Does Fish Conditioning in Aquaculture Increase Survival Success in the Wild? A Case Study on a Cyprinid Fish

Many endangered fish species in the wild are artificially bred, and their populations are strengthened by the stocking of aquaculture-raised juveniles. Because fish from aquaculture are generally not well prepared for the challenging life in the wild, we tested whether training for selected challenges could improve fish survival after stocking. We chose conditioning on predation pressure (by learning predator image of northern pike Esox lucius using predator chemical cues and visual stimuli), increased rearing water velocity 20 cm × s−1, and direct exposure to predation. The juvenile cyprinid fish asp (Leuciscus aspius) was used as a model prey species. A total of 7949 asp were reared in four groups using a combination of high flow, predation, and control treatments (low flow, no predation; 2018, 2149, 1929, and 1856 individuals, respectively). Of these, 1800 individuals were released into three ponds with pike, and their mortality rates were monitored in relation to predation for two months after stocking using passive telemetry arrays. The remaining 6149 aquaculture-reared individuals were released directly into a large reservoir, while 1426 individuals that survived pike predation for two months were released after the pond experiment ended. Fish survival in a reservoir was monitored in 2020 and 2021 by boat electrofishing and passive telemetry. The effect of training in aquaculture was not detected in pond conditions, but the fish that survived direct predation from pike for two months in the semi-natural treatment were more likely to survive in the wild than their aquaculture-reared counterparts. In the laboratory environment, asp responded to predator chemical cues with an increase in shoal cohesion and swimming activity, which demonstrate their ability to detect chemical cues. However, exposure to more fluvial conditions did not result in increased critical swimming speed. The study suggests that conditioning tested in aquaculture may not be sufficient to prepare fish for the wild, while exposing fish to direct predation could increase fish survival.

The effect of liquid organic plant supplements on aquaponic culture of red cabbage (Brassica oleraceae L. var. Capitata f. rubra DC.) and tilapia (Oreochromis niloticus L.)

Abstrak. Aquaponic cultivation is an innovation in the fulfillment of fish and vegetable food needs. The types of fish and vegetables that have not been widely cultivated in aquaponics are tilapia and red cabbage. The aims of this experiment is to provides information on the best concentration of plant liquid organic suplements for the maintenance of red cabbage and tilapia in this aquaponic system. These are commodity have a variety of advantages and high production so it is necessary to conduct an aquaponic assessment of tilapia and red cabbage using liquid organic supplements of plants. This research was conducted gradually, namely the preparation of red cabbage seeds and fish seeds, fermentation of water, acclimatition of fish and research treatment. The research design uses a completely randomized design with four treatments and five replays. The treatment used by giving of liquid organic supplement concentrations merk SOC plants that differ in the integrated aquaponic tarpaulin pond system is treatment1 (0 ml/l), treatment2 (2.5 ml/l), treatment3 (5 ml/l) and treatment4 (7.5 ml/l) with each pond as much as 25 fish/pond. Aquaponic watering technique using DFT (Deep Flow Technique). Variables of red cabbage include the morphometry of the red cabbage plant (height of the plant, number of leaves, and wet weight). Tilapia variables include relative growth rate and fish survival rate. The results showed that the treatment of the concentration of liquid organic supplements of plants had a noticeable effect on the height of the plant, the number of leaves and the wet weight. Data of tilapia research with aquaponic system using tepal ponds include the relative growth rate of tilapia ranging from 2.84 - 3.90%/day and tilapia survival ranges from 88-92%.

Innovative Projects and Technology Implementation in the Hydropower Sector

In this chapter, some innovative case studies in the hydropower sector are discussed, highlighting how novel technologies and operational practices can make it more efficient, sustainable and cost-effective. Some practices to reduce hydropeaking effects, improving fish habitat, and turbines with higher survival rate, allowing to bring fish survival >98%, are discussed. The retrofitting of non-powered barriers can help to minimize the environmental impacts, reducing costs by more than 20%. New turbines are described focusing on their advantages with respect to standard ones, in particular, water wheels in irrigation canals to promote the valorization of watermills and old weirs, the very low head (VLH) turbine in navigation locks (reducing overall cost by more than 20%), the vortex turbine, and the Deriaz turbine with adjustable runner blades to improve the efficiency curve, especially at part load. Digitalization can help in preventing damages and failures increasing the overall efficiency and energy generation by more than 1%.

Performance Of Nile Tilapia Oreochromisniloticus (L) In Cages of Varied Stocking Densities

Cage culture is a new venture in Tanzania, and the knowledge of stocking density in cages is still needed. Growth performance of Nile tilapia, Oreochromis niloticus (L) stocked in cages of varied stocking densities and their impacts on waters were evaluated for 212 days in Shirati Bay of Lake Victoria. We started with fingerlings of 18.0±2.1 g, 19.9±14.7 g, and 18.5 ± 8.0 g mean weights. They were raised in cages at stocking densities of 70 (Treatment I), 100 (Treatment II), and 130 fish/ m3 (Treatment III) each in triplicates. We recorded monthly fish weights and lengths, total nitrogen, total phosphorus, ammonia, and micro-benthos. Parameter such as dissolved oxygen, pH, temperature, and transparency were all monitored weekly. The final average fish weights were 374.1±59.8g in treatment I, (194.8 ± 63.7g) in II, and (273.2±20.6g) in III. Percentage fish survival was the highest in treatment I (76.7%), followed by II (65.4%) and III (54.3%). Specific growth rate, production and yield was the highest in treatment I, and significantly different from treatments II and III (p <0.05). This indicates that Nile tilapia flourished well in the lowest stocking density. Water quality parameters were within the range of fish culture throughout the study and observation of water depth, distance from the shoreline, and the prevailing water currents showed lack of adverse environmental effect caused by fish cage culturing

Post-release survival and prolonged sublethal effects of capture and barotrauma on deep-dwelling rockfishes (genus Sebastes): implications for fish management and conservation

Barotrauma—injury induced by changes in pressure—is a widespread challenge for successfully releasing fishes following capture. We used acoustic telemetry to examine the long-term post-release survival and behaviour of four rockfish species (genus Sebastes) suffering from barotrauma following capture using recreational fishing techniques. We placed particular emphasis on examining Cowcod (Sebastes levis) and Bocaccio (Sebastes paucispinis), two historically overfished species along the United States West Coast that serve as good model species representing different ecological lifestyles. We show that fish survival was species specific and that 40% of observed mortality occurred more than 48 h post release—a typical time period used in many short-term survivorship studies. Cowcod survival was correlated with fish length, sea surface temperature, and dissolved oxygen concentration at the mean depth of capture. Generalized additive mixed models of Cowcod and Bocaccio behaviour showed that surviving individuals were negatively affected by capture and barotrauma for at least 30 d post-release. Our findings demonstrate the need for extended observations to accurately quantify the mortality of fishes suffering from barotrauma and show how such data can be successfully implemented into fisheries management through engagement between managers, scientists, and the fishing community.

Evaluation of nutritional compositions and haematological effect of locally produced fish feeds in Heterobranchus Bidorsalis (catfish) Fingerings

Background: The Insufficient feed availability in the natural or artificial environment of fish has resulted in their competition for survival. This has also brought about their poor yields and population depletion in their environment. Thus, supplementation of fish feed with cheap locally produced diets containing the essential nutrients needed for fish survival and growth is a necessity. In the present study, we evaluated the nutritional compositions and haematological effect of locally produced fish feed on Heterobranchus Bidorsalis (Catfish) fingerlings. Methods: Pearson’s square method was used to formulate three diets A, B and C using different fractions of local ingredients. A commercial feed (Coppens) was used as a control diet. The feeds were evaluated for proximate, minerals, and amino acid compositions. Forty fingerlings of 2 g body weight were divided into 4 groups consisting of ten fingerlings each. Groups A-C were fed the formulated diets while group D was fed with the commercial feed. Each group was fed 5 % of their average body weight twice daily in an aquarium for 49 days. Results: The results revealed a significant increase (p<0.05) in protein (44.12±0.15 %), amino acids and minerals contents of diet A than other formulated diets (B and C) but lower than the control diet. The results of haematological parameters showed that fingerlings fed formulated diet A was significantly higher in values for RBC, haemoglobin and PCV but lower in WBC contents than the groups fed formulated diets B and C. Conclusion: Formulated diet A yielded a better result in terms of protein content, and haematological status of the catfish. Therefore, formulated diet A is the most preferably alternative for catfish fingerlings rearing

Applying Artificial Intelligence (AI) Techniques to Implement a Practical Smart Cage Aquaculture Management System

Purpose This paper presents our team’s results to establish an AIoT smart cage culture management system. Methods According to the built system, the farmed field information is transmitted to the data platform of Ocean Cloud, and all collected data and analysis results can be applied to the cage culture field after the bigdata analysis. Results This management system successfully integrates AI and IoT technologies and is applied in cage culture. Using underwater biological analysis images and AI feeding as examples, this paper explains how the system integrates AI and IoT into a feasible framework that can constantly acquire information about the health status of fish, survival rate of fish, as well as the feed residuals. Conclusion The results of our research enable the aquaculture operators or owners to efficiently reduce the feed residual, monitor the growth of fish, and increase fish survival rate, thereby increasing the feed conversion rate.

An Evaluation of Fish Tissue Monitoring Alternatives for Mercury and Selenium: Fish Muscle Biopsy Samples Versus Homogenized Whole Fillets

Fish contaminant studies with human health protection objectives typically focus on muscle tissue, recognizing that fillets are the commonly consumed tissue fraction. Muscle biopsy punch sampling for mercury analysis has recently been used as an alternative to harvesting fish for fillets; however, there is limited information comparing fillet plug results to whole fillet results. This study was conducted to address that data gap and to test the applicability of plugs for monitoring associated with United States Environmental Protection Agency’s fish tissue-based mercury and selenium water quality criteria. The mercury phase included 300 fillet homogenates and 300 field-extracted plug samples from 60 fish, and the selenium phase included 120 fillet homogenates and 120 plugs from 30 fish. Both phases showed that there were no statistically significant differences between fillet plug and homogenized fillet results at the community level; however, a selenium plug monitoring alternative must employ a sufficiently sensitive analytical method and consider total solids. Plug and fillet sampling alternatives have inherent advantages and disadvantages. Fillet sampling provides sufficient mass to consider multiple contaminants but requires fish to be harvested. Plug sampling only provides adequate mass for a single analyte but may allow fish survival, although additional research is needed on survival following plug removal.

Integration of Satellite Image Derived Temperature and Water Depth for Assessing Fish Habitability in Dam Controlled Flood Plain Wetland

The present study attempted to investigate the changes in temperature conducive to fish habitability during the summer months in a hydrologically modified wetland following damming over a river. Satellite image-driven temperature and depth data calibrated with field data were used to analyse fish habitability and the presence of thermally optimum habitable zones in some fishes such as Labeo Rohita, Cirrhinus mrigala, Tilapia fish, Small shrimp, and Cat fishes. The study was conducted both at the water's surface and at the optimum depth of survival. It is very obvious from the analysis that a larger part of wetland has become an area that destroyed aquatic habitat during the post-dam period and existing wetlands have suffered significant shallowing of water depth. This has resulted in a shrinking of the thermally optimum area of fish survival in relation to surface water temperature (from 100.09 km2 to 74.24 km2 before the dam to 93.97 km2 to 0 km2 after the dam) and an improvement in the optimum habitable condition in the comfortable depth niche of survival. In the post-dam period, it increased from 75.49 % to 99.765%. Since the damming effect causes a 30.53 to 100% depletion of the optimum depth niche, improving the thermal environment has no effect on fish habitability. More water must be released from dams for restoration. Image-driven depth and temperature data calibrated with field information has been successfully applied in data sparse conditions, and it is further recommended in future work.