Bycatch In Trawl Fisheries Research Articles

‘Data Deficient’ but potentially threatened: first biological observations on the poorly known quagga catshark (Halaelurus quagga)

Context The quagga catshark (Halaelurus quagga) is a small-sized (~370-mm total length), deep-water catshark (Family: Pentanchidae), assessed as Data Deficient on the IUCN Red List. Aim We aimed to bridge critical knowledge gaps on aspects of the life history and exploitation of H. quagga to make a meaningful Red List assessment, and develop management plans. Methods Specimens landed as bycatch in three harbours along the Laccadive Sea coast of south-western India were examined to gather the first information on exploited length classes and aspects of reproductive biology. Key results Halaelurus quagga had a female-dominated sex ratio, a positively allometric growth in females, and isometric growth in males. Mature H. quagga males ranged between 294 and 336 mm, and females between 315 and 370 mm, with pregnant females carrying two, three or four egg cases with embryos in each uterus. Conclusions This study provides the first information on the biology and exploitation of H. quagga, showing that the species is landed (and discarded) as bycatch in trawl fisheries, with the catches comprising a significant amount of reproductively active individuals. Implications The intense deep-sea bottom-trawling off south-western India is a major threat to H. quagga, and, if left unmanaged, could likely trigger a threatened category on the IUCN Red List.

Trouble in the trawls: Is bycatch in trawl fisheries preventing the recovery of sawfish? A case study using the US population of smalltooth sawfish, Pristis pectinata

All five species of sawfish (Family Pristidae), are among the most threatened families of elasmobranchs, and face significant threats from fishing, in particular trawl fisheries, and habitat loss. Unfortunately, there is little data on the level of sawfish taken in trawl fisheries outside Australia and the United States and case studies from these areas can provide a “risk analysis” for populations elsewhere. In the United States, bycatch risk for smalltooth sawfish is significantly higher for the southeast shrimp trawl fishery than all other fisheries assessed. Using new estimates of life history and population size, an updated population viability model was developed and trajectories using different scenarios of initial population sizes, fishery catches and post-release mortality were projected for 100 years. The simulated population trajectories for the assumed initial population sizes and fishing mortality ranged between population extinction, quasi-extinction, to a slight reduction in population size and in some cases the population continuing to recover. The most pessimistic scenarios were when the initial population was lowest and post-release mortality in the shrimp trawl fishery was highest. Quasi-extinction for some scenarios was between 6.9 and 22.8 years. While some scenarios suggest that smalltooth sawfish still can recover despite the potential for shrimp trawl fishing mortality, key input variables for these optimistic scenarios is the initial population size and the true level of fishing mortality. This uncertainty highlights the importance of improving our understanding of sawfish life history, captures in fisheries and their associated post-release mortality.

Trawl-related mortality and injuries to the southern king crab Lithodes santolla of Patagonia

The catch and discard of non-target species could have detrimental effects on bycatch, species due, among others, to the increase in mortality and prevalence of injuries. In Argentina, the southern king crab (SKC), Lithodes santolla, supports a profitable trap fishery but is also caught as bycatch in trawl fisheries. The aims of this work were: i) to quantify the mortality and injuries in SKC caught as bycatch in the hake fishery in San Jorge Gulf (southwestern Atlantic Ocean), ii) to assess the factors that affect their mortality and injury occurrence, and iii) to estimate their postdiscard mortality.Immediate mortality (IM) and injuries in SKC were recorded in hauls of the hake fishery, and then related to operational and biological variables. SKC vitality was assessed using the reflex action mortality predictor (RAMP) test. Postdiscard mortality was analyzed in aquaria and wild (sea cages) conditions. The IM of SKC in the common hake fishery was 31%. The IM, as well as increased injuries and decreased vitality, were directly associated with the time and conditions of air exposure. Both the IM and injury occurrence were also affected by biological variables such as the sex,size and molt stage. Postdiscard mortality was lower in wild conditions than in the aquaria (1%). Our results suggest that SKC could have high resistance to handling and high recovery capacity after its return to the sea. In consequence, the quick return of SKC to the sea may have a positive effect on SKC survival.

Bird scaring lines reduce seabird mortality in mid-water and bottom trawlers in Argentina

Abstract Seabird bycatch in fisheries, and the development of effective mitigation to minimize this, have been subject to increasing research attention over the past three to four decades. Trawl fisheries represent a particular challenge, as bird mortalities (especially highly threatened albatrosses and large petrels, Procellariforms) occur primarily through difficult-to-detect collisions with warp and net monitoring cables. Effectiveness of bird-scaring lines (BSLs) as a mitigation measure can be fleet-specific, and studies relating specifically to reducing collisions with the net monitoring cable are rare. To support improved assessment and mitigation of seabird bycatch in trawl fisheries, we studied the mortality associated with mid-water and bottom factory trawl vessels along the southern tip of the Argentine Patagonian shelf, across 2144 trawls from 2012 to 2019, with three specific objectives: (i) inform improved bycatch management in this (and other) trawl fisheries by analysing differences in seabird collision rates and outcomes between net monitoring and warp cables, as well as the effect of mitigation measures in reducing collisions; (ii) explore the effects of key fishing operation variables on seabird impact outcomes; and (iii) estimate the annual seabird mortality in the study fleet. We tested the efficacy of BSLs as a mitigation measure to reduce seabird mortality, on warps and net monitoring cables. Our results show that seabird mortality increases in the presence of a net monitoring cable. Our estimation of fishery-wide mortality without the use of BSLs includes 108 [31–186] Southern royal albatross (Diomedea epomophora) and 279 [108–465] Black-browed albatross (Thalassarche melanophris) killed annually by the collisions with the net monitoring cable. We demonstrate the efficacy of BSLs in reducing the number of collisions and in combination with no discarding of fishes, seabird interactions fell to c. zero. Our study builds the case for better bycatch data collection in trawl fisheries, the strong influence of discarding, and the feasibility of simple mitigation measures to reduce seabird bycatch, including on the net monitoring cable.

Mitigation of seabird bycatch in New Zealand squid trawl fisheries provides hope for ongoing solutions

ABSTRACT Although there is an increasing awareness of the high rates of seabird bycatch in trawl fisheries globally, there is relatively limited implementation of effective mitigation measures. Seabirds that are attracted to the stern of the trawl vessel to feed on fish-waste can be drowned or injured when they collide with warps/cables or when they become entangled in nets. Managing fish-waste discharge (processing offal and discards) and limiting access to it by scaring birds have been identified as the most effective measures to reduce seabird mortality from collisions with warps. New Zealand’s arrow squid (Nototodarus spp.) trawl fishery occurs during the austral summer and autumn when there is significant overlap with large numbers of foraging seabirds due to the proximity of breeding areas. Regulations introduced by the New Zealand government in 2007 requiring the use of devices to reduce warp strikes and operational procedures to manage fish-waste were independently implemented by the fishing industry in 2007 with the support of fishery regulators. The rate of capture of albatrosses by warps decreased from a mean of 2.9 birds per 100 tows during the period 2003 to 2006 to a mean of 0.7 birds per 100 tows after 2007. Long-term ownership of squid fishery quota catalysed the proactive engagement of the industry and has been reflected in a positive cultural shift in the attitude of fishers towards managing the risk of the capture of seabirds. Multi-sector collaboration and engagement allowed for the translation of experimental mitigation results into long-term, industrial-scale operational practices.

Biological parameters and spatial segregation patterns in sharks from the North Aegean Sea, Greece

Context Sharks are frequently caught as bycatch in trawl fisheries in the North Aegean Sea. However, very little information exists on their biology and ecology in the area. Aims Biological parameters and spatial segregation of sharks in relation to size class, sex, depth and geographic location were examined. Methods Morphological characteristics and generalised additive models were used to explore biological traits and aggregating behaviour respectively, by using data from the Mediterranean International Trawl Survey between 2014 and 2021. Key results Overall, 7761 specimens were measured, with Scyliorhinus canicula, Galeus melastomus and Squalus blainville being the most common species. Scyliorhinus canicula was found in shallow coastal waters, whereas the remaining species were detected in deeper waters. Conclusions Females were larger and heavier than males and the weight–length relationships corroborated size differences between sexes in all species, whereas allometric growth did not share the same patterns as those from the Mediterranean Sea. Generalised additive models showed that the distribution of dominant species is bathymetric and geographically dependent. Additionally, the depth and geographic segregation patterns are highly associated with ontogeny and not sex. Implications These findings highlighted the importance of incorporating elasmobranch behavioural characteristics in the poorly developed management regulations in the North Aegean Sea.

Bycatch of non-commercial batoids in the trawl fishery of south India: Status and conservation prerequisites

Bycatch of trawl fishery is a global concern and batoid fishes, including skates, rays and guitar fishes, are caught frequently as non-targeted species in commercial trawl fishery of India. While the commercial batoid species are documented separately in fishery data, a large number of non-commercial species do not form part of fishery data, even though many such species are listed as ‘Data Deficient’ in IUCN red list. A survey was conducted from July 2018 to June 2019 in the major harbours and landing centresof the south coasts of India to monitor the non-commercial batoid species in the trawl bycatch. Massive landings of non-commercial batoid species such as Torpedo sinuspersici, Narcine cf maculata, Orbiraja powelli Acroteriobatus variegatus and the occasional occurrence of Dipturus johannisdavisi, Benthobatis moresbyi, Narcine timlei and Plesiobatis daviesi have been recorded, besides the juveniles, sub-adults and few adults of commercial species Rhinobatos annandalei, Brevitrygon imbricata and Neotrygon indica from south India. The non-commercial batoids mainly inhabit continental shelf and slope regions of Indian coast where fishing pressure and efforts are high. When these k-selected species live in fishing zones with intense fishing pressure, data deficient species of batoids should be considered as threatened, and this paper discuss challenges in the sector, and forwards strategies for conserving non-targeted batoids.

Exploring epidermal mucus protease activity as an indicator of stress in Atlantic sturgeon (Acipenser oxyrinchus oxyrhinchus).

Atlantic sturgeon are anadromous fish that spend much of their life in near-shore environments. They are designated as "threatened" by the Committee on the Status of Endangered Wildlife in Canada and listed by the IUCN as "near threatened." In Canada, Atlantic sturgeon support small commercial fisheries in the Saint John River, New Brunswick, and the St. Lawrence River, Quebec. While occupying the marine environment, the species is susceptible to various anthropogenic stressors, including by-catch in trawl fisheries and through interactions with coastal engineering projects such as tidal power development. Atlantic sturgeon are also susceptible to implantation of acoustic tags used by researchers to study their movement ecology. These stressors can cause physiological and behavioural changes in the fish that can negatively impact their viability. Because the species are commercially important, and are also of conservation concern, it is important to understand stress responses of Atlantic sturgeon to better mitigate the effects of increased industrial activity in the coastal zone. This study used proteomics to identify and characterize protease activity and identify putative novel protein biomarkers in the epidermal mucus of Atlantic sturgeon. Changes in protein profiles in Atlantic sturgeon epidermal mucus as a result of by-catch and surgery stress were investigated using one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis and mass spectrometry. Proteolytic activity was identified and characterized using inhibition zymography, which provided information on the classes of proteases that are associated with stress. Samples were collected from Atlantic sturgeon on the Minas Basin, Nova Scotia, Canada, after capture by brush weir and otter trawl, and after surgical implantation of a V16-69 kHz VEMCO acoustic tag. Significant proteins found in the epidermal mucus include various inflammatory proteins, with calmodulin and complement 9 found ubiquitously, and more rarely lysosome C, identified in a brush weir capture sample. Serum albumin, a blood plasma protein, was another ubiquitous protein and verifies how the sample collection method provides a picture of the internal systems. Protease activity was dominantly exhibited by matrix metalloproteases and serine proteases in all sample collections, with serine proteases more active in otter trawl captures than in brush weir captures. By identifying potential protein biomarkers of stress, this study is an example of a non-invasive method for measuring stress in Atlantic sturgeon. Understanding the defence mechanism and release of non-specific biomarkers can be used to improve conservation regulations, as well as to contribute to the limited scientific knowledge on the stress response of Atlantic sturgeon.

Mollusk bycatch in trawl fisheries targeting the Atlantic seabob shrimp Xiphopenaeus kroyeri on the coast of Sergipe, northeastern Brazil

The malacofauna bycatch of sea-bob shrimp Xiphopenaeus kroyeri (Heller, 1862) trawl fisheries on the coast of Sergipe was studied for 5 years. The malacofauna bycatch considered was obtained in nine oceanographic sampling campaigns carried out between May 1999 and June 2003 in 18 stations distributed in six transects along depths of 10, 20 and 30 m. A total of 2,669 individuals of mollusk belonging to 54 species were captured on the 18 sea-bob shrimp trawl stations carried out along the coast of Sergipe. The considerable richness of mollusks was composed by 19 families and 31 species of gastropods, 12 families and 19 species of bivalves and 2 families and 4 species of cephalopods. The highest abundance were observed at stations 13 (373 individuals) and 16 (685 individuals) that represents the lowest depth (10 m) and the richness was higher at stations 15 and 12 (17 and 11 species, respectively) both located at the highest depth (30 m). Cephalopods had high frequency of occurrence being collected in all the stations and by far the most abundant group with a total of 2,488 individuals captured. On the other hand, gastropods (with 142 individuals found in 83.3% of stations) and bivalves (about 1% of the individuals collected) contribute with a much smaller percentage of individuals captured. Lolliguncula brevis (Blainville, 1823) was most representative cephalopod in number and frequency of occurrence. Arcidae, Conidae, Muricidae and Strombidae were the families with the higher number of species in the trawl-fishery. Among bivalves, Pitar arestus (Dall & Simpson, 1901) and Spathochlamys benedicti (Verrill & Bush [in Verrill], 1897) were the species with higher frequency of occurrence. Although the considerable sample effort and a number of mollusks captured as bycath, the richness estimators indicated that the species richness could increase with additional sampling effort in the study area. The present study expands the taxonomic alpha knowledge on the mollusk bycatch of sea-bob shrimp trawl fisheries on the northeastern coast of Brazil. However, it is of crucial importance to assess urgently the negative impacts of the sea-bob shrimp trawl fisheries on the benthic community of the entire coast of Brazil.

Pramod et al. methods to estimate IUU are not credible

We have examined the estimates in Pramod et al. of IUU Alaskan Pollock imported into Japan. Based on extensive knowledge of this fishery we find that their estimates are not substantiated by any known facts from the fishery. Whereas in a retracted version of the paper the authors estimated that 15–22% of Alaskan Pollock imported into Japan were IUU and listed the sources as discards & high-grading; unreported by-catch in trawl fisheries and unreported catches in artisanal fisheries, the authors have now added blending of IUU Pollock overseas with Alaskan Pollock as the dominant source of IUU Alaskan Pollock entering Japan. Remarkably, the authors estimate the same 15–22%, and continue to assert that discarded and high-graded fish in Alaska somehow make their way to Japan. None of the citations provided in the Pramod et al. paper provide any estimates of IUU, so their numerical estimates must therefore come from two confidential informants. No documentation of how the estimates are made is provided and the paper completely fails to meet normal standards of scientific replicability. The deficiencies in the estimate of IUU in Alaskan Pollock must cast serious doubt on their approach for all fisheries.

Catch and release patterns for target and bycatch species in the Northeast Atlantic deep-water shrimp fishery: Effect of using a sieve panel and a Nordmøre grid.

The Nordmøre grid and the sieve panel are two of the main devices used to reduce fish bycatch in trawl fisheries targeting shrimp species. However, even when using such devices, some small-sized fish enter the codend of the trawl together with the targeted shrimp. Therefore, bycatch reduction remains a problem in some shrimp fisheries. One such fishery is the Northeast Atlantic deep-water shrimp (Pandalus borealis) fishery where it is mandatory to use a Nordmøre grid. In this study, the bycatch reduction efficiencies and patterns for several fish species using the standard Nordmøre grid and an experimental sieve panel were investigated and compared. The effect of combining these devices was also explored. The bycatch reduction patterns differed significantly between the two devices and a more efficient bycatch reduction was obtained by combining them. However, while the loss of commercial-sized shrimp was only between 0 and 2% for the Nordmøre grid, it was between 37 and 56% for the tested sieve panel, making this completely unacceptable for commercial fishing. Therefore, before a sieve panel can be considered as an option for the fishery, other sieve panel designs that have a significantly lower loss of shrimp catches need to be identified.

SIZE AT FIRST MATURITY OF THE BLUE SPOTTED MASKRAY, Neotrygon kuhli lN INDONESIAN, WATERS

The biue spotted maskray, Neotrygon kuhtii is the most common rays occurred in Indonesian waters. This species is often caught as bycatch in trawl fisheries targeting demersal fishes and shrimps.

Note on Occurrence of Jaydia queketti (Osteichthyes: Apogonidae) from the Bycatch of Tropical Trawl Fishery

Three specimens of apogonids species of total length 72.69, 106.28 and 110.67 mm were caught off Tuticorin at the depths of 90-100 m as a bycatch on 1st January 2013 from the commercial trawler operated from Tuticorin Fishing Harbour, Southeast coast of India. In this paper, on the occurrence of Jaydia queketti was figured and the comprehensive diagnostic features of the recorded specimens were elucidated. The species of this genus Jaydia is distributed continentally and often caught as a bycatch from shrimp or fish trawl. These species are widely distributed in New Guinea, larger islands in the Coral Sea, Australia, Arabian Sea of India and also from Africa to Japan. Nevertheless, the present observation shows the occurrence of J. queketti from the by-catch of trawl fishery operated along Gulf of Mannar, Southeast coast of India.

Minimizing seabird by‐catch in industrial fisheries

Read the Feature Paper: Significant reductions in mortality of threatened seabirds in a South African trawl fishery; other Commentaries on this paper: Challenges in seabird by‐catch mitigation and the Response from the authors: Problems and solutions for seabird bycatch in trawl fisheries

Problems and solutions for seabird bycatch in trawl fisheries

Read the Feature Paper: Significant reductions in mortality of threatened seabirds in a South African trawl fishery and the Commentaries on this Feature Paper: Minimizing seabird by‐catch in industrial fisheries; Challenges in seabird by‐catch mitigation

Challenges in seabird by‐catch mitigation

Read the Feature Paper: Significant reductions in mortality of threatened seabirds in a South African trawl fishery; other Commentaries on this paper: Minimizing seabird by‐catch in industrial fisheries and the Response from the authors: Problems and solutions for seabird bycatch in trawl fisheries

Reproduction of the sandpaper skate, Bathyraja kincaidii (Garman 1908) in the eastern North Pacific

The sandpaper skate, Bathyraja kincaidii, is commonly taken as bycatch in trawl fisheries off central California. The impact of fisheries exploitation on this population is unknown, however little is known about its biology, including its reproductive life history. To determine reproductive aspects of B. kincaidii, 506 individuals were collected from commercial trawls, museum collections, and monthly trawl and longline surveys conducted by the National Marine Fisheries Service. Males ranged from 112 to 635 mm TL, whereas females ranged from 113 to 610 mm TL. Males reach first maturity at 440 mm TL and at ~3 years, whereas females reach first maturity at 450 mm TL, approximately 1 year later. Size and estimated age at 50 % maturity were similar between sexes: 492 mm TL and 7.5 years for males and 467 mm TL and 7.1 years for females. Gonadosomatic index (GSI) and hepatosomatic index (HSI) values indicate a continuous reproductive cycle, with a seasonal peak in the summer and fall, and a resting period following egg case deposition.

Combining in-trawl video with observer coverage improves understanding of protected and vulnerable species by-catch in trawl fisheries

Assessments of incidental wildlife mortality resulting from fishing rarely account for unobserved by-catch. We assessed by-catch of protected and vulnerable wildlife species in an Australian trawl fishery by comparing in-trawl video footage with data collected by an on-board observer. Data were obtained from 44 commercial trawls with two different by-catch reduction devices (BRDs). Eighty-six individuals from six major taxa (dolphins, sharks, rays, sea snakes, turtles and sygnathids) were documented from video analysis, including the endangered scalloped hammerhead shark (Sphyrna lewini) and the critically endangered green sawfish (Pristis zijsron). On the basis of the 2008–2009 fishing effort of 4149 trawls and scaling from these results, we estimated the annual catch of protected and vulnerable species (± 1 s.e.) at 8109 ± 910 individuals. Only 34% of by-catch was expelled through the BRDs. Independent observer data for the 44 trawls showed that 77% of the landed by-catch from these taxa were dead when discarded. The results indicate that unaccounted by-catch in trawl fisheries can be substantial, and that current methods of recording by-catch on-board vessels are likely to underestimate total fishing mortality. We recommend gear modifications and their validation through dedicated observer coverage, combined with in-trawl video camera deployments to improve current approaches to by-catch mitigation.

Assessment of relative performance of a square-mesh codend design across multiple vessels in a demersal trawl fishery

Implementing gear-based solutions to reduce bycatch in trawl fisheries can be difficult owing to fishers’ concerns over the fleet-wide applicability of results from discrete, highly controlled experiments associated with the development of such innovations. In New South Wales, Australia, a codend comprising a posterior section made from 35-mm square-shaped mesh (i.e. hung on the bar) was developed and subsequently recommended for partial implementation in a multi-species demersal trawl fishery (i.e. for use when eastern king prawn –Melicertus plebejus – is the primary target species). However, industry concerns over this design have to date prevented its implementation. Here, using direct twin-tow comparisons onboard a subset of the fleet, we quantitatively assessed the performance of the square-mesh codend, relative to the range of diamond-mesh codend designs currently being used, in terms of reductions in bycatch rates and shortfalls in catch rates of retained animals. Generalised linear mixed-effects modelling across all vessels showed that when eastern king prawn was the target species, the square-mesh codend significantly reduced bycatch rates (by ∼48%), but with an accompanying significant shortfall in catch rates of eastern king prawn (∼7%) and a substantial (though not statistically significant) shortfall in catch rates of an important component of the retained byproduct (whiting, Sillago spp., ∼36%). Partitioning of data by vessel revealed that such shortfalls in retained catch were evident for only some vessels, while the square-mesh codend performed as intended for the others. When school prawn (Metapenaeus macleayi) was the target species, substantial shortfalls in catches of school prawn (∼54%) in the 35-mm square-mesh codend confirmed that a codend of a smaller square mesh might be a more appropriate design under those circumstances. Potential strategies to address intra-vessel inconsistencies in performance of the square-mesh codend and thereby facilitate implementation of square-mesh codends in the fishery are discussed.

Reducing interactions between seabirds and trawl fisheries: Responses to foraging patches provided by fish waste batches

Seabird bycatch in trawl fisheries is driven by the attraction of birds to foraging opportunities, i.e., the discharge of catch processing waste and the contents of trawl nets. The risk of seabird captures increases with seabird abundance and exposure to fishing gear. We investigated (1) how quickly seabirds responded to discharges of trawl catch processing waste and (2) whether decreasing numbers of seabirds attended trawlers during processing waste discharge events as the time interval between these events increased. Waste was retained onboard the vessel for four different holding periods (30 min, 2 h, 4 h, 8 h), one of which was applied each day using a randomised block design. We determined seabird responses to batch discharge events after the prescribed holding periods using the abundance of large (albatrossses and giant petrels Macronectes spp.) and small (all other petrels except cape petrels Daption capense, shearwaters and prions) seabirds in a semi-circle of 40 m radius, centred on the stern of the experimental trawler. Seabird responses reflected the type of discharge released: birds moved from the air to the water, as the amount of food available increased from no discharge, through sump discharge to batch discharge. When discharge occurred, seabird abundance increased faster than could be resolved with the 5 min sampling period. However, abundance decreased more slowly over a 10–15 min period after the discharge event. The number of large seabirds attending the vessel during discharge events decreased significantly when waste was held for 4 h. For small birds, significant decrease occurred after 8 h. Such holding periods emphasise the tenacity of foraging seabirds, although we have not evaluated any long-term habituation to a particular discharge regime. While holding waste for less than 4 h may not reduce seabird attendance during discharge events, holding for shorter intervals can still reduce bycatch risk, e.g., prior to and during net shooting and hauling.