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By-Catch: Problems and Solutions
Abstract
By-catch is one of the most significant issues affecting fisheries management today. Incidental mortality of species which are long-lived and have low reproductive rates is a conservation problem affecting marine mammals, sea birds, sea turtles, sharks and other groups. By-catches can affect biodiversity through impacts on top predators, the removal of individuals from many species, or by elimination of prey. The by-catch issue is also one of waste; the millions of tons of protein dumped in the ocean, and the waste of animal lives is often condemned on moral grounds. For the economist, it generates additional costs without affecting the revenues, and may hinder profitability. For the fishers, it causes conflicts among fisheries, it gives fishers a bad public image, generates regulations and limitations on the use of resources, and frequently has negative effects on the resources harvested through the mortality of juvenile and undersized individuals of the target species before they reach their optimal size from the point of view of future yield.Several examples of major by-catch issues are described, focusing also on the solutions to the problems which have been developed by scientists, fisheries managers and members of the fishing industry itself. By-catch is an extremely complex set of scientific issues, not only an economic, political, or moral one. Although only a few fisheries include by-catches of the target species in their stock assessment (e.g. Pacific halibut), it is clear that by-catch management will be an integral part of most future ecosystem management schemes. These considerations, together with the introduction of environmental variability and a better handling of scientific uncertainty, should lead to more intelligent ways to harvest our resources.
... Overlapping use of the same fine-scale habitat with unmitigated fisheries could lead to a consequent change in behaviour, which inherently increases the chance of mortality. This would be detrimental for large, long-lived species whose populations are especially vulnerable to increases in adult mortality (Hall et al ., 2000 ;Lewison et al ., 2004 ). ...
Bycatch risk assessments typically rely on spatial o v erlaps betw een seabirds and fishing vessels but should also consider seabirds' position in the attraction spectrum. In v estigating seabird-fishery interactions in relation to habitat use is vital for species-specific risk assessments. To address this, we studied interactions bet ween soot y albatrosses (SA) and white-chinned petrels (WCP) with fisheries. GPS data from 20 SA and 18 WCP individuals from Marion Island were analysed alongside Automatic Identification Sy stem-deriv ed boat locations o v er tw o breeding seasons. We calculated encounter and attraction rates and correlated them with marine habitat characteristics. SA interactions occurred in deeper, warmer waters compared to their foraging habitat when vessels were absent, with 20% of individuals encountering and only 5% being attracted to boats. In contrast, WCP interactions occurred in shallo w, w arm South African shelf waters, consistent with their typical foraging habitats, with 72% encountering and 56% attracted to boats. These results highlight the need for continued reinforcement of mitigation measures for WCP. Despite the low attraction rates for SA, ongoing vigilance is required due to their smaller population size, which heightens the potential impact of illegal fisheries. The comparison of species along an attraction spectrum contributes to refining risk assessments and informs species-specific conservation strategies.
... For example, a number of fisheries have small fish protocols in place to ensure juvenile fish remain in the water and some protected species cannot be retained (e.g., sea turtles). Survival rates for discarded bycatch and the impacts on the ecosystem may vary (Hall et al. 2000); however the ecological impacts of bycatch are substantial (Kelleher 2005). In some fisheries, such as the mixed groundfisheries, discarding is not allowed, except for specifically authorized species. ...
This report analyzes the bycatch of marine species in Canada to assess the potential impacts on marine life, as well as to identify current policy gaps and potential solutions to mitigate bycatch. First, it reviews Canada’s management approaches to minimizing bycatch by analyzing Integrated Fisheries Management Plans (IFMPs) and associated Conservation Harvesting Plans (CHPs), as available. Second, it quantifies the extent of bycatch impacts, specifically the percentage of catch discarded and the potential for cumulative impacts, using the datasets available in Marine Stewardship Council (MSC) public certification reports for Canadian fisheries.
... To address the environmental impact of discarding bycatches back into the sea, numerous initiatives have been launched globally to mitigate these effects and reduce the volume of by-catches [43][44][45][46]. The conventional practice of discarding by-catches is recognized as problematic due to its adverse effects on the aquatic environment and the distribution of food within different layers of aquatic ecosystems. ...
Fish wastes pose environmental and economic challenges for companies operating in the field. The global fishing industry generates a substantial amount of waste, which has far-reaching consequences. Just to have a glance of the issue on a global scale, according to the Food and Agriculture Organization of the United Nations (FAO), nearly 50 million tons of fish are wasted every year, representing about 30% of the total global catch. The majority of this waste occurs at sea, where fish are discarded as by-catch or are not fully utilized; waste also occurs during processing, transportation, and retail. While the waste management costs continue to rise, these by-products also present an untapped potential in the form of valuable bioactive compounds. Some of the noteworthy compounds found in fish wastes include Omega-3 fatty acids (ω\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega $$\end{document}-3), collagen, and hyaluronic acid, all of which have substantial commercial value. The extraction of high-value compounds from fish waste is a promising way to reduce waste and create new products that can benefit human health and the environment. The full valorization of wastes and biomass is reached in biorefinery plants, where the combination of innovative separation technologies and reaction stages allows extracting high-quality final products with a very low impact on the environment. In this framework, we propose a novel process to extract ω\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega $$\end{document}-3 from fish wastes while keeping their integrity for further protein (collagen) extraction and improving the ω\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega $$\end{document}-3 quality compared to traditional thermal extraction systems. The process is designed using a feedstock derived from salmonid wastes and includes extraction using Supercritical Fluid (SCF)-CO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$CO_2$$\end{document}, followed by hydrolysis and vacuum distillation. We simulated the innovative process in Aspen Plus, a professional tool for chemical process design, providing key indications regarding the process feasibility (yields, flow concentrations, and basic equipment design). The process has been optimized with respect to recovery ratio, purity, and energy duties, providing a clear profile regarding the technical feasibility of the innovative process. Results show good efficiency of the proposed process, with a recovery of 96% and a purity of 77%, in good compliance with other green applications, such as pretreatment-assisted enzymatic extraction. According to detailed results on the final composition of products, the simulations have reported a very high ratio ω3/ω6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega _3 / \omega _6$$\end{document}, corresponding to recognized highly beneficial effects on health. All in all, the presented research demonstrates through quantitative data the feasibility of ω\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega $$\end{document}-3 production and provides a tangible instance highlighting how the circular economy paradigm can foster innovation within the agri-food industry. This is accomplished by utilizing technological solutions that have minimal environmental impact and emissions.
Graphical abstract
... Most of the seahorses enter the trade as incidental bycatch [9,14]. Unlike targeted or monitored fishing practices, bycatch is non-selective and leads to difficulties in accumulating data regarding both size of individuals collected and species-specific exploitation [7,11,[15][16][17][18]. ...
Tens of millions of dried seahorses (genus Hippocampus) are traded annually, and the pressure from this trade along with their life history traits (involved parental care and small migration distances and home ranges) has led to near global population declines. This and other forms of overexploitation have led to all seahorse species being listed in Appendix II under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The signatory nations of CITES recommended a 10-cm size limit of seahorses to ensure harvested individuals have reached reproductive maturity, and have thus had the chance to produce offspring, to maintain a more sustainable global seahorse fishery. We assessed adherence to CITES recommendations using DNA barcoding and size measurements to compare two prominent U.S. dried seahorse markets: (1) traditional Chinese medicine (TCM), and (2) non-medicinal ecommerce and coastal curio (ECC). We also estimated U.S. import abundance from CITES records. Of the nine species identified among all samples (n = 532), eight were found in the TCM trade (n = 168); composed mostly (75%) of the Indo-Pacific species Hippocampus trimaculatus, and Hippocampus spinosissimus, and the Latin American Hippocampus ingens. In contrast, ECC samples (n = 344) included 5 species , primarily juvenile Indo-Pacific Hippocampus kuda (51.5%) and the western Atlantic Hippocampus zosterae (40.7). The majority of TCM samples (85.7%) met the CITES size recommendation, in contrast to 4.8% of ECC samples. These results suggest non-size discriminatory bycatch is the most likely source of imported ECC specimens. In addition,
... The extent and magnitude of bycatch varies widely and involves a complex spectrum of biological, ecological, human, technological, economic and spatial dimensions; some fisheries can have negligible bycatch. Bycatch can negatively impact fishers (e.g. by generating costs or reputational damage), as well as commercial species, endangered, threatened and protected (ETP) taxa, and ecosystems (Davies et al., 2009;Dulvy et al., 2014;Gray and Kennelly, 2018;Hall et al., 2000;Kennelly, 1995;Stevens et al., 2000). 'Clean' fisheries with little bycatch therefore offers benefits to both fishers and the ecosystem, and documenting bycatch is a fundamental first step towards this goal. ...
... Shrimp trawls are unfortunately one of the least selective fishing gears, catching large quantities of non-targeted species (Hall et al., 2000;Nnelly, 1995). This by-catch is often discarded at sea and this has increased during the last few years (Sivanthan et al., 2016). ...
The by-catch and discards from shrimp trawl fishery have increased during the last few years. Leiognathus sp. is one of the most discarded fish species in the shrimp trawling fishery in Jaffna, Sri Lanka. Lack of information was found regarding the nutrient composition of Leiognathus sp. and therefore the present study was carried out to assess the presence of amino acids and fatty acids in whole-dried and mince-dried fish which are beneficial for human health. The total sum of amino acids was estimated to be 229.8 and 174.4 mg/g raw protein percentages in whole-dried fish and minced-dried fish, respectively. The protein content of fish is mainly explained by the sum of the total amino acids identified. The total lipid was 5.5% and 7.3% in whole-dried fish and minced-dried fish, respectively. Proline and glycine were found to be the abundant amino acids in both whole-dried and minced-dried fish. A total of 13 fatty acids in whole-dried fish and 14 fatty acids in minced-dried fish were identified in the present study. The n-3 polyunsaturated fatty acids were found to be one of the highly abundant compounds in this fish and docosahexaenoic acid is also considerably higher in amount. In the sense of higher availability of protein, storage of whole-dried fish will be a better option than minced-dried fish. Drying is one of the best and easiest methods to preserve this fish and dried fish products could be supplied to the local population at a low cost to overcome the nutrient deficiency among them. Alternatively, utilizing these bycatch fish is an effective method to reduce marine pollution as well.
... Individuals of S. lewini tend to make solitary movements away at night to feed on pelagic fish and squid, returning to the same or nearby aggregation sites the following days (Klimley 1993;Ketchum et al. 2014b). The species is also characterized by a differential habitat use by juveniles, which are born and grow in shallow coastal bays, and adults, which comprise most of the schools found at oceanic aggregation sites (Klimley 1983;Hall et al. 2000;Hinke et al. 2004). ...
The Eastern Tropical Pacific (ETP) is one of the last regions where large aggregations of the critically endangered scalloped hammerhead shark (Sphyrna lewini) can still be observed. In this regard, we comparatively assessed the seasonality in S. lewini’s relative abundance within three marine protected areas (MPAs) of the ETP and explored its relationship with environmental factors such as temperature. Abundance standardization via generalized linear mixed models revealed that Galapagos Islands (Ecuador) held an overall higher relative abundance of S. lewini when compared to Cocos Island (Costa Rica) and Malpelo (Colombia). The greatest relative abundance was observed from June to October for Cocos, followed by Galapagos (January, September, and November) and Malpelo (December, February, and March). Our results suggest that S. lewini observed relative abundances are significantly affected by water temperature and years (all three sites), and by the seasons, dive schedule, visibility and moon phase (to a lesser extend). This research contributes to the understanding of the temporal and spatial fluctuations of S. lewini at oceanic aggregation sites to improve the decision-making tools for the integral regional climate-smart management of the species. We recommended future studies to model the effect of climate change in the abundance at aggregation sites and potential distribution shifts across the ETP.
... The lack of proper management, the lack of longterm planning for the restoration of stocks, the lack of su cient monitoring of shing, in ation, and the unfavorable economic situation of shermen can be considered effective factors involved in the current situation (Moradi et al. 2013; Paighambari et al. 2017). The mortality of long-lived marine species with low reproductive rates is a major problem in species conservation and affects the sustainability of sheries in the seas (Hall et al. 2000). The amounts of bycatch obtained in different shing methods depend on the used shing gear. ...
This study investigates the composition of bycatch and the maturity status of some commercial fish caught by fishing boats equipped with shrimp trawls in the Dayyer-Nakhiloo and Mond marine protected areas in Bushehr, located in the north of the Persian Gulf. Cruises were conducted by fishing boats equipped with 27-foot length and 115-horsepower engines between August 18th and September 20 th in 2020 and 2021. The trawl nets were made of polyamide (PA) and had mesh sizes of 50 mm in the body and 40 mm in the bag (STR). After 32 haulings, a total of 37 aquatic species were caught as bycatch. Greater lizardfish ( Saurida tumbil ), largescale tonguesole ( Cynoglossus arel ), blue swimming crab ( Portunus segnis ), whipfin silver-biddy ( Gerres filamentosus ), spotted sicklefish ( Drepane punctata ), elongate sole ( Solea elongata ), and orange-spotted grouper ( Epinephelus coioides ) were the most frequently caught species in all seasons. The results of the bycatch weight showed that the highest and lowest amounts of bycatch weight were observed in the 18 th and 3 rd fishing operations in the Mond region, respectively, with 234 kg and 4 kg. Similarly, the highest and lowest amounts of catch per unit effort (CPUE) were observed in the 18th and 9th fishing operations in the Mond region, respectively, with 234 kg h ⁻¹ and 3.25 kg h ⁻¹ . The bycatch to shrimp ratio (r) was computed as 2.32:1. The results of species dominance showed that Acanthopagrus arabicus (9.4%), Scomberomorus commerson (7.75%), and Saurida tumbil (6.05%) had the highest percentage of abundance during the study period. Length frequency data of commercial fish caught showed that Parastromateus niger (44.19%) and Acanthopagrus arabicus (33.81%) had the highest percentage of mature fish in the specimens, while Scomberomorus commerson and Epinephelus coioides had the highest percentage of immature fish (100%). Overall, the present study indicates that bottom trawling by fishing boats in Dayyer-Nakhiloo and Mond marine protected areas poses a threat to the biodiversity of the Persian Gulf. An efficient management approach is therefore essential to promote responsible fisheries in the region.
Commercial fishing is a crucial industry in Alaska’s economy, but unsustainable fishing practices, especially bottom trawling, lead to excessive bycatch and economic discards. This poses a major threat to marine ecosystems and their biodiversity, which puts the resources within Alaska’s fisheries at risk of diminishing to a point where they cannot meet human demand. Through extensive research and evaluation of this issue and existing legislation that governs Alaska’s fisheries, we recommend the full implementation of two specific measures across all of Alaska’s fisheries. One is electronic monitoring on all vessels in the form of deep learning cameras, and the other is a “freeze the footprint” approach on bottom trawling, which protects key seafloor habitats within the existing area that has been damaged by previous trawling activity. These efficient methods are a safer alternative to on-site observation, and they will lead to a healthier seafloor ecosystem, which is essential for marine life. Alaskan communities rely on their fisheries, and maintaining healthy marine ecosystems is critical to economic stability.
The present study is the result of collective work on the analysis of the controversy surrounding the incidental capture of marine mammals and birds due to fishing in the Bay of Biscay. For this research project, the levers and obstacles to taking social and environmental issues into account in the political decision-making process and the management of incidental catches are studied. Among the levers, we evaluate the relevance of the principle of ecological solidarity from the environmental code in the resolution of the conflict. Consequently, this article is an opportunity to test the application of this principle and its possible consequences in the face of the problem of bycatch in the Bay of Biscay.
Several bycatch-reducing devices (BRD's) were compared for their effectiveness in reducing bycatch while maintaining catches of prawns in an estuarine prawn-trawl fishery in New South Wales (NSW), Australia. A solid separator-panel (the Nordmore grid), a soft separator panel (the commercially used blubber chute), and four secondary BRD's (the fisheye, extended mesh funnel, Allerio Brothers grid, and square-mesh panel) each attached to a Nordmore grid, were compared against each other in a series of paired comparisons in the Hunter River prawn-trawl fishery. The results showed that the Nordmore grid and all secondary BRD's caught less bycatch and more prawns than the commercially used blubber chute. Most bycatch seemed to escape with use of the Nordmore grid, and there was no significant advantage in adding a secondary BRD to this design. The efficiency of the Nordmore grid has led to its voluntary adoption by many commercial prawn-trawl fishermen throughout NSW estuaries.
Shipboard surveys were conducted in the summer of 1991 to estimate the abundance of harbor porpoises, Phocoena phocoena, in the northern Gulf of Maine and lower Bay of Fundy. The best estimate is 37 500 (95% CI: 26 600 to 86 400). The abundance estimate presented is substantially higher than previous estimates for the area. While the statistical precision that was reported here included some sources of uncertainty, others remain to be addressed. -from Author
This volume is based on the symposium and workshop held in La Jolla, California, in 1990. After a report of the workshop and a report to the United Nations Conference on the Environment and Development on significant direct and incident catches of small cetaceans, 51 papers on incidental catches, generally of small cetaceans are published. These are arranged regionally, covering the North Atlantic (including the Baltic and Mediterranean); Central America and Caribbean; W South Atlantic; Africa and Indian Ocean; Asia and North Pacific pelagic; E North Pacific; SE Pacific. As well as general studies of marine fisheries and their by-catches of cetaceans and other marine mammals, individual species studied are: harbour porposies Phocoena phocoena, franciscana Pontoporia blainvillei, marine tuxuci Sotalia fluviatilis, right whale Eubalaena glacilias, sperm whale Physeter macrocephalus, southern minke whale Balaenoptera bonaerensis and dusky dolphin Lagenorhynchus obscurus. Lastly, there is a section of causes and solutions to the reduction of net entanglement of small cetaceans. -J.W.Cooper
The behaviour of seabirds and the rate of incidental mortality were observed during commercial trawling operations for Patagonian toothfish (Dissostichus eleginoides) in the 1994/95 season near Macquarie Island and Kerguelen Island. Longlining for D. eleginoides and trawling for mackerel icefish (Champsocephalus gunnari) were also observed at Kerguelen. Many seabirds were constantly observed near the vessels, especially giant petrels (Macronectes halli and M. giganteus), black-browed albatrosses (Diomedea melanophris) and Dominican gulls (Larus dominicanus). White-chinned petrels (Procellaria aequinoctialis) were common only at Kerguelen. Bird mortality during trawling was zero at Macquarie Island and very low at Kerguelen; most was associated with a single vessel using a netsonde cable while targetting C. gunnari. Most mortality associated with both longliners and trawlers was of white-chinned petrels, with a lesser mortality of albatross species. Mortality rates associated with longlining in the Kerguelen region were lower than those reported for the South Georgia area, probably because the birds at the former site are distracted from the longlines by the discharge of offal from the side of the vessel opposite to where the longline is set.
Large-scale research vessel surveys were conducted annually from 1986 through 1990 by the US National Marine Fisheries Service to monitor the abundance of dolphin populations in the E tropical Pacific (ETP). Distribution maps are presented for all 29 species. Data from all five surveys were pooled to give single estimates of abundance in the EPT for 24 stocks of cetaceans. Abundance estimates totaled 9.6 million animals for all dolphin species (subfamilies Delphininae and Steninae), 292 800 for all species in the subfamily Globicephalinae, 45 300 for all species in the family Ziphiidae (beaked whales), 33 881 for all species in the superfamily Physeteroidea, and 14 431 for two species in the family Balaenopteridae (rorquals). -from Authors
Ten major categories of passive fisheries are identified, five of which take substantial numbers of cetaceans during the course of their operations: Atlantic Canada and Gulf of Maine groundfish gillnets; Atlantic Canada cod traps; Bay of Fundy and Gulf of Maine herring weirs; Atlantic Canada and Greenland salmon gillnets; and US east coast swordfish driftnets. The cetacean species most threatened by incidental mortality in commercial fisheries in this region are harbour porpoise Phocoena phocoena, which is taken in large numbers and the endangered northern right whale Eubalaena glacialis. -from Author
Examined the effects of method of obtaining estimates of small cetacean and seal bycatch on reports by inshore fishermen in Newfoundland and Labrador during 1990. Investigations without assessments of the methodology for obtaining bycatch reports cannot be evaluated or interpreted. Scaling corrections and improvements of survey methodology are discussed. -from Authors