Bycatch Levels Research Articles

Raised‐Footrope Gill‐Net Modification Significantly Reduces Subadult Atlantic Sturgeon Bycatch

AbstractBycatch is a major problem in most commercial fisheries around the world and is among the greatest challenges for fisheries managers tasked with conserving, protecting, and sustaining marine resources. Bycatch of protected species is particularly problematic because even small levels of bycatch mortality can hinder conservation efforts. The federally protected Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus is one such example. Unknown numbers of Atlantic Sturgeon are caught as bycatch in commercial gill‐net fisheries along the U.S. Atlantic coast, with discard mortality rates as high as 51%. The Striped Bass Morone saxatilis sink gill‐net fishery in the James River, a tributary to Chesapeake Bay, is the only inshore fishery in Virginia with mesh sizes (13.3–20.3‐cm stretched mesh) that are large enough to have high levels of Atlantic Sturgeon bycatch. This study was conducted during the spring fishery and examined a modified gill‐net design that incorporated a raised footrope at the bottom of the net, creating an approximately 1‐m space between the benthos and the net. The modified net was fished alongside conventional commercial gear to evaluate catch rates of Striped Bass and Atlantic Sturgeon in each gear. Our findings showed that the experimental net significantly reduced bycatch of Atlantic Sturgeon (64.3%) and significantly increased the landings of Striped Bass (45.6%). This gear should be considered as a management option for the spring Striped Bass fishery in Virginia and any fishery in which subadult Atlantic Sturgeon are the primary bycatch. Additional research on seasonal orientation of Atlantic Sturgeon in the water column is needed before adopting the raised‐footrope design in the presence of adults on spawning runs.

Tracking young-of-the-year gray seals Halichoerus grypus to estimate fishery encounter risk

The current level of annual incidental bycatch of gray seals Halichoerus grypus in the New England sink gillnet fishery is the highest for all marine mammal species in the USA. One way to evaluate the risk of bycatch is to examine the risk of encounter between an animal and fishing gear based on the animal’s habitat use in relation to fishing activity. Here we used satellite telemetry deployed on 30 gray seal pups in 2019 and 2020 to measure the risk of encounter with large-mesh sink gillnet fishing effort throughout the Gulf of Maine and southern New England. We estimated relative encounter risk within 30 min grid cells in each calendar quarter based on the overlap of seal presence and fishing effort, and then validated the expected risk based on bycatch events reported by independent observers on board fishing vessels. The relative risk of seals encountering gillnet fishing gear was highest off southeastern Massachusetts in spring. Patterns in the estimated encounter risk fit our expectation that relatively high levels of habitat use and fishing effort correspond to increased encounter risk. The approach taken here can be used to identify times and areas of high encounter risk to justify altered fishing practices for purposes of avoidance, or to target observer monitoring intended to characterize and quantify bycatch. Mitigation strategies will need to be continuously monitored and updated to incorporate new information as conflicts with fisheries and gray seals are likely to continue.

Spatiotemporal models highlight influence of oceanographic conditions on common dolphin bycatch risk in the Bay of Biscay

The population of short-beaked common dolphins Delphinus delphis of the Bay of Biscay (northeast Atlantic) has been subjected to potentially dangerous levels of bycatch since the 1990s. As the phenomenon intensifies, it represents a potent threat to the population. Here, we investigated the relationship between bycatch mortality and oceanographic processes. We assumed that oceanographic processes spatiotemporally structure the availability and aggregation of prey, creating areas prone to attract both common dolphins and fish targeted by fisheries. We used 2 datasets from 2012 to 2019: oceanographic data resulting from a circulation model and mortality data inferred from strandings. The latter allows location of mortality areas and quantification of the intensity of mortality events at sea. We fitted a series of spatiotemporal hierarchical Bayesian models using integrated nested Laplace approximations (INLA). Results provided first insights on how bycatch of common dolphins in the Bay of Biscay might be related to key seasonal and dynamic oceanographic features. We showed that from a statistical predictive point of view, the monthly trend of 2019 bycatch mortality could be predicted with few oceanographic covariates. This study highlights how gaining knowledge about environmental influences on interactions between short-beaked common dolphins and fisheries could have great conservation and management value. Identified relationships with oceanographic covariates were complex, as expected given the dynamic aspects of oceanographic processes, dolphins and fisheries distributions. Further research focusing on smaller time scales is needed to elucidate proximal drivers of common dolphin bycatch in the Bay of Biscay.

Low mitochondrial genetic diversity in the Indian Ocean humpback dolphin Sousa plumbea in South African waters

The Indian Ocean humpback dolphin Sousa plumbea has been described as South Africa’s most endangered marine mammal due to its low abundance, reliance on coastal habitats with increasing anthropogenic threats and high rates of mortality from bycatch in bather protection nets (BPNs). Although the species has been well studied in South Africa, only a single study has examined its molecular ecology to date, and its population structure remains poorly understood. However, understanding population structure is vital for the conservation and management of a species. To address these research gaps for S. plumbea in South African waters, we analysed the mitochondrial D-loop of 157 museum skin and tooth samples collected between 1963 and 2017 from across the species’ geographic range in South Africa. Our data show that the humpback dolphin has extremely low mitochondrial diversity (haplotype diversity, HD = 0.47; nucleotide diversity, π = 0.2%) with only 3 haplotypes identified, which is comparable to the Critically Endangered Māui dolphin Cephalorhynchus hectori maui and the Critically Endangered Mekong population of Irrawaddy dolphin Orcaella brevirostris. Mitochondrial genetic diversity has not changed significantly in the last 50 yr, despite the high levels of bycatch in BPNs over this time period. Furthermore, we found no evidence of differentiation between dolphins from the KwaZulu-Natal Coast and the Cape South Coast (Western Cape and Eastern Cape). The extremely low mitochondrial diversity we found adds to the growing body of evidence that the humpback dolphin is becoming increasingly vulnerable and that urgent conservation efforts are required for the survival of the species.

Incidental capture of seabirds in Argentinean side-haul trawlers

SummaryBetween April 2008 and July 2015, we conducted a total of 18 trips on five different side-haul trawlers fishing within the Argentine Exclusive Economic Zone, monitoring 486 hauls. We observed 100% of the hauls and monitored trawl cables for 136.7 hours, about 5% of the trawl effort, to identify the levels of seabird bycatch from net entanglements and collisions with trawl cables. A total of 35 net entanglements of White-chinned Petrels Procellaria aequinoctialis, Great Shearwaters Ardenna gravis, Black-browed Albatrosses Thalassarche melanophris and Southern Royal Albatross Diomedea epomophora were recorded, all of which occurred during the autumn and winter. Additionally, 656 seabird collisions against trawl cables were recorded including 39 heavy, 96 medium and 521 light. Further, we recorded nine Black-browed Albatrosses and two Great Shearwaters potentially dead. Although in the study fishery the number of deaths in the trawl cables could surpass the number of birds incidentally killed in nets, the mortality rate caused by the latter type of interaction far exceeds those observed in nets from other trawl fisheries operating in the Patagonian Shelf. Fortunately, 26% of the seabirds entangled in the net were recovered and released alive, which indicates that awareness and training in safe bird handling and release may improve captured seabird survival rates. The main objectives of this work is to highlight a little-studied source of seabird mortality by entanglement, to generate discussion on potential technical mitigation measures for side-haul trawl fisheries, and to propose crew training in safe handling and release of seabirds as an immediate mitigation measure.

Fishing and trade of devil rays (Mobula spp.) in the Bay of Bengal, Bangladesh: Insights from fishers’ knowledge

Abstract Devil rays (Mobula spp.) are globally threatened cartilaginous fishes that have attracted global conservation concern owing to their high extinction risk and lack of protection in many countries. Limited resources and data on threatened marine species, including devil rays, impede conservation actions, particularly in developing countries, many of which have high biodiversity. Devil ray catch is a component of artisanal fisheries in Bangladesh, but data on their fisheries and trade are limited. To characterize devil ray fishing practices, fishers’ perception and trade, 230 fishers and traders were interviewed between 4 June 2018 and 22 June 2019, in four areas of south‐east Bangladesh. Catch data were also opportunistically collected at landing sites. Six devil ray species were documented, caught in an array of gill nets, set‐bag nets and longlines. All interviewed fishers reported life‐long devil ray bycatch in some numbers, and also noted a decline in catch over the last decade. Bottom trawling, increased bycatch levels, increased demand for devil ray products and, in some cases, ecosystem changes were identified by fishers as threats to devil ray populations. Unregulated and undocumented trade and retained bycatch, especially by gill nets and set‐bag nets, are fuelled by local consumption of devil ray meat and international trade in meat and gill rakers. Compliance with international trade control treaties for all Mobula spp. or the Bangladeshi law protecting Mobula mobular was low, with the majority of fishers (87%, n = 174) unaware of their existence. To manage devil ray fisheries, and prevent possible population declines, we propose a combination of legally enforced gear modifications, and catch and trade control through community‐owned implementation strategies. Additionally, we propose the simultaneous implementation of inclusive, community‐based awareness and stewardship projects in conjunction with a coast‐wide ray monitoring programme. Finally, we emphasize that more research and action rooted in a sustainable fishery model is urgently needed to protect Bangladeshi devil ray populations.

Determining the fundamental metrics of pot entrances for New Zealand scampi, Metanephrops challengeri

Bottom trawling is a fishing method that typically produces high levels of bycatch and is associated with benthic habitat damage. Pots (also known as creels or traps) are used as a less impactful alternative to trawling in a range of crustacean fisheries and has been proposed as a method to harvest New Zealand scampi (Metanephrops challengeri). However, pots designed in Europe for the ecologically similar Norway lobster (Nephrops norvegicus) failed to capture scampi at an economically viable rate. Therefore, a series of laboratory experiments were conducted to investigate the behaviour of scampi around pots and to identify the drivers of successful entries. These experiments were conducted in flume tanks with the entry performance of standard and modified designs contrasted with a control. Scampi were significantly more likely to enter a control pot than either a standard or modified pot entrances. The width of the entranceway was the biggest hinderance to scampi entering pots, as further experiments showed that scampi were significantly more likely to enter the control (15 cm wide) or 12.5 cm entrances than 7.5 cm entrance. The height of the entrances had no impact as the control, 12.5 cm, 10 cm and 7.5 cm high entrances had similar likelihoods of success. Lastly the angle of the ramp also had a significant effect on the likelihood of scampi entering the pots, with a 20° ramp having a higher likelihood of success than the 30°,40° and 60° ramps These results show that scampi require wide, gently sloping entrances to consistently enter pots. Consequently, for a scampi potting fishery to be successful, NZ scampi-specific pot designs should be developed and tested.

Multiple stressors and data deficient populations; a comparative life-history approach sheds new light on the extinction risk of the highly vulnerable Baltic harbour porpoises (Phocoena phocoena)

Many endangered marine mammal populations are difficult to study, spread out over large areas, and capturing them for branding and research purposes would be unethical. Yet, they are in urgent need for assessment and conservation actions. We suggest collecting data from other more abundant populations of the same species, with careful consideration of body size, age at sexual maturity, and ecological conditions to produce scientifically sound best approximations of vital rates of data deficient endangered populations. The genetically distinct Baltic Sea harbour porpoise population amounts to about 500 animals and is classified as ‘Critically Endangered’ according to the IUCN red list. Data deficiency on nearly all demographic parameters have precluded systematic investigations of the relative importance of stressors affecting population viability. We took a comparative life history approach and investigated the phenotypic plasticity in somatic and demographic vital rates of seven larger, well studied North Atlantic harbour porpoise populations, enabling us to approximate the missing pieces of the life history of the Baltic population. We parameterized a stochastic, individual-based population model, and performed a population viability analysis for a range of biologically realistic parameter values and scenarios of environmental stressors. The baseline scenario was based on the most representative samples of healthy harbour porpoise populations and challenged with three different levels of bycatches. Due to high levels of endocrine disruptive contaminants observed in Baltic harbour porpoises, we also investigated the effect of a possible reduction in fecundity. Subsequently, the combined effects of bycatches and reduced fecundity were investigated in terms of population growth rate and quasi-extinction risk. The Baltic harbour porpoise population is viable in the baseline scenario without anthropogenic stressors. However, even the lowest estimated bycatch level of 7 individuals per year will lead to a population collapse to ≤50 animals with high probability (0.4–1.0) over the next century, assuming an intermediate or low (<73%) fecundity. Adult survival is of critical importance and mitigation of fishery impacts and reduction of anthropogenic disturbances in the identified main breeding areas are recommended.

Changes in Shrimping Effort in the Gulf of Mexico and the Impacts to Red Snapper.

Despite a complex management landscape and decades of overfishing, Red Snapper (Lutjanus campechanus) stocks have grown substantially in the Gulf of Mexico and restrictions on the fisheries that catch them are being loosened. This year, annual shrimping effort was allowed to increase by 21% after National Marine Fisheries Service scientists concluded that the resulting bycatch of Red Snapper would only reduce the annual allowable catch in other fisheries by ∼1% and have no impact on population growth. Nonetheless, the recreational fishing sector intensely campaigned against this rule, fueled by wild mischaracterization of shrimp trawl bycatch in media outlets targeting anglers. Here, we aim to elevate the debates surrounding Red Snapper management by presenting scientific and historical context for the potential impacts from shrimping. We discuss our views of the current problems facing Red Snapper and key ecological questions to address for more effective management of this resource.

Bycatch in local fishery disrupts natural reestablishment of Eurasian otter in western Norway

AbstractLack of proper estimates of nonreported bycatch has made it difficult to evaluate the actual impact of bycatch in many local fisheries. For the Eurasian otter (Lutra lutra), there are no published estimates on the extent to which bycatch is unreported, despite nonreporting being a well‐known issue. Through public outreach efforts in local news and media we collected information from citizen scientists on nonreported otter mortalities of a small‐scale fishery in western Norway along the recent natural expansion front of otters. We compared this to deaths that were properly registered by local authorities. In total, cause of mortality was determined from 218 otters between 2003 and 2018. We found that the chances of a mortality being properly reported varied between type of death. Drowning in fyke and gillnets were the most common cause of mortality, and at least 61 and 69% of these deaths were never reported, respectively. The high level of bycatch occurring in the otters' current region of expansion is likely to have demographic impacts and hinder otter reestablishment in the area. Banning the use of fyke nets and setting a minimum fishing depth for gillnets would enhance otter recovery and simultaneously alleviate bycatch of other nontarget species in the region, while having little economic impact on a fishery which is mostly noncommercial. The case of the otter is a classic example of lack of communication between government agencies which have so far failed to establish platforms where issues like this can be discussed and solved by adequate law implementation.

A Data-Informed Approach for Identifying Move-on Encounter Thresholds for Vulnerable Marine Ecosystem Indicator Taxa

The United Nations General Assembly has called for the adoption of conservation management measures to protect vulnerable marine ecosystems (VMEs) from significant adverse impacts outside of areas of national jurisdiction. In response, many regional fisheries management organisations (RFMOs) have implemented move-on rules triggered by encounter threshold levels for the biomass of VME indicator taxa retained as bycatch. However, due to uncertainty of the relationships between catch, catch efficiency and the in-situ biomass of VME indicator taxa, move-on rules alone may not be enough to prevent significant adverse impacts on VMEs. Although spatial management measures present one possible solution to these concerns, a lack of empirical data on the distribution of VMEs within the high seas means spatial management is often informed by model predictions of the spatial distribution of VME indicator taxa. Given the uncertainty associated with predicted distributions, move-on rules can provide immediate responses when spatial management measures may not be providing the expected conservation benefits. Using bycatch data from 9,771 New Zealand bottom trawls within the South Pacific RFMO Convention Area, we illustrate a data-informed approach for selecting high move-on encounter thresholds that may suggest the predicted distributions of VME taxa used to underpin spatial management are highly inaccurate. The reasoning that high thresholds act as a safeguard against uncertainty in the performance of spatial management measures requires untested assumptions regarding the level of permissible bycatch before further management action is required, with the acceptance of those assumptions a management decision balancing the sensitivity of the move-on rule with uncertainty regarding the effectives of the spatial management measures. Additional work is required to support these management decisions, including the determination of taxa-specific catchability estimates, and the seafloor density/biomass of VME indicator taxa that represents a VME. Obtaining this information will allow for the identification of encounter thresholds that are more ecologically meaningful. In the interim, the choice of thresholds should be re-evaluated as more experience with their application is gathered.

Fishery bycatch is among the most important threats to the European population of Greater ScaupAythya marila

SummaryFor Greater ScaupAythya marila, classified as ‘Vulnerable’ on the European Red List of Birds, the south-western Baltic Sea is one of the most important wintering sites in Europe. In this area, a large concentration of gillnet fishery temporally overlaps periods of the most abundant occurrence of foraging diving birds. The aim of the article is to show how bycatch can impact the population of a diving duck. To assess this, we calculate the Potential Biological Removal (PBR) for the studied Greater Scaup population and we model the population change according to age-structured matrix models. Summing all the available recent figures on Greater Scaup bycatch in north-west Europe yields an estimated mean annual total of 3,991 individuals (2% of the flyway population). For a baseline stable population, an age-structured matrix model indicates that at this bycatch level the Greater Scaup population that winters in north-west Europe will decrease by 36% over the next 30 years, qualifying the status of the population as ‘Vulnerable’ according to IUCN criteria. As this population also experiences decline prior to bycatch, this decrease will be 57%, which qualifies the status as ‘Endangered’. PBR as an indicator of population vitality does not work in our case because the PBR-informed allowable bycatch values have a significantly negative impact on the population. Our results indicate unambiguously that fishery bycatch is among the most important threats responsible for the Greater Scaup’s decline. While recent data suggest that some improvement has taken place in the species’ status over the last 10 years, measures to protect Greater Scaup from bycatch are required. The solution should involve the prohibition of gillnet fishing in selected key sites and the use of mitigation techniques in other areas.

Distribution, habitat use, and abundance of the endangered franciscana in southeastern and southern Brazil

AbstractThe franciscana (Pontoporia blainvillei) is endemic to coastal waters from Brazil to Argentina. The species is regarded as one of the most threatened cetaceans in South America due to high bycatch levels. Four management units (FMAs) were defined throughout the species’ range. FMA II includes states along southeastern and southern Brazil, and represents one of the least known units. Recently, genetic analysis proposed that FMA II comprises two distinct populations and its range should be divided into FMA IIa and IIb. In December 2008 and January 2009 aerial surveys were conducted to assess the distribution and to estimate abundance of franciscanas off FMA II. A total of 54 groups were seen (average group size = 2.76, SE = 0.17) in shallow (mean depth = 7.15 m, SE = 7.08) coastal habitats (average distance from the shore = 6.48 km, SE = 6.28). Abundance corrected for perception and availability bias was estimated at 6,827 (CV = 0.26) franciscanas in FMA II, and at 1,915 (CV = 0.32) and 4,353 (CV = 0.24) franciscanas in FMA IIa and FMA IIb, respectively. This study indicates that, at least during the summer, franciscanas aggregate in shallow coastal habitats. Current estimates of incidental mortality in FMA II correspond to 4.4%–7.3% of the estimated stock size, suggesting high, likely unsustainable bycatch.

Decline towards extinction of Mexico's vaquita porpoise (Phocoena sinus).

The vaquita (Phocoena sinus) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr−1. We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6–19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.

CPOD successful in trial for detecting Māui dolphin outside harbours

ABSTRACTCritically endangered Māui dolphin (Cephalorhynchus hectori maui) are found exclusively off the west coast of New Zealand’s North Island. One important data gap troubling efforts to reduce the current unsustainable level of bycatch is the limited information on the offshore and alongshore limits of their range. Passive acoustic monitoring studies could address this data gap, but Māui dolphin habitat is dominated by a sandy substrate that can shift greatly in the strong local currents. In February 2016, a short pilot CPOD deployment was thus attempted as a first step to see if the equipment could be deployed and recovered in the area and if the data collected would be viable, with a second unit deployed inside a harbour for comparison with earlier TPOD data. The pilot was largely successful, and roughly 11% of all minutes in the core habitat location contained detections of clicks attributed to Māui dolphin. A visual inspection of the data suggests some trends with diel and tidal patterns. Further work of this type is thus recommended.

Population growth of an endangered pinniped—the New Zealand sea lion (Phocarctos hookeri)—is limited more by high pup mortality than fisheries bycatch

AbstractThe endangered New Zealand sea lion, Phocarctos hookeri is killed as incidental bycatch in a trawl fishery operating near their second largest population on Campbell Island in New Zealand’s sub-Antarctic. Using the Potential Biological Removal (PBR) procedure to assess the sustainability of this bycatch for the sea lion population on Campbell Island indicated that annual bycatch estimates, particularly following the implementation of bycatch mitigation measures, are below the PBR threshold of 25 (derived using a precautionary approach). Preliminary Population Viability Analysis (PVA) modelling supported the finding that current bycatch levels, especially given a strong male bias (98%) in bycatch, are sustainable for this population. Models showed that reducing pup mortality through management actions, such as installing ramps in wallows where large numbers of pups drown, would lead to increased population growth. While obtaining more accurate data on population status and demographic parameters for the Campbell Island population should be a priority, this will take many years of research. The PBR and PVA tools demonstrate that contemporary conservation management should continue to focus on increasing pup survival while maintaining mitigation approaches that have reduced bycatch to low levels, together with high observer coverage to sustain confidence in annual bycatch estimates.

Spatiotemporal bycatch analysis of the Atlantic halibut (Hippoglossus hippoglossus) longline fishery survey indicates hotspots for species of conservation concern

The Atlantic halibut (Hippoglossus hippoglossus) longline fishery is the second most valuable groundfish fishery in Atlantic Canada and received Marine Stewardship Council certification in 2013. The bottom longline fishery accounts for most halibut landings but incidentally catches nontargeted species (bycatch). Since 1998, Fisheries and Oceans Canada and the halibut fishing industry performed annual longline surveys across the Scotian Shelf and Southern Grand Banks stock management area to monitor halibut abundance, and at‐sea observers also recorded bycatch information. We examined the species composition and proportion of the survey bycatch and analyzed temporal and spatial trends in standardized weight of (a) halibut catch, (b) total bycatch, and (c) bycatch of species of conservation concern. From 1998 to 2016, 70% of the total catch by weight and 85% by number of individuals were bycatch. Over 100 identified species of finfish, sharks, skates, benthic invertebrates, marine mammals, and seabirds were caught as bycatch in the survey. This included four species listed under the Species at Risk Act (Northern wolffish, Anarhichas denticulatus; spotted wolffish, A. minor; Atlantic wolffish, A. lupus; Atlantic cod, Gadus morhua), and another 14 species awaiting a listing decision based on assessments by the Committee on the Status of Endangered Wildlife in Canada. Generally, the standardized weight of halibut and barndoor skate (Dipturus laevis) increased over time, while Atlantic cod, spiny dogfish (Squalus acanthias), white hake (Urophycis tenuis), and thorny skate (Amblyraja radiata) decreased. Spatial patterns indicated high bycatch levels on the southern Scotian Shelf and southern edge of the Southern Grand Banks, with hotspots for certain species of conservation concern. Our results identify temporal trends in threatened species and areas where they are susceptible to the Atlantic halibut longline fishery which can inform recovery strategies, bycatch levels and spatial zoning in fisheries management and marine conservation.

The net buyback and ban in St. Croix, U.S. Virgin Islands

The gill and trammel net ban and buyback were two of the most politically sensitive management reforms in St. Croix, U.S. Virgin Islands. The purpose of the net ban was to protect parrotfish populations, reduce by-catch, and minimize gear-habitat interactions whereas the aim of the buyback was to mitigate the economic hardship imposed by the ban. This paper describes the development of the net fishery and management efforts to protect parrotfish populations and coral reef habitats focusing on the performance of the ban and buyback. The study drew from 43 in-person interviews with select user groups and secondary sources such as government reports and databases.Our analysis suggests that these reforms had limited success. While local fishery managers promoted a participatory approach, shifting policy directives, implementation delays, limited buyback assistance, and high forgone earnings had unforeseen consequences. Most net fishermen substituted the banned nets with ‘modified’ small mesh seine nets, which were opposed by most stakeholders since they felt that their use defeated the purpose of the ban. The study also found that, with the exception of curtailing the dumping of spoiled fish on land, conflicting views about the health of parrotfish and surgeonfish stocks, excessive by-catch levels, and damaging gear-habitat interactions remained. Most net fishermen believed that the ban had advanced resource conservation; however, other stakeholders had more guarded or skeptical views. The Crucian experience with these reforms suggests that incentive-based regulatory approaches deserve greater attention as a means to improve management outcomes and minimize distrust in the management process.

Exploring the role of fishers knowledge in assessing marine megafauna bycatch: insights from the Peruvian longline artisanal fishery

AbstractNovel approaches are required to estimate the bycatch associated with artisanal fisheries. Foremost among these is the use of fisher knowledge (FK). An interview survey was conducted in ports along 2631 km of the Peruvian coast to assess the spatial patterns and bycatch rates of marine megafauna of the artisanal longline fishery and its relation with vessel characteristics and fishing operations. The survey allowed the assessment of 18% of the fleet, while only 1% of the Peruvian longline fleet has been monitored with on board observations in the past. The results indicate that big vessels (higher capacity, longline length and number of hooks) that travel long distances (average distance to coast: 123 nm) mainly catch turtles and show a small amount of seabird bycatches in north‐central Peru. Small vessels especially impact turtles in southern Peru and near the coast (63 nm on average). Contrary to previously published information, which indicates a low level of cetacean bycatch in this fishery, a group of fishers reported more than 1000 cetaceans were incidentally captured in 2009. Using FK allowed to integrate different sources of information and scale the implications of artisanal fisheries in terms of bycatch. FK could further be used to help managers deal with the uncertainties in the dynamics of these generally data‐ poor social‐ecological systems.

Seabird bycatch mitigation trials in artisanal demersal longliners of the Western Mediterranean.

High numbers of seabirds are killed annually worldwide in longline fisheries. In the Mediterranean, this mortality is seriously affecting the viability of seabird populations, in particular of the three endemic shearwaters. Even so, there is currently no specific seabird mitigation requirements for the longline fleet operating in this area. From 2013 to 2014, we assessed the efficiency and practical applicability of four mitigation measures on artisanal demersal longliners targeting European hake (Merluccius merluccius) in the western Mediterranean: night setting, tori line, weighted lines and artificial baits. We performed fifty-two pairs of experimental (with the tested mitigation measure) and control settings (without any measure), and compared their effects on seabird interactions and fish catches. In addition, we estimated the longline sink rates and the seabird access area to baited hooks in different longline configurations. Night setting reduced bycatch risk without affecting target and non-commercial fish catches. The tori line may have reduced the bycatch risk by displacing bait attacks beyond the end of the line, but at this distance shearwaters could still access to the baits and the streamers did not deter birds under calm wind conditions. Weighted lines increased sink rate, but it resulted in only a minor reduction of the seabird access window to baited hooks and led to some operational problems during the setting. Artificial baits substantially reduced commercial catches. Moreover, the seabird access to the baited hooks was influenced by the longline configuration, the setting speed and the relative position to the floats and weights. So far, night setting stands out as the best mitigation measure for reducing bycatch levels without compromising target catches in demersal longliners. Ideally, these results should be confirmed in longliners targeting species other than European hake.