Investigating relationships between albacore tuna (Thunnus alalunga) CPUE and prey distribution in the Bay of Biscay

The Bay of Biscay in the northeast Atlantic is an important feeding zone for juvenile albacore tuna (Thunnus alalunga) during their summer migration northwards. Spatial distribution and abundance of their potential prey [planktonic organisms, anchovy (Engraulis encrasicolus) and other small pelagics] were investigated in the southeast Bay of Biscay during acoustic surveys in autumn from 2003 to 2005. The relationships between albacore tuna catch per unit of effort (CPUE), and prey abundance and sea surface temperature (SST) were studied at different spatiotemporal scales. We observed positive and significant correlations between albacore tuna CPUE and anchovy abundance and total prey abundance, at different spatial scales. However, in 2003, a year characterised by extreme temperatures compared to the other years of this study, the relationship between CPUE and prey abundance was much weaker. Instead, we found a significant negative correlation with SST.