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A study of the early life history stages of fishes (ELH) in the area of the Połaniec Power Plant (PPP), the second largest power plant with an open cooling system located on the Vistula River, was conducted. Using next-generation sequencing, 17 fish species were found in the drift, five of which are protected by international (Natura 2000) or national law. It was estimated that in the spring and summer of 2023 from 10 to 17 × 106 ind. ELH, including 22–23% of protected species, was probably entrained and killed in the cooling system of the PPP. The water temperature within the mixing zone was found to be noticeably elevated (by an average of 5.5°C). In addition, a pronounced hydropeaking phenomenon was observed after the ELH sampling period (since spring 2024). All these pressures overlapping can cause very unfavorable conditions for aquatic organisms in the Upper Vistula River. [ABSTRACT FROM AUTHOR]

\nHIGHLIGHTSAt the end of the summer of 2023, in September, an intense water discolouration (red tide) accompanied by fish mortality was observed in the Gulf of Tadjoura. This discolouration of the seawater was caused by a potentially toxic dinoflagellate, Pyrodinium bahamense. The proliferation, located near the coast between the Moucha/Maskali islands and the city of Tadjoura, was significant enough to be detected by satellite imagery. P. bahamense had formed an almost monospecific bloom (90%), with a density of 1.8 × 106 cells l‒1 (22 September 2023). Other dinoflagellates such as Dinophysis miles, Dinophysis caudata, Tripos furca, Lingulaulax sp. (formerly Lingulodinium), Balechina sp. and Protoperidinium sp. were detected at very low concentrations. This study characterises P. bahamense through an integrated approach, combining detailed morphological analysis with molecular phylogenetic analyses based on the internal transcribed spacer (ITS) region and the D1–D3 regions of large subunit ribosomal (LSU rDNA). For the first time, we have molecularly identified the toxic ribotype from the Indo-Pacific in the Gulf of Aden region. This discovery highlights an emerging risk of this toxic ribotype in the eastern Mediterranean basin. This region, already facing various environmental challenges, may see its vulnerability heightened with the emergence of new risks. A red tide was formed in September 2023 by Pyrodinium bahamense.First morpho-molecular identification of P. bahamense in the Gulf of Aden.The genotype corresponded to the toxic ribotype and the Indo-Pacific ribotype.A red tide was formed in September 2023 by Pyrodinium bahamense.First morpho-molecular identification of P. bahamense in the Gulf of Aden.The genotype corresponded to the toxic ribotype and the Indo-Pacific ribotype. [ABSTRACT FROM AUTHOR]

In this study, we assessed the growth patterns and population characteristics of the Odontobutis potamophila in Nansi Lake to inform evidence-based management recommendations for the sustainable development of fisheries in the region. A collection of O. potamophila was taken from Nansi Lake between August 2017 and July 2018 (except February) to estimate the age structure, growth pattern, and mortality of the population. Edge-type analysis of sagittal otoliths indicated that a single annulus was formed from March to May. The results revealed that the age structure of O. potamophila consisted of four age groups (0-3 ages), with 0-1 year-old fish comprising about 85.11% of the harvest. An isometric growth pattern was observed, with the Logistic growth function providing the best fit for combined sexes. S L t = 172.94 / (1 + e − 0.458 (t − 0.79)) (n =591, R 2 = 0.622). Total mortality (Z), natural mortality (M), and fishing mortality (F) were computed as 1.69, 0.53, and 1.16/year, respectively. Meanwhile, the exploitation rate (E) was 0.69/year, in accordance with the rule of thumb (E>0.5, the fish stock was undergoing overfishing), which indicated the stock has been overfished slightly. These results showed that brief generation-time, dominance of juvenile fish and relatively high natural mortality of the O. potamophila provide essential information on the native fish species in Nansi Lake, which may be essential for conservation strategies and artificial propagation. At the same time, these results provide critical data for sustainable fisheries management in Nansi Lake and similar ecosystems. [ABSTRACT FROM AUTHOR]

Long-term data on the phytoplankton of the Bulgarian Black Sea (BBS) coast describe three states for the ecosystem: a "pristine" reference phase (1954–1970 years); an intensive anthropogenic eutrophication (1970–1992 years) phase; and a post-eutrophication phase after the early 1990s of the 20th century. The eutrophication period is characterised by ecosystem degradation and intense phytoplankton blooms, some of which were formed by the potentially toxic species Lingulodinium polyedra. This warm-water species is a red tide former that is associated with fish and shellfish mortality events. In the 1980s, L. polyedra reached the highest biomass of 84.4 g·m−3 in Varna Bay, BBS. The aim of this study (1992–2022) was to provide an overview of the development of L. polyedra in the phytoplankton biocenosis in the Bulgarian part of the Black Sea, taking into account the influence of anthropogenic stress and the climatic variables NAO and SST on the development of the species population. An analysis of the distribution of the dinoflagellate L. polyedra is based on a total of 5126 phytoplankton samples collected during the period between 1992 and 2022 under projects led by the Institute of Fish Resources, Varna. The samples were analyzed using standard methods validated for the Black Sea, and phytoplankton abundance and biomass were determined. The species are most abundant in summer in the coastal marine areas exposed to anthropogenic influence. During the analyzed period, a decrease in the abundance and biomass of L. polyedra in Bulgarian Black Sea waters were observed. It was found that the influence of climatic factors such as NAO and SST on the species population is from weak to moderate, and the correlation with NAO cycles is better expressed. [ABSTRACT FROM AUTHOR]

Devil rays (Mobula spp.) are caught in fisheries across the Indian Ocean, with reports of significant recent declines in catch and sightings. Globally, the few populations studied have extremely low population growth rates due to low fecundity and long reproductive cycles, making them highly vulnerable to overfishing. To allow for assessment of the current sustainability of devil ray catch in the Indian Ocean, we provide estimates of age using the caudal vertebrae; somatic growth using a Bayesian, multi-model approach; maximum intrinsic rate of population increase (rmax); and fishing mortality for Endangered Spinetail Devil Ray (Mobula mobular) and Bentfin Devil Ray (M. thurstoni) sampled from small-scale fisheries catch in Indonesia, Kenya, and Pakistan. The oldest individuals of Spinetail Devil Ray (n = 79) and Bentfin Devil Ray (n = 59) were 17.5 and six years, respectively. Both species had relatively low growth coefficients (k = 0.05 and g = 0.19 year−1, respectively), with the von Bertalanffy and logistic models providing the best fitting growth models, and low rmax (0.109 and 0.107 year−1, respectively) indicating that they are highly sensitive to overexploitation. Fishing mortality F estimates (0.16 and 0.18 year−1, respectively) were higher than rmax and exploitation ratio E (0.77 and 0.80, respectively) were higher than an optimum value of 0.5 for biological sustainability for both species, suggesting that the fisheries catches of the species are unsustainable. We demonstrate an approach to assess data-poor species and apply this to two Indian Ocean devil ray species. The results highlight the urgent need for better management actions to reduce the catch of all devil rays to prevent species extinction and aid in population recovery. [ABSTRACT FROM AUTHOR]

Photosynthetic eukaryotic microalgae are key primary producers in the Antarctic sea ice environment. Anticipated changes in sea ice thickness and snow load due to climate change may cause substantial shifts in available light to these ice-associated organisms. This study used a laboratory-based experiment to investigate how light levels, simulating different sea ice and snow thicknesses, affect fatty acid (FA) composition in two ice associated microalgae species, the pennate diatom Nitzschia cf. biundulata and the dinoflagellate Polarella glacialis. FA profiling and transcriptomic analyses were used to compare the impact of three light levels: High (baseline culturing conditions 90 ± 1 μmol photons m−2 s−1), mid (10 ± 1 μmol photons m−2 s−1); and low (1.5 ± 1 μmol photons m−2 s−1) on each isolate. Both microalgal isolates had altered growth rates and shifts in FA composition under different light conditions. Nitzschia cf. biundulata exhibited significant changes in specific saturated and monounsaturated FAs, with a notable increase in energy storage-related FAs under conditions emulating thinner ice or reduced snow cover. Polarella glacialis significantly increased production of polyunsaturated FAs (PUFAs) in mid light conditions, particularly octadecapentaenoic acid (C18:5N-3), indicating enhanced membrane fluidity and synthesis of longer-chain PUFAs. Notably, C18:5N-3 has been identified as an ichthyotoxic molecule, with fish mortalities associated with other high producing marine taxa. High light levels caused down regulation of photosynthetic genes in N. cf. biundulata isolates and up-regulation in P. glacialis isolates. This and the FA composition changes show the variability of acclimation strategies for different taxonomic groups, providing insights into the responses of microalgae to light stress. This variability could impact polar food webs under climate change, particularly through changes in macronutrient availability to higher trophic levels due to species specific acclimation responses. Further research on the broader microalgal community is needed to clarify the extent of these effects. [ABSTRACT FROM AUTHOR]

Background: Probiotics and essential oils feed supplements are widely used in the aquaculture sector. This study was conducted to evaluate the effects of dietary supplementation with probiotics, essential oils and their combination on growth performance, serum biochemical parameters, antioxidant capacity, resistance against Aeromonas veronii, and intestinal histomorphology of Nile tilapia (Oreochromis niloticus). A total of 360 O. niloticus fingerlings were randomly assigned to four groups (3 replicates/ group; each replicate contains 30 fish) based on the different dietary treatments. The first group was fed a basal control diet (G1), the second group was fed a basal diet supplemented with 0.015% probiotic (Klu-zetar®) (G2), the third group was fed a basal diet with 0.015% essential oil (ACTIVO®) (G3), and the fourth group was fed a basal diet mixed with 0.015% Klu-zetar® and 0.015% ACTIVO®, (G4) for 6 weeks. At the end of the trial fish were intraperitoneally injected with pathogenic bacteria Aeromonas veronii and the fish mortality rate was recorded for 7 days post infection. Results: The results revealed that using probiotics and or essential oils in Nile tilapia diets improved growth performance, reduced oxidative stress, enhanced immunity, maintained intestinal integrity, and enhanced resistance to pathogenic infection (P ≤ 0.05). Conclusions: It is concluded that the use of probiotics and/ or essential oils enhance the overall outcomes of Nile tilapia, so it is highly recommended to be used in aquaculture management. [ABSTRACT FROM AUTHOR]

ABSTRACT The blackspotted croaker (Protonibea diacanthus) is among the highest‐valued commercial marine fish species in Bangladesh. Therefore, we assessed the stock status, economic significance, and market status of blackspotted croaker in the Bay of Bengal, Bangladesh. We estimated life history parameters and sustainability indicators to determine if the stock was being sustainably managed. Size of blackspotted croaker was significantly differ temporally. Blackspotted croaker increased in weight allometrically in relation to length. Length‐age life history parameters were L∞ = 161.16 cm, k = 0.39 year−1. Natural mortality M was 0.39 year−1 and fishing mortality F was 0.35 year−1. Catch composition and sustainably indicators revealed that the stock was prone to recruitment and growth overfishing. Medium to large sized blackspotted croaker (> 85 cm) fetched the highest price in commercial markets for the swim bladders that was worth many times more than the value of fillets. The highest demand of swim bladders in export commerce termed this species as marine gold to the fishers. Therefore, fishers were increasingly motivated to target the species. Ununiformed landing of blackspotted croaker, for domestic and international trade of swim bladder of blackspotted croaker, and poorly documented trading supply chains make this fishing industry luck‐driven. Management interventions are needed to sustain the fishery and economic value. [ABSTRACT FROM AUTHOR]

The Indian mackerel (Rastrelliger kanagurta) holds significant economic value in Indonesian fisheries. However, the continued increase in fishing activities may impact its population, leading to a decline. Therefore, studying the population dynamics and the spawning potential ratio (SPR) using a length-based data approach is essential to determine population parameters and to assess exploitation status. This research was conducted in 2021, with fish length measurements collected from mini purse seine vessels operating in the Aru Sea and landing their catches in Kaimana, West Papua, Indonesia. The results showed that the length distribution of the Indian mackerel ranged from 10 to 31.5cm fork length (cmFL), with a mode at 22.5 cmFL. The asymptotic length (L∞) was estimated at 33.08 cmFL per year, while the growth rate (K) was 0.8 per year. The natural mortality rate (M) was 1.55 per year, and the fishing mortality (F) was 1.04 per year, resulting in a total mortality rate (Z) of 2.59 per year. The exploitation rate (E) was 0.4. The exploitation level of the Indian mackerel in the Aru Sea is still moderate, indicating that increasing fishing effort or the number of fishing gears is still possible. The estimated length-based SPR (LB-SPR) was 57%. The spawning potential ratio of mackerel in the Aru Sea exceeds the minimum reference point, and the target reference point suggests that its exploitation is still sustainable. This indicates that further development efforts can be pursued. [ABSTRACT FROM AUTHOR]

Freshwater fish community surveys are an important component of aquatic ecosystem management. However, the standard method for taxonomic identification currently used for these surveys, wherein fishes are manually identified in the field by a taxonomic expert, has several shortcomings. These include handling-related fish injury and mortality, the need for a fish-identification expert to be present during field sampling, and additional fish mortality due to physical voucher collection. These shortcomings may be overcome using new methods such as environmental DNA (eDNA) or image analyses. While eDNA can provide fish community data through metabarcoding, it is costly and provides little ecological information. A novel, image-based method for taxonomic identification ("batch-image identification"), which addresses the shortcomings of standard and eDNA methods, was tested in this study. Fishes were captured in the field and photographed in small groups ("batches") within fish viewers for subsequent identification by taxonomic experts. Comparing taxonomist-based identifications from batch images to specimen-based identification, batch-image identification yielded an overall species-level correct-identification rate (CIR) of 49.7%, and an overall genus-level CIR of 61.2%. CIR increased with taxonomist expertise, reaching 83% when identification was performed by expert taxonomists. Batch-image identification data also produced rarefaction curves and fish-length measurements comparable to those obtained through standard methods. Potential methodological improvements to batch-image identification, including procedural adjustments and alternative identification methods, provide direction for the continued testing and improvement of this method. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the rates of natural mortality (M), fishing mortality (F), total mortality (Z), the exploitation rates (E), as well as the biological reference points (BRPs) and the annual removal rates (R) of the crocodile shark, Pseudocarcharias kamoharai, in the Ecuadorian Pacific. Thirty similar and different models were applied to determine all these rates. These equations were obtained from studies on teleost and chondrichthyan fish. The biological parameters, including age, growth, longevity, and reproduction, were obtained from the specialized literature based on the biology of P. kamoharai in Ecuadorian waters. These biological parameters were used in all the models considered here. The M estimations were 0.14 to 0.28 based on six models for chondrichthyans and osteichthyes. These values were similar to the six algorithms designed for cartilaginous fish, ranging from 0.16 to 0.35; for this reason, these mortality rates were considered low. The Z values ranged from 0.08 to 0.51; however, they were not considered given that the three estimations were less than M, and only the Z = 0.51 was considered. Given that Z = 0.51 and M = 0.24, an F = 0.27 was obtained by subtraction, indicating a low mortality by fishing. E had values between 0.21 and 0.53, which indicated overexploitation that exceeded the Eopt = 0.50 value. The obtained BRPs were Fopt = 0.10 and 0.12 and Flim = 0.16, which showed that the optimal fishing levels (best possible capture) to achieve long-term sustainable exploitation of the stock encompass 10 to 16% of the fishing effort applied for this species. However, the F surpassed this prudential range. The annual removal percentage (R = 21%) demonstrated that 21% of the population was being removed. Based on the biology and ecology of this species, all models applied in this study showed that P. kamoharai had low natural and fishing mortality rates and moderate total mortality; its exploitation rate exceeded the fishing limits. These values and their life history traits indicated that this shark species cannot tolerate any fishing level without threatening its populations. [ABSTRACT FROM AUTHOR]

In fisheries management, it is generally assumed that density-dependent processes are confined to the pre-recruit stage of a fish. Consequently, current calculations of fishing mortality reference points include density dependence (DD) solely in recruitment dynamics. However, several studies have reported the importance of DD in growth and natural mortality (M). In this study, we tested the effect of DD on estimates of fishing mortality producing maximum sustainable yields (F MSY), comparing these estimates to those resulting from constant growth and M. We simulated fish populations with a wide range of life-history traits (LHTs), applying either constant or density-dependent growth and M and derived F MSY for each stock. Results showed that including DD in growth and M led to higher F MSY and often also higher yield estimates (MSY). The effect of DD was found to be greater in growth than in M. Additionally, F MSY estimates derived from surplus production models fitted to generated stocks with density-dependent growth and/or M were generally closer to true F MSY, compared to those from age-based long-term predictions assuming constant growth and M. However, due to the inherent uncertainties in estimates of stock dynamics and biological reference points (BRPs), caution is suggested before implementing DD in F MSY calculations. Equilibrium yield curves relating production to stock size were right-skewed, shape parameters from production models were slightly below 1 for scenarios assuming constant growth and M , but declined to 0.5 with increasing DD. [ABSTRACT FROM AUTHOR]

Simple Summary: This study investigates the historical fluctuations in the Brazilian sardine (Sardinella brasiliensis) abundance and its impact on the purse seine fishery dynamics in southeast–south Brazil. Using an ECOPATH mass balance model, the trophic relationships and biomass importance between two fishery collapses, in 2000 and 2017, were analyzed. Following 2000, the fishery became multi-species. Mean trophic levels showed a decline until 2008, when more advanced vessels expanded the fishery grounds, increasing the trophic levels. However, by 2016, the fishery collapsed due to the high catches and natural mortality rates, a drop in primary production, and rising water temperatures, suggesting a detrimental cycle affecting the sardine stocks. The inter-annual fluctuations of abundance of the Brazilian sardine (Sardinella brasiliensis) during the last decades have deeply modified the purse seine fishery dynamics. This study evaluates the trophic relationships of the main species exploited by this fishery and the importance of its biomass for the southeast–south Brazil marine ecosystem (22° S–34° S). Data were analyzed using a mass balance model (ECOPATH) between the two fishery collapses: 2000 and 2017. From 2000 onwards, the sardine fishery adopted a multi-species character. The mean trophic level of the catches (MTL) showed a decreasing trend until 2008, when more modern vessels with greater autonomy entered the fishery, and expanded the traditional fishing area to exploit northern fishing grounds. The MTL in the expanded fishing area suddenly increased and was characterized by high biomass of the Brazilian sardine and other species with a high biomass and high ecotrophic impact, falling again to the lowest level in 2016. The model evidenced high estimates for fishing mortality, natural mortality, and flow to detritus between 2008 and 2016, when sardine fishing collapsed. During this period, a sharp drop in the primary production required to sustain the catches from 2012 onwards accompanied a significant fall in the biomass accumulation rate. This pattern was coincidental with the increasing mean temperature of the catches, which was probably acting as a limiting factor for the primary production, resulting in a higher natural mortality and flow to detritus. Furthermore, the higher fishing mortality may have led the stock to collapse. [ABSTRACT FROM AUTHOR]

The current work was conducted to investigate fisheries dynamics, rate of growth, and mortality, along with demographic features of Schizothorax niger using length-frequency data collected monthly from Manasbal Lake from August 2020 and July 2022. The length data for estimation was categorized into 13 bins, and population parameters were explored utilizing various options in ELEFAN I, with the best fit (Rn = 0.282) calculated by means of the FiSAT-II application. TW = 1.94 TL2.94, with a = − 1.94, b = 2.94, and an attuned r2 = 0.77 were derived for the weight and length association. The growing performance metric (ϕ) was calculated as 2.80. S. niger harvested stock in Manasbal Lake was prevalent in length categories of 20.5 to 25.4 and 25.5 to 30.4 cm. Different growth attributes were valued utilizing length frequency statistics as L∞ = 46.05 cm, k = 0.30/year, and t0 = − 0.493 years. Over all mortality (Z), natural mortality (M), and fishing mortality (F) coefficients were evaluated as 1.43 year−1, 0.56 year−1, and 0.87 year−1, respectively. The fish's average length was assessed at the culmination of the 1st, 2nd, 3rd, 4th, 5th, and 6th year as 15.42 cm, 22.78 cm, 28.09 cm, 32.61 cm, 36.03 cm, and 38.53 cm, respectively. Recruitment patterns in S. niger from Manasbal Lake indicate a singular annual recruitment occurrence, exclusively observed during the month of June. The current value of the exploitation (fish harvest) ratio (E) was 0.61 by the size-transformed catch curvature method, found to be marginally lower than the maximum value (Emax) of 0.699 depicting that the species is on the brink of overexploitation, and caution is required to maintain sustainability. The seasonal analysis of water quality parameters revealed that except for pH and free carbon dioxide, the other parameters showed pronounced temporal variations. Total alkalinity values were reflective of hard water type of the lake, and dissolved oxygen and free carbon dioxide values were reported to be suitable for S. niger. [ABSTRACT FROM AUTHOR]

Successful conservation of pinnipeds in the northwest Atlantic has led to increasing populations of harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus) in the Gulf of Maine. Within this region, habitat restoration and diadromous fish conservation in the Penobscot River have also been top priorities for the past decade. To understand the overlap between the regional recovery of pinnipeds and the aggregative response of pinnipeds to increasing forage fish, we assessed how counts, distribution, and behavior of seals in the Penobscot River Estuary have changed over time from 2012 to 2020 and determined whether those changes were related to changes in fish biomass that are occurring as the result of diadromous fish restoration. We did not see increased counts of hauled-out seals, but consistent with regional harbor seal phenology, hauled out seal counts were highest in late spring and declined throughout the summer and into the fall. The number of swimming harbor and gray seals, analyzed as a proxy for changes in behavior, showed a stronger annual trend with an increase throughout the study period. Fish biomass was negatively associated with total number of hauled out seals and swimming gray seals but positively associated with swimming harbor seals. We also documented the potential displacement of harbor seals when gray seals are present. Together, these results begin to provide insights into how regional conservation and local restoration efforts interact to affect multiple trophic levels in an ecosystem. Continued monitoring of predator-prey interactions, along with diet and movement studies, will further elucidate seal aggregative response to increasing prey species in this system and the potential impact of recovering predator populations on restored prey populations. Knowledge gained regarding pinniped response to increasing fish biomass has important implications for other systems with ongoing conservation measures that aim to improve habitat, decrease exploitation, or recover protected species. Studies like these can be critical for finding paths forward to reconcile the potentially competing objectives of marine mammal protection and fish restoration. [ABSTRACT FROM AUTHOR]

Saprolegniasis is one of the most dangerous fungal diseases of fish, causing significant mortality in fish hatcheries and young ones. The present study aimed to isolate and characterize the causative fungus from fingerlings of Pangasianodon hypophthalmus cultured intensively in freshwater cages in Indian reservoirs and to determine minimum inhibitory concentrations of different antifungal compounds against the fungal hyphae and zoospores. The fungal isolates grown on potato dextrose agar showed an abundance of gemmae, elongated mycelia, non-septate hyphae, primary zoospores, mature zoosporangia with numerous zoospores, cysts with bundles of long hairs and were further identified as Saprolegnia parasitica following PCR amplification and sequencing of internal transcribed spacer region. S. parasitica showed temperature-sensitive optimum growth in a narrow window of 12–24 ℃, which might drive its experimental pathogenesis as well as natural infections in the winter months. In vitro sensitivity testing established negligible inhibitory activity of fluconazole, boric acid, sodium thiosulfate, and potassium permanganate while clotrimazole arrested the spore and hyphal growths at 2 mgL-1 concentration suggesting potential of the imidazole antifungal in treating S. parasitica infection in fish. The present study will serve as the baseline information for developing therapeutic and management strategies for controlling saprolegniasis in the economically significant iridescent catfish. [ABSTRACT FROM AUTHOR]

ABSTRACT The minute intestinal trematode Centrocestus formosanus is a major problem that can be found in the gills of various fish species. This parasite can destroy the gill structure of fish, leading to increased fish morbidity and mortality rates. In this study, loop‐mediated isothermal amplification (LAMP) based on the internal transcript spacer 1 region combined with a lateral‐flow dipstick (LAMP‐LFD) assay was used to detect C. formosanus in goldfish, Carassius auratus. The results showed that LAMP‐LFD was specific to C. formosanus and had no cross‐amplification with other co‐infecting parasite species, close related parasite species or their hosts (both intermediate host and definitive host). The limit of detection is as low as one metacercaria per gill. In testing 40 goldfish gill samples, the LAMP‐LFD method showed 100% accuracy when compared to traditional morphological identification. This method can be used as a rapid diagnostic tool for C. formosanus detection to obtain epidemiological information for monitoring, controlling, and preventing outbreaks of this parasite. [ABSTRACT FROM AUTHOR]

This study aimed to elucidate the parasitic nematode infecting the bile ducts of striped catfish. A total of 1570 fish specimens, weighing between 400.5 and 899.1 g each, were examined. A parasitological analysis revealed that 607 fish samples were infected with nematodes, with typical clinical signs including swollen in both the common bile duct and gallbladder, several white cysts in the common bile ducts, and gallbladders exhibiting a dark green coloration. Examination of the common bile ducts in striped catfish revealed the presence of two distinct parasitic nematode morphotypes. Free-living nematodes were observed residing within the lumen, the central cavity, of the common bile duct. Additionally, larval nematodes were encapsulated within cysts lining the duct wall, suggesting a more chronic parasitic association. The infection rate of worms in the common bile duct was prevalent from November to April, with the most significant infection rate occurring in March (67.1%). The intensity of free-living nematode infection was the peak in March, with a mean of 6.7 ± 1.5 worm/gallbladder, and the peak level of larval nematode encapsulation was in November, with 9.4 ± 3.8 encysted larvae/common bile duct. The highest cumulative fish mortality rate was observed in February (2.1 ± 0.4%). Morphological analysis revealed the roundworms to be white and elongated with a slight narrowing at the mid-esophageal region. The mouth extended posteriorly towards the abdomen, and a well-developed, funnel-shaped esophagus was observed. Further analysis using 18S rRNA gene sequencing confirmed the identity of the parasite within the common bile duct of striped catfish as Cucullanus bourdini. [ABSTRACT FROM AUTHOR]

Introduction: The implementation of the 10-year fishing ban in the Yangtze River has provided a crucial opportunity for the recovery of rare and endangered diadromous species, such as Coilia nasus. Methods: In this study, we utilized electronic length–frequency analysis (ELEFAN) and length-based Bayesian biomass estimation (LBB) method to fit the body length data of C. nasus from the Yangtze River Estuary and its adjacent sea areas before and after the fishing ban (2019-2023), and the resource changes of C. nasus population were evaluated. Additionally, combined the catch production monitoring data from 2020 to 2022, we comprehensively analyzed the impact of the Yangtze River fishing ban on the recovery of C. nasus resources. Results: The results showed that: (1) The proportion of quantity, weight and occurrence frequency of C. nasus in catches showed a significant increasing trend year by year. (2) 4,994 C. nasus were caught from 2021–2023, with body lengths ranging from 13–410 mm. In 2023, the average body length and weight of C. nasus had increased by 39.93% and 133.89%, respectively, from those in 2021. (3) ELEFAN estimated that the growth parameters after fishing ban, including asymptotic length, growth coefficient, and the theoretical age at length zero, were determined to be 42.92 cm, 0.43 year-1, and -0.31 year, respectively. The total mortality rate, fishing mortality rate, and exploitation rate were determined to be 1.47 year-1, 0.79 year-1, and 0.54, respectively. (4) LBB estimated that the relative fishing mortality of C. nasus before the fishing ban increased from 1.22 in 2019 to 2.65 in 2020, while the relative biomass decreased from 0.34 to 0.22. After the fishing ban, the relative fishing mortality decreased from 0.85 in 2021 to 0.06 in 2023, and the relative biomass increased from 0.26 in 2021 to 0.90 in 2023, with a significant increase in 2022, indicating a clear recovery trend in C. nasus resources. Discussion: By quantifying the resource characteristics of C. nasus before and after the 10-year fishing ban on the Yangtze River, this research revealed the impact of the ban and provided a reference for future systematic evaluations of the C. nasus population. [ABSTRACT FROM AUTHOR]

ABSTRACT During spring 2024, a heat wave induced sustained water temperatures of 34°C during a week in Veracruz, Mexico. Serendipitously, we monitored Gyrodactylus cichlidarum infecting farmed tilapia fry during this pulse warming event and recorded a drastic decline of parasite populations over the following days. We subsequently established that parasites incubated in vitro at ca. 27°C survived up to 24 h, while at ca. 30°C and 34°C, all worms died within 4–7 h. Abnormal haptor structures were observed in parasites that developed and were born at a water temperature of 34°C. Under farming conditions, no unusual fish mortality was recorded, suggesting that pulse heat treatment may be an effective method to control G. cichlidarum, a recognised tilapia pathogen. [ABSTRACT FROM AUTHOR]

It is reported that the magnitudes of flood events in riverine systems have been increasing due to global climate change. Because flood events could displace fish species downstream and/or increase the mortality of fish, it is important to know how the increased floods can affect fish in river networks. In this study, we focused a hatchery-raised amphidromous fish, Ayu Plecoglossus altivelis altivelis in a mainstem-tributary network in Japan and examined the relative fish abundance changes before and after the recordable massive flood using the environmental DNA (eDNA) analysis. We also examined the spatiotemporal patterns of the Ayu eDNA concentrations and the relationships with tributary discharge, width, and depth to examine if the relative abundance changes could be related to tributary size. Our results indicated that Ayu tended to inhabit large, deep tributaries more than small, shallow tributaries even after the flood event. Further, the eDNA concentrations of Ayu have decreased in most study sites after the flood; however, the eDNA concentrations in certain tributaries with lower tributary size have increased during the study period. These results suggest that (1) the habitat conditions could be important for the maintenance of Ayu populations before and after flood events, (2) increase in flood magnitude along climate changes could have impacts on Ayu populations, and (3) not only large tributary, but also small tributaries could be important habitats for the target species to avoid flood disturbances. [ABSTRACT FROM AUTHOR]

In this study, we simulated water temperature changes under variable frequency temperature rise conditions caused by coastal nuclear power plant discharges and conducted thermal shock tests on four fish species: Trachinotus ovatus, Nibea albiflora, Larimichthys crocea, and Acanthopagrus schlegelii at acclimated water temperatures of 25.0°C and 27.5°C during the summer. The effects of these temperature variations on the thermal shock response of the four fish species were analyzed. The results indicated that at 25.0°C, the mortality rate of N. albiflora exhibited an overall upward trend with increasing temperature and duration frequency, with an average mortality rate ranging from 10±3.3% to 38.9±3.3%. For L. crocea, mortality was observed only in the 8.5°C-100% duration probability group, while other groups had a 0% mortality rate. At 27.5°C, A. schlegelii showed an average mortality rate of 10±3.3% at an 8.5°C-100% duration probability, with all other groups showing 100% survival. The average mortality rate of T. ovatus at 8.5°C-100% was 6.7±3.3%, with no mortality in the other treatment groups. The expression level of the hsp70 gene in the liver of N. albiflora increased with higher temperature rise amplitudes and longer frequency conversion durations. Similarly, the hsp70 gene expression in L. crocea and A. schlegelii increased with rising temperatures, though there were no significant differences among groups with varying frequency conversion times. In contrast, the hsp70 gene expression in T. ovatus remained relatively stable across temperature rise treatments, showing no significant differences with varying frequency conversion durations. The heat stress tolerance ranking among the four fish species was determined to be L. crocea > N. albiflora > T. ovatus > A. schlegelii. [ABSTRACT FROM AUTHOR]

Jinga shrimp (Metapenaeus affinis) is one of the most productive shrimp fisheries in Iraqi waters. The study aimed to evaluate the growth, mortality, recruitment, yield-per-recruit, and virtual population analysis (VPA) of the M. affinis shrimp in these Iraqi waters. Samples were collected from the nursery grounds of the species in east Hammar marsh and the fishing grounds in Iraqi marine waters between November 2022 to October 2023. A total of 8021 M. affinis ranged from 2.0 to 15.6 cm TL (0.6-6.0 cm CL) were examined. The length-weight relationship exhibited a positive allometric growth pattern. Total length-frequency data for combined sexes was analyzed using the FiSAT II software. The asymptotic length, growth coefficient and growth performance index were 16.3 cm, 0.92 and 2.388, respectively. Total, natural and fishing mortalities were 3.69, 1.82 and 1.87, respectively. The current exploitation rate (Ecur) was 0.51. Length at first capture (Lc50) was higher than at first maturity length (Lm50). Recruitment continued throughout the year, with one major peak in April. The analysis of relative yield per recruit and relative biomass per recruit indicated that the Ecur of the stock was equal to its optimal level (E0.1= 0.520) and below its maximum sustainable yield (Emax= 0.628). To effectively manage the M. affinis stock, it is essential to adjust the mesh size so that the total length of the species at first capture must not be less than the length at first maturity. Consequently, it may have a chance to breed, and the nursery grounds should be protected from illegal fishing. [ABSTRACT FROM AUTHOR]

The stock assessment model for the Antarctic krill fishery is a population model operating on daily timesteps, which permits modeling within‐year patterns of some population dynamics. We explored the effects of including within‐year patterns in natural and fishing mortality on catch limits of krill, by incorporating temporal presence of key predator species and contemporary temporal trends of the fishing fleet. We found that inclusion of within‐year variation in natural and fishing mortalities increased catch limits. Fishing mortality had a greater effect than natural mortality despite differences in top‐down predation on krill, and potentially increased catch limits by 24% compared to the baseline model. Additionally, the stock assessment model allowed a higher catch limit when fishing was during peak summer months than autumn. Number of days with active fishing was negatively related to precautionary catch limits. Future stock assessments should incorporate contemporary spatiotemporal fishing trends and consider implementing additional ecosystem components into the model. [ABSTRACT FROM AUTHOR]

Sinipercachuatsi rhabdovirus (SCRV) has caused severe disease and mortality in commercial fish in China. To investigate the molecular relationships between pathogen and host, transcriptome analysis of SCRV-infected and non-infected E11 cells was obtained using the Illumina HiSeq X Ten sequencing system. A total of 29,894 unigenes were assembled and a total of 4137 differentially expressed genes (DEGs), consisting of 2189 up-regulated and 1948 down-regulated unigenes, were detected between SCRV-infected and non-infected E11 cells. To understand the immune response of the host against the virus, pathway function analysis indicates that SCRV infection affected 31 typical immune-related pathways, including MAPK signaling pathway, PI3K-Akt signaling pathway, endocytosis, and apoptosis, suggesting that E11 cells resist SCRV invasion through these innate immune pathways. Overall, qRT-PCR results showed similar expression to Illumina HiSeq, with reliable sequencing results. These results provided some vital clues which will be helpful for future study on SCRV-host interactions. [ABSTRACT FROM AUTHOR]

Simple Summary: A comprehensive assessment of the life history parameters of the invasive Atlantic blue crab Callinectes sapidus in the Lesina Lagoon (Adriatic Sea, SE Italy) in terms of abundance, sex ratio, size–frequency distribution, morphological maturation, growth, and mortality was provided adopting a suite of analytical techniques. The results of the present study can provide a valuable knowledge basis for future comparative investigations on the fishery biology of C. sapidus in Mediterranean waters. The fishery biology of the invasive Atlantic blue crab Callinectes sapidus in the Mediterranean Sea outside the eastern sectors of the basin has been only recently investigated. Here we studied the population of C. sapidus in the Lesina Lagoon (Adriatic Sea, SE Italy). In total, 838 crabs were captured monthly between February 2021 and January 2022 using fyke nets. Abundances varied seasonally with catches per unit effort ranging between 0 and 1.76 crabs fyke nets−1 d−1 in winter and summer. Spatial abundances estimated in summer by a Carle–Strub procedure ranged between 0.06 and 0.64 crabs m−2. The sex ratio (♂/♀) was close to 1:1; males prevailed only in August and September; ovigerous females occurred from April to August. The males' size at morphological maturity was smaller than females (110.6–112.3 mm vs. 122.1–123.1 mm). Seasonal von Bertalanffy growth parameters indicated that, compared with males, females showed a shorter maximum lifespan (5 vs. 8 years), a higher growth coefficient K (0.6 vs. 0.4 y−1) and growth performance index Ф' (4.6 vs. 4.3), while maximum sizes CW∞ (237.8 vs. 232.6 mm) and seasonality indices C (0.62 vs. 0.57) were similar. Furthermore, females showed higher natural and fishing mortalities and exploitation rate. We discussed the results of the present study in the context of the available literature to provide a valuable basis for the implementation of standardized Mediterranean-scale management plans, matching exploitation of C. sapidus with sustainable conservation of coastal ecosystems. [ABSTRACT FROM AUTHOR]

Objective: Gray Snapper Lutjanus griseus constitute a significant recreational fishery and minor commercial fishery throughout the Gulf of Mexico. The overall stock appears healthy based on the results of the most recent assessment; in fact, shifting climate conditions have led to range expansions and subsequent population growth in the north‐central Gulf of Mexico, a region for which the full suite of basic biological data is currently lacking for this species. This work presents the results of a comprehensive study on the age, growth, maturity, and mortality of Gray Snapper in Alabama and Mississippi waters. Methods: From 2011 to 2021, otoliths (n = 886) and gonads (n = 364) were sampled and processed according to standard microscopic techniques. Age data were used to fit three separate growth functions and derive estimates of total, natural, and fishing mortality, while testes and ovaries were categorized by reproductive phase to determine maturity at length and age. Result: Ages ranged from 0 to 27 years, representing one of the most comprehensive collections across published studies to date. Sex‐specific growth curves constructed using the von Bertalanffy growth function were preferred over the Gompertz and logistic models based on Akaike information criterion and suggest that males reach a higher mean asymptotic length Lt=731.521−e−0.15t+1.34$$ \left({L}_t=731.52\left[1-{e}^{-0.15\left\{t+1.34\right\}}\right]\right) $$ than females Lt=704.281−e−0.14t+1.62$$ \left({L}_t=704.28\left[1-{e}^{-0.14\left\{t+1.62\right\}}\right]\right) $$. Based on histological analyses, we estimate total length at 50% maturity to be 181 mm for males and 273 mm for females and total length at 90% maturity to be 215 mm for males and 354 mm for females. We estimate the age at 50% maturity to be <1.0 year for males and 2.0 years for females and the age at 90% maturity to be 1.4 years for males and 3.6 years for females. Mortality rates calculated using preferred estimators (Z = 0.30–0.38; M = 0.26; F = 0.04–0.12) indicate relatively low levels of exploitation in the north‐central Gulf of Mexico, with full recruitment to the fishery occurring at age 4. Conclusion: Based on these results, the Gray Snapper population in the north‐central Gulf of Mexico is characterized by a relatively unexploited age structure with moderate longevity that has been subject to minimal fishing pressure. The findings from this study introduce new regional data for incorporation into assessments and provide an informed basis for future management decisions in this fishery. Impact StatementInvestigations into the life history of Gray Snapper in the Mississippi Bight (Alabama and Mississippi coastal waters) fill important regional gaps in various biological parameters, supplementing estimates from recent Gulf of Mexico stock assessments. The environment in this region is likely changing and becoming more suitable for Gray Snapper. [ABSTRACT FROM AUTHOR]

Objective: Francisella orientalis is a bacterial pathogen that is responsible for substantial mortalities in warmwater fish, such as tilapia, and has negatively impacted the aquaculture industry globally. Starting in the mid‐1990s, periodic F. orientalis outbreaks in Hawai'i led to severe mortalities in cultured and feral tilapia populations on Oahu. In an attempt to limit the outbreak's impact on tilapia aquaculture in Hawai'i, the Hawai'i Department of Agriculture Plant Quarantine Division issued a moratorium on the export of tilapia from Oahu to the other Hawaiian Islands. Despite reported high incidences of F. orientalis from cultured tilapia on Oahu and from around the world, the moratorium continues to remain in effect to this day. Methods: To assess the prevalence of F. orientalis in feral tilapia populations across the Hawaiian Islands, tilapia were collected from streams on Kauai, Oahu, Maui, Moloka'i, and the Big Island (Hawai'i) and were screened using a combination of molecular, bacteriological, and histological techniques. Result: Although signs of infection (i.e., granulomas) were observed in fish on all five islands, molecular screening using quantitative polymerase chain reaction only detected the presence of F. orientalis on the islands of Oahu, Maui, and Kauai. Conclusion: These findings suggest that F. orientalis is prevalent in feral tilapia populations across the Hawaiian Islands. Impact StatementEvidence of Francisella orientalis in multiple species and hybrids of wild tilapia populations from the Hawaiian Islands renders the 1998 moratorium on tilapia exportation by Oahu producers no longer necessary, and the moratorium should be revoked. [ABSTRACT FROM AUTHOR]

Copyright of Basrah Journal of Veterinary Research is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fishery stock assessment is the basis of fishery management. This study explored the applicability of the Length-Based Spawning Potential Ratio method (LBSPR) to assess the exploitation status of data-limited fisheries. Using data from bottom trawl surveys in Zhanjiang Bay, the study estimated the relative fishing mortality (F/M) of Johnius belangerii stock. The results showed that the average lengths at 50% and 95% selectivity (LS50 and LS95) were 105 mm and 145 mm, respectively, both of which are smaller than the lengths at 50% and 95% sexual maturity length (L50 = 125 mm and L95 = 167 mm) determined via the logistic curve. The estimated spawning potential ratio (SPR) was 0.15 significantly below the reference threshold of 0.2. The study recommended the establishment of a minimum size range (137 to 150 mm) length for harvesting Johnius belangerii to enhance their reproductive potential. It also emphasized the importance of scientific monitoring of fishery resources and the ecological environment in Zhanjiang Bay to ensure sustainable management. [ABSTRACT FROM AUTHOR]

ABSTRACT The Atlantic surfclam, Spisula solidissima supports a lucrative commercial fishery in the Mid‐Atlantic Bight (MAB) worth roughly $30 million in revenue per year. Rapid climate change is expected to modify the geographic range of the Atlantic surfclam, with consequences for the surfclam fishery. This study evaluated fishery‐based indicators projected from 2020 through 2095 based on anticipated changes in the geographic range and biomass of the Atlantic surfclam, using a Spatially Explicit, agent‐based Fisheries and Economics Simulator (SEFES). Simulations generally showed a positive trend in Atlantic surfclam biomass throughout the next three‐quarters of the 21st century as the clam's range continues to shift offshore and northward along the continental shelf. A general decrease in fishing mortality rate is projected given the present fleet capacity, with a simultaneous increase in catch and landings per unit effort (LPUE), signaling future potential growth in the surfclam fishery. Regionally, forecasts show biomass expanding into deeper waters particularly off New Jersey, Long Island, and southern New England starting in the early 2050s, whereas populations on Georges Bank and off Delmarva gradually decline. Trends in time spent fishing, catch, and LPUE parallel those of biomass in each region. These results can inform managers and business interests that rely on this fishery, as well as other users of the continental shelf, to provide a basis for the development of anticipatory management for the socio‐ecological and economic impacts that may result from future changes in the Atlantic surfclam range and carrying capacity consequent of climate change. [ABSTRACT FROM AUTHOR]

Featured Application: Machine learning model applications provide enough evidence to predict fish stock using aquaculture data, allowing for significant practical implications. By applying advanced statistical models, including Random Forest, Decision Tree, and Linear Regression, aquaculture stakeholders can improve their decision-making processes by predicting fish populations, mortality rates, and other critical metrics. Among the predictive models, the Random Forest model outperformed other models, reaching the highest accuracy. This allows more efficient and productive management strategies, supports sustainable development, and helps policymakers in enhancing decision-making to protect marine ecosystems. The dynamic for integrating such tools, such as predictive statistical models into real-time monitoring systems, provides a proactive strategy for aquaculture growth, risk mitigation, and long-term sustainability. The current study evaluates the performance of three machine learning models—Decision Trees, Random Forest, and Linear Regression—applied to aquaculture data to mitigate risks in aquaculture management. The performances of these models are analyzed and properly demonstrated using metrics including the Mean Squared Error (MSE), R-squared (R2), Root Mean Squared Error (RMSE), and Concordance Index (C-index). The Random Forest model achieved the highest prediction accuracy among all machine learning models, followed by Linear Regression and the Decision Trees. The scatter plot for Linear Regression demonstrates good predictive accuracy for mid-range values. However, it shows significant deviations at the extremes, indicating that the model struggles to capture the full range of variability in the data. The bar chart of coefficients pinpoints the variables with the greatest impact on the predictions, providing suggestions for potential areas that can be improved and providing model interpretability. Future work could incorporate more predictive statistics models focusing on improving the models for extreme values by assessing non-linear models, feature engineering methods, and expanding research into less influential variables. The results greatly impact several sections, including aquaculture management, policy-making, and operational strategies, providing valuable insights for stakeholders and decision-makers. Apache Spark was used for data processing and machine learning model implementation; Apache Cassandra was also used for data storage, ensuring efficient large dataset management and SQL tools for structured data handling; Oracle VM VirtualBox for cross-platform virtualization; and Spark Connector was also used. [ABSTRACT FROM AUTHOR]

Large high-head centrifugal pumps have the characteristics of large flow rate, high head, and high specific speed, making them important engineering equipment in large-scale water transfer projects. However, these pumps inevitably cause the death of a large number of fish during operation, which has adverse effects on the ecological environment. Therefore, studying the damage of large high-head centrifugal pump stations on fish is of great significance. This article establishes a new mathematical model for blade strike and predicts the strike probability and mortality rate of fish passing through the inlet of the centrifugal pump impeller. The prediction results show that under various flow conditions, the strike mortality rate for 50 mm fish passing through the model pump exceeds 82.5%, indicating that the model pump will cause significant damage to the pumped fish. This article further investigates the damage to fish caused by unstable flow inside the impeller and diffuser in low-pressure, high-shear, and high-pressure gradient regions. The research results show that fish suffer less low-pressure damage and more high-pressure gradient damage while passing through the model pump. [ABSTRACT FROM AUTHOR]

Assessing the skipjack tuna (Katsuwonus pelamis) stock is a crucial step in understanding the population dynamics, distribution, and fishing potential in these waters. Given the increasing exploitation pressure in the North Buru waters, studies on the assessment of skipjack tuna stock in various regions are becoming increasingly important. The objective of this study was to conduct a detailed analysis of the skipjack tuna stock in the Maluku waters. The monthly data collected included the length of skipjack tuna from January to November 2022. The data was analyzed using FiSAT II software, revealing a total catch of 3728 individuals with lengths ranging from 25 to 97 cm. Skipjack tuna recruitment (Katsuwonus Pelamis) was observed in June, with a total mortality rate (Z) and fishing mortality rate (F) of 2.52 and 1.67 per year, respectively, and an exploitation rate (E) of 0.66 (E>0.5), indicating that it exceeds sustainable potential (over-exploited). In conclusion, it is recommended that the exploitation rate be restricted to maintain the skipjack tuna resources in the North Buru waters. [ABSTRACT FROM AUTHOR]

Home range size is a fundamental trait that can affect the probability of fish being harvested and, at the same time, may be affected by fishing. The relationship between home range size and fishing will impact the effectiveness of fully protected areas (FPAs), as it will influence the number of fish moving into fished areas, affecting both spillover and edge effects. One hypothesis is that individuals within FPAs will present reduced home range size relative to individuals in fished areas. This pattern can be driven by demographic selection (e.g. fishing of individuals with large home ranges leaving the FPAs), improved habitat requiring less foraging movements, or behavioural changes associated with reduced fishing threats. To test the relationship between home range size and protection, we compiled 1143 individual‐level home range sizes based on acoustic tracking, covering 17 species from 11 FPAs in 7 countries, with information on distance from FPA borders. A dichotomic analysis (in/out of FPAs) did not support a significant change in the home range size between FPAs and fished areas. However, continuous analysis across the FPA borders demonstrated reduced home range size within the FPAs. We did not find an effect of FPA age or size on this pattern. While we cannot pinpoint the underlying mechanism for the pattern revealed, we suggest behavioural changes as the main driver for reduced home range within FPAs. This mechanism will lead to more resident populations within FPAs, reducing fishing mortality within FPAs yet limiting spillover benefits to adjacent fisheries. [ABSTRACT FROM AUTHOR]

Simple Summary: Streptococcus agalactiae, a significant pathogen affecting humans and aquatic species, is causing high morbidity and mortality in fish, particularly Nile tilapia (Oreochromis niloticus). This study focuses on S. agalactiae infection in cultured O. niloticus, examining transmission, sources, risk factors, clinical signs, pathogenesis, virulence factors, and methods for diagnosis, treatment, control, and prevention. Streptococcus agalactiae (Group B Lancefield) has emerged as a significant pathogen affecting both humans and animals, including aquatic species. Infections caused by S. agalactiae are becoming a growing concern in aquaculture and have been reported globally in various freshwater and marine fish species, particularly those inhabiting warm water environments. This has led to numerous outbreaks with high morbidity and mortality in fish. Nile tilapia (Oreochromis niloticus), a member of the Cichlid family, is one of the severely affected fish species by S. agalactiae. The current study aims to focus on S. agalactiae infection in cultured O. niloticus with reference to its transmission and sources of infection; risk factors influencing GBS infection, disease clinical signs, lesions, and pathogenesis; S. agalactiae virulence factors; and how to diagnose, treat, control, and prevent infection including vaccination and herbal extract medication. [ABSTRACT FROM AUTHOR]

A 2-week rapid fishery assessment using various sampling gears was conducted to collect life-history data on rednose labeo Labeo rosae and Mozambique tilapia Oreochromis mossambicus in Loskop Dam on the Olifants River, Mpumalanga Province, South Africa. These native species were the two most-abundant fish species caught in the impoundment during the study. Both species displayed a bimodal population size distribution comprised of recent recruits and large-sized individuals. Isometric growth (b value ∼3), an asymptotic length (L∞) of 447 mm, and length at 50% sexual maturity (Lm50) of 198 mm were estimated for L. rosae. Isometric growth, L∞ of 451 mm, and Lm50 of 124 mm were estimated for O. mossambicus. This rapid assessment at Loskop Dam produced sets of life-history parameters comparable to those previously reported for these two species in Flag Boshielo Dam, ∼80 km downstream. [ABSTRACT FROM AUTHOR]

Background/Objectives: Maintaining an optimum transport density is essential for protecting water quality, lowering stress levels, and increasing fish survival rates. Transporting marine fish fry involves major dangers. The purpose of this study was to evaluate the impact of transport stress at varying densities on the immune-related gene expression, antioxidant capacity, and survival rate of yellowfin seabream (Acanthopagrus latus) fry. Methods: A 12 h simulated transport experiment was conducted with A. latus fry divided into six density groups. For 1–2 cm fry, densities of 900, 1200, and 1500 fry per pouch were used to assess antioxidant enzyme activity; and for 4–5 cm fry, densities of 100, 125, and 150 fry per pouch were used for gene expression analysis. The key parameters measured included survival rates, antioxidant enzyme activities in liver and intestinal tissues, and expression levels of HSP90α and caspase-3 genes. Results: The findings showed that recovery time and density both affected the observed responses and that transport density had a substantial effect on antioxidant enzyme activity in all tissues. The intestinal and liver tissues showed a considerable decrease in antioxidant enzyme activity, suggesting that these tissues may be able to respond to oxidative stress. Moreover, under high-density transport conditions, there were notable increases in the expression of caspase-3 and HSP90α, suggesting the activation of immune response systems. This research offers valuable new understandings into the relationship between transport density and immunological and antioxidant modulation in A. latus fry. Conclusions: The results provide a scientific foundation for enhancing aquaculture transport conditions, which will ultimately lead to decreased fish mortality and improved general health during transit, resulting in more sustainable and effective aquaculture methods. [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fish diseases are among the major limiting factors to increase global aquaculture production. They lead to increased fish mortality, low breeding and growth rates, and low meat quality. The success of aquaculture is heavily dependent on the timely identification of disease. Therefore, we propose a fuzzy U-Net model to automatically identify fish disease from underwater images. U-Net is enhanced with multi-head channel and spatial attention and used to segment infected fish regions from fish disease images. Color pixel intensity features are then extracted from the localized regions, a form of guided feature extraction. Fuzzy C-means clustering is then used to find the cluster centroids and data distribution within the clusters, for the design of fuzzy membership functions. Moreover, the number of clusters are determined by silhouette score. Adaptive neuro-fuzzy inference system (ANFIS) is then trained, tested, and cross-validated for fish disease identification. The model parameters are optimized using particle swarm optimization (PSO) algorithm and compared with gradient-based methods. For image segmentation, the enhanced U-Net achieved a mean intersection over union (IoU) of 86.29%, mean pixel accuracy of 90.94%, mean precision of 93.58%, and mean recall value of 89.94% on 42 test images. Subsequently, ANFIS with PSO achieved overall superior performance on fish disease identification over gradient-based methods, with accuracy of 99.31%, precision of 99.00%, recall of 99.00%, and F1-score of 99.00%. The high-performance results of the optimized ANFIS confirm the robustness and efficacy of the proposed method to automatically identify fish diseases in aquaculture. [ABSTRACT FROM AUTHOR]

Water temperature is a critical factor for aquatic ecosystems, influencing both chemical and biological processes, such as fish growth and mortality; consequently, river and lake ecosystems are sensitive to climate change (CC). Currently proposed CC scenarios indicate that air temperature for the Mediterranean Jucar River will increase higher in summer, 4.7 °C (SSP5-8.5), resulting in a river water temperature increase in the hotter month; July, 2.8 °C (SSP5-8.5). This will have an impact on ecosystems, significantly reducing, fragmenting, or even eliminating natural cold-water species habitats, such as common trout. This study consists of developing a simulated model that relates the temperature of the river with the shadow generated by the riverside vegetation. The model input data are air temperature, solar radiation, and river depth. The model proposed only has one parameter, the shadow river percentage. The model was calibrated in a representative stretch of the Mediterranean river, obtaining a 0.93 Nash–Sutcliffe efficiency coefficient (NSE) that indicates a very good model fit, a 0.90 Kling–Gupta efficiency index (KGE), and a relative bias of 0.04. The model was also validated on two other stretches of the same river. The results show that each 10% increase in the number of shadows can reduce the river water temperature by 1.2 °C and, in the stretch applied, increasing shadows from the current status of 62% to 76–87% can compensate for the air temperature increase by CC. Generating shaded areas in river restorations will be one of the main measures to compensate for the rise in water temperature due to climate change. [ABSTRACT FROM AUTHOR]

Fisheries management needs to ensure that resources are exploited sustainably and the risk of depletion is at an acceptable level. In developing countries, multi-gear, multispecies fisheries often lack data, making conventional stock assessment approaches unsuitable. Data-limited methods have been developed to compare quantitative measures of fishery and stock status with management and biological reference points. In Morocco, despite its large productive ecosystems, most of the fishing stocks remain unassessed.Weselected a stock of chub mackerel, considering the availability of survey data, and the fact that it occupies an important place in small pelagic resources. Although this is an important stock, there is a lack of new information on migration and possible exchange between the two stocks of chub mackerel (central and southern). This study presents the first attempt at a combined assessment to provide Maximum Sustainable Yield (MSY) estimates and related indicators of the Moroccan chub mackerel (center and south) by using two of the most used data-limited approaches, the Stochastic Surplus Production model in Continuous Time (SPiCT) and the Length Based Spawning Potential Ratio estimation (LBSPR).Thesetwoapproacheswereappliedtoanalyze thechubmackerel stock state and estimate how far away it was from the estimated harvest relative to MSY using all available time series data. The findings provide valuable informationonMSY advice for this stock while remarking the advantages and limitations of two data-limited approaches for the assessment of chub mackerel. The SPiCT results show that the current harvest level closely aligns with the estimated MSY, and that the estimated biomass (B) is below BMSY, and the estimated fishing mortality (F) exceeds FMSY. For LBSPR, most SPR values are lower than the reference point of 40%, which serves as a proxy for BMSY, indicating also a biomass below BMSY. Both models suggest full to overexploited stock status mainly for the period (2016-2020), and this is a different perception to the one provided only by analyzing survey indices fluctuations that indicate critical status over a longer period. Then, this exercise is also pointing out the importance of having different data sources for a better stock status estimation. [ABSTRACT FROM AUTHOR]

Risk and uncertainty are intrinsic characteristics of natural resources that must be taken into account in their management. Harvest control rules (HCR) used to be the central management tool to control stock fisheries in an uncertain context. A typical HCR determines fishing mortality as a linear relationship of the biomass binding only when the biomass is above a critical risk value. Choosing the linear relationship and the risk value is a complex task when there is uncertainty because it requires a high level of data and an in-deep knowledge of the stock. This paper fully characterizes robust HCRs that explicitly include scientific uncertainty using the robust control theory approach. Our theoretical findings show that under uncertainty: i) Constant HCRs are not robust; ii) Robust HCRs show a steeper linear relationship between fishing mortality and biomass and a higher value of biomass to be consider at risk than non-robust HCRs. From the implementation viewpoint, we assume a three-sigma rule and show that robustness is achieved by selecting a fishingmortality such that its deviation fromthe fishingmortality target is twice the deviation of the biomass from the biomass target, and the critical value of the biomass (the point below which fishing should cease, or become as close to zero as possible) is half of the biomass associated with the maximum sustainable yield when this is the target. [ABSTRACT FROM AUTHOR]

One of the most farmed fishes is the African catfish, Clarias gariepinus. Its production has increased by 20% annually on average during the last 20 years, but the occurrence of fish diseases, especially bacterial such as Aeromonas hydrophila infections, is hindering its activities. Also, the incorporation of plant‐derived substances in aquafeeds is limited since they frequently contain different antinutritional factors, like nonstarch polysaccharides (NSPs). However, supplementing fish diets with β‐mannanase could increase growth, antioxidants, and immunity. Despite the advantage of β‐mannanase, its effects on growth, digestive enzymes, antioxidants, and immunity in African catfish need to be elucidated. This study examined the effects of dietary β‐mannanase on the growth performance, liver enzymes, antioxidant profiles, immunity, and protection of African catfish, C. gariepinus, against A. hydrophila infection. Five isonitrogenous diets were prepared to have 400 g/kg crude protein and supplemented with β‐mannanase at 0, 1500, 3000, 4500, or 6000 thermostable endo, 1,4‐β‐mannanase units (TMUs)/kg diet and fed to 300 juveniles of the African catfish, C. gariepinus (mean weight 12.1 ± 0.1 g) for 12 weeks. Then, 10 fish from each tank received an intraperitoneal injection of 0.1 mL of A. hydrophila (5.0 × 105 CFU/mL) and observed for 14 days. Results showed dietary β‐mannanase levels considerably improved growth performance but did not affect fish survival. Also, amylase, protease, and lipase levels were significantly promoted in the fish fed with β‐mannanase‐fortified diets than the control group (p < 0.05). Enhanced gut villi and intestinal absorption areas, haematlogical profiles, and liver enzymes but reduced gut viscosity were observed in fish‐fed β‐mannanase‐fortified diets (p < 0.05). In a dose‐dependent order, including β‐mannanase in the meals of African catfish raised the levels of glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione‐S‐transferase (GST), and glutamate cysteine ligase (GCL) activities and decreased the malondialdehyde (MDA) values in African catfish (p < 0.05). Also, fish immunity was greatly (p < 0.05) enhanced due to supplementation of the diet with β‐mannanase. In addition, fish‐fed diets comprising 6000 TMU β‐mannanase/kg diet showed the lowest rates of fish mortality (7.5%) (p < 0.05). Therefore, feeding African catfish, Clarias gariepinus, β‐mannanase enhanced growth performance, increased activity of digestive enzymes, gut morphology, enhanced generation of short‐chain fatty acids, digesta potential of hydrogen (pH), and improved antioxidant profiles and immunity at the optimum dose of 5800 TMU/kg diet. Additionally, β‐mannanase protected African catfish against A. hydrophila infection. [ABSTRACT FROM AUTHOR]

The growth of animal aquaculture requires ever more feed. Yet, fish and crustacean farming is argued to be sustainable because wild fish use is low and has improved over time. Here, accounting for trimmings and by-products from wild fish in aquaculture feed, and using four different sources of industry-reported feed composition data, we find ratios of fish inputs to farmed outputs of 0.36 to 1.15--27 to 307% higher than a previous estimate of 0.28. Furthermore, a metric that incorporates wild fish mortality during capture and excludes unfed systems raises the wild fish mortality-to-farmed fish output ratio to 0.57 to 1.78. We also evaluate terrestrial ingredients in aquaculture feeds. Widely cited estimates of declines in wild fish use from 1997 to 2017 entailed a trade-off of more than fivefold increase in feed crops over the same period. Our assessment challenges the sustainability of fed aquaculture and its role in food security. [ABSTRACT FROM AUTHOR]

Background: Streptococcus agalactiae (Group B streptococcus, GBS) induces a serious infection that can harm not only aquatic life but also humans and other animals. In a fish farm in southern Egypt, Nile tilapia (Oreochromis niloticus) has developed an epidemic with clinical symptoms resembling piscine streptococcosis. Results: Initial microscopic inspection of the affected fish brain and kidney indicated the presence of Gram-positive cocci. S. agalactiae was effectively isolated and identified using nucleotide homology of the 16S rRNA and species-specific PCR. The partial 16S rRNA sequence was deposited in the GenBank database at the NCBI and given the accession number MW599202. Genotyping using RAPD analysis indicated that the isolates in the present study belonged to the same genotypes and had the same origin. The challenge test, via immersion (9.2 × 107, 9.2 × 106, and 9.2 × 105 CFU/ml for 1 h) or intraperitoneal injection (4.6 × 107, 4.6 × 106, and 4.6 × 105 CFU/fish), elicited clinical symptoms resembling those of naturally infected fish with a mortality rate as high as 80%. The ability to create a biofilm as one of the pathogen virulence factors was verified. Zinc oxide nanoparticles and the ethanolic leaf extracts of nine medicinal plants demonstrated considerable antibacterial activities against the tested S. agalactiae strain with low minimum bactericidal concentrations (MBC) and minimum inhibitory concentrations (MIC). The ethanolic leaf extracts from Lantana camara and Aberia caffra showed potent antibacterial activity with MBC values of 0.24 and 0.485 mg/ml, and MIC values of 0.12 & 0.24 mg/ml, respectively. Conclusion: This study isolated S. agalactiae from O. niloticus mortalities in a fish farm in Assiut, Egypt. The pathogen persists in fish environments and can escape through biofilm formation, suggesting it cannot be easily eliminated. However, promising findings were obtained with in vitro control employing zinc oxide nanoparticles and medicinal plant extracts. Nevertheless further in vivo research is needed. [ABSTRACT FROM AUTHOR]

Simple Summary: The cultivation of the Pacific fat sleeper (Dormitator latifrons) is of commercial interest in the Eastern Central Pacific. Its domestication potential is affected by the presence of pathogens. This study aimed to identify two trichodinid ectoparasites that are associated with D. latifrons larval mortality. We evaluated a total of 4320 fish larvae, 1080 fish larvae per treatment, revealing the presence of T. acuta and T. compacta in one treatment. Larval mortality in the infected treatment reached up to 58% by the fourth day post-hatching, at 28 °C, due to Trichodina infestation, resulting in significantly lower survival in the infected tanks compared to the uninfected tanks. This is the first geographical record of these protozoan parasites in a species that is native to the East Central Pacific Basin and intended for culture. Trichodinidae, a prevalent group of protozoan ectoparasites in aquaculture, cause rapid mortality in fish hatcheries. Despite their significance, knowledge about these parasites in farmed fish in South America, especially in native species that are currently being domesticated for aquaculture, remains limited. This study morphologically characterized the Trichodinid species that are infecting Pacific fat sleeper (Dormitator latifrons) larvae and evaluated their impact on larval rearing. Four pairs of broodstock were induced with GnRHA implants and placed in tanks containing 200 L of freshwater, with a water temperature of 28 ± 1.0 °C and a dissolved oxygen level of 4.00 ± 1.23 mg L−1, with partial water exchanges being performed daily. The larvae hatched 7 to 8 h after fertilization and were transferred to tanks containing water with the same quality parameters. Twelve hours post-hatching, the presence of Trichodina was observed. Every 24 h, 60 larvae per tank (n = 180 per treatment) were sedated, and larval wet mounts were prepared, air-dried at room temperature, and impregnated with silver nitrate. Infection parameters and daily mortality were calculated. Trichodina was observed to parasitize the pelvic fins, caudal fins, and heads of fish larvae, which showed lethargy and erratic swimming movements. The Trichodina species showed a daily increase in the infection parameters, and a 58% rate of larval mortality was observed at the fourth day post-hatching (dph) in the infected tanks. In captivity, D. latifrons larvae typically survive up to 7 days post-hatching (dph) before reaching their point of no return due to the lack of adequate diet and feeding regimes. However, our study indicates that Trichodina infestation accelerates mortality, causing infected larvae to die more quickly than uninfected ones. [ABSTRACT FROM AUTHOR]