Factors affecting the number and mortality of seabirds attending longline vessels in the Argentinean Economic Exclusive zone.

GANDINI, P.A.; FRERE, E.; RABUFFETTI, F. & CRUGEIRAS, J.

Montevideo, Uruguay

Congreso; Albatross Conference; 2004

Factors affecting the number and mortality of seabirds attending longline vessels in the Argentinean Economic Exclusive zone Gandini, P.A.(1) ; Frere,E.(1) ; Rabuffetti, F(2) and Crugeiras, J(3). (1) Centro de Investigaciones de Puerto Deseado (UNPA), CONICET and Wildlife Conservation Society. Avda. Prefectura s/n (9050), Puerto Deseado, Santa Cruz, Argentina. (2) Seabird Conservation Program, Aves Argentinas / BirdLife International. 25 de Mayo 749 2º “6”, (1002) Ciudad Buenos Aires, Argentina. (3) ARGENOVA S.A. Avda Prefectura s/n, Puerto Deseado, Provincia de Santa Cruz. The factors affecting numbers and the mortality rates of seabirds attending longliners fishing in Argentinean waters were studied sampling during September to November 2003. Nineteen species of seabirds and marine mammals were identified in the vicinity of the vessel. The release of offal had a positive influence on the total birds attending specially three species of albatross and four species of petrels. Six seabird species were caught on longline hooks:  White-chinned petrels, Black-browed albatrosses, Grey-headed albatross, Cape petrel, Sooty shearwater and Southern giant petrel. Most affected species during setting were Black-browed albatross (N = 223) followed by White-chinned petrel (N = 50) and only Southern-giant petrels (N = 29)  were affected during hauling.  Logistic regresion analysis indicated that moonligth (b0 = 0.041) explained most of  the “capture events”. The average by-catch rate we obtained 0.188 ± 0,26 birds/1000 hooks is four times higher than the one obtained by during Autum, winter and summer (Gandini and Frere; 0.034 b/1000 hooks). Several factors probably affect the number of birds caught, the presence of offal provided by vessels from the same side of hauling affected Southern- giant petrels (this species was no caught in previous samplings) and time of the year (spring) when birds are more abundant in the AEEZ. Results enhance the necessity of using additional mitigation measures during this time of the year specially on vessels without offal strategically deployed on the other side of hauling.