Use and advice on incorporating ecosystem indicators in the stock assessment of north Atlantic swordfish

No abstracts are to be cited without prior reference to the author.

Observations of opposing trends in abundance for northern Swordfish suggested the possibility of a shift in abundance from warm, southern latitudes to cooler, more northern latitudes. Several of the observed indices of abundance changed sharply in direction in from negative to positive, while others showed an opposite change. The observed changes in the direction of the abundance indices correspond with changes in trends in the size of the Atlantic Warm Pool (AWP), the change in sign of the Atlantic Multidecadal Oscillation (AMO), and the North Atlantic Oscillation (NAO). To quantify a possible relation between the changes in abundance and the various candidate environmental indices, we fit the assessment model by allowing area specific catchabilities (q) to be modulated by the AMO and estimated an associated slope parameter that described the relationship between the AMO and residuals of the fit to the CPUE times series. The many of the CPUE slope parameters were significantly different from zero, and the pattern of the slope patterns suggested an east-west difference that was very similar to that of the NAO and other correlated oceanographic environmental indicators