Back-calculation of the growth of capelin (Mallotus villosus) in the Canadian Northwest Atlantic from measurements of otoliths

Winters, G. H. (1969) Back-calculation of the growth of capelin (Mallotus villosus) in the Canadian Northwest Atlantic from measurements of otoliths. Masters thesis, Memorial University of Newfoundland.

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Abstract

The otolith radius-fish length relationship in capelin is shown to take the form of an heterogonic curve with an inflexion point occurring at the size of maturity for both sexes. This relationship changes with sex, age and maturity. A linear relationship between otolith radius and fish length, as determined by regression analyses, was found to exist only within an age-group. This necessitated the use of separate equations for back-calculating the lengths of each age. -- Growth curves of Trinity Bay capelin, as constructed from back- calculated lengths, indicated that male capelin grow faster than female capelin up to the age at maturity after which the growth rates remain the same. Inferences about age at first maturity of Trinity Bay capelin are made from otolith-age curves which suggest that capelin normally spawn more than once. -- Growth compensation in its typical form and Lee's phenomenon are shown to exist in capelin and reasons are given for their presence. It is suggested that growth compensation in capelin is not only acquired from the growth patterns of the different age-groups but is also an inherent feature of its growth. -- The method of ageing Trinity Bay capelin from otoliths is validated and the embryonic nucleus or larval check ring is described from the otoliths of larval capelin. Comparison of the otoliths of capelin from various regions of the northwest Atlantic indicates that there is a distinct decrease in the size of the first annulus from south to north. -- The otolith radius-fish length relationships of capelin from various regions of the northwest Atlantic are compared by age, sex and maturity. No consistent differences were apparent except those created by local variations in growth rate and maturity. -- Growth rates of capelin from the Bay of Fundy to northern Labrador are compared from otolith radius-age curves and length-at-age curves. The Bay of Fundy capelin are characterized by a fast growth rate, early maturity and small maximum size; the Labrador capelin are slow-growing, mature later and have a large maximum size; Newfoundland capelin are shown to be intermediate in growth rate. Reasons for these differences are discussed in relation to the hydrography of the area under consideration.

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