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Schematic diagram (not to scale) of coastal pelagic longline gear configuration used during 85 sets in the western North Atlantic, showing placement of hook–time recorders (HTRs) and temperature–depth recorders (TDRs). Lengths of buoy drops and leaders varied by season. For clarity, baits are not shown on hooks.
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The U.S. Atlantic coastal pelagic longline fishery that targets tunas and swordfish also interacts with a wide range of non-target species including billfishes and sea turtles. Preliminary studies indicate that a change in terminal gear from J-style hooks to circle hooks may reduce bycatch mortality, but the effects of this change on catch rates of...
Context in source publication
Context 1
... sections of pelagic longline gear were fished as part of normal commercial operations (Fig. 1). A section consisted of 90 hooks and was separated by either a radar-reflecting high-flyer float or radio location buoy. Size 16/0, 0 • off- set circle (Mustad #39660ST or #39666DT) and 10 • offset, size 9/0 J-style (Mustad #7698 or Eagle Claw #9016) hooks were alternated in each of the four sections. Each basket (the section of line ...
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... The fishing mortality of bycatch species may be mitigated by decreasing bycatch rates and increasing survival upon capture (Kerstetter and Graves, 2006). One way to decrease bycatch rates is by improving gear selectivity (O'Neill et al., 2019;Uhlmann et al., 2019). ...
... The catchability of circle hooks was found to differ among species, with lower catch rates for sea turtles and some species of billfishes, but higher catch rates for tunas, pelagic sharks and other species of billfishes (Reinhardt et al., 2018). The closed gape of circle hooks contributes to shallower and less internal hooking for most species, compared to the widely used J-hooks (Carruthers et al., 2009;Godin et al., 2012;Pacheco et al., 2011), improving the likelihood of survival upon release (Kerstetter and Graves, 2006). Circle hooks may thus offer a promising cost-effective measure to reduce the mortality of elasmobranchs caught on longlines, even though they might not reduce the probability of capture for all species. ...
... As such, the higher catchability of deep-water sharks with circle hooks likely results from a higher probability of the sharks being hooked after biting the bait. Circle hooks tend to slip over soft tissue and pivot as the eye of the hook exits the mouth, explaining why hooking predominantly occurs in the jaw (Kerstetter and Graves, 2006). The morphology of the mouths and feeding behaviour of deep-water sharks may promote greater effectivity of this hooking process. ...
The recognition that deep-water sharks are among the most vulnerable marine species to fisheries exploitation led to the implementation of fishing prohibition regulations in European waters. Reducing unwanted bycatch and mortality are key fisheries mitigation measure for the conservation of these species. Yet, few studies have investigated how to mitigate the common bycatch of these sharks on deep-water longline fisheries. Specifically, the potential of hook type as such a measure has never been investigated. Here, we conducted fishing experiments to test how circle hooks affect the catchability, the hooking position, and the overall condition of deep-water sharks, in comparison to the commonly used J-hooks in the Azores bottom longline fishery. We found that circle hooks did not significantly reduce deep hooking (throat or gut hooked), nor improve the overall condition of captured sharks, while the catchability of deep-water sharks on circle hooks was greater than on the J-hooks currently used in the local fishery. As such, circle hooks do not appear as a suitable measure to reduce deep-water shark bycatch and increase survival potential in deep-water longlining. Despite deep hooking being rare for the deep-water sharks caught with both hook types in the experiments, at-vessel mortality was still substantial (around 40%). Post-release survival remains mostly unquantified but preliminary results suggest it could also be high. This study highlights the urgent need for continued research addressing bycatch mitigation measures for deep-water sharks and identifying efficient strategies to reduce bycatch and increase survival.
... The decline of these species has focused attention at both the national and the international levels. Even for target fish that are not bycatch species, addressing the deterioration of stock status caused by overfishing requires reductions in unintentional fishing mortality (for instance, billfishes in the North Atlantic; Kerstetter and Graves 2006;Diaz 2008). ...
... The tip of the circle hook bends inward, and when a fish or sea turtle swallows the hooked bait, the circle hook less likely to hook inside the digestive tract; instead, as the hook exits the mouth, a torque causes it to hook through the edge of the mouth. This property allows for easy hook removal and has been reported to reduce the mortality rate of bycatch sea turtles on board and after release (Cooke and Suski 2004;Kiyota et al. 2004;Kerstetter and Graves 2006). Reports of positive effects of circle hooks include those for other species, such as reduced haulback and post-release mortality in sharks, reduced post-release mortality in swordfish (Xiphias gladius), and increased catch rates in tuna, the target fish. ...
CONTEXT:
The pelagic longline fishery has implemented bycatch mitigation measures to reduce sea turtle bycatch, but little attention has been given to their side effects on other endangered species.
AIMS:
To investigate the impact of using circle hooks and whole fish bait on the fishing mortality of target and non-target fish species, as well as bycatch species.
METHODS:
Long-term data collected from research cruises conducted by a pelagic longline vessel were used for analysis. A Bayesian quantitative evaluation was employed to assess the effects of the mitigation measures on the fishing mortality of various species.
KEY RESULTS:
The use of circle hooks led to an increase in mouth-hooking for both target and bycatch species, and the effect was proportional to hook size. Although deploying circle hooks did not increase fishing mortality per unit effort (MPUE) for shortfin mako sharks, combining to whole fish bait had a significant increase on MPUE.
CONCLUSIONS:
The study stresses the need for considering the trade-offs of bycatch mitigation measures such as circle hooks and fish bait among multi-taxa species.
Implications
The necessity for quantitative assessments of bycatch mitigation measures before implementation is highlighted to avoid unintended consequences on endangered species and ensure effective conservation in pelagic longline fisheries.
... For conservation purposes, the ideal scenario would be to avoid interactions between pelagic longlines and non-target species, yet with the overlap of geographic ranges and habitats of target and nontarget species it would be unrealistic to expect no interactions of nontarget species with the fishing gear (Kerstetter & Graves, 2006;Zollett & Swimmer, 2019). In spite of that, it is crucial to implement measures that could minimize encounters of these animals with pelagic longlines, as well as measures that together with good handling practices could improve their at-haulback and post-release survival rates. ...
A meta‐analysis of 40 publications totalling 59 experiments was undertaken to review and assess the effects of changing the hook (circle vs. J‐hooks or tuna hooks), bait (fish vs. squid) and leader (wire vs. nylon) type on retention and at‐haulback mortality rates of teleosts (tunas and billfishes), elasmobranchs and sea turtles caught on shallow‐set and deep‐set pelagic longline fisheries.
Circle hooks are a promising approach to mitigate the impact of pelagic longline fisheries on sea turtles, as they reduced sea turtle retention rates. The adoption of circle hooks would, however, also lead to a decrease in swordfish retention, the main target species of shallow‐set pelagic longlines.
Using fish as bait resulted in lower retention rates of sea turtles, highlighting that option as an additional measure to further mitigate sea turtle bycatch. The bait type had non‐significant effects on sharks, except for blue shark and shortfin mako, for which at‐haulback mortality rates were significantly higher with fish bait.
The use of nylon leaders instead of wire leaders could serve as a conservation measure for sharks, as they reduced the retention of blue shark without adversely impacting the catches of swordfish. The results on the effect of the leader material types should, however, be interpreted with caution owing to the limited information available reporting on leader material effects.
When considering future research directions, priority should be given to experimental field work on the effects of leader material and on deep‐set longlines. Evaluating the post‐release survival of species should also be a priority.
... Considering that circle hooks have been associated with significant decreases in injury and mortality rates of bycatch species, it has been mandatory for all ICCAT fleets since 2022 to either employ circle hooks or utilize finfish bait. Furthermore, the use of circle hooks is obligatory in the US longline Atlantic fishery [3,28]. Since January 2020, the pelagic longline fleet operating in the Azores is required to use straight circle hooks with a gap of at least 30 mm [29]. ...
... Although this study showed a tendency for the CLP18 and RT to catch more small swordfish, in general, other studies have presented no effect of hook types on length at capture for this species [3,30,80]. Regarding sea turtles, almost all circle hook types are related to low catches of small individuals, mainly the larger CLP18 and CLP18O hooks. This result is in agreement with size-selectivity studies performed for this species [23,32,31], which affirm that larger gears reduce turtle capture and prevent smaller individuals, with relatively small mouths, from ingesting the hook. ...
... The use of circle hooks is related to a significant change in the anatomical hooking location for the majority of species caught in the pelagic longline fisheries [20,23,25]. The anatomical hooking position directly influences the survival at haulback since the jaw-hooking, compared to deep-hooking, reduces the animal injury and allows it to continue to swim and breathe while on the line [3]. The pelagic longline trial in the Azores showed that there is a tendency for the circle hooks to lodge in the mouth more than in deep-hooking positions when compared to the traditional J-hook. ...
The threat of population declines caused by pelagic longline fisheries in the Atlantic has increased the concern to find strategies that minimize the bycatch and mortality of non-target marine animals. Gear modification, such as the use of circle hooks instead of conventional J-hooks, has been identified as an effective bycatch reduction strategy in different pelagic longline fisheries around the world. This study aimed to verify the effectiveness of the use of circle hooks by quantifying catch rates, relative size selectivity, and anatomical hooking position for the most common target species (swordfish, Xiphias gladius , and blue shark, Prionace glauca ), and some bycatch species (loggerhead sea turtles, Caretta caretta , and shortfin mako, Isurus oxyrinchus ) caught by the Azorean longline fishing fleet. The trial was conducted for five consecutive years (2000–2004) using eight different types of hooks. In general, the blue shark catches using circle hooks were significantly higher compared to J (Mustad 9/0). The circle hooks also showed high probabilities of catching juvenile blue sharks. Conversely, the circle hooks were efficient in reducing the loggerhead sea turtle bycatch and were related to fewer catches of small sea turtle individuals. The use of circle hooks was also associated with reduced swordfish catches compared to J (Mustad 9/0), and the effect of hook types on length at capture was only significant for Circle (L. & P. 18/0—CLP18) and Ringed Tuna (RT). No significant differences were observed comparing hook type to either catch rates or size selectivity for shortfin mako. Additionally, circle hooks were more likely to lodge in the mouth than in deeper anatomical positions, when compared to J (Mustad 9/0), for the four species analysed. The present study demonstrated that the use of circle hooks could mitigate the impact of the pelagic longline fisheries in the Azores by decreasing the bycatch of sea turtles and reducing animal injuries caused by deep hooking.
... A nonoffset (08 offset) J hook has a point parallel to the hook shank (Prince, Ortiz, and Venizelos, 2002), whereas an offset hook has the point bent sideways (either right or left side),~58-258, relative to the shank (Swimmer et al., 2010;Thomas et al., 2007). In the Pacific Ocean, the offset angle plays a major role by influencing the catch rate and survival rate of targeted and nontargeted species (Kerstetter and Graves, 2006;Prince, Ortiz, and Venizelos, 2002). However, hook type, including size and shape, used in isolation or in combination with bait selection clearly plays a significant role in improving fishing selectivity and reducing the capture of nontargeted species in several fishing activities (Gilman et al., 2006;Piovano, Swimmer, and Giacoma, 2009;Read, 2007). ...
... This is related to the shape of the hook point bent toward the right and better hooking efficiency, in addition to higher bait-holding efficiency. Kerstetter and Graves (2006) reported a high overall hooking rate for J hooks compared with circle hooks for tuna and swordfish, which reveals the behavioral difference between tuna and needlefish. The reversed hook ranked second in terms of its hooking rate, with 3.85%. ...
... Regarding hooking positions, among the three types of hooking positions-hooking at the jaw, throat, and gut hooking-jaw hooking highly prevailed in an offset kirbed hook (64.7%), followed by the offset reversed hook and nonoffset straight hook at 57.3% and 39.1%, respectively. Similar results were observed for the 3.5 sun Japanese tuna hooks (27%) on the Agatti Island of Lakshadweep (Kumar et al., 2013) and an offset circle hook to reduce the rate of deep hooking and increase mouth hooking in pelagic fishes, such as Atlantic bluefin tuna and yellowfin tuna and billfish (Kerstetter and Graves, 2006;Prince, Ortiz, and Venizelos, 2002;Skomal, Chase, and Prince, 2002). However, in contrast, straight shank J hooks had a 70% rate of jaw hooking (Sahu et al., 2020). ...
Vasanth, K.; Muthupandi, K.; Naganandhini, V.; Kumar, M.; Krishnan, A.; Patolla, H., and Radhakrishnan, K., 2023. Effect of J-hook shapes on catch rate, efficiency, and hooking position of Needlefish: Evidence from Palk Bay, India. Journal of Coastal Research, 39(5), 933–939. Charlotte (North Carolina), ISSN 0749-0208.
The efficiency of different shapes of J hooks No. 11 (nonoffset straight hook, 10° offset kirbed hook, and 10° offset reversed hook) in needlefish longline fishing gears was studied in 24 fishing grounds in Palk Bay, India, from, February to July 2022. A total of 24 fishing trips were conducted for each experimental gear for the comparative study, with 14,400 hooks, with a total catch of 582 fish during the study. The result was that the kirbed hook had the highest percentage composition of the needlefish (37.36%), followed by the reversed hook (31.79%) and the straight hook (30.75%). Further, the overall hooking rate was higher for the kirbed hook than for the straight hook (13.43% vs. 8.60%). Considering the catch rate, the overall catch per unit effort (CPUE; individual/200 hooks) of the kirbed hook was higher (9.08 vs. 7.45) than that of the straight hook, whereas for the straight hook, the CPUE of nontarget species (0.29) was much higher than that of the kirbed hook (0.12). In terms of the targeted species, the Ablennes hians showed the highest CPUE of 3.78 individuals/200 hooks followed by Tylosurus crocodilus crocodilus (1.78), Strongylura strongylura (1.38); the least dominant CPUE was T. choram (0.94). The percentage of hooking position in the jaw was higher in the kirbed hook than that of the straight hook (64.7% vs. 39.1%) and was found lower in the gut system (11.5% vs. 28.5%). Among the three hook shapes tested, the overall performance of the 10° offset kirbed hook was found to be better than the other 10° offset reversed and nonoffset J hook in terms of a higher catch efficiency, hooking rate, CPUE, and hooking position for needlefish (<0.05).
... Pelagic stingrays are the only known whiptail stingray (Family Dasyatidae) commonly caught as incidental bycatch by pelagic longline fisheries targeting tunas (Family Scombridae) and swordfish, Xiphias gladius. Pelagic stingrays are considered one of the top 10 bycatch species within these fisheries composing up to 20% of bycatch within the western Atlantic, Indian, and Pacific oceans (Kerstetter and Graves 2006) with significantly higher catch rates when smaller or J-style hooks are used (Piovano et al. 2010). Pelagic stingrays are also occasionally caught in drift gillnets in the eastern Pacific (Mollet 2002), midwater (100-150 m) trawl nets in the Arabian Sea (Purushottama et al. 2022), and in both Atlantic and Pacific purse seine fisheries (Wilson and Beckett 1970). ...
... Fisheries Implications.-While pelagic stingrays are currently of little concern to commercial pelagic fisheries due to their relatively low susceptibility and high survival rates during haulback (Kerstetter and Graves 2006, Cortés et al. 2010, Coelho et al. 2012, as management shifts from species-specific to ecosystem-based approaches, documenting species' movement patterns will be important for future bycatch avoidance and habitat-standardized stock assessment modeling. Data from this research highlights the temperature and depth ranges used by pelagic stingrays, and this information can be used to reduce incidental bycatch by recommending alteration of commercial gear deployment to mitigate overlap (Sims 2010), or adjustments to fishing locations to prevent encounters with vulnerable species (Wang et al. 2023). ...
The pelagic stingray, Pteroplatytrygon violacea , is commonly encountered as bycatch in pelagic longline fisheries targeting Swordfish, Xiphias gladius , and tunas; however, very little is known about its habitat use. To better assess the utility of the technology and attachment method, four pop-up satellite archival tags (PSATs) with short, 13-day durations were deployed on pelagic stingrays in 2010 and 2011 in the South Atlantic Bight (n = 2) and the northern Gulf of Mexico (n = 2). Analysis of the minimum straight-line distances from the first transmission locations compared to release locations showed that pelagic stingrays moved from 151.0 to 258.0 km [mean (SD) = 190.8 (46.6) km] or between 11.6 to 19.8 km day ⁻¹ . Data also indicates pelagic stingrays undergo small diel vertical migrations with stingrays inhabiting slightly warmer [20.95 (3.4) °C], shallower [128.6 (99.8) m] waters at night, compared to cooler [19.7 (3.0) °C], deeper [167.0 (112.4) m] waters during the day. Understanding habitat use and behavior of less economically important species, particularly those that compose a substantial portion of bycatch like pelagic stingrays, will help fisheries managers account for these interactions with more economically valuable target species, as well as advance the overall understanding of pelagic ecosystems and aid in conservation efforts.
... Longline is a popular type of ecofriendly fishing gear that is operated in all types of fishing crafts (Løkkeborg and Bjordal, 1992). Longlines are used throughout the world's oceans to harvest fast-moving fish, such as swordfish, tunas (Kerstetter and Graves, 2006), and needlefish (Ilaiyaraja, 2016). The quantity of fish caught in longlines is influenced by various factors, such as type and thickness of material used for longline construction, depth of operation, size of hook, duration of soaking hours, fishing ground distance from the shore, and location (resource differences among areas). ...
... Another study found a 36% higher CPUE in circler hooks than the EZ baiter circle hooks (Woll et al., 2001). By using circle hooks (18/0), catching of bigeye tuna has increased by almost 40% (Kerstetter and Graves, 2006). Several studies also reported that CPUE was remarkably higher for target species than nontarget species when the circle hook was used in the longline fishery (Falterman and Graves, 2002;Promjinda et al., 2008). ...
The contribution of needlefishes from the Gulf of Mannar coast has been remarkable and is presently exploited by pelagic longlines. The J hook is extensively used in longline fishing in the Indian region to capture carnivore fishes, including needlefish. Catch rate significantly differed between the hook numbers. In this context, three hook numbers of 10 J, 11 J, and 12 J were studied from January to May 2022. Results showed that the Ablennes hians was the dominant fish caught (47.9%), followed by Tylosurus crocodiles (22.2%), T. choram (16.6%), and Strongylura strongylura (13.3%); weight-based catches of T. crocodiles (39.7%) were dominantly higher, followed by A. hians (35.9%), T. choram (13.8%), and S. strongylura (10.6%). The two-way ANOVA results revealed that a significant (p ,0.05) difference occurred between the hook number and the number of species caught. The largest number of fish were caught with hook number 12 (3769), followed by hook number 11 (2745) and hook number 10 (1445). However, the highest weight of 2749.74 kg was recorded with hook number 11 and the lowest of 1602.65 kg in hook number 10 (p ,0.05). This is related to fewer fish caught with hook number 10 and heavy fishing pressure on subadults (,50 cm) due to the use of hook number 12. Considering the maximum total length and weight, the optimum hook number for the commercial exploitation of needlefishes was hook number 11. The catch per unit effort disproportionately increased with the increasing of the hook number; the significant higher contribution of 48.
... Blue sharks are the main bycatch target in longline fisheries and gillnet fisheries [27,28]. Surveys show that in many countries or regions, blue shark account for an average of a third or even more than half of the total catch in their large pelagic fisheries [29][30][31][32][33]. The fins of the blue shark are the traditional seafood, and its meat can be made into fish balls [27,32]. ...
Numerous studies have shown that type II collagen (CII) has a potential role in the treatment of rheumatoid arthritis. However, most of the current studies have used terrestrial animal cartilage as a source of CII extraction, with fewer studies involving marine organisms. Based on this background, collagen (BSCII) was isolated from blue shark (Prionace glauca) cartilage by pepsin hydrolysis and its biochemical properties including protein pattern, total sugar content, microstructure, amino acid composition, spectral characteristics and thermal stability were further investigated in the present study. The SDS-PAGE results confirmed the typical characteristic of CII, comprising three identical α1 chains and its dimeric β chain. BSCII had the fibrous microstructure typical of collagen and an amino acid composition represented by high glycine content. BSCII had the typical UV and FTIR spectral characteristics of collagen. Further analysis revealed that BSCII had a high purity, while its secondary structure comprised 26.98% of β-sheet, 35.60% of β-turn, 37.41% of the random coil and no α-helix. CD spectra showed the triple helical structure of BSCII. The total sugar content, denaturation temperature and melting temperature of BSCII were (4.20 ± 0.03)%, 42 °C and 49 °C, respectively. SEM and AFM images confirmed a fibrillar and porous structure of collagen and denser fibrous bundles formed at higher concentrations. Overall, CII was successfully extracted from blue shark cartilage in the present study, and its molecular structure was intact. Therefore, blue shark cartilage could serve as a potential source for CII extraction with applications in biomedicine.
... Longline is a popular type of ecofriendly fishing gear that is operated in all types of fishing crafts (Løkkeborg and Bjordal, 1992). Longlines are used throughout the world's oceans to harvest fast-moving fish, such as swordfish, tunas (Kerstetter and Graves, 2006), and needlefish (Ilaiyaraja, 2016). The quantity of fish caught in longlines is influenced by various factors, such as type and thickness of material used for longline construction, depth of operation, size of hook, duration of soaking hours, fishing ground distance from the shore, and location (resource differences among areas). ...
... Another study found a 36% higher CPUE in circler hooks than the EZ baiter circle hooks (Woll et al., 2001). By using circle hooks (18/0), catching of bigeye tuna has increased by almost 40% (Kerstetter and Graves, 2006). Several studies also reported that CPUE was remarkably higher for target species than nontarget species when the circle hook was used in the longline fishery (Falterman and Graves, 2002;Promjinda et al., 2008). ...
Naganandhini, V.; Muthupandi, K.; Vasanth, K.; Neethiselvan, N.; Padmavathy, P., and Radhakrishnan, K.,. Influence of hook number on species composition, catch rate, and size of needlefishes in the Gulf of Mannar, India. The contribution of needlefishes from the Gulf of Mannar coast has been remarkable and is presently exploited by pelagic longlines. The J hook is extensively used in longline fishing in the Indian region to capture carnivore fishes, including needlefish. Catch rate significantly di ered between the hook numbers. In this context, three hook numbers of 10 J, 11 J, and 12 J were studied from January to May 2022. Results showed that the Ablennes hians was the dominant fish caught (47.9%), followed by Tylosurus crocodiles (22.2%), T. choram (16.6%), and Strongylura strongylura (13.3%); weight-based catches of T. crocodiles (39.7%) were dominantly higher, followed by A. hians (35.9%), T. choram (13.8%), and S. strongylura (10.6%). The two-way ANOVA results revealed that a significant (p <0.05) di erence occurred between the hook number and the number of species caught. The largest number of fish were caught with hook number 12 (3769), followed by hook number 11 (2745) and hook number 10 (1445). However, the highest weight of 2749.74 kg was recorded with hook number 11 and the lowest of 1602.65 kg in hook number 10 (p <0.05). This is related to fewer fish caught with hook number 10 and heavy fishing pressure on subadults (<50 cm) due to the use of hook number 12. Considering the maximum total length and weight, the optimum hook number for the commercial exploitation of needlefishes was hook number 11. The catch per unit e ort disproportionately increased with the increasing of the hook number; the significant higher contribution of 48.
... Due to their closed shape, circle hooks tend to lodge at or close to the mouth as opposed to J-hooks that easily become embedded in the digestive tract (Carruthers et al., 2009;Pacheco et al., 2011;Godin et al., 2012). Individuals caught on circle hooks are thus more likely to survive (Kerstetter and Graves, 2006), reducing the lethal effects of pelagic longlines even if not necessarily reducing the risk of capture. To our knowledge, the comparative effects of circle versus J-hooks on deep-water shark catch had not been tested until 2018 when it was first investigated in the Azores. ...
Deep-water sharks are highly diverse, vulnerable, and understudied as a group, despite the increasing pressures on their populations. Twenty-five species of deep-water sharks have been recorded in the Azores, an oceanic archipelago in the mid-North Atlantic, that are regularly caught as bycatch in hook-and-line fisheries. Avoiding the bycatch of deep-water sharks presents multiple challenges due to their high catchability, difficulties in correctly identifying species, and the general lack of data on these species. This review summarizes the findings of recent studies from the region, providing an up-to-date science-based framework for mitigating bycatch effects of Azorean hook-and-line fisheries. Several depth-based, area-based, and gear-based measures have been studied that demonstrate the potential to either avoid or increase the survival of deep-water shark bycatch. However, these measures may have limited efficacy for some species (e.g. highly mobile species) and thus, limited widespread applicability. Convincing fishers to avoid deep-water shark bycatch is also a challenge given the antagonistic interactions with sharks damaging the catch and fishing gear, while simultaneously a market incentive for shark liver oil remains. It highlights the need to proactively engage fishers and incentivize the mitigation of bycatch of deep-water sharks in Azorean waters.
