On the relationship between El Niño/Southern oscillation and South Pacific albacore

Abstract

The influence of El Niño/Southern oscillation (ENSO) episodes on South Pacific albacore (Thunnus alalunga) is analyzed using historical catch per unit effort (CPUE) data collected from the Taiwanese distant-water longline fishing fleet, Southern oscillation indices and large scale measurements of seawater 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°S and 30°S and south of 30°S, respectively; and (2) towards the beginning of ENSO episodes CPUE was slightly higher in fishing grounds between the equator and 10°S. The time lag of the first effect corresponds to the time intervals that would be expected before the recruitment for the fish spawned during ENSO episodes. The second effect is interpreted as a result of the anomalous temperature structure of the seawater. The rise of the mixed layer depth (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 albacore in the two regions.