Surface Longline Research Articles

Status of off-bottom mariculture in wave-exposed environments. Part 2. Comparative loading and motion of longline designs currently used in exposed commercial farms

A global inventory of extractive species mariculture in wave-exposed temperate waters shows that the longline is the technology used in more than 99% of the sites (Part 1 of this review). In this second part, I compare the static (longline at rest), quasi-static (tidal sea surface elevation, steady currents and mainline lifting operation) and dynamic (wind seas and swells) loading and motion of surface, semi-submerged and fully submerged longlines used to grow bivalves and kelp. This review is based on a hundred papers published on the subject mostly after 2010 and on simple analytical models used to illustrate the many compromises that must be made to ensure the survivability of the structure and the survival (retention), growth and quality of the cultured biomass. Surface longlines are unsuitable for fully exposed environments. To mitigate storm energy it is necessary to minimize the volume of surface buoys and submerge the mainline to the maximum depth possible. There is however a limit to minimizing the volume of surface buoys due to the uplifting of the mainline by currents. In the case of kelp, its optimal growing depth is within a few meters from the sea surface. This limitation can be partly circumvented by having the kelp float above the mainline. In the case of bivalves, mainline depth can be tens of meters below the sea surface. This comes with some disadvantages including difficulties in maintaining the delicate buoyancy balance, particularly for fully submerged longlines without legs, and reduced access to the mainline, particularly for fully submerged longlines with legs. Devices that allow autonomous or remote-controlled changes of mainline depth on a daily, occasional (husbandry and harvest operations) or seasonal basis have been tested but are not yet used commercially on longlines.

Size structure, age, and growth of the blue shark, Prionace glauca (Linnaeus, 1758) in southern Brazil.

The blue shark is a highly migratory species with a worldwide distribution, making it susceptible to multiple fishing fleets across the globe. In southern Brazil, it is an important target, comprising up to 40% of the total biomass landed by the commercial surface longline fleet. This study aims to contribute to a better understanding of how the species uses the region and to update its life-history information available for future assessments. Over five consecutive years (2018-2022) of landings and onboard monitoring, we gathered size data and vertebral samples to describe the species size composition in the region, as well as its seasonal and interannual variability and to update estimated life-history parameters. The results showed that southern Brazil is mainly inhabited by large juvenile males that arrive during winter (July-September) and stay until spring (October-December), when their frequency decreases. Small adult males are present throughout the year but in higher frequencies during summer. A small number of adult females are present with higher frequencies during spring and summer, which decreases during the austral autumn and winter. Some variability in the presence of each life stage was observed among years. The estimated life-history parameters were as follows: L∞: 255.02 cm fork length (FL), k: 0.20, L0:35.68 cm FL for males; L∞: 246.47 cm FL, k: 0.23, L0:36.77 cm FL for females; and L∞: 269.58 cm FL, k: 0.18, L0:36.19 cm FL for pooled sexes. However, the estimated values must be cautiously interpreted, as the obtained samples cannot be construed as representative of the entire harvested stock due to the lack of consistent presence of some life stages in the study region.

Potential of dynamic ocean management strategies for western Pacific leatherback sea turtle bycatch mitigation in New Zealand

Western Pacific leatherback sea turtles (Dermochelys coriacea) are a priority bycatch mitigation concern due to the projected extinction of the population before the end of the 21st century. The species regularly occurs as bycatch in gillnet and surface longline fisheries. Here, we explore the potential for dynamic ocean management in an emerging hotspot of leatherback sea turtle bycatch in the New Zealand pelagic longline fishery. We compared spatial areas of different sizes built from single oceanographic covariates as well as built from a composite risk surface developed through ensemble random forests. We found that, individually, the Okubo–Weiss parameter, sea surface temperature (SST) anomaly, SST, moon phase, and distance to the SST front were important oceanographic covariates for leatherback sea turtle bycatch. However, the spatial areas built from the composite risk surface were the most effective at discriminating sets with and without bycatch across a range of risk cutoffs. When we also considered implementation metrics of spatial area and coherence as part of performance, the area derived from the composite risk surface with a risk of interaction per set greater than 52% performed best. This spatial area was ephemeral, occurring 1 or 2 weeks each year, and localized, occurring along the north coast of East Cape in the North Island of New Zealand. The apparent presence of discrete spatial areas with elevated risk may be useful to inform future management in the area. Considering implementation metrics in defining utility was useful for identifying tradeoffs between the total size and the underlying covariates delineating a spatial area. As such, we recommend these types of metrics to be included when designing spatial bycatch mitigation strategies elsewhere.

Consumption of Post-Larval Swordfish (Xiphias gladius) by Dolphinfish (Coryphaena hippurus): New Ecological Insights into Both Species in the Tyrrhenian Sea

Knowledge of post-larval swordfish (Xiphias gladius) ecology in the world’s oceans is incomplete as they are rarely found in ichthyoplankton samplings or commercial catches and individuals are difficult to observe in the marine ecosystem. Analyses of stomach contents of apex predators can provide otherwise unobtainable ecological insights. Two well-preserved bills of post-larval swordfish were identified among the partially digested stomach contents of an adult male dolphinfish (Coryphaena hippurus) caught in the northern Tyrrhenian Sea. The lower jaw to fork lengths of the two predated swordfish were estimated at, respectively, 18 and 22 cm, corresponding to 81- and 99-day-old swordfish hatched in the 2022 spawning season. This analysis and recent information on the reproductive dynamics of swordfish in the same area reported in the literature shed light not only on the early stages of swordfish growth but also on dolphinfish ecology in the Tyrrhenian Sea. The two species share the same habitat and are both caught with commercial pelagic surface longlines. Environmental shifts associated with climate change could unpredictably modify the reproduction dynamics, growth, recruitment and distribution of both species. This knowledge is important for the sustainable management of regional fisheries.

Increased captures of the critically endangered leatherback turtle (Dermochelys coriacea) around New Zealand: the contribution of warming seas and fisher behavior

Five species of sea turtles are known to occur in New Zealand waters, with the leatherback turtle (Dermochelys coriacea) being the most frequently reported. In New Zealand all sea turtles are protected, but there are currently no fisheries bycatch mitigation measures. We describe fishery captures of leatherbacks from Ministry observer and fisher self-reported data. A generalized additive model (GAM) was then used to evaluate which factors might explain the observed year trend in captures. Between fishing years 2007–08 and 2020–21 (years starting 1 October), there were 217 captures of leatherback turtles, an annual average of 15.5. Reported captures increased substantially to 50 in 2020–21. Nearly all (97.7%) captures were reported from surface longline fisheries. Because of sparse observer coverage most captures (85.3%) were self-reported by fishers. Within the main fishery, just 9.4% of the vessels reported 94.5% of the leatherback captures, and one vessel reported 40.4% of all captures. Some non-reporting of captures seems likely. The GAM estimated a higher probability of capture with increasing SST from a constant-over-time spatial pattern of monthly sea surface temperature, and predicted the increase in captures in 2020–21. Much of the increase in bycatch could therefore be explained by the fleet moving into warmer areas where the probability of leatherback capture was higher. Capture mitigation measures could include restricting fishing in turtle ‘hotspot’ times and areas. New Zealand waters should be recognized as an important seasonal foraging ground for leatherback turtles where capture mitigation measures are necessary.

Karakteristik Sosial Ekonomi Nelayan Pemanfaat Hiu Tikus (Alopiidae) di Manggis, Karangasem, Bali

Thresher sharks are known to have substantial economic value. They are caught globally as target and as bycatch in tuna fisheries. Due to their declining population, they are listed as an appendix II species on CITES, therefore any form of trade and fisheries related to the species have been nationally and internationally regulated. However, information on thresher shark fisheries in Bali is still limited. This study aims to socio-economically characterize thresher shark fishermen in Manggis, Karangasem. The research was conducted in August 2020 – October 2020 by interviewing 53 out of 119 recorded shark fishermen using a structured questionnaire. Shark fishermen use surface longlines to catch thresher sharks (Alopiidae) in between 3 areas, North Nusa Penida-Karangasem, east Nusa Penida and Bangko-Bangko. The fishermen catch sharks exclusively during the months of June-October and catch tuna the rest of the year. Operational costs for 1 boat ranges between Rp 121.000 – Rp 250.000 during 1 round trip. The income generated from shark fishing each trip averages to about Rp 627.714 per boat. Prior to the Covid-19 pandemic, some of the fishermen work jobs in the tourism sector. However, due to the pandemic’s impact on tourism, they have no choice but to be fishermen full time. Although thresher shark fisheries in Manggis are generally small scale, conservation and management strategies need to be implemented to ensure sustainable use of shark resources.

Interactions Between Cetaceans and Small-scale Fisheries Around the Central Mediterranean Maltese islands

Cetacean depredation poses threats to both the socioeconomic viability of fisheries as well as species conservation. This study is based in the Maltese islands where the fishing sector has always been of a small-scale nature, with 93% of vessels being under 12 metres in length. Maltese fishers engage in small-scale fishing utilizing a variety of artisanal fishing gear, including surface longlines, which are mainly used to target swordfish and tuna; bottom-longlines; trammel nets and entangling nets, which are used to target groupers, various species of bream, red snappers and red porgies; and pots and traps which are generally used to captured octopus and bogue. This study, which aimed to analyse fishers perception with respect to interaction occurrence between small-scale fisheries and cetaceans in Maltese waters, found that fishers claim that dolphin presence has increased in the past five years, particularly in the vicinity of bluefin tuna, seabream, and seabass fish farms locations. While the use of trammel nets remains by far the most popular gear type employed by Maltese fishers, this study showed that around 33% of the fishing gear deployed in the past year suffered damages. It is therefore essential that proper monitoring is carried out in order to assess the factors that drive the interactions and the impact of dolphin depredation on the fishing sector. New prevention and mitigation measures are proposed. This study provides first-hand insights which will aid in the execution of local fisheries management plans and, subsequently, ecosystem-based fisheries management.

First insights into the movements and vertical habitat use of blue marlin (Makaira nigricans) in the eastern North Atlantic

BackgroundThe blue marlin (Makaira nigricans) is a vulnerable migratory fish inhabiting tropical and subtropical pelagic waters of the Atlantic, Pacific and Indian Oceans. The biology and spatial ecology of the species in the eastern North Atlantic is poorly understood, despite being exploited in the region by recreational and commercial fisheries. Here, we present results of the first study to use pop-up satellite archival tags to track blue marlin off Madeira, Portugal (n = 3) and obtain insights into the movements and habitat use of the species within the eastern North Atlantic.ResultsBlue marlin were tracked for 24 to 83 days, moving from Madeira to pelagic waters off the Canary Islands, Cape Verde Islands, as well as along the continental shelf brake of Europe and Africa. Blue marlin spent 71% of their time in the upper 5 m and 89% in the upper 50 m, though all individuals dived to depths over 200 m (maximum: 336 m). Temperature at depth ranged from 12 to 28.6 °C, but the greatest proportion of time was spent in waters between 20 and 26 °C. Detailed depth and temperature time-series data were obtained from a tag recovered eight years later. These data show clear diel differences in depth use, involving consistent use of the surface at night and deeper dive activity during the day, predominately to depths greater than 50 m.ConclusionsThe highly migratory patterns of this vulnerable species in the eastern North Atlantic highlights the need for both local and international conservation measures. Depth-use patterns, particularly the high usage of the upper 5 m of the water column, make them susceptible to surface longline fisheries.

Seabird bycatch risk correlates with body size, and relatively larger skulls, bills, wings and sensory structures

Many animals have sensory biases towards signals or cues that typically provide some fitness benefit. Sensory traps occur when other species or anthropogenic sources produce similar signals or cues but responding is no longer adaptive and can impose significant costs or even death. Bycatch of seabirds by fishing boats has devastating impacts, causing hundreds of thousands of seabird deaths per annum. Here, we explore whether fishing vessels are acting as a sensory trap, inadvertently targeting seabirds with certain life-history traits or larger skeletal or sensory structures. We surveyed the literature to compare seabird order, diet, wingspan, body size, and nesting preference (surface or burrow) of 70 seabirds with varying numbers of reported bycatch in one of the world’s most important regions for seabird breeding, in northern Aotearoa New Zealand. We also examined the skeletal and sensory measurements of six seabirds that co-occur spatially in this region, but have different numbers of reported bycatch and indices of bycatch risk. The literature survey revealed that the Charadriiformes and the Sphenisciformes were the most vulnerable groups (p = 0.01), especially to surface longline fisheries. There were no correlations with diet and foraging behaviour, but surface nesting seabirds and those with larger bodies and wingspans were at a greater risk of becoming bycatch. Skeletal measurements show that species with higher bycatch also have relatively larger skulls, bills and wings, eye sockets and nostrils (relative to body size) (p < 0.05). This suggests that having a larger overall body size and longer protruding body parts is a primary risk factor, but that species with relatively more sensitive sensory systems likely have even more acute bycatch risk. Considering fishing vessels as sensory traps provides a context to explore the multiple interconnecting factors of sensory sensitivity, sensory bias, behaviour and morphology.

Reproductive biology of Isurus oxyrinchus captured by the south Brazilian surface longline commercial fleet in the Southwest Atlantic Ocean, with data on CPUE and size distribution by sex

Reproductive biology of <i>Isurus oxyrinchus</i> captured by the south Brazilian surface longline commercial fleet in the Southwest Atlantic Ocean, with data on CPUE and size distribution by sex

Sea turtle bycatch by different types of fisheries in southern Spain

The bycatch of sea turtles by large-scale fisheries is receiving an increasing attention in recent years due to the high impact it causes on these endangered species. This issue was evaluated in southern Spanish waters that harbor an important feeding ground of loggerhead and leatherback turtles, including the endangered Eastern Atlantic loggerhead population. To quantify the impact that different fisheries represents to sea turtles, 272 fishermen answered to detailed illustrated questionnaires in all the main ports of Andalusia and Murcia (Spain) during 2014. This study has updated the knowledge of turtle bycatch in the southwestern Mediterranean revealing a widespread impact of fisheries on sea turtles. Fishermen recognized an annual catch of 2.3 turtles per boat. Considering the census of operative large-scale fishing boats in the study area (1182), more than 2840 sea turtles could be bycaught per year in that area. Most captures (96.2%) were produced during the summer. These fisherman answers suggest a severe impact of most legal fisheries (surface longline, purse seine, trawling and small-scale fisheries) on loggerhead feeding grounds in the southwestern Mediterranean. Fishermen suggested that drift fishing conducted by foreign or illegal fishermen and almadrabas are also causing a significant bycatch of turtles. Several measures such as reviewing compliance of current fishing and environmental regulations, modifying fishing techniques to reduce turtle bycatch, facilitating the rescue and handle of wound turtles and their transport to the port for recovery, and recognizing the efforts of anglers to perform a more sustainable fishing, are recommended to mitigate this impact.

Involving stakeholders in the evaluation of management strategies for shortfin mako (Isurus oxyrinchus) and blue shark (Prionace glauca) in the Spanish longline fisheries operating in the Atlantic Ocean

Shortfin mako (Isurus oxyrinchus) and blue shark (Prionace glauca) are a relevant bycatch in the Spanish surface longline fisheries that operate in the Atlantic Ocean. Concern has been raised after the 2017 and 2019 shortfin mako evaluations for the Northern Atlantic stock. It stated the population being overfished and suffering from overfishing. Also blue shark is subject to high extraction rates in the Atlantic Ocean. Few data and uncertainty in assessment results suggest that further management strategies could be taken into account for both species. This study evaluated different fisheries management strategies for shortfin mako and blue shark in the Atlantic Ocean from the stakeholders' perspective. Personal interviews were conducted with Spanish fishermen and surveys were sent to scientists and non-governmental organizations (NGOs). Local Ecological Knowledge was considered to be useful as fishermen possess unique expertise based on their continued interaction with the species and environment. Interviews allowed understanding the fishermen's perception on variations of stock abundance, distribution patterns, size of capture and seasonal fluctuations for both species. SWOT (Strength, Weaknesses, Opportunities and Threats)-analysis was used to study the different management measures. Main management strategies proposed by all stakeholders to reduce the bycatch of both species were spatial-temporal closure, minimum size and quotas. The Sole Bank was suggested as a temporarily closed area to protect blue shark juveniles during the summer months. The participation of stakeholders enriched the knowledge available and provided a broader data set now available for decision makers in the corresponding regional fisheries management organization (RFMOs).

North Atlantic Oscillation affects dolphinfish catch and bycatch in the Western Mediterranean Sea

Dolphinfish is targeted by small-scale fisheries and is part of the bycatch of drifting surface longline targeting tuna and swordfish in the Mediterranean Sea. The main aim of the present study is to understand the effect of the North Atlantic Oscillation (NAO) on the dolphinfish bycatch of the Spanish longline fisheries in the Western Mediterranean Sea and, likewise on the catch of small-scale fisheries targeting dolphinfish associated to anchored fish aggregating devices (aFADs) in waters of the Balearic Islands. Understanding the impact of climatic effects is crucial to improve the assessment and management of the Mediterranean dolphinfish. In longline fisheries, the negative phases of the NAO with a short time lag increase the dolphinfish bycatch probability, with a CPUE higher than the mean of the study period. However, with a long time lag, the positive phases increase the dolphinfish bycatch probability, with a CPUE higher than the mean of the study period. On the other hand, when examining the Mallorca aFADs fisheries, the negative phases of the NAO with a long time lag increased the probability of catching fish with higher landings than the observed mean of the study period. The results suggest strong connections between the prevailing climate conditions in March and April and dolphinfish catches during the fishing season of this species in September and October.

Multiple-threats analysis for loggerhead sea turtles in the southwest Atlantic Ocean

Priority-setting approaches for widely distributed and long-lived species can be challenging. This is especially true for sea turtles, which are species of conservation concern. The aim of this study was to conduct a detailed analysis of threats to identify, quantify and prioritize the main impacts to the loggerhead Caretta caretta population in the southwest Atlantic (SWA) region. A matrix of relative threats was constructed. Threats were identified and classified for 8 different life stages (nesting females, eggs, hatchlings, swim-frenzy transitional stage, juveniles-neritic, juveniles-oceanic, adults-neritic, adults-oceanic) and for 3 ecosystems inhabited by sea turtles (terrestrial, neritic and oceanic). Results indicated that fisheries bycatch represents a major threat for loggerheads in the SWA. The trawl fishery was identified as the main source of mortality for neritic juvenile and adult turtles, whereas juveniles in oceanic areas are mostly impacted by surface longlines. In terrestrial environments, eggs and hatchlings are mainly affected by habitat alteration and by native and exotic predators. Loggerheads have shown a positive nesting trend at their main nesting beaches in the SWA, probably due to long-term conservation efforts to reduce mortality of the different life stages within the terrestrial zone. However, the high mortality rates of juveniles and sub-adults documented at some known foraging grounds represent a reason for concern, as this may affect the overall population trend in the future. This threat analysis provides a tool to review the goals of national action plans, prioritize actions and optimize the allocation of management resources.

Influência da Variabilidade Meteo-Oceanográfica no Oceano Atlântico Sudoeste sobre a Pesca Tubarão-Azul, Prionace glauca (Linnaeus, 1758)

O Brasil possui cerca de 8.500 km de linha de litoral e um número razoável de ilhas, totalizando uma área de aproximadamente 3,5 milhões de km² de Zona Econômica Exclusiva (ZEE), que se estendo desde o Cabo Orange (5 ºN) até o Chuí (34 ºS). A pesca com espinhel superfície é uma modalidade pesqueira mundialmente utilizada em oceano aberto. Atualmente os principais portos que abrigam a frota espinheleira na região Sudeste em Santos (SP) e Itaipava (ES) e na região Sul a localidade de Itajaí e Navegantes (SC). O tubarão-azul, Prionace glauca (Linnaeus, 1758), é uma das espécies de elasmobrânquios pelágicos, mais capturadas pela frota de espinhel de superfície. O tubarão-azul, é considerado o abundante dentre os grandes tubarões pelágicos presentes no Oceano Atlântico. É uma espécie oceânica, altamente migratória, apresenta distribuição global, entre as latitudes de 60°N e 50°S, ocorrendo em águas tropicais e temperadas, predominantemente naquelas com temperaturas entre 12°C - 20°C. A presente estudo visa avaliar a influência da variabilidade meteo-oceanográfica no oceano atlântico sudoeste sobre a população de tubarão-azul, Prionace glauca (Linnaeus, 1758), capturada pela frota industrial no período de 1994-2018 na modalidade de espinhel de superfície. Para a elaboração do estudo serão analisados ​​os dados de desembarques mensais da frota espinheleira da região do Atlântico Sudoeste entre os anos 1994 - 2018.

A possible new spawning area for Atlantic bluefin tuna (Thunnus thynnus): the first histologic evidence of reproductive activity in the southern Gulf of Mexico.

The number of studies of reproductive biology for Atlantic bluefin tuna carried out in the Gulf of Mexico is significantly lower than those undertaken in the Mediterranean Sea. Four spawning areas have been found for the eastern Atlantic bluefin tuna stock in the Mediterranean Sea, so it is not implausible that there is more than one spawning area in the Gulf of Mexico for the western Atlantic bluefin tuna stock. The individuals used in this study were caught as bycatch by the Mexican surface longline fleet between January and April 2015. A total of 63 individuals ranging between 192 and 293 cm LF (mean = 238 ± 22.52 cm) were measured. Gonads from 46 fish (31 females and 15 males) were collected for histological examination. All the individuals were classified as mature; 25 were reproductively active (in spawning capable and spawning stages). The histological analysis indicates spawning activity in Mexican waters (the southern Gulf of Mexico). Spawning occurred in March and April, when the sea surface temperature was 25.57 °C ± 0.69 in March and 27.03 °C ± 0.69 in April. Information on the location of the spawning areas is necessary for a correct management of species. The present study provides the first histological evidence of reproductive activity in Mexican waters, and indicates a wider spawning area, beyond just the northern zone, potentially encompassing the entire Gulf of Mexico.

Hookpod-mini: a smaller potential solution to mitigate seabird bycatch in pelagic longline fisheries

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 39:1-8 (2019) - DOI: https://doi.org/10.3354/esr00953 ESR Special: Marine vertebrate bycatch: problems and solutions Hookpod-mini: a smaller potential solution to mitigate seabird bycatch in pelagic longline fisheries David Goad1,*, Igor Debski2, Joanne Potts3 1Vita Maris Limited, Papamoa, 3118, New Zealand 2Department of Conservation, Wellington, 6011, New Zealand 3The Analytical Edge Statistical Consulting, Tasmania, 7052, Australia *Corresponding author: goad.dave@gmail.com ABSTRACT: Hookpods are an emerging technology designed to reduce seabird bycatch in pelagic longline fisheries. Hookpod-minis were trialled in the New Zealand surface longline fishery in 2016-2017 during short-term experimental (20 longline sets) and longer-term operational (110 longline sets) trials. Two sets of experimental trials were conducted. The first compared snoods fitted with Hookpod-minis with a tori line to unweighted snoods with a tori line. The second compared snoods fitted with Hookpod-minis as a stand-alone mitigation measure to weighted snoods in combination with a tori line. All gear, across both trials, was set at night. Operational trials compared snoods fitted with Hookpod-minis and tori lines to standard mitigation requirements for unweighted gear and tori lines, with all gear set at night. Both sets of trials demonstrated that Hookpod-minis fit easily into fishing operations, do not reduce target species catch rate, and may reduce seabird bycatch to low levels. Our findings suggest that Hookpod-minis as a stand-alone mitigation measure are as effective, or more effective, than current bycatch mitigation measures including the combination of line weighting and tori lines. KEY WORDS: Mitigation · Pelagic longline · Seabird bycatch · Tori line Full text in pdf format NextCite this article as: Goad D, Debski I, Potts J (2019) Hookpod-mini: a smaller potential solution to mitigate seabird bycatch in pelagic longline fisheries. Endang Species Res 39:1-8. https://doi.org/10.3354/esr00953 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 39. Online publication date: May 02, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Fishery strategy affects the loggerhead sea turtle mortality trend due to the longline bycatch

The western Mediterranean Sea is an important fishing ground for the Spanish surface longline fleet targeting swordfish, bluefin tuna, and albacore. Spanish Mediterranean waters, including contiguous international waters, are important feeding areas for thousands of juvenile and sub-adult loggerhead turtles. Due to the spatial overlap in fishing grounds between different longline métiers and loggerhead distribution, in the early 2000s, an estimated minimum of 60,000 loggerhead sea turtles were caught as bycatch in Mediterranean longline fisheries, including all countries operating in the area. The Spanish surface longline fleet is continually introducing technological and strategic innovations to improve the economic benefits of the fishery. These innovations lead to high variability in fishing gear and operational strategies from year to year.During the study period, there was a change in the specific contribution of each métier to total effort. Thus, since 2000 to the present, the Spanish traditional home-base surface longline targeting swordfish has been gradually modified or in other cases replaced by other métiers, and in most vessels it has been replaced by a new deeper semipelagic longline targeting the same species; which has led to a dramatic decrease in sea turtle mortality. The main result of this study is that loggerhead turtle post-release mortality due to the bycatch by the Spanish surface fleets using different longline métiers has significantly decreased during the last 8 years of the study period. We estimate an average post-release mortality around 1800 loggerheads sea turtles per year. The observed decrease in turtle mortality was an indirect effect of the introduction of changes in technology and fishing strategies in the fleets in the attempt to improve their economic objectives.

Depredation in pelagic surface longlines in the Atlantic and Indian Oceans

Depredation in pelagic surface longlines in the Atlantic and Indian Oceans

Portuguese fisheries in seamounts of Madeira-Tore (NE Atlantic)

The activity of the Portuguese fishing fleet operating near seamounts of the Madeira Tore geologic complex was analyzed. The main objective is to identify the different fisheries taking place in the area, characterize the spatial patterns of vessels activity and estimate the fishing intensity, thus contributing to better inform management decisions. Vessel Monitoring System (VMS) and e-logbook data for the period 2012–2014 were used. The combined analysis of these data allowed the identification of fishing events and the estimation of the fishing intensity by gear type, as well as the characterization of general patterns relating to fishing operations. A total of 47 vessels displayed fishing activity in the studied area, mainly longliners based either on the mainland or the Madeira archipelago, visiting different seamounts in fishing trips lasting two to three weeks, and a few pole and line bait boats. Bottom and pelagic longlining alternate throughout the year, the former mostly in spring and summer, targeting the wreckfish Polyprion americanus and the European conger, Conger conger, while the latter is carried out in autumn and winter using a surface longline targeting the swordfish Xiphias gladius and a drifting longline set deeper in the water column, targeting the black scabbard fish Aphanopus carbo. A global evaluation of the fishing intensity and estimation of fishing impact in this area calls for the availability of VMS data, e-logbooks and landing declarations from non-Portuguese fleets, making monitoring in these areas a top priority to assess the sustainability of human activities.