Gutted to round-weight conversion factors for anglerfish (Lophius piscatorius and Lophius budegassa)

Abstract

In response to a request from the Department of Communications Marine and Natural Resources and fishing industry, the conversion factors used to estimate round or live weights from gutted anglerfish were re-examined. A number of data sources was available from survey data, port sampling and observer trips. In some cases, the liver is left in place when the fish are gutted. For these landings a separate conversion factor is necessary. The conversion factors were found to be independent of fish size, however, some significant differences between the data sources were found. Significant differences between the conversion factors of the two species of anglerfish (Lophius piscatorius and L. budegassa) were also found. As commercial landings of anglerfish are not usually speciated, a generic conversion factor was estimated for Lophius spp. by combining the data for both species after weighting by the estimated proportions of the two species in the Irish landings. The resultant conversion factor for fully gutted fish is 1.23 and 1.17 when the liver is left in place; both estimates are lower than the current Irish factor of 1.28.