A new optimal allocation sampling design to improve estimates and precision levels of discards from two different Fishery Units of Spanish trawlers in northeast Atlantic waters (ICES subareas VIIc,j,k)

摘要

The present report discusses a new onboard sampling design for the Spanish trawlers in northeast Atlantic waters -International Council for the Exploration of the Sea (ICES) subareas VIIc,j,k-. This sampling design comprises three stages: i) number of vessels and trips per vessel to be sampled; ii) the minimum number of sampled hauls; and iii) a temporal distribution of those sampled hauls throughout the fishing trip to balance hauls sampling along the fishing trip. As a result, an optimal allocation sampling is suggested, comprising at least one vessel and one trip per vessel to be sampled monthly, between 30 to 50 sampled hauls within that fishing trip, and a time-division for hauls during the fishing trip, containing 8-15 sampled hauls at the beginning, middle and end of the trip.