Assessing the impact of the pelagic longline fishery on albatrosses and petrels in the southwest Atlantic (original) (raw)
Related papers
Estimates of seabird incidental catch by pelagic longline fisheries in the South Atlantic Ocean
Animal Conservation, 2013
The mortality of seabirds in fisheries has had a serious negative impact on many seabird populations, yet the extent of fishery-derived seabird mortality in pelagic longline fisheries, remains poorly understood. In this study, we analyze fishing effort and catch data of the Taiwanese distant-water longline tuna fleet -the largest fleet in the Atlantic Ocean. These data collected by fishery observers over a 5-year span include 61 trips involving 6181 observed sets of over 20 million hooks, where 198 seabirds were caught (23 of which were released alive). Most birds were caught in the South Atlantic, with estimated seabird bycatch rates ranging from 0.026 birds per thousand hooks in the southwest Atlantic to 0.063 birds per thousand hooks in the southeast Atlantic. Black-browed, Atlantic yellow-nosed, and wandering albatrosses, as well as spectacled and southern giant petrels, were the most frequently caught species. Seabird bycatch hotspots were identified at 20°-40°S/10°W-15°E and 35°-45°S/45°-55°W. In the South Atlantic Ocean, generalized additive models indicated that fishing location and the number of birds sighted significantly influenced seabird bycatch rates. Extrapolating these spatially and temporally explicit seabird bycatch rates to the fishing effort data of other distant-water longline fleets and extrapolating the bycatch rates reported in the literature to the reported fishing effort of coastal nation fleets, we estimate the total seabird incidental mortality from pelagic longline fishing in the southern Atlantic Ocean to be between 3446 and 6083 birds per year from 2004 to 2008. These findings support proposals calling for the required use of best-practice mitigation measures by all pelagic longline vessels operating in seabird bycatch hotspots in the South Atlantic Ocean. International cooperation on research and data sharing is critical to ensure the sustainability of seabird populations and fisheries. Seabird bycatch in the South Atlantic Ocean Y-M. Yeh et al. Y-M. Yeh et al.
Seabird bycatch in the Southwest Atlantic: interaction with the Uruguayan pelagic longline fishery
Polar Biology, 2009
This paper analyzes the spatiotemporal variation and the causes of seabird bycatch by the Uruguayan pelagic longline fleet in a region of the Atlantic Ocean where the world’s highest historical rates of seabird bycatch were recorded. The study is based on data obtained by the Uruguayan Observers Program in 29 trips, conducted from 1998 to 2004, totalling about 648,000 hooks. The bird capture per unit of effort (BCPUE) for the studied period was 0.42 birds/1,000 hooks. The highest BCPUE values were recorded in the period May–November. Three zones were identified, with BCPUEs of 2.50 birds/1,000 hooks (very high); 0.78 birds/1,000 hooks (high) and 0.04 birds/1,000 hooks (low). Though these BCPUE values are lower than those historically reported, some are still high in global terms. Night setting was found to be effective in reducing seabird bycatch, but it is necessary to implement additional measures as seabirds have access to bait also by night, especially during the more luminous moon phases.
2008
The Southwestern Atlantic Ocean is an important foraging ground for several albatrosses and petrels during breeding and non-breeding seasons. In this region they meet longline fishing fleets, currently the main threat for this group of seabirds. Significant overlap between longline fishery and seabird distribution in southern Brazil, especially during winter, is the major cause for concern. Here we present information on bycatch rates of seabirds in the Brazilian domestic pelagic longline fleet from 2001 to 2007 on the Exclusive Economic Zone (EEZ) and adjacent international waters of the Southwestern Atlantic Ocean and a review of bycatch rates reported for the area. Overall seabird capture rates obtained during 63 cruises (656 sets and 788,446 hooks) was 0.229 birds/1000 hooks, varying from zero to 0.542 birds/1000 according to season. Capture rates were higher between June and November (cold season) and affected mainly black-browed albatross Thalassarche melanophris (55% of birds captured), white-chinned petrel Procellaria aequinoctialis, spectacled petrel Procellaria conspicillata and Atlantic yellow-nosed albatross Thalassarche chlororhynchos. Capture rates previously reported in SW Atlantic varied from 0 to 5.03 birds/1000 hooks, with those based on logbooks or fishermen interview tending to underestimate capture rates, whereas those based on small number of hooks and/or seasonally biased tend to overestimated in both pelagic and demersal longline fisheries. Representative capture rates for the pelagic longline are in the range of 0.2 to 0.4 birds/1000 hooks. Detailed studies with large sample sizes are required for a comprehensive approach of causes determining the incidental capture.
Risk assessment and relative impact of Uruguayan pelagic longliners on seabirds
Aquatic Living Resources, 2012
Bycatch in longline fisheries is considered one of the main threats for the conservation of albatrosses and petrels worldwide. However, the relative impact of fisheries on all the affected populations or species still remains poorly understood. This paper applied a Productivity and Susceptibility Analysis (PSA) and the concept of "Potential Biological Removal Level" (PBR) to assess the relative impact caused by the Uruguayan pelagic longline fishery on several populations. This two-step approach allowed us to obtain an objective view of the relative impact of the Uruguayan pelagic longline fleet on most of the populations or species of albatrosses and petrels with high association with this fishery. Of fifteen species considered, fourteen were finally assessed and a ranking of risk derived. The concept of PBR was applied to the nine most at-risk species. The impact of fishing on populations could not be straightforwardly inferred from their bycatch rates. Results indicate that large albatrosses (Diomedea spp.) and Thalassarche chlororhynchos are more affected than some of the main species caught by the fishery (i.e. Thalassarche melanophrys and Procellaria aequinoctialis). Diomedea exulans from South Georgia is likely to be the population most affected by the Uruguayan fleet. This work should be seen as a case study of the fisheries operating in the southwestern Atlantic. The Uruguayan fleet within its operation area was responsible for only the 4.3% to 12.5% of the total annual effort deployed by the different fleets during 2004−2008. The combined impact of these fleets could be sufficiently high to account for many of the observed declines in the populations of D. exulans, D. dabbenena and T. chlororhynchos. However, the seabird bycatch numbers for most of the pelagic longline fleets that operate in the southwest Atlantic remain unknown. Applying mitigation measures to reduce the impact of pelagic longline fleets operating in this region should be considered a high priority.
ESTIMATING FISHERY BYCATCH AND EFFECTS ON A VULNERABLE SEABIRD POPULATION
Ecological Applications, 2003
Pelagic longline fisheries worldwide incidentally take long-lived seabird species. This mortality has led to fisheries restrictions to protect seabirds at risk, including Wandering (Diomedea exulans) and Amsterdam Albatross (D. amsterdamensis) in the South Pacific and Spectacled Petrel (Procellaria conspicillata) in the South Atlantic. Because pelagic longline fisheries involve multinational fleets operating in vast ocean regions, assessing total bycatch levels for a seabird is challenging. Here we present a case study of quantifying bycatch from a basin-wide pelagic longline fishery and assessing the populationlevel impact on a vulnerable seabird, the Black-footed Albatross (Phoebastria nigripes) in the central North Pacific. We develop an assessment method that uses observer data to estimate bycatch for one fleet and then uses scenario analysis to estimate bycatch for remaining fleets. Our method generates a bounded estimate of bycatch within an ocean region, ranging from the worst-case to the best-case bycatch scenario. We find that Blackfooted Albatross mortality across all fleets in the central North Pacific may total as much as 10 000 individuals/yr. At this level of mortality, population declines are likely. However, even at the best-case bycatch estimate (5200 individuals/yr), population declines may occur over the next three generations (60 years). Although this analysis requires extensive estimation and extrapolation from existing data, it is critical to provide fisheries managers with bounded estimates of likely population-level effects of current fishing activity.
An assessment of seabird–fishery interactions in the Atlantic Ocean
ICES Journal of Marine Science. 68: 1628 - 1637., 2011
Currently, 17 of 22 albatross species are listed as Vulnerable, Endangered, or Critically endangered by the International Union for the Conservation of Nature (IUCN). Incidental mortality in fisheries is by far the most widespread cause of the population declines observed for these and other closely related species. In 2006, the International Commission for the Conservation of Atlantic Tunas (ICCAT) requested an assessment of the threat from their fisheries to all seabirds that breed or forage within their jurisdiction. Methods were developed to assess the potential consequences of fishing for more than 60 populations of seabird. The assessment framework involved the identification of at-risk populations, overlap analyses, estimation of total bycatch, and an evaluation of the impact of the bycatch on key selected populations for which there were sufficient data on bird distribution and demography. These were the wandering and black-browed albatrosses of South Georgia and the Atlantic yellow-nosed and Tristan albatrosses of Gough Island. Summary results from the seabird assessment are presented, revealing that ICCAT longline fisheries catch substantial numbers of seabirds, with potentially significant conservation implications. If this mortality is not reduced, the numbers of breeding birds in some populations will continue to decline, threatening their long-term viability.
OVERVIEW OF SEABIRD BYCATCH BY BRAZILIAN FISHERIES IN THE SOUTH
The impact of fisheries bycatch on seabirds around the world is currently the focus of considerable international concern. In Brazilian waters there are eight fisheries that affect seabirds, according to the National Plan of Action for the Conservation of Albatrosses and Petrels (NPOA-Seabirds Brazil). Capture rates obtained by observers during 40 cruises (473 sets and 499,978 hooks) in the pelagic longline fisheries in south and southeastern areas, between November 2000 and December 2005 were 0.102 birds/1000 hooks. The leased fleet (based in northern and northeast ports) that fished along most of the Brazilian coast and in adjacent international waters was sampled by ProBordo observers (Brazilian National Observer Program). Seabird capture in this fishery during 2005 was 68 specimens. The most commonly captured species in both the leased and domestic fleets were the black-browed (Thalassarche melanophris) and Atlantic yellow-nosed (T. chlororhynchos) albatrosses, whitechinned (Procellaria aequinoctialis), spectacled (P. conspicillata) petrels and the great shearwater (Puffinus gravis). Other fisheries have demonstrated that fishing is an important mortality factor for seabirds and incidental capture rates must be evaluated. The assessment of seabird by-catch by fleets based in Brazilian ports must continue in order to support the implementation of mitigation measures.
Endangered Species Research, 2008
Appendix 1. Summary of studies reporting capture rates of seabirds (birds per 1000 hooks) in demersal and pelagic longline fisheries in the southwestern Atlantic Ocean from 1991 to 2008. -: data not provided. Range of capture rates was reported in several ways, e.g. between sets, cruises, season or areas. Namorado = Pseudopercis numida, tilefish = Lopholatilus villarii, groupers = Epinephelus spp., toothfish = Dissostichus eleginoides, hake = Merluccius hubbsii, kingclip = Genypterus blacodes, tunas = Thunnus spp., swordfish = Xiphias gladius, sharks = several species, including Prionace glauca, Sphyrna spp., Carcharhinus spp., and Alopias spp.), wreckfish = Polyprion americanus, yellownosed skate = Dipturus chilensis, dolphinfish = Coryphaena hippurus Longline type Location Mean capture rate Range capture rate Year(s)