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the population biology of the thornback ray, raja clavata in caernarfon bay, north wales

Published online by Cambridge University Press:  06 October 2005

j.m. whittamore
Affiliation:
school of ocean sciences, university of wales—bangor, menai bridge, anglesey, ll59 5ab, uk school of biosciences, hatherly laboratories, university of exeter, exeter, ex4 4ps, uk
i.d. mccarthy
Affiliation:
school of ocean sciences, university of wales—bangor, menai bridge, anglesey, ll59 5ab, uk
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Abstract

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amid concern about the status of skates and rays in welsh waters the present work set out to provide up-to-date information on the population biology of raja clavata in caernarfon bay. the von bertalanffy growth parameters were l=100.9 cm, k=0.18 y−1 and t0=−0.95 y for males; and l=117.6 cm, k=0.16 y−1 and t0=−0.7 y for females. male r. clavata reached 50% maturity at 58.8 cm and 3.9 y, which was smaller and younger than females (l50 and a50 were 70.5 cm and 5.3 y, respectively). although previously over-exploited, the present estimate of total mortality (z) was 0.48–0.49 y−1 which, in terms of replacement mortality (calculated as 0.7 y−1), suggests no immediate prospect of recruitment failure for r. clavata in caernarfon bay. the potential for the recovery of a depleted population is discussed in relation to the allee effect.

Type
research article
Copyright
© 2005 marine biological association of the united kingdom