Search

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]

ABSTRACT Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD), is one of the leading pathogens in rainbow trout (Oncorhynchus mykiss) aquaculture. To date, there is little knowledge of the transmission kinetics of F. psychrophilum over the course of infection. In particular, how transmission is affected by host genotype and pathogen exposure dosage are not well studied. In order to fill in these knowledge gaps, we exposed two divergently selected lines of rainbow trout (ARS‐Fp‐R and ARS‐Fp‐S) to a range of dosages of F. psychrophilum (strain CSF117‐10). We then measured mortality and bacterial shedding to estimate transmission risk at multiple time points since initial infection. As dosage increased, the number of fish shedding and the amount of bacteria shed increased ranging from 0% to 100% and 103 to 108 cells fish−1 h−1, respectively. In addition, we found that disease resistance (survival) was not correlated with transmission risk blocking, in that 67% of fish which shed bacteria experienced no clinical disease. In general, fish mortality began on Day 3, peaked between Days 5–7 and was higher in the ARS‐Fp‐R line. Results from this study could be used to develop epidemiological models and improve disease management, particularly in the context of aquaculture and selective breeding. [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. We selected 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). These two approaches were applied to analyze the chubmackerel 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]

Water diversions that support agricultural and municipal use result in fish mortality through entrainment and impingement. Additionally, this infrastructure may attract both predators and prey fishes, thereby increasing predation rates and prey mortality near these anthropogenic contact points. The Sacramento–San Joaquin Delta (the Delta) in California's Central Valley is a tidal freshwater ecosystem that exports large volumes of water for municipal and agricultural use while at the same time providing valuable migratory and rearing habitat for imperilled fishes. Emigrating juvenile salmonids experience high mortality in the Delta, with predation by non‐native fishes contributing substantially.Therefore, this study had three main objectives. First, we determined if small water diversions aggregated piscivorous fishes like other similar structures in freshwater ecosystems. Second, we determined how small diversions may influence juvenile salmon predation risk in conjunction with other known predation risk factors (e.g. predator abundance, temperature and depth). Third, we assessed the predator assemblage, abundance and distribution to determine the likely predator composition in objectives one and two.Throughout the spring of 2021, we used ARIS (adaptive resolution imaging sonar; Sound Metrics) sonars to compare piscivore abundance at 30 water diversions in the north Delta to shorelines adjacent to diversions that did not contain these structures. We used predation event recorders (PERs) to assess the predation risk juvenile salmonids were exposed to, with linear distance (m) from diversions, and other predation risk factors in the north Delta. Finally, we used a boat electrofishing survey to determine the piscivore assemblage and compare spatial trends in black bass (Micropterus spp.) CPUE and relative abundance throughout these waterways.Piscivore abundance was greater near small water diversions than at adjacent shorelines and the predation risk of juvenile salmonids increased with diversion proximity. Additionally, predation risk increased with increasing piscivore abundance and decreasing water depth. The north Delta predator assemblage was dominated by black basses (Micropterus spp.), which likely drove the negative relationship of predation risk with water depth, given habitat requirements of these species. Furthermore, increasing smallmouth (Micropterus dolomieu) and spotted bass (Micropterus punctulatus) abundance in our northern study sites may have weakened temperature effects on predation, given metabolic requirements of these species.Our work demonstrated that small water diversions are likely to increase mortality of endangered salmonids, and that the north Delta predator assemblage was different than recorded by previous work in this system, changing predation risk factors. Although more work is needed to determine the population level impacts of diversions, the ubiquitous distribution of these structures warrants management solutions to reduce mortality from this source.These results indicate that in addition to entrainment and impingement, water diversions may increase mortality of small‐bodied fishes by attracting predators and elevating predation risk. Given the continual human demand for freshwater, predator–prey interactions should be considered along with entrainment and impingement when assessing intake infrastructure mitigation, especially when diversions co‐occur along migratory routes and essential habitat of imperilled fishes. [ABSTRACT FROM AUTHOR]

Curcumin, a polyphenol, targets multiple signaling molecules and shows activity at the cellular level, supporting its various health benefits. Thereafter, the present study examines the effects of different doses of dietary curcumin on growth indices, feed efficiency, serum metabolites, redox (oxidation) status, immunity, histological assessment, and antioxidant-related genes in red tilapia (Oreochromis sp, Oreochromis aureus x O. mossambicus). A total of 1200 red tilapia with an average weight of 19.1±0.03 g were distributed in 12 cement ponds (3×3.5×1m). Each treatment was assigned three pounds (n=100 replicates). For 60 days, fish were fed baseline diets containing 0, 0.4, 0.6, and 0.8 g of curcumin/kg of diet. The treated fish showed increased body weight and SGR (specific growth rate) compared to the T0 group (P<0.05). Curcumin in the diet significantly improved weight gain, percentages, and FCR (feed conversion ratio), with a dose-dependent effect (P < 0.05). Curcumin supplementation showed no influence on feed intake, fish mortality, or survival rate (P >0.05). The curcumin-treated fish groups improved tissue structure in hepatocytes, pancreatic lumens, hepatic blood sinusoids, and intestine tissue layers, particularly the mucosal layer. The T0.8 group had reduced liver enzymes (AST and ALT) and greater total protein and albumin levels (P<0.05). The T0.6 and T0.8 groups showed significantly lower MDA levels than the other groups (P < 0.05). Curcumin groups demonstrated significantly higher antioxidant indices (CAT, GPx, and SOD) compared to the basal diet (P<0.05). Curcumin administration resulted in significant improvements in IgM and lysosome levels (P<0.05). All supplemented groups had considerably (P<0.05) higher levels of SOD, CAT, and GPx mRNA than the control group. Consequently, administering 0.6–0.8 g/kg of curcumin to red tilapia (Oreochromis sp.) diets may improve the fish's growth, health, tissue composition, and antioxidant response. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to assess the effect of dietary supplements of either aqueous (AE) or ethanolic (EE) (Juniperus communis) leaf extracts on growth performance, intestinal health, hemato-biochemical indices, antioxidant, inflammation cytokine responses, and resistances against infection in Nile tilapia, Oreochromis niloticus. Fish groups were controlled with no extract (J1) and fed diets (J2, J3, J4, and J5) containing 1.0 and 2.0 g/kg aqueous and ethanolic extract for 60 days. Fish were given an intraperitoneal injection (IP) of Aeromonas hydrophila for 10 days after the feeding trial; then, the fish mortality was recorded. Growth, feed efficiency, and activity of endogenous enzymes (lipase, trypsin, chymotrypsin, and amylase) were significantly improved in all dietary J. communis groups, especially in J5, compared to other groups. Also, J5 showed the highest absorption area, muscularis, goblet cells, villi width, and fewer gut bacterial counts than the other groups. In addition, the J4 and J5 groups of tilapia fish exhibited a significant increase in the levels of total protein, serum albumin, globulin, hemoglobin, white blood cells, and hematocrit (P < 0.05), as well as a significant decrease in the levels of serum alanine, aspartate aminotransferases, glucose, and cholesterol compared to the J1 groups. Moreover, the J4 and J5 fish showed a significant decline in the levels of MDA with improvements in antioxidant (SOD, CAT, and GPX) and immunological (lysozyme, immunoglobulin M, and complement C3) indices compared to the J1 group. Fish in J4 and J5 exhibited downregulated levels of il-8, il-10, il-1β, tnf-α, ifn-γ, and hsp70 genes compared to other groups. In contrast, hepatic catalase (cat), superoxide dismutase (sod), and interleukin (il-10) gene expressions were upregulated. The lowest fish mortality after the bacterial challenge was recorded in the J5 group. These findings suggest that 2.0 g/kg feed ethanolic extract of J. communis-fed Tilapia fish fingerlings improved their growth and intestinal health, boosted their immune systems and antioxidant responses, and increased their resistance to A. hydrophila. [ABSTRACT FROM AUTHOR]

Aquaculture and the production of aquatic goods are rapidly growing industries in the world. These industries involve the cultivation of various saltwater and freshwater fish as well as shellfish species, and they undergo regular updates in their manufacturing processes. The increasing popularity of aquaculture is driven by the desire to achieve long-term sustainability in food production. However, the intensification of farming techniques can lead to economic losses due to fish mortality, which is often caused by infectious and stressful conditions. To address this challenge, it is crucial to enhance the immune response of fish as part of sustainable intensification and aquaculture management. Recently, there has been growing interest in eco-friendly and natural bioactive solutions as potential alternatives to synthetic compounds used for disease prevention in aquaculture. Medicinal plants, available as whole plants, plant extracts, or synthetic analogues of natural substances known as phytomedicines or phytopharmaceuticals, have shown high efficacy in disease prevention for humans and animals. One such medicinal plant is Saussurea lappa, which is extensively utilized in various forms of medicine for treating multiple diseases. The bioactive chemicals derived from S. lappa exhibit a wide range of biological activities, including anti-inflammatory, antioxidant, antimicrobial, and anticancer properties, along with immunostimulatory effects. Given the diverse biological activities of S. lappa and its potential to enhance the immune responses of aquatic species, this review focuses on exploring its contributions in this area. By examining the numerous benefits and applications of S. lappa, we aim to shed light on its potential role in improving the immune response of aquatic species. [ABSTRACT FROM AUTHOR]

Ecosystems and biodiversity across the world are being altered by human activities. Habitat modification and degradation are among the most important drivers of biodiversity loss. These modifications can have an impact on species behavior, which can, in turn, impact their mortality. While several studies have investigated the impacts of habitat degradation and fragmentation on terrestrial species, the extent to which habitat modifications affect the behavior and fitness of marine species is still largely unknown, particularly for pelagic species. Since the early 1990s, industrial purse seine vessels targeting tuna have started deploying artificial floating objects—Drifting Fish Aggregating Devices (DFADs)—in all oceans to increase tuna catchability. Since then, the massive deployment of DFADs has modified tuna surface habitat, by increasing the density of floating objects, with potential impacts on tuna associative behavior and mortality. In this study, we investigate these impacts for yellowfin tuna in the Indian Ocean. Using an individual‐based model based on a correlated random walk and newly available data on DFAD densities, we quantify for the first time how the increase in floating object density, due to DFAD use, affects the percentage of time that yellowfin tuna spend associated, which, in turn, directly impacts their availability to fishers and fishing mortality. This modification of tuna associative behavior could also have indirect impacts on their fitness, by retaining tuna in areas detrimental to them or disrupting schooling behavior. Hence, there is an urgent need to further investigate DFAD impacts on tuna behavior, in particular, taking social behavior into account, and to continue regulation efforts on DFAD use and monitoring. [ABSTRACT FROM AUTHOR]

During the flood season, high dam discharge rates result in total dissolved gas (TDG) supersaturation. This condition causes gas bubble trauma and can lead to fish mortality, which poses a significant threat to downstream river ecosystems. Assessing the ecological risks of TDG supersaturation is a challenge in waterpower-intensive river basins worldwide. Few studies have explored the impact of TDG supersaturation on fish behaviours, such as aggression and memory, which are crucial for feeding, reproduction, and predator avoidance. In this study, behavioural tests were conducted in a T-maze to investigate the effects of acute TDG supersaturation on swimming behaviour, aggression, and memory in medaka (Oryzias latipes). The results demonstrated that medaka exposed to TDG levels of 115% and 130% for 2 h had significantly reduced swimming performance.At TDG levels of 100%, 115% and 130%, medaka activity rates in the mirror arm of the maze in the mirror test were 44.34 ± 12.88%, 40.27 ± 15.44% and 35.35 ± 16.07%, respectively. Similarly, the activity rates of medaka in the active stimulus arm of the maze in the memory test were 50.35 ± 14.75%, 40.76 ± 12.51% and 35.35 ± 18.47%, respectively. The behaviour of medaka changed with increasing TDG supersaturation. These findings contribute to the development of an ecological risk assessment model for TDG supersaturation based on memory and aggression in fish and provide data for developing management strategies to mitigate the adverse effects of TDG supersaturation. [ABSTRACT FROM AUTHOR]

Fish farming is increasingly important globally and nationally, playing a crucial role in fish production for human consumption. Monitoring microbiological and chemical contaminants from water discharge is essential to mitigate the risk of contaminating water and fish for human consumption. This study analyzes the physicochemical and E. coli parameters of water and tambacu fish muscles (Colossoma macropomum × Piaractus mesopotamicus) in Western Maranhão, Brazil. It also includes a qualitative characterization of zooplankton in the ponds. Samples were collected from tambacu ponds in a dam system fed by natural watercourses from the Tocantins River tributaries, located at the connection of the Brazilian savanna and Amazon biomes. The physicochemical and E. coli parameters of water did not meet national standards. The zooplankton community included Rotifera, Cladocera, Copepoda, and Protozoa representatives, with no prior studies on zooplankton in the region, making these findings unprecedented. The biological quality of freshwater is crucial in fish farming, as poor quality can lead to decreased productivity and fish mortality, raising significant food safety concerns. The water quality studied is related to the potential influence of untreated wastewater as a source of contamination, leaving the studied region still far from safe water reuse practices. The findings on chemical and E. coli contamination of fish farming waters concern human health and emphasize the need for appropriate regulations. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive assessment of the black-barred halfbeak (Hemiramphus far) in Bardawil Lagoon, North Sinai, Egypt, focusing on key parameters such as length at first capture, growth metrics, mortality rates, and relative yield per recruit. Data were collected monthly from May to December 2022, comprising a total of 1,593 fish samples from commercial catches in the lagoon. The fish that were sampled ranged in length and weight from 17 to 36.7cm and 22 to 247.3g, respectively, with an average of 23.84cm and 85.67g. The formula for the length-weight relationship of the studied species was W = 0.0029 TL 3.2286. This study showed four age groups. The estimated von Bertalanffy growth parameters were L∞ = 37.8cm and k = 0.48 year-1. It was found that the growth performance index (Φ ') was 2.84. An estimate of the length at first capture was 20.89cm. The length at first capture was determined to be 20.89cm. The mortality rates were calculated as follows: total mortality (Z) at 2.15, natural mortality (M) at 0.95, and fishing mortality (F) at 1.2 year-1. The exploitation rate (E) was found to be 0.56, indicating overfishing and high fishing pressure on the population. The relative yield per recruit analysis (Y'/R) showed that the current exploitation level significantly exceeds the sustainable threshold (E0.5=0.383). To sustainably manage this resource, the current exploitation rate needs to be reduced by 32%, decreasing from 0.56 to 0.383. The findings from this investigation are critical for the assessment and management of the H. far fishery in Bardawil Lagoon, ensuring the sustainability of this important fish species. [ABSTRACT FROM AUTHOR]

The present study aimed to assess the stock of Chloroscombrus chrysurus in the Ivorian coastal waters to support its sustainable management. Approximately 2,520 specimens were collected between July 2022 and June 2023. The fish were captured using beach seines and gillnets, then measured and weighed to the nearest millimeter and gram, respectively. Stock assessment was conducted using the Fisat software, which analyzed pooled length-frequency data. The estimated growth parameters for Chloroscombrus chrysurus were as follows: asymptotic length (L∞) of 22.05cm, growth rate (K) of 0.82 year-1, growth performance index (Φ') of 2.59, theoretical age (t0) of -0.084 years, and life-span (Tmax) of 3.57 years. Instantaneous fishing mortality (F) was estimated at 0.81 year-1, while natural mortality (M) was 1.70 year-1. The exploitation rate (E) was 0.32. The length at first capture (Lo50) was 13.32cm, which is slightly lower than the length at first sexual maturity (13.42cm). The findings indicate that the Chloroscombrus chrysurus population in Côte d'Ivoire's coastal waters is at moderate risk of overexploitation. To mitigate this risk, it is crucial to monitor the fishery and to implement immediate measures, such as increasing the mesh size of the nets and the cod-end or bag of beach seines. [ABSTRACT FROM AUTHOR]

The study on Bronze Featherback in Huai Kho Reservoir examined 273 specimens, with fork lengths ranging from 105 to 295mm and an average length of 185.80 ± 27.05mm. The fish exhibited a strong length-weight correlation, with an allometric coefficient (b) greater than 3.00, indicating a positive allometric growth. Growth parameters included an asymptotic length (L∞) of 309.75mm and a growth coefficient (K) of 0.10. Capture probabilities were 108.99 (L25%), 186.52 (L50%), and 191.44mm (L75%). Mortality rates were measured with a total mortality rate (Z) of 1.07 per year, natural mortality (M) at 0.22 per year, and fishing mortality (F) at 0.86 per year. Recruitment peaks occurred from June to August, and replacement rates were the highest from July to September. The current exploitation rate (E) of 0.80 exceeds the maximum sustainable rate (Emax) of 0.724. The total steady-state biomass was 10.57 tons. To promote sustainable management, it is recommended to regulate fishing gear and enforce a fishing ban during the spawning season. [ABSTRACT FROM AUTHOR]

Two of the most-commonly used pyrethroid insecticides were subjected to static bioassays to determine their acute toxicity to Clarias gariepinus fingerlings, followed by comparisons of their impact on mortality and behavioural changes in the fish. The LC50 values for deltamethrin (DMT) at exposure durations of 24, 48 and 96 h were 12, 9 and 8 µg l−1, respectively; the LC50 values for cypermethrin (CYP) at the same exposure durations were 55, 44 and 26 µg l−1, respectively. The estimated safe limits ranged from 8×10−1 to 8×10−5 µg l−1 for DMT, and 26×10−1 to 26×10−5 µg l-1 for CYP. The tested substances had an acute toxicity effect on fish development as they caused death, and chronic toxicity effects as they changed fish behaviour. Fish exposed to either one of these pesticides showed behavioural alterations, such as loss of static balance, excessive mucous secretion, irregular swimming, gulping of air and skin discolouration. The results reveal that CYP was less toxic (96-h LC50 = 26 µg l−1) than DMT (96-h LC50 = 8 µg l−1) based on the greater LC50 value and a lower percentage of mortality. To avoid potential ecotoxicological risks to aquatic life, use of these pyrethroids in both terrestrial and freshwater ecosystems must be treated with caution. [ABSTRACT FROM AUTHOR]

The adequate collection of health information at the farm level is the first step in good health management. The objective of this study was to analyze how Spanish fish farms collect their census, disease occurrence, and mortality data through their farm record books and how they use them for reporting to competent authorities. Comparing and contrasting farm books between regions (autonomous communities) revealed a lack of standardization and substantial differences in the reporting. Therefore, this study points out the need to improve and standardize, at the national level, the design of fish farm record books in order to ensure the better collection of farm census data on mortality and disease occurrence, which may facilitate the production of epidemiological reports and the early detection of emerging diseases at the national level. [ABSTRACT FROM AUTHOR]

Twelve commercial species exploited in the eastern Guangdong and southern Fujian waters were assessed using the Catch-Maximum Sustainable Yield (CMSY) and Bayesian Schaefer Model (BSM) methods. The carrying capacity (k), intrinsic rate of population growth (r), maximum sustainable yield (MSY), and relative biomass (Bend/k and B/BMSY) were estimated. The current stock status was defined by B/BMSY and fishing mortality (F/FMSY). The results indicate that seven stocks were overfished or below safe biological limits (B/BMSY < 0.5 or F/FMSY > 1), two stocks were in a recovery phase (0.5 < B/BMSY < 1, F/FMSY < 1), and three stocks were under sustainable fishing pressure with healthy biomass, capable of producing yields close to the MSY (B/BMSY > 1, F/FMSY < 1). The stock statuses are consistent with previous studies on the utilization of pelagic fisheries in the eastern Guangdong and southern Fujian waters and with those assessments in other waters. The results of the assessments suggest that these stocks could be expected to produce higher sustainable catches if permitted to rebuild; thus, more effective and proactive management is needed in this upwelling fishing ground. [ABSTRACT FROM AUTHOR]

Freshwater fisheries in developing regions provide livelihoods and nutrition for millions of people worldwide. These fisheries are frequently data poor, which limits fisheries management. The seasonal Cambodian dai platform fishery on the Tonle Sap River is one of the best monitored inland fisheries in Southeast Asia, yet catch sampling is limited and there is no fishery-independent monitoring. A monitoring system is needed to characterize fish migration and mortality, be cost effective, and be deployable in areas with minimal infrastructure. We integrated a Simrad wide-band transceiver mini echosounder (200 kHz), solar power, and an Internet of Things communications module as an autonomous, automated monitoring package for the deployment on upstream and downstream commercial fishing platforms. The solar panel and controller supply direct current power to the echosounder, communications module, and battery for power during dark hours. Echosounders are programmed to sample at 1 Hz for 15 min every hour. The communications module is a built cellular endpoint that accesses a local wireless network to transmit raw data files to a data server. Data are downloaded from the server for processing and analysis. This expandable system provides a flexible management tool that can be deployed at any location with wireless communication capability. [ABSTRACT FROM AUTHOR]

Maximum sustainable yield reference points (MSY-RPs) are usually calculated assuming spawner-recruitment relationships (SRR) and population dynamics of the stock. However, due to the difficulty of estimating SRR, the uncertainty in MSY-RPs is often too large to be put into practice. Therefore, based on the concept of maximum–minimum yield (MMY), fishing mortality (F) that gives %SPR (spawner biomass per recruitment [SPR] at a given F relative to SPR in the absence of fishing) of 30–50% (F30-50%SPR) is often used as a proxy of FMSY (F that maximizes the long-term catch). In this study, we estimated F % SPR MMY (F expected to produce %SPR at MMY) for 30 stocks of Japanese fishery resources based on the life-history parameters of the stocks and steepness assumptions derived from meta-analysis. Our results showed that %SPRMMY ranged from 23% to 62% (excluding 86% of Scomberomorus niphonius), depending on the stock and the assumed steepness scenario. If the fish were caught under F % SPR MMY , at least 70% of the MSY could be expected in Japanese fishery resources. When compared with the %SPRMSY for the 15 stocks estimated through Japanese fishery stock assessment, %SPRMMY were similar, or often larger. %SPRMMY can be considered a precautionary value, reflecting the uncertainty of SRR. [ABSTRACT FROM AUTHOR]

Most fisheries are conducted without any scientific knowledge about the size and productivity of the stocks that support them. This navigation in the dark in most fisheries is a major obstacle in making them sustainable sources of nutrition for people in general and income for fishers and other economic actors along supply chains. Fisheries that have not been assessed generally are data‐intermediate and data‐poor, the latter usually having annual time series of landings as the single piece of data available. A major effort in the last two decades has been directed toward developing 'catch‐only' stock assessment methods, although some of these methods have been tested and found deficient. Here we provide a novel approach to using annual landing time series as the single source of data to qualitatively judge the condition of un‐assessed stocks using frequentist cumulative probability ogives, both in terms of stock biomass and fishing mortality. A meta‐analysis of the FishSource database allowed us to infer statistical patterns from hundreds of assessed fisheries and thousands of annual landings, biomass, and fishing mortality observations. Four stock‐management types were considered separately in the analysis: short‐lived and others (mid‐ to long‐lived) stocks, controlled or not controlled by catch limits. Obtained cumulative probability ogives provide clear evaluations of stock biomass and fishing mortality trends in all four stock‐management types, leading to actionable information on probable current status and future trends. Using these probability ogives, we developed decision trees that lead to qualitative scores on the exploitation status of un‐assessed stocks. [ABSTRACT FROM AUTHOR]

The knowledge of the life-history traits of commercial and data-deficient fish species is essential for assessing, among others, their status, as well as for the formulation of conservation measures and the implementation of sustainable managerial decisions. In the present study, growth parameters were estimated for eight fish species of the Lake Trichonis (Greece): Atherina boyeri, Cobitis trichonica, Leucos panosi, Luciobarbus albanicus, Rhodeus meridionalis, Salaria economidisi, Scardinius acarnanicus and Tropidophoxinellus hellenicus. The mortality and exploitation status were estimated for the five most exploited ones (A. boyeri, L. panosi, L. albanicus, S. acarnanicus and T. hellenicus). For four of the abovementioned species (C. trichonica, R. meridionalis, S. economidisi and T. hellenicus), life history data were provided for the first time. A. boyeri (a commercially important and the most exploited species in the lake) and T. hellenicus (a discarded species) exhibited the highest values of fishing mortality, followed in descending order by L. albanicus, L. panosi and S. acarnanicus. The information produced in the present study can be incorporated in ecosystem-based models aiming at the establishment of management and conservation measures at both species level and ecosystem level. [ABSTRACT FROM AUTHOR]

Copyright of Nachrichten aus der Chemie is the property of Wiley-Blackwell 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.)

The present study investigated the effect of polypropylene (PP) microplastics on the growth performance, hematological profile and oxidative stress responses in the liver and brain tissues of Oreochromis niloticus juvenile. The microplastic exposure was done by offering microplastic‐incorporated feed to the fish. The feed was prepared by mixing microplastics and the feed in three different ratios; Low (1.5 g/kg), Medium (3.0 g/kg), High (4.5 g/kg), and a control with no plastics in it. The trial was done for 7 weeks. A significant impact on the growth performance of the fish was observed in terms of body weight gain, specific growth rate, metabolic growth rate, protein efficiency ratio and energy retention. All the treatments had a significant difference in growth parameters compared to the control. The results of the hematological profile confirmed erythropoietic impairment in the fishes due to high microplastic exposure which led to an anemic condition in the fishes and mortality in the early juvenile stage. The antioxidant enzyme analysis also shows significant oxidative stress induced in liver and brain tissues in a dose‐dependent manner. Exposure to PP microplastics significantly affected the growth, health and metabolism of O. niloticus. Further studies on genetic and cellular levels should be done to elucidate the wide‐ranging effects of MPs on fish species. [ABSTRACT FROM AUTHOR]

Sterlet (Acipenser ruthenus), one of the last sturgeons in the Danube basin, is regularly stocked in national and international restoration programs, but the efficacy of stocking has not yet been evaluated. Effectiveness of stocking should involve marking and evaluating growth and survival of juveniles. Chemical marking with alizarin red S (ARS) was evaluated to establish optimal ARS staining approaches for juvenile sterlet. Bathing in a 100–200 mg l−1 ARS concentration for 12 h had no affect on fish mortality or growth. Use of a green laser on the upper five external structures (dorsal, lateral, and ventral scutes and rostral and anal plates) allowed easy detection for at least a year. Simultaneous use of multiple external structures was effective for distinguishing stocked from wild fish without harm or sacrifice. We conclude that ARS staining enabled a cost‐effective, quick, and labour‐nonintensive way to mark sterlet, with a high‐field detectability and minimal previous experience required. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants generally found in complex mixtures. PAHs are known to cause pleiotropic effects on living organisms, including developmental defects, mutagenicity, carcinogenicity and immunotoxicity, and endocrine disruptions. The main goal of this study is to evaluate the toxicity of water-accommodated fractions (WAFs) of oils in two life stages of the Japanese medaka, larvae and juveniles. The deleterious effects of an acute exposure of 48 h to two WAFs from Arabian light crude oil (LO) and refined oil from Erika (HO) were analyzed in both stages. Relevant endpoints, including ethoxy resorufin-O-deethylase (EROD) activity, DNA damage (Comet assay), photomotor response, and sensitivity to nervous necrosis virus (NNV) infection, were investigated. Larvae exposed to both oil WAFs displayed a significant induction of EROD activity, DNA damage, and developmental anomalies, but no behavioral changes. Deleterious effects were significantly increased following exposure to 1 and 10 μg/L of LO WAFs and 10 μg/L of HO WAFs. Larval infection to NNV induced fish mortality and sharply reduced reaction to light stimulation. Co-exposure to WAFs and NNV increased the mortality rate, suggesting an impact of WAFs on fish defense capacities. WAF toxicity on juveniles was only observed following the NNV challenge, with a higher sensitivity to HO WAFs than to LO WAFs. This study highlighted that environmentally realistic exposure to oil WAFs containing different compositions and concentrations of oil generated high adverse effects, especially in the larval stage. This kind of multi-marker approach is particularly relevant to characterize the toxicity fingerprint of environmental mixtures of hydrocarbons and PAHs. [ABSTRACT FROM AUTHOR]

Nile tilapia is the main farmed fish in Brazilian aquaculture. Streptococcus agalactiae (GBS) is responsible for high mortality rates in fish farms. Genetic improvement is considered an effective alternative for producing resistant animals in aquaculture. The objective of this study was to estimate genetic parameters for resistance to GBS infection in a breeding population of Nile tilapia from Brazil, based on disease challenge using a circulating serotype (Ib and STNT). Furthermore, genetic correlations between resistance to GBS and average daily gain (ADG) were estimated to determine whether these traits can be included in selective breeding programs. Survival (SS) and time until death (TD) were the evaluated traits. The survival of the most resistant families was approximately 30%, indicating high phenotypic variation in resistance to the infection. Low to moderate heritability values for resistance traits in the Nile tilapia population were estimated, ranging from 0.14 to 0.27. Heritability for ADG was moderate to high (0.40) based on a growth trial involving 43 families (735 animals). Phenotypic correlations between the resistance traits (SS and TD) and ADG were positive and low, ranging from 0.09 to 0.18, whereas genetic correlations were close to zero. Phenotypic and genetic correlations between SS and TD were considered high and positive, ranging from 0.38 to 0.72. The results suggest that selection for resistance against GBS does not negatively affect juvenile weight gain in Nile tilapia. [ABSTRACT FROM AUTHOR]

Climate change and global warming have led to more frequent harmful algal blooms in the last decade. Among these blooms, Heterosigma akashiwo, a golden‐brown phytoflagellate, is one of the 40 species with a high potential to form harmful blooms, leading to significant fish mortality. Climate change leads to rising atmospheric and ocean temperatures. These changes, along with altered rainfall patterns and meltwater input, can cause fluctuations in ocean salinity. Elevated atmospheric carbon dioxide (CO2) levels increase water acidity as oceans absorb CO2. This study investigated the effects of temperature, salinity, and CO2 levels on lipid production, hemolytic activity, and toxicity of H. akashiwo using the design of experiment approach, which can be used to investigate the effect of two or more factors on the same response simultaneously in a precise manner with fewer experiments and materials but in a larger region of the factor space. The lipid content was measured using a high‐throughput Nile Red method, and the highest level of lipid content was detected at 25°C, a salinity of 30, and a CO2 concentration of 400 ppm. Hemolytic activity was assessed using rabbit blood erythrocytes in a 96‐well plate, and the optimal conditions for achieving the highest hemolytic activity were determined at 15°C, a salinity of 10, and a CO2 concentration of 400 ppm. As the chemical structure of the toxin is not known, we used the toxicity against the cell line RTgill‐W1 as the cell toxicity proxy. The maximum toxicity was identified at 15°C, a salinity of 10, and a CO2 level of 700 ppm. [ABSTRACT FROM AUTHOR]

Whiteleg skate (Amblyraja taaf) is a bycatch species commonly discarded in demersal longline fisheries targeting Patagonian toothfish around the Crozet archipelago (Southern Ocean). While there are global conservation issues on elasmobranchs, the post-release survival of this deep-sea species remains unknown. This study is the first tagging programme conducted on Whiteleg skates to investigate their fate after being released at sea. Almost 3000 skates were captured, double-tagged with conventional tags and released between 2020 and 2022 to assess survival using capture–mark–recapture (CMR) models. Our primary result was an estimated annual apparent survival rate higher than 92% for skates released in good condition (with 185 skates recaptured after up to 944 days at liberty). Low detection rate highlighted methodological challenges for CMR models. However, skate size and depth of capture had an effect on apparent survival probability with smaller individuals having lower values (<65 cm; 0.84 ± 0.04) as well as skates caught at shallower depths (<1200 m; 0.83 ± 0.04). Overall, this study suggests that the mandated release of skates in good condition is effective to limit fishing impact on skates in this fishery. To further limit this impact, we recommended changes in fishing practices (hauling speed and soak time). [ABSTRACT FROM AUTHOR]

Globally, catadromous freshwater eels of the genus Anguilla are of conservation concern, including critically endangered European eel (Anguilla anguilla). Pumping stations that move river water to a higher elevation severely impact eels during their seaward spawning migration. Fish-friendly pumps can mitigate fish injury and mortality but here we uniquely rethink a fish-friendly pump as a fish passage solution. In this pluriannual study, the seasonal timing of pump operation was misaligned with the typical silver eel migration period. Eels were almost exclusively nocturnal but night-time pumping represented as little as 5.6% a year. Night-time eel approaches were primarily influenced by pump duration and temperature, but did not align with lunar phase, unlike in unregulated rivers. After reaching the pumping station, eel passage was influenced by weedscreen aperture and increased when the aperture was increased. Passive sensor collision suggested non-pump infrastructure could cause injury and mortality to eels. It is therefore recommended pump operation should align with the timing of silver eel migration, weedscreen and pump entrance efficiencies should be maximised, and non-pump infrastructure must have low fish injury risk. Ultimately, considering the entire structure a fish passage solution will help ensure fish-friendly pumps have high conservation value for anguillid eels globally. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, environmental DNA technology, 16S rRNA gene sequencing, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were employed to investigate the relationships between Tetrahymena pyriformis, bacteria, and guppies under varying temperature and pH conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observations were studied. Results of this study showed that several bacteria were related to T. pyriformis, and environmental factors affected the interaction between bacteria and T. pyriformis. In the aquaculture system of ornamental fish, the interaction between bacterial microbiota and ciliate protozoa can prevent or promote disease outbreaks, and different physicochemical conditions will affect the relationships between them. We investigated the interaction between bacterial microbiota and the parasite Tetrahymena pyriformis when infecting Poecilia reticulata (guppy) under different physicochemical conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observation were studied or monitored using environmental DNA (eDNA) extraction technology, the qPCR method, and 16s rRNA sequencing, respectively. The morphological identification and phylogenetic analysis of T. pyriformis were carried out. The infected guppy tissue was also stained by the hematoxylin and eosin methods. The results showed: (1) the bacterial communities of water samples were mainly composed of species assigned to Proteobacteria and Bacteroidetes, and Tabrizicola and Puniceicoccaceae were positively correlated with fish mortality, T. pyriformis abundance, and temperature. (2) Arcicella and Methyloversatilis universalis with different correlations between ciliates appeared in different treatment groups, the result of which proved that environmental factors affected the interaction between bacteria and T. pyriformis. (3) Lower temperatures and a higher pH were more beneficial for preventing disease outbreaks. [ABSTRACT FROM AUTHOR]

The Atlantic pearl oyster Pinctada radiata (Leach, 1814), the first documented Lessepsian bivalve species to enter the Mediterranean basin, is present in various coastal areas in Greece, and constitutes, almost exclusively, a domestic commercial bivalve resource. The present study aimed to contribute to the limited information available on P. radiata population structure and dynamics in Hellenic waters, especially following the recent enforcement of legislation for regulation of its fishery. A total of 703 individuals were collected using scuba diving from the South Evoikos Gulf. The male-to-female ratio (1:1.70) significantly departed from 1:1. A higher probability for female prevalence was exhibited for shell heights over 50.77 mm. Significant differences were exhibited in the shell height–total weight relationship between the sexes. The fourth-year class was the dominant cohort, comprising 50.09% of the population, out of the seven age classes identified. Asymptotic length was estimated at 109.1 mm and growth index at 3.35, respectively. Longevity was estimated at 15.7 years, with natural mortality (M) at 0.39 and total mortality (Z) at 0.76. The probability of capture (LC50) was estimated at 50.72 mm at 2.8 years. Biological reference points FMSY and EMSY were higher than the fishing mortality and current exploitation rate, respectively, indicating the potential for further population exploitation. [ABSTRACT FROM AUTHOR]

Catch‐and‐release angling is common in recreational fisheries, but post‐release mortality (PRM) may be high. We conducted a controlled field experiment to estimate mortality of released snapper Chrysophrys auratus. Recreational fishers caught 960 snapper from three depth strata (<15, 15–25, 26–40 m) that were either lip‐hooked, foul‐hooked or gut‐hooked. A bottom longline vessel caught 162 lip‐hooked fish in shallow water to serve as controls. Fish were held in 15‐m deep holding nets. All control fish and 80% of treatment fish survived, with anatomical hook site and capture depth significantly predicting mortality. Probability of mortality was lowest for lip‐hooked fish in shallow water (5 m = 0.00, 95% CI [0.00, 0.03]), but increased rapidly to 20 m (0.24, 95% CI [0.2, 0.3]). Mortality of foul‐hooked fish increased steadily with depth from 0.05 (95% CI [0.00, 0.78]) at 5 m to 0.65 (95% CI [0.13, 0.96]) at 40 m. Gut‐hooking resulted in high mortality at all depths but a low sample size resulted in high uncertainty of estimates. Our results indicate that snapper PRM can be reduced by fishing in shallow water and by mitigating gut‐hooking, possibly by using large circle hooks. [ABSTRACT FROM AUTHOR]

The tubular pump is a typical water transfer apparatus designed for extremely low heads and large flow rates. It serves as the core equipment in pumping stations situated at lakes, rivers, and canals. An adverse effect on the ecological environment stems from fish injury and mortality primarily caused by blade strikes. The present work combines computational fluid dynamics and the discrete element method to simulate the dynamics of fish passing through a simplified blade, allowing us to establish a safe margin of the strike force to further assess fish damage in a more complex tubular pump system. The results indicated that strikes on fish alter their motion state in terms of direction and magnitude, inducing chaotic movements that heighten the risk of subsequent strikes with downstream components. Fish tend to align their velocities with the surrounding fluid due to flow-induced drag after multiple contacts with solid structures. The knife-shaped leading edge, and particularly the blade tip side, emerged as the primary factor in creating strike damage, and the adoption of a slanted and blunt leading edge can effectively reduce fish damage. In addition, decreasing the shaft speed, increasing the flow rate, and restricting the fish size were identified as measures conducive to fish survival in running pumps. The study further suggested that using fewer but larger pumps operating at lower shaft speeds would contribute to better fish friendliness, which can also ensure a sufficient delivery head and mass flow rate. [ABSTRACT FROM AUTHOR]

This paper proposes a novel ensemble approach, integrating Artificial Neural Networks (ANNs), Symbolic Regression (SR), and Decision Trees (DTs), to predict fish mortality caused by infectious diseases. The intensifying global burden of fish diseases threatens the sustainability of aquatic ecosystems and the aquaculture industry, necessitating sophisticated modelling strategies for effective disease management and control. The proposed approach capitalizes on the non-linear data modelling strength of ANNs, the explanatory power of SR, and the decision-making efficiency of DTs, offering both predictive accuracy and interpretable insights. The architecture of the proposed ensemble method is developed in two stages. In the intermediate stage, an ANN is employed to learn the complex, non-linear interactions between various biological and environmental factors impacting fish health. Additionally, SR is applied to produce a symbolic equation that effectively maps the input variables to fish mortality rates. In the final stage, a DT model is included to enhance prediction performance by capturing decision rules from the data. This hybrid approach offers superior prediction performance while also revealing meaningful biological/environmental relationships that can guide preventive and reactive interventions in the management of fish health. We evaluate the developed models using extensive real-world datasets acquired from two large Greek fish-farming units, which encompass representative disease types. The results demonstrate that our ensemble approach significantly outperforms traditional standalone models developed in our recent previous work, achieving enhanced predictive accuracy, robustness, and interpretability. Overall, this research has far-reaching implications for improving disease predictions, facilitating optimal decision-making in aquaculture management, and contributing to the sustainability of global fish stocks. [ABSTRACT FROM AUTHOR]

Why offspring size and number vary in diverse ways with adult body size is little understood. In my comparative analysis of animal taxa, I show that age-specific mortality predicts the interspecific body-mass (BM) scaling of offspring (egg, embryo, or neonate) mass (OM) and number per clutch (CS) with striking accuracy. Across six animal taxa, the mean ratio of juvenile to adult mortality (mj/ma) explains 80% and 88% of the variation in BM scaling slopes for OM and CS, respectively. Animal taxa with high parental care and low mj/ma ratios tend to exhibit steeper OM scaling and shallower CS scaling than taxa with low parental care and high mj/ma ratios. Even the curvature of OM scaling in logarithmic space can be predicted approximately by the difference in the BM scaling slopes of juvenile and adult mortality rates. The overall triangular pattern of variation in OM in relation to BM in animals can be understood in terms of body-size dependent variation in mj/ma, as well. These results are explained by an 'age-specific mortality hypothesis', which posits that OM and CS scaling slopes are functions of the relative emphasis of natural selection on offspring versus parental fitness. Therefore, I recommend that future studies of the body-size scaling of life-history traits should include estimates of age-specific mortality. In general, it is becoming clear that a mortality perspective can provide useful insight into many kinds of biological and ecological scaling relationships. [ABSTRACT FROM AUTHOR]

Interaction with fishing gears represents the main anthropogenic threat at sea for sea turtles worldwide, and identifying the hotspots of turtle bycatch is a priority knowledge gap.Turtle stranding data represent a source of information about mortality areas at sea that are not fully exploited. This study aims to infer turtle mortality areas of turtles stranded along the Italian Adriatic Coast in the period 2019–2021 (1432 records), through backtrack modelling of carcasses. Specifically, the decomposition process of eight loggerhead carcasses was monitored, and the relationship between floating period (FP), turtle size and sea temperature was modelled through a generalized additive model. Oceanographic information was then used to track the routes of floating carcasses back, knowing their size and decomposition stage, and finally estimate the likely area of mortality. A complementary numerical experiment of connectivity between coastal and offshore areas gave indication that areas of potential mortality are relatively close to the coast, particularly in the northern Adriatic.Stranded turtles probably represent just a small fraction (17%–25%) of total at‐sea mortalities in the study area (Italian Adriatic waters), with decomposition rates, season and distance from shore influencing their stranding likelihood. Hence, strandings can inform only about spatio‐temporal variability of coastal mortality hotspots.Inferred areas of turtle mortality were most likely located in the North and Central Adriatic all over the year and overlap with heatmaps of fishing effort, obtained from vessel monitoring system (VMS) and automatic identification system (AIS) data, in the Gulf of Manfredonia and in the North‐West Adriatic in the cold (September–December) and warm (May–August) periods, respectively. [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]

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]

Introduction: Recent minimum population estimates are critical for effective marine mammal conservation, yet such estimates are often lacking at the stock or management level. Throughout the Main Hawaiian Islands, pantropical spotted dolphins (PSD; Stenella attenuata attenuata) are comprised of a pelagic and three island-associated stocks (O‘ahu, 4-Islands, and Hawai‘i Island). The insular stocks, in particular, face multiple anthropogenic and natural threats such as vessel impacts, fisheries interactions, marine debris, climate change, and disease. Prior to this study, no abundance estimates of the 4-Islands (i.e., the Maui Nui region) PSD stock existed that were suitable for management use and inclusion in stock assessment report calculations. Methods: We generated annual mark-recapture abundance estimates of naturally marked adults in a POPAN-framework using photo-identification data collected from small-boat surveys during 2014–2022 in the Maui Nui region. We extrapolated these estimates to the wider population using dorsal fin mark rates. Results and discussion: We collected data on 62 groups of PSD, throughout all months of the year, and with an average group size of 55.70 (SD = 17.31). We analyzed encounter histories of 174 distinct individuals. Annual recapture rate averaged 1.84 (SD = 1.32) with a maximum of 7. Individuals detected per year averaged 35.67 (SD = 21.16) with a maximum of 77 in 2017. Overall mark rate was 0.495 (SE = 0.010), resulting in total annual abundance estimates that averaged 154.87 (SE = 14.25) and ranged from 105 (SE = 13) in 2014 to 232 (SE = 31) in 2017. Although abundance estimates fluctuated, generally 250 animals or less used the study area each year and we found no overall evidence of a trend. Our benchmark results revealed a small population in need of monitoring given the numerous threats facing this stock, the uncertainty of their impacts, and the decreased resiliency and recovery potential of small populations to negative demographic and environmental stochastic events. Our findings, including documenting long-term site fidelity and year-round presence of PSD in Maui Nui, further signify this area as one of future research and conservation importance. [ABSTRACT FROM AUTHOR]

Introduction: This study examines the understudied historical evolution of the seafood value chain in southern Brazil by analysing newspaper articles from Santa Catarina state, published between 1855 and 2019. Methods: Through a meticulous review of 598 selected articles, we reconstruct the development and transformation of small-scale fisheries (SSF) and their interaction with the emerging industrial fishing sector. Results and discussion: Our findings highlight the central role of SSF in the seafood value chain, contributing significantly to production, processing, retail, and trade, despite increasing competition and challenges from industrial fishing and aquaculture. The analysis reveals shifts in fish species targeted, processing methods employed, market dynamics, and consumption patterns over time. Notably, the study uncovers the resilience and adaptability of SSF in maintaining their importance to local economies and food security, amidst technological, economic, and regulatory changes. Furthermore, it underscores the often-overlooked contributions of women in seafood value chains, advocating for their equitable recognition. By providing a comprehensive and multi-faceted historical perspective, this research can inform contemporary policy-making, aiming to foster more resilient, inclusive, and sustainable seafood value chains in Brazil. [ABSTRACT FROM AUTHOR]

Introduction: The circular bioeconomy concept revolves around biological production cycles that reintroduce products or waste from one production system to another, aiming to maximize resource utilization while minimising environmental impact. The purpose of this study was to evaluate and compare the element flow when integrating black soldier fly larvae (BSF) production with Nile tilapia production using varying experimental fish feed. Methods: Tilapia (42.5 ± 11.2 g) were reared in recirculating aquaculture systems (RAS) at 25.5°C for 10 weeks and fed equal daily rations of four experimental diets containing fishmeal (FM), poultry blood meal (PBM), black soldier fly meal (BSF) and poultry by-product meal (PM) as the single main protein source, respectively. Faeces was collected daily from settling columns installed in the RAS and subsequently fed to BSF larvae. Results and discussion: The fish exhibited the highest biomass gain when fed with FM (1,001 g) or PM (901 g). The growth was lowest for those fed with PBM (406 g). The fish fed with PBM also produced the highest amount of faeces (234 g). When the fish faeces were utilized as a substrate for rearing black soldier fly (BSF) larvae and although the biomass gain did not differ significantly, the feed conversion ratio (FCR) varied among larvae fed with different fish faeces, ranging from 8.36 to 25.04. Furthermore, the concentration of analysed elements (Al, B, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, S, and Zn) varied based on the type of fish faeces provided. Results illustrate that a modulation of BSFL elemental composition is possible through manipulating the feed provided to the fish and emphasize the importance of fish feed composition for fish performance as well as the compositional quality of the larvae reared on the resulting fish faeces. Hence, if BSF larvae production is to be harnessed for the recycling of aquaculture sludge, ingredient choice and subsequent elemental composition of fish feeds are pivotal to larvae composition. [ABSTRACT FROM AUTHOR]

The Precautionary Approach to Fisheries Management requires an assessment of the impact of uncertainty on the risk of achieving management objectives. However, the main quantities, such as spawning stock biomass (SSB) and fish mortality (F), used in management metrics cannot be directly observed. This requires the use of models to provide guidance, for which there are three paradigms: the best assessment, model ensemble, and Management Strategy Evaluation (MSE). It is important to validate the models used to provide advice. In this study, we demonstrate how stock assessment models can be validated using a diagnostic toolbox, with a specific focus on prediction skill. Prediction skill measures the precision of a predicted value, which is unknown to the model, in relation to its observed value. By evaluating the accuracy of model predictions against observed data, prediction skill establishes an objective framework for accepting or rejecting model hypotheses, as well as for assigning weights to models within an ensemble. Our analysis uncovers the limitations of traditional stock assessment methods. Through the quantification of uncertainties and the integration of multiple models, our objective is to improve the reliability of management advice considering the complex interplay of factors that influence the dynamics of fish stocks. [ABSTRACT FROM AUTHOR]

The Channa limbata fish is a type of tropical freshwater fish of the Channidae family which is relatively small as an aquarium ornamental fish with a distinctive color at the tip of its dorsal fin and has a snake-like head (dwarf snakehead). Natural snakehead fishing activities have threatened its sustainability. Breeding C. limbata fish through cultivation can increase its potential for sustainable use. This study aims to evaluate the acclimation response of wild-type dwarf snakehead fish in captivity and its sexual characteristics as a basis for domestication and hatchery technology. The fish samples used were natural catches from rivers in West Java measuring <100 mm to >150 mm of body length then individually acclimated indoors in an aquarium (35×20×20 cm) for 14 days. Snakehead fish live in shallow, slow-flowing river waters with a temperature of 20.2-21.3°C, TDS 16-24 mg/L at neutral pH, while the rearing water temperature and TDS are higher (temperature: 24.9-27.6°C; TDS: 88-110 mg/L). The fish mortality rate during acclimation reached 25% in fish measuring >150 mm of length on tenth day, while fish measuring <150 mm more adaptive with 100% survival. The male fish measuring 100-150 mm have 13-15 pectoral fin rays while female fish have fewer (13-14). The gonad development level of male C. limbata in nature is slower than female fish measuring 100-150 mm with a gonadosomatic index of ovaries reached 10 times higher than testicular. [ABSTRACT FROM AUTHOR]

For freshwater or marine fish farming to be successful, live fish must be transported. This can be performed with eggs, larvae, juveniles, and adults. Nonetheless, because of the handling, confinement, and duration of transport, it is considered a difficult procedure. To prevent significant physiological changes that could result in fish mortality, it is crucial to look for ways to reduce stress and enhance the quality of transport water. Consequently, a comprehensive range of research on the use of additives in water, including salt and artificial or natural anesthetics, is presented in this review, which also discusses potential changes in water quality factors during transport, such as dissolved oxygen (DO), carbon dioxide (CO2), pH, ammonia, and temperature. The usage of stocking densities during transport is also covered in this review, with consideration given to the various recommendations for each species, fish size, and length of transport. [ABSTRACT FROM AUTHOR]

Between 2021-2022, a dense mucilage disaster occurred in the Sea of Marmara in Türkiye. Mucilage mostly covered coastal areas, which juvenile fish use for nurseries, growth, and protection. Due to Sand steenbras having been suggested as an environmental bioindicator species for Mediterranean coastal waters, this study attempts to reveal post-mucilage distribution and potential differences on the timing of hatching, daily age, growth, and mortality as revealed by the otolith microstructure. Individuals were sampled using beach seine nets from 12 equally spaced stations along the Sea of Marmara. Its presence and significant abundance in 10 out of 12 stations showed the Sand steenbras to be a common juvenile species for the Sea of Marmara. Hatching occurs between May- January, with peak hatching occurring in October. When considering that the mucilage had completely disappeared from the environment in August, the first set of hatching months can be seen to coincide with the dense mucilage. Thus, Sand steenbras can be considered as able to reproduce under these environmental conditions. The daily age of the Sand steenbras juveniles ranged between 38-235 days, with a mean of 120.3 ± 1.8 days. The daily growth and mortality rates were also calculated respectively as 0.226 mm/day and 4.11%. [ABSTRACT FROM AUTHOR]

The study determined acute toxicity, behavioural changes and histological effects of atrazine on juvenile Clarias gariepinus. The experiment involved exposing groups of fish to different concentrations {0.00 (control), 3.75, 6.25, 8.75, 11.25 and 13.75mg/l} of atrazine and monitoring fish mortality, physicochemical parameters of the test water and behavioural changes in the fish. The histological assessment of liver and gills was also carried out on dead fish to examine possible changes in their structural makeup in comparison to the organ extracted from the control. Acute toxicity test was conducted using standard methods and fish mortality was monitored for 96 hours. The physico-chemical parameters such as temperature, pH, dissolved oxygen, total dissolved solids and electrical conductivity in the test solutions were monitored using standard procedure. The study revealed that there was no mortality in the control group, which had no atrazine, while mortality rates increased with increasing concentrations of atrazine. The highest percentage mortality (83.33%) was recorded at the highest concentration of 13.75mg/l. The 96-hour lethal concentration (LC50) value of atrazine computed based on logarithm was 8.84mg/l. At exposure to acute concentrations, fish showed abnormal behaviour such as restlessness, loss of colouration, respiratory stress, erratic swimming and instant death. Histological effects observed on the gills exposed to atrazine included interstitial haemorrhage, deformed primary and secondary lamella, lesion, blanketing and blood congestion. Liver tissues showed necrosis and vacuolation of hepatocytes. Dissolved oxygen level in the test solutions that contained atrazine reduced drastically and this might have induced death in fish recorded in the study. Inference from the study revealed that atrazine may be toxic to aquatic organisms, particularly juvenile C. gariepinus. [ABSTRACT FROM AUTHOR]

A study on the population dynamics of Marble Goby (Oxyeleotris marmorata, Bleeker, 1852) was conducted to support the conservation and sustainability in Huai Kho Reservoir. Fishermen were instructed to set fishing nets monthly from January to December 2022. This study successfully collected 284 fish specimens, with lengths ranging from 115 to 236mm and an average length of 162.97± 24.60mm. The total weight ranged from 24 to 236g, with an average weight of 60.87± 31.00g. The growth performance index (ϕ) was calculated to be 3.986 per year, with an asymptotic length (L∞) of 273.00mm, and a growth coefficient (K) of 0.13. The probability of capture was determined to be L25%= 137.18mm, L50%= 144.90mm, and L75%= 163.02mm. The length-weight relationship (LWR) was found to be W= 0.02443L1.61202 (r² = 0.92). The rate of total mortality (Z) was 0.97 per year, natural mortality (M) was 0.26 per year, and fishing mortality (F) was 0.71 per year. The highest recruitment (maximum replacement rate) was observed annually from March to June, ranging from 11.63 to 18.82%. The total steady-state biomass was calculated to be 6.50 tons, with the current exploitation rate (E) rate being 0.73 (E>0.5). The results indicate that the marble goby stock was overexploited. [ABSTRACT FROM AUTHOR]

Hierarchical models can express ecological dynamics using a combination of fixed and random effects, and measurement of their complexity (effective degrees of freedom, EDF) requires estimating how much random effects are shrunk toward a shared mean. Estimating EDF is helpful to (1) penalize complexity during model selection and (2) to improve understanding of model behavior. I applied the conditional Akaike Information Criterion (cAIC) to estimate EDF from the finite‐difference approximation to the gradient of model predictions with respect to each datum. I confirmed that this has similar behavior to widely used Bayesian criteria, and I illustrated ecological applications using three case studies. The first compared model parsimony with or without time‐varying parameters when predicting density‐dependent survival, where cAIC favors time‐varying demographic parameters more than conventional Akaike Information Criterion. The second estimates EDF in a phylogenetic structural equation model, and identifies a larger EDF when predicting longevity than mortality rates in fishes. The third compares EDF for a species distribution model fitted for 20 bird species and identifies those species requiring more model complexity. These highlight the ecological and statistical insight from comparing EDF among experimental units, models, and data partitions, using an approach that can be broadly adopted for nonlinear ecological models. [ABSTRACT FROM AUTHOR]

The European sprat is a small plankton-feeding clupeid present in the northeastern Atlantic Ocean, in the Mediterranean Sea, and in the brackish Baltic Sea and Black Sea. This species is the target of a major fishery and, therefore, an accurate characterization of its genetic population structure is crucial to delineate proper stock assessments that aid ensuring the fishery's sustainability. Here, we present (i) a draft genome assembly, (ii) pooled whole genome sequencing of 19 population samples covering most of the species' distribution range, and (iii) the design and test of a single nucleotide polymorphism (SNP)-chip resource and use this to validate the population structure inferred from pooled sequencing. These approaches revealed, using the populations sampled here, three major groups of European sprat: Oceanic, Coastal, and Brackish with limited differentiation within groups even over wide geographical stretches. Genetic structure is largely driven by six large putative inversions that differentiate Oceanic and Brackish sprats, while Coastal populations display intermediate frequencies of haplotypes at each locus. Interestingly, populations from the Baltic and the Black Seas share similar frequencies of haplotypes at these putative inversions despite their distant geographic location. The closely related clupeids European sprat and Atlantic herring both show genetic adaptation to the brackish Baltic Sea, providing an opportunity to explore the extent of genetic parallelism. This analysis revealed limited parallelism because out of 125 independent loci detected in the Atlantic herring, three showed sharp signals of selection that overlapped between the two species and contained single genes such as PRLRA , which encodes the receptor for prolactin, a freshwater-adapting hormone in euryhaline species, and THRB , a receptor for thyroid hormones, important both for metabolic regulation and the development of red cone photoreceptors. [ABSTRACT FROM AUTHOR]