Experimental fishing with an “umbrella-and-stones” system to reduce interactions of sperm whales (Physeter macrocephalus) and seabirds with bottom-set longlines for Patagonian toothfish (Dissostichus eleginoides) in the Southwest Atlantic

Depredation, i.e. the damage or removal, of Patagonian toothfish (Dissostichus eleginoides) from longlines by sperm whales (Physeter macrocephalus) can cause considerable economic loss for Spanish fishing vessels in the Southwest Atlantic. The fishery also suffers high bycatch rates of seabirds. The...

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Bibliographic Details
Published in:ICES Journal of Marine Science
Main Authors: Goetz, S. (Sabine), Laporta, M. (Martín), Portela, J. (Julio), Santos, M.B. (María Begoña), Pierce, G.J. (Graham John)
Format: Article in Journal/Newspaper
Language:English
Published: Centro Oceanográfico de Vigo 2011
Subjects:
depredation
longline
Patagonian toothfish
sperm whale
umbrella system
Patagonian Toothfish
Physeter macrocephalus
Sperm whale
Online Access:http://hdl.handle.net/10508/814
https://doi.org/10.1093/icesjms/fsq161
Description
Summary:Depredation, i.e. the damage or removal, of Patagonian toothfish (Dissostichus eleginoides) from longlines by sperm whales (Physeter macrocephalus) can cause considerable economic loss for Spanish fishing vessels in the Southwest Atlantic. The fishery also suffers high bycatch rates of seabirds. The main goal of the study was to assess the extent of depredation and seabird bycatch and to test the potential of the so-called “umbrella” system, coupled with attached stones for faster sinking, for minimizing both. Moreover, we investigated the relationships between sightings of sperm whales, depredation, catches, and environmental variables using generalized additive modelling. Data were collected during 297 hauls on a longliner in 2007/2008 in international waters of the Southwest Atlantic. Sperm whales were sighted during 35% of the hauls, always during gear retrieval, and their presence was positively related to fish damage. The overall depredation rate (0.44% of the total catch) was low, but is assumed to be underestimated because sperm whales were suspected of also taking fish without leaving visual evidence. The “umbrella-and-stones” system was highly effective in preventing bycatch and appeared to restrict depredation, but significantly reduced the catches. The results demonstrate that there is still some way to go to solve the problem of depredation.

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