Unwanted Fish Research Articles

Waste to wealth- a transformative perspective in greening the environment with a focus on fisheries and aquaculture: emerging cutting edge trends

This article explores the growing potential of the waste-to-wealth approach in the fisheries and aquaculture sectors. It argues that by viewing waste as a resource, these sectors can achieve significant environmental and economic benefits. The editorial highlights the concerning volume of waste generated in fisheries and aquaculture, including unwanted fish, aquaculture waste, and plastic pollution. It then discusses the potential of waste-to-wealth solutions, such as fish waste valorization, aquaculture wastewater treatment, and plastic pollution reduction. The editorial emphasizes the crucial role of environmental biology in driving this revolution by providing expertise in ecosystem understanding, waste management optimization, sustainable resource management, and monitoring and evaluation. Finally, it highlights the future direction of environmental biology in this context, focusing on innovative technology development, long-term ecological understanding, and stakeholder collaboration.. KEYWORDS :Circular economy,Fish waste valorization,Plastic pollution reduction,Sustainable resource management,Waste management,Waste-to-wealth

Movement and behavioral states of common carp (Cyprinus carpio) in response to a behavioral deterrent in a navigational lock

BackgroundFreshwater ecosystems are some of the most affected by biological invasions due, in part, to the introduction of invasive carp worldwide. Where carp have become established, management programs often seek to limit further range expansion into new areas by reducing their movement through interconnected rivers and waterways. Lock and dams are important locations for non-physical deterrents, such as carbon dioxide (CO2), to reduce unwanted fish passage without disrupting human use. The purpose of this study was to evaluate the behavioral responses of common carp (Cyprinus carpio) to non-physical deterrents within a navigation structure on the Fox River, Wisconsin. Acoustic telemetry combined with hidden Markov models (HMMs) was used to analyze variation in carp responses to treatments. Outcomes may inform CO2 effectiveness at preventing invasive carp movement through movement pinch-points.MethodsCarbon dioxide (CO2) was recently registered as a pesticide in the United States for use as a deterrent to invasive carp movement. As a part of a multi-component study to test a large-scale CO2 delivery system within a navigation lock, we characterized the influence of elevated CO2 and forced water circulation in the lock chamber on carp movements and behavior. Through time-to-event analyses, we described the responses of acoustic-tagged carp to experimental treatments including (1) CO2 injection in water with forced water circulation, (2) forced water circulation without CO2 and (3) no forced water circulation or CO2. We then used hidden Markov models (HMMs) to define fine-scale carp movement and evaluate the relationships between carp behavioral states and CO2 concentration, forced water circulation, and temperature.ResultsForced water circulation with and without CO2 injection were effective at expelling carp from the lock chamber relative to null treatments where no stimulus was applied. A portion of carp exposed to forced water circulation with CO2 transitioned from an exploratory to an encamped behavioral state with shorter step-lengths and a unimodal distribution in turning angles, resulting in some carp remaining in the lock chamber. Whereas carp exposed to forced water circulation only remained primarily in an exploratory behavioral state, resulting in all carp exiting the lock chamber.ConclusionOur findings illustrate the potential of forced water circulation, alone, as a non-physical deterrent and the efficacy of CO2 injection with forced water circulation in expelling carp from a navigation lock. Results demonstrate how acoustic telemetry and HMMs in an experimental context can describe fish behavior and inform management strategies.

Acute Toxicity Effect of Crude Leaves Extract of Thevetia peruviana on Full Blood Count and some Organs of Clarias gariepinus Juveniles

Background: Many toxicity studies have shown that heamatological and histological alterations are widely used as good bioindicators in determining the effect of toxicants on fish. This study investigated the acute toxicity effects of the leaf extract of Thevetia peruviana on full blood count parameters and some organs of Clarias gariepinus juveniles”. Methods: One hundred and twenty C. gariepinus mixed sex juveniles were exposed to acute con-centrations (0.63, 1.25, 2.50, 5.00, and 10.00g/L ) of leave extract of T. peruviana in twelve 20 L capacity rectangular glass tanks with six treatments and bi-replicated. Blood for full blood count was collected through cardiac puncture while gills and liver were excised and analyzed for histo-pathological alterations. Results: PCV, RBC, Hb, Neu, and Lym of C. gariepinus juveniles inversely decreased while WBC directly increased with acute concentrations of T. peruviana leaves extract. The microscopic examination of the gills revealed concentration-dependent histo-architectural alterations expressed as epical clubbing, haemorrhage, desquamation, atrophy, and complete erosion of secondary lamel-lae. The liver showed moderate to severe concentration-dependent histopathological lesions typi-fied by hypertrophy, atrophy, necrosis, kupffer cell proliferation, and hepatocellular degenerations. Conclusion: Given the alterations in the blood, gills and liver noted in this study, the invasive growth of the T. peruviana plant should be controlled to minimize unwanted fish kill.

Changes in catch efficiency and selectivity in the beam trawl fishery for sole when mechanical stimulation is replaced by electrical stimulation

Beam trawl fisheries for sole are characterised by large amounts of unwanted bycatch (i.e. discards) consisting of fish below the Minimum Conservation Reference Size, unwanted fish due to low commercial value or lack of quota, and benthic invertebrates. In order to reduce the quantity of discards, a substantial part of the Dutch beam trawl fleet was allowed to replace the conventional tickler chain beam trawl (BT) with the pulse trawl (PT) on an experimental basis. The PT used electrical stimulation to immobilise and capture fish. Here we study whether pulse trawling reduced the amount of discards by comparing catch rates of landings and discards of BT and PT in the period 2009–2018 for a wide range of species. The PT caught (kg.km-2) significantly more marketable sized sole (Solea solea, 48 %), turbot (Psetta maxima, 8 %), brill (Scophthalmus rhombus, 28 %) and whiting (Merlangius merlangus, 95 %), and significantly less marketable sized plaice (Pleuronectes platessa, −16 %), cod (Gadus morhua, −32 %) and gurnards (−12 %). No significant difference was found for dab (Limanda limanda), gadoids, or rays and sharks. Among discards, the PT caught more undersized sole (27 %) and whiting (42 %) but less undersized plaice (−21 %), dab (−19 %) and grey gurnard (Eutrigla gurnardus, −31 %). The observed differences in species selectivity are discussed in relation to the response of fish to bottom trawl gear and the effects of pulse stimulation. For the benthic invertebrates Ophiuroidae, bivalves and crabs the PT caught fewer individuals (between −38 % and −57 %). No significant difference was observed in sea urchins and sea stars. Overall, this study shows that the transition from the BT to PT resulted in a 36 % decrease (95 % prediction interval: 31–42 %) in discards (kg.hour-1).

Primeiro registro da espécie exótica, plati Xiphophorus maculatus (Günther, 1866), na área de inundação urbana de um rio neotropical brasileiro

Abstract: Aim This work reports the first occurrence of the exotic species Xiphophorus maculatus (Günther, 1866) in the Sorocaba River Basin. The introduction of non-native fish species has become common and many species have been introduced mainly through sport fishing, aquaculture and aquarium keeping. In the case of the Poeciliidae, most of the introduced species that have been recorded come aquarium keeping. The environment where the specimens were captured had a large number of macrophytes due to anthropization and is located in a strictly urbanized area of the municipality. Methods The collection was done through a rectangular dip net, with measures of 70 cm x 60 cm and a mesh of 1 mm. The specimens were anesthetized in eugenol solution, fixed in 10% formalin solution and preserved in 70% alcohol. The specimens were later deposited in a scientific collection. Results The record includes two female specimens from an urban wetland on the Sorocaba River, São Paulo State, Brazil. Conclusions In the municipality of Sorocaba, 63 species of fish have already been identified, belonging to 7 orders and 19 families and 6 are exotic, such as the Xiphophorus maculatus. Urban floodplains are poorly studied environments, thus presenting great potential for the occurrence of species that have not yet been inventoried. The monitoring and inventory of exotic species must be carried out systematically so that mitigating measures can be proposed in relation to the control of these species, and this is one of the major causes of biodiversity loss. In addition, developing a program for returning unwanted fish to aquarium stores can be effective in preventing the introduction of new aquarium fish and displaying warnings informing of the negative ecological effects of releasing aquarium fish in all bags, fish plastics, and aquarium store websites.

Fishers can optimize gear design if the management system allows for enough flexibility: A modified SELTRA codend can reduce fish catch in the Danish trawl fishery for Norway lobster

Through an industry-science collaboration, a modified SELTRA codend consisting of a grid with scaring floats (GSF) was successfully developed by the fishing industry, and tested in a scientific trial on board a twin-rig demersal trawler. The selectivity of the gears used in the fishery needs to be tailored to each vessel and season, as quota availability differs across vessels and seasons. The modified gear aims at avoiding catching unwanted fish when targeting Norway lobster. The use of the modified codend showed good potential for effectively reducing catches of unwanted fish without affecting the catch of the target species Norway lobster. With respect to a standard SELTRA codend, the GSF design led to a significantly lower retention of unwanted fish, with 71 (61–79) % less cod, 94 (73–100) % less saithe and 22 (14–37) % less plaice being retained. The results show that fishers have the knowlegde to develop more selective gears. The authors argue that fisheries management should support such industry driven innovation through more flexible management approaches.

Developing and testing a novel active-selection (ActSel) bycatch reduction device to quickly alternate trawls between capture and release configurations with real-time triggering

Bycatch reduction devices (BRDs) allow selective release of unwanted fish (bycatch) during fishing operations, while retaining target fish. Existing BRDs use passive methods, exploiting differences in fish behavior, size, and/or shape to separate bycatch from target species. Recent availability of practical systems transmitting real-time video from trawls to the towing vessel during routine fishing opens the possibility to develop active selection (ActSel) BRDs, devices that allow trawlers to selectively trigger fish release when bycatch species are observed.Development through numerical modeling, scale-model tests, and full-scale, at-sea trials, resulted in an ActSel BRD system that, when triggered, quickly (average 10 s) and reversibly moved a mesh panel between configurations covering a release opening or leading fish out of that opening. A hydrodynamic kite across that selection panel’s leading edge drove it between catch and release positions. Manipulation of control lines by a remotely-controlled electromechanical reel adjusted the kite’s orientation, determining movements of the mesh panel. Results of full-scale testing of this ActSel system under commercial fishing conditions while trawling for Pacific hake (Merluccius productus) showed that ActSel operation effectively and reversibly changed movement of all fish from normal passage toward the codend to moving toward the release opening. While our sea trials occurred in the Pacific hake fishery, the ActSel has applications to other trawl fisheries, particularly fisheries where real-time video systems are used (i.e., Alaska pollock (Gadus chalcogrammus) fishery).

Fish Loss/Waste and Low-Value Fish Challenges: State of Art, Advances, and Perspectives.

The sustainability of fishery is a global challenge due to overfishing and reduced stocks all over the world; one of the leading factors of this threat is fish loss/waste. As a contribution to the global efforts towards a sustainable world, this review addresses the topic from different sides and proposes an overview of biorefinery approaches by discussing bioactive compounds that could be produced from fish loss (nitrogen compounds, lipids, minerals and pigments, and fish-based compounds such as chitosan). The second part of this review reports on the possibility of using loss or unwanted fish to design products for human consumption or for animal feeding, with a focus on economic criteria, consumers’ segmentation, and some examples of products. The final focus is on Food and Agriculture Organization FAO guidelines as a roadmap for the future with respect to solving this threat by addressing the problem from different sides (technology, skills, market, policy, social and gender equity, and infrastructures).

Reducing catch efficiency of rabbitfish (Siganus oramin) in a shrimp beam trawl fishery of the South China Sea

The bycatch of unwanted fish species is a main concern in shrimp beam trawl fishery of the South China Sea. This study evaluated the effect of using combined square-mesh and diamond-mesh codends (CSDM codends) on catch efficiency of a shrimp trawl fishery with the catch comparison and catch ratio approach. The trouser trawl method was applied using the commercial 22-mm diamond mesh codend (D22) as the baseline. The target species, greasyback shrimp (Metapenaeus ensis), and main fish bycatch rabbitfish (Siganus oramin) were chosen as the referred species. The results demonstrated that there was no significant change for the target species but a significant reduction on the unwanted fish bycatch when the CSDM codends were used. Compared with the D22 codend, the CSDM codends would reduce the catch efficiency of greasyback shrimp by less than 18% on average, and the reduction was not statistically significant; whereas catch efficiency of rabbitfish would be significantly reduced by more than 45% and the reduction was length-dependent. The results also showed that the catch efficiency of fish bycatch would reduce as the mesh sizes of the diamond-section of the tested codends increased. These promising results demonstrate that the CSDM codends have a potential to be applied to fishery management for mitigating fish bycatch in the shrimp fishery of the studied area.

Less is more – Basic quantitative indices for fish can be achieved with reduced gillnet sampling

Obtaining a representative sample is fundamental to the assessment of fish communities. In this study we used data from 99 different surveys of 29 artificial lakes in the Czech Republic to evaluate the precision of fish community indicator estimates based on reduced gillnet scenarios derived from triplet gillnets installed in each particular locality, depth strata and habitat. Forty-four indicators (based particularly on numbers and biomass per unit of effort – NPUE and BPUE, respectively) were compared between the full sampling design (three gillnets at every sampling location) and six reduced scenarios which were combinations removing one or two gillnets from the triplets. The whole community comparison found the accuracy (R2) between the full sampling design and reduced scenarios usually to be above 0.9. Strong accuracy was also found for species richness and mean fish weight. In individual species comparisons, accuracy above 0.75 was found for common species in a given habitat, whereas accuracy for less common species sometimes dropped below 0.5. Setting one gillnet in an appropriate depth strata and lake locality appears to be sufficient for unbiased overall NPUE, BPUE, and species composition estimates, and at the same time, reduces sampling effort and minimizes unwanted fish mortality. Capturing less common species in a given habitat is more or less accidental and additional sampling effort increased the probability of catching these species. On the other hand, methods targeting rare species of interest may be considered instead of increasing gillnet effort above the CEN standard.

Toxicological effect and behavioral response of a predatory Stinging Catfish, Heteropneustes fossilis exposed to three indigenous plant seed extracts

For the removal of undesired fish species from aquaculture ponds, an alternative to synthetic toxins is the use of botanical toxicants which are biodegradable and environmentally safer. Toxicological effects of distilled water, 50% ethyl alcohol, methanol and acetone extracts of three indigenous plant seeds, Jatropha carcus (Linn.), Hydnocarpus wightianus (Blume) and Aleurites moluccana (Linn. Willd) were studied on the predatory fish, Heteropneustes fossilis (Bloch) under normal laboratory conditions. Depending upon the type of plants, extracts and concentrations, percentage mortality varied. Behavioral activities increased with increasing concentrations. During exposure, fish exhibited discolouration, gulping for air, erratic swimming, loss of reflex, slow movement and ultimately became motionless before death . The extent of toxicity of extracts for J. carcus, H. wightianus and A. moluccana on H. fossilis could be ranked in the order: Acetone > methanol > 50% ethyl alcohol > distilled water. On the basis of LC50 values the most toxic was acetone extract of J. carcus seeds and least toxic was distilled water extract of A. moluccana seeds. It is suggested that these plant seed extracts would be helpful in aquaculture to remove unwanted fish species from culture ponds.
 Bangladesh J. Zool. 48(2): 379-391, 2020

Production performance of Pabda (Ompok pabda) and Gulsha (Mystus cavasius) with Rohu (Labeo rohita) in natural pond conditions

The study was carried out infourselected farmer’s pond in Netrokona sadarand Barhatta upazillas(sub district) under Netrokona district during April to September 2019 having average pond area of 0.14 haeach. The ponds were prepared by removing aquatic vegetation and unwanted fish and other animals, andapplying with lime at the rate of 250 kg/ha. Five days after liming, water was supplied from shallow tubewell to the ponds and filled up to the depth of 1.5 m. The fry of Pabda (Ompok pabda) and Gulsha (Mystuscavasius) with Rohu (Labeo rohita) were stocked at the rate of 175000; 87,500 and 2000/ha, respectively.After stocking, fish were fed at a rate of 5-12% of body weight with supplementary feed (30% crudeprotein). Fish sampling were done at monthly interval to know the fish growth status and also to adjust feedration. After six months rearing, fish were harvested by repeated seine netting. Total bulk weight and numberof fish from each pond was recorded. Survival and gross production of fish of each pond were estimated. Theharvesting weight of pabda ranged from 33 to 36g. While the harvesting weight of Gulsha and Rohu rangedfrom 26-27g and 591-614g, respectively. Based on the number of fish harvested at the end of the experiment,survival ranged from 75 to 88%.Total production of Pabda (O. pabda) and Gulsha (M. cavasius) with Rohuwas estimated at 5202, 1772 and 1066 kg/ha, respectively. The total production of fish as recorded in trialponds were 8043 kg/ha

Researchers say Europe’s ban on throwing unwanted fish overboard is backfiring

Researchers say Europe’s ban on throwing unwanted fish overboard is backfiring

Fishery spatial plans and effort displacement in the eastern Ionian Sea: A bioeconomic modelling

The management of fisheries requires well-planned approaches that consider the socio-ecological costs and benefits of management options while minimising conflicts among fishing practices. We developed a framework to anticipate the cost-effectiveness of several fisheries management options, including space-time closures, gear selectivity improvements, and fishing effort reduction of eastern Ionian Sea fisheries. We also examined to what extent these fisheries could be influenced by placing new aquaculture sites into specific areas. We used a dynamic space-time model considering the effect of possible fishing effort displacement on alternative marine areas. A fine-scale distribution of 6 species of high commercial importance, for the eastern Ionian fisheries (central Mediterranean), was used together with the fishing effort distribution of trawlers, purse-seines, and small-scale fisheries to track the implications on several bio-economic indicators. The study revealed that the stocks and the fisheries economics benefited from a 10% reduction in fishing effort for all fishery sectors, while the unwanted fish catch was slightly higher. Thus, although there are notable advantages, this management option is not sufficient to support an EU regulatory framework aiming to promote more selective fishing practices and mitigate unwanted catches. However, we showed that the protection of juveniles, by imposing selectivity improvements or space-time closures on trawlers, slightly reduced the unwanted catch. Nevertheless, the benefit for the majority of stocks and fisheries economics, during the five-year simulation period, was limited. In the case of space-time closures, this is attributed to the offset due to the fishing effort displacement towards other areas. While the benefit on fish populations by improving trawl selectivity, it depends on the species. Finally, the establishment of new aquaculture units could lead to a slight re-allocation of fishing effort along the border of the new sites without substantially affecting the profit of small-scale fisheries. Such findings are useful for fisheries management and broader spatial planning in the Ionian Sea. They will provide insight to policymakers and different fishing sectors, thus enabling a more transparent and participatory decision–making process.

Does the efficiency of a counter-herding device depend on seabed contact?

To prevent unwanted fish bycatch from entering the trawl, we modified a counter-herding device, FLEXSELECT, developed for a Northeast Atlantic Nephrops (Nephrops norvegicus) trawl fishery. FLEXSELECT, which was designed to direct fish away from the trawl by means of sweeping ropes in the herding area, has been shown to be highly effective on both roundfish and flatfish species. However, by adding sweeping elements we could be increasing the benthic impact of trawling. Therefore, in this study we investigated if the effect of FLEXSELECT can be maintained when raising the ropes off the seabed. A reduction in fish bycatch could still be achieved, but the effect of FLEXSELECTraised with respect to the previous design was significantly different for four of the seven species analysed. While for some species the effect was lower, it substantially increased for cod (Gadus morhua), making it highly relevant for the Nephrops fisheries, as well as for other fisheries in needs of avoiding cod catches. The results offer insights regarding species behavioural responses to FLEXSELECTraised, to be used for future developments of counter-herding devices in commercial fisheries without the addition of seabed impact to the baseline gears.

Using automated video analysis to study fish escapement through escape panels in active fishing gears: Application to the effect of net colour

Quantification of the escapement rate of unwanted fish through a selective device is usually based on catch comparison. This study proposes a new, time efficient method to automatically compare two selective devices by automated counting of fish escapements through each selective device based on video sequences. First, sea trials were conducted to record video sequences of fish escaping a white and black square mesh panel. Then, all of the underwater sequences were automatically analysed by a computer vision software for automated object detection and tracking. Finally, the algorithm was assessed using 150 min of video sequences analysed by humans. We observed that the variability in escapements rate between all the observers on reference video sequences could reach 5%. As the difference in escapements rate between the algorithm and the observers was lower than the variability between observers, the automated approach was validated. The software detected a significant difference in fish escapement rate according to the net colour in the camera field of view: 60% of all fish escaped through the white panel. Our results suggest that net colour influences the escape rates of fish. The colour of the selective device should therefore be investigated further with the aim of increasing their efficiency. Further development of the software could be done to identify species and size of the fish and assess the effectiveness of a selective device by species and size.

Automatic segmentation of fish using deep learning with application to fish size measurement

AbstractOne of the leading causes of overfishing is the catch of unwanted fish and marine life in commercial fishing gears. Echosounders are nowadays routinely used to detect fish schools and make qualitative estimates of the amount of fish and species present. However, the problem of estimating sizes using acoustic systems is still largely unsolved, with only a few attempts at real-time operation and only at demonstration level. This paper proposes a novel image-based method for individual fish detection, targeted at drastically reducing catches of undersized fish in commercial trawling. The proposal is based on the processing of stereo images acquired by the Deep Vision imaging system, directly placed in the trawl. The images are pre-processed to correct for nonlinearities of the camera response. Then, a Mask R-CNN architecture is used to localize and segment each individual fish in the images. This segmentation is subsequently refined using local gradients to obtain an accurate estimate of the boundary of every fish. Testing was conducted with two representative datasets, containing in excess of 2600 manually annotated individual fish, and acquired using distinct artificial illumination setups. A distinctive advantage of this proposal is the ability to successfully deal with cluttered images containing overlapping fish.

Behavioural and welfare implications of a new slipping methodology for purse seine fisheries in Norwegian waters.

The release of unwanted fish from purse seines whilst still in the water is termed slipping and may lead to significant mortality following release. The objective of this study was to determine the fish welfare implications of a new slipping methodology in which fish are released via a discharge opening formed in the bunt end of the purse seine net. Video analyses of collective and individual level fish behaviour were undertaken in the Norwegian mackerel and herring purse seine fisheries, to quantitively describe slipping behaviour and to determine its driving factors. The majority of fish escaped the purse seine with the schooling structure intact as part of large groups towards the end of slipping process, increasing their speed following escape. However, there was also a tendency (24% of all escapes) to escape in a manner likely to impact negatively upon their welfare, with a breakdown in schooling structure and physical contact with the fishing gear and conspecifics. The tendency to express such welfare compromising behaviour was higher for mackerel than for herring, but was also influenced by the vessel releasing the fish, the amount of fish being slipped, how long the discharge opening had been open and the particular slipping event. These results provide important information for future science-based development of welfare friendly slipping practises.

Controversial European policy bans ships from throwing unwanted fish overboard

Controversial European policy bans ships from throwing unwanted fish overboard

The challenges of the landing obligation in EU fisheries

A feasibility study was conducted on the impacts of the new Common Fisheries Policy (CFP) rules requiring catches in regulated fisheries to be landed and counted against quotas of each Member State - the landing obligation (LO), and that catch of species subject to the LO below a minimum conservation reference size (MCRS) be restricted to purposes other than direct human consumption. The aim was to estimate the level of discarded fish likely to be covered by the new rules, the impact of the rules on EU fisheries and the regulatory challenges and responses to them. Data from EU's Scientific, Technical and Economic Committee on Fisheries (STECF) database were analysed to estimate the volume of unwanted catches produced by EU fisheries. Views were sought from policy officials and fisheries scientists through a questionnaire on the implications of the LO and the control of fisheries across Member States, and the potential adjustments that might be needed. Findings show that 11% (44,000t) of the total catches of EU countries from which data were available are of fish under MCRS. The species with the highest volume of undersized discards associated with the lowest quota, which would potentially restrict the fishing opportunities for other quota species (i.e. choke species), are plaice and haddock with 18,000 and 14,000t of undersized fish respectively, followed by whiting and cod with 5000 and 6000t of undersized fish respectively. Discards data shows that the Netherlands, United Kingdom, France and Belgium will be most affected by landings for non-human markets. Findings also show that existing infrastructure at landing ports in all Member States is limited because there are currently limited facilities in place to handle animal by-products produced by the catching sector. Policy officials maintained that while they could support the fishing industry through funding programmes, it is the responsibility of fishers to ensure they have the right infrastructure to handle unwanted catches. The expectation is that the LO combined with the restriction to non-human consumption purposes will encourage fishers to internalise the costs of catching unwanted fish and motivate them to avoid unwanted catch. This will be realised if sufficient flexibility is given to fishers to find their own solutions to reducing unwanted catches. It is concluded that gear technology measures exist to enable the regulated fisheries to increase gear selectivity.