Recursos Marinos y Pesquerías

Mark-recapture analysis of growth in Maja brachydactyla [Working paper]

13/05/05 ,

A. Corgos, M. P. Sampedro, E.
González-Gurriarán and J. Freire. Growth at moult, intermoult period
and moulting seasonality of the spider crab Maja
brachydactyla: combining information from mark-recapture and experimental
studies. (Working paper, v.1, May 2005) [pdf]

An analysis of growth at moult (for
both the prepubertal and terminal moults), moulting seasonality and the
intermoult period in the spider crab Maja squinado in the Ría de A Coruña (NW
Spain) was carried out based on a mark-recapture experiment. Crabs between 70
and 130 mm carapace length (CL) undergo a mean increase at moult of 32.4% from
their pre-moult size. Generalised Linear Models (GLMs) were used to construct
growth models, employing a combination of information from the mark-recapture
study and other previous studies performed in both laboratory and extensive
culture, to estimate the effects of the biological variables and the study
method. No differences were found in the growth rate between males and females.
However, the effects of the study method, the premoult CL and the interaction between
them were significant. The smallest-sized crabs undergo a greater increase in
size in the laboratory and culture studies, while the largest individuals
undergo greater growth in the field. The mean intermoult period estimated for
prepubertal moults in the field ranged from 50 to 86 days, which is similar to
the 84.7 days observed in the laboratory study. The prepubertal moults occurred primarily in
spring and autumn in the field, while under culture conditions, the crabs
moulted mainly in the spring. The intermoult period for terminal moults was
estimated to be around 90 days, slightly lower than the value of 104 days
obtained in the laboratory. The terminal moult took place generally in summer
(June-September) both at sea as well as in culture experiments. The intermoult
period of juveniles at sea was highly variable, and some of the specimens did
not moult for more than 5 months.