On the relationship between El Nino Southern oscillation and South Pacificalbacore

The influence of El Nino/Southem oscillation (ENSO) episodes on South Pacif ic albacore (Thunnus alahnga) is analyzed using historical catch per unit e ffort (CPUE) data collected from the Taiwanese distant-water longline fishi ng fleet, Southern oscillation indices and large scale measurements of seaw ater temperature. Two effects were identified from a time series analysis: (1) relatively low CPUE followed the onset of ENSO episodes with 8 and 4 yr time lag in fishing grounds between 10 degrees S and 30 degrees S and sout h of 30 degrees S, respectively; and (2) towards the beginning of ENSO epis odes CPUE was slightly higher in fishing grounds between the equator and 10 degrees S. The time lag of the first effect corresponds to the time interv als that would be expected before the recruitment for the fish spawned duri ng ENSO episodes. The second effect is interpreted as a result of the anoma lous temperature structure of the seawater. The rise of the mixed layer dep th (MLD) in the equatorial region as well as the narrowing volume of water comprising the albacore's temperature preference in the subtropical region would both be expected to lead to a (slight) increase in the hook rate of a lbacore in the two regions. (C) 1998 Elsevier Science B.V. All rights reser ved.