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Biomanipulation by piscivore stocking has been widely used for restoration of temperate shallow lakes, but long-term results have been mixed. In warm (i.e., subtropical/tropical) lakes where omni-benthivorous fish prevail, the effects of piscivore stocking on small fish, plankton communities, and water quality have not been well elucidated yet. Here, we conducted a mesocosm experiment in the subtropics to examine the top-down and bottom-up effects of stocking of a native piscivorous fish, mandarin fish (Siniperca scherzeri). The experiment consisted of two treatments (piscivore present/absent) in triplicate, lasting for 90 days and including two periods. Crucian carp (Carassius carassius) were stocked twice to simulate the recruitment of small fishes. Our results showed that stocking of mandarin fish significantly reduced the abundance of crucian carp but did not increase zooplankton biomass nor reduced the phytoplankton biomass, the concentrations of nutrients or suspended solids, suggesting that both top-down and bottom-up control of phytoplankton were unaffected by stocking mandarin fish. Moreover, the presence of mandarin fish did not help maintain a clear water state in the period of crucian carp recruitment. Our results indicate that piscivore stocking may not help control phytoplankton biomass in subtropical shallow mesocosms, at least on the short term. [ABSTRACT FROM AUTHOR]

Present study aimed at improving the immune and antioxidant response of Pacific white shrimp (Litopenaeus vannamei) cultured at high stocking density fed with 0.2% supplementation of lauric acid (LA) and N-acetyl-L-cysteine (NAC). Shrimp (initial average weight = 0.65 g; n = 270) were grown at low stocking density (LSD) (n = 10/0.80 ft3 per replicate) and high stocking density (HSD) (n = 20/0.80 ft3 per replicate). They were randomly distributed into five groups (T1: negative control at LSD, T2: positive control at HSD, T3: at HSD and fed with LA supplement diet, T4: at HSD and fed with NAC supplemented diet, T5: at HSD and fed with combination of LA and NAC). All these five treatments were studied in triplicates and study continued for eight weeks. Better growth and higher levels of glucose, total protein, total hemocyte count and phagocytic index were observed in shrimp fed with NAC and LA supplemented diets. Observed survival rate and feed conversion ratio in all treatments was 75–89% and < 0.82, respectively. All parameters indicating stress were observed to be higher in T1 as compared to T2. Improved expression of superoxide dismutase and glutathione peroxidase and lower levels of malondialdehyde genes in T3, T4 and T5 showed that supplementation with these nutraceuticals can improve antioxidant response at high stocking density. A parallel increase was observed in the profiles of prophenoloxidase and lysozyme, underscoring the immune-boosting effects of both NAC and LA. This finding was further supported by higher expression of innate immune signaling pathway-related gene, toll like receptor-2 in T3, T4 and T5. In conclusion, NAC and LA, can possibly improve the resistance of white pacific shrimp against oxidative stress and pathogens when cultured in intensive production system. [ABSTRACT FROM AUTHOR]

The objective was to identify the best stocking density in the initial grow-out phase of tambaqui (Colossoma macropomum) using biofloc technology (BFT) and evaluate the effects of the densities on water quality, zootechnical performance and the metabolic profile of fish and production costs. Juveniles (56.5 ± 1.69 g) were reared in the densities: 15 (BFT15), 30 (BFT30) and 45 (BFT45) fish.m−3, in triplicate, for 80 days. The use of BFT inoculum at the beginning contributed to the maintenance of adequate ammonia and nitrite concentrations at all densities, though with a higher nitrite concentration in BFT45. Electrical conductivity (EC), nitrite, total suspended solids (TSS), pH, alkalinity and hardness were different (p < 0.05) between BFT15 and BFT45. EC and TSS increased according to the increase in density, and were higher in BFT45. The highest final weight and specific growth rate were observed in BFT15, while the apparent feed conversion was lower for BFT15 and BFT30 compared to BFT45 (p < 0.05). Biomass and productivity were higher (p < 0.05) in BFT45. The values of hematocrit, number of erythrocytes and the hemoglobin concentration were higher in BFT45 (p < 0.05). Regarding production costs, the highest average feed expenditure occurred in BFT45; however, expenditure with electricity was lower at this density. The increase in biomass in BFT45 generated the reduction of the partial average cost (ACp). It can therefore be concluded that the best stocking density for initial grow out of tambaqui is 45 fish.m−3, since it presents better productivity and biomass, lower ACp and average expenditure on electricity when using BFT. [ABSTRACT FROM AUTHOR]

The shrimp nursery is an important tool to improve the shrimp zootechnical and health performances. However, diseases and high mortality rates are the main limitations of the nursery system. Therefore, this work aimed to evaluate the influence of stocking density in the synbiotic nursery system, through growth, microbial composition, and water quality. The experiment lasted 30 days and used Penaeus vannamei postlarvae (PL10, 0.003 ± 0.001 g), fed with commercial feed (40–45% crude protein) and treatments were completely randomized with 2000, 4000, and 6000 PL‧m−3, with three replicates. Before and after stocking the postlarvae, in the experimental units (10 m3), were added a mixture of rice bran, brown sugar, commercial probiotic, and sterilized water (Synbiotic). The bottom water of tanks was drained twice a week, totaling a total 5% water exchange during the total experiment and alkalinity was corrected with calcium hydroxide (Ca(OH)2) when the alkalinity values were < 100 mg CaCO3‧L−1. Weekly, the total ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and total alkalinity were monitored and microbiological analyses were conducted at the beginning and end. After the trial (30 days), the influence of the different stocking densities on the final weight, survival, feed conversion ratio, weekly growth rate, and productivity, with higher values for 2000 PL‧m−3. Also observed. Vibrio spp., Lactobacillus spp., total heterotrophic bacteria, and yeast count values increased by the end of the period in all shrimp stocking densities, however, with only significant differences in yeast count. In relation to ammonia, nitrite, and nitrate, no significant differences were observed in the influence of the different stocking densities. Based on the data obtained, we recommend using a density of 2000 PL‧m−3 in the nursery phase, with better zootechnical performance, water quality, and microbial composition. [ABSTRACT FROM AUTHOR]

Aquaponics is the integration between aquaculture and hydroponics, where bacteria mediate the interaction between fish and plants, facilitating a mutually beneficial system. Although there have been numerous studies on aquaponics, there have been few studies focused on optimizing management parameters in small-scale systems for family farming. A key aspect is to find the appropriate culture density to maximize the production of both fish and plants. In aquaculture, introduced species have predominated due to their ease of management, great adaptability, and high growth rates; however, it is important to consider alternatives such as Dormitator latifrons. To determine the effect of density on the yield of D. latifrons and chard Beta vulgaris in an aquaponic culture, three culture densities of 10, 30, and 50 fish m−3 were evaluated in triplicate with a fixed plant density of 20 plants m−2. Nine experimental units (EU) were implemented consisting of 300 L Rotoplas® troughs, a settler (80 L), a biofilter (80 L), and a submersible water pump connected to a nutrient film technique (NFT) system that represented the hydroponic component. The results obtained suggest that an intermediate stocking density (30 fish m−3) could provide a favorable balance between fish and plant performance and fish health. These findings contribute to the knowledge on the culture of this species in aquaponics. [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]

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]

The interconnectedness of adjacent freshwater and terrestrial ecosystems results in 'tangled‐webs', where the cross‐boundary exchange of materials results in energy flows that provide critical resources for ecosystem productivity. However, these energy flows can be disrupted by anthropogenic activities, resulting in modified ecosystem functioning.A ubiquitous anthropogenic activity in fresh waters is recreational angling. Five major angling activities can disrupt the structure of the 'tangled‐web' to produce an 'angled‐web' (a tangled food web that is modified by angling activities). (1) Fish stocking increases the number and species available to exploit, but the increased fish abundances can have strong top‐down effects and disrupt reciprocal prey subsidies. Following capture, fish are either (2) harvested or (3) released alive ('catch‐and‐release0'); both can both drive eco‐evolutionary changes that can modify food‐web structure. Where fish are exploited using baited hooks, (4) the release of 'ground‐bait' is used as a fish attractant; its composition of novel protein and carbohydrate sources form novel trophic links in the food web and can accelerate eutrophication. Some angling styles also require (5) riparian and in‐stream vegetation to be cleared to minimise gear fouling, potentially modifying fish spawning and nursery areas.We suggest that each of these angling impacts (and their interactions) can contribute to transforming the 'tangled web' into an 'angled‐web', with the strength and direction of the transformation dependent on angling pressure, prevailing fishery practices, regulations and management, and the extent of the interaction effects of the activities. These interactions and their impacts will vary globally given angling methods, practices and regulations differ across the world.We argue that, in this era of substantial environmental change driven by climate change, habitat loss and nutrient enrichment of fresh waters, the extent to which angling impacts food webs should not be overlooked and underappreciated. We emphasise that when freshwater angling activities are poorly managed and/or unregulated, they can strongly modify the interconnectedness between terrestrial and freshwater food webs. [ABSTRACT FROM AUTHOR]

Fish stocking has been utilized for over a century to offset extirpations or declines in abundance of many native species. These historical declines and hatchery contributions have led to uncertainty surrounding whether many contemporary populations are native, introgressed with hatchery sources, or entirely of hatchery origin. Such uncertainty is problematic for the conservation of native biodiversity as it hampers management agencies' ability to prioritize the conservation of indigenous locally adapted populations. Fortunately, genetic and genomic tools have allowed researchers to investigate these questions, often through the use of clustering or assignment approaches that are predicated on identifiable and consistent divergence between native populations and hatchery sources. Here, we apply these methods to restriction‐site associated DNA (RAD) data from 643 brook trout (Salvelinus fontinalis) originating from 13 wild populations and an exogenous hatchery strain to investigate the extent of historical extirpations, hatchery contributions, and processes affecting population structure in a small area of the previously unglaciated Driftless Area of Wisconsin, USA. The results from these analyses suggest that wild populations in this region are genetically distinct even at small spatial scales, lack strong hydrologically associated population structure, rarely exchange gene flow, and have small effective population sizes. Furthermore, wild populations are substantially diverged from known hatchery strains and show minimal evidence of introgression in clustering analyses. However, we demonstrate through empirically informed simulations that distinct wild populations may potentially be hatchery‐founded and have since diverged through rapid genetic drift. Collectively, the apparent lack of hydrological population structure and potential for rapid drift in the Driftless Area suggest that many native populations may have been historically extirpated and refounded by stocking events. If this is the case, then commonly used genomic clustering methods and their associated model selection criteria may result in underestimation of hatchery introgression in the face of rapid drift. [ABSTRACT FROM AUTHOR]

The study aimed to assess the impact of stocking density on the growth performance, survival rate and production of seabass (Lates calcarifer) fingerlings in floating net cages conducted at the Maheshkhali Channel, Cox's Bazar, Bangladesh. A triplicate group of seabass, with an average initial weight of 86.82 ± 1.9 g, was randomly stocked in floating net cages at densities of 15, 12, 10 and 8 fish m−3, referred to as T15, T12, T10 and T8, respectively. The fish fingerlings were supplied with freshly chopped sardine (Sardinella fimbriata) at 10% of their body weight for 4 months and 5% for 2 months, administered twice daily. The water quality metrics were measured fortnightly. The initial and the final proximate composition of seabass was not significantly different (p > 0.05). Upon completion of the experiment on the 180th day, the growth performance and additional measures, including final body weight, weight gain (WG), percent weight gain (PWG), specific growth rate (SGR), feed conversion ratio (FCR), feed efficiency ratio (FER), survival rate and total production, were assessed. Comparisons of growth and yield demonstrated that fish stocking density significantly (p < 0.05) influenced growth and productivity. Fish cultivated at maximum density (T15) exhibited lower mean weights than those raised at lower densities. This study demonstrated that T10 had better results for all growth and other metrics examined, indicating the appropriateness of this density. Therefore, it may be inferred that seabass exhibits optimal growth at a stocking density of 10 fish m−3 along the coast of Cox's Bazar, Bangladesh. [ABSTRACT FROM AUTHOR]

In order to study the suitable stocking density of out-season E. sinensis marketing in lunar June （Eriocheir sinensis） under pond culture conditions, male juvenile E. sinensis（20. 43 ± 0. 11 g） were divided into three different stocking density groups: 1. 5 ind./m2（ low density group）, 2. 25 ind./m2（ medium density group） and 3 ind./m2 （high density group）. The growth performance, tissue indices, culture effect and economic profits of out-season E. sinensis marketing in lunar June were compared through a 140-day culture experiment. The results showed that: （1） Since April 15, the average body weight of the low density group was always the highest, the medium density group was the second, and the high density group was the lowest. There were significant differences among the three groups on June 15 and July 5. The total weight gain rate （WGR） of the low density group was slightly higher than that of the medium density group, and both of them were significantly higher than that of the high density group（P<0. 05）. The meat yield（MY） of low density group and medium density group was significantly higher than that of high density group（P<0. 05）. The total edible yield（TEY） of low density group was significantly higher than that of high density group（P<0. 05）. （2） The final average body weight and survival rate（SR） of the low density group were significantly higher than those of the medium and high density groups（P<0. 05）, while the yield of the high density group was significantly higher than that of the medium and low density groups（P<0. 05）. The feed conversion rate （FCR） and limb loss rate（LLR） of the high density group were significantly higher than those of the low density group（P<0. 05）, but there was no significant difference between the high density group and the medium density group（P>0. 05）. In terms of size distribution, the proportion of larger-sized male E. sinensis （≥110 g） of low density group was the highest and that of smaller-sized male crab（<100 g） was the lowest. （3） The total cost and total income of the high density group were the highest, the medium density group was the second, and the low density group was the lowest. The differences among them were significant（P< 0. 05）. The net profit of the high density group was significantly higher than that of the low density group（P< 0. 05）, and slightly higher than that of the medium density group. The return-on-investment（ROI） is just the opposite. The culture model of out-season E. sinensis marketing in lunar June has the characteristics of short culture cycle, simple production operation, low investment cost and high income. Considering comprehensively, the suitable stocking density of out-season E. sinensis marketing in lunar June is 3 ind./m2. [ABSTRACT FROM AUTHOR]

The densities of existing fish populations in streams may affect salmonid stocking programs. Non-native brown trout (Salmo trutta) now occur in rivers in Japan that are managed via stocking programs to restore recreational fisheries for native white-spotted charr (Salvelinus leucomaenis), but how they affect charr stocking programs needs to be better understood. We investigate how suppressing populations of brown trout affects the density and biomass of stocked charr population sizes and biomasses. We report no significant change in charr abundance or biomass after stocking into areas in which brown trout are abundant. However, following suppression of brown trout, charr significantly increased in numbers and biomass, and their settlement rates rose in excess of 10 times. We suggest that brown trout outcompete charr for habitat and food resources, and that stocking charr in streams in which brown trout populations exist is unlikely to be effective in the management and restoration of recreational fisheries, but that stocking them into streams in which brown trout have been suppressed is more likely to be effective. [ABSTRACT FROM AUTHOR]

In the last five years, the state of Haryana has implemented a few high stocking density holding modern fish farming technologies such as Biofloc and Recirculation Aquaculture System (RAS) to boost farmers' fish production. Besides this, RAS technology has the potential to filter water while reducing the danger of environmental contamination and disease outbreaks due to its unique characteristic of filtration systems. The primary goal of this face-to-face interview-based study was to determine the state of various variables, characteristics, RAS employees' skills, farmer engagement, and the role of the Pradhan Mantri Matsya Sampada Yojana (PMMSY) in the overall development of this technology in state of Haryana. The majority of RAS farms in Haryana (55%) employed unskilled employees, 25% employed mixed skilled and unskilled workers, and 20% employed just skilled workers. With the implementation of the Pradhan Mantri Matsya Sampada Yojana (PMMSY), the majority of farmers (90%) received government subsidies for the construction of their high-cost RAS projects, while 5% of farmers built their RAS systems under the Blue Revolution scheme and 5% used their own resources to build the farms without any government assistance. On the other side, majority of RAS farmers (45%) sell their production stock to local district markets, while 30% opted to sell their stock inside and beyond the state, compared to 25% who sold their output within their district and State Haryana. All RAS farmers have single units of RAS for fish farming but only 70% RAS farms have 8-6 production tanks on their RAS farms. Whereas 95% of farmers have a power backup (generator) for the appropriate operation of RAS filtration during emergency hours, 35% of RAS farms have four aerators/units for improved filtration and fish survival under high stocking density technology. [ABSTRACT FROM AUTHOR]

Research in seaweed cultivation technologies aims to increase production and reduce costs, leading to more efficient and sustainable processes. In this study, we analyzed the outdoor production of Ulva compressa cultured in summertime at different stocking densities of 0.6, 0.8 and 1.0 kg Fresh weight (FW) m−2 in a raceway photobioreactor with 30 m2 surface (3000 L), and its relation to photosynthetic activity. Under the experimental conditions of high temperature (>28–30 °C) and pH > 9 in culture water, higher seaweed density resulted in lower specific growth rate. The biomass production has been related to photosynthetic activity by using in vivo chlorophyll a fluorescence. Dynamic photoinhibition was observed at noon, which was less severe in cultures with higher algal densities. However, photosynthesis recovered in the afternoon. Seaweeds that were acclimatized for a week to the conditions of 1.0 kg FW m−2 stocking density showed an increase in biomass growth and absence of photoinhibition compared to non-acclimatized thalli. In conclusion, the cultivation of U. compressa in a mid-scale raceway photobiorreactor under conditions of high irradiance and temperature and low nutrient input, exhibited the best photosynthetic performance and hence the highest growth rates for the highest culture density assayed (1.0 kg FW m−2). [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 article discusses the impact of William Taylor on cross-border river sharing challenges and sustainable fisheries. It highlights collaborations between Michigan State University and various European universities to address environmental policy gaps. The text delves into specific case studies, such as the Rogun Dam in Tajikistan and the Grand Ethiopian Renaissance Dam, to illustrate the complexities of water resource management and the need for equitable solutions in politically divided regions like Central Eurasia. The article emphasizes the importance of interdisciplinary research and international cooperation in addressing environmental sustainability issues. [Extracted from the article]

Objective: The spiny sand lobster Panulirus homarus is one of the lobster species that has a high price in local and international markets and is economically valuable. The objective of this study was to determine the effect of stocking density on the survival and growth of spiny sand lobsters kept in cylindrical cages (1.00 m high × 1.15 m in diameter) at a depth of 7 m below the water surface, with an average ambient temperature of 29–32°C. Methods: The 3‐month study was performed in 2022 and had a completely randomized design. There were three treatment groups, each of which had three replications. Stocking densities were 10 lobsters/m2 (10 lobsters/cage) for treatment A, 15 lobsters/m2 (15 lobsters/cage) for treatment B, and 20 lobsters/m2 (20 lobsters/cage) for treatment C. The initial average body weight was 75 g/lobster. Result: The survival rates for treatment A (mean ± standard error = 91.50 ± 0.25%) and treatment B (93.30 ± 0.51%) were higher than the survival rate for treatment C (86.05 ± 0.45%), but the values were not significantly different. Daily weight gain and the specific daily growth rate for treatments A and C were significantly higher than those of treatment B. The feed conversion ratio was not significantly different among the groups. Total hemocyte count in the hemolymph between treatments A and B as well as initial (day‐0) values were not significantly different, but values for treatments A and B were significantly lower than that for treatment C. The hemolymph glucose value for treatment A was significantly lower than that of treatment C but was not different from that of treatment B. Conclusion: The grow‐out study of spiny sand lobsters at 7‐m depth indicated an optimal stocking density of 15 lobsters/m2. This was supported by several physiological response and production performance parameters, which generally had no significant difference with those of the lower stocking density. Impact StatementWe investigated three different stocking densities of spiny sand lobsters at 7‐m depth. We explored whether the standard stocking density of lobsters could be determined according to their size. This is very important for lobster farmers who wish to understand the appropriate stocking density to ensure a reliable production of lobsters with high survival and growth rates. The present findings contribute to more sustainable aquaculture practices. [ABSTRACT FROM AUTHOR]

Intensified production of stocker‐size tilapia can be accomplished using the biofloc technology production system. Stocker‐size tilapia (ca. 10–200 g/fish) are raised for subsequent stocking for grow‐out to market size. The relationship between stocking rate and the production of stocker‐size hybrid tilapia (Oreochromis aureus × O. niloticus) was evaluated in two studies in outdoor mixotrophic biofloc tanks. Hybrid tilapia were stocked in 18.6‐m2 (15.7‐m3) tanks at 50–150 fish/m2 (59–178 fish/m3) in 25 fish/m2 (30 fish/m3) increments in Study 1 and grown for 141–143 days. Stocking rates evaluated in 4.7‐m2 (3.6‐m3) tanks during Study 2 over 78–79 days ranged from 100 to 300 fish/m2 (132–396 fish/m3) in 25 fish/m2 (33 fish/m3) increments. Linear regression models best described growth to stocker size in both studies. Fish yield increased linearly with stocking rate and ranged from 20.1 to 38.3 kg/m3. Individual weight at harvest was inversely related to stocking rate and ranged from 389.8 to 163.4 g/fish and 155.2 to 81.4 g/fish in Studies 1 and 2, respectively. Partial budget analyses suggested positive net changes in profit with incremental increases in stocking rate for producing a 75‐g stocker. Water quality concentrations were impacted directly by daily feed ration and total feed fed, which increased linearly with stocking rate. In Study 2, whole‐body dry matter, protein, protein retention, and lipid were unaffected by stocking rate, whereas whole‐body ash increased with stocking rate. Whole‐body energy retention significantly decreased with stocking rate. The outdoor mixotrophic biofloc production system is well suited for intensive production of hybrid tilapia stockers. However, additional replicated research and economic analysis are needed to evaluate stocking rate and culture duration to produce specific‐sized stocker hybrid tilapia. [ABSTRACT FROM AUTHOR]

Fish stocking continues to be an important and often‐used tool in fisheries management. Mortality of fish may be high in the first few days after stocking due to predation and a lack of appropriate food and habitat. The objective of this study was to develop a conceptual model that may identify stocking locations that can help improve the survival of stocked fish. We identified three factors—predator risk, zooplankton (food) availability and measures of habitat that could be important to the survival of stocked Walleye (Sander vitreus) and White Bass (Morone chrysops) fingerlings in Lake McConaughy, Nebraska. The spatial distribution of these factors was used to create a predictive surface to identify those stocking locations hypothesised to lead to higher survival. Final stocking maps identified the best 12.8% and 13.9% of the predicted area of Lake McConaughy for stocking Walleye and White Bass, respectively. Both maps predicted that the best locations were along the south‐central shoreline of Lake McConaughy. The maps for both species were interestingly similar. These results are likely due to the similarities in predators consuming the stocked species and the zooplankton consumed by fingerlings of both species. Habitat availability may be less important, or other aspects of habitat may need to be considered. Identifying the best locations for stocking based on predation risk and the availability of food and habitat could increase the survival of stocked fishes and help managers reach population objectives. [ABSTRACT FROM AUTHOR]

Context: Successful fish stocking relies upon releasing cohorts directly into habitat containing suitable supporting resources. To facilitate this, an emerging trend has seen fish released onto artificial reefs. Aims: We compared the residency and movement patterns of juvenile sparids (yellowfin bream – Acanthopagrus australis), stocked on artificial reefs and natural habitat, to determine the suitability of incorporating artificial structures as release sites in future stocking programs. Methods: Forty hatchery-reared yellowfin bream were evenly divided and stocked on either artificial reef or natural habitat within an east-Australian estuary, and tracked using acoustic telemetry. Key results: Artificial reefs provided greater habitat complexity than the natural habitat and fish stocked onto these structures showed greater fidelity to their release site and were detected for longer periods of time than those stocked into less complex natural habitat. Conclusions: The high residency levels of fish around artificial reef sites indicate they contain resources to support stocked juvenile sparids. Implications: Stocked yellowfin bream can tolerate a range of salinity and temperatures, allowing flexibility in stocking programs. Future stocking of bream or other sparids should consider releasing fish onto artificial reefs where available. Additionally, the deployment of reefs could aid existing stocking programs. Successful fish stocking relies upon releasing cohorts directly into habitat containing suitable supporting resources. We compared residency and movement patterns of juvenile yellowfin bream stocked on artificial reefs and less complex natural habitat. Fish stocked on artificial reefs showed greater fidelity to their release site and were detected for longer periods. Future stocking of bream or other sparids should consider releasing fish onto artificial reefs, with benefits these structures provide likely to be greater for estuaries lacking naturally complex habitats. [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]

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]

The land-based recirculating aquaculture system (RAS) has been widely applied to fish farming as a new eco-friendly culture model. This system consists of circular culture tanks on land integrated with water treatment and recycling systems. This study investigated the growth performance of juvenile gibel carp (Carassius gibelio) cultured at high stocking density (HSD, 0.3 kg/m3) and low stocking density (LSD, 0.15 kg/m3) conditions in RAS, and evaluated the comprehensive economic profit of RAS. The body weight, body length, weight gain rate, and condition factor of gibel carp in the LSD group were significantly higher than those in the HSD group (p < 0.05). The feed conversion ratio increased significantly in the HSD group (p < 0.05). A histological analysis revealed a significantly higher density of white muscle fibers in the LSD group (p < 0.05). Relative mRNA expression levels showed that ubiquitin–proteasome system (UPS)-related genes, ub, psma2, and mafbx, were significantly expressed in the HSD group, while the s6k1 expression was elevated in the LSD group (p < 0.05). The mRNA expression levels of keap1 and hsp70 in the dorsal muscle were significantly higher in the HSD group (p < 0.05). Throughout the rearing period, the water temperature remained consistent between the two density groups. The pH value gradually decreased and the dissolved oxygen levels in the HSD group were generally lower than in the LSD group. The nitrite nitrogen (NO2−-N) content was higher in the HSD group. Compared to the LSD group, the return on investment was significantly lower in the HSD group. In conclusion, the water quality and growth rates of juvenile gibel carp were better in the LSD group. An appropriate stocking density improved the growth performance and aquaculture economic efficiency. [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]

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]

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]

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]

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]

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]

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]

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]

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]

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 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]

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]

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]

ABSTRACT Fish stocking continues to be an important and often‐used tool in fisheries management. Mortality of fish may be high in the first few days after stocking due to predation and a lack of appropriate food and habitat. The objective of this study was to develop a conceptual model that may identify stocking locations that can help improve the survival of stocked fish. We identified three factors—predator risk, zooplankton (food) availability and measures of habitat that could be important to the survival of stocked Walleye (Sander vitreus) and White Bass (Morone chrysops) fingerlings in Lake McConaughy, Nebraska. The spatial distribution of these factors was used to create a predictive surface to identify those stocking locations hypothesised to lead to higher survival. Final stocking maps identified the best 12.8% and 13.9% of the predicted area of Lake McConaughy for stocking Walleye and White Bass, respectively. Both maps predicted that the best locations were along the south‐central shoreline of Lake McConaughy. The maps for both species were interestingly similar. These results are likely due to the similarities in predators consuming the stocked species and the zooplankton consumed by fingerlings of both species. Habitat availability may be less important, or other aspects of habitat may need to be considered. Identifying the best locations for stocking based on predation risk and the availability of food and habitat could increase the survival of stocked fishes and help managers reach population objectives.

Biofloc technology (BFT) is one of the innovative methodologies for waste management and nutrient retention that offers a solution to solve environmental problems in aquaculture, because it doesn't use water exchange to solve nitrogen compound elimination, but it utilizes microbial assimilation, stimulated for addition of material rich in carbon, to transform those compounds. However, two trials of ten months period each (2021-2023) were performed to investigate the growth and production of Singhi in fresh water Biofloc System at Krishi Vigyan Kendra, IGKV, Raipur, Chhattisgarh, India. Three circular and rectangular cemented tanks (10,000 liter capacity each) were used in each trial under this purpose. Probiotic was used for developing beneficial bacterial colonies and controlling ammonia in confined water system. Healthy advanced fry of Singhi (Avg weight 1.3 g) were stocked @ 1500 nos/tank with treatment of potassium permanganate. Floating feed with 40-45% protein level was fed in twice in a day by following standard feeding chart. Molasses was applied for proper microbial growth and maintained C:N ratio. Physico-chemical parameters were studied weekly and maintained properly during whole period. Floc volume range was recorded between 13-33 ml/liter water sample, FCO was periodically applied for bacterial growth. The average yield was recorded 212.50 kg/tank after a period of 11 months from stocking, average growth was 154 g and FCR was found to be 1.3. Experiments were conducted during 2021-2023, so the variation of temperature was very high. The other important parameters recorded were-average pH value 7.6, dissolved oxygen 5.7 ppm, TDS 684 ppm and C:N ratio 12:1. Probocare & Medifish unique were applied weekly @ 75 ml/tank for maintaining floc and water parameters as well. Unique growth was applied @ 100 g/tank as growth promoter in fortnight interval. The results obtained in this experiment suggest that the biofloc system in fresh water aquaculture improves growth performances of Singhi in almost zero-water exchange system. [ABSTRACT FROM AUTHOR]