Shark interactions in pelagic longline fisheries

Blue Ocean Institute, USA; School of Geography and Environmental Studies, University of Tasmania, Australia; 2718 Napuaa Place, Honolulu, Hawaii 96822, USA; Imperial College London, Silwood Park Campus, Manor House, Buckhurst Road, Ascot SL5 7PY, UK; 178 South Arm Drive, Wonga Beach, Queensland 4873, Australia; Pro Delphinus, Octavio Bernal 572-5, Lima 11, Peru; New England Aquarium, Central Wharf, Boston, MA 02110, USA; BirdLife South Africa, P.O. Box 52026, Waterfront, Cape Town 8002, South Africa; Dipartimento di Biologia Animale e dell’Uomo, Università di Torino, Via Accademia Albertina 13, I-10123 Torino, Italy; Environment Consultants Fiji, Box 2041, Government Buildings, Suva, Fiji; Western Pacific Regional Fishery Management Council, 1164 Bishop Suite, Suite 1400, Honolulu, HI 96813, USA; Instituto de Fomento Pesquero, Blanco 839, Valparaiso, V Region, Chile
Marine Policy (Impact Factor: 1.87). 01/2008; 32(1):1-18. DOI: 10.1016/j.marpol.2007.05.001
Source: RePEc

ABSTRACT Substantial ecological, economic and social problems result from shark interactions in pelagic longline fisheries. Improved understanding of industry attitudes and practices towards shark interactions assists with managing these problems. Information on fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers. A study of 12 pelagic longline fisheries from eight countries shows that incentives to avoid sharks vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. Shark avoidance practices are limited, including avoiding certain areas, moving when shark interaction rates are high, using fish instead of squid for bait and deeper setting. Some conventionally employed fishing gear and methods used to target non-shark species contribute to shark avoidance. Shark repellents hold promise; more research and development is needed. Development of specifically designed equipment to discard sharks could improve shark post release survival prospects, reduce gear loss and improve crew safety. With expanding exploitation of sharks for fins and meat, improved data collection, monitoring and precautionary shark management measures are needed to ensure that shark fishing mortality levels are sustainable.

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    ABSTRACT: Shark take, driven by vast demand for meat and fins, is increasing. We set out to gain insights into the impact of small-scale longline fisheries in Peru. Onboard observers were used to document catch from 145 longline fishing trips (1668 fishing days) originating from Ilo, southern Peru. Fishing effort is divided into two seasons: targeting dolphinfish (Coryphaena hippurus; December to February) and sharks (March to November). A total of 16,610 sharks were observed caught, with 11,166 identified to species level. Of these, 70.6% were blue sharks (Prionace glauca), 28.4% short-fin mako sharks (Isurus oxyrinchus), and 1% were other species (including thresher (Alopias vulpinus), hammerhead (Sphyrna zygaena), porbeagle (Lamnus nasus), and other Carcharhinidae species (Carcharhinus brachyurus, Carcharhinus falciformis, Galeorhinus galeus). Mean ± SD catch per unit effort of 33.6 ± 10.9 sharks per 1000 hooks was calculated for the shark season and 1.9 ± 3.1 sharks per 1000 hooks were caught in the dolphinfish season. An average of 83.7% of sharks caught (74.7% blue sharks; 93.3% mako sharks) were deemed sexually immature and under the legal minimum landing size, which for species exhibiting k-selected life history traits can result in susceptibility to over exploitation. As these growing fisheries operate along the entire Peruvian coast and may catch millions of sharks per annum, we conclude that their continued expansion, along with ineffective legislative approaches resulting in removal of immature individuals, has the potential to threaten the sustainability of the fishery, its target species, and ecosystem. There is a need for additional monitoring and research to inform novel management strategies for sharks while maintaining fisher livelihoods.
    Ecology and Evolution 05/2014; · 1.66 Impact Factor
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    ABSTRACT: Studies concerning marine litter have received great attention over the last several years by the scientific community mainly due to their ecological and economic impacts in marine ecosystems, from coastal waters to the deep ocean seafloor. The distribution, type and abundance of marine litter in Ormonde and Gettysburg, the two seamounts of Gorringe Bank, was analysed from photo and video imagery obtained during ROV-based surveys carried out at 60–3015 m depths during the E/V Nautilus cruise NA017. Located approximately 125 nm southwest of Portugal, Gorringe Bank lays at the crossroad between the Atlantic and the Mediterranean and is therefore characterized by an intense maritime traffic and fishing activities. The high frequency of lost or discarded fishing gear, such as cables, longlines and nets, observed on Gorringe Bank suggests an origin mostly from fishing activities, with a clear turnover in the type of litter (mostly metal, glass and to a much lesser extent, plastic) with increasing depth. Litter was more abundant at the summit of Gorringe Bank (ca. 4− 1), decreasing to less than 1− 1 at the flanks and to ca. 2− 1 at greater depths. Nevertheless, litter abundance appeared to be lower than in continental margin areas. The results presented herein are a contribution to support further actions for the conservation of vulnerable habitats on Gorringe Bank so that they can continue contributing to fisheries productivity in the surrounding region.
    Journal of Sea Research 10/2014; in press. · 1.86 Impact Factor
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    ABSTRACT: An experiment was done to quantify species-specific variation in temporal hooking rates from demersal longlines targeting various carcharhinids off south eastern Australia, with a view to reducing the incidental catches of protected species, including the scalloped hammerhead Sphyrna lewini , great hammerhead Sphyrna mokarran and grey nurse Carcharias taurus . The longline comprised a 9600 m mainline, separated into four sections (termed lines) each with 120 gangions (20 m apart) rigged with hook timers and 16/0 circle hooks baited with either sea mullet Mugil cephalus or eastern Australian salmon Arripis trutta . The mainline was deployed on each of 17 nights (between 19:30 and 23:30 h), with two lines retrieved after 7 and 14 h respectively. From a total of 8160 hooks, 246 timers were activated without hooking fish. Twenty-two species comprising 684 individuals were caught, including 52 S. lewini , 12 C. taurus , 11 S. mokarran and 1 loggerhead turtle Caretta caretta . Several environmental factors, including water temperature, moon phase and depth had mostly homogeneous positive effects on catches. The only identified variables that might be used to considerably reduce the catches of Sphyrna were soak time and/or diurnal gear retrieval, with most individuals hooked during daylight. Simply mandating shorter deployments and within nocturnal retrieval might limit exploitation, especially among juveniles (<150cm total length). For the studied fishery to approach sustainability, future research is required to investigate other gear modifications for improving size and species selectivity, and/or operational procedures for mitigating discard and escape mortalities.
    Global Ecology and Conservation. 01/2014;


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May 19, 2014