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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]

This trial aimed to investigate whether dietary selenium form influenced the reproductive performance of red tilapia broodfish. Four experimental broodstock diets were prepared employing two types of selenium. The first diet was free of additives and acted as the control diet. While the other three formulated diets were supplemented with conventional selenium sources (sodium selenite, Na2SeO3; 1 mg/kg), selenium nanoparticles (NPSe, 1 mg/kg), or a combination of them (0.5 mg Na2SeO3/kg + 0.5 mg NPSe/kg), respectively. Twelve cement ponds (each 24 m2) were subjected to fish brooder experimental groups. Each pond received six prespawning females (mean initial weight, 60.9 ± 0.4 g) and two males (mean weight 80.3 ± 0.8 g) of red tilapia. Each formulated diet was supplied to three broodfish cement ponds, and the reproductive traits of 18 adult female fish were monitored over 25 weeks. The findings showed that female fish fed NPSe-enriched diets had significantly higher viscera, liver, and gonad weight than other experimental groups. At the same time, the highest levels of LH, progesterone, and estradiol-17β, as well as the lowest levels of FSH, were detected in fish fed the NPSe diet, followed by those on the Na2SeO3 + NPSe and Na2SeO3 diets, respectively. Furthermore, the diameter, weight, and volume of eggs, as well as the number and weight of larvae in red tilapia brooder fish fed the various dietary selenium forms, increased markedly (P < 0.001). Female red tilapia broodfish given selenium-based diets enhanced all spawning performance indicators (particularly total spawned egg per pond or fish and initial spawning interval) when compared to a control group fed an unsupplemented diet. Besides, as compared to other treatment groups, the spawning frequency of each female fish fed NPSe-supplemented diets (alone or in combination with Na2SeO3) was considerably (P < 0.001) promoted. The fish group fed NPSe alone or mixed with Na2SeO3 had a well-developed stroma structure, many mature vitellogenic and postvitellogenic oocytes, and a remarkable intensity of mature spermatozoa in the testis. In conclusion, incorporating NPse into red tilapia broodstock diets might be a safe and efficient way to enhance reproductive function and fry production. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) is an intensive sustainable farming technique that increases the carrying capacity of the culture system by controlling the C/N ratio. The present study aims to assess the potentiality of BFT for intensive nursery production of Labeo rohita spawn (6–8.5 mm). The assessment was done at different stocking densities, that is, 1 (D1), 2 (D2), 3 (D3), 4 (D4) and 5 (D5) spawn/L (study I) and at different C/N ratios, that is, 10:1, 15:1 and 20:1 (study II), by evaluating survival, growth, feed utilization and biochemical composition of spawn in biofloc culture system. The cultures reached at the end of 20 days showed a higher mean survival rate, that is, 89%, 91.38% and 80.4% in D1, D2 and D3 respectively. Moreover, these BFT groups exhibited spearheading growth in terms of final length, final weight and specific growth rate. The coefficient of variation and food conversion ratio was lowest in D2, but the highest production was achieved in D3. In study II, the biofloc culture (at 2 spawn/L density) with C/N ratio >15:1 effectively reduced the total ammoniacal and nitrite nitrogen and produced in situ live food adequately. In addition, the C/N ratio showed an interactive effect on the growth performance of fish by the substantial increase in final length, weight gain percentage, specific growth rate and feed utilization in C/N 20 and 15 groups than that in C/N 10 group. The crude protein and lipid level of biofloc in C/N 20 and 15 treatments was notably higher than in other treatments. The findings suggest that the BFT can be effectively applied to enhance the nursery production of L. rohita, preferably at 2–3 spawn/L stocking density and 15:1C/N ratio. [ABSTRACT FROM AUTHOR]

Cobitis faridpaki is a small endemic loach from the southern Caspian basin. Reproductive parameters are key components for enlightening the life history of an endemic species. The reproduction parameters of C. faridpaki including sex ratio, spawning season, fecundity, and oocyte diameters were studied in a tributary of Gorganroud River – northern Iran, the area where no information on the Cobitis spawning is available, from February to July 2018. A total of 403 specimens including 47.8% males and 52.2% females were collected using electrofishing. Even though the sex ratio was not significantly different from parity, a perceptible dominance of females in the pre‐spawning and spawning periods could be observed in the population. Based on the monthly variation in GSI, the spawning period is from late March to early May. The absolute fecundity of females ranged from 57 to 1287, with a mean of 404 (±250) oocytes per ovary, and relative fecundity was estimated to be 47–386, with a mean of 136 (±73) oocytes per gram of total weight. Absolute fecundity established statistically significant linear relationships with total length and weight. Oocyte diameters varied from 0.26 to 1.30 mm, being of multi‐modal distribution throughout the spawning period, which suggests that the species is a multispawner. The oocyte size correlated positively with the length, weight, and age of mature females. This study provides fundamental information to aid in future conservation programs that intend to reduce the ongoing depletion of habitats and populations of endemic species. [ABSTRACT FROM AUTHOR]

Broodstock development, induced maturation and breeding of the newly described seabream, Sparidentex jamalensis collected from Kali estuary, Karnataka, India were achieved successfully for the first time. Taxonomy of the fish was confirmed employing morphological and molecular tools. Majority of the brooders collected were in the 20–30 cm length class (140–510 g) and were ideal for developing matured broodstock. Periodic microscopic observation of ovarian biopsy indicated progressive gonadal development in the broodstock. The broodstock developed for this protandrous hermaphrodite consisted of females having maturing oocytes and males with oozing milt during the breeding season. Final maturation and spawning of the females (520 ± 8 g; ova diameter above 400 µm) was achieved using cholesterol‐based LHRH analogue pellets (50 µg/kg fish) and the males (450 ± 54 g) were not treated with hormones. Pelagic fertilized eggs (720 ± 8 µm) with a single oil globule were obtained with an absolute fecundity of 0.42 ± 0.06 million/kg fish and a fertilization rate of 82 ± 2.4%. Major embryological stages were recorded and the fertilized eggs hatched after 18–20 hours with 80 ± 4.6% hatching rate at 28°C. The newly hatched planktonic larvae measured 1.8 ± 0.12 mm in total length. Mouth opening of the larvae was observed on second day post hatch (dph). Resorption of the yolk sac was observed on third dph. These results will act as a baseline for developing a breeding programme for this species. [ABSTRACT FROM AUTHOR]

Summary: Evaluation of appropriate hormone and ideal broodstock age for optimal breeding efficiency may ensure the production of good quality eggs and larvae in the hatchery. In this study, the spawning response of captive silver therapon Leiopotherapon plumbeus to various hormonal treatments and broodstock age was examined. In Experiment 1, spawning success, latency period, absolute and relative fecundity, fertilization and hatching rates, and larval production of female silver therapon broodstock were determined after ovulation and spawning in response to human chorionic gonadotropin (hCG; 5000 and 10,000 IU/kg), Ovaprim (0.5 ml/kg), hCG + Ovaprim (5000 IU + 0.5 ml/kg; 10,000 IU + 0.5 ml/kg) or hCG + domperidone (5000 IU + 0.5 ml/kg; 10,000 IU + 0.5 ml/kg). In Experiment 2, reproductive performance of four domesticated broodstock age groups (1+, 2+, 3+ and 4+‐year old) was examined for five consecutive months, coinciding with the spawning season. Higher dose of hCG + Ovaprim resulted in higher spawning (100%), fertilization (99.7 ± 0.1%), and hatching (85.8 ± 5.5%) rates than the other treatments. The effect of age on reproductive indices was not significant. However, better spawning performance was observed in 1+ to 3+‐year old broodstock, with higher fertilization (96.8–98.5%) and hatching (63.7%–77.2%) rates than among the oldest age group (82.9% and 57.2%). Together, results suggest that the combination of hCG + Ovaprim is highly effective in inducing ovulation and spawning in silver therapon, and that domesticated broodstock up to 4+ years of age could still be used for breeding activities and seed production. [ABSTRACT FROM AUTHOR]

The ferruginous limpet is one of the most threatened invertebrate species in the Mediterranean Sea. Its controlled reproduction has been considered one of the potentially most effective strategies for the production of juveniles for population restocking or for recolonization of areas where the species was brought to extinction by human pressure but is now under protection (e.g., MPAs). This approach has been pursued for at least two decades but with partial results: at most, some juveniles have been obtained and have reached adult stage, yet not starting from spawning induction but through sacrifice of female specimens (lethal approach), additionally resulting in low genetic diversity of the juveniles produced. Herein, we describe, for the first time, positive results of the spawning induction in P. ferruginea. The fertilizations made after these experiences allow describing the larval development of the species from its early stages to its metamorphosis. The fertilization rate in these spawning events was much higher (>97%) than in previous studies that were based on the extraction of oocytes by dissection. The rate of non‐anomalous larvae after 15 hours was not negligible but variable, depending perhaps on the quality of the sperm available at each fertilization. The timing of larval development of the species and its variability, particularly regarding metamorphosis, are described. Settlement ability is reached at 3–4 days after fertilization, depending on water temperature, while a large variability is observed in metamorphosis, occurring between 7 and 32 days (probably up to 40 days), although inducing factors are still unknown. [ABSTRACT FROM AUTHOR]

Nutritional components and feeding strategies are multifarious amongst different producers, whereas they are just designed for fish farming but not suitable for improving the reproductive performance of broodfish. Yellow catfish (Pelteobagrus fulvidraco), an omnivorous species, is one of the important aquaculture fish in China. In order to improve the reproductive performance of female yellow catfish (119.86—134.54 g), four feeding strategies (0.5%, 0.75%, 1% and 1.5% BW/d) and three dietary protein levels (34%, 40% and 46%) were examined, respectively, in the two separate trials. The females with moderate feed restriction (1%) showed significant lower mesenteric fat index (MFI) and higher gonadosomatic index (GSI) than the satiation group (1.5%) and excessive feeding restriction groups (0.5% and 0.75%). Females with high MFI were difficult to be artificially propagated and showed a high mortality rate, whilst the fish at 1.0% feeding rate displayed low mortality rate and high ratios of spawned fish, as well as high percentages of fertilization and hatching. Meanwhile, the offspring of 1.0% feeding rate group showed a low malformation rate and high survival rate. Multiple spawning in the same breeding season are applied in yellow catfish to reduce the number of parent fish and increase the fry production, and gonadal recrudescence after spawning might be affected by different nutrient values including dietary protein levels. In the second trail, female yellow catfish were fed with 34%, 40% and 46% crude protein diet at 1% feeding rate for the second spawning, and the best reproductive and breeding performances were observed in the fish group with 46% crude protein diet. These results demonstrate that 1% feeding rate is optimum for the spawning and reproductive performance of female yellow catfish for the first artificial spawning, and 46% dietary protein group had the best reproductive performances in the second spawning. [ABSTRACT FROM AUTHOR]

The present study provides the complete report on the embryonic and larval development of pink ear emperor, Lethrinus lentjan (Lacepede, 1802). Eggs were obtained from captive‐reared broodstock of pink ear emperors from 1‐year of age maintained in a 10‐tonne recirculating aquaculture system (RAS). The brood fishes spawned throughout the year without hormonal induction. Fertilized eggs (692.65 ± 6.67 µm) were pelagic, transparent, non‐adhesive and with a single oil globule measuring 146.63 ± 3.51 μm. Description of the different phases of embryogenesis, namely the zygote, cleavage, blastula, gastrula, segmentation of the fish is provided. Additionally, the developments during larval development period after hatching, which extends till the completion of yolk‐sac absorption (pre‐larvae) and the end of metamorphosis (post‐larval) are also included in the present study. The embryonic development was completed within 14 h 40 min after fertilization. The newly hatched larvae had an average body length of 1.39 ± 0.08 mm, with a yolk sac measuring 787.67 ± 42.65 µm. The mouth opening was observed at 2 days post‐hatch (dph). The yolk sac was completely absorbed by 2 dph, and the preflexion stage began, and it continued till 14 dph. Notochord flexion began by 15 dph and extended to 20 dph. The appearance of the typical adult colouration and scale formation started by 22 dph and by 35 dph the larvae reached the juvenile stage. The data on the embryonic and larval development will help to standardize the larval rearing techniques for the species. [ABSTRACT FROM AUTHOR]

Summary: Using a forward projecting population model, the timing and scale of Lake Sturgeon Acipenser fulvescens (LS) recovery and natural reproduction was estimated for the Milwaukee River in Wisconsin, USA for the years 2004–2048. LS, a widely distributed potamodromous Acipenseridae species in North America, have, like other sturgeon species, suffered population declines due to overharvest and other factors since the 1800s. LS recovery efforts were initiated in the early 1980s following the successful development of LS propagation techniques and stocking has become a widely utilized tool in LS recovery programs. Sturgeon recovery programs are long‐term endeavors, with annual stocking usually planned for 25 plus years, along with population assessments and habitat improvements conducted over decades before project success can be verified. LS recovery activities on the Milwaukee River, a Lake Michigan tributary in southeast Wisconsin, began with barrier mitigation in 1997 and stocking in 2003. The modest size of the Milwaukee River, along with habitat improvements, and 17 years of stocking, provided an opportunity to model and predict LS population recovery trends. A forward projecting population model with an imbedded stochastic Ricker stock‐recruitment relationship, adjusted for the estimated LS productive capacity of the Milwaukee River, estimated the timing and scale of LS recovery during 2004–2048 predicting a 18.3% annual average population rate of increase during the stocking period, and a 5.7% post‐stocking rate. Accelerated LS growth and maturity due to goby consumption built into the model resulted in projections of gravid adult males present in 2012 and spawning adult females and natural recruitment in 2019. During the 2020 spawning period a group of adult‐sized LS were observed in the Milwaukee River below an intermittent barrier on the river. The model predicted adult LS densities to grow from 22 in 2012 to 8088 in 2048, and annual natural recruitment to grow steadily from 76 yearlings in 2019 to an average of 4000 yearlings/year during 2039‐2049. The estimated number of yearling recruits per spawning (gravid) female dropped steadily from 21 in 2019 to 8 recruits per gravid female in 2048 as a function of the Ricker stock‐recruitment relationship built into the model. The model results indicate that significant LS recovery can possibly begin in a shorter time frame on Great Lakes tributaries than originally expected through systematic resolution of habitat issues and LS stocking. Results can also be used to help anticipate recovery trends, fine tune stocking and habitat strategies, and plan LS recovery assessments. [ABSTRACT FROM AUTHOR]

Tawera elliptica is a small size (baby) clam with an export fishery in southern Chile. The species is dioecious with external fertilization and without sexual dimorphism. The aim of this work was to optimize broodstock conditioning, induce spawning and describe embryonic development until the early larval stage in a hatchery. Broodstock were conditioned at 3 treatments (with/without sand; water circulation) for 48 days. The clams were fed with a mixed diet of macroalgae, with a daily ration of 250,000 cells/ml. Broodstock response was quantified using condition index and gonad development stages (histological techniques). For spawning induction, physical and biological methods were tested. The best response was achieved in males with physical induction. Histological analysis showed that the water circulation system treatment exhibited the highest percentage of maximum maturity. A fertilization ratio of 500:1 sperm:oocyte was used. The incubation was carried out in 3‐L containers with filtered seawater at 10.7 ± 0.9°C without aeration. Observations, measurements and the duration of each embryonic and larval stage were recorded. The oocyte has a prominent gelatinous layer (= jelly coat) that disappears between the gastrula and trochophore stages. The status of the D‐larval stage was reached at 107 h post fertilization with a mean valve length of 91.4 ± 8.9 µm. This is the first record of the complete embryonic development of this baby clam until the early larval stage and the conditioning in a water circulation system for 48 days are suitable for the species. [ABSTRACT FROM AUTHOR]

Relatively little is known of the effects of time of day of hormone injection on latency period in most fishes. Interest in improved culture techniques for White Crappie (Pomoxis annularis) has led to advances in tank holding and induced spawning methods. However, an understanding of latency period is needed for synchronizing and optimizing White Crappie hatchery production. Therefore, the effects of hormone injection timing on latency period and egg viability were examined. Crappie were injected with gonadotropin‐releasing hormone analog (GnRHa) at 1600 (evening treatment) and 0800 (morning treatment), monitored for latency period duration, and spawning success was determined using percent of females ovulated, ovulated egg volume and egg fertilization percent. In the evening treatment group, 75% of the females ovulated 48.40 ± 2.70 (mean ±SE) hours post initial injection and had a mean egg fertilization rate of 63%, while in the morning injection treatment, 91% of females ovulated 44.58 ± 1.36 h post initial injection and had a mean fertilization rate of 56%. No significant difference in mean latency period or spawning success was observed between treatments. Therefore, diel timing of hormone injection did not affect latency period or spawning success in White Crappie, allowing for flexibility in production. [ABSTRACT FROM AUTHOR]

The present study provides the first detailed early embryonic development of the Shalyni barb, Pethia shalynius (Yazdani & Talukdar, 1975), a vulnerable cyprinid fish occurring in streams and lentic waters of Meghalaya, northeast India. Induced spawning by synthetic hormone injection in May 2019 was conducted to a pair of mature female and male P. shalynius under controlled conditions in a well‐aerated aquarium. Fertilized eggs were spherical, 0.75–0.80 mm (approx.) in diameter, transparent, unpigmented and non‐adhesive. A total of 22 developmental stages could be categorized under seven broad periods, viz. the zygote, cleavage, blastula, gastrula, segmentation, pharyngula and hatchling. The first cleavage occurred at 15 min post fertilization (mpf), followed by blastulation at 01:23 hr post‐fertilization (hpf), gastrulation at 04:20 hpf, initial somite formation at 07:00 hpf, and pharyngula period at 19:20 hpf, respectively. Embryos hatched between 26–27 hpf and the newly‐hatched larvae ranged 2.2–2.5 mm in total length. For naturally‐declining populations of this vulnerable fish species, inferences drawn from the present study will help provide a baseline data for its conservation and management, and aid the research fields of developmental biology, biotechnology, molecular biology as well as taxonomy of this species. [ABSTRACT FROM AUTHOR]

We analyzed ovarian dynamics of anadromous blueback herring, Alosa aestivalis, in Connecticut River with the principal aim of exploring oocyte recruitment and how it shapes the fecundity pattern. We examined the oocyte release strategy and analyzed spawning cyclicity by linking oocyte growth to the degeneration of postovulatory follicles. Females were accordingly classified as pre‐spawners, early and late active spawners, and oocyte recruitment intensity was compared among the different spawning phases. Oocyte recruitment occurred continuously and in parallel with spawning activity, a pattern which is diagnostic of indeterminate fecundity. However, both fecundity and oocyte recruitment intensity progressively decreased (tapered) throughout spawning, until the ovary was depleted of vitellogenic oocytes. There was no massive atresia of vitellogenic oocytes at the end of the spawning season, which is atypical of indeterminate spawners. We propose that tapering in oocyte recruitment and fecundity is an adaptation to the high energetic expenditure of the upstream spawning migration. [ABSTRACT FROM AUTHOR]

A major challenge in Clariid catfish seed production is our inability to induce voluntary captive spawning of the brooders. Since voluntary captive spawning had been previously elicited in a Clarias species by simulating natural breeding environment, we speculated that the major obstacle in voluntary spawning might be the absence of an inducing agent that triggers mating response in the brooders. To address the issue, oxytocin was injected to the brooders along with Ovatide (a commercial inducing agent comprising salmon gonadotropin‐releasing hormone analogue and domperidone). Administration of 40 mIU/kg body weight of oxytocin after 12 hr of Ovatide injection resulted in voluntary spawning of the fish (81.5%, i.e. 31 out of 38 trials), with more than 70% hatching rate in simple and low‐cost spawning facilities. Histology of male gonads indicated sustained gamete maturation and the gonads were observed to be visibly turgid in the fish that received both the hormones. In contrast, gamete maturation slackened after 10 hr in the control fish, injected with Ovatide only. Administration of oxytocin along with Ovatide was also observed to induce aggressive sexual behaviour among the males. Neither of the hormones, acting alone, could induce voluntary spawning in the fish or influence sexual behaviour. Our results clearly show that oxytocin plays a significant role in sustaining the male gamete maturation induced by Ovatide and trigger the behavioural mating response, leading to voluntary spawning in C. magur. The results hold potential to make a paradigm shift in the commercial catfish seed production technology. [ABSTRACT FROM AUTHOR]

The ontogenetic structure and longitudinal variability of ichthyoplankton in a confluence zone of two river systems in the Eastern Amazon were evaluated between December 2018 and April 2019, at the time 137 eggs and 7,687 larvae of fish were captured. Ichthyoplankton proved to be heterogeneous between sections of rivers with differences in the number of taxa and abundance. The assemblages were distinguished by a NMDS Analysis, a ANOSIM, a SIMPER and a CCA, they presented a spatial zonation pattern with strong distinction and variability in the composition of the species between the river systems, under strong influence of limnological variables. The assemblages were mainly represented by larvae of Clupeiformes and Perciformes in the clear waters of the Tapajós river and Characiformes and Siluriforms in the cloudy waters of the Amazon river, influenced by the existence of a limnological gradient. Larvae in more advanced development stages were predominant in the Tapajós river while early stages were dominant in the Amazon river. The confluence zone does not seem to be a spawning area, but it is an important transport site for the larvae to reach the nursery areas in the lower stretch of the Amazon river. The encounter of these two river systems seems to guarantee the survival and biological recruitment of several fish species. [ABSTRACT FROM AUTHOR]

Reproductive migration of a Telestes species is reported for the first time for the Balkan endemic Telestes pleurobipunctatus (Stephanidis, 1939) from Louros River (Northwestern Greece), while the embryonic and larval development is also described for the first time for this species and genus. Adult fish migrate in late winter upstream and spawn in a peak of 2–3 nights in the outflow of springs. Embryos at hatching measure approx. 6.0 mm notochord length (NL), flexion starts at 8.1 mm NL and food particles are noted in the digestive tract of larvae at 8.2 mm NL. The larval period is characterized by the sequential formation of fins and the development of scalation. Fin differentiation ends with the completion of pelvic fin rays and the disappearance of the pre‐anal finfold at 20.0 mm. First scales appear at 17.0 mm standard length (SL) and scalation completes at 27.8 mm SL. We propose that the size at a specific ontogenetic event, the pigmentation pattern and the pre‐anal myomeres' number comprise diagnostic characters that permit distinguishing T. pleurobipunctatus larvae from other sympatric cyprinids. We note the rare pattern of scale scalation and pigmentation pattern of the target species. Parapatric speciation in T. pleurobipunctatus possibly related to its spawning migration pattern, as well as the use of larval identification in monitoring and conservation programmes targeting threatened cyprinids exhibiting this type of reproductive behaviour are also discussed. [ABSTRACT FROM AUTHOR]

Pinfish, Lagodon rhomboides, and pigfish, Orthopristis chrysoptera, are popular marine baitifsh used throughout the southeastern United States. Well‐defined methods exist for closing their life cycles in captivity and are being used for commercial aquaculture efforts for each species. Multiple spawning hormones have been effective for spawning induction for both species. Evaluations of a type II gonadotropin‐releasing hormone (cGnRH IIa) have proven it effective for induced spawning in channel catfish, and it has been proposed to be an effective hormone for induced spawning in other species. Four dosages (25, 50, 100 and 200 μg/kg) of cGnRH IIa for spawning induction along with a negative (saline at 0.5 ml/kg) and positive control (Ovaprim® at 0.5 ml/kg) treatment were evaluated for both species. Pinfish and pigfish responded to every cGnRH IIa tested, with up to nine viable spawns collected from pigfish at 100 μg/kg and up to five viable spawns collected from pinfish at 200 μg/kg. The amount of sinking eggs spawned, egg and larval size, and hatching success and survival to first feeding differed significantly for pigfish. Total egg production, fecundity, egg and larval size, and hatching success and survival to first feeding were significantly different for pinfish. While effective for spawning induction in both species, there may be some decrease in spawn quality associated with cGnRH IIa, at least for pigfish. Future research directed towards understanding the potency and physiological reactions caused by cGnRH IIa will help corroborate findings of higher egg output and reduced egg and larval quality. [ABSTRACT FROM AUTHOR]

Here, we describe the biological and ecological differences between partially anadromous Dolly Varden and riverine stone charr distributed in the Kamchatka River middle course. Endemic stone charr, being the ambush predator, is defined by the accelerated growth and prolonged lifespan, robust body, and large mouth, as well as specific marble coloration since an early age. The significant restriction in gene flow between the stone charr and benthos‐eating Dolly Varden was supported by an allelic distribution of eight microsatellite loci. Herewith, the identity of mitochondrial DNA control region and intron sequences of growth hormone and metallothionein genes confirms a relatively recent diversification of the groups within the single basin. We suggest the key role of the specific environment for reproduction isolation of stone charr. It occupies coniferous taiga zone with dark‐colored water, whereas Dolly Varden spawns uppercourse in the zone of stunted, windblown forest. Conifer litter decomposition products could drive natural selection of stone charr via metabolism acceleration and resistance to toxicants. The metabolic difference could promote piscivory and development of the specific morphological peculiarities of the stone charr. Therefore, we present the first evidence in favor of trophic‐based sympatric diversification in a river basin at high latitudes. [ABSTRACT FROM AUTHOR]

The study provides new information on the reproductive biology of Hypselobarbus thomassi (Day, 1874) an endemic cyprinid fish in the Western Ghats–a biodiversity hotspot of India. A total of 384 specimens (males = 244 and females = 140) were collected monthly from April 2009 to March 2011 from Kallada River of Southern part of Western Ghats, India. Monthly sex ratio indicated that males predominated in the fishery, and an overall sex ratio was significantly different from the expected value of 1:1 (male:female = 1:0.57, x2 = 28.17, p <.01). Based on the monthly analysis of gonadosomatic index (GSI) and the proportion of mature individuals, the spawning season of H. thomassi occurred between May to October with a peak in June to August. The length at first maturity (L50) recorded was 290 mm TL in males and 330 mm TL in females. The absolute fecundity ranged between 305 (234 mm TL) to 1,089 (414 mm TL) and relative fecundity oscillated between 77.3–220.69 oocytes/g of fish. The fecundity established a linear relationship with total length, body weight and ovary weight. The findings of this study would be very effective to impose sustainable conservation plan for this threatened species in Kallada River and other Western Ghats river systems. [ABSTRACT FROM AUTHOR]

Multiple spawnings are special reproductive tactics that many fish evolved to obtain different types of direct and/or indirect spawning benefits. This has led to two pertinent questions: (a) what types of benefit does a commercially important fish provide during multiple induced spawnings annually? and (b) is there any trade‐off between traits during these spawnings? To address these questions, the present study was carried out with two separate experiments during two spawning events of an Indian major carp (Catla catla) to assess: (a) male's spawning performances and (b) female's spawning performances. The male's spawning data revealed that they produced significantly higher amount of milt and hatchlings during the first spawning, while they significantly reduced hatchling deformation rate, enhanced offspring survival rate and enlarged offspring body size during the second spawning. The female's spawning information unveiled no significant differences in total egg weight, hatching rate and hatchling deformation rate between the first and second spawning. However, females had significantly higher offspring survival rate during the first spawning and enhanced offspring body size during the second spawning. Interestingly, the analysis of trait associations revealed that males allocated energy with a trade‐off between milt weight and offspring survival rate, whereas females showed a trade‐off between hatching rate and offspring survival rate. Thus, the study provides some important information for carp breeders and associated stakeholders to know which spawning season is preferable for the higher production of eggs, milt and good quality larvae. [ABSTRACT FROM AUTHOR]

The percent of egg fertilization was highest in the 3:1 sex ratio with low water velocity (mean = 51.5 ± 4% SE), while lowest fertilization occurred under a 1:1 sex ratio and high flow (mean = 21 ± 7% SE; Figure 2). GLO:EV7/01jun20:jai14031-fig-0002.jpg PHOTO (COLOR): 2 Lake sturgeon (Acipenser fulvescens) egg fertilization success (average % ± standard error) across three different sex ratios (milt volumes) and water velocity treatment combinations. There was no statistical difference in fertilization success among the 4 males used in this study (1:1 sex ratio) and thus we conclude that variation in sperm quality, which is observed in lake sturgeon (see Toth, Ciereszko, Christ, & Dabrowski, [26]), did not drive variation in fertilization success. [Extracted from the article]

Pejerrey Odontesthes bonariensis spawning period takes place during the end of winter and spring and, depending on temperature conditions, during late summer and autumn. Nevertheless, the occurrence and quality of the summer–autumn spawning period have not been well documented and are not considered for aquaculture production. In this context, this study aimed to characterize the reproductive activity of pejerrey reared in captivity under natural conditions of temperature and photoperiod throughout a year in order to summarize the spawning quality of the two spawning periods. The present results showed that pejerrey might spawn from late winter to the end of the spring with a peak in October (mid‐spring) and, also during summer and early autumn, interrupted by a period of 56 days without spawning activity in between. The extension of both spawning periods was almost equal (67 and 69 days). Nevertheless, higher relative fecundity and larger egg size were observed during the first spawning period, associated with higher levels of oestradiol measured in females demonstrating that it is better than the second spawning. The fertilization rate was not affected throughout the reproductive periods. These differences in the reproductive parameters are discussed in order to design specific strategies to increase seed production. [ABSTRACT FROM AUTHOR]

Caspian roach (Rutilus rutilus caspicus), a spring spawning teleost, were subjected to various photoperiod and temperature regimes to study the feasibility of shifting the timing of spawning for artificial propagation purposes. A total of 650 female reproductively mature R. rutilus caspicus were subjected to different photoperiod and temperature regimes including four light regimes (natural light (NL), 16 hr of light (L):8 hr of darkness (D), 9L:15D, 11L:13D), each affected by three temperature regimes (14, 20 and 24°C) for 70 days. Five fish per tank were randomly sampled on Feb. 10, Feb. 20, March 28, April 15 and April 30 (natural spawning time). Ovarian tissue sections were studied using light microscope and transmission electron microscope (TEM). The levels of 17‐β estradiol (E2) and 17α‐hydroxyprogesterone (OHP) were also measured in the serum samples. In late winter (March 28th), the gonadal maturation and spawning were accelerated in fish treated with the long day length (16L/8D) and warm temperature (20°C). While, the maturation of oocytes and spawning delayed in fish exposed to low temperature (14°C) and short day length (9L/15D and 11L/13D). Photoperiod seems to play a more important role in the ovarian development of the R. rutilus caspicus compared to temperature; since even among the fish treated with the lowest temperature (14°C), those exposed to a longer day length (16L/8D), matured and spawned earlier than the others. Considering that the earliest spawning occurred in R. rutilus caspicus treated with 16L/8D at 20°C and the latest spawning occurred in fish exposed to low temperature and short photoperiod, it can be concluded that temperature and photoperiod play an important role in accelerating oocyte maturation and spawning. [ABSTRACT FROM AUTHOR]

Knowledge of fecundity in fishes is important for understanding life history, modeling population dynamics, developing fisheries management and determining conservation status. Sturgeon species are known for their high fecundity but to date only two populations of Atlantic sturgeon (Acipenser oxyrinchus Mitchill, 1815) have been examined for this aspect of their biology. The species is protected in most regions of eastern North America but the Saint John River, New Brunswick supports one of the two remaining commercial fisheries in Canada. Sixty females selected by this fishery were sampled for total length, weight, age, gonad weight and egg number. Absolute fecundity ranged from 153,630 to 1,306,626 eggs, with a mean fecundity of 582,832 ± 261,806 eggs. Absolute fecundity exhibited a significant positive relationship to increasing body weight but not to total length or age. Relative fecundity ranged from 129 to 216 eggs/g gonad weight and although it declined with both increasing body size and age the relationships were not significant. The Gonadosomatic Index (GSI) ranged from 1.3% to 27.0% with a mean of 7.8% ± 4.94 SD. Relative fecundity found in this study was higher and mean GSI lower than reported for other Atlantic sturgeon populations and other sturgeon species. Differences were probably due to location of the fishery downstream from spawning sites and selection of pre‐spawning females by the commercial fishery. [ABSTRACT FROM AUTHOR]

In this experiment, golden rabbitfish (Siganus guttatus) were allocated between three treatment groups. The fish were injected with saline, human chorionic gonadotropin (hCG) and D‐Ala6, Pro9‐Net‐mGnRH. After injection, in 6 hr intervals, blood plasma samples were collected for steroid hormone (testosterone [T] in males and estradiol‐17β [E2] in females) using enzyme immune assay (EIA). In male fish, T levels significantly increased and reached 170 and 650 pg/ml for hCG and D‐Ala6, Pro9‐Net‐mGnRH treatments, respectively. Then T levels slightly decreased until 24 hr post injection. There were no significant changes of T levels in saline treatment. In female fish, we found significant changes in E2 levels at 2,567 and 524 pg/ml at 12 hr post injection in hCG and D‐Ala6, Pro9‐Net‐mGnRH treatments, respectively. No significant differences of E2 levels were observed in saline group. In the second experiment, we injected 100 golden rabbitfish with both hCG and D‐Ala6, Pro9‐Net‐mGnRH. Fish spawned successfully when hCG and D‐Ala6, Pro9‐Net‐mGnRH were given individually and in combination. Latency periods were between 46–64 hr with an average fertilization rate of 70%–90% and hatching rate of 56%–74%. The embryonic duration was 16–20 hr. The saline‐injected group produced no spawning. Our findings contribute to further understanding of exogenous hormones impact on golden rabbitfish reproductive endocrinology, refining breeding protocol and implications for fish propagation. [ABSTRACT FROM AUTHOR]

Keywords: embryonic development; hatching; longfin yellowtail; salinity tolerance However, information regarding the effects of specific environmental conditions (e.g. salinity) on the incubation of eggs and yolk-sac larvae of longfin yellowtail is scarce. A one-way analysis of variance ANOVA (trial 1) and two-way ANOVA (spawn sources and salinity; trial 2) were used to compare the effects of salinity on eggs and yolk-sac larvae. [Extracted from the article]

The main goal of this research was to find out about the influence of temperature as one of the important environmental factors on the sex development of carp and examine the differences in production between male and female sexes within one particular treatment. We have chosen these temperature treatments because the 21-29°C range is the optimum temperature for carps, and only a very small temperature difference can cause significant shift in the sex ratio (Cheng, Lin, & You, [2]; Lin & You, [8]). Examination of sex ratios of each temperature treatment of the 12-month-old fish was analysed using chi-squared test. Although results of the T29 treatment showed lower body weight than those of the T22 and T25 treatments, females still had higher average body weight of 118.0 ± 30.3 g and males a corresponding 105.8 ± 55.7 g. [Extracted from the article]

Feeding activity of pikeperch (Sander lucioperca) under winter and spring photothermal conditions of pre-spawning period Keywords: feeding behaviour; pond culture; predation; prey selection; trophic ecology; wintering Size-dependent prey selection in piscivorous pikeperch Sander lucioperca and Volga pikeperch Sander volgensis haped by bimodal prey size distribution. Effect of gonadotropin hormonal stimulation on out-of-season propagation success of different year classes of indoor-reared pikeperch (Sander lucioperca (L.)). [Extracted from the article]

The administration of exogenous hormones for induction spawning of captive fish is a common practice throughout the finfish aquaculture industry. Induced spawning protocols for ornamental cyprinids commonly rely on sGnRH IIIa, commercially available as Ovaprim. In this study, the efficacy of an alternative spawning aid, cGnRH IIa, was evaluated relative to Ovaprim, in two commonly cultured ornamental Cyprinids: the Redtail Sharkminnow Epalzeorhynchos bicolor and the Rainbow Shark E. frenatum. Broodstock of each species were injected with either a positive control (0.5 µl/g Ovaprim), a negative control (propylene glycol) or one of three doses of cGnRH IIa (50, 100, or 200 µg/kg). Following spawning aid injection, ovulation success, fecundity, fertilization success, embryo diameter, hatch success and larval notochord length were evaluated. Ovulation success (82 ± 8%) was statistically similar to the positive control group for all experimental doses of cGnRH IIa in E. bicolor, while 50 and 100 µg/kg cGnRH IIa doses resulted in significantly higher ovulation success (100.0% and 83.0% respectively) than the positive control (17.0%) in E. frenatum. All other parameters did not vary significantly among treatments. These results indicate cGnRH IIa can be successfully used as a spawning aid in both species. [ABSTRACT FROM AUTHOR]

Continued study of the relationship between lake sturgeon (Acipenser fulvescens) recruitment and hydroelectric dams and operations, in a variety of river systems and habitat types is needed to improve the ability to predict and monitor impacts of the hydroelectric industry on this species. Herein, we present results of a juvenile lake sturgeon study aimed at addressing concerns over an inferred lack of recruitment resulting from spawning downstream of a hydroelectric generating station (HGS). Two years of sampling (2015 and 2016) were conducted in five sections of a 41 km long reach of the Seine River, Ontario, a lake sturgeon spawning tributary of Rainy Lake. Using an established gillnetting method, deepwater habitat was targeted to capture juvenile lake sturgeon to assess relative abundance, recruitment (cohort strength), and growth. Deepwater habitat, defined as water depths >6 m in this system, comprised only 2.1% of the wetted area in this study area. Within these habitats, a total of 331 lake sturgeon capture events were observed over the 2‐years study period. The majority of the lake sturgeon catch (85%) was comprised of age‐0 to age‐5 individuals (both sampling years combined). Although inter‐annual variation in cohort strength was apparent, each cohort between 2006 and 2016 was represented. The spatial distribution of cohorts varied among river reaches with younger individuals (age‐0 and age‐1) occupying reaches proximal to the Sturgeon Falls HGS, and larger, older individuals (age‐2 to age‐5) occupying reaches further downstream. The rarity of age‐6+ individuals can likely be explained by ongoing downstream redistribution of juveniles over time, out of the Seine River and into Rainy Lake. Growth of juvenile lake sturgeon captured in the Seine River was above average relative to conspecifics from other rivers in the Hudson Bay drainage. Unfortunately, baseline data sets required to facilitate comparisons of contemporary (post‐construction Sturgeon Falls HGS) versus historical (i.e. pre‐ Sturgeon Falls HGS) lake sturgeon recruitment, or to evaluate the influence of the Seine River Water Management Plan (2004) on lake sturgeon recruitment, are lacking. However, juvenile Lake Sturgeon are more abundant in this system than what had been surmised based on recent studies which implemented random sampling. Results indicate that juvenile lake sturgeon may reside in spawning tributaries for several years (age‐0 to age‐5) prior to seeking alternate habitats and highlights the value of targeted sampling (i.e. by depth) along the flow axis of rivers downstream of spawning areas when assessing lake sturgeon recruitment patterns. [ABSTRACT FROM AUTHOR]

Acipenseriformes (sturgeons and paddlefish) globally have declined throughout their range due to river fragmentation, habitat loss, overfishing, and degradation of water quality. In North America, pallid sturgeon (Scaphirhynchus albus) populations have experienced poor to no recruitment, or substantial levels of hybridization with the closely related shovelnose sturgeon (S. platorynchus). The Lower Missouri River is the only portion of the species' range where successful reproduction and recruitment of genetically pure pallid sturgeon have been documented. This paper documents spawning habitat and behavior on the Lower Missouri River, which comprises over 1,300 km of unfragmented river habitat. The objective of this study was to determine spawning locations and describe habitat characteristics and environmental conditions (depth, water velocity, substrate, discharge, temperature, and turbidity) on the Lower Missouri River. We measured habitat characteristics for spawning events of ten telemetry‐tagged female pallid sturgeon from 2008–2013 that occurred in discrete reaches distributed over hundreds of kilometers. These results show pallid sturgeon select deep and fast areas in or near the navigation channel along outside revetted banks for spawning. These habitats are deeper and faster than nearby river habitats within the surrounding river reach. Spawning patches have a mean depth of 6.6 m and a mean depth‐averaged water‐column velocity of 1.4 m per second. Substrates in spawning patches consist of coarse bank revetment, gravel, sand, and bedrock. Results indicate habitat used by pallid sturgeon for spawning is more common and widespread in the present‐day channelized Lower Missouri River relative to the sparse and disperse coarse substrates available prior to channelization. Understanding the spawning habitats currently utilized on the Lower Missouri River and if they are functioning properly is important for improving habitat remediation measures aimed at increasing reproductive success. Recovery efforts for pallid sturgeon on the Missouri River, if successful, can provide guidance to sturgeon recovery on other river systems; particularly large, regulated, and channelized rivers. [ABSTRACT FROM AUTHOR]

Management and conservation have begun to rely on supplemental information to make appropriate decisions. In organisms with little available information, preserved specimens may be particularly important for researchers to continue their role in the management process. Bluenose Shiners are a minnow species that can benefit from such analyses as they are of conservation concern across their native range in the Southeastern United States. To supplement conservation, the objectives were to: (a) quantify sexual dimorphism through a comprehensive morphological analysis, (b) approximate peak spawning condition of males and females through GSI measurements over the anticipated spawning season, and (c) utilize female gonad histology to refine conclusions regarding spawning condition from GSI. Historical collections of Bluenose Shiners obtained from the Tulane University Biodiversity Research Institute were used to conduct morphological and gonadal analyses. While males expressed all morphometrics to a greater degree, male dorsal and anal fin length appears to be the most distinguished characteristic beginning at a total length of approximately 45 mm. GSI displayed peaks in the samples from April 21, 1957 and June 1, 1968; female GSI from Black Creek, MS in April, May, and June of 1986 suggested a peak in late May. Gonad histology showed a progression towards final oocyte maturation through May to early June, via relative prevalence of stage IV and absence of stage I oocytes. This information can be used to supplement future morphometric analyses and reproductive studies performed on Bluenose Shiners or other fish species. [ABSTRACT FROM AUTHOR]

The population of the freshwater animal was declined day by day due to the degradation of habitat and use of illegal fishing methods, which cause a great threat to these aquatic animals. The main purpose of this study was to scrutinize the wild population and fecundity of freshwater prawn Macrobrachium assamense peninsulare in Rawasan stream to assess the health status of prawn. Fecundity was estimated by a random sampling of prawn from five selected sites of Rawasan stream. A wild collection of a total of 35 ovigerous females was collected for an interval of 2 years (August 2013–July 2015) from May to September month, that is breeding session. The maximum number of eggs was 102 eggs in an individual having 52 mm total length and 2.66 g body weight. It was concluded that fecundity of Macrobrachium assamense peninsulare was low, and egg dimension was larger than other closely related species of freshwater prawn. Fecundity of Macrobrachium assamense peninsulare showed a positive relationship with a total weight (R2 = .71) and moderate with the total length (R2 = .38). A strong correlation exists between egg mass and total weight, and between egg mass and total length of female (R2 = .849 and R2 = .77 at p < .05) respectively. The numbers of eggs, that is fecundity, in a female were increased with the body growth of an individual, which results in a linear graph. [ABSTRACT FROM AUTHOR]

The reproductive dynamics of a species is important information to have for the maintenance and reproduction of animals in captivity, for either commercial or conservation purposes. Steindachneridion melanodermatum is an endemic fish that has been reproduced by breeding protocols, but knowledge related to the maturation and reproductive cycle of this species is scarce. The purpose of this research was to observe different parameters related to the reproductive biology of males born in captivity over a 24‐month period to determine the first maturation and reproductive activity of S. melanodermatum males maintained in captivity. Body development changes (weight and length) were observed, and gonadosomatic index (GSI) and plasma sex steroids (testosterone and 17β‐estradiol) were measured monthly. Phases of the reproductive cycle were detected based on macroscopic changes and histological observations of the testes. The obtained data were correlated, demonstrating that the GSI values accompanied testis development and sex steroid peaks. Additionally, immunohistochemistry was performed for the detection of KI‐67, 3β‐HSD and Vasa protein. Our data analysis indicated that the first maturity in males bred in captivity occurred after one year (at 22‐month‐old fish), with a reproductive period occurring from September to November, which is the spring season in the southern hemisphere. [ABSTRACT FROM AUTHOR]

The wild stocks of large yellow croaker Larimichthys crocea and yellow drum Nibea albiflora have been depleted since the 1980. Although the Chinese government has put a lot of effort (e.g., implementing fishing ban and releasing artificially bred fish into naturally distributed sea areas) into restoring their natural resources, the restoration still fails to expectation. We speculate that the slow restoration may be related to the increasing ship noise near the spawning grounds of these two species of fish. To test the harmfulness of ship noise on the L. crocea and N. albiflora, in our previous study, we studied the impacts of ship noise on their behaviors, parallelly, in the present study, we focused on the impacts of noise on their immunophysiological responses. We designed two experiments. In the first experiment, the juveniles were exposed to 120 dB ship noise for only once, then the plasma physiological indices were monitored every 1 hr within 4 hr. In the second experiment, the juveniles were exposed to 120 dB noise twice a day for 30 days, afterwards, the growth, plasma immune indices and intestinal microbiota were analyzed. The results showed that stimulated by ship noise, the physiological indices of L. crocea and N. albiflora both increased sharply within 3 hr. After a month noise stimulation, the growth and immune indices decreased significantly, and the proportion of intestinal microbiota was seriously imbalanced, showing Vibrio and Pseudomonas were dominant and other genera's abundance was quite low, especially some common intestinal probiotics. In addition, we also found that N. albiflora may be more sensitive to ship noise than L. crocea in terms of the required duration of physiological indices recovering to unstimulated level, and growth. This study highlights that ship noise negatively affects L. crocea and N. albiflora, which is helpful for some departments taking measures to protect the natural resource of these two species of fish. [ABSTRACT FROM AUTHOR]

We evaluated the annual process of oocyte and ovarian development of the planktivorous Amazonian catfish, the mapará (Hypophthalmus marginatus), aiming to support captive reproduction for domestication. A total of 149 females were captured from the Tocantins River at the Tucuruí Dam (3°49'55"S, 49°39'9"W) in 13 sampling events. For each individual, we evaluated ovary histology and plasma steroid concentrations. Two annual reproductive cycles, with similar characteristics, including a long period of rest, a short vitellogenic stage and a well‐defined spawning season from November to March, were described. A 17β‐estradiol (E2) rise and a 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) peak were associated with vitellogenesis and spawning season, respectively, in the first cycle but not in the second reproductive cycle. In conclusion, the studied species presents a reproductive cycle similar to that of other migratory total spawners; however, unusually for this group of fish, there were three (but not two) batches of vitellogenic oocytes in "in maturation" and "mature" stage ovaries, pointing to the possibility of more than one spawn during the spawning season. [ABSTRACT FROM AUTHOR]

The aim of the present study was to know the cyclic changes in gonadal maturation and to investigate the various developmental stages of oocytes and testicular germ cells of snow trout, Schizopyge niger. A total of 316 fish specimens were procured from three sites of river Jhelum during November 2016 to October 2017 and the histological analysis of their gonad was carried out. The results of the present study indicates that the male population was found significantly (p < 0.05) higher compared to female population and were reported as (1.6:1; M:F). The highest mean GSI value was recorded in male (12.24 ± 0.89) during the month of March and for female (13.74 ± 0.92) also in the month of March, which indicated that the gonadal development reached its peak during this month. The highest mean oocyte diameter was 1.04 ± 0.20 mm observed in March, showing that the oocyte reached its maturity during this month. Histological study of ovary revealed the evidence of vitellogenic yolk granule stage and ripe mature stage from December to April. While in case of male, four stages of spermatogenesis were distinguished and spermatozoa were highly abundant in the months of March and April. Mean ± SE of absolute fecundity was 3,224 ± 421 eggs and also, the relative fecundity was 69 egg/g body weight. Based on the results of GSI and the analysis of gonad histology, it was observed that the peak breeding season of S. niger occurred in the month of March. It was also noted that spawning period of this fish begins in the month of February and lasts till April with a peak breeding season in the month of March. The present study will provide a baseline information about the appropriate peak breeding of the fish, which will be useful for artificial breeding as well for prevention of fishing from natural habitat. [ABSTRACT FROM AUTHOR]

Summary: Gonad development of the silver therapon Leiopotherapon plumbeus in two volcanic crater  lake  habitats (Sampaloc Lake, Taal Lake) in south Luzon, Philippines was examined during the annual reproductive cycle. The minimum body size‐at‐maturity of fish in these two lake habitats was also compared. Four gonad development stages were characterized as basis for the classification of ovarian (immature, maturing, mature, spawned) and testicular maturation (immature, maturing, mature) phases. The occurrence of all development stages in individual gonads suggest an asynchronous development whereby advanced stages are recruited continuously from a pool of younger stage germ cells to result in elevated female and male GSI throughout the annual cycle due to active gonadogenesis. Together with the increasing occurrence of advanced stage oocytes and spermatozoa from March until October, the elevated GSI of fish may indicate peak gonadal growth during the onset of the dry season (December–January) for eventual spawning from the beginning (May–June) until the end of the wet season (October–November). In both lake habitats, male fish were smaller than females but, regardless of sex, the minimum size‐at‐maturity of fish in Sampaloc Lake was significantly smaller than fish in Taal Lake. Overall, asynchronous development during oogenesis and spermatogenesis allows for year‐round reproduction of silver therapon, with elevated gonad growth in the dry season in preparation for spawning during the wet season. Compared with fish in Taal Lake, a smaller size‐at‐maturity of fish in Sampaloc Lake may be a response of the wild fishery stock to long‐term high fishing mortality and degradation of the lake habitat. [ABSTRACT FROM AUTHOR]

Summary: The Chinese sturgeon (Acipenser sinensis) is an anadromous fish inhabiting the Yangtze River. Migration of Chinese sturgeon from the estuary to upper Yangtze River was blocked by Gezhou Dam, completed in 1981, and a new, much smaller, spawning ground was established below the dam. However, Three Gorges Dam began operating in 2003, altering hydrological conditions in the new spawning grounds and the impact on Chinese sturgeon reproduction was severe. The annual survey of Chinese sturgeon shows that both spawning scale and breeding population decreased during this period. To illustrate the impact of Three Gorges Dam on the spawning grounds and reproduction of Chinese sturgeon, the habitat suitability of spawning grounds on spawning day was simulated using River2D. Results show that the area of suitable spawning grounds positively correlates with the scale of reproduction and both have decreased sharply since 2003. [ABSTRACT FROM AUTHOR]

The sea growth of two whitefish forms, anadromous (Coregonus lavaretus lavaretus) and sea‐spawning (Coregonus lavaretus widegreni), was analysed using samples collected from the commercial sea catch in the Gulf of Bothnia (GoB) in the northern Baltic Sea during 1998–2014. In the GoB area, these two forms are possible to identify because the gill‐raker number and size at maturity vary between forms. The growth rate of the forms is linked to their feeding area. Sea‐spawning whitefish, which has a feeding migration near its home site, was shorter in the northern GoB (66°N–64°N) at the ages of 3–11 than those in the southern GoB (64°N–60°30′N). In the data, most whitefish were caught with gill nets in the GoB. The mesh sizes of gill nets capturing the anadromous form were mostly 35–45 mm, while those capturing the sea‐spawning form were <35 mm in the northern GoB. It is likely that the different growth trends for small and large whitefish were connected with differences in their recruitment for fishing. The length of anadromous females at the age of four sea years increased significantly, but the length of six‐year‐old anadromous female whitefish decreased over the catch years from 1998–2014. In contrast, the length of slow‐growing sea‐spawning whitefish of six years or older increased significantly in relation to the catch year in the gill‐net catch. The increase in the growth of young age groups in both forms was probably associated with the increasing temperature and the low fishing pressure on small fish. The decreasing age at capture for both forms and the depression of the mean size of old anadromous whitefish are signs of high fishing pressure with a high gill‐net effort that selectively removes the largest and oldest individuals of both forms. [ABSTRACT FROM AUTHOR]

We evaluated the effects of dietary vitamin E on the reproductive performance and antioxidant capacity of Macrobrachium nipponense female shrimp. Prawns were fed 0, 40, 80, 160, 320 or 640 mg vitamin E/kg diet for 60 days. The 80 mg/kg group had the highest weight gain and lowest feed conversion rates. And the highest spawning rates were observed in the 80 mg/kg group with no significant differences among the groups. The highest activities of lysozyme, acid phosphatase and alkaline phosphatase in hepatopancreas were obtained in the 160 mg/kg group. The activities of superoxide dismutase, catalase and glutathione peroxidase showed a decreasing trend in the hepatopancreas. The lowest content of malondialdehyde was obtained with 80 and 160 mg/kg vitamin E. Histological results showed that the number of restzellen cells in hepatopancreas and a number of follicular cells in ovaries increased with 160 mg/kg vitamin E. However, 640 mg/kg vitamin E resulted in damaged hepatopancreas tubules and oocytes. The highest vitellogenin and vitellogenin receptor gene expressions were observed with 160 mg/kg vitamin E. These results provide evidence that dietary vitamin E with 80 and 160 mg/kg plays a positive impact on reproductive performance and antioxidant capacity of female shrimp. [ABSTRACT FROM AUTHOR]

The article discusses a study on the effect of commercial probiotic Sanolife MIC, which is composed of Bacillus species, on reproductive processes in spawning berried prawn Macrobrachium rosenbergii caught at Karnaphuli River, Bangladesh. Topics include the benefits of using probiotics as a prophylactic approach to the target host, the administration of Sanolife to the experimental prawns while the control group did not receive any probiotics, and a comparison of the responses of both groups.

The present experiment was aimed at studying the conditioning, maturation and natural spawning of orange-spotted grouper, Epinephelus coioides, in a recirculatory aquaculture system ( RAS). Thirty fish ( n = 30; 3.35 ± 0.05 kg) were stocked in a circular tank of 125 m3 capacity fitted with an RAS for conditioning and broodstock development. After 15 days, 15 fish were implanted with 17 α methyl testosterone and letrozole at the rate of 5 mg and 0.2 mg/kg body weight, respectively, for conversion from female to male. The gonadal development started after 1 month, and by 90th day, 63.53 ± 3.78% and 2.07 ± 0.84% of the oocytes attained a size of 400-500 μm and 500-600 μm respectively. Natural spawning commenced in the RAS from 4th month onward after stocking and spawning continued round the year. The spawning pair showed courtship behaviour with a typical vertical burst of swimming just before release of gametes. The total number of eggs spawned during 1 year was 47.23 million with spawning frequency varying form 5 to 13 times per month. The association of spawning events with new moon day (lunar cycle) weakened as time progressed. The mean monthly fertilization and hatching rates varied from 77.80 ± 3.34% to 83.70 ± 1.76% and 82.80 ± 4.21% to 88.33 ± 1.39% respectively. The study proved that RAS is an efficient system that provides a stable, controllable and conducive environment for year-round natural breeding of orange-spotted grouper. [ABSTRACT FROM AUTHOR]

Florida pompano has been identified as a promising candidate for commercial-scale aquaculture production, but to date, little information is available regarding captive broodstock spawning characteristics. Genetic markers were tested for their power in monitoring mating outcomes and potential in analysing heritability of rapid growth trait in Trachinotus carolinus. A total of 20 unrelated adults (10 females and 10 males) were chosen for a hormone-induced mass spawning event. The 515 fastest growing and 485 slowest growing fish of the total 4852 offspring were considered a selected progeny stock, and fish were collected at 45 days post hatch based on their growth traits. Parentage analyses based on the 20 breeders and 1,000 selected progeny were performed using a total of nine microsatellite markers, a 100% assignment rate was achieved, and a four-marker set was the minimum number for the parentage assignment. The effective breeding number for the selected progeny was 11 (six females and five males), among which three females and two males were predominant contributors with the total contribution of 95.8% and 94.7% respectively. The proportion of fast-growing offspring from broodfish and each mating cross (sire/dam) was used for detecting whether variation in growth of the offspring was related to parental stocks. Results showed that three adults and their mated combination exhibited the greatest fast-growing offspring proportion (69.73% and 55.95%). This research provided new information regarding spawning performance and parental contribution during mass spawning events; both important first steps towards developing improved management strategies for captive Florida pompano broodstock. [ABSTRACT FROM AUTHOR]

The article offers information on topics related to Florida Largemouth Bass (Micropterus salmoides floridanus) hatchery fish. Topics mentioned include the management of fish hatchery, the genetic diversity in the fish production, and the guidelines for fish spawning. Also mentioned are the fish genetic diversity and the development of hatchery environment.

The article presents a study of the association of water temperature and daytime and migration intensity, as wel as the effect of water turbidity, light and obstacles on the spawning migration of the Caspian lamprey or Caspiomyzon wagneri. It highlights the importance of temperature and light during the spawning migration of the Caspian lamprey and the challenges of the propagation of lampreys in the Shirud River, India.

The article presents a study on the spawning distribution of Coilia nasus, a commercial species of fishes in China. Topics addressed include recognition of the species' spread throughout the Yangtze River, China and the ecology of the species in freshwater. Methodology and findings of the investigation are also discussed.

In the past decade improved acoustic hard- and software have enabled estimations of abundance and distribution patterns of aquatic organism, including non-intrusive monitoring of fish migrations and behaviour. In this study, a high frequency acoustic camera (DIDSON-LR, 1.2 MHz, 0.7 MHz) and a portable split-beam scientific echo sounder (Simrad EY60, 200 kHz) collected acoustic data on 192 and 157 individuals within 24 hr (19-20 April 2011) in the Mituo reach of the Yangtze River, China. Mean fish length estimated from the acoustic camera data was 18.7 ± 5.6 cm, with an average swimming speed of 0.19 ± 0.13 m s−1. The mean fish target strength (TS) produced by the echo sounder was −43.8 ± 4.4 dB, which corresponded to 5.7-119.9 cm fish length when converted by three different TS-length equations. Average swimming speed was 0.11 ± 0.06 m s−1 from the echo sounder. Compared with the actual fish catch by the three layers of drift gill net in the survey area, the target length indicated by DIDSON was more accurate than the EY60 results, which were highly affected by the choice of TS length equations. It was determined that the two devices used synchronously could estimate fish length effectively to investigate their behaviour and distribution. [ABSTRACT FROM AUTHOR]

Local adaptation may cause thermal tolerance to vary between nearby but distinct populations of a species. During the summer of 2013, alligator gar Atractosteus spatula spawned from broodstock collected from three populations within the Mississippi River drainage separated by a 5° latitudinal gradient were acclimated to three temperatures (25, 30, and 35°C). Ten fish from each population were acclimated at each temperature. CTMax was determined at each temperature for each population, using five fish for each population-acclimation temperature pairing. CTMax for each population-acclimation temperature pairing was compared using two-factor anova. CTMax increased significantly with acclimation temperature (F2,40 = 600.5, P < 0.001) but population had no significant effect (F2,40 = 1.882, P = 0.166). Temperature tolerance appears to be consistent across populations of alligator gar, with no evidence of local adaptation. [ABSTRACT FROM AUTHOR]