Application of the Gómez-Muñoz model to estimate catch and effort in squid fisheries in Scotland

Abstract

The Gómez-Muñoz model, which utilises interview data obtained from fishermen, was developed to aid the management of small-scale artisanal fisheries, where there may be a dearth of catch and effort data, and has been successfully used in the estimation of catch per unit effort (CPUE) in this type of fishery in Galicia. The suitability of applying the model to two cases in Scotland, a non-targeted by-catch fishery off the northwest coast of Scotland and a directed squid fishery in the Moray Firth, is explored. The interview information returned from the directed fishery is generally of higher quality. In order to study the model behaviour, an alternative parameterisation is carried out. In general, the model was found to be most sensitive to parameters having a direct effect on catch and effort. Calculated confidence intervals are rather wide but could be improved by refining the interview protocol with emphasis placed on reducing the timing from monthly to weekly. A database of 671 individual vessels’ landings into Scottish ports in 2000 is created and, from this, an index of fishing effort calculated, which displays a close approximation with official data. The results from the by-catch fishery are extrapolated to larger areas. In all cases, the predicted catches are higher than official figures although similar trends are evident.