sustainable, but monitoring of the population should continue. [ABSTRACT FROM AUTHOR]

Squid Lolliguncula panamensis Berry, 1911 is of commercial and ecological importance in the Gulf of Tehuantepec (southeastern Mexico). This study examines the mode of oocyte development, packing in the ovary, and spawning pattern of this understudied species. Lolliguncula panamensis presents a synchronous oocyte growth in batches, with multiple spawnings, with the presence of post-ovulatory follicles and atretic follicles, including the constant presence of pre-vitellogenic and vitellogenic oocytes. The size frequencies of oocytes of ripe ovaries exhibit a pronounced morphological and size separation between the late yolk stage and mature oocytes, suggesting that the oocytes pass through this size range very fast. These oocytes adopt a geometrical shape that makes their packing efficient for spawning. One three-dimensional packing of vitellogenic oocytes (scutoid type) in the ovary was observed. The results of our study suggest that the spawning behavior of Lolliguncula panamensis may constitute an opportunistic reproductive strategy in which individuals present multiple spawnings over a brief period. We suggest that this strategy might be a response to complex regional oceanographic conditions of the Gulf of Tehuantepec. [ABSTRACT FROM AUTHOR]

The Northeast Atlantic mackerel is an income breeder with indeterminate fecundity, spawning in multiple batches at optimal temperatures around 11°C in the upper water column during February–July along the continental shelf from 36–62°N. Based on macroscopic staging of gonads (N ∼62000) collected in 2004–2021, we detected an on-going extension of spawning activities into the Norwegian Sea feeding area (62–75°N), reaching stable levels around 2012 onwards. This poleward expansion increased as more fish entered the area, whilst the maximum proportions of spawners concurrently dropped from about 75 to 15% from May to July. Detailed histological examinations in 2018 confirmed the macroscopic results but clarified that 38% of the spawning-capable females in July terminated their spawning by atresia. We suggest that increased access to suitable spawning areas (≥10°C), following ocean warming from 2002 onwards, functions as a proximate cause behind the noticed expansion, whereas the ultimate trigger was the historic drop in body growth and condition about 10 years later. Driven by these energetic constraints, mackerel likely spawn in the direction of high prey concentrations to rebuild body resources and secure the future rather than current reproduction success. The ambient temperature that far north is considered suboptimal for egg and larval survival. [ABSTRACT FROM AUTHOR]

Received wisdom has argued that large protected areas are superior to small reserves, based on island biogeography theory, economies of scale, and the need to sustain viable populations of top predators and other large ranging or dispersive species. But this position overlooks evidence that, for many species, strategically placed smaller reserves are extremely important, especially in areas highly altered by humans. Many countries are reluctant or unable to designate additional large protected areas. We provide evidence that carefully designed support networks of smaller protected areas can be an important complement to activities to reach the Global Biodiversity Framework's target of 30% of the planet in protected and conserved areas by 2030. We identify seven benefits from small reserves, when correctly located and well-managed: (1) conserving critical habitat of range-limited or relic species; (2) conserving remaining areas of sensitive or threatened habitat in altered ecosystems; (3) conserving habitat for sensitive, time-limited lifecycle stages, such as raptor nesting sites and fish spawning grounds; (4) maintaining and enabling connectivity by providing stepping stones of suitable habitat through inhospitable ecosystems; (5) providing increased protection for critical habitat within Category V protected landscapes and seascapes to boost their overall conservation potential; (6) taking advantage of conservation opportunities at cultural sites, sacred natural sites, and other faith-based sites in transformed landscapes; (7) integrating different management approaches and governance types in a range of connected small reserves to multiply conservation impacts. We propose a typology based on these benefits that can guide steps for policy makers to help plan and monitor small reserves in area-based conservation efforts. Using these principles, the role of small reserves in area-based conservation efforts can be further enhanced. [ABSTRACT FROM AUTHOR]

Spawning migrations of fishes are common case studies for examining the magnitude of resource subsidies; however, no studies have evaluated this phenomenon in iteroparous migrations of the Catostomid (i.e. suckers) genus Moxostoma (i.e. redhorses). Fish resource subsidies are usually represented as nitrogen (N) and phosphorus (P), and migratory redhorses can deliver these nutrients via excretion and eggs. We evaluated whether redhorses deliver N and P subsidies to Brasstown Creek—a fourth‐order stream in the Southeastern US—during their spawning migrations. We measured individual‐level nutrient contributions from excretion and eggs and extrapolated those values to estimate nutrient contributions based on daily abundances of migratory redhorses. We compared daily nutrient inputs to daily nutrient exports to determine the potential for resource subsidies. We estimated 71.6 kg of N and 4.4 kg of P were delivered to Brasstown Creek over a 98‐day migration period. N input exceeded N export on 15 of the 98 days, but phosphorus input never exceeded P export. Eggs accounted for the majority of N and P input at 51% and 100% respectively. Redhorse N inputs peaked in the spring during a period of low N exports, suggesting that redhorse subsidies were delivered during times of elevated nutrient demand and relatively low nutrient availability. Suckers receive little management attention, and several species of redhorses are imperilled. Given our conclusion that redhorses provide a temporally critical N subsidy that is likely available to multiple consumers in freshwater food webs, this study provides compelling motivation for increased conservation of these species and their migrations. [ABSTRACT FROM AUTHOR]

This study aims to provide a thorough ecological understanding of fin fish diversity within carp spawning grounds in the Surma River and Tanguar haor. Over two spawning seasons, this research investigates ecological factors impacting fin fish diversity and abundance in carp spawning grounds of the Surma River and Tanguar haor, emphasizing water quality, habitat features, spawn availability, and environmental influences. Fish spawn samples were collected with eight "Savar nets" at chosen sites and reared in a fiberglass tank at the mini hatchery for species identification. The representative spawn samples were examined under a microscope for preliminary species identification before rearing. The study found that both the Surma River and Tanguar haor offer ideal conditions for carp spawning due to factors such as water quality, natural food availability, habitat suitability, and favorable climatic conditions. The study identified 39 fish species under the 10 fish groups from both locations, with a higher percentage of carp species (31.42%) in the Surma River in 2021 compared to 2022 (22.50%). In Tanguar haor, the percentage of carp species was 7.55% and 6.50% in 2021 and 2022, respectively. The Surma River's ecological indices (2021-2022) indicated decreased diversity, likely due to environmental degradation, while Tanguar haor showed lower diversity possibly attributable to multiple environmental stressors. The dominant carp species, Labeo calbasu, Labeo bata, and Labeo gonius, were identified in both the Surma River and Tanguar haor. The spawning distribution varied among different locations, with some sites showing a presence of carp species, such as Hajipur T 1 in the Surma River and Alam Duar T 2 in Tanguar haor. The findings highlight the importance of hydrological and environmental parameters in shaping carp spawning habitat distribution and abundance, contributing to aquatic biodiversity conservation and resource management. [ABSTRACT FROM AUTHOR]

Flowers blooming, fungi fruiting, insects biting, fish spawning, geese migrating, deer calving; our consciousness is steeped in a seasonal calendar of nature's events. Phenology is the study of these recurring, seasonal life-history events, though nowadays this term is widely applied to the events themselves. From Shakespeare's sonnet 98, " From you I have been absent in the spring ", to the appearance of seasonal events and migratory species in the oral traditions of Native Americans, interest in phenology is long-standing and transcends cultures. In this primer we introduce the study of phenology, trace the development of the field, and examine the prominent role phenology has played in evidencing the widespread impacts of anthropogenic climate change on life on Earth. We will consider the potential implications of climatic change for the ability of populations to persist and the stability of species interactions. Phenology, the timing of an organism's recurrent life history events, determines the abiotic conditions and biotic interactions with which it is presented. In this primer, Macphie and Phillimore provide an overview of the science of phenology and discuss the implications of these important timing mechanisms for the ability of populations to persist in the face of climate change. [ABSTRACT FROM AUTHOR]

Prey species often congregate in groups to detect and evade predators, yet not all group members benefit equally. We observed the nesting aggregations of bluehead chub (Nocomis leptocephalus), where one nest "hosts" as many as several hundred "nest associates." We predicted that the male chub exploits the aggregation in a manner consistent with selfish‐herd theory – specifically, by locating itself in the safest location within the aggregation (the centre) and using the aggregation to reduce its own vigilance requirements.Vigilance was measured as the time it took the host (male) chub, first chub female and first individual of each associate species to return to the nest under differing associate abundances (hypothesised to be inversely related to risk) following a simulated predator scare. Spatial position was investigated by digitising host movement and overlaying it with the aggregation and nest's spawning pit area.We used information theoretic statistics to analyse the effect of aggregation characteristics on the return time of chub and their nest associates. The best‐supported model included both species composition and abundance (inverse of risk) as predictors of return time. Hosts returned last under nearly all scenarios and the aggregation as a whole took longest to return in high‐risk environments. The 95% and 99% confidence ellipses of host spatial position contained the centroids of the aggregation and spawning pits, respectively, for all nests analysed (n = 11).We conclude that the host locates itself at the centre of both the aggregation and the spawning pit area of the nest, and that the host uses the aggregation to reduce its own vigilance requirements. These results support our hypothesis that hosts use their nest associates to disproportionately decrease their risk of predation during spawning.This is the first study to show any mixed‐species fish spawning aggregation as a selfish shoal, and to identify bluehead chub as a selfish participant in the mutualistic reproductive interactions that they host. [ABSTRACT FROM AUTHOR]

Malleability allows computing facilities to adapt their workloads through resource management systems to maximize the throughput of the facility and the efficiency of the executed jobs. This technique is based on reconfiguring a job to a different resource amount during execution and then continuing with it. One of the stages of malleability is the dynamic spawning of processes in execution time, where different decisions in this stage will affect how the next stage of data redistribution is performed, which is the most time-consuming stage. This paper describes different methods and strategies, defining eight different alternatives to spawn processes dynamically and indicates which one should be used depending on whether a strong or weak scaling application is being used. In addition, it is described for both types of applications which strategies benefit most the application performance or the system productivity. The results show that reducing the number of spawning processes by reusing the older ones can reduce reconfiguration time compared to the classical method by up to 2.6 times for expanding and up to 36 times for shrinking. Furthermore, the asynchronous strategy requires analysing the impact of oversubscription on application performance. [ABSTRACT FROM AUTHOR]

The cassava (Manihot esculenta Crantz) breeding program at the International Institute of Tropical Agriculture (IITA) has adopted genomic selection to accelerate genetic gain. The program continues to develop varieties broadly adapted across Nigeria's diverse agroclimatic zones. However, for this purpose, genotype‐by‐environment interaction (GEI) presents a challenge. To decide whether broad adaptation breeding is a good strategy, we evaluated broad versus narrow adaptation strategies using stochastic simulation, assessing genetic gain, genetic variance, heritability, and selection accuracy at 0 versus realistic levels of GEI variance. To parameterize the models, we analyzed historical data from four phenotypic evaluation stages of the IITA breeding program to estimate genetic and error variances, and genetic correlations across environments. Based on these observed parameters, the genomic‐enabled breeding programs exhibited higher genetic gain than the conventional program for both GEI variances. At realistic GEI variance, the narrow adaptation program showed higher genetic gain than the broad adaptation program. Across all programs, the genetic variance declined over time, though the genomic‐enabled programs showed higher initial variance due to the selection of parents at earlier stages. At realistic GEI variance, an increase in genetic variance was observed in the narrow adaptation program due to its conversion of GEI between mega‐environments into main genetic variance within mega‐environments. This higher genetic variance led to higher heritabilities and selection accuracies. This study highlights the potential of genomic selection in accelerating genetic gain and suggests that dividing the IITA cassava breeding program to target more than one mega‐environment should be considered. Core Ideas: Simulation is a cost‐effective approach to assess different breeding strategies toward making informed decisions.Genomic selection outperformed a conventional breeding program in terms of rates of genetic gain, irrespective of genotype‐by‐environment interaction variance.Breeding for narrow adaptation by splitting Nigerian locations into two mega‐environments outperformed breeding for broad adaptation.Not all biological complexities of genetic effects and real‐world breeding programs can be captured in simulation. [ABSTRACT FROM AUTHOR]

Insight into fish annual reproductive dynamics (including spawn timing) can elucidate key determinants of recruitment. However, few methods, if any, are available to directly index individual spawn timing, hindering study of such processes. To this end, we developed two reproductive tags (RTs; internal and external) and evaluated their performance assessing spawn timing of female yellow perch (Perca flavescens). Internal RTs performed well, especially in comparison to external RTs, displaying consistent long-term tag retention and clear tag release synchronized with egg mass release during spawning. These results demonstrate the utility of internal RTs to investigate previously unexplored mechanisms of reproductive timing. [ABSTRACT FROM AUTHOR]

This article provides an overview of the spawning and larval development of Colossendeis megalonyx, a large sea spider found in Antarctica. The researchers observed the unique reproductive behavior of this species, where male parents care for the offspring. They collected eggs and observed the slow development of embryos, leading to the hatching of larvae. The study also suggests that the larvae of C. megalonyx have limited potential for long-distance dispersal and that the family Colossendeidae as a whole are nonbrooders. The researchers highlight the importance of field and laboratory observations for understanding the biology and natural history of sea spiders. [Extracted from the article]

This article provides a detailed analysis of gonadal neoplasia in Chinese gold barbs kept in home aquariums. The study examines the clinical, pathologic, and immunohistochemical characteristics of multiple gonadal neoplasms found in male and female gold barbs. The neoplasms identified include seminomas in males and fibrosarcoma in a female, as well as various other types of tumors in both sexes. The article also discusses the potential genetic and environmental factors that may contribute to the development of these neoplasms. This research emphasizes the need for further investigation into fish pathology and aquatic animal health in relation to neoplastic diseases. [Extracted from the article]

The present study investigated the reproductive biology of European anchovies obtained seasonally from fishermen in İzmir Bay (Aegean Sea). The total length range of the investigated individuals was 9.0 – 15.7 cm. Of the 750 samples in which sex was determined, 34% were males, and 66% were females, resulting in a female-to-male ratio of 1.91:1. The first maturation length was determined to be 10.47 cm for females and 9.95 cm for males. Based on the total values of the gonadosomatic index, it was concluded that the reproductive period of the species falls in the summer season. The batch fecundity of the species ranged from 2.123 to 6.951 oocytes, and the fecundity–length relationship was expressed as F = 1134.4TL – 10034 (R2 = 0.84). Histological examination of the female ovaries revealed the presence of oocytes at different stages of development, indicating multiple spawning during the reproductive season. [ABSTRACT FROM AUTHOR]

By the 1980s, after decades of declining numbers in the mid‐1900s, Coho salmon (Oncorhynchus kisutch) were considered extirpated from the interior Columbia River. In the mid‐1990s, the Confederated Tribes of the Umatilla Indian Reservation, the Confederated Tribes and Bands of the Yakama Nation, and the Nez Perce Tribe began successful reintroduction programs of Coho salmon upstream of Bonneville Dam, but which were initially sourced from lower Columbia River hatcheries. Here we present the first Coho salmon parentage‐based tagging (PBT) baseline from seven hatchery programs located in the interior Columbia River basin, and two sites at or downstream of Bonneville Dam, composed of over 32,000 broodstock samples. Analyses of baseline collections revealed that genetic structure followed a temporal pattern based on 3‐year broodlines rather than geographic location or stocking history. Across hatchery programs, similar levels of genetic diversity was present. The PBT baseline provided multiple direct applications such as identification of origin for Coho salmon collected in a mixed stock at Priest Rapids Dam and the detection of the proportion and distribution of hatchery‐origin fish on the spawning grounds in the Methow River basin. The PBT baseline for Coho salmon is freely available for use and can be downloaded from FishGen.net. [ABSTRACT FROM AUTHOR]

Age‐at‐maturity and iteroparity are two life history variations of steelhead trout (Oncorhynchus mykiss) that are believed to increase population resilience and stability. While repeat‐spawning individuals are thought to have historically made up a substantial portion of the reproductive population in the Columbia River and the majority of females still attempt outmigration as kelts, return rates of repeat‐spawner are low throughout the basin and below 1% for the furthest migrating stocks. Notably, outmigrating adults exhibit variation in rematuration phenology, displaying either "consecutive" (reproduce immediately the following season) or "skip" (delay spawning for future seasons) spawning patterns. Here, we use low coverage whole genome sequencing of consecutive versus skip spawning female Columbia River steelhead from two populations to test for genomic differences between these two iteroparous phenotypes. We identified genomic regions on several chromosomes which were associated with the phenology of iteroparity, including a region on chromosome 25 containing two genes, estradiol receptor beta (ERβ) and glycoprotein hormone beta‐5 (GPHB5), which, in mammals, are estrogen‐sensitive and expressed in reproductive tissues. Allele frequencies in this ERβ/GPHB5 region differed among female steelhead of different age at maturity, but not males. These genes also shared an island of linkage disequilibrium with the SIX6 gene, 600Kbp away on the same chromosome, a region of known association with age‐at‐maturity. These observations contribute to growing evidence that age‐at‐maturity and the phenology of iteroparity are determined by overlapping physiological processes and genetic pathways. [ABSTRACT FROM AUTHOR]

In the artificial breeding of Pampus argenteus (Euphrasen, 1788), female fish spawn before male release sperm, which indicates rapid ovarian development. In fish, aromatase is responsible for converting androgens into estrogens and estrogen plays a crucial role in ovarian development. In this study, we aimed to investigate the potential role of brain-type and ovarian-type aromatase to study the rapid ovarian development mechanism. The results showed that cyp19a1a was mainly expressed in the ovary and could be classified as the ovarian type, whereas cyp19a1b could be considered as the brain type for its expression was mainly in the brain. During ovarian development, the expression of cyp19a1a in the ovary significantly increased from stage IV to stage V and Cyp19a1a signals were present in the follicle cells, while cyp19a1b expression in the pituitary gland decreased from stage IV to stage V. To further investigate the function of Cyp19a1a, recombinant Cyp19a1a (rCyp19a1a) was produced and specific anti-Cyp19a1a antiserum was obtained. The expressions of cyp19a1a, estrogen receptors 2 alpha (esr2a), and androgen receptor alpha (arα) were significantly upregulated in the presence of rCyp19a1a. Meanwhile, cyp19a1a was expressed significantly after E2 treatment in both ovarian and testicular tissue culture. Taken together, we found two forms of aromatase in silver pomfret. The ovarian-type aromatase might play an important role in ovarian differentiation and maturation, and participate in E2 synthesis through co-regulation with esr2a. The brain-type aromatase cyp19a1b might be involved in the regulation of both brain and gonadal development. [ABSTRACT FROM AUTHOR]

Inflammatory responses are modulated by sex steroids, and hence, not surprisingly, in seasonally breeding organisms, the immune responses are reported to vary according to the reproductive phases. NOD-like receptors (NLRs) act as intracellular sentinels and play a key role in inflammation. Interestingly, to date, there are no reports on their reproductive season-dependent expression and their regulation by sex steroids in teleosts. In the current study, the expression of NOD-like receptors (NLRs) in primary and secondary lymphoid tissues in female Channa punctata during different reproductive phases has been investigated. It was observed that NLRs show a dramatic increase in expression during the spawning phase of Channa punctata. Since estradiol is the primary sex steroid in females that shows the highest plasma level during the reproductively active phase, we investigated whether estradiol was responsible for the increased transcription of NLRs. The effect of estradiol on NLR expression in female Channa punctata was diverse, depending upon the lymphoidic tissue, dose, duration, and mode of estradiol treatment. However, the increased expression of NLRs in the spawning phase could not be attributed to estradiol alone as evident from the study. Other factors acting alone or collaborating with estrogen might be involved in the increased NLR expression during spawning phase in Channa punctata. [ABSTRACT FROM AUTHOR]

Context: The Carnaby's Black–Cockatoo Calyptorhynchus latirostris , an endangered species endemic to south-west Western Australia, has experienced a 30% contraction in range and 50% decline in population since the 1940s. A breeding population of Carnaby's Black–Cockatoo was first described at Murchison House Station in the 1970s, but breeding had not been recorded there since the 1990s. Aims: We sought to confirm whether Carnaby's Black–Cockatoos were still breeding at this location at the far-northern edge of their range, hundreds of kilometres from the nearest known breeding site. Once confirmed, we compared population, hollow and nestling characteristics with those of other well-studied breeding populations of the same species and surveyed foraging and nesting habitat to evaluate population health and inform management. Methods: We monitored 30 breeding attempts and characterised 21 confirmed hollows. We conducted comprehensive vegetation community surveys at nine sites. Key results: We confirm that Carnaby's Black–Cockatoos are still breeding at the far-northern edge of their range. Hollow and nestling characteristics are similar to breeding populations elsewhere. We found no evidence of plant recruitment for crucial foraging or nesting species. Conclusions: The absence of plant recruitment in both foraging and nesting habitats suggests that active management will be required to support ongoing breeding. We recommend conserving and revegetating foraging and breeding habitat, maintaining hollows and/or providing artificial hollows while trees regenerate. Implications: Foraging and breeding habitat will need long-term management to support ongoing breeding of this threatened species at the northern edge of its range. Carnaby's Black–Cockatoos have experienced significant range contraction and population decline. We studied an isolated population breeding at the edge of the species range, hundreds of kilometres north of the next-nearest known breeding location. We recommend direct management actions to support continued breeding at the site. [ABSTRACT FROM AUTHOR]

The age, growth, reproduction and resource development status of Ptychidio jordani, as a critically endangered freshwater fish in the Hongshui River, China, was studied in this work. A total of 525 specimens were collected monthly using the cages and gillnets from October 2021 to September 2022 in the Hongshui River. The scale was used for age determination, and the maximum age for both female and male was estimated to be 5 years and 3 years, respectively. Female and male P. jordani showed different growth patterns, which were expressed as Lt = 261.3 (1‐e−0.4885(t−0.1476)) and Lt = 251.2 (1‐e−0.4758(t+0.9643)), respectively. The overall sex ratio was 1:0.47 (female:male). Female attained sex maturity at 2.34 years (192 mm body length). Month variation of the gonad somatic index indicated that the spawning period occurred from April to October. The absolute fecundity was estimated at 9046 ± 3434 eggs per individual, and the relative fecundity was 38.08 ± 15.77 eggs per gram. The exploitation rate of female and male was 0.233 and 0.495, which indicated that P. jordani was not overfishing. This study provided data on the key life‐history traits of P. jordani, which has not been known previously and is essential for conservation strategy and policy development. [ABSTRACT FROM AUTHOR]

Prespawn mortality (PSM) presents a major problem for the recovery of spring Chinook Salmon (Oncorhynchus tshawytscha) populations. In the Willamette River, Oregon, PSM exceeds 90% in some years but factors explaining it are not well understood. We examined intestinal tissue samples using histological slides from over 783 spring Chinook Salmon collected between 2009 and 2021, which included tissues from PSM fish, artificially spawned captive broodstock (BS) and normal river run fish, comprised of trapped (Live) and naturally post‐spawned river (RPS) fish collected from the river. We observed degeneration of the intestinal epithelium and loss of villous structure, with concurrent severe enteritis. A natural progression of decline in epithelial integrity (EI) through the summer and fall until spawning and subsequent death was also observed. Live fish exhibited high EI scores (mean = 68%), BS exhibited variable EI scores (35%) and RPS exhibited severe loss of EI (14%). PSM fish exhibited prominent loss of intestinal epithelium with EI scores (13%), very similar to RPS fish, despite having been collected earlier in the year. Hence, we argue that low EI scores are strongly linked with PSM. Ceratonova shasta and Enterocytozoon schreckii were common in all groups, but neither were linked to either PSM or a decline in EI. [ABSTRACT FROM AUTHOR]

The placement of wood in rivers is a common restoration method used to locally affect hydraulic and morphologic conditions to create habitat. Laboratory experiments demonstrated that wood placements can also promote surface declogging, that is, removal of fine sediment from a gravel bed, thereby restoring spawning grounds for fish. Logs of different size and submergence level were placed on a gravel bed clogged with fines. Surface declogging was observed in regions of elevated turbulence in the log wake and elevated velocity adjacent to the log. A criteria for declogging was identified based on a modified non‐dimensional Shields parameter combining mean and turbulent velocity at the bed. The footprint of declogged bed scaled with log dimensions. Emergent logs produced a larger declogging footprint compared to submerged logs of the same length, due to their stronger influence on the flow field. Logs were also shown to prevent clogging over similar areas. Plain Language Summary: Placing wood in rivers is a common way of improving river health and creating regions for fish and small aquatic animals to live. This method involves the placement of individual wood pieces (logs) at the side or in the center of a river. In this study, we explored how the positioning of logs could be used to remove fine sediments from gravel beds by changing the way water flows. This is important because excessive deposition of fine sediments in the bed, defined as riverbed clogging, can make the channel bed too compact. This makes it harder for fish to find good spots to lay their eggs. Using laboratory experiments, we observed that the logs generated regions with strong water turbulence (swirling) and faster flowing water in their surroundings, both of which removed fines from the gravel bed surface. We identified specific conditions necessary for effective removal of fines, which were related to both the turbulence and water velocity. The size of the cleaned area on the gravel bed was proportional to the size of the log. Key Points: Deliberate wood placement can promote declogging adjacent to and downstream of logsDeclogging was correlated with elevated turbulence downstream of logs and elevated velocity adjacent to logsEmergent logs declogged a greater surface area than submerged logs [ABSTRACT FROM AUTHOR]

Simple Summary: Galaxias maculatus plays an important ecological and socioeconomic role in Chile. We determine the sex ratio, sexual maturity stages, gonadosomatic index, spawning period, type and frequency of spawning, and fecundity under experimental culture. The sex ratio was close to 1:1. First sexual maturity was reached at one year of age in 50% of the population. The highest GSI in both females and males was found in August. Nevertheless, females have a long spawning period, divided into two subperiods; the highest reproductive peak occurs between September and October, and the minor peak occurs between December and February. The females spawned between 3 and 10 times over a period of two months. The number of embryos per female per day varied from 1 to 429, while the total number of embryos per female during the entire season varied from 163 to 1044. This knowledge will be useful to establish future reproductive programs in captivity as a strategy for sustainable fishery and aquaculture management. This study determines the reproductive patterns of puye (Galaxias maculatus) under culture conditions. A population of 567 wild fish was caught in the Cautín River, Chile, and held in captivity for four years. Mortality, sex ratio, gonadosomatic index (GSI), sexual maturity stages, spawning period, type and frequency of spawning, and fecundity were measured. The fish grew throughout the experimental period, with the fastest rate during the first half of the first year of life. The highest mortality occurred during the first three months of the experiment and during the spawning season. The sex ratio was almost 1:1 (female:male). First sexual maturity was reached at one year of age, with an average weight of 0.85 ± 0.01 g, total length of 4.85 ± 0.16 cm, and condition factor 0.0074. The highest GSI in both females (12.14 ± 0.74) and males (17.7 ± 2.70) was recorded in August. Nevertheless, the females spawned 3 to 10 times between September and February, with the highest reproductive peak between September and October. The number of embryos per female per day varied from 1 to 429, while the total number of embryos per female during the entire season evaluated varied from 163 to 1044. There was a high correlation (r = 0.82) between absolute fecundity and body weight. Although further studies are needed in this field, these results are basic for establishing future reproductive programs in captivity as a strategy for sustainable fisheries and aquaculture management. [ABSTRACT FROM AUTHOR]

Fish is an important resource in Malawi as a source of food for the majority as it provides affordable source of dietary animal protein as well as income. A number of fish species in the Malawi water bodies have their population dwindling. One of the species under serious threat of extinction is the Opsaridium microlepis - a potamodromous fish species that migrate to the rivers during its spawning period and its management seems a nightmare. A number of studies reveal contrasting results on genetic makeup and morphological aspect of this fish species. With changes in the ecosystems of the rivers connecting Lake Malawi, coupled with absence of strong management measures in the major rivers adjoining the lake, problems have arisen in the conservation of potamodromous fish species. This necessitated the present study to investigate if the morphological features of stocks of O. microlepis are the same or not and if they have changed to adapt to changes in the ecosystems. One hundred and eleven O. microlepis fish samples were collected from Linthipe River (48), Bua River (59) and North Rumphi River (4) monthly from March to August 2020 using trawled and static gillnets. Twenty-four morphometric characteristics were measured to determine if any morphological differences existed among the fish samples from the three rivers. Principal component analysis (PCA) was used to compare morphology of the fish. Results of the study showed no significant morphological differences among stocks from the three rivers, implying that O. microlepis in these rivers belong to same stock morphologically. The study reveals that the species do not differ morphologically even though they migrate to different rivers for breeding. The study further notes that numerous activities taking place along the tributary rivers (as observed during the study) such as modification of fishing gears as well as fishing methods and the deterioration of the spawning grounds due to siltation from soil erosion caused by deforestation and agriculture, are putting the potamodromous fish species such as O. microlepis under serious threat. The study recommends that the populations of O. microlepis from the rivers can be managed equally since they are morphologically similar. Adopting uniform catchment management and sustainable exploitation of O. microlepis (such as regulations on mesh sizes and fishing methods, closing the rivers from fishing activities during spawning period, river bank and catchment management and restoration) with the aim of conserving the stocks from further overexploitation in these rivers is recommended so that the communities and the people at large continue to utilize the resource sustainably and at the same time, sustaining their livelihood. [ABSTRACT FROM AUTHOR]

Understanding the molecular mechanisms underlying individual responses to environmental changes is crucial for species conservation and management. Pelagic fishes including Atlantic herring (Clupea harengus) are of particular interest because of their key ecological and economic roles and their susceptibility to a changing ocean from global warming. Temperature and photoperiod have been linked with spawning time and location in adult herring, but no study has thus far investigated the role of environmental factors on gene regulation during the vulnerable early developmental stages. Here, we examine DNA methylation patterns of larval herring bred under two temperatures (11°C and 13°C) and photoperiod (6 and 12 h) regimes in a 2 × 2 factorial design. We found consistently high levels of global methylation across all individuals and a decline in global methylation with increased developmental stage that was more pronounced at 13°C (p ≤ 0.007) than at 11°C (p ≥ 0.21). Most of the differentially methylated sites were in exon and promoter regions for genes linked to metabolism and development, some of which were hypermethylated at higher temperature. These results demonstrate the important role of DNA methylation during larval development and suggest that this molecular mechanism might be key in regulating early‐stage responses to environmental stressors in Atlantic herring. [ABSTRACT FROM AUTHOR]

Worldwide biodiversity is on the brink of extinction following the complete disappearance of many forest and freshwater vertebrates. This disappearance is closely linked to the reduction and disturbance of habitats, which should instead benefit from special conservation. In the case of lake ecosystems, fish spawning grounds remain the most vulnerable. This study aims to identify, characterise and locate fish spawning and nursery sites in Lake Kivu for better conservation. Sixteen sampling sites were selected along the shoreline of the Bukavu sub-basin. Physico-chemical parameters were measured in situ, and fish were captured using multi-mesh nets, identified and dissected, gonads observed and sexual maturity stages determined. Twenty-five fish species were identified, but 17 of these use the selected sampling sites as spawning and/or nursery. Eleven spawning and nine nursery sites were identified and located. Physico-chemical analyses showed that temperature (F=2.124, p = 0.011), dissolved oxygen (F=2.792, p<0.001), depth (F=5.915, p<0.001) and transparency (F=3.421, p = 0.004) were significantly different, which characterise each site and may be key factors in species distribution between spawning sites. Fish size-weight relationships indicate allometric growths. The results of this research contribute to empirical knowledge of fish spawning grounds. [ABSTRACT FROM AUTHOR]

Introduction: Righting behaviour has been used as a health indicator in response to stressor variables. Using this parameter in aquaculture could help to reduce mortality and improve welfare in the sea urchin Arbacia dufresnii culture. Objective: The purpose of this study was to determine the effect of sex, diameter, and three stressor factors on the righting behaviour of the sea urchin A. dufresnii. Methods: A total of 300 animals were evaluated for complete righting behaviour (CRB) time, with 100 of them also recording half righting behaviour (HRB) time. Three stressors were applied to the animals: serial repetitions (three successive turnings), temperature (24-hour shock), and spawning induction with KCl injection. A stopwatch was used to record the time, and a precision calliper was used to measure the diameter. Results: Righting time was discovered to be diameter dependent but sex independent. The upper temperature limit of 19 °C had a significant effect on righting behaviour compared to 16 °C and 13 °C with CRB times up to 150 seconds. Serial repetitions and spawning had no significant effect. However, based on the recorded times, it can be deduced that spawning had an effect on the health of the animals, with CRB times of up to 150 seconds compared to the control, with lower times. Conclusions: Complete righting behaviour appears to be an optimal indicator for evaluating the health and condition of the sea urchin A. dufresnii, but more tests would be performed to confirm the effect of the control treatment on post-spawning stress. [ABSTRACT FROM AUTHOR]

Anti‐Müllerian hormone (AMH) is secreted by granulosa cells of healthy, growing follicles and is positively correlated with the ovarian reserve. Maternal and environmental factors, such as nutrition, disease, parity and endocrine disruptors, are thought to have a profound impact on ovarian reserve development during early foetal life. For genetic progress, it can be advantageous to breed dairy replacements from heifers to expedite the generation interval; however, there is some evidence that nulliparous animals produce female offspring with smaller ovarian reserves compared with multiparous animals. The objective of this prospective, observational study was to determine whether maternal growth in the pre‐conception and early gestational period of nulliparous dairy heifers is associated with pre‐weaning AMH concentrations in their female offspring. Our hypothesis was that excessive growth in this period would negatively impact AMH concentrations. Seasonal, pasture‐based dairy heifer calves (n = 156) born from nulliparous dams, from six Irish farms, were blood sampled at an average of 60 days of age in spring 2022 and tested for AMH. Mixed‐effects linear regression models were constructed with Box‐Cox transformed AMH concentration as the dependent variable. The independent variables tested included maternal average daily gain (ADG) from pre‐breeding examination (PBE) to pregnancy diagnosis (PD) between 30 and 60 days in calf (DIC), ADG from PBE to PD over 60 DIC and ADG between the two PDs. Calf breed and age at sampling were forced into the models, and the farm was treated as a random effect in all models. We found that as ADG increased from the pre‐breeding period to their first PD visit, the AMH concentration in their offspring reduced. However, ADG explained only a small amount of the variation in AMH concentrations (marginal R2 = 0.041). In conclusion, the results of our study suggest that excessive growth prior to conception and in early gestation of nulliparous heifers could impact the ovarian reserve of their female offspring, and may imply that farmers should avoid excessive growth in the immediate pre‐breeding and early gestational periods. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms by which individual organisms respond and populations adapt to global climate change is a critical challenge. The role of plasticity and acclimation, within and across generations, may be essential given the pace of change. We investigated plasticity across generations and life stages in response to ocean acidification (OA), which poses a growing threat to both wild populations and the sustainable aquaculture of shellfish. Most studies of OA on shellfish focus on acute effects, and less is known regarding the longer term carryover effects that may manifest within or across generations. We assessed these longer term effects in red abalone (Haliotis rufescens) using a multi‐generational split‐brood experiment. We spawned adults raised in ambient conditions to create offspring that we then exposed to high pCO2 (1180 μatm; simulating OA) or low pCO2 (450 μatm; control or ambient conditions) during the first 3 months of life. We then allowed these animals to reach maturity in ambient common garden conditions for 4 years before returning the adults into high or low pCO2 treatments for 11 months and measuring growth and reproductive potential. Early‐life exposure to OA in the F1 generation decreased adult growth rate even after 5 years especially when abalone were re‐exposed to OA as adults. Adult but not early‐life exposure to OA negatively impacted fecundity. We then exposed the F2 offspring to high or low pCO2 treatments for the first 3 months of life in a fully factorial, split‐brood design. We found negative transgenerational effects of parental OA exposure on survival and growth of F2 offspring, in addition to significant direct effects of OA on F2 survival. These results show that the negative impacts of OA can last within and across generations, but that buffering against OA conditions at critical life‐history windows can mitigate these effects. [ABSTRACT FROM AUTHOR]

Periodic monitoring can provide important information for the protection of endangered fish, sustainable use of fishery resources and management of alien species. Previous studies have attempted to monitor fish using non‐invasive environmental DNA (eDNA) technology, generally employing quantitative PCR to quantify the eDNA concentration. However, the throughput was limited. High‐throughput metabarcoding technology can detect the DNA of multiple species simultaneously in a single experiment but does not provide sufficient quantification. In this study, we applied a quantitative metabarcoding approach to simultaneously quantify the eDNA concentration of an entire fish assemblage in a small reservoir over two summer seasons. Traditional surveys were also conducted to investigate the individuals of fish. The eDNA concentrations were quantified using quantitative metabarcoding, and the fish species detected using this approach were highly consistent with the results of traditional fish monitoring. A significant positive relationship was observed between the eDNA concentration and fish species abundance. Seasonal changes in fish community structure were estimated using eDNA concentrations, which may reveal the activity seasons of different fish. The eDNA concentrations of different fish species peaked at different water temperatures, reflecting the differential responses of fish species to this environmental factor. Finally, by detecting outlier eDNA concentrations, the spawning activities of 13 fish species were estimated, 12 of which were roughly consistent with the current knowledge of fish spawning periods. These results indicate that quantitative eDNA metabarcoding with dozens of sampling times is useful for the simultaneous ecological monitoring of multiple fish species. [ABSTRACT FROM AUTHOR]

Obtaining viable Argopecten purpuratus seeds faces challenges, especiallyci the unpredictability of the marine environment and high production costs in hatcheries. However, improving the method of "Broodstock Conditioning In Hatcheries" is key to ensure permanent seed supplies by minimizing the dependence on marine conditions and by maximizing economic viability in hatcheries. In an effort to overcome these barriers, broodstock were conditioned into two different environments: (a) Natural Environment: Natural marine conditions located in Bahía Inglesa, Atacama Region, Chile. (b) Hatchery: Laboratory conditions to achieve gonadal maturation, spawning induction, fertilization and larval development. The purpose of this research was to evaluate how the type of reproductive conditioning affects the reproductive potential and nutritional quality of the progeny. Both methods were successful at inducing the necessary maturity for reproduction, obtaining viable gametes and larvae. On the other hand, it was observed that in the natural environment, the oocytes and D larvae reached a greater size and nutritional value, being the most significant differences with (p < 0.05): the size of the D larvae reached figures of 95.8 ± 3.1 μ m and 91.2 ± 2.7 μ m in the environment and hatchery, respectively; the lipid content in dry mass was 25.2 ± 3.1 mg g − 1 and 13.5 ± 1.9 mg g − 1 for the natural environment and hatchery, respectively. Although quality indicators in hatcheries were slightly lower compared to the natural environment, the possibility of conditioning A. purpuratus broodstock independently of environmental variability highlights the importance of further optimizing broodstock conditioning aspects in hatcheries that would allow more predictable and sustainable production. [ABSTRACT FROM AUTHOR]

The Gorgeous goby Lythrypnus pulchellus shows extreme sexual plasticity with the bidirectional sex‐change ability socially controlled in adults. Therefore, this study describes how the hierarchical status affects hormone synthesis through newborn hormone waste products in water and tests the influence of body size and social dominance establishment in sex reversal duration and direction. The associated changes in behavior and hormone levels are described under laboratory conditions in male–male and female–female pairs of similar and different body sizes, recording the changes until spawning. The status establishment occurred in a relatively shorter time period in male and female pairs of different sizes (1–3 days) compared to those of similar size (3–5 days), but the earlier one did not significantly affect the overall time of sex change (verified by pair spawning). The changes in gonads, hormones, and papilla occurred in sex‐changer individuals, but the first one was observed in behavior. Courtship started at 3–5 days in male pairs and from 2 h to 1 day in female pairs of both groups of different and similar sizes. Hormones did not gradually move in the new sexual phenotype direction during the sex‐change time course. Nonetheless, estradiol regulated sex change and 11‐ketotestosterone enabled bidirectional sex change and was modulated by agonistic interactions. Cortisol is associated with status and gonadal sex change. In general, similar mechanisms underlie sex change in both directions with a temporal change sequence in phases. These results shed new light on sex‐change mechanisms. Further studies should be performed to determine whether these localized changes exist in the steroid hormone synthesis along the brain–pituitary gonad axis during social and bidirectional sex changes in L. pulchellus. [ABSTRACT FROM AUTHOR]

This study was the first to investigate the key reproductive traits of the electric lantern fish Electrona risso (Myctophidae, n = 918) and the bigscale fishes (Melamphaidae) Melamphaes polylepis (n = 260) and Scopelogadus mizolepis (n = 649). Specimens of these mesopelagic species were collected in March and April 2015 in the eastern Central Atlantic (0–24° N, 20–26° W). Sex ratio was not significantly different from 1:1 in E. risso and M. polylepis but significantly skewed toward female dominance in S. mizolepis. Reproductive phases were determined macroscopically and by histological analyses on selected individuals. Female length at 50% maturity (L50) was 55.1 mm standard length (LS) in E. risso, with an observed female maximum length (Lmax) of 81.2 mm LS. M. polylepis females had an L50 of 40.2 mm LS and an Lmax of 86.7 mm LS. S. mizolepis had an L50 of 46 mm LS and an Lmax of 97.9 mm LS. The three species show histological features of iteroparity, but the E. risso population appears to occur in two year‐classes and experience only one spawning season per lifetime in the study region. All three species are batch‐spawners. A batch fecundity of 2668 eggs was estimated from one E. risso individual, with a relative batch fecundity of 369 eggs g−1 gonad‐free body mass. M. polylepis had a batch fecundity of 1027 eggs and a relative batch fecundity of 149 eggs g−1 (n = 3). S. polylepis had a batch fecundity of 1545 eggs and a relative batch fecundity of 215 eggs g−1 (n = 21). The median gonado‐somatic index during the actively spawning phase of E. risso was 4.5, significantly lower than that of M. polylepis (7.5) and S. mizolepis (7.1). No regressing or regenerating phases were observed in this study. Batch‐spawning in all three species is suggested to be advantageous to cope with intra‐annual variability in food supply and other risks for offspring survival. With what appears to be in effect a (facultative) semelparous strategy in combination with a short life span in E. risso, interannual differences would have a great effect on population dynamics of this species. Knowledge is still lacking on temporal aspects of reproduction such as the duration of the spawning season and the frequency of spawning, as well as age and growth. [ABSTRACT FROM AUTHOR]

The results of the study of the morphometric parameters of eggs and prelarvae of the Alaska plaice Pleuronectes quadrituberculatus in the northern part of the Sea of Okhotsk are presented. Incubation of eggs of the species from natural spawning collected in June 2021 was carried out. The diameter of eggs of the Alaska plaice ranges from 1.60 to 1.93 mm (on average, 1.75 mm). The results of our research in the northern part of the Sea of Okhotsk briefly supplement the information available in the literature on the parameters of the eggs and the morphology of the prelarvae of the Alaska plaice. The total length (TL) of newly hatched prelarvae of P. quadrituberculatus is equal to 6.48 mm with fluctuations of 5.70–7.25 mm. The general morphology of embryos and prelarvae of the Alaska place coincide with the descriptions available in the literature. At the same time, in those described by us, along with the pigmentation of the body with black melanophores, yellow pigment cells develop. The prelarvae of the Alaska plaice of the area studied differ from their peers in other areas by their large size and differentiated digestive tract. This paper presents for the first time photos of embryos and prelarvae of P. quadrituberculatus in the living state. Analysis of the levels and stages of development of Alaska plaice eggs suggests that, in the northern part of the Sea of Okhotsk, mass spawning of the species occurs in April and early May. [ABSTRACT FROM AUTHOR]