A second assessment of the stock of megrim Lepiodorhombus whiffiagonis in Divisions Vll b, c, j and k

Abstract

An assessment of megrim captured by Irish and joint venture (Spanish) vessels in Divisions Vll b, c, j, k is based on landings from both fleets and discards from Irish vessels targeting whitefish and Nephrops. Fishing activity by the joint venture fleet is centred on the 200m depth contour. Megrim CPUE has declined since 1985. Lepidorhombus whiffiagonis constitutes the majority of the landings by joint venture vessels; L. boscii amounts up to 2% by weight of the landings from deeper waters. In catches of undersized megrim, L. boscii was 12% of the total. Landings of L. whiffiagonis have similar length frequency distributions in the Irish inshore and joint venture fleets. There are indications of what may be seasonal abundance in the discards and landings of Irish vessels fishing inshore. Discards were calculated as 77% of landed weight in the first half of the year and 31% in the second. Megrim with an inshore provenance were slightly larger than those coming from deeper waters. The following growth parameters were calculated: L∞ = 51.2cm, k = 0.17 and to = -0.97. A catch curve derived from the combined landed and discarded megrim has a value of Z = 0.45, slightly less than the value calculated for the inshore Irish fleet (0.49). F is consequently in much the same position as in the 1989-90 assessment, on the negative slope of the yield per recruit curve.