Albatrosses Following Fishing Vessels: How Badly Hooked Are They on an Easy Meal?

Abstract

Fisheries have major impacts on seabirds, both by changing food availability and by causing direct mortality of birds during trawling and longline setting. However, little is known about the nature and the spatial-temporal extent of the interactions between individual birds and vessels. By studying a system in which we had fine-scale data on bird movements and activity, and near real-time information on vessel distribution, we provide new insights on the association of a threatened albatross with fisheries. During early chick-rearing, black-browed albatrosses Thalassarche melanophris from two different colonies (separated by only 75 km) showed significant differences in the degree of association with fisheries, despite being nearly equidistant to the Falklands fishing fleet. Most foraging trips from either colony did not bring tracked individuals close to vessels, and proportionally little time and foraging effort was spent near ships. Nevertheless, a few individuals repeatedly visited fishing vessels, which may indicate they specialise on fisheries-linked food sources and so are potentially more vulnerable to bycatch. The evidence suggests that this population has little reliance on fisheries discards at a critical stage of its nesting cycle, and hence measures to limit fisheries waste on the Patagonian shelf that also reduce vessel attractiveness and the risk of incidental mortality, would be of high overall conservation benefit.

Predicting the distribution of a threatened albatross: The importance of competition, fisheries and annual variability

“…Taking-off from the sea surface is an energetically expensive exercise for albatrosses (Weimerskirch et al, 2000), and we therefore assume that landing is generally associated with foraging and is rarely conducted without purpose. Landing can also be associated with resting, but the proportion of landings with this function must be low in our study birds, which on average landed on the sea 60 times per day (Granadeiro et al, 2011). Furthermore, landing spots, even if not providing food sources, are relevant because birds can still be affected by oil spills or other sources of pollution.…”

“…No foraging activity was recorded beyond this box. The immediate vicinity (<1500 m) of the study colonies, where birds often congregate to rest, was excluded as potential foraging area (see Granadeiro et al, 2011). The maximum foraging distance from the colony recorded during this study was 603 km.…”

“…This information constitutes a complete portrait of fishing activity in Falkland waters (as there are no vessels operating there without VMS), but not in Argentinean or international waters where data were unavailable. Nevertheless, we included the available fisheries data given that in different years and colonies between 53% and 87% of the black-browed albatross time at sea was spent in sectors with complete VMS data (Granadeiro et al, 2011). During the study period, the vessels operating in the area (15 vessels in the first year and 21 in the second) were freezer/factory bottom trawlers targeting finfish.…”

“…The main target species was the Patagonian rock cod (Patagonotothen ramsayi). Fishery products include headed and gutted trunks, fillets and skate wings, with offal, heads and under-sized fish or unwanted species being discarded directly and not minced (see Granadeiro et al, 2011 for more details). Fishing effort of the Falklands fleet was estimated based on hourly positions of vessels moving at <6 knots (in 2008, values were interpolated to 1 h).…”

“…Whatever the relationship, fishing vessel distribution needs to be taken into account. Most studies so far have examined this issue at coarse spatial and temporal scales (Xavier et al, 2004;Phillips et al, 2006;Weimerskirch et al, 2010, but see Peterson et al, 2008;Votier et al, 2010;Granadeiro et al, 2011 for important exceptions) and more work is needed in this area.…”