Incidental Capture Research Articles

In situ video monitoring of by-catch interactions within commercial rock lobster (Jasus edwardsii) fishing traps

ABSTRACTThe incidental capture of non-target and undersized target species during commercial fishing operations has been identified as a major issue and ongoing challenge for fisheries management. In the Northern Zone rock lobster (Jasus edwardsii) fishery (NZRLF) of South Australia, escape gaps have been mandatory in all commercial fishing traps since 2002 to reduce non-target species (by-catch) catch rates and juvenile lobster mortality. This study used in situ video monitoring of by-catch species in traps with and without escape gaps to understand how by-catch species interact within commercial fishing traps. Twenty-two different by-catch species were observed entering commercial rock lobster traps, 20 of which were temperate reef finfish. Overall, on-board by-catch rates were significantly higher in hauled traps without escape gaps and were dominated by reef-dwelling finfish species, particularly Meuschenia hippocrepis and Notolabrus tetricus. However, in situ video monitoring within traps showed no difference in the maximum number of finfish by-catch (MaxN) in traps with or without escape gaps. We suggest that the difference in by-catch rates between hauled traps with and without escape gaps may be driven by species-specific behavioural interactions within traps prior to hauling. Overall, this study shows that the implementation of escape gaps in the NZRLF has considerably reduced fishery by-catch rates. Furthermore, the use of in situ video monitoring has provided a better understanding of by-catch behavioural interactions within traps, not previously identified in on-board sampling research, which may partly explain the mechanisms underpinning escape gap effectiveness.

Incidental capture ofMyliobatis goodeiandMyliobatis ridensin artisanal fishing in southern Brazil

This study described the myliobatids caught in artisanal beach seine fisheries in southern Brazil. Fieldwork was carried out from spring 2012 to winter 2014 in Cassino Beach (Rio Grande, Brazil). Both retained and discarded specimens were identified to species level, and sex, maturity and disc width (DW in cm) were recorded. A total 359 specimens ofMyliobatisspp. were recorded, of which 43.4% were from fishery discards, 31.5% from beach seine and 25.1% from drifting gill-net (‘lance de praia’, a fishery that has developed recently in the study area). Catches of myliobatids were higher in the spring and autumn. A total of 94Myliobatis goodei(24 males, 69 females (eight pregnant) and one unsexed), and 179Myliobatis ridenswere recorded (24 males, 148 females (17 pregnant) and seven unsexed).Myliobatis goodeiranged in size from 45.0–65.0 cm DW (males) and 43.3–115.0 cm DW (females).Myliobatis ridenswere 45.0–59.0 cm DW (males) and 41.2–98.0 cm DW (females). Both beach seine and gill-net fisheries operated in potential nursery areas for these myliobatid rays, as indicated by the proportionally high number of mature females (including pregnant females) and juveniles found in this study. The rays probably feed and give birth during the warmer seasons of the year (spring and summer) in these areas.

Incidental capture of sea turtles in the artisanal gillnet fishery in Sechura Bay, northern Peru

Gillnets are recognized globally as one of the fishing gears with the highest levels of bycatch and mortality of sea turtles. Through onboard observer monitoring from July 2013 to June 2014 we assessed the bycatch of sea turtles by an artisanal gillnet fishery operating from Sechura Bay, Peru. One hundred and four sea turtles were incidentally caught in 53 observed fishing sets. The observed species composition of bycatch was green turtle Chelonia mydas (n = 100), hawksbill Eretmochelys imbricata (n = 3) and olive ridley Lepidochelys olivacea (n = 1). Bycatch occurred in 62.3% of monitored sets, with an average of 1.96 turtles caught per set. For all sea turtles combined, 28.8% of individuals were dead and 71.2% were alive at the time of retrieval. The majority of individuals caught were classified as juveniles and sub-adults, with an average carapace length (CCL) of 57.3 ± 0.9 cm for green turtles and 40.2 ± 2.4 cm for hawksbills. The mean annual catch per unit effort (CPUE) of sea turtles was 1.11 ± 0.31 turtles km -1 12 h -1 ), but varied by seasons. These results suggest that Sechura Bay is an important developmental habitat for juvenile and sub-adult green turtles and hawksbill turtles, but one subject to intense fishing interaction pressure. The development of monitoring programs, local awareness-raising activities, and enhanced management and protection of this critical foraging area and developmental habitat is recommended.

Preliminary estimates of the abundance and fidelity of dolphins associating with a demersal trawl fishery

The incidental capture of wildlife in fishing gear presents a global conservation challenge. As a baseline to inform assessments of the impact of bycatch on bottlenose dolphins (Tursiops truncatus) interacting with an Australian trawl fishery, we conducted an aerial survey to estimate dolphin abundance across the fishery. Concurrently, we carried out boat-based dolphin photo-identification to assess short-term fidelity to foraging around trawlers, and used photographic and genetic data to infer longer-term fidelity to the fishery. We estimated abundance at ≈ 2,300 dolphins (95% CI = 1,247–4,214) over the ≈ 25,880-km2 fishery. Mark-recapture estimates yielded 226 (SE = 38.5) dolphins associating with one trawler and some individuals photographed up to seven times over 12 capture periods. Moreover, photographic and genetic re-sampling over three years confirmed that some individuals show long-term fidelity to trawler-associated foraging. Our study presents the first abundance estimate for any Australian pelagic dolphin community and documents individuals associating with trawlers over days, months and years. Without trend data or correction factors for dolphin availability, the impact of bycatch on this dolphin population’s conservation status remains unknown. These results should be taken into account by management agencies assessing the impact of fisheries-related mortality on this protected species.

Filling the gaps in sea turtle research and conservation in the region where it began: Latin America

The first documented long-term sea turtle research and conservation project in the world was officially launched in Latin America (Tortuguero, Costa Rica) in 1955. Despite the enormous advances in research and conservation in the nearly seven decades since, many questions still remain unanswered about fundamental aspects of ecology and population dynamics that hinder the conservation of sea turtles in the region. To catalyze further dissemination of information and improvement of sea turtle conservation, this Special Issue presents 10 papers solely focused on studies conducted in Latin America. This Special Issue resulted from an initiative launched to celebrate the 36th Annual Symposium on Sea Turtle Biology and Conservation, held in Peru in March 2016 -the first time this event was held in South America. The articles featured present novel results for four of the five species of sea turtles present in this region, with data collected as far back as 1971 and as recent as 2016. The studies cover diverse subjects including the nesting ecology for the most endangered populations of sea turtles in the world -the Eastern Pacific hawksbill turtle (Eretmochelys imbricata) and leatherback turtle (Dermochelys coriacea); the origins and connectivity of nesting and foraging populations of hawksbills and green turtles (Chelonia mydas); the detection of a new foraging ground for hawksbills in the Eastern Pacific; and the pervasive occurrence of incidental capture as well as illegal retention of sea turtles. The recovery of these imperiled marine reptiles relies on information to design and implement sound conservation actions; in this regard, the papers in this Special Issue are making a vital contribution, following the initial efforts launched nearly 70 years ago.

Defining risk variables causing gas embolism in loggerhead sea turtles (Caretta caretta) caught in trawls and gillnets

Incidental capture, or ‘bycatch’ in fishing gear is a major global threat to sea turtle populations. A recent study showed that underwater entrapment in fishing gear followed by rapid decompression may cause gas bubble formation within the blood stream (embolism) and tissues leading to organ injury, impairment, and even mortality in some bycaught individuals. We analyzed data from 128 capture events using logistic and ordinal regression to examine risk factors associated with gas embolism in sea turtles captured in trawls and gillnets. Likelihood of fatal decompression increases with increasing depth of gear deployment. A direct relationship was found between depth, risk and severity of embolism, which has not been previously demonstrated in any breath-hold diving species. For the trawl fishery in this study, an average trawl depth of 65 m was estimated to result in 50% mortality in by-caught turtles throughout the year. This finding is critical for a more accurate estimation of sea turtle mortality rates resulting from different fisheries and for devising efforts to avoid or minimize the harmful effects of capture.

When does hypoxia affect management performance of a fishery? A management strategy evaluation of Dungeness crab (Metacarcinus magister) fisheries in Hood Canal, Washington, USA

Management strategies for fisheries typically do not account for environmental stressors, such as hypoxia (dissolved oxygen < 2 mg·L−1). Hypoxia can lead to shoaling of organisms into normoxic habitats, enhancing catchability, which could reduce the performance of fishery management strategies. Here, we conducted a management strategy evaluation of Dungeness crab (Metacarcinus magister) fisheries in Hood Canal, Washington, a seasonally hypoxic fjord in Puget Sound. Specifically, we asked whether the current management strategy was robust to hypoxia-induced catchability changes under alternative scenarios of illegal take, incidental capture mortality, and reproductive limitation. We find that the management strategy performed well to changes in catchability when illegal and incidental fishing mortality was low and fishing did not lead to reproductive limitation. However, the performance eroded markedly (reduced long-term catch and (or) population and higher catch variation) under the alternative scenarios. These findings underscore the benefit of applying an ecosystem approach to fisheries management because it identifies potential risks to management strategies in systems subject to environmental change.

Disentangling the causes of protected-species bycatch in gillnet fisheries.

Gillnet fisheries are widely thought to pose a conservation threat to many populations of marine mammals, seabirds, and turtles. Gillnet fisheries also support a significant proportion of small-scale fishing communities worldwide. Despite a large number of studies on protected-species bycatch in recent decades, relatively few have examined the underlying causes of bycatch and fewer still have considered the issue from a multitaxon perspective. We used 3 bibliographic databases and one search engine to identify studies by year of publication and taxon. The majority of studies on the mechanisms of gillnet bycatch are not accessible through the mainstream published literature. Many are reported in technical papers, government reports, and university theses. We reviewed over 600 published and unpublished studies of bycatch in which causal or correlative factors were considered and identified therein 28 environmental, operational, technical, and behavioral factors that may be associated with high or low bycatch rates of the taxa. Of the factors considered, 11 were associated with potential bycatch reduction in 2 out of the 3 taxa, and 3 factors (water depth, mesh size, and net height) were associated with trends in bycatch rate for all 3 taxa. These findings provide a basis to guide further experimental work to test hypotheses about which factors most influence bycatch rates and to explore ways of managing fishing activities and improving gear design to minimize the incidental capture of species of conservation concern while ensuring the viability of the fisheries concerned.

Long-term trends in abundance of green sea turtles (Chelonia mydas) assessed by non-lethal capture rates in a coastal fishery

Sea turtle populations underwent severe decline in historical times, mainly through harvesting eggs and adults on nesting beaches. With the reduction of this threat in many areas, coupled with other conservation actions, some populations have demonstrated encouraging recovery, although remaining below their previous levels and undergone additional modern threats such as incidental capture in fisheries and pollution. Trends in sea turtle populations have usually been assessed through monitoring of females or nests on nesting beaches. Here we present data from a 22-year monitoring period for a juvenile green sea turtle Chelonia mydas mixed-stock in southeastern Brazil that were incidentally captured in passive non-lethal pound nets. A total of 3639 green turtles were captured in 5323 fishing days.pound−1 with mortality rate of 2%. Captures occurred in all months, but bycatch rates, excluding recapture events, were higher in September and October, probably due to the recruitment of turtles migrating from southern areas, as well as recruits from the oceanic zone. Capture rates increased by 9.2% per year in the period from 1995 to 2016, in line with increasing source populations, particularly the main source contributor at Ascension Island, but also Trindade Island (Brazil) and Aves Island (Venezuela). Mean Curved Carapace Length of green turtles was higher during austral summer/early autumn and decreased markedly in May, probably due to the small-sized individuals that recruited to the study site. We show that the incidental capture of sea turtles in non-lethal fisheries, such as Brazilian pound nets, could also provide data on trends of populations nesting in distant places, and can contribute to the assessment of population status of sea turtles within Regional Management Units throughout the Atlantic Ocean.

Incidental capture of sea turtles by industrial bottom trawl fishery in the Tropical South-western Atlantic

The five sea turtle species occurring in Brazilian waters are susceptible to threats, including incidental catches by fisheries. Studies on incidental captures in fishing gears are the main focus of several conservation actions due to high sea turtle fishery mortality worldwide. This study provides the first evaluation of incidental sea turtle catches by industrial bottom trawl fisheries operating in Brazilian waters. Four twin-trawler vessels were monitored between July 2010 and December 2011 by captains who voluntarily completed logbooks. Forty-four turtles were captured during the 1996 tows (8313 fishing hours), resulting in a catch of 5.3 ± 0.8 turtles per 1000 h per unit effort. Captured species included the loggerhead turtle (Caretta caretta, 22 individuals), olive ridley turtles (Lepidochelys olivacea, 21 individuals) and one green turtle (Chelonia mydas). Water depth was the only variable that significantly affected sea turtle captures according to Generalized Linear Models. The capture rates reported in this study ranked sixth in relation to other published studies of similar fisheries occurring worldwide. Considering the importance of this region for sea turtles, the increasing evidence of sea turtle mortality and the goals of the National Action Plan for Conservation of Sea Turtles in Brazil, it is essential to identify the main threats towards these animals and propose mitigating solutions to reduce sea turtle mortality induced by fishing activities. This study provides results that may guide future research and goals in meeting sea turtle conservation strategies.

Oceanographic determinants of ocean sunfish (Mola mola) and bluefin tuna (Thunnus orientalis) bycatch patterns in the California large mesh drift gillnet fishery

The reduction of incidental capture of non-target species in a fishery (bycatch) is a key objective of ecosystem-based fisheries management (EBFM) and critical to the conservation of many marine species. Predicting bycatch events can inform targeted ecosystem-based management approaches to reduce risk. Here, the probability of ocean sunfish (Mola mola) and bluefin tuna (Thunnus orientalis) bycatch in the California large-mesh drift gillnet fishery is predicted using a suite of remotely-sensed environmental variables. Generalized additive models (GAMs) were used to model bycatch probability for these species in 8045 observed sets from 1990 to 2011, and predictive capabilities were assessed using k-fold cross validation. Bycatch probabilities for both species were elevated in regions of cool sea surface temperatures (<17°C), likely related to seasonal upwelling dynamics in the California Current, a major eastern boundary upwelling ecosystem. Mola bycatch occurred primarily in late fall, at moderate eddy kinetic energy values (0.006–0.008m2/s2) and in areas of high seafloor rugosity. Bluefin tuna bycatch rates were higher west of the Southern California Bight, also in late fall, and appear to be associated with the seasonal upwelling frontal zone. These models can be used with near-real time satellite data by both fishers and managers for bycatch avoidance, providing a tool for more dynamic ocean management strategies.

Incidental capture of leatherback sea turtles in fixed fishing gear off Atlantic Canada

Abstract Incidental capture in commercial fishing gear is a threat to many populations of marine megafauna, including sea turtles. While research has largely focused on pelagic longline impacts on sea turtles, fixed‐gear fisheries are a significant, historically understudied source of injury and mortality. The present study assesses the interaction of endangered leatherback sea turtles (Dermochelys coriacea) with fixed‐gear fisheries in high‐latitude seasonal foraging habitat where sub‐adult and adult turtles aggregate. Records of leatherback‐fishery interactions (n = 205) were compiled from databases of publicly‐reported sea turtle sightings in Atlantic Canada (1998–2014) to identify the spatio‐temporal distribution of these events; to identify corresponding fisheries and gear types; and to describe the mechanics and outcomes of entanglements in fixed gear. Most reports came from coastal Nova Scotia (n = 136) and Newfoundland (n = 40), with reporting rates peaking in the mid‐to‐late 2000s. The majority of entanglements were reported during the summer months of July and August when leatherbacks are seasonally resident and several fisheries are active in continental shelf waters. Entanglements were most commonly reported in pot gear (e.g. snow crab, lobster, whelk) and trap nets (e.g. mackerel), reflecting extensive use of polypropylene lines distributed in the upper water column where leatherback foraging activity is concentrated. Given reporting biases and uncertainty regarding post‐release survivorship, entanglement mortalities should be considered a gross underestimate of true mortality rates. This study highlights both the importance of looking beyond pelagic longlines to evaluate leatherback interactions with fixed‐gear fisheries in high‐use continental shelf foraging habitat, and of involving the fishing industry in developing mitigation measures to reduce entanglement rates and associated turtle mortality.

Importance of Bahia Sebastian Vizcaino as a nursery area for white sharks (Carcharodon carcharias) in the Northeastern Pacific: A fishery dependent analysis

In the Northeastern Pacific, immature white sharks (Carcharodon carcharias) have been recorded in the nearshore waters of the Southern California Bight (SCB), USA, along the Mexican coast off Baja California and throughout the Gulf of California, which makes them susceptible to incidental capture by coastal fisheries. While the SCB is considered a nursery area for white sharks, records of young-of-the-year white sharks (YOY) in Bahia Sebastian Vizcaino (BSV) off central Baja California suggest that this region could also be an important white shark nursery area, but a formal evaluation of the region’s habitat function is lacking. We analyzed incidental catch records of white sharks from the US-Mexico border to BSV and evaluated whether Heupel et al.’s (2007) criteria for the identification of shark nursery areas were met for BSV. We compiled a total of 390 white shark incidental catch records between 1999 and 2013 and compared incidental catch records from the region north of Bahia Sebastian Vizcaino (NBSV; an area not considered to be a nursery ground) with those for BSV. There was a significantly higher abundance of newborns and YOY in BSV than NBSV. White shark were caught consistently throughout the year within BSV; however, the majority (70.1%) were caught between May and September. Our results are consistent with the shark nursery area criteria proposed by Heupel et al. (2007), and indicate the region between BSV to the SCB may be an important migration corridor for YOY and juvenile white sharks. Future management and conservation efforts ought to consider BSV’s nursery habitat function.

At loggerheads over international bycatch: Initial effects of a unilaterally imposed bycatch reduction policy

The Magnuson-Stevens Fishery Conservation and Management Act (MSA) is the primary law that codifies marine fisheries management in United States federal waters. The MSA was amended in 2006 with Section 610, an international provision that directs the Secretary of Commerce to unilaterally identify foreign nations engaged in the incidental capture (bycatch) of protected living marine resources (PLMRs) under specific conditions. In 2013 the United States identified Mexico for bycatch of a PLMR – the North Pacific loggerhead turtle – representing the first time a nation has been identified for bycatch under section 610. This paper evaluates the initial effects of the identification on loggerhead bycatch management efforts in Mexico and provides policy recommendations for improving the law and its implementation. In the wake of the unilateral identification, Mexico downplayed and denied the bycatch problem that their agencies had previously accepted and cancelled a bycatch research partnership between their federal fisheries science agency and U.S. researchers. Moreover, fishers invested in bycatch reduction and monitoring programs ceased to participate, jeopardizing their understanding of the problem and their co-development of bycatch solutions. However, the identification and subsequent consultation process ultimately resulted in Mexico implementing federal loggerhead bycatch regulations that are temporarily comparable with relevant U.S. measures. These regulations establish a temporary fisheries reserve (authorized for two years) that includes monitoring of bycatch, a loggerhead bycatch mortality cap, temporal and spatial restrictions on fishing gear and practices, and a closure of all finfish fisheries during the summer of 2016. As a result, turtle bycatch was likely substantially reduced in 2016, but at the cost of artisanal fishers' entire seasonal income. Policy recommendations are made, highlighting the need to: 1) better assess the socioeconomic, political, and environmental consequences associated with using the threat of trade sanctions to compel nations to reduce their bycatch; and 2) facilitate a more consistent consideration of bycatch data across nations such that the current policy does not create a disincentive for other nations to assess or report PLMR bycatch.

Grey petrel population on Campbell Island 14 years after rodent eradication

AbstractPopulations of grey petrels have declined globally due to both incidental capture in commercial fisheries and predation by introduced mammals at breeding sites. In the New Zealand region, grey petrels only breed on Campbell and Antipodes islands. Rats were successfully eradicated from Campbell Island in 2001. We assessed the spatial extent and conducted the first quantitative population estimate of the grey petrel population on Campbell Island and surrounding islets. There was an estimated c. 96 pairs (95% CI: 83, 109) of breeding grey petrels from the four colonies. Since work was conducted during the middle of the chick-rearing stage, this is an underestimate of the breeding population. The Campbell Island grey petrel breeding population remains small. Our study provides a baseline for future population estimates of grey petrels on Campbell Island.

Where is the risk? Integrating a spatial distribution model and a risk assessment to identify areas of cetacean interaction with fisheries in the northeast Atlantic

Throughout their range, marine mammals are vulnerable to incidental capture in fishing gear. Bycatch is a particularly important issue for cetaceans, which generally have lower potential rates of population growth and are thus more susceptible to the effects of bycatch mortality than other marine mammals. Spatial and temporal gaps in our knowledge of cetacean distributions can make it difficult to mitigate and manage bycatch. Here, we modelled the spatial and temporal distribution of two species of cetacean for which bycatch is known to occur; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena) and the spatial and temporal distribution of six different gear types. The models were integrated into a Productivity Susceptibility Analysis (PSA) to calculate risk in both spatial and temporal dimensions. Models showed temporal variation in spatial distribution for both species but particularly for harbour porpoise, whilst common dolphins were distributed in association with areas of high primary productivity where pelagic fish are likely to shoal. The risk assessment indicated two areas in the study region where risk from bycatch is likely to be particularly high, with gillnets being assessed as the highest risk gear type. Results should be used to guide fisheries and bycatch management through an integrated ecosystem approach, and could be used as a guide to where further observer effort should be focused. Results also provide valuable information for the designation of Marine Protected Areas for marine mammals.

Biologgers reveal post-release behavioural impairments of freshwater turtles following interactions with fishing nets

Bycatch, the incidental capture of non-target organisms, occurs in most commercial fisheries. Although immediate bycatch mortality is frequently documented in fisheries, detrimental sub-lethal effects and potential post-release mortality remain largely unknown despite the potential population-level consequences. Turtles are captured as bycatch and their populations are vulnerable to slight increases in adult mortality. In eastern Ontario, turtles are frequently captured as bycatch in a small-scale freshwater commercial fyke-net fishery and, currently, the fate of discarded turtles is unknown. We wished to determine the effect of fyke-net capture on post-release survival and behaviour in eastern musk turtles Sternotherus odoratus and painted turtles Chrysemys picta. We used biologgers equipped with tri-axial acceleration, depth and temperature sensors to document locomotor activity, vertical distribution, and temperature use of entrapped (exposed to forced submergence for 4 h) and control turtles upon release. Overall dynamic body acceleration was used as a measure of post-release activity for the first hour, first 6 h, and first 48 h. Post-release mortality was not detected. Turtles subjected to entrapment exhibited lower activity during the first 6 h following release, and their vertical distribution and temperature use differed in the first 2 h following release, but these effects disappeared after 48 h, suggesting turtles have the ability to recover. Quantifying the post-release mortality and sub-lethal effects of entrapment is important for estimating the population effects associated with bycatch.

Using Behavioral Observations to Develop Escape Devices for Freshwater Turtles Entrapped in Fishing Nets

AbstractThe drowning of freshwater turtles following incidental capture in fishing gear has the potential to cause population declines. Fyke nets can be equipped with bycatch reduction devices that enable the escape of turtles before they drown. We employed quantitative and qualitative behavioral observations (with action cameras deployed underwater) to develop a new, collapsible, escape bycatch-reduction device that mounts internally in the terminal end of a fyke net. We also used behavioral observations to identify areas of the net most used by turtles, thus revealing the most logical placement for an escape bycatch-reduction device. When turtles were introduced into modified nets, escape was rapid (mean of 12.4 min), with 100% escape for map Graptemys geographica and musk turtles Sternotherus odoratus and 94% escape for painted turtles Chrysemys picta. Our preliminary field trials indicated that modified fyke nets decreased the capture rate of turtles relative to unmodified nets. Escape devices can be used as a key component of a bycatch reduction program and be particularly effective when paired with exclusion bycatch-reduction devices. The escape device developed in this study can potentially be used in the local fishery or modified for other fisheries. The use of behavioral observation to guide the development of bycatch reduction devices may provide an extra tool for managers to increase selectivity and maintain sustainable harvests of target fish.

Four new records of stranded Kemp’s ridley turtle Lepidochelys kempii in the NW Iberian Peninsula

The critically endangered Kemp’s ridley turtle (Lepidochelys kempii) has a reduced distribution range concentrated in the Gulf of Mexico and only a few pelagic stage juveniles occasionally strand on European coasts. In the study area only three individuals have been recorded previously, most recently in 2001. Four new records of Kemp’s ridley turtle are reported from the northwestern Iberian Peninsula in 2014. All of them were juvenile with a maximum straight carapace length of 26.8 cm. Two of them were found alive, but died on the first two days at the rehabilitation centres. The largest individual stranded in November presented signs of incidental capture in fishing gears. The four records in just one year are a significant increase compared to previous data for the species in this area, and the data obtained contribute to the local knowledge on species phenology, size, distribution and threats.

Incidental capture of the short-beaked common dolphin (Delphinus delphis) in the industrial purse seine fishery in northern Chile

Incidental capture of marine mammals during fishing activities is a worldwide concern given the potentially drastic effects this can have on marine mammal populations. To assess the interaction between marine mammals and industrial fishery, an onboard observer monitored 8 purse seine fishing trips in northern Chile. He reported the incidental capture of 58 short-beaked common dolphins, 3 of which died, and one South American sea lion, which also died. The mortality rate of dolphins was 0.15 dolphins/haul and 0.3 dolphins/fishing trip, whereas for sea lions the mortality rate was 0.05 sea lions/haul and 0.125 sea lions/fishing trip. This study recorded for the first time the incidental capture of common dolphins in industrial fishery in Chile, and emphasizes the need to implement a specific monitoring plan to estimate bycatch rates of marine mammals.