P. Ivory, F. Jeal, and C. P. Nolan
Department of Zoology, Trinity College, Dublin 2, Ireland
Publication (Upload) date: 29 September 2004
IVORY, P., F. JEAL, and C. P. NOLAN. 2005. Age Determination, Growth and Reproduction in the Lesser-spotted Dogfish, Scyliorhinus canicula (L.). J. Northw. Atl. Fish. Sci., 35: 89-106. doi:10.2960/J.v35.m504
Successful fisheries management is based on the knowledge of species-specific life history data, comprising age and general morphometric information. This study presents such information for the lesser-spotted dogfish (Scyliorhinus canicula).
Four samples of S. canicula, totalling 745 individuals (310 males and 435 females), were collected by fisheries scientists from research and commercial vessels in ICES areas VIIa and VIIg, over the period November 1999–November 2000. A further 10 hatchling specimens (5 males and 5 females), from a commercial aquarium, were also collected. The total body length range for males was from 10.4 cm to 71.0 cm and for females was 10.3 cm to 70.0 cm.
A total of 706 specimens (301 male and 405 female) were aged using crystal violet stained sagittal sections of vertebral centra. Centrum length grew in proportion to total body length for males and females. Age estimates ranged from 0 years (hatchlings) to 11 years for males and 0 years to 12 years for females. Annual periodicity of growth increment deposition was suggested following analysis of the centrum edge characteristics of a subsample of specimens by all three readers. The von Bertalanffy growth parameters L∞, K and t0 were estimated for males (L∞ = 87.42 cm, K = 0.118, t0 = -1.09) and females (L∞ = 75.14 cm, K = 0.15, t0 = -0.96) separately. The length at 50% maturity for males was 53.5 cm and for females was 57.0 cm. These findings increase the life history data available for S. canicula and form a valuable contribution to the implementation of basic management measures to ensure the sustainability of catches of this by-catch species.
Key words: age estimates, annual periodicity, crystal violet, length at 50% maturity, sagittal sections, Scyliorhinus canicula, von Bertalanffy growth parameters