Estimation of the Diopatra neapolitana annual harvest resulting from digging activity in Canal de Mira, Ria de Aveiro

Abstract

Bait digging for recreational and commercial fishing is widely practiced and economically significant. Since polychaetes often form part of the diets of several demersal species they are commonly used as fresh bait by sports and professional fishermen. The objectives of this paper are to quantify the annual bait digging of harvest Diopatra neapolitana in the intertidal mudflats of Canal de Mira, Ria de Aveiro, Portugal and comment briefly on its significance for management. Annual harvest, defined as D. neapolitana (kg) caught by collectors, was calculated as the product of independent estimates of harvesting effort using a progressive count and harvest rate through an access survey. Harvesting effort was higher during spring tides in all seasons except in winter and harvest rate lower during winter, regardless of tidal range, and higher during spring tides. Bait collection in the Canal de Mira is very intense with an annual harvest in excess of 45,000 kg per year valued at over € 325,000 per year.

Management of the remove needs to take account of both the ecosystem impacts of bait digging and the socio-economic importance of bait digging to the many families involved.