Sebastián Jiménez

Seabird bycatch in the Southwest Atlantic: interaction with the Uruguayan pelagic longline fishery

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.

Marine debris ingestion by albatrosses in the southwest Atlantic Ocean

Plastics and other marine debris affect wildlife through entanglement and by ingestion. We assessed the ingestion of marine debris by seven albatross species in the southwest Atlantic by analyzing stomach contents of birds killed in fisheries. Of the 128 specimens examined, including four Diomedea species (n=78) and three Thalassarche species (n=50), 21 (16.4%) contained 1-4 debris items, mainly in the ventriculus. The most common type was plastic fragments. Debris was most frequent in Diomedea species (25.6%) and, particularly, Diomedea sanfordi (38.9%) and very rare in Thalassarche species (2.0%), presumably reflecting differences in foraging behavior or distribution. Frequency of occurrence was significantly higher in male than female Diomedea albatrosses (39.3% vs. 18.0%). Although levels of accumulated debris were relatively low overall, and unlikely to result in gut blockage, associated toxins might nevertheless represent a health risk for Diomedea albatrosses, compounding the negative impact of other human activities on these threatened species.

Interactions of long-line fishing with seabirds in the south-western Atlantic Ocean, with a focus on White-capped Albatrosses (Thalassarche steadi)

Abstract We analyse the interactions of seabirds with the Uruguayan long-line fishing fleet in the south-western Atlantic Ocean, with a focus on White-capped Albatrosses (Thalassarche (cauta) steadi). The aim of this work is to determine the species composition of the incidental by-catch of seabirds and assess the importance (in terms of abundance) of White-capped Albatross in the seabird assemblage attending this fishery. Counts of seabirds associated with fishing vessels (n =132 counts) were made during five commercial fishing trips in Uruguayan waters, and the incidental by-catch of seabirds per line-set (n = 44 line-sets) was recorded. Of 25 species of seabird recorded in association with the vessels, five were incidentally caught on long-lines. The relative frequency of occurrence of shy-type albatrosses (cauta-type) observed was 25% and their abundance was in the range 0–20 birds; most birds seen were immatures. The three specimens of shy-type albatrosses caught, along with two other specimens caught by the fleet in 2004, were identified by molecular analysis. All were confirmed to be White-capped Albatrosses, suggesting this species is the predominant one among the shy-type albatrosses occurring in the region. Before this study, there was little information on seabirds for this region of the south-western Atlantic Ocean and it was not included in the distribution of the White-capped Albatross. However, the results of this study confirm its occurrence in this region, expanding its global range and show that it is exposed to pelagic long-line fisheries in this part of the Atlantic.

Molecular analysis suggests the occurrence of Shy Albatross in the south-western Atlantic Ocean and its by-catch in longline fishing

Abstract Albatrosses are killed or injured through by-catch in longline fisheries and by collisions with warp cables in trawl fisheries. Detection of areas where albatrosses interact with fisheries is important for their conservation. Shy (Thalassarche cauta) and White-capped (T. steadi) Albatrosses are difficult to study from vessels as they are phenotypically similar. However, the two species can be identified by molecular analysis. The six-fold difference in the size of the total populations of these two species could mask by-catch of the less-abundant Shy Albatross, particularly when available sample sizes of by-catch are small. Here we document the species of a sample of 29 shy-type albatrosses killed as fisheries by-catch to confirm the observation that White-capped Albatrosses are the dominant shy-type albatross in the south-western Atlantic Ocean and exposed to the pelagic longline fishery there. Using a test based on a single nucleotide polymorphism (SNP) previously reported in the mtDNA of both species, 28 specimens were identified as White-capped Albatross. The SNP test and phylogenetic analyses suggested that the remaining bird was a Shy Albatross. Further analyses with other independent markers could confirm the identification of the latter. This result indicates the possibility that Shy Albatrosses reach the southwestern Atlantic Ocean. There is no doubt that White-capped Albatrosses, which are a regular visitor to Uruguayan waters, is the predominant shy-type albatross in the south-western Atlantic. However, a small proportion of shy-type albatrosses in this region could be Shy Albatross but further analysis is needed to confirm this.