Journal Article

Morphometric and gonad maturity in the spider crab <i>Maja brachydactyla</i>: a comparison of methods for estimating size at maturity in species with determinate growth

Antonio Corgos and Juan Freire

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 5, pages 851-859
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2006.03.003
Morphometric and gonad maturity in the spider crab Maja brachydactyla: a comparison of methods for estimating size at maturity in species with determinate growth

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Ontogenetic changes in the relative growth of males and females of the spider crab Maja brachydactyla, a species with terminal moult and determinate growth, were analysed and related to their reproductive (maturity) status. Based on the allometry of cheliped size, two morphometric groups of males separated juvenile and adult phases. Juvenile males also showed two growth phases, immature (smaller ones, without spermatophores) and adolescent (with spermatophores). Size at gonad maturity in males (estimated as CL50) was 96.2 mm carapace length (CL). Histological analysis of males showed that >60% of morphometric juveniles and 100% of morphometric adults had spermatophores in the gonad. Females begin to develop gonads 2–3 months after the terminal moult. Size at morphometric maturity was estimated comparing two methodologies: the size at 50% maturity (CL50) and the median size of adult cohorts (CLM). In all cases the CLM size at maturity was greater than that resulting from the CL50 method, and, in contrast to the CL50 method, CLM was greater for females in all cases. Therefore, CLM reflects better the real size at maturity for M. brachydactyla. Owing to spatial segregation of adults and juveniles and the availability of morphological and morphometric methods to estimate maturity status, we suggest a combination of spatial closures and direct protection of juvenile habitat as management strategies alternative to minimum landing sizes.

Keywords: decapods; Maja brachydacta; maturation; morphometrics

Journal Article.  5915 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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