Age and growth of a sub-Antarctic notothenioid, Patagonotothen ramsayi (Regan 1913), from the Falkland Islands
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The Falklands’ rockcod Patagonotothen ramsayi was aged successfully using whole and sectioned otoliths. Marginal increment analysis showed that one opaque and one translucent zone were laid down each year. Counting daily rings in juvenile fish and back calculating to their assumed hatch dates validated the first annulus. Readings taken from scales and otoliths showed good agreement with no significant difference between them (P>0.05). Inter- and intra-reader comparisons also showed good agreement. The maximum estimated age was found to be 14 years and the calculated von Bertalanffy growth curve L T =33.77(1−e −0.25year(t+1.07)) showed that P. ramsayi is a relatively slow growing fish that attains 5–6 cm L T in its first year and after which grows approximately 3 cm per year until 4 years. Males seemed to have a slightly lower growth rate but attained a greater maximum size than females. The formation of annuli in the otoliths of P. ramsayi seems to coincide with periods of high reproductive activity with both peaks in GSI and the prevalence of translucent margins occurring in July.
KeywordsGrowth Increment Otolith Microstructure Translucent Zone Summer Growth Patagonian Shelf
The ICEFISH cruise was supported by National Science Foundation grant OPP 01-32032 to H. William Detrich (Northeastern University). This is publication number 5 from the ICEFISH Cruise of 2004 (H.W. Detrich, Chief Scientist). P.B. took part in the initial leg of the ICEFISH cruise in May 2004, and we are indebted to Dr. H. William Detrich for his participation and the opportunity to present this work at the ICEFISH symposium held at the University of Maine’s Darling Marine Centre in August 2005. We would also like to thank José R. Fuertes Gamundi (Vigo Shipowners Co-operative, ARVI), the main co-ordinator of the EU Sixth Frame Work CRAFT Project entitled “Promoting Higher Added Value to a Finfish Species Rejected to Sea” (Proposal No. CRAF-1999-71709) for including us into the project. We are grateful to the FIFD observers Mick Hatterlsey, Duncan Brake, Sarah Crofts, Oli Yates, Jorge Torrens, Sam Clark, Sandra Cordes and Teresa Athayde for their help in collecting samples, and Joost Pompert for the data management. We thank Ruben Roa for his advice on statistics. Finally we would like to thank Dr. Mario la Mesa, Dr. Stephen Brouwer and an anonymous reviewer who helped to improve the manuscript.
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