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Bigeye Tuna behavior and physiology. Their relevance to stock assessments and fishery biology.

Publiceringsår: 2005
Språk: Engelska
Sidor: 142-161
Publikation/Tidskrift/Serie: Collective Volume of Scientific Papers
Volym: 57
Nummer: 2
Dokumenttyp: Artikel i tidskrift
Förlag: International Commission for the Conservation of Atlantic Tunas (ICCAT)


Bigeye tuna (Thunnus obesus) have distinctive depth distributions and vertical movement

patterns. They remain in the uniformed temperature surface layer at night and can descend to

greater than 500 m depth at dawn. They thus mirror the vertical migrations of the small

nektonic organisms of the deep sound scattering layer and extensively exploit these as a food

resource. At their maximum depths, bigeye tuna frequently experience prolonged exposure to

ambient temperatures (.5 EC) that are up to 20EC colder than surface layer temperature, and

oxygen concentrations less than 1.5 ml O2 l-1. In contrast, skipjack tuna (Katsuwonus pelamis)

and yellowfin tuna (T. albacares) generally limit their forays to depths where water

temperatures are no more than 8EC below surface layer temperatures, and ambient oxygen

levels are above 3.5 ml O2 l-1. Understanding the vertical movements and depth distribution of

bigeye tuna, as well as the physiological abilities/tolerances and oceanographic conditions

controlling them, has been shown key for improving longline catch-per-unit effort analysis and

long-term populations assessments in the Pacific. Similar work is needed in the Atlantic.


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