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Most major rivers in Europe have been dammed for hydropower or other purposes. Such river alterations have decimated natural reproduction of many migratory fish species, including that of the anadromous European whitefish, Coregonus lavaretus, which is now maintained by extensive stocking programmes. In addition to stocking, limited natural reproduction may occur downstream of dams, where peak flow bouts from the dams threaten to flush the eggs into unsuitable habitats. Here, we assessed the effects of water flow velocity and substrate coarseness on downstream drift of whitefish eggs under laboratory conditions. The experiment's two different gravel substrates retained eggs better than cobble or sand substrates; the water velocity needed for notable egg drift was higher for the gravel substrates. The results indicate that egg drift is one of the factors that should be considered when evaluating the effects of hydropower plant operations. Moreover, measures mitigating the effects of the artificial flow regimes should incorporate the type and coarseness of the riverbed's substrate. [ABSTRACT FROM AUTHOR]

Simple Summary: The Internet of Things (IoT) can improve small-scale aquaponics, a sustainable farming method that combines fish farming with plant growing in water without soil, by making the process more efficient and profitable by optimizing resource use, closely monitoring water quality, and ensuring the best conditions for both fish and plants to thrive. Aquaponics is beneficial for the environment and can help ensure a steady food supply but presents challenges for small-scale farmers due to a lack of expertise in water chemistry and system upkeep, as well as high operational costs. Identified challenges in aquaponics operation include high water and energy costs, maintaining the right balance of fish and plants, and the risk of mosquitoes breeding in the water. This systematic review offers a comprehensive guide to setting up and maintaining an aquaponics system, including choosing the right fish and plants, designing the system, monitoring water quality, and feeding the fish. The importance of knowledge sharing among farmers is also highlighted to improve aquaponics practices. The integration of IoT into these systems can reduce the need for manual work and improve the availability of information related to system control, which could facilitate further adoption and optimization of aquaponics farming practices. Aquaponics combines aquaculture and hydroponics to offer a sustainable approach to agriculture, addressing food security issues with minimal environmental harm. However, small-scale practitioners face challenges due to a lack of professional knowledge in water chemistry and system maintenance. Economic hurdles, such as operational costs and energy-intensive components, hinder the viability of small-scale aquaponics. Selecting suitable fish and plant species, along with appropriate stocking densities, is crucial. Media Bed (MB), Deep Water Culture (DWC), and the Nutrient Film Technique (NFT) are commonly used hydroponic techniques. This study outlines optimal conditions, including water quality, temperature, pH, and nutrient concentrations, essential for symbiotic fish and plant cultivation. Integrating IoT technology enhances efficiency and profitability by optimizing resource utilization, monitoring water quality, and ensuring optimal growth conditions. Knowledge sharing among practitioners fosters innovation and sustainability through collaborative learning and best practices exchange. Establishing a community for knowledge sharing is vital for continuous improvement, advancing small-scale aquaponics towards a more efficient and sustainable future. [ABSTRACT FROM AUTHOR]

Due to intensified human activities like hydropower development, biodiversity in the upper Yellow River faces severe threats. In 2019, we conducted a survey across all reservoirs in the river section from Longyangxia to Liujiaxia in the upper Yellow River, focusing on key aquatic organisms such as benthic macroinvertebrates and fish. The benthic index of biotic integrity (B-IBI) and the fish stocking index (FSI) were used to assess the river's biotic integrity. We collected 54 macroinvertebrate species with an average biomass of 1.28g/m², predominantly featuring species like Gammarus sp. and Palaemon modestus. Additionally, 39 fish species were captured, with Gymnocypris eckloni, Pseudorasbora parva, and Triplophysa pappenheimi being the most common, with an average weight of 43.27 g per individual. The B-IBI scores ranged from 1.06 to 3.04, averaging 78; the number of native fish species varied from 3 to 15 per location, resulting in an FSI score of 69. This indicated that the biotic integrity of the Longyangxia to Liujiaxia section was common yet still significantly impacted by human activities. This study highlights the impacts of human activities on the river's ecosystem and aims to guide ecological protection and restoration efforts in the upper Yellow River. [ABSTRACT FROM AUTHOR]

Simple Summary: Ecological fishery management is one of the predominant approaches to lake ecological management in China; it involves the stocking of filter-feeding fish species to mitigate algal blooms. This strategy not only enhances water quality but also yields ecological benefits by fostering the growth of fish populations, thereby offering both ecological and economic advantages. Nonetheless, there is a scarcity of works in the literature addressing the effects on fish community dynamics and diversity in lakes subsequent to the cessation of ecological fishing practices. This study focuses on the initial changes observed in fish community composition and diversity following the cessation of an ecological fishery project in Qilu Lake, an eutrophic shallow lake situated in China. Ecological fishery projects aim to improve the water quality of eutrophication lakes by stocking filter-feeding fish species that feed on algae. The findings indicate a significant decline in the number of fish species, average individual size, and species diversity index following the cessation of fisheries-related activities (including fish stocking and fishing activities) due to the termination of the ecological fishery project in the lake. To preserve fish biodiversity and enhance water quality in Qilu Lake, it is recommended that policies be implemented to sustain the implementation of ecological fisheries projects, restore habitats for native fish species, and regulate the proliferation of small fish populations. The Qilu Lake is an eutrophic shallow lake located in Yunnan Province, China. An ecological fishery project was initiated in the lake from 2011 to 2021 to introduce filter-feeding fish species that feed on algae, with the aim of improving water quality. In January 2022, when the ecological fishery project expired, all fisheries-related activities (including fish stocking and fishing activities) ceased in the lake. To comprehensively evaluate the initial alterations in fish community structure and diversity resulting from the fishing cessation in the Qilu Lake, the present study conducted field surveys within the one year before the fishing cessation (referred to as BFC) and the one year after the fishing cessation (referred to as AFC). A total of twenty-one fish species were collected, including four native species. Four species were recorded in the lake for the first time, including Pelteobagrus fulvidraco, Pelteobagrus vachelli, Paramisgurnus dabryanus, and Hyporhamphus intermedius. The number of fish species decreased from 21 to 13 following the fishing cessation. The fishes collected in both BFC and AFC are mainly omnivorous-feeding and of bottom-dwelling habits. The mean size of the fishes in the AFC sample shows a significant decrease compared to those in BFC. After the fishing cessation, the Shannon–Wiener diversity index and Margalef richness index of the fish slightly declined. The fish community structure of the Qilu Lake exhibits a high degree of similarity to adjacent lakes in central Yunnan. Our study demonstrates a significant shift in the fish community of the Qilu Lake following the fishing cessation, one which may adversely impact the stability of the lake ecosystem. To enhance fish species diversity in the Qilu Lake, it is recommended that policies be implemented to promote the ecological fishery project and improve habitat restoration for native fish species, while also regulating fish community structure. [ABSTRACT FROM AUTHOR]

The number of birds or their total live weight in relation to a given area is known as stocking density; higher stocking densities will cause more stress to the birds, which may have an impact on their physiological state, productivity, carcass quality, growth performance, immunity, metabolism, and meat quality. The present study aimed to investigate the potential impact of 2 different stocking densities on growth performance, carcass characteristics, meat quality, serum, and expression of Insulin like growth factor-1 (IGF-1), muscle regulatory genes expression and serum biochemical indicators of broilers supplemented with essential oils (EO). In total, 784-day-old chicks of Ross 308 were randomly assigned into 4 different groups with 7 replicates for each: Normal feed (no essential oils [EO] added) and normal stocking as 9 bird/m2, (NSD). Normal feed (no essential oils [EO] added) and high stocking as 14 bird/m2, (HSD). Feed with essential oils (Digestarom DC® 150 g/Ton of feed) and normal stocking as 9 birds/m2, (NSD + EO). Feed with essential oils (Digestarom DC® 150 g/Ton of feed) and high stocking as 14 birds/m2, (HSD + EO) for 35 days. Bodyweight was recorded at the beginning of the trial and then at the end of each week, feed intake was recorded at the end of each week as well. A total of 28 birds (7 birds per treatment) birds were slaughtered at 35 days of age to evaluate each parameter. The HSD group had the lowest (P < 0.05) feed intake. The NSD groups showed the highest (P < 0.05) body weight gain compared to HSD groups. The HSD + EO had lower adjusted FCR (P < 0.05) compared to HSD. The legs % was the highest (P < 0.05) for NSD group, while HSD + EO had the highest (P < 0.05) Fat Pad percentage. Moreover, HSD had the highest CL%, and the lowest WHC and Warner–Bratzler shear force. For biochemical indicators, (IGF-1) was the lowest (P < 0.05) HSD group. Also, Mammalian Target of Rapamycin (mTOR) and Aspartate Aminotransferase (AST) were higher (P < 0.05) in the EO supplemented groups. Regarding gene expression, the results showed that Myogenin (MyoG) and IGF-1 were lower in HSD while MSTN was higher in the same group, (P < 0.05). In brief, essential oil supplement has improved the performance of broilers under high stocking density situation. [ABSTRACT FROM AUTHOR]

Basket height and stocking density are crucial and related factors for successful commercial sea urchin aquaculture, but these factors have not been definitively determined for production of Tripneustes gratilla. This study investigated the effects of varying basket heights (deep 30 cm vs. shallow 15 cm) and stocking densities (4, 6 and 8 kg.m−2 or 13, 19 and 24% coverage of available basket surface area) on aquacultural production of T. gratilla. Contrary to previous suggestions, reduced consumption was identified as the cause of decreased production in deeper baskets. Consumption was significantly higher in shallow baskets than deep baskets for both the fresh seaweed, Ulva lacinulata, (W = 38, p = 0.026) and formulated feed (W = 76.5, p = 0.007). Consequently, baskets of approximately 15 cm deep are recommended to enhance production of T. gratilla and possibly other urchin species. Two subsequent trials assessed production of T. gratilla at different stocking densities. Trial 1 aimed to maximize urchin size over a three-month grow-out period using fresh U. lacinulata, while trial 2 focused on enhancing gonad production over two months using formulated feed. Although greater stocking density significantly reduced the specific growth rates of individual urchin mass in both trials (p < 0.044), there was no significant impact on mortality, net production or gonad size and quality. The variations in growth rates were attributed to spine loss resulting from negative behavioural interactions (F2, 9 = 9.551; p = 0.005). Based on the objectives of both grow-out and gonad-enhancement phases, we recommend a stocking density of approximately 20% coverage. [ABSTRACT FROM AUTHOR]

Water quality and growth of Litopenaeus vannamei were monitored at different stocking densities in a zero-water exchange nursery system inoculated with chemoautotrophic bacteria and limited organic carbon (OC) addition. Shrimp (∼3.4 mg) were divided into four groups of 200 PL/m2 (T200), 500 PL/m2 (T500), 1000 PL/m2 (T1000), and 1500 PL/m2 (T1500). At the end of the study, the water temperature, pH, salinity, dissolved oxygen, oxidation-reduction potential, and dissolved oxygen saturation were within the optimal range. Total dissolved solids and electrical conductivity were lower in T200. The highest concentrations of free CO2 were observed in T1500. The results also revealed higher levels of alkalinity in T1500 compared to T500 and T1000. Notably, TAN was lower in T200 than in T1000 and T1500. Nitrite nitrogen (nitrite-N) and nitrate nitrogen were also lower in T200. Furthermore, TAN and nitrite-N levels rapidly elevated upon OC addition. Interestingly, nitrite-N levels exhibited a decrease whenever OC application was terminated. Total heterotrophic and Vibrio sp. bacteria in water samples were not affected by study groups. Regarding growth performance, T200 had significantly better final weight, weight gain, specific growth rate, and weekly growth rate. However, T1500 had the highest shrimp yield (kg/m3 or kg/m2). In conclusion, OC in the chemoautotrophic system interferes with the nitrification cycle, disrupts the effective conversion of nitrogen, and leads to further deterioration of water quality and shrimp growth performance at higher stocking densities. In this system, shrimp at the lowest density (200 PL/m2) reached the highest final weight and survival. [ABSTRACT FROM AUTHOR]

The article presents the discussion on critical role of aquaculture in global food security, noting its substantial growth to 87.5 million tonnes, which represents nearly half of global aquatic animal production. Topics include the rapid expansion of aquaculture's share of global food production, the significant contributions of South Asia to global fish production; and the shifting dynamics from marine to inland fisheries, particularly in India and Bangladesh.

This study sought to assess the possibility of genetically improving the performance of the African catfish using triploidy techniques. The experiment was carried out using Completely Randomized Design (CRD) with varied temperatures, time spent before shock after fertilisation, and durations of the shock for the triploid production experiment and four treatments replicated thrice for the culture experiment. Fertilised eggs from each female parent stock were subjected to either cold or heat shock treatments. The result showed a significant (p<0.05) increase in the hatching time and survival of the fertilized eggs subjected to different cold and heat shock treatments as compared to the control which recorded the shortest hatching time of 22.48 ± 0.00 hours. The temperature regime of 2oC recorded the highest approximate yield of triploids (98.33 ± 1.66%), while the prolonged duration of the shock of 30 minutes at the temperature regime of 3oC significantly increased (p<0.05) triploid yield. Comparatively, triploids significantly gained more weight, had an increased growth rate, and grew longer than the diploid counterparts with an average of 11.22 ± 1.07 g, 0.013 ± 0.001%, and 21.49 ± 0.47 cm respectively. The highest comparative cost of the diet of 1000 catfish juveniles occurred in triploids with a stocking density of 7 fishes/m² (N14,132.50). However, the seed, feed, and variable costs consistently decreased with increasing stocking densities across the ploidies. It is therefore concluded that the triploids were superior in both production attributes and cost benefits. [ABSTRACT FROM AUTHOR]

Lactococcus garvieae has recently been identified and listed as one of the causative agents of hyperacute hemorrhagic sepsis in fish. In intensive recirculating aquaculture systems where there are high fish densities and minimal water changes, not only will it be conducive to the growth of bacteria, but Cryptocaryon irritans as a marine protozoan fish parasite is also prone to appear. This study reports the disease status of Trachinotus ovatus in an aquaculture area in Yangjiang City, Guangdong Province. Through the diagnosis of clinical symptoms of the diseased fish, identification of specific primers, 16s rRNA sequences phylogenetic tree analysis, physiological and biochemical identification, and observation of histopathological sections, the result of the experiment is that the mass death of T. ovatus is caused by a mixture of L. garvieae and C. irritants infections. Subsequently, regression infection experiments were performed to verify Koch's law. It was confirmed that the pathogen had strong virulence to T. ovatus. This is the first time that the co-infection of L. garvieae and C. irritans to T. ovatus was found in South China. The research results of this experiment have certain enlightenment significance for the epidemic trend of fish diseases in relevant sea areas. [ABSTRACT FROM AUTHOR]

Lake Jošava (Croatia) is a shallow reservoir surrounded by agricultural land. In the present study, the trophic cascade was tested by examining the effects of stocking with common carp on plankton and periphytic microphytes. Before stocking, the phytoplankton community was dominated by the chrysophyte Synura uvella. In the epilithon and epiphyton, the predominant diatoms were prostrate, stalk-forming, and motile taxa representing an important food source for adult copepods. After stocking, phytoplankton biomass declined and the community shifted towards small centric diatoms, allowing the small-bodied zooplankton to exploit them. The lower biomass of adult copepods allowed rotifers to proliferate and exploit phytoplankton, while small cladocerans and nauplii fed primarily on epilithon. One month after stocking, phytoplankton was dominated by cryptophytes, small centric diatoms and chlorophytes, which were an important food for rotifers, while none of the zooplankton groups showed a significant relationship with the epilithic and epiphytic communities. By the end of the experiment, food was scarce due to reduced biomass of autotrophs, and zooplankton possibly began to feed on other sources. Our results add to the knowledge about the trophic cascade hypothesis in small shallow reservoirs. [ABSTRACT FROM AUTHOR]

When investigating potential causes of apparent declines in European brown trout angling catch rates over recent decades, fisheries management procedures are rarely considered. Using a 20‐year dataset of brown trout stocking and angling catch rates, we found a significant decline in brown trout angling catch rates in streams of East Bohemia, Czechia, were well predicted by a reduction in the number of brown trout stocked at catchable size (i.e. age‐3+). Increased stocking of smaller sized brown trout, and recent sporadic efforts to stock large brown trout, had no effect on catch rates. Our findings suggest that brown trout catch rates were related to ‘put‐and‐take’ stocking, in which non‐native rainbow trout gradually replaced brown trout in both stocking and catches. Our study stresses the importance of considering historical fisheries management, a sometimes‐neglected factor, when studying angling catches of economically important species. [ABSTRACT FROM AUTHOR]

Under the direction of Salahaddin University in Erbil's College of Agricultural Engineering Sciences, study was carried out to investigate how local quail performed biochemically, histologically, and immune-wise when varied levels of Salvia indica (SI) additive were added at high stocking density. For a 42-day trial, 216 one-week-old local quails were divided into four treatments at random, with three replicates for each treatment, in cages measuring 60 by 30 by 25 centimeters. The following was the design of the feed treatments: Positive control (12 birds/replicate), Negative control 20 birds per replicate at a high stocking density, 20 birds per replicate plus 0.2% of SI additive, and 20 birds per replicate plus 0.4% of SI additive. When compared to a negative control, the results indicated that 0.4% SI supplements with high stocking density produced the best live body weight and weight gain. When compared to positive and negative controls, the cholesterol level of female quails considerably (P<0.05) decreased in both SI with high stocking density; however, no significant variations were seen with either of the SI additives with high stoking density. Furthermore, when compared to the positive control, the LDL content in female quails was considerably (P<0.05) reduced by both supplements of SI with high stocking density and negative control. When treated with SI, the height of the jejunum villus was significantly (P<0.05) higher than when treated with both positive and negative controls. The size of Fabricius follicles was significantly (P<0.05) enhanced by the addition of SI treatments, but no significant difference was seen between the two SI additives with high stocking density. In summary, adding Salvia indica to a diet with high stocking density enhanced the quail population's biochemical markers, immunological response, and jejunum histology. [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]

Understanding recruitment, the process by which individuals are added to a population or to a fishery, is critical for understanding population dynamics and facilitating sustainable fisheries management. Important variation in recruitment dynamics is observed among populations, wherein some populations exhibit asymptotic productivity and others exhibit overcompensation (i.e., compensatory density‐dependence in recruitment). Our ability to understand this interpopulation variability in recruitment patterns is limited by a poor understanding of the underlying mechanisms, such as the complex interactions between density dependence, recruitment, and environment. Furthermore, most studies on recruitment are conducted using an observational design with long time series that are seldom replicated across populations in an experimentally controlled fashion. Without proper replication, extrapolations between populations are tenuous, and the underlying environmental trends are challenging to quantify. To address these issues, we conducted a field experiment manipulating stocking densities of juvenile brook trout Salvelinus fontinalis in three wild populations to show that these neighboring populations—which exhibit divergent patterns of density dependence due to environmental conditions—also have important differences in recruitment dynamics. Testing against four stock‐recruitment models (density independent, linear, Beverton‐Holt, and Ricker), populations exhibited ~twofold variation in asymptotic productivity, with no overcompensation following a Beverton‐Holt model. Although environmental variables (e.g., temperature, pH, depth, substrate) correlated with population differences in recruitment, they did not improve the predictive power in individual populations. Comparing our patterns of recruitment with classic salmonid case studies revealed that despite differences in the shape and parameters of the curves (i.e., Ricker vs. Beverton‐Holt), a maximum stocking density of about five YOY fish/m2 emerged. Higher densities resulted in very marginal increases in recruitment (Beverton‐Holt) or reduced recruitment due to overcompensation (Ricker). [ABSTRACT FROM AUTHOR]

A stochastic model was developed to analyze Crassostrea virginica production when cultivated at three stocking densities, defined as the area occupation (50, 75, and 100%) in Nestier-type trays, using juvenile oysters with an initial size (height) of 29.40 ± 0.18 mm. A 25-week grow-out was first conducted in the Rio Lagartos lagoon, showing that final oyster size was inversely related to density (P < 0.05), ranging from 61.87 mm (100% density) to 68.00 mm (50% density). At the same time, mortality was negligible (lower than 1.0%). The environmental conditions in the lagoon were stable, and the oyster growth rate positively correlated with water temperature and pH. Low pH was associated with slow oyster growth, possibly as an adverse effect of acidic conditions on the oyster shell formation. The model indicated that, for an initial 100,000 oyster population, the maximum production (oyster dozens) is obtained after 20 weeks (8310 at 50% density) and 25 weeks (8250 at 75%, and 6670 at 100% density). There was a 100% probability of oysters reaching a minimum commercial size (MCS) of 60.00 mm when using the 50 and 75% densities and 80.6% when using 100%. The model estimated that, for the maximum density, extending the grow-out up to 32 weeks would allow reaching MCS with 100% probability, although this should be experimentally confirmed. The random variability of oyster production in 50 and 75% densities was minimal, while at 100% density, it was extremely high. A sensitivity analysis indicated that for 50 and 75% densities, the main stochastic elements influencing production, are related to oyster mortality, while at 100% density, they are related to oyster growth. [ABSTRACT FROM AUTHOR]

Dietary uptake is key for transferring potentially toxic contaminants, such as mercury (Hg) and essential dietary nutrients, such as polyunsaturated fatty acids (PUFA), to consumers at higher trophic levels of aquatic food webs. We evaluated the role of diet sources for Hg bioaccumulation and PUFA retention in fish across lake food webs in seven Swedish lakes and two Chinese reservoirs. Fish total Hg (THg) and methyl-Hg (MeHg) differed greatly between the two countries: the Chinese fish contained less than 300 ng g−1 dry weight (d.w.) THg with less than 50% as MeHg, versus the Swedish fishes which contained approximately 2000 ng g−1 d.w. THg and nearly 100% as MeHg. Fatty acids enrichment of linoleic acids (LIN) were more prevalent in the Chinese fishes regardless of size (p < 0.05). Here we examined food web length, fish growth rates, and fatty acids patterns in relation to the quality of fish as a food source for both Hg and FA. Contrary to the expectation that biodilution of Hg throughout the food chain would explain these differences, a more complex picture emerged with high levels of Hg at the base of the food web in the Chinese reservoirs, a decoupling of fatty acid and Hg bioaccumulation, and a major role for both fish stocking and fish feed. It is hoped that this work will provide a nuanced picture of fish quality as a food source in different ecosystems. [ABSTRACT FROM AUTHOR]

In shrimp farming, the development of alternative production systems, such as fermented products, can help reduce the high dependence on artificial diets and ensure more sustainable growth. The "synbiotic system" typically uses low stocking densities in traditional earth ponds. To increase profitability, the tendency is to increase stocking densities, especially in small production units. The objective of the following work was to use the "synbiotic system" in different stocking densities, analyzing the water quality, the microorganisms present, the proximal composition of the formed bioflocs and the zootechnical performance. For this, 12 tanks with an area of 35 m2 each were used. Stocking densities were 30, 60, 90 and 120 shrimp/m2. Fertilization was carried out for seven days before the shrimp stocking and then every two days until the end of the experiment. The experiment lasted 45 days, and no water was renewed. Significant differences were observed in several quality parameters, including alkalinity, nitrate, total suspended solids, and turbidity. However, no significant differences were found in the proximal composition of the formed bioflocs. The presence of microorganisms throughout the experimental period indicated the effectiveness of adding fermented rice bran for nutrient assimilation. Furthermore, significant differences were observed in the final weight, feed conversion rate and productivity. The ability of the synbiotic system to provide food supplementation, control water quality and present satisfactory zootechnical performance was demonstrated, proving to be efficient in the cultivation of Litopenaeus vannamei. [ABSTRACT FROM AUTHOR]

The demand for marine living resources is increasing at an unprecedented scale because of the need for continuous food provision to the world’s population. The potential of already exploited fish stocks to meet this demand is limited. Therefore, mesopelagic fish have recently become attractive potential targets for fisheries because of their vast conjectured biomass. However, the role of mesopelagic fish in marine ecosystems is poorly understood. Before developing commercial exploitation plans, the relationship between mesopelagic fish and other groups in the marine food web and biogeochemical cycles should be analyzed quantitatively. In this study, we coupled a one-dimensional biogeochemical model (North Atlantic Generic Ecosystem Model) with a higher-trophic-level food web model (Ecopath with Ecosim) for the Sargasso Sea in the North Atlantic to investigate changes in carbon export and trophodynamics under two mesopelagic fish harvesting scenarios. The coupled model represented the marine food web from plankton to fish and mammals, vertical carbon export dynamics, and their interaction with fisheries. The results showed that when mesopelagic fish were not harvested, they contributed approximately 6% of the total carbon export in the surface waters, but up to 40% of the total carbon export below 400 m. Harvesting mesopelagic fish altered the energy transfers within the food web as well as to fisheries. The ecological footprint of fisheries increased significantly. Due to declining competition in the food web, epipelagic fish increased to exert elevated grazing pressure on phytoplankton; hence, phytoplankton-mediated carbon export decreased. The total carbon export decreased by 14% due to the decreases in mesopelagic fish- and phytoplanktonmediated carbon exports. The simulated increase in zooplankton- and nonmesopelagic fish-mediated carbon exports (up to 92% and 96%, respectively) did not compensate for the total decrease in carbon exports under harvesting scenarios. The findings of this study highlighted that mesopelagic fish not only have a direct control on carbon dynamics by their metabolic releases and diel vertical migration, but also strong indirect controls through prey-predator interactions within the food web. Therefore, the implications of harvesting mesopelagic fish should be carefully considered from a holistic perspective. [ABSTRACT FROM AUTHOR]

Understanding the mechanism by which non‐native fish species integrate into native communities is crucial for evaluating the possibility of their establishment success. The genus Pangasianodon, comprising Pangasianodon gigas and Pangasianodon hypophthalmus, has been introduced into reservoirs, which are non‐native habitats, for fishery stock enhancement. P. gigas and P. hypophthalmus often successfully establish and co‐occur in several Thai reservoirs, but there is little information on differences in food resource use between the two species. To investigate the trophic niche width of P. gigas and P. hypophthalmus in a Thai reservoir, we conducted stable carbon and nitrogen ratio (δ13C and δ15N) analyses. We examined the degree of individual specialization in both species using the δ13C and δ15N values of muscle and liver tissues, which provides long‐ and short‐term diet information. The isotopic niches did not overlap between P. gigas and P. hypophthalmus. The δ15N value of P. gigas was significantly higher than that of P. hypophthalmus, whereas the δ13C value did not significantly differ between the two species. The isotopic niche sizes were larger in P. hypophthalmus than in P. gigas. Individual specialization was observed in P. hypophthalmus but not in P. gigas, indicating that intraspecific variation in food resource use was larger in P. hypophthalmus compared to P. gigas. These findings suggest that trophic niche partitioning was one of the factors facilitating the establishment success of P. gigas and P. hypophthalmus in a reservoir, but the establishment process may differ between the two species. [ABSTRACT FROM AUTHOR]

Microalgal density is one of the factors affecting bioremediation efficiency, but literature on the density that efficiently removes nitrogen and phosphorus from aquaculture wastewater is still very limited. Thus, this study was conducted to optimize the density of Isochrysis galbana, Nannochlorum sp., and Tetraselmis tetrahele to efficiently remove inorganic N (NH3-N, NO2-N) and P. Three densities such as low, medium, and high with an optical density at 680 nm of 0.1, 0.2, and 0.3, respectively, were evaluated for 12 days. Results showed that medium density was good for Isochrysis galbana and Nannochlorum sp. in the removal of both N and P with rates reaching 97.93% and 84.07%, 94.25% and 93.39%, and 59.39% and 71.65% for NH3-N, NO2-N, and P, respectively. For Tetraselmis tetrahele, the low density efficiently removed N, while the high density effectively removed P with the highest removal of 99.16%, 97.5%, and 51.55% for NH3-N, NO2-N, and P, respectively. Specific growth rates of Isochrysis galbana and Tetraselmis tetrahele were affected by density; the lower the densities, the higher their growth rates. The three densities did not differ significantly in Nannochlorum sp. Isochrysis galbana and Nannochlorum sp. biomass productivity were high in medium and high densities, while low and medium densities for Tetraselmis tetrahele. Overall, the optimization of microalgal density is beneficial in the efficient removal of nitrogen and phosphorus from aquaculture wastewater. [ABSTRACT FROM AUTHOR]

Identifying a fish's artificial or natural origin is crucial for stock enhancement assessments. In this study, we collected specimens of hatchery (including the early fry, reared, and released juveniles) and wild mangrove snapper Lutjanus argentimaculatus to explore the feasibility of using δ13C and δ15N values in scales as a non-lethal alternative to muscle tissues for discriminating between hatchery and wild origins. The results showed scales generally enriched in δ13C value and relatively consistent in δ15N value compared to muscle. Significant correlations were found between the two tissues for both δ13C and δ15N values (R2 = 0.80–0.88). Based on the isotopic composition of the scale core, individuals with different origins could be effectively discriminated, achieving a classification success rate of 77.6%. The random forest analysis revealed that a δ13C value of −15.8‰ could be a reference for determining the hatchery and wild origins of mangrove snapper. This study provides an isotopic approach for assessing the benefit of stock enrichment in mangrove snapper. It highlights the importance of regular sampling and scales analysis to expand fishery management and conservation practices. [ABSTRACT FROM AUTHOR]

Successful aquacultural production of juvenile fish requires that the optimal rearing conditions be applied. However, for many fish species, there is a significant knowledge gap concerning these conditions. In this study, we evaluated the effects of stocking density on the survival and growth of brown meagre, Sciaena umbra (L.), during rearing trials in an experimental hatchery. This research forms part of a feasibility project to improve the aquacultural production of brown meagre. Four initial larval density treatments (5, 10, 30, and 70 larvae per L) were established. At 0, 9, 17, 22, and 25 days post-hatching, we measured the total length, coefficient of variation in length, and specific growth rate. The physicochemical water parameters remained at satisfactory levels for fish culture throughout the experiment. Lower densities promoted better growth in terms of total length, specific growth rate, and survival. We observed a significant negative correlation between larval density and length growth/survival. Thus, the low larval density treatment yielded the highest survival (48.5% ± 3.46%), growth in final total length (11.9 ± 1.09 mm), and specific growth rate (5.13% ± 0.39% per day). Increased stocking density therefore negatively affects growth and survival, reduces homogeneity, but increases the production of S. umbra larvae. This study helps identify optimal aquaculture conditions for maximizing the production of juvenile S. umbra for ecological restoration. [ABSTRACT FROM AUTHOR]

Understanding stakeholder diversity can help natural resource managers tailor activities to achieve greater stakeholder satisfaction. Stakeholder diversity can be described by the concept of recreational specialization. Centrality-to-lifestyle, one subdimension of specialization that measures the psychological importance of a recreational activity to an angler, has been shown to explain many human dimensions and behaviors of recreational fishers and to correlate with preferences for management actions. We surveyed 9911 anglers in Florida, USA to examine how centrality-to-lifestyle relates to preferences for stocking and other management tools. We found that most anglers support stocking and that anglers of greater centrality-to-lifestyle had more positive views toward stocking than less central anglers. Participants, regardless of level of centrality-to-lifestyle, generally preferred stocking of one species, Florida largemouth bass (Micropterus salmoides), and they preferred habitat management above stocking, with no relation to centrality. The results suggest stocking can improve the satisfaction of anglers of all commitment levels, but habitat improvement could do so even more. Managers might consider prioritizing habitat management over stocking in systems where natural recruitment is ample to increase overall angler satisfaction, and where the anglers will, on average, support such actions independent of the degree of centrality. [ABSTRACT FROM AUTHOR]

The Pasur-Sibsa and Baleshwari River Estuary (PSBE) is the longest estuary located in the southwest part of Bangladesh on the Ganges-Brahmaputra delta which flows into the Bay of Bengal. The study was conducted to investigate the diversity and abundance of the zooplankton from three gateways (S1 station: Pasur river gateway; S2 station: Sibsa river gateway and S3 station: Baleshwari river gateway) in the PSBE from July 2022 to December 2022. Water samples were collected from these gateways using plankton net (55 µm mesh size) and preserved for analyzing in the laboratory. A total of 34 species of zooplankton belonging to 9 orders and 17 families were documented. The dominant orders were Calanoida and Dendrobranchiata, covering 59.52% and 18.20%, respectively. Acartia bilobata was the dominant species, while Sagitta sp. was the inferior species throughout the gateways. The Pasur river estuary gateway showed the highest percentage of abundance, accounting for 36.39% of the total individuals. The study calculated the Shannon-Wiener Diversity Index, Simpson's Dominance Index, Simpson's Index of Diversity, Margalef's Richness Index, and Evenness ranged from 1.33 to 1.43, 0.24 to 0.30, 0.70-0.76, 1.11 to 1.21, and 0.74-0.80, respectively. The results showed that the zooplankton composition was rich in the S1 station, which serves as a good indicator of marine productivity like zooplankton. The density of zooplankton in a body of water is indicative of the fish stocking rate. [ABSTRACT FROM AUTHOR]

Gamma-aminobutyric acid (GABA) is a non-protein amino acid that is found in the brain and central nervous system of animals as an inhibitory neurotransmitter. It has been shown to have a variety of physiological functions, including stress reduction and immune enhancement. This study investigated the effects of dietary supplementation with GABA on growth, serum biochemistry, innate immunity, and disease resistance in juvenile olive flounders (Paralichthys olivaceus) challenged with Edwardsiella tarda under high-stocking density. A control diet and three experimental diets were prepared, with 150 mg/kg (GABA150), 200 mg/kg (GABA200), and 250 mg/kg (GABA250) of GABA added to each diet, respectively. Each experimental diet was fed to olive flounders in triplicate with an initial weight of 12.75 g ± 0.3 g in 40 L tanks at two stocking densities: normal density (20 fish/tank) and high density (40 fish/tank). After 8 weeks of the feeding trial, growth, feed utilization, whole-body proximate compositions, blood analyses, and non-specific immune responses were measured, and challenge tests were performed. There were no significant differences in the weight gain (WG) and specific growth rate (SGR) among fish fed the GABA-supplemented diets at the two stocking densities. However, the normal-density groups showed significantly higher WG and SGR than the high-density groups (p < 0.05). There was no significant difference in feed efficiency and protein efficiency ratio among all groups. Moreover, there was no significant difference in the whole-body proximate composition analysis (p > 0.05). There were no significant differences in cortisol levels in fish fed the GABA at both densities, but the high-density group showed a significantly higher cortisol than the low-density group. Blood GABA significantly increased in a dose-dependent manner regardless of the density groups (p < 0.05). Superoxide dismutase activity showed significantly higher levels than the control group, but there was no significant effect of the stocking densities in fish fed the GABA diets (p < 0.05). Myeloperoxidase activities in fish fed the GABA200 and GABA250 diets showed significantly higher levels at both of the stocking densities (p < 0.05). Lysozyme activity was significantly higher in the GABA150 group than in the CON, GABA200, and GABA250 groups (p < 0.05). After 15 days of challenge tests with Edwardsiella tarda, the cumulative survival rates of the GABA150, GABA200, and GABA250 groups were significantly higher than that of the CON group (p < 0.05). The results suggested that the optimal dietary GABA level for juvenile olive flounder culture is 150 mg/kg, regardless of rearing density, to enhance growth, immunity, and disease resistance. [ABSTRACT FROM AUTHOR]

Feed conversion ratio (FCR) is widely used as a measure of feed use efficiency in commercial aquaculture production and research. Surprisingly, little work has focused on the factors that affect FCR in plankton‐based, commercial ponds despite the widespread use of FCR as a production metric. Proposals to use FCR as a numeric standard for environmental regulation (mandatory or voluntary) raise questions as to whether FCR meets the reliability and consistency requirements of a good metric, and whether it would lead to desired behavioral changes. This article summarizes FCR data from university research verification programs conducted on US catfish farms and databases developed from commercial farm records. The relevant research literature is synthesized with respect to factors that affect FCR. US catfish is used as a case study because pond‐level data from verification trials (Extension/research‐led on‐farm trials of best available science) and commercial farm records are available. While specific to US catfish production, the analysis provides insights into factors affecting FCR that likely apply to other pond‐based aquaculture species. Commercial verification of pond data showed (1) significant variation in FCR (coefficients of variation from 1% to 47%) among ponds with similar stocking, feeding, and aeration rates; (2) significant effects of survival on FCR; and (3) no significant effects on FCR of yield, feed type, management, or production system. Improvements in FCR would occur with improved survival that requires improved management of federally protected fish‐eating bird populations and development of additional, effective vaccines for diseases. FCRs were found to not exhibit the degree of reliability and consistency required for use as an effective metric or numeric standard for regulatory purposes. Use of FCR for mandatory or voluntary regulation is unlikely to lead to behavioral changes by farmers. [ABSTRACT FROM AUTHOR]

The frequency of freshwater cyanobacterial blooms is increasing globally due to climate change and eutrophication, particularly in reservoirs. Reservoir ecosystems exhibit unique characteristics, and there is a complex relationship between factors such as light, temperature, nutrient salts, hydrology, and algal growth. The impact of the other factors on algal growth varies significantly among different reservoirs. Thus, it is crucial to assess the effectiveness of various algal control measures implemented in different reservoirs. This study conducted a comprehensive assessment by establishing a eutrophication model for the Shanzi Reservoir in Fuzhou City. The model incorporated meteorology, hydrology, carbon dynamics, nutrient cycling, and biological communities. The effectiveness of diverse management measures was systematically evaluated. The findings demonstrate that increasing the water level, reducing nutrient salts in sediments, and implementing ecological fish stocking effectively suppressed algal growth to varying degrees and improved nitrogen and phosphorus levels. Lower water levels and ecological fish stocking had a significant impact on algal reproduction, while sediment reduction had a minimal effect. Conversely, lower water levels and ecological fish stocking did not significantly improve nitrogen and phosphorus concentrations in the reservoir, whereas sediment reduction had a noticeable effect. Consequently, the management strategies for the Shanzi Reservoir should prioritize external control measures and the implementation of ecological fish stocking. [ABSTRACT FROM AUTHOR]

Background: Malaria treatment is faced with the challenge of access, affordability, availability, and quality of antimalarial medicines. Affordable medicines facility-malaria (AMFm) program and subsequently Co-payment mechanism were developed to help increase access to quality assured Artemisinin-based combination therapies (ACTs) in seven countries in sub-Saharan Africa. We explored through a qualitative study, experience of healthcare personnel on Co-payment mechanism and the implication on its use in private drug outlets in Uganda. Method: Private drug outlets that reported stocking antimalarial agents in moderate-to-high and low malaria transmission settings were purposively selected for inclusion in the study. In each drug outlet, data was collected from a pharmacist/dispenser through key informant interview. The interview was done using a key informant interview guide which covered the following areas, (i) sociodemographic characteristics, ii) awareness of healthcare personnel on the co-payment mechanism, (iii) awareness of healthcare personnel on quality assured artemisinin combination therapies (QAACT), (iv) antimalarial stocking in private drug outlets, (v) antimalarial dispensing prices, (vi) considerations made while stocking, and pricing antimalarial agents, vii) challenges in antimalarial dispensing, and (viii) access to antimalarial agents in private drug outlets. Data was managed using Atlas.ti and analyzed using framework methodology. Results: Data was collected from 25 key informants (12 pharmacists and 13 dispensers). Five themes emerged following data analysis, (i) antimalarial stocking influenced by price and client demand, (ii) access and purchasing behavior of drug outlet clients, (iii) basis of dispensing antimalarial agents in private drug outlets, (iv) awareness of QAACT, and (v) awareness of Co-payment mechanism. None of the study participants was aware of the existence of Co-payment mechanism and QAACT in the private sector. Duocotecin brand of ACTs was the most mentioned and dispensed ACT among the study participants in private drug outlets. Nearly all the pharmacists/dispensers said that many clients who request to purchase ACTs don't come with a prescription and prefer buying cheaper antimalarial agents. Study participants reported stocking and selling both ACTs and non-ACT antimalarial agents in the drug outlets. Pharmacists/dispensers in the drug outlets reported that most clients could not afford buying a full dose of an ACT. None of the study participants considered using Co-payment mechanism while stocking ACTs in the drug outlets. Conclusion: There is lack of awareness and utilization of Co-payment mechanism in stocking, pricing, and dispensing of ACTs among pharmacists/dispensers in private drug outlets in Uganda. The antimalarial dispensing in drug outlets was mostly based on prescriptions, clients' preferences, and medicine affordability. The Ministry of Health needs to create demand for Co-payment mechanism through public awareness campaigns, training of healthcare personnel and behavior change communication in the private sector. [ABSTRACT FROM AUTHOR]

Simple Summary: Simple Summary: The first 16 weeks of life for a laying hen is the pullet phase. Experiences and management during this phase are critical for the long-term success of a hen, but few studies have evaluated pullet management in cage-free systems. This study evaluated the effects of two density or space allotments and two pullet strains in cage-free systems. Bird condition, physiology, immunology, and production parameters were evaluated. Stocking density only affected the size of one immune organ, the bursa of Fabricius. The relative bursal weight was higher in the low-density group. The feed conversion rate was improved in the low-density group for both strains. The brown strain had decreased uniformity and worse tail and total feather coverage at the high-stocking density. The white strain had improved uniformity and worse tail and total feather coverage at the low-stocking density. The majority of parameters evaluated had strain and age main and/or interaction effects only. Ultimately, cage-free pullets had limited negative effects at the high and low-stocking densities used. Management choices during the pullet phase can affect behavior, welfare, and health later in life, but few studies have evaluated the pullet phase, particularly in extensive housing systems. This study was a 2 × 2 factorial randomized complete block design (RCBD) with two strains and two stocking densities. The Lohmann LB-Lite and Lohmann LSL-Lite were housed on the floor at high-stocking density (619–670 cm2/bird) and low-stocking density (1249–1352 cm2/bird), which changed with age from 2 to 16 weeks of age (WOA). Bird-based measures of appearance, blood parameters, organ measurements, and production values were evaluated. Stocking density alone affected (p < 0.05) only relative bursal weight (% of body weight)—3.32% in the low-density versus 3.08% in the high-density group. High-stocking density was correlated with decreased uniformity (high—89.33 ± 0.24%; low—90.41 ± 0.24; p < 0.02) and worse feather coverage in the brown strain. High-stocking density was correlated with greater uniformity (High—90.39 ± 0.24%; Low—88.47 ± 0.24%; p < 0.001) and better feather coverage in the white strain. This study's feed conversion ratio (FCR) was improved by 0.07 in the low-stocking density for both strains. The remaining parameters were affected by strain and age only. Thus, while stocking density effects vary slightly depending on the strain used, cage-free pullets had limited negative effects at both the high and low-stocking densities tested in this study; there were few to no changes in the numerous bird-based welfare parameters tested. [ABSTRACT FROM AUTHOR]

Crassostrea is the most farmed oyster genus worldwide and has significant economic and social impacts with environmental benefits. Hatchery oyster seed production is a highly costly phase, and a fluidized nursery system can help reduce this cost and reduce seed production time. The present study evaluated the survival and growth of two oyster species (Crassostrea gasar and Crassostrea gigas) in a fluidized bed bottle nursery system. With C. gasar, two experiments were performed; one tested three stocking densities and the other three bialgae diets. With C. gigas, one experiment with a bialgae and monoalgae in an initial bottle occupation of 8.8% produced more seeds per bottle, but an initial bottle occupation of 2.2% produced bigger seeds. Also, the experiment with C. gasar and with C. gigas tested diets did not affect seed survival, but the diets with bialgae I. galbana and N. oculate promoted more seed growth. The fluidized bed bottle nursery system developed for this study was adequate for the seeds of the oysters C. gasar and C. gigas in the nursery phase. [ABSTRACT FROM AUTHOR]

Artificial enhancement and release activity is an important method in the restoration of fishery resources. In order to understand the possible genetic effect of hatchery-released populations on wild populations during the artificial enhancement and release activities of Sebastiscus marmoratus in Zhoushan waters, we utilized mitochondrial DNA control region sequences to examine the genetic diversity in four S. marmoratus populations, including one farmed population, one released population and two wild populations. A total of 68 haplotypes from 123 individuals were detected, including 3 shared haplotypes. Haplotype diversity ranged from 0.944 to 0.980, with a mean of 0.966. The nucleotide diversity ranged from 0.020 to 0.025, with a mean of 0.022. Analysis of Molecular Variance (AMOVA) indicated that the primary genetic variation occurs within populations and the index of genetic differentiation between populations (FST) among the four populations showed no differentiation. The results indicate that the current artificial enhancement and release has not impacted the S. marmoratus population in Zhoushan waters. Continued long-term monitoring is essential to protect the high-quality germplasm resources of S. marmoratus. [ABSTRACT FROM AUTHOR]

Summary: Millions of native fish are entrained into irrigation pumps in Australian rivers every year. It is often assumed these fish are wild, but stocked fish may also be affected. During fish entrainment surveys at two pump intakes on the Macquarie River, New South Wales, a noticeable increase of entrained juvenile Murray Cod (Maccullochella peelii) was observed. DNA parentage analysis confirmed that a large proportion of these fish were linked to nearby fish restocking events. At both pump intakes, genetic analysis confirmed that at least 70% and 17% of the individuals sampled were stocked fish. This equated to up to 3% of the fish that were stocked – most of which were entrained less than 24 h after their release. Given the large number of unscreened irrigation pumps in this reach of river, and more broadly throughout the Murray–Darling Basin, fish losses at pump intakes have the potential to remove large numbers of stocked fish from the river where they are released to support native fish recovery and boost recreational fishing opportunities. The use of fish‐protection screens at pump intakes may be a suitable solution to reduce the number of fish entrained and thus increase the survival of recently stocked fish in the rivers. [ABSTRACT FROM AUTHOR]

Accurately identifying the fish feeding intensity is crucial for timely understanding the feeding demand, dynamically adjusting the feeding strategy, and reducing costs. For the variability and uncontrollability of the pond aquaculture environment, the densities of feeding fish schools aggregating to the feeding point exhibit significant variations. Consequently, different densities of fish schools present inconsistent characteristics in the image, even under the same feeding intensity, making the precise identification of feeding intensity difficult. To tackle this issue, a method for identifying the feeding intensity of pond fish schools based on dual-label and MobileViT-SENet (DL-MobileViT-SENet) was proposed. The fish school images were marked with labels indicating density and feeding intensity to establish the dual-label dataset. Subsequently, a proposed MobileViT-SENet network is trained using the dataset to obtain the dual-label pre-training weight incorporating both fish density and feeding intensity features. Two models are trained to identify density and feeding intensity based on the obtained weight. Finally, a dynamic feeding strategy for fish that integrates biomass, density, and feeding intensity is presented. The proposed method combines the density and feeding intensity labels to enhance the accuracy of identifying the feeding intensity of pond fish schools across various densities, and lays the groundwork for designing a dynamic feeding strategy. It was tested on authentic pond fish school images and yielded an accuracy of 97.95%. This value is superior to these comparison methods, demonstrating that this method can accurately identify the feeding intensity of pond fish and provide support for formulating a dynamic feeding strategy. • A method for identifying fish feeding intensity at different densities is proposed. • To improve feature representation in pond culture, a MobileViT-SENet is introduced. • A dual-label pre-training method is proposed to shorten the model training. • A dynamic feeding strategy for pond fish is provided. [ABSTRACT FROM AUTHOR]

The effects of heat stress (HS) caused by high temperatures continue to be a global concern in poultry production. Poultry birds are homoeothermic, however, modern‐day chickens are highly susceptible to HS due to their inefficiency in dissipating heat from their body due to the lack of sweat glands. During HS, the heat load is higher than the chickens' ability to regulate it. This can disturb normal physiological functioning, affect metabolism and cause behavioural changes, respiratory alkalosis and immune dysregulation in birds. These adverse effects cause gut dysbiosis and, therefore, reduce nutrient absorption and energy metabolism. This consequently reduces production performances and causes economic losses. Several strategies have been explored to combat the effects of HS. These include environmentally controlled houses, provision of clean cold water, low stocking density, supplementation of appropriate feed additives, dual and restricted feeding regimes, early heat conditioning and genetic selection of poultry lines to produce heat‐resistant birds. Despite all these efforts, HS still remains a challenge in the poultry sector. Therefore, there is a need to explore effective strategies to address this long‐lasting problem. The most recent strategy to ameliorate HS in poultry is early perinatal programming using the in ovo technology. Such an approach seems particularly justified in broilers because chick embryo development (21 days) equals half of the chickens' posthatch lifespan (42 days). As such, this strategy is expected to be more efficient and cost‐effective to mitigate the effects of HS on poultry and improve the performance and health of birds. Therefore, this review discusses the impact of HS on poultry, the advantages and limitations of the different strategies. Finally recommend a promising strategy that could be efficient in ameliorating the adverse effects of HS in poultry. [ABSTRACT FROM AUTHOR]

This study explored the combined influence of tank color, stocking density, and gender on Tilapia zillii's performance and well‐being. In this 120‐day trial, 320 T. zillii, each initially weighing 10.0 ± 0.1 g/fish, were distributed among 24 tanks. The experiment included eight distinct treatment combinations, varying tank color (blue and green), stocking density (10 and 30 fish/m3) and sex (monosexual and mixed). The results showed that blue tanks improved specific growth rate and condition factor, while green tanks were better for feed utilization. Density at 30 fish/m3 showed the highest mean values of final body weight and total length, weight gain (WG), and gain length. Mono‐sex outperformed mixed‐sex ones in WG and daily growth. Interactions between color, density and sex were significant, affecting growth and feed utilization. Green tanks were best for protein profiles, while blue tanks excelled in glucose. A density of 10 fish/m3 yielded the highest protein profiles, and mono‐sex fish had higher protein profiles. For lipid profiles, green tanks were superior, and density affected lipid profiles. Mixed‐sex populations were best for certain lipid profile parameters. Interactions between these factors also played a significant role, making the biochemical profiles of T. zillii a complex interplay of various factors. The results explored that tank color, fish density and sex influence the activity of nonspecific immune enzymes in the liver of T. zillii. Blue tanks and lower fish density led to higher nonspecific immune enzymes, while mono‐sex fish exhibited more significant nonspecific immune enzymes. Complex interactions between these factors also influenced nonspecific immune enzyme activities. Blue tanks increased malondialdehyde (MDA) levels, while green tanks raised glutathione S‐transferases (GST) and catalase (CAT) levels. Lower fish density led to higher MDA, while higher density increased GST and CAT. Mono‐sex fish had more MDA and GST, while mixed‐sex fish showed greater CAT levels. Complex interactions among these factors affected the antioxidant levels in T. zillii. In summary, our study suggests that rearing T. zillii in green tanks at higher densities (30 fish/m3) and in mono‐sex conditions yields the best results in terms of growth and overall performance. [ABSTRACT FROM AUTHOR]

Climate change has myriad impacts on ecosystems, but the mechanisms by which it affects individual species can be difficult to pinpoint. One strategy to discover such mechanisms is to identify a specific ecological factor related to survival or reproduction and determine how that factor is affected by climate. Here we used Landsat imagery to calculate water clarity for 127 lakes in northern Wisconsin from 1995 to 2021 and thus investigate the effect of clarity on the body condition of an aquatic visual predator, the common loon (Gavia immer). In addition, we examined rainfall and temperature as potential predictors of water clarity. Body mass tracked July water clarity strongly in loon chicks, which grow chiefly in that month, but weakly in adult males and females. Long‐term mean water clarity was negatively related to chick mass but positively related to adult male mass, suggesting that loons foraging in generally clear lakes enjoy good foraging conditions in the long run but might be sensitive to perturbations in clarity during chick‐rearing. Finally, chick mass was positively related to the density of docks, perhaps because angling removes large fishes and thus boosts the abundance of the small fishes on which chicks depend. Water clarity itself declined strongly from 1995 to 2021, was negatively related to July rainfall, and was positively related to July air temperature. Our findings identified both long‐term and short‐term water clarity as strong predictors of loon foraging efficiency, and suggest that climate change, through water clarity, impacts freshwater ecosystems profoundly. Moreover, our results identified the recent decrease in water clarity as a likely cause of population decline in common loons. [ABSTRACT FROM AUTHOR]

Water diversions worldwide may entrain or impinge fish and have population‐level impacts, but barriers like fish screens can reduce such threats. Traditional barriers are ineffective in the San Juan River, USA, due to high sediment and debris loads, so the Hogback Diversion Canal, NM, employs a novel weir wall design to reduce entrainment of sub‐adult and adult fishes. We evaluated the effectiveness of the weir wall in reducing the entrainment of larval fish using a combination of experimental and overnight trials. Larval fish densities were compared between the irrigation canal that delivers water to irrigators and subsequently entrains fish and the bypass canal that conveys water and fish back to the river. The density of hatchery‐produced larval fish collected in the irrigation canal during the experimental trial (0.74 fish/m3) was 52% of their density in the bypass canal (1.43 fish/m3), suggesting entrainment reduction. The density of wild‐produced larvae during overnight trials indicated some minor, mostly nonsignificant, differences between catch rates in irrigation and bypass canals, ontogenetic phases, and sampling dates. Though entrainment rates of wild‐produced larvae were not significantly reduced, density differences among postflexion mesolarvae and metalarvae suggest possible entrainment reduction of more developed ontogenetic phases. More intensive research is necessary to better elucidate the efficacy of the novel weir wall for reducing the entrainment of larval fish. However, our larval fish results and the results from prior large‐bodied entrainment studies suggest the novel weir wall may reduce fish entrainment in water diversions and benefit fluvial ecosystems in which traditional screens are unfeasible. [ABSTRACT FROM AUTHOR]

The present study carried during the year 2022-23, worked on the impact of the introduction of genetically improved strains of rainbow trout on the economy of the fish farmers, in comparison to the normal strains. The economy of 40 farmers in groups of 20 Normal stock (NS) and Genetically Improved Stock (GIS) each was conducted and interviewed using a pre-tested questionnaire. The investigation showed that fixed capital investment on sample farm was Rs.1.25 lakh per raceway in both the set ups. The major share of investment was for the construction of raceway, which accounted for 68.53% of total investment on sample farms. The share of total variable cost was 58.37% in NS and 48.50 in GIS per cent and fixed cost was 41.62 in NS and 51.49 in GIS group. Feed was the major cost component accounting for about 46.43 per cent of the total cost in NS, while as it was reduced to 37.15% in GIS, thereby encouraging as a key factor in deciding profitability of trout farming. Resource use efficiency showed that feed was overutilized while labor was under-utilized in NS, while as it was optimally utilized in GIS group. The returns to scale in trout production of 1.25 indicates increasing returns to scale in trout production. High price of feed and seed are found to be the major constraints in trout culture. The B-C ratio worked out to be 1.37 in NS group and 1.87 in GIS group, indicating the economic feasibility of trout farming in the Kashmir valley, and better economic profile of farmers farming GIS strain. [ABSTRACT FROM AUTHOR]

With the global population growth and increasing demand for high-quality protein, aquaculture has experienced rapid development. Fish culture management and feed supply are crucial components of aquaculture. Traditional baiting management relies on experiential judgment and regular observation, which often leads to inefficient baiting practices and wastage. To address these issues, intelligent bait casting decisions have emerged. Leveraging advanced artificial intelligence algorithms, intelligent bait casting decisions can overcome most drawbacks of traditional bait management and enhance breeding efficiency. However, most of the current intelligent baiting decisions are focused on using methods such as image processing and target detection to identify different feeding actions and patterns. These methods do not discuss based on video streams and do not consider the changes in fish behavior during the baiting process. Therefore, we proposed a real-time analysis method based on the density distribution of fish feeding behavior (FishFeed). Firstly, this method upgrades the input mechanism, not only handling static images but also capable of real-time video stream analysis. Secondly, by evaluating the fish school density distribution through a new intelligent baiting strategy, this method can monitor the feeding behavior of fish school during the baiting process in real time. Finally, we constructed a dataset for fish school density analysis (DlouFishDensity) that includes a wealth of video and image frames, providing a valuable resource for research. Experimental results indicate that our algorithm outperforms MCNN, improving MAE by 1.63 and 1.35, MSE by 1.92 and 1.58, and reducing prediction time by 2.56 seconds on the same dataset. By implementing real-time analysis of fish feeding behavior density distribution, our method offers a more efficient and effective approach to baiting management in aquaculture, contributing to improved breeding efficiency and resource utilization. [ABSTRACT FROM AUTHOR]

Tenualosa ilisha popularly known as 'Hilsa' is one of the most commercially important euryhaline food fish species in South Asian countries. Co-infection of Fusarium incarnatum FHHS2 and Acinetobacter bohemicus FHHK1 was reported for the first time in captive-reared pre-adult T. ilisha (average length 22.30 ± 0.92 cm and weight 93.48 ± 28.06 g) that had manifested skin lesions in freshwater pond during November–December 2022. The infected fish showed lethargy, abnormal swimming behaviour, blackening of gills, red streaks on the fins, erosions of the skin, and sloughing of the scales resulting in 40% mortality of the stock. Microscopic observation revealed the presence of aerial slightly curved conidia, septate macroconidia, and randomly spread microconidia. The fungal species was confirmed as F. incarnatum FHHS2 (NCBI GenBank accession number OR030402) by ITS sequencing. It clustered with known pathogenic F. incarnatum (NCBI Accession no. AY633745) counterpart associated with black gill disease of Penaeus monodon Fabricius (99.46% homology) in phylogenetic tree. We have also isolated, identified, and characterised A. bohemicus FHHK1 from the infected fish which clustered with A. bohemicus reported in the lakes of Indian subcontinent (100.00% homology). No parasite was found in different organs of the moribund hilsa shad. Significant histopathological alterations were observed in the skin, gill, and kidney of infected hilsa. Our study records the first report of F. incarnatum FHHS2 and A. bohemicus FHHK1borne infection in hilsa during its domestication in freshwater pond. [ABSTRACT FROM AUTHOR]

Natural food available in ponds can complement formulated feed in fed aquaculture. This study elucidated the natural food intake and its contribution to tambaqui (Colossoma macropomum) growth in fertilized and unfertilized ponds, using stable isotope and stomach contents analyses. Additionally, it described the impact of fertilization management on natural food availability, fish performance, and production costs. Tambaqui juveniles (93.8 ± 15.0 g) were stocked (0.55 fish/m2) in fertilized (Fert) and unfertilized (NoFert) ponds (600 m2) for a culture period of 10 months in quadruplicate. A lower food conversion ratio was observed in Fert ponds. The main natural food items ingested by tambaqui were insects, vegetables, and cladocerans. Plankton contributed 39.4% and 10.7% of muscle formation in Fert and NoFert ponds, respectively. Pond fertilization (2.45 g of nitrogen and 0.80 g of phosphorus per square meter every two weeks) did not significantly affect fish growth, survival, or productivity but had a slightly influence on water quality parameters. However, fertilization increased the zooplankton density (through phytoplankton) in the water, thereby increasing autochthonous food availability for tambaqui consumption. This species demonstrates the ability to alternate between natural food sources and commercial feed without compromising its development. Consequently, tambaqui exhibits suitability for farming within restorative and integrated aquaculture systems as well as intensive systems reliant on commercial feed. [ABSTRACT FROM AUTHOR]

Fish marking is an essential tool for fisheries management, especially for evaluating the stocking of endangered fish species to support conservation and sustainable use of fish stocks. Batch marking of young European eels Anguilla anguilla (L.) prior to stocking is recommended as the benefits of stocking for the spawning stock can be evaluated by recapturing marked fish over time, therefore mass marking of young eels with substances such as alizarin red S (ARS) is becoming increasingly important. To improve the marking method and reduce marking costs when immersing glass eels in an ARS solution, eight laboratory experiments under varying conditions (e.g., temperature, ARS concentration, immersion time, osmotic induction, fish density) and with ARS from different suppliers were carried out. The results show that optimal marking of glass eels can be carried out in the field or during transport by putting approximately 50 g of glass eels per liter in 150 mg L−1 ARS solution for 3 h at 10–15°C. Lower concentrations did not result in reliable marking. Water temperatures of 5°C and below can have a stunning effect on the eels and increase mortality significantly, regardless of the concentration of ARS. Glass eel densities below 50 g L−1 in the marking bath increase marking costs unnecessarily, while a higher density of 100 g L−1 resulted in significantly higher mortality and lower marking success. A somewhat more difficult but less expensive alternative is to bathe the fish in a saline solution of 1% (10 PSU) of 80 mg L−1 ARS for 3 h at 10°C. Costs can also be significantly reduced by choice of supplier for ARS, but care should be taken as the quality of the powder appears to vary (mean percentage of sufficiently marked eels ranged from 59% to 91% among suppliers in the present study) and can lead to marking failure. The optimal marking conditions can help ensure that stocked glass eels can be reliably identified in future studies to assess stocking benefits while reducing costs. [ABSTRACT FROM AUTHOR]

Questions: Agricultural expansion is one of the dominant drivers of forest and biodiversity loss, and shifting cultivation is the most widely used form of agriculture in many tropical forest regions. Where forests have been cleared, they have the potential to recover once the land is abandoned. However, legacies of land use are often overlooked in successional studies, and a deeper understanding of this legacy effect is needed to define efficient restoration practices using natural or assisted regeneration. Here, we analysed how land‐use history affects soil properties and early succession on abandoned agricultural fields in two contrasting Mexican socio‐ecological systems. Location: Mexico, Oaxaca and Chiapas. Methods: We sampled soil and monitored vegetation for 2 years after agricultural abandonment, and interviewed landowners about their land‐use practices. Results: Land‐use practices were clearly influenced by landowners' social context (residence time, rural or urban origin), and topography and soil type also constrained or facilitated land‐use practices. Soil characteristics were strongly affected by three land‐use practices: mechanical tillage decreased soil N and K; frequent herbicide and pesticide use increased N and K; and for pasture systems, stocking density increased soil bulk density and decreased pH and N. High‐intensity land management practices, specifically use of machinery, had the highest impact on early forest succession. When machinery was not used, the frequency of land‐use practices, particularly weeding frequency, is the main factor influencing tree cover and sapling diversity. Conclusions: To facilitate post‐agricultural forest recovery, we recommend restoration efforts using natural regeneration in areas with low previous land‐use intensity and frequency. [ABSTRACT FROM AUTHOR]

Whiteleg shrimp (Litopenaeus vannamei) is a widely cultivated commodity in Indonesia. The high demand of white leg shrimp requires increased production. High stocking density in intensive cultivation and excessive amounts of feed are obstacles in white leg shrimp productiom. It will cause the shrimp to become stressed and susceptible to pathogen infection, one of them is ectoparasite. This research was conducted from August to September 2023 with the aim of determining the intensity and infestation degree of ectoparasite on white leg shrimp that cultivated in intensive ponds. The samples of white leg shrimp in this study were 50 individuals by purposive random sampling method. Observations were carried out by native method in the Cultivation and Anatomy Laboratory, Faculty of Fisheries and Marine, Airlangga University. The results showed that white leg shrimp cultivated in intensive ponds were infested by Zoothamnium sp. with intensity 184 individuals/tail, Vorticella sp. with intensity 268 individuals/tail and Epistylis sp. with intensity 235 individuals/tail. Each ectoparasite has a very severe infestation degree, but the most severe infestation was carried out by Vorticella sp. [ABSTRACT FROM AUTHOR]

Large-bodied animals, such as the Mekong giant catfish (Pangasianodon gigas), may modify prey communities and affect their potential competitors for food resources by consuming large quantities of prey. The Mekong giant catfish is a key representative of freshwater megafauna and is stocked in reservoirs in Thailand for species conservation and fishery stock enhancement. However, their biological interactions with other sympatric animals remain unclear. Here, we aimed to investigate the trophic niche of the Mekong giant catfish in a Thai reservoir by comparing stable carbon and nitrogen isotope ratios (δ13C and δ15N, respectively) and fatty acid (FA) composition with those of five other sympatric fish species. The δ13C value of the Mekong giant catfish was –24.4 ± 1.0‰ (mean ± SD), the second highest among the sympatric fish species, suggesting relatively weak reliance on phytoplankton-based food chains. The δ15N value of the Mekong giant catfish was 10.7 ± 0.4‰, intermediate between those of herbivorous and carnivorous fishes, indicating that it is not a primary consumer. The FA composition of the Mekong giant catfish significantly differed from those of the other fish species and was characterized by a large proportion of long-chain FA, including 22:6n-3, 20:5n-3, and 20:1n-9. The δ13C, δ15N, and FA signatures suggest that the Mekong giant catfish occupy distinct trophic niches in food webs. Our results highlight that it is necessary to monitor the ecological impacts of released Mekong giant catfish on lower-level consumers through their foraging in receiving reservoirs. [ABSTRACT FROM AUTHOR]

Yellow catfish Tachysurus fulvidraco is an important commercial fish species in South Korea. However, due to their current declines in its distribution area and population size, it is being released from hatchery populations into wild populations. Hatchery populations also produced from wild broodstocks are used for its captive breeding. We reported 15 new microsatellite DNA markers of T. fulvidraco to identify the genetic diversity and structure of its hatchery and wild populations, providing baseline data for useful resource development strategies. The observed heterozygosity of the hatchery populations ranged from 0.816 to 0.873, and that of the wild populations ranged from 0.771 to 0.840. Their inbreeding coefficient ranged from −0.078 to 0.024. All populations experienced a bottleneck (p < 0.05), with effective population sizes ranging from 21 to infinity. Their gene structure was divided into two groups with STRUCTURE results of K = 2. It was confirmed that each hatchery population originated from a different wild population. This study provides genetic information necessary for the future development and conservation of fishery resources for T. fulvidraco. [ABSTRACT FROM AUTHOR]

Integrated rice-fish farming has emerged as a novel agricultural production pattern to address global food security challenges. Aiming to determine the optimal, scientifically sound, and sustainable stocking density of red claw crayfish (Cherax quadricarinatus) in an integrated rice-crayfish farming system, we employed Illumina high-throughput 16S rRNA gene sequencing to evaluate the impact of different stocking densities of red claw crayfish on the composition, diversity, function, and co-occurrence network patterns of soil bacterial communities. The high stocking density of red claw crayfish reduced the diversity and evenness of the soil bacterial community during the mid-culture stage. Proteobacteria, Actinobacteria, and Chloroflexi emerged as the most prevalent phyla throughout the experimental period. Low stocking densities initially boosted the relative abundance of Actinobacteria in the paddy soil, while high densities did so during the middle and final stages. There were 90 distinct functional groups identified across all the paddy soil samples, with chemoheterotrophy and aerobic chemoheterotrophy being the most abundant. Low stocking densities initially favored these functional groups, whereas high densities enhanced their relative abundances in the later stages of cultivation. Medium stocking density of red claw crayfish led to a more complex bacterial community during the mid- and final culture stages. The experimental period showed significant correlations with soil bacterial communities, with total nitrogen (TN) and total phosphorus (TP) concentrations emerging as primary factors contributing to the alterations in soil bacterial communities. In summary, our findings demonstrated that integrated rice-crayfish farming significantly impacted the soil microbiomes and environmental factors at varying stocking densities. Our study contributed to theoretical insights into the profound impact of integrated rice-crayfish farming with various stocking densities on bacterial communities in paddy soils. [ABSTRACT FROM AUTHOR]

Objective: Density‐related information for landlocked fall Chinook Salmon Oncorhynchus tshawytscha shortly after first feeding is poorly understood. This study was undertaken to determine the effects of a range of rearing densities (low, intermediate, and high) on rearing performance and survival of newly feed‐trained juvenile landlocked fall Chinook Salmon. Methods: The fish were reared for 66 days in 1.8‐m (diameter) tanks with approximate volume of 2036 L at one of three loadings of approximately 2500, 5000, or 10,000 fish/tank. Result: The initial and final densities for each of the three loadings were 0.73 and 8.93, 1.45 and 16.41, and 2.90 and 26.86 kg/m3, respectively. At the end of the study, the specific growth rates were significantly lower, total lengths were significantly shorter, and feed conversion ratios were significantly greater in the fish from the highest‐density treatment relative to the fish in the other treatments. Percentage of weight gain, final weights, and condition factor were significantly reduced in fish from the highest‐density treatment relative those at the lowest density. There were no significant differences in any growth metrics between fish that were reared at the lowest and intermediate densities. The intermediate density (5000 fish/tank) produced intermediate results that did not significantly differ from either the highest or lowest densities. Mortality was not significantly different among the density treatments. Conclusion: An initial loading of 5000 fish in 1.8‐m (diameter) circular tanks, corresponding to initial and final densities of 1.45 and 16.41 kg/m3, respectively, is recommended to minimize the detrimental effects of density on newly feeding Chinook Salmon while maximizing their production in often limited hatchery space. Impact statementThe use of intermediate tank loadings of fall Chinook Salmon in 1.8‐m (diameter) circular tanks (corresponding to initial and final densities of 1.45 and 16.41 kg/m3, respectively) minimized the detrimental effects of rearing density on newly feeding salmon while maximizing Chinook Salmon production in limited hatchery space. [ABSTRACT FROM AUTHOR]

This study describes the effects on the skeletal phenotype of two pivotal factors, density and water volume, don the hatchery (larval) phase of gilthead seabream (Sparus aurata) larvae previoulsy described for two model species (Danio rerio and Oryzias latipes) and sub‐adult (pre‐ongrowing) gilthead seabream (Sparus aurata). The experimental trial was conducted using single conditions in a pilot study, starting with a total of 615,385 eggs from the same batch. Three densities (LD low density: 25 larvae/L; MD medium density: 125 larvae/L; and HD high density: 250 larvae/L) and two water volumes (500 and 1000 L) were tested from spawning up to 60 days post‐hatching (dph) (average standard length: 1.79 cm; average dry weight: 27.11 mg). On the final samples, morphometric, anatomical, and histological data were collected for data pertinent to meristic counts and skeletal anomalies. The results (analyzed by means of multivariate analyses) indicated that the LD‐reared larvae were significantly longer and heavier than HD‐reared fish. Furthermore, LD‐reared gilthead seabream exhibited a significant reduction in the frequency of individuals with anomalies of jaws, vertebral body shape, and vertebral arches than the MD and HD conditions, which is in agreement with previous experiments carried out on model species and gilthead seabream sub‐adults. [ABSTRACT FROM AUTHOR]