Morphometric variation in Loligoforbesi and Loligo vulgaris: regional, seasonal, sex, maturity and worker differences

22 páginas, 3 figuras, 17 tablas, 1 apéndice
Morphometric variation in the squid Loligoforbesi was investigated to quantify effects of region, season, sex and maturity. Practical exercises were carried out using this species and the congeneric Loligo vulgaris to evaluate differences in measurements by different workers. The utility of meristic characters was also examined. Consistent significant differences were found between measurements by different workers, although this problem may be reduced with experience and many of the differences were small compared with observed differences between areas, particularly differences between Loligoforbesi from the Azores and elsewhere (Scotland, Spain, Portugal). Body shape in Loligoforbesi varied significantly in relation to maturity stage and, to a lesser extent, with season. Multivariate analysis of morphometric characters for samples collected in Scottish waters over 12 months revealed no consistent differences between localities. In contrast, there were marked differences between Loligoforbesi from the Azores and those from UK waters. If future studies on geographic variation in loliginids are to make use of morphometric characters, they should be based on simultaneous sampling to minimise effects of season and maturity, and all measurements on a single character should be made by a single worker.
This work was funded by the Commission of the European Communities within the frame of the EEC research programme in the fisheries sector (FAR, Contract No. MA 1.146). Data collection by AG and FGH in 1989 was supported by the Spanish Ministry of Education and Science and the British Council under the British/Spanish Joint Research Programme (Acciones Integradas 1989/90).