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Catch rates of the pelagic species around the Fish Aggregating Devices (aFADs) anchored off the Western coast of Mauritius show that the seasonal variation of the sea surface temperature (SST) has a significant influence on the abundance of the tropical tuna.
The results of the study carried out over the period 2010 to 2012 suggest that the season of relative abundance for the skipjack tuna (Katsuwonus pelamis) is more pronounced during the summer months when SST is higher. The study on the other hand indicates that the yellow fin tuna (Thunnus albacares) prefers the cooler waters which prevail both at start of winter and at the outset of the summer season. The broad annual migration of the yellow fin and skipjack tunas around the anchored FADs is noticeably associated with the annual SST cycle. The results also indicated a marked scarcity in the presence of the big eye tuna (Thunnus obesus) in the landings of the artisanal FAD fishery.
In contrast, data on landings from the licensed industrial foreign long liners operating mostly in the EEZ of Mauritius illustrate that both the yellow fin and the skipjack tunas abound during the summer season. In addition, the landings of the semi-industrial local fleet (long liners <24m) primarily targeting swordfish in Mauritius waters included the big eye tuna (mostly caught in the winter season) and the yellow fin tuna (all year round).
This paper highlights the results based on the analyses on the fish catch data collected from the professional artisanal fishermen operating around FADs off the Western coast of Mauritius with discussion on the relation between effort, SST and the seasonal abundance of the tropical yellow fin and skipjack tuna.
