Standardized CPUE Indices for Greenland Halibut in NAFO Divisions 3LMNOBased on Spanish Commercial Catch Rates

Standardized CPUE series using a Generalized Linear Model for Greenland halibut in Div. 3LMNO, based on catch and effort data from the Spanish trawl fleet since 1991 are presented. Fixed factors considered in the model were: year, month, vessel, Division and depth and the interactions analysed were: Division – depth and month – Division. All the factors and interactions analyzed are significant. The total proportion of variance explained by this model was 40%. The results indicate a decrease trend in the catch rate index in recent years from highest values in 2000. Introduction The Spanish Greenland halibut fishery in Div. 3LM Regulatory area is performed by bottom trawlers since 1990 (Junquera et al., 1992). From about 1993 the activity of this fleet has been spread to the south, into Div. 3N and 3O shelf edge, where at present a significant proportion of this fleet effort is displayed (Junquera et al., 2000). Greenland halibut is the main resource for Spanish fleet in NAFO Regulatory Area and Spanish catches represent more than 40% of the total catches of this stock during last years. The objective of this study is to standardize CPUE series for Greenland halibut in Div. 3LMNO based on catch and effort data recollected by scientific observers onboard the Spanish trawl fleet since 1991. Since Greenland halibut is the target species of the fleet analysed here, the standardized CPUE data can be considered as an index of the fishable biomass of this stock. Material and Methods 1Catch and effort data. Records of catch and effort data from the Spanish Greenland halibut fishery was collected in Div. 3LMNO by scientific observers from the national sampling program since 1991. While those records varied in coverage over the years, it is assumed that the available data are representative of the fishery, considering that the Spanish fleet catches constitute the major component of the total Greenland halibut catch in the Regulatory Area. Data were recorded and analyzed on a haul by haul basis. Catch in kilograms per hour (CPUE) was the unit measure selected to standardize the series. Since the database of records contain data from different fleets directed to several species, as a first step, an analysis was carried out to select the hauls directed to Greenland halibut. For this purpose, the hauls where the catches of Greenland halibut plus Grenadiers were bigger than total catches of any other species present in the catches were selected.