Assessment of maturity state and seasonality of reporduction in Loligo forbesi (Cephalopoda: Loliginidae) from Scottish Waters

• Main Authors: Boyle , P.R., Ngoile, M.A.K.
• Format: Book Part
• Language: English
• Published: Tokai University Press 1993
• Subjects: DML
• Online Access: https://oceanrep.geomar.de/id/eprint/50933/; https://oceanrep.geomar.de/id/eprint/50933/2/3039.pdf

Maturity scales for male and female Loligo forbesi are described utilizing qualitative features of reproductive state. Sexes can be distinguished by external dimorphisms; hectotylus, seminal receptacle, colour of accessory nidamental glands and chromatophore patterns, at sizes down to 70 mm (DML), below which internal examination is necessary. In these samples from Scottish waters males were significantly more numerous for most of the year except attimes during the main period of sexuall maturity (November - March) when the sex ratio was equal or slightly dominated by females. A series of quantitative maturity indices based on morphometric and gravimetric measurements of reproductive components is compared with assessment of maturity using the scale. The genadosomatic index and maturity coefficient were better correlated with maturity state than indices based on other components. Males matured slightly earlier in the year than females and at a greater mean size (computed mean sizes at maturity 205mm DML, 192mm DML females). No significant differences were found in reproductive characteristics and timing of reproduction between samples from the north eastern Atlantic and North Sea areas. Estimates of total potential fecundity gave a mean of 6500 eggs (range 4260-17650, n = 91).