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This study aimed to compare the growth performance and economic profitability of rearing Oreochromis niloticus in floating cages using three feeding strategies (5 days a week, 6 days a week, and 7 days a week) coupled with three stocking densities (20, 40, and 60 fish·m−3). Male monosex fish measuring 6.44 ± 0.18 cm and weighing 3.42 ± 0.7 g were used. The controls were weighed every 15 days from the 35th day of rearing until 185 days to assess zootechnical parameters. BioMar feed (Efico Cromis 832F) was used during the study, and the feed ration was adjusted for each treatment every 2 weeks. At the end of the study, the average weights varied from 293.09 g to 468.41 g for the conditions of 40 fish·m−3 with a 5/7-day diet and 20 fish·m−3 with a 7/7-day diet, respectively. The yield per m2 values were between 7.11 kg and 23.17 kg, respectively. On the other hand, the economic profitability was better with the condition of 40 fish.m−3 with daily feeding. These results suggest that in the Toho-Todougba lagoon complex, a stocking density between 40 and 60 fish·m−3 coupled with daily feeding (three times a day) promotes the optimization of fish production and profitability of fish farming. [ABSTRACT FROM AUTHOR]

Domestic herbivores have been closely associated with the historical evolution and development of agriculture systems worldwide as a complementary system for providing milk, meat, wool, leather, and animal power. However, their major role was to enhance and maintain agricultural soil fertility through the recycling of nutrients. In turn, cereal production increased, enabling to feed a progressively increasing human population living in expanding urban areas. Further, digestion of organic matter through the rumen microbiome can also be viewed as enhancing the soil microbiome activity. In particular, when animal droppings are deposited directly in grazing areas or applied to fields as manure, the mineralization–immobilization turnover determines the availability of nitrogen, phosphorus, potassium, and other nutrients in the plant rhizosphere. Recently, this close coupling between livestock production and cereal cropping systems has been disrupted as a consequence of the tremendous use of industrial mineral fertilizers. The intensification of production within these separate and disconnected systems has resulted in huge emissions of nitrogen (N) to the environment and a dramatic deterioration in the quality of soil, air, and ground- and surface water. Consequently, to reduce drastically the dependency of modern and intensified agriculture on the massive use of N and phosphorus (P) fertilizers, we argue that a close reconnection at the local scale, of herbivore livestock production systems with cereal-based cropping systems, would help farmers to maintain and recover the fertility of their soils. This would result in more diverse agricultural landscapes including, besides cereals, grasslands as well as forage and grain crops with a higher proportion of legume species. We developed two examples showing such a beneficial reconnection through (i) an agro-ecological scenario with profound agricultural structural changes on a European scale, and (ii) typical Brazilian integrated crop–livestock systems (ICLS). On the whole, despite domestic herbivores emit methane (CH4), an important greenhouse gas, they participate to nutrient recycling, which can be viewed as a solution to maintaining long-term soil fertility in agro-ecosystems; at a moderate stocking density, ecosystem services provided by ruminants would be greater than the adverse effect of greenhouse gas (GHG). [ABSTRACT FROM AUTHOR]

Rice-fish cultivation, also known as Manipadi in Indonesia, is one of the many integrated farming systems where fish are grown concurrently with rice. However, this integrated system needs to be optimized by organic fertilizer. The application of organic fertilizers, such as compost and local biofertilizers, when implemented into this integrated system, can optimize the yield per land for both rice and fish. However, this combination must be evaluated systematically by multiple evaluation criteria and statistical analyses. Therefore, this study aimed to identify the combination of compost doses and/or local liquid organic fertilizer concentrations, based on multiple evaluation criteria, that supports the productivity of rice-fish integration agriculture. The experiment was carried out in the Wanuae farmer group of the Barebbo District, Bone Regency, Indonesia, between September 2018 and January 2019. The experiment employed a split plot design with a randomized complete block design (RCBD). The main plot consisted of compost (four levels), and the subplot was the local biofertilizer source (four levels). The results demonstrated that the number of fill grains was significantly affected by the compost treatment and the type of local biofiller. The effect of the compost dosing was more dominant in comparison with the local liquid organic fertilizer character and its interactions. A compost dosage of four tons ha−1 and a local liquid organic fertilizer, sourced from soaked coconut fiber with cow urine, has been recommended as the combination treatment to optimize the rice and fish yield potential. The Minapadi (rice fish) with additional high composting effectively increased the farmer's outcome with a 2-point R/C ratio, more so than those without composting. Moreover, the compost dosage in this Minapadi study requires further exploration for a better understanding. [ABSTRACT FROM AUTHOR]

The vital goal of aquaculture genomics, genetics and genomic editing is to enhance production efficiency in aquaculture sector. Rainbow trout (RBT) Oncorhynchus mykiss is a native species from the northwest coast of North America and it belongs to salmonid family. Rainbow trout is an important species in, wild stock fisheries and recreational sport fisheries in Aquaculture sector and RBT is valued for superior growth. Muscle is a molecular motor and muscle mass of livestock is crucial in food industry. Some studies reported the non-coding RNAs gene expression in muscle tissues of healthy and unhealthy (affected by muscle deterioration and muscle atrophy) fishes. During vitellogenesis, significant loss of muscle mass and sufficient muscle proteins accumulate in developing ova. This change throws a glimpse on general pattern of muscle wastage supporting RBT as an ideal model to illuminate muscle catabolism molecular mechanism. This review reports the differentially expression of microRNAs and lncRNAs of rainbow trout muscle tissues in the healthy and unhealthy fishes. [ABSTRACT FROM AUTHOR]

Ecosystem-based management is costly. Therefore, without rigorously showing that it can outperform traditional species-focused alternatives, its broad-scale adoption in conservation is unlikely. We present a large-scale replicated and controlled set of whole-lake experiments in fish conservation (20 lakes monitored over 6 years with more than 150,000 fish sampled) to examine the outcomes of ecosystem-based habitat enhancement (coarse woody habitat addition and shallow littoral zone creation) versus a widespread, species-focused alternative that has long dominated fisheries management practice (i.e., fish stocking). Adding coarse woody habitats alone did not, on average, enhance fish abundance, but creating shallow water habitat consistently did, especially for juvenile fish. Species-focused fish stocking completely failed. We provide strong evidence questioning the performance of species-focused conservation actions in aquatic ecosystems and instead recommend ecosystem-based management of key habitats. [ABSTRACT FROM AUTHOR]

The objectives of the present study were to evaluate the potential of the Korill (KO), a product based on krill oil, supplemented in fish feed (5 g/kg feed) to alleviate density-induced stress in carp fingerlings, and its protective capacity in case of anthelmintic drug administration (ABZ—albendazole). Thus, the fish were divided into four groups: LD (low density with normal feed), LD-KO (low density with KO supplementation feed), HD (high density with normal feed), and HD-KO (high density with KO supplementation feed). During the first trial, the fish held under different densities were fed normal feed and KO feed for two months, following a 2 × 2 factorial experimental design. In the second trial, seven fish per tank were subjected, for one week, to albendazole treatment (administered daily by an oral dose of 5 mg/kg body weight). For both trials, blood and plasma samples were used to quantify hematological and biochemical parameters. The results showed that the KO diet alleviated the negative impact of ABZ treatment on liver function and the metabolic profile of carp fingerlings reared in high densities. In addition, KO feeding improved lysozyme activity (LZM) and therefore the immune status of the fish, and reduced oxidative damage in the liver, demonstrated by a decrease of malondialdehyde (MDA) content and an increase of total antioxidant capacity (TAC). [ABSTRACT FROM AUTHOR]

Water quality improvement was carried out by means of recirculation and bioremediation systems in grouper nurseries with high stocking density, thereby increasing production performance. The goal of this study was to evaluate the effectiveness of aquabusiness by analyzing the rise in grouper nursery stocking density using RAS and bioremediation systems. The test parameters consist of production performance, blood glucose levels, physic-chemistry-biology of water quality, and business efficiency based on productivity and business analysis. Treatment of 1,000 fish/m³ increased survival, blood glucose levels, total bacteria, Vibrio spp., ammonia, nitrite, and all productivity parameters. But it lowers all growth parameters, pH, and dissolved oxygen values. The recirculation system with bioremediation at up to 1,000 fish/m³ of stocking boosted the profit by 2.64 times. and 14.97% more efficient than 500 fish/m³ which could not be matched by the high production performance. [ABSTRACT FROM AUTHOR]

In the welcome circumstance that species believed extinct are rediscovered, it is often the case that biological knowledge acquired before the presumed extinction is limited. Efforts to address these knowledge gaps, in particular to assess the taxonomic integrity and conservation status of such species, can be hampered by a lack of genetic data and scarcity of samples in museum collections. Here, we present a proof‐of‐concept case study based on a multidisciplinary data evaluation approach to tackle such problems. The approach was developed after the rediscovery, 40 years after its presumed extinction, of the enigmatic Lake Constance deep‐water charr Salvelinus profundus. Targeted surveys led to the capture of further species and additional sympatric normal charr, Salvelinus cf. umbla. Since the lake had been subject to massive stocking in the past, an evaluation of the genetic integrity of both extant forms was called for in order to assess possible introgression. A two‐step genomic approach was developed based on restriction site associated DNA (RAD). Diagnostic population genomic (single nucleotide polymorphism [SNP]) data were harvested from contemporary samples and used for RNA bait design to perform target capture in DNA libraries of archival scale material, enabling a comparison between extant and historic samples. Furthermore, life history traits and morphological data for both extant forms were gathered and compared with historical data from the past 60–120 years. While extant deep‐water charr matched historical deep‐water specimens in body shape, gill raker count, and growth rates, significant differences were discovered between historical and extant normal charr. These resulted were supported by genomic analyses of contemporary samples, revealing the two extant forms to be highly divergent. The results of population assignment tests suggest that the endemic deep‐water charr persisted in Lake Constance during the eutrophic phase, but not one of the historical genomic samples could be assigned to the extant normal charr taxon. Stocking with non‐endemic charr seems to be the most likely reason for these changes. This proof‐of‐concept study presents a multidisciplinary data evaluation approach that simultaneously tests population genomic integrity and addresses some of the conservation issues arising from rediscovery of a species characterized by limited data availability. [ABSTRACT FROM AUTHOR]

Plankton is major food item for Nile tilapia and their availability is one of the most important factors affecting its growth performance in an extensive and semi-intensive pond-based culture systems. Thus, this study aimed to examine plankton composition, abundance, and feeding preference by Nile tilapia reared under a semi-intensive pondbased production system. The experiment was carried out using ponds (10mx15mx1.7m size) fertilized with chicken manure at the rate of 100g/m2/week. Nile tilapia with 7.8g average body weight was stocked at a density of 2 fish/m2. Examination of plankton from both pond water and stomach samples of fish was done using qualitative assessment methods. The results showed that a total of 20 phytoplankton groups were identified following standard identification key. These include four types of Blue-green algae (Cyanophyceae), seven types of Green algae (Chlorophyceae), six Diatoms (Bacillariophyceae), one type of Dinophyceae, and two types of Euglenophyceae. Among the phytoplankton groups, Chlorophyceae was the dominant group with 56% followed by Bacillariophyceae (23%), Cyanophyceae (17%), and Euglenophyceae (3%) while the least was Dinophyceae (1%). The most frequently observed algal genus was Scenedesmus. In addition, three Zooplankton groups namely Copepods (43%), Rotifers (31%) and Cladocerans (26%) were also identified. The result indicated that, the most preferred planktonic groups used by Nile tilapia was green algae, particularly Chlorophyceae followed by Copepoda and Rotifers. The level of chlorophyll "a" was 62.3±2.0 µg/l concentration. The different water quality parameters together with the availability of different plankton were optimal for the growth of Nile tilapia which resulted in a 0.45 specific growth rate. In conclusion, Nile tilapia exhibit preference for green algae, blue-green algae from phytoplankton, and Copepods from zooplankton groups than other groups of plankton. [ABSTRACT FROM AUTHOR]

Rapidly increasing hatchery-raised Nile tilapia (Oreochromis niloticus) in most developing countries lack informed recommended fingerling weight for stocking in semi-intensive grow-out ponds. The current study assessed the growth performance, survival and productivity of all-male Nile tilapia fingerlings of 0.2 g, 1 g, and 5 g in an on-farm experiment. The final mean weight of fingerlings stocked at size 5 g was significantly higher (113.80±4.21 g) (P<0.05) compared to the 0.2 g (36.99±1.14 g) and 1g (91.93±5.59 g) fingerling sizes. The mean daily weight gain was highest in 5 g stocked fingerlings (0.91±0.04 g day -1) resulting in significant differences in the final mean weight. The coefficient of correlation between fish body length and weight was high and positive ranging (R=0.95-0.98). Significantly low percent survival was recorded in 0.2 g stocked fingerlings (64.4 3±1.93%). The net annual fish yield (NAY) and profit index (PI) were significantly lower at the 0.2 g. The highest NAY and PI were recorded in the 5 g stocked fingerlings (8.59±0.09 tons ha-1 year-1 and 6.6±2.08), respectively. Thus, with appropriate Nile tilapia fingerling weight at stocking, fish farmers can maximize fish growth, yield and profits. [ABSTRACT FROM AUTHOR]

Field trials were conducted to assess the potential for stocking native unionid mussels in urban streams of the Chesapeake Bay catchment. Juvenile, hatchery‐raised mussels were placed in enclosures at five urban streams (two restored and three unrestored) and two nearby rural streams. Adult mussels were translocated to two restored urban streams. Mussel growth and survivorship were assessed at the stream sites and for individuals maintained at hatchery ponds.At all sites, water quality conditions were generally suitable for mussels with respect to temperature, pH, and dissolved oxygen. Food resources, as indicated by the quantity and quality of suspended and benthic particulate matter, were higher among rural sites and lower in unrestored urban streams.Positive growth rates were observed at all sites, among both juveniles (caged) and translocated adults. Mussel fatty acid profiles were generally similar among sites, except for docosahexaenoic acid (DHA), which was lower among stocked mussels relative to mussels maintained at the hatchery.Among the unrestored urban streams, the frequent occurrence of high discharge events resulted in burial and downstream loss of enclosures. At restored urban streams and rural streams, the washout effects were less severe. Apart from washout effects, mortality, as indicated by the presence of dead mussels, was low (<10%).Overall, rural and restored urban streams provided suitable conditions for stocking native mussels, whereas in unrestored urban streams, bed and bank instability during high discharge events resulted in a high attrition of mussels. Conservation efforts may be aided by the consideration of mussel habitat needs in the design of stream restoration projects. The inclusion of mussel stocking efforts in urban stream restoration projects has the potential to facilitate stream recovery, expand and bring greater attention to mussel conservation efforts, and garner public support for the preservation of stream health in urban areas. [ABSTRACT FROM AUTHOR]

Stocking of native and non-native fish species is a widespread practice commonly used to enhance inland recreational fisheries, appropriate when intense harvesting and the degradation or lack of suitable habitat decrease the abundance of the managed species below carrying capacity. In spite of its popularity, this practice is often poorly informed by scientific information. Salmonids are arguably the most popular and commercially valuable freshwater fishes being managed for recreational fisheries. Stocking of both native and non-native taxa has been practiced for almost two centuries in Europe, dramatically altering the structure and function of riverine and lacustrine ecosystems. In the Verbano-Cusio Ossola Province, northern Italy, within the Lake Maggiore catchment, we measured large numerical mismatches between stocking of cultured native (Salmo marmoratus) plus non-native trout taxa (S. trutta, S. ghigii, Oncorhynchus mykiss) and the number of fishes captured by local anglers. These observations highlight the need for future studies to estimate the stocking effectiveness of S. marmoratus, a critically endangered species of significant cultural and economic value.

Simple Summary: The development of skeletal anomalies in the early life stage of gilthead seabream (Sparus aurata) poses a significant challenge for farmers, affecting their profit margins, animal welfare, and the consumers' perception of the aquaculture industry. Although many factors have been considered to be causative in the development of skeletal anomalies in marine finfish, the stocking density and available swimming space represent two key parameters which can be easily manipulated by the farmers during the critical phase of pre-ongrowing (prior to being placed in sea cages). This work aims at distinguishing which among tank volume and stocking density is the driving factor eliciting the development of skeletal anomalies during the pre-ongrowing phase in gilthead seabream, a productive cycle in which many skeletal anomalies can arise, particularly those affecting the vertebral axis. The results from this work indicated that particular cranial and axis deformities affected fish in higher incidences when they were reared at higher densities. The results are discussed through an eco-evo-devo approach in relation to the potential mechanisms at play affecting the increased prevalence of skeletal anomalies found. This research represents an intriguing contribution to aquaculture with results that can be applied directly to the production methods used by fish farmers to ameliorate the skeletal and morphological quality of farmed gilthead seabream. Gilthead seabream (Sparus aurata) production is a highly valued aquaculture industry in Europe. The presence of skeletal deformities in farmed gilthead seabream represents a major bottleneck for the industry leading to economic losses, negative impacts on the consumers' perception of aquaculture, and animal welfare issues for the fish. Although past work has primarily focused on the hatchery phase to reduce the incidence of skeletal anomalies, this work targets the successive pre-ongrowing phase in which more severe anomalies affecting the external shape often arise. This work aimed to test the effects of: (i) larger and smaller tank volumes, stocked at the same density; and (ii) higher and lower stocking densities maintained in the same water volume, on the skeleton of gilthead seabream fingerlings reared for ~63 days at a pilot scale. Experimental rearing was conducted with gilthead seabream juveniles (~6.7 ± 2.5 g), which were selected as 'non-deformed' based on external inspection, stocked at three different densities (Low Density (LD): 5 kg/m3; Medium Density (MD): 10 kg/m3; High Density (HD): 20 kg/m3) in both 500 L and 1000 L tanks. Gilthead seabream were sampled for growth performance and radiographed to assess the skeletal elements at the beginning and end of the experimental trial. Results revealed that (i) LD fish were significantly longer than HD fish, although there were no differences in final weights, regardless of the water volume; (ii) an increase in the prevalence of seabream exhibiting cranial and vertebral axis anomalies was found to be associated with increased density. These results suggest that farmers can significantly reduce the presence of some cranial and axis anomalies affecting pre-ongrown gilthead seabream by reducing the stocking density. [ABSTRACT FROM AUTHOR]

Background: Streptococcal infections are one of the main causes of fish disease. During the last decade, Streptococcus iniae has become one of the most important aquatic pathogens worldwide, causing high losses in marine and freshwater finfish. Clinical signs in farmed fish include loss of appetite, lethargy and grouping at the bottom of the tank. Gross changes comprise darkening of the skin and haemorrhage at the basis of fins and opercula. To date, S. iniae has been isolated from several wild and farmed fish species but never in the European eel (Anguilla anguilla). In Europe, eel production from aquaculture is around 4500 tonnes and Italy is the third largest producer. This communication represents the first report of an outbreak of S. iniae infection in European eels. Case presentation: The outbreak occurred at an eel farm in northern Italy between May 2021 and September 2021. The outbreak caused about 2% mortality per month, resulting in the loss of about 10% of the farmed fish. The diseased eels showed apathy, lethargy, inactivity and inappetence. In July 2021, three eels were necropsied. Necropsy revealed skin and branchial hyperaemia, a few skin ulcers, and diffuse peritoneal congestion with a few haemorrhagic-like spot lesions. Swab samples for bacteriology were taken from the kidneys, liver, spleen, and brain. Additionally, four eels were opened and swap samples as above were taken. All the investigated eels were found dead. Bacteriological examination revealed growth of Streptococcus spp. from all samples. Identification of S. iniae was done by biochemical characterization, the API20STREP microsystem, 16S rDNA sequencing, and MALDI-TOF. Antimicrobial therapy (oxytetracycline and erythromycin) was ineffective. Conclusions: This is the first report of S. iniae infection in the European eel. Although this may be an isolated outbreak, it is of concern due to the losses associated with this pathogen in fish worldwide and because the European eel is an endangered species. Due to the difficulties of controlling the disease with antimicrobials, it is advisable to plan other effective control measures, such as improving water quality and the environmental conditions, reducing fish density, improving biosecurity, and by using immunostimulants and, when possible, vaccines. [ABSTRACT FROM AUTHOR]

The U.S. catfish industry is seeking production systems that are efficient, intensive, and profitable. Growing foodsize and stocker-sized fish in the same pond is attractive as it is often difficult to obtain larger-sized stockers early each year. This case study evaluated the performance and economics of producing foodsize hybrid catfish and stocker-sized fingerlings in in-pond raceway systems (IPRS) placed into four 0.4 ha ponds. Growout raceways (RW1/RW2) in ponds 1 and 2 were 63 m3, and 45 m3 in ponds 3 and 4 (RW3/RW4). Each pond had one (14 m3) stocker unit raceway and a 5 HP of aeration that maintained adequate dissolved oxygen levels. Average growout production was 12,050 kg/ha in 63 m3 raceways and 12,078 kg/ha in 45 m3 raceways (228 days of production) and achieved harvest weights ranging from 564 to 661 g. The raceway stocker unit had production yields ranging from 3537 to 4388 kg/ha (143 days of production) and achieved harvest weights ranging from 123 to 234 g. Stocker units in ponds 1 and 2 generated 8540 stocker–fingerlings (21,102 fingerlings/ha) and units in ponds 3 and 4 generated 7954 fingerlings (19,654 fingerlings/ha). An investment of USD 39,996 was needed for ponds 1 and 2 and USD 21,196 for ponds 3 and 4. When scenarios were analyzed financially, positive financial net returns occurred when farm level investment decreased, leading to reduced payback periods, increased net present values, and higher internal rates of return. IPRS used stocker units to culture fingerlings for future stocking of foodsize fish. IPRS provided good inventory control, and high production yields compared to traditional pond culture of catfish. [ABSTRACT FROM AUTHOR]

The effects of semi-intensive (100 kg m−3), intensive (200 kg m−3), and super-intensive (400 kg m−3) stocking densities on the growth and welfare of African catfish (Clarias gariepinus) were investigated under commercial production conditions. Plasma cortisol, glucose, and selected transcripts following a stress challenge, lactate, as well as skin lesions, were analyzed at regular intervals (from 12 g juveniles to 1.5–2.0 kg). The fish grew well, but after 23 weeks, the semi-intensively stocked fish had a mean final weight of 1830.5 g, significantly higher than the super-intensively stocked fish with 1615.4 g, and considerably higher than the intensively stocked fish with 1664.8 g (p > 0.05). Cortisol and glucose responses significantly differed between stressed and unstressed fish, but not between treatment groups. An unforeseen external stressor (nearby demolition noise) caused stress responses among all treatment groups, but was similarly coped with. Mortality ranged between 3.8–9.2%. In the juveniles, skin lesions were reduced under intensive or super-intensive densities, with the least under semi-intensive densities in outgrown fish. Expression profiles of 22 genes were compared in the spleen at semi-intensive and super-intensive densities. The transcript concentrations of most genes remained unchanged, except for slc39a8 and mtf1, which were significantly downregulated in stressed catfish under semi-intensive conditions. We demonstrated that African catfish growth performance and welfare depend on age and stocking density, also reacting to demolition noise. This supports farm management to optimize stocking densities during the grow-out of African catfish in RAS and suggests avoiding external stress. [ABSTRACT FROM AUTHOR]

The Chinese pond mussel Sinanodonta woodiana (Lea, 1834) (Bivalvia: Unionidae) is among the most invasive freshwater species worldwide. The last decades have seen its rapid geographical spread beyond the species' natural range, particularly in anthropogenically modified water bodies across Asia, America, and Europe where it is now very common. In this paper, we also confirm the presence of S. woodiana in Africa (Algeria) by establishing the UNESCO Biosphere Reserve and Ramsar site Oubeira Lake as a new locality for its occurrence. In all likelihood, S. woodiana was accidentally introduced in the 1980s with Asian fish species imported from Hungary for stocking purposes. The present survey was conducted in the summer of 2020, and here we present the first data on several biological aspects of 141 S. woodiana specimens collected in the lake fringe area. The age structure varied from two to over height years old; medium- and large-sized individuals with shell lengths ranging from 102.23 to 183.55 cm accounted for 96% of sampled mussels. A study of the conchological features revealed that bivalves adopt the species' typical morphological trends. Overall, our findings showed that S. woodiana succeeded in establishing a viable population in Oubeira Lake, which allows for the assumption that additional records can be predicted at a regional scale in locations related to the lake water system in Algeria and Tunisia. [ABSTRACT FROM AUTHOR]

Context. The Murray--Darling Basin -- Australia's largest river system -- is heavily dominated by alien fish. Native fish species have suffered numerous localised extinctions and ~47% are listed on federal and/or state threatened species lists. Aims. This paper explores the hypothesis that alien fish and alien fish stockings can be the primary cause of decline and localised extinction of large-bodied native fish species, as opposed to habitat degradation and river regulation. The Lower Goodradigbee River, which is unregulated, in excellent instream health over the great majority of its course, and replete with high quality habitat, is utilised as a case study. Methods. I investigated the hypothesis by synthesising historical records with contemporary scientific research and recent field observations. The role of alien fish species, particularly alien trout species (Oncorhynchus mykiss and Salmo trutta) and constant stockings of them, were closely examined. Results. Data support the hypothesis that domination by alien trout species and their continual stocking have lead to historical declines and localised extinctions of large-bodied native fish species. Continued alien trout stockings, along with more recent invasions of alien carp (Cyprinus carpio) and alien redfin perch (Perca fluviatilis), are inhibiting native fish recovery. A suspected field sighting of the alien fish pathogen atypical Aeromonas salmonicida is reported, and the status of the declining native crayfish Murray cray (Euastacus armatus), and potential alien fish impacts upon them, are examined. Conclusions. The impacts of alien fish and alien fish stocking in Australia require major re-evaluation and dedicated research. Implications. It is strongly recommended that stocking of alien trout into the Lower Goodradigbee River for angling cease in order to conserve surviving native fish and Murray cray populations. Conservation stockings to effect a Murray cod (Maccullochella peelii) recovery in the Lower Goodradigbee River are warranted. [ABSTRACT FROM AUTHOR]

Here we list species-specific recommendations for housing, care and management of cephalopod molluscs employed for research purposes with the aim of contributing to the standardization of minimum requirements for establishments, care and accommodation of these animals in compliance with the principles stated in Directive 2010/63/EU. Maximizing their psychophysical welfare was our priority. General recommendations on water surface area, water depth and tank shape here reported represent the outcome of the combined action of the analysis of the available literature and an expertise-based consensus reached – under the aegis of the COST Action FA1301 – among researchers working with the most commonly used cephalopod species in Europe. Information on water supply and quality, environmental conditions, stocking density, feeding and handling are also provided. Through this work we wish to set the stage for a more fertile ground of evidence-based approaches on cephalopod laboratory maintenance, thus facilitating standardization and replicability of research outcomes across laboratories, at the same time maximizing the welfare of these animals. [ABSTRACT FROM AUTHOR]

A synergy model of the aquaponic system was integrated with soil-based cultivation, particularly for the recycling use of aquaculture wastewater and solids. A three-way water cycle process was also designed in this study. A pilot system was built at Yaomo village, Ningxia Hui Autonomous Region, China in 2020. Three parts were composed mainly of the recirculating aquaculture system (RAS), hydroponics, and soil-based cultivation unit, specifically including the fish tank, radial-flow clarifier, micro-screen drum filter, moving bed biofilm reactor (MBBR), mineralization tank, ultraviolet sterilizer, sump tank, hydroponic troughs, and farmland. In a three-way water cycle process, the first way was a circulation loop of the RAS unit, where the effluent first went through the physical filters under gravity, and then lifted into the MBBR by pump to remove ammonia nitrogen, and nitrate. Finally, the water flowed into the ultraviolet sterilization, and then returned to a fish tank. The second way was a circulation loop of “aquaculture unit to hydroponics unit”, where the aquaculture effluent was loaded with the nutrients, filtered into the hydroponic troughs where the plant roots were fertilized, then recycled back to the fish tank, and remediated cumulated nutrients. The third way was the “aquaculture unit to soil-based cultivation unit” cycle, where the fish sludge solids were accumulated into the mineralization tank, and then irrigated to the farmland after being mineralized by the pump. In the RAS unit, the respiration and metabolism of fish and the decomposition of the residual feed produced ammonia nitrogen and then converted to nitrate nitrogen under the effect of microorganisms in the MBBR and on the surface of plant roots. In the hydroponics unit, the plants absorbed nitrate nitrogen produced from the RAS unit, and then purified the aquaculture wastewater. In the soil-based cultivation unit, the fish sludge solids (mainly composed of degradable organic matter) were degraded to small molecules in a mineralisation tank, whereas, the macronutrients (i.e. N, P, and K) and micronutrients (i.e. Fe, Mn, and Zn) that were bound to the organic molecules were released into the water in their ionic forms to complete the process of nutrient mineralization. The key parameters (including the biomass ratio of fish and vegetables) were calculated to propose the capacity of the mineralization device. According to the calculation, the system was designed to farm 1 400 kg fish in a tank of 28.3 m³, to plant 3 648 vegetables in 96 circular pipes each of 8 m, and the mineralization tank volume was set to 2 m³ . Taking the largemouth bass as the case, the lettuce and tomato as the culturing object for 160 days from May 21st to October 28th. The experiment results showed that better growth of fish was achieved, where the final culture density reached up to 41.6 kg/m³, the specific growth rate was 0.42%, the survival rate was 99.95%, and the feed coefficient was 1.4. The better growth of vegetables was also obtained, where 1205 kg of hydroponic lettuce and 2 400 kg of tomato were harvested during the period. Consequently, the water quality was stable: the average concentration of total ammonia nitrogen (TAN) was (0.83±1.46) mg/L, the average concentration of nitrite (NO2 - -N) was (0.035±0.062) mg/L, the average concentration of nitrate (NO3 - -N) was (25.1±8.06) mg/L, the concentration range of dissolved oxygen was 4.25-7.16 mg/L, and the average pH was 6.8. More importantly, the average concentration of total phosphorus and potassium in water increased by 141% and 7%, respectively, during the mineralization process. The excellent economic and ecological benefits of the system were obtained: the annual profit was about 46 000 Yuan, the use of chemical fertilizers was reduced by 4/5, the use of pesticides was reduced by 3/4, and the daily water exchange was less than 5%. [ABSTRACT FROM AUTHOR]

The study investigated the management practices that contribute to disease outbreaks in farmed tilapia in Lusaka and central and southern provinces in Zambia. It was a cross-sectional qualitative study undertaken from January to March 2021 in which questionnaires were administered to 49 farmers to assess their fish health management and biosecurity competence. Data were analysed using means, percentages, ratios, and logistical regression. The results showed that the majority of the farms had high stocking densities (>8 fish/m2, 44.4%), reared Nile tilapia (67.7%), and sourced water for farming from rivers and streams (45.7%). A few farmers measured water quality parameters daily (16.7%) and removed dead fish from ponds daily (20.8%). The stocking density (p = 0.013), fish species (p = 0.031), dead fish disposal methods (p = 0.023), and control of predator birds (p = 0.016) influenced the total mortality recorded on farms, while pond type (p = 0.031 and p = 0.045), water source (p = 0.023), and stocking density (p = 0.027) influenced the duration of a mortality episode. It is evident that some fish health management practices and biosecurity concepts among tilapia farmers in the study area are inadequate and may not contain disease outbreaks or the spread of pathogens. [ABSTRACT FROM AUTHOR]

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive pest species that uses a wide variety of commercial fruit as a breeding and feeding resource. The damage to the fruit generated by D. suzukii´ oviposition causes considerable economic losses. Therefore, the maintenance of D. suzukii in the lab conditions constitutes a fundamental tool for research proposal. Two of the determining factors affecting the lab rearing conditions are the culture medium and density. In this study, we evaluated the impact of these factors on three components associated with fitness: development time, larval-adult viability and body size, comparing the effects of three culture media: cornmeal (polenta), mashed potato and plum when the flies were reared at three densities: 10, 30 and 50 larvae per 5ml of culture medium. Our results revealed that the flies reared the cornmeal culture medium and at lower densities provide the better conditions for the maintenance of D. suzukii under lab conditions. [ABSTRACT FROM AUTHOR]

Aquaponics is the cultivation of fish and plants in a series of systems, either in one container or in separate containers, by paying attention to the balance between fish, plants, and aquatic microorganisms. One of the obstacles in aquaponic activities is that vegetable growth is not optimal due to a lack of dissolved nutrients, so further research is needed to make better plant growth. This study aimed to evaluate catfish and water spinach growth performance in an aquaponic system by adding AB mix nutrients at different fish stocking densities. This study used a completely randomized design with three differences in stocking densities of catfish (150 fish/m³, 200 fish/m³, and 250 fish/m³ ) as test animals with four replications where AB mix was added to each treatment. The growth performance of catfish is better in control with a stocking density of 250 fish/m³ and without adding nutrients. The growth performance of catfish decreased with the addition of AB mix nutrients, while the growth of water spinach was better. The growth rate of catfish without adding AB mix nutrients was higher than in other treatments. In contrast, all treatments with the addition of AB mix increased the growth performance of water spinach, with the stocking density of catfish not affecting the growth of water spinach plants. [ABSTRACT FROM AUTHOR]

The objective of the current study was to determine the effect of two fish stocking densities on the growth performance, development, and antioxidant capacity of kale (Brassica oleracea L. var. acephala) and arugula (Eruca vesicaria ssp. sativa) in an aquaponic system with common carp (Cyprinus carpio). The aquaponics system consists of six rearing units for fish and twelve units for plants, purple light-led lamps for plants (36 W), biological and mechanical filters, and pumps for water recirculation. Two fish stocking densities were used: 3.5 kg×m-3 and 7 kg×m-3, each replicated three times. For each treatment or fish stocking density, 15 kale seedlings (51 plants×m-2) and 15 arugula seedlings (51 plants×m-2) were planted. All treatments were done in triplicates. At the end of the trial, the fresh weight of the plants was measured, and the results showed that the stocking density of the common carp of 7 kg×m-3 resulted in higher production of kale and arugula by maintaining good water quality for the plant and fish. [ABSTRACT FROM AUTHOR]

To support preparation of a forthcoming Committee on the Status of Endangered Wildlife in Canada (COSEWIC) review, this report assembles data on Atlantic Salmon (Salmo salar) biology, demographics, habitat, and threats for Prince Edward Island (PEI) (Salmon Fishing Area 17). Historical accounts indicate that the original PEI Atlantic Salmon population was dominated by late-run and large (= 63 cm) fish. These characteristics are retained in small rivers. At least 38,826,353 Atlantic Salmon have been stocked in PEI in 1880 - 2020, mostly in larger rivers. The proportion of early-run and small Salmon has been increased in larger rivers by the stocking of fish intended to increase summer angling opportunities. Sea ages of returning adults are generally one year for small Salmon and two years for large Salmon. Return rates for fish of hatchery origin range from 0.5 to 5.9%. Data on return rates of naturally spawned fish are unavailable. In the Morell River, PEI's traditionally most important Salmon river, mean fecundity is 3,143 eggs for small Salmon and 4,963 eggs for large Salmon. The egg phase (1 year), juvenile phase (mean 2.32 years), and sea phase (mean 1.77 years) sum to 5.09 years, which is the mean generation time of the population. The typical early life history pattern of PEI Atlantic Salmon occurs in rivers, with eggs hatching as fry, fry developing into parr, and parr turning into smolts which leave on marine migrations. However, some juvenile males mature precociously, and some parr occupy ponds and estuaries. The ancestral trait of late-run and large returnees is shared by Atlantic Salmon in southeast New Brunswick and northern Nova Scotia. Genetic data on Salmon in stocked rivers suggest an affinity with Salmon in a broad geographic area centred in the southern Gulf of St. Lawrence. However, genetic samples from two small rivers in northeastern PEI clustered with each other but did not show affinities with samples from elsewhere in Canada. Redd counts for the period 1990 - 2019 showed rising trends in four rivers and falling trends in five rivers. Redd counts for the period 2004 - 2019 showed rising trends in 13 rivers and falling trends in six rivers. Seventy-one PEI rivers are large enough that they probably supported Atlantic Salmon populations in pristine times. For 2000 - 2019, juvenile electrofishing and redd surveys detected Atlantic Salmon at least once in 40 rivers, but detected Atlantic Salmon in every monitored year in only 12 rivers. The spawning population of Atlantic Salmon on PEI is estimated at 717, based on redd counts. Sediment deposition on spawning and rearing habitat is a major threat to Atlantic Salmon on PEI. Additional threats include pesticide-related fish kills, water extraction for municipal and irrigation purposes, climate change leading to more frequent droughts and higher water temperatures, fish passage impairment by dams (including beaver Castor canadensis dams), and competition with non-native Rainbow Trout (Oncorhynchus mykiss). [ABSTRACT FROM AUTHOR]

This study examined the status of climate smart aquaculture practices (CSAP) in Ilorin West Local Government Area of Kwara State, Nigeria. About 120 fish farmers were selected for the study. Statistical tools such as frequency count, percentage, mean score, binary logistic regression and Pearson product moment correlation were used to analyse the data. The result revealed that the average age of the respondents was 45 years and 79.2% of them were males. About 65% of them had tertiary education with an average of 6 years’ experience in fish farming. The average annual income of the respondents was about 379. 25 Dollars, and the average household size was 5 persons. The result also showed that about 65% of the respondents used earthen ponds for fishing with an average of 8 fishing ponds per farmer. The most stocked species of fish was catfish (79.2%). Majority (88.3%) of the respondents owned the ponds used and about 90.8 % of them indicated that they farm on the pond all-year-round. About 87.5% of them had high status on the use of climate smart aquaculture practices. The result of binary logistic regression showed that pond type (b=1.350), source of stocked fish (b= 0.850), sources of credit (b= 0.456) and access to extension services (B=1.607) were the determinant factors of the use of CSAP. The study concludes that the main climate smart aquaculture practices used by the fish farmers were stocking of fish, liming of pond, feeding of fish, provision of measures, sorting of fish, water transparency farmers. [ABSTRACT FROM AUTHOR]

Assessment of fish stocks is especially important to avoid overfishing and obtain sustainable fishing policies, and there are many stock assessment methods such as XSA, VPA, BMS, CMSY, and MSVPA to analyze fish stocks. However, these assessment methods require an important amount of data for fish stocks such as diet data, natural mortality, fishing mortality, abundance index of species, predator ratio estimates, and so on. Unfortunately, we do not have such data for most of the fish stocks, and obtaining such data requires an important amount of money and time, but we still can predict important information about fish stocks such as biomass of fish stocks, the maximum sustainable yield, the biomass of fish lost or gained due to predator-prey relations, and even can track the effect of harvesting on predator-prey relations by building a mathematical model for fish populations and implementing a stability analysis. To obtain these outputs, we only need landing data and implement a parameter estimation constrained on stability conditions derived from the stability analysis of the mathematical model. Shortly, this study shows us how important stability analysis is to obtain important information about fish populations in the absence of important data. [ABSTRACT FROM AUTHOR]

As a key link between top‐down regulators and bottom‐up factors, zooplankton responds sensitively to environmental variations and provides information on the ecological state of freshwater systems. Although the response of zooplankton to anthropogenic pressures and fluctuating natural conditions, such as nutrient loading and climate change, has been extensively examined, findings have varied markedly. The mechanistic basis for the correlation between environmental variability and the zooplankton community is still debated, particularly for subtropical eutrophic lakes. We used two methods to analyze physicochemical and selected biological variables derived from long‐term monitoring of Lake Taihu, a subtropical shallow lake in China. We first applied random forest regression to examine how changes in zooplankton were related to a set of environmental variables on interannual time scales. Then we used the results to guide the construction of a conceptual model for piecewise structural equation modeling (pSEM) to quantify more precisely the zooplankton–environment relationship. Zooplanktivorous fish and nutrient concentrations were the most important predictors of long‐term trends in zooplankton in RF regression. Intensification of planktivorous fish predation led to a lower zooplankton biomass and smaller individuals through the removal of larger crustaceans. Moreover, suppression of zooplankton can in part be explained by increases in inedible algae, triggered by a combination of reduced nutrient concentrations and weakened grazer control. These results were also confirmed in the pSEM, which further indicated that top‐down regulators might be more important than bottom‐up factors for the zooplankton community in Lake Taihu. Our results suggest that stocking of filter‐feeding fish in the lake did not meet the expectation that they would control algae, but that the use of biomanipulation measures considering both water quality and fishery management seems promising. This study offers insights into how indicator metrics of zooplankton can improve our understanding of the associations between plankton communities and ecosystem alterations. [ABSTRACT FROM AUTHOR]

Mangrove forests play a critical role in natural disaster resistance and provide meaningful livelihoods for local communities, especially integrated mangrove shrimp farming (IMSF) systems. Organic shrimp certification actually increases the value chains of shrimp farming in addition to ameliorating mangrove--forest management. Identifying technical issues and assessing environmental risks are the leading concerns when considering organic shrimp production certification. In this study, the technical practices of 30 households were investigated, and surface water and sediment samples were collected in the IMSF models and adjacent rivers in the Thua Duc Forest Management Board area, Ben Tre Province. Data collected from shrimp farming ponds and the environmental background were referred to both the Naturland and National Standards. The results showed that the average mangrove forest and shrimp pond ratio was 56.90:42.70 (%). Two technical issues were highlighted: (i) the use of rotenone, known as a toxin to kill undesirable fish before stocking shrimp, and (ii) annual shrimp pond regeneration causing increased pollution. The data showed that higher concentrations of TSS and P-PO4 3- were detected in surrounding rivers, while surface water in either IMSF ponds or adjacent rivers slightly surpassed the permissible levels of total Fe concentration. All parameters--including heavy metals; toxic and persistent parameters; oil and grease and coliforms analysed in surface water, and sediment samples--were lower than the detection and permissible levels. The results provided evidence that the IMSF's practices and environmental characteristics were suitable for recommending the Naturland Standards. Recommendations and technical interventions for farmers are necessary to help reduce Fe levels and the safe use of rotenone in IMSF systems. An environmental quality monitoring programme at the target area should be applied when launching organic shrimp production. [ABSTRACT FROM AUTHOR]

Subtropical lakes are often dominated by benthi-omnivorous fish (e.g., crucian carp) that may substantially disturb sediments and thereby increase water turbidity and nutrient concentrations. Piscivores stocking is sometimes used to control these benthi-omnivores in the expectation that they will reduce their adverse effects on the water quality. However, in shallow subtropical lakes the benthic foraging activities of piscivorous fish may also disturb sediments, a topic that has not yet been well elucidated. Here, we conducted a 6-day mesocosm experiment to explore the bioturbation effects of two native subtropical piscivorous fish (i.e., snakehead, Channa argus and mandarin fish, Siniperca chuatsi) in prey fish (crucian carp, Carassius carassius) present and absent scenarios. Our results showed that in mesocosms without prey, both snakehead and mandarin fish greatly increased the concentrations of suspended solids. However, the concentrations of total, organic and inorganic suspended solids were significantly higher in the mesocosms with snakehead than in those with mandarin fish, suggesting that snakehead has higher bioturbation effects than mandarin fish. When crucian carp were present, we found that both snakehead and mandarin fish significantly reduced prey abundance, whereas piscivore stocking did not significantly decrease the suspended solids and nutrient concentrations. Our study revealed differential effects of two subtropical piscivorous fish species on sediment disturbance and water quality, and we suggest that for lake restoration with piscivores stocking, mandarin fish are a better option than snakehead fish as their predation effect was equal but the strength of sediment disturbance by mandarin fish was lower than that of snakehead. [ABSTRACT FROM AUTHOR]

The North American invasive fish pumpkinseed Lepomis gibbosus has been associated with some detrimental ecological consequences in some parts of its invasive range. Here, we tested the trophic interactions of pumpkinseed with the endemic stream fish Aegean chub Squalius fellowesii ('chub') in a Mediterranean-type water course in SW Anatolia, Turkey, using a bulk stable isotope approach (δ13C, δ15N). Seven sampling sites were able to be grouped as chub in pumpkinseed presence (n = 2) and absence (n = 3), and pumpkinseed in chub absence (n = 2). Across these groups, stable isotope metrics revealed that chub trophic (isotopic) niche size was similar in pumpkinseed presence/absence, but pumpkinseed had a larger niche in chub presence. In sites where they are co-habited, their niches showed some convergence, but with no apparent consequences for their growth or body condition, suggesting there were minimal ecological consequences of this sharing of food resources. These results suggest that the trophic consequences of this riverine invasion of pumpkinseed on this endemic chub was minimal. [ABSTRACT FROM AUTHOR]

Meeting ambitious climate targets will require deploying the full suite of mitigation options, including those that indirectly reduce greenhouse-gas (GHG) emissions. Healthy diets have sustainability co-benefits by directly reducing livestock emissions as well as indirectly reducing land use emissions. Increased crop productivity could indirectly avoid emissions by reducing cropland area. However, there is disagreement on the sustainability of proposed healthy U.S. diets and a lack of clarity on how long-term sustainability benefits may change in response to shifts in the livestock sector. Here, we explore the GHG emissions impacts of seven scenarios that vary U.S. crop yields and healthier diets in the U.S. and overseas. We also examine how impacts vary across assumptions of future ruminant livestock productivity and ruminant stocking density in the U.S. We employ two complementary land use models—the US FABLE Calculator, an agricultural and forestry sector accounting model with high agricultural commodity representation, and GLOBIOM, a spatially explicit partial equilibrium optimization model for global land use systems. Results suggest that healthier U.S. diets that follow the Dietary Guidelines for Americans reduce agricultural and land use greenhouse gas emissions by 25–57% (approx 120–310 MtCO2e/y) and pastureland area by 28–38%. The potential emissions and land sparing benefits of U.S. agricultural productivity growth are modest within the U.S. due to the increasing comparative advantage of U.S. crops. Our findings suggest that healthy U.S. diets can significantly contribute toward meeting U.S. long-term climate goals for the land use sectors. [ABSTRACT FROM AUTHOR]

Stocking of native and non-native fish species is a widespread practice commonly used to enhance inland recreational fisheries, appropriate when intense harvesting and the degradation or lack of suitable habitat decrease the abundance of the managed species below carrying capacity. In spite of its popularity, this practice is often poorly informed by scientific information. Salmonids are arguably the most popular and commercially valuable freshwater fishes being managed for recreational fisheries. Stocking of both native and non-native taxa has been practiced for almost two centuries in Europe, dramatically altering the structure and function of riverine and lacustrine ecosystems. In the Verbano-Cusio Ossola Province, northern Italy, within the Lake Maggiore catchment, we measured large numerical mismatches between stocking of cultured native (Salmo marmoratus) plus non-native trout taxa (S. trutta, S. ghigii, Oncorhynchus mykiss) and the number of fishes captured by local anglers. These observations highlight the need for future studies to estimate the stocking effectiveness of S. marmoratus, a critically endangered species of significant cultural and economic value. [ABSTRACT FROM AUTHOR]

Data from research and commercial use of lumpfish were collected from the research facilities of Gifas (Inndyr, Northern Norway, 67.0° N, 14.0° E). The data were sourced from 12 main lumpfish groups subdivided into 66 subgroups (N = 160,729) delivered to Gifas between 2013 and 2020 and used in cleaner-fish research in (a) land-based facilities, (b) small-scale, or (c) large-scale sea pens. The data were standardised and organised into three main headings. Firstly, background information included transfer time, point of origin, mean starting weight and population size on arrival. Other information included to which site the lumpfish were transferred, volume of cage/tank, whether in the presence of salmon or not, stocking density, days at each site and water quality parameters. Causes of mortality were recorded, when possible, for each group, along with calculated mortality rates, patterns, and analytical information, along with imaging where available. Results show that causes of mortality varied within and between research sites. For lumpfish in hatcheries as well as for those deployed at small-scale sea pens, the primary cause of mortality was identified as pathogenic, while for lumpfish deployed at large-scale sea pens, transporting, grading and mechanical delousing were the primary causes of mortality. The results indicate that more research is required to clarify best practices both in commercial hatcheries and salmon cages and further understanding on lumpfish biological requirements and stress physiology is necessary to develop better methods that safeguard lumpfish welfare and meet their needs. [ABSTRACT FROM AUTHOR]

Gravel pit lakes are common across Europe. These novel ecosystems serve as model systems to study human‐induced and natural colonisation of isolated lakes by fish. Fisheries‐management activities can quickly spread species over large distances, possibly homogenising fish communities across ecosystems, while fostering local fish diversity.Our objective was to evaluate the effects of lake genesis (gravel pit lakes < 100 years old vs. natural lakes of glacial genesis ~10,000 years old) and fisheries management (fish stocking activities present vs. absent) on the fish community in small lakes, while controlling for key environmental variables known to affect lake fish communities.We sampled fish communities by electrofishing and multimesh gillnetting in 47 isolated lakes managed for fisheries, and 19 unmanaged and isolated lakes of both natural and artificial origin in northern Germany. Unmanaged lakes were used as reference to assess fisheries‐management impacts in small natural and artificial lakes.We caught 178,506 fish from 30 species and found that the accumulation of native lake fish species in lakes was associated with fisheries management, which increased local species richness (α‐diversity) and number of predatory species, and reduced among‐lake variation in fish community composition (β‐diversity; i.e., homogenisation). The homogenisation‐effect associated with fisheries happened with introduced native fish species, whereas non‐native species were rarely detected.In unmanaged gravel pit lakes, the littoral fish community composition was substantially different to the communities present in both types of managed lakes and unmanaged natural lakes. Therefore, the relatively young unmanaged gravel pit lakes revealed evidence of ongoing, stochastic colonisation processes that resulted in comparatively species‐poor fish communities.We concluded that fisheries management by anglers speeds up the colonisation of gravel pit lakes with native fish species in the study area. For planning initial fish introductions in newly created gravel pit lakes, it is recommended that fish communities from ecologically similar natural lakes within the same geographical region are used as references to maintain the biotic integrity of newly created fish communities. [ABSTRACT FROM AUTHOR]

Simple Summary: Throughout the Great Lakes basin, infectious diseases likewise threaten wild and hatchery reared fishes, and often require management attention. The lake sturgeon (Acipenser fulvescens) is the only sturgeon species native to the Great Lakes, where it is the largest and longest living fish therein. Due to multiple known and unknown factors, current Great Lakes lake sturgeon populations are estimated to be <1% of historical abundances. One potential contributing factor about which little remains known, especially when compared to other Great Lakes fishes, is the impact of infectious diseases. To address this knowledge gap, a two-year disease surveillance study was undertaken, resulting in the detection and isolation of a herpesvirus from lesions observed on wild adult lake sturgeon in two Great Lakes watersheds (Erie and Huron). Genomic analyses revealed the recovered virus was most similar to, yet molecularly distinct from, a herpesvirus recently recovered from lake sturgeon in the Lake Michigan watershed (Wisconsin, USA). This newly described virus, proposed as Lake Sturgeon Herpesvirus 2, proved virulent to juvenile (<1 year old) lake sturgeon, whereby disease and mortality occurred in virus-exposed fish under laboratory conditions. Overall, results from this study highlight the potential threat this newly described virus poses to Great Lakes lake sturgeon conservation efforts. The lake sturgeon (Acipenser fulvescens; LST) is the only native sturgeon species in the Great Lakes (GL), but due to multiple factors, their current populations are estimated to be <1% of historical abundances. Little is known about infectious diseases affecting GL-LST in hatchery and wild settings. Therefore, a two-year disease surveillance study was undertaken, resulting in the detection and first in vitro isolation of a herpesvirus from grossly apparent cutaneous lesions in wild adult LST inhabiting two GL watersheds (Erie and Huron). Histological and ultrastructural examination of lesions revealed proliferative epidermitis associated with herpesvirus-like virions. A virus with identical ultrastructural characteristics was recovered from cells inoculated with lesion tissues. Partial DNA polymerase gene sequencing placed the virus within the Family Alloherpesviridae, with high similarity to a lake sturgeon herpesvirus (LSHV) from Wisconsin, USA. Genomic comparisons revealed ~84% Average Nucleotide Identity between the two isolates, leading to the proposed classification of LSHV-1 (Wisconsin) and LSHV-2 (Michigan) for the two viruses. When naïve juvenile LST were immersion-exposed to LSHV-2, severe disease and ~33% mortality occurred, with virus re-isolated from representative skin lesions, fulfilling Rivers' postulates. Results collectively show LSHV-2 is associated with epithelial changes in wild adult LST, disease and mortality in juvenile LST, and is a potential threat to GL-LST conservation. [ABSTRACT FROM AUTHOR]

High‐density fingerling rearing of pengba was conducted for 90 days in biofloc system (BFS) to study the effect of stocking density on growth, feed utilization, water quality, water use efficiency and health of animals. The study was conducted in 12 continuously aerated tanks (50 m3), grouped into four treatments T‐1, T‐2, T‐3 and T‐4, which were stocked with pengba fry (1.25 ± 0.05 g, 4.74 ± 0.70 cm) at 50, 60, 70 and 80 m−3, respectively. Supplementary feed (1 mm floating pellet) was fed twice daily, each time for 30 min duration. Molasses and urea were supplemented to maintain suitable C:N ratio at 15:1. No water exchange was given, except monthly compensation of evaporation loss. While water quality and most of the growth attributes in T‐1 and T‐2 remained similar, T‐3 at 70 m−3 density showed better water quality, higher survival and growth than T‐4. Body composition remained consistent across treatments despite impaired feed digestion and utilization associated with higher densities. The non‐specific immune responses in fingerlings increased from T‐1 to T‐3, but further density rise showed compromised immune in T‐4. Such results suggested 70 m−3 to be an ideal density for production of healthier fingerlings. But T‐4 produced 13.5% more fingerlings than T‐3, and fingerlings (7.56 ± 0.50 cm; 5.43 ± 0.09 g) were within acceptable size range for grow‐out stocking. T‐4 also showed the lowest total water use and the highest water implicating 80 fry m−3 to have more applicability. Thus, the study recommends 70–80 m−3 as ideal range for fingerling rearing of pengba in BFS. [ABSTRACT FROM AUTHOR]

Common carp is one of the most important game fish in Europe. Due to the high exploitation and limited natural recruitment, direct stockings became a common and widespread stock enhancement practice in recreational fisheries. Sustainable recreational fisheries management requires continuous monitoring programs to define the stocking size and distribution of newly-stocked fish. In this study, we assess the capture rate and distribution patterns of hatchery-reared common carps in a dammed, lotic ecosystem using data from a seven-year tagging survey. Mean capture rate was 7.4% and onethird of captures happened within the first two months after release. High interannual differences were observed both in the capture rate and the temporal dynamics of captures. Movement patterns also showed interannual and interindividual differences; 30.8% of the fish were captured within 5 km of their release site, and 55.6% of the fish were captured within 10 km. More than ten per cent (12.8%) of fish caught more than 25 km far from release site. Distance travelled did not associate consistently with time between the release and capture. Our findings suggest that repeated surveys in consecutive years would be preferable than increasing the number of tagged fish in one year in angler report-based tagging surveys, and that 15-20 kms between stocking sites can ensure proper distribution of common carp in a lotic fishery even under high angling pressure. [ABSTRACT FROM AUTHOR]

The Length-weight relationships (LWRs) are very important to data for accurate estimate of populations in stock menagement. In this study, the length-weight relationships and Fulton's condition factor (K) of some fish in Göynük Stream, Murat River (Bingöl/Turkiye) were examined. The LWRs and condition factor (K) of Cyprinon macrostomus, Garra rufa, Barbus lacerta, and Acanthobrama marmid were analyzed between March 2017-February 2019. LWRs was estimated using the linear regression model. LWRs were obtained as total weight (TW) = 0.013L2.98, 0.057L2.40, 0.016L2.79 and 0.029L2.82 for C. macrostomus, G. rufa, B. lacerta and A.marmid, respectively. The b values acquired in the four fish species ranged from 2.13-2.57 (G. rufa-Male; Female) to 2.77-3.34 (B. lacerta-Female; Male). Only B. lacerta males had a positive allometric growth versus the males and females of all species had a negative allometric growth. The K of the fish species varied from 0.90-0.99 (A. marmid-Male; Female) to 1.27 (G. rufa-All), indicating that most of the fish were in good condition. However, C. macrostomus and G. rufa were better condition than B. lacerta and A. marmid. The study has provided baseline information on the LWR and K of the fish species in Göynük Stream. The data that would be useful to adapt the adequate regulations for sustainable fish stock estimation in the stream for fishery biologist. [ABSTRACT FROM AUTHOR]

All‐female stocks of giant freshwater prawn, Macrobrachium rosenbergii, hold immense potential for aquaculture but early sexual maturity might still be a constraint in all‐female prawn farming. The growth performance and gonadal maturation of all‐female M. rosenbergii reared in 1,000 L tanks for 60‐days were tested at five stocking densities of 4 (T1), 8 (T2), 16 (T3), 24 (T4), and 32 (T5) prawns/m2 in triplicates. The mean initial weights (±SD) of prawns were 5.20 ± 0.42 g (T1), 5.10 ± 0.48 g (T2), 5.18 ± 0.54 g (T3), 4.87 ± 0.92 g (T4), and 5.05 ± 1.09 g (T5), respectively. The survival rate (83.3%), mean final weight (24.93 g), daily weight gain (0.33 g), and specific growth rate (2.61) were the highest in T1, while the most efficient feed conversion ratio (1.57) was in T2. The prawn yields were higher at higher stocking densities (T3 to T5). The stocking density of 8 prawns/m2 is feasible for good growth performance, while the estimated density for optimum yield was 23.5 prawns/m2, indicating that all‐female prawns are amenable to intensive farming. The presence of virgin females ranged from 30% in T1 to 14% in T5, but the distribution of ovarian stages was not significantly different among the stocking densities tested. The gonadosomatic index values showed no significant difference among the treatments. The results indicated that while the stocking density significantly affected growth parameters, it had no significant effect on the all‐female prawns' gonadal maturation. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) may be a promising alternative for production of juvenile matrinxã (Brycon amazonicus) as it allows greater fish productivity compared to ponds and is considered an economic and environmentally sustainable system. This study evaluated the effects of different stocking densities on water quality, survival, blood parameters and growth performance of juvenile matrinxã in the biofloc system. Juveniles of 5.89 ± 0.11 g were randomly distributed in five stocking densities (50, 140, 230, 320 and 410 fish ∙ m−3), in triplicate, in a BFT system. Extruded commercial feed (36% crude protein) was offered until apparent satiety four times per day for 61 days. In general, the increase in stocking density resulted in a reduction in dissolved oxygen, pH and alkalinity. Although nitrogenous compounds, total suspended solids, settleable solids and turbidity were greater in higher stocking densities, the water quality parameters were within the recommended range for matrinxã in all treatments. The stocking density had a quadratic effect on the variables specific growth rate, daily weight gain and mean final body weight. For the final stocking density and feed conversion ratio, the effect of stocking density was positive and linear. Survival rates were over 90% at stocking densities >230 fish ∙ m−3. We found a lower concentration of erythrocytes in juvenile matrinxã at the lowest stocking density (50 fish ∙ m−3) and the lymphocyte concentration was higher in the fish kept at 140 fish ∙ m−3 compared to those kept at 410 fish ∙ m−3; however, there was no difference among the other treatments. In conclusion, juvenile matrinxã can be efficiently produced using BFT at stocking densities of 291–293 fish ∙ m−3 or 13.50–13.60 kg ∙ m−3. Although the increase in stocking density is favorable for increasing the biomass and survival of matrinxã, an intensive management of solids and nitrate, as well as alkalinity corrections, are necessary to ensure proper functioning of the production and to avoid mortality of fish due inadequate water quality. • The increase in stocking density contributes to biomass increment of matrinxãs. • Stocking density had a positive and high correlation with survival rate. • Biofloc system is an alternative to reduce aggressiveness in matrinxã juveniles. • Stocking densities of 13.5–13.6 kg m−3 are suggested for matrinxã juveniles in BFT. • Survival rate was above 90% at stocking densities above 230 fish m−3. [ABSTRACT FROM AUTHOR]

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]

In recent years, the rapid development of the large-scale aquaculture industry has generated substantial economic benefits, positioning it as one of the fastest-growing sectors in global agricultural production. However, improper management practices in aquaculture, including overfeeding, improper feed selection, antibiotic misuse, high stocking densities, inappropriate choice of aquaculture species, and improper discharge of aquaculture wastewater, have resulted in significant watershed pollution in agriculture and the wastage of valuable resources. To address these challenges, extensive research and application of wastewater treatment technologies have been conducted in large-scale aquaculture in China. This review provides an overview of current cases and applications of wastewater treatment in large-scale aquaculture in China, focusing on four common intensive wastewater treatment methods: constructed wetland treatment model, ecological ditch treatment model, Integrated Multi-trophic Aquaculture model, and recirculating aquaculture model. The constructed wetlands utilize plants and microorganisms to purify both organic and inorganic pollutants in water, while ecological ditches employ engineering measures such as sedimentation ponds, interception ditches, and aeration devices to achieve wastewater treatment. Additionally, other aquaculture models are highlighted, such as Integrated Multitrophic Aquaculture (IMTA), which emphasizes synergistic interactions between aquaculture species and the recycling of nutrients, and the Recirculating Aquaculture Systems (RAS), which utilize water circulation and treatment equipment for wastewater treatment. The consequences and benefits of these systems in pollution reduction are described. These treatment technologies have made significant progress, offering theoretical guidance for environmentally friendly aquaculture production and the maintenance of ecological stability in aquaculture water bodies. Each wastewater treatment model has a different function, target, and methodology. Finally, this paper proposes directions and recommendations for future pollution management in large-scale aquaculture in China, including strengthening technological research and development, the combined application of multiple treatment models, promoting industry collaboration, and achieving resource sharing. These efforts will contribute to further promoting the sustainable development of China's aquaculture industry and provide valuable experiences and references for other countries and regions. • CWs and ecological ditch use plants and microorganisms to purify wastewater. • IMTA maximizes species interactions for efficient nutrient cycling. • RAS uses equipment to remove pollutants from aquaculture water for recirculation. • Utilizing multiple purification modes can enhance wastewater treatment efficiency. [ABSTRACT FROM AUTHOR]

Probiotics in the biofloc technology (BFT) system improve fish growth and immune response and promote a favorable intestinal microbiota balance. This study aimed to investigate the growth, hemato-biochemical parameters, bacterial resistance, and the number of intestinal bacteria colonies of Nile tilapia (6.23 g) reared in the BFT system with graded levels of Bacillus subtilis multiplicate (BSM) in the water. The multiplication of these microorganisms was performed in a biofactory. Fish were distributed into four different groups with graded BSM concentrations in the water of 0.00, 0.25, 0.50, and 0.75% (or 0; 750; 1500; and 2250 mL; called BSM0 (control), BSM25, BSM50, and BSM75, respectively). The experimental procedure had 45 days for growth performance evaluations and seven additional days of bacterial challenge with Aeromonas hydrophila. The experimental design was randomized into four treatments in triplicate (n = 20 fish per tank; initial stocking density of 0.50 kg m−3). Survival was 100% before and after the bacterial challenge. Increasing BSM in the BFT system had a positive linear effect on nitrite, nitrate, settled solids, hemoglobin, and hematimetric indices. BSM50 showed the highest specific growth rate, weight gain, intestinal total bacteria, and B. subtilis counts and the lowest feed conversion rate. In BSM50 and BSM75, liver glycogen levels and aspartate aminotransferase (AST) activity were higher and lower, respectively, than in the other treatments. Plasma total cholesterol, total proteins, albumin, and skin mucus total proteins and albumin were highest in BSM25. After the bacterial challenge, the number of lesions was lower in BSM75 than in the control group. In conclusion, we recommended BSM50 because it increased the growth performance and bacterial colonization in the intestine. It also decreased liver AST activity in Nile tilapia reared in the BFT system without compromising water quality and hematological and plasmatic parameters. • BFT system is a suitable alternative for Nile tilapia production. • The Bacillus subtilis multiplicate (BSM) was produced through a biofactory. • Increasing BSM in the water increased nitrite, nitrate, and settled solids. • The growth performance was improved with BSM at 0.50%. • Lesions caused by Aeromonas hydrophila decreased with BSM at 0.75%. [ABSTRACT FROM AUTHOR]

Traditional Chinese medicines (TCMs) with anti-pathogenic properties have been increasingly utilized in animal husbandry as substitutes for antibiotics. However, lingering uncertainties persist regarding the mobility, bacterial hosts, and potential human hazards associated with antibiotic resistance genes (ARGs) in animal husbandry when TCMs are introduced. In this study, cecal digesta from Wuding chickens subjected to varying stocking densities (moderate and high) and treated with different TCMs (dihydroartemisinin, berberine hydrochloride, and oligomeric proanthocyanidins) were collected and subjected to metagenomics-based analysis. A total of 280 ARG subtypes were identified, with multidrug and aminoglycoside resistance genes being the most diverse and abundant. The primary antibiotic resistance bacteria identified belonged to the phyla of Firmicutes (38.68%), Bacteroidetes (22.74%), and Proteobacteria (12.71%); however, some pathogenic antibiotic-resistant bacteria (PARB) were also identified across different samples. Surprisingly, high stocking density was not observed to propagate ARGs, which could be due to the restricted usage of antibiotics. Furthermore, higher proportions of mobile genetic elements and some multidrug-resistant PARB (∼4 times) were observed in high-stocking-density chickens fed berberine hydrochloride than in high-stocking-density chickens fed other TCMs, which could facilitate the horizontal gene transfer (HGT) of ARGs and pose potential human health risks. In contrast, dihydroartemisinin reduced the total abundance of ARGs and the resistome risks to human health (∼10% decrease compared to control). Moreover, rank I ARGs with higher human health risk and the risk index based on ARG risk also ranked lowest (p < 0.05) in high-stocking-density chickens fed dihydroartemisinin. The reduction effect of dihydroartemisinin was achieved by regulating the cecal microbiome of broilers and inhibiting HGT (reducing the contribution from 17.7% to 4.0%). This study provides metagenomic evidence of the development of ARGs in broiler breeding environments. The findings highlight the distinct characteristics of TCMs as feed additives on regulating the antibiotic resistome during broiler farming and demonstrate dihydroartemisinin as an effective additive complying with the environmental safety. [Display omitted] • Effects of three Chinese medicines on antibiotic resistome of broilers were compared. • High stocking density did not obviously affect on antibiotic resistome of broilers. • Berberine hydrochloride addition enriched the multidrug-resistant pathogens. • Dihydroartemisinin reduced the antibiotic resistome risk of broilers to human health. • This reduction achieved by regulating cecal microbiome and inhibiting gene transfer. [ABSTRACT FROM AUTHOR]

Background: High stocking density (HSD) stress has detrimental effects on growth performance, intestinal barrier function, and intestinal microbiota in intensive animal production. Organic acids (OA) are widely used as feed additives for their ability to improve growth performance and intestinal health in poultry. However, whether dietary OA can ameliorate HSD stress-induced impaired intestinal barrier in broilers remains elusive. In this study, a total of 528 one-day-old male Arbor Acres broilers were randomly allocated into 3 treatments with 12 replicates per treatment including 10 birds for normal stocking density and 17 birds for HSD. The dietary treatments were as follows: 1) Normal stocking density + basal diet; 2) HSD + basal diets; 3) HSD + OA. Results: HSD stress can induce increased levels of serum corticosterone, lipopolysaccharides, interleukin-1β, tumor necrosis factor-α, and down-regulated mRNA expression of ZO-1, resulting in compromised growth performance of broilers (P < 0.05). Dietary OA could significantly reduce levels of serum corticosterone, lipopolysaccharides, interleukin-1β, and tumor necrosis factor-α, which were accompanied by up-regulated interleukin-10, mRNA expression of ZO-1, and growth performance (P < 0.05). Moreover, OA could down-regulate the mRNA expression of TLR4 and MyD88 to inhibit the NF-κB signaling pathway (P < 0.05). Additionally, HSD stress significantly decreased the abundance of Bacteroidetes and disturbed the balance of microbial ecosystems, whereas OA significantly increased the abundance of Bacteroidetes and restored the disordered gut microbiota by reducing competitive and exploitative interactions in microbial communities (P < 0.05). Meanwhile, OA significantly increased the content of acetic and butyric acids, which showed significant correlations with intestinal inflammation indicators (P < 0.05). Conclusions: Dietary OA ameliorated intestinal inflammation and growth performance of broilers through restoring the disordered gut microbial compositions and interactions induced by HSD and elevating short-chain fatty acid production to inhibit the TLR4/NF-κB signaling pathway. These findings demonstrated the critical role of intestinal microbiota in mediating the HSD-induced inflammatory responses, contributing to exploring nutritional strategies to alleviate HSD-induced stress in animals. [ABSTRACT FROM AUTHOR]

A 16‐week experiment was conducted to assess whether dietary supplementation with Digestarom® as a phytogenic feed additive could reverse the negative influences of high stocking density in Nile tilapia (Oreochromis niloticus). For this purpose, 240 fish (2.4 ± 0.1 g) were divided into six groups. Two groups (D1 and D2) were fed a basal diet and reared under different stocking densities of 125 and 250 fish per m3. The other fish groups (D3, D4, D5 and D6) were raised under a high stocking density of 250 fish per m3 and fed supplemented diets with Digestarom® P.E.P. MGE at levels 50, 100, 200 and 300 mg per kg diet respectively. Growth retardation and impaired feed efficiency resulting from rearing fish at high stocking density were improved in groups fed diets fortified with 200 and 300 mg Digestarom® per kg diet. Moreover, rearing fish at a density of 250 fish per m3 significantly reduced Hb, RBCs, MCV and total protein but increased WBC, MCHC creatinine, urea‐N, ALT and AST. On the contrary, enriched tilapia diets with 200 or 300 mg Digestarom® per kg diet significantly corrected the earlier altered haematological indices and serum biochemical indicators. Furthermore, the addition of 300 mg Digestarom® to the diets of tilapia reared at high stocking density significantly modulated lipid deposition and ash level in their flesh. Conclusively, supplementing the Nile tilapia diet with 300 mg Digestarom® per kg feed could be a promising supplement for combating the negative impacts of high stocking density. [ABSTRACT FROM AUTHOR]