The use of internal otolith morphometrics for identification of haddock (Melanogrammus aeglefinus) stocks on Georges Bank


Begg, Gavin A., William J. Overholtz, and Nancy J. Munroe
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Internal otolith morphometrics, coupled with image analysis procedures and multivariate statistical analyses, were examined to investigate stock structure of haddock (Melanogrammus aeglefinus) on Georges Bank in the northwest Atlantic. Samples were collected during spring 1995–97 from the Northeast Peak (eastern Georges Bank) and the Great South Channel (western Georges Bank) spawning components. The structure of transverse sagittal otolith sections were described for individual haddock samples from each spawning component by using a combination of linear morphometrics, shape characteristics, and growth increments. Analyses were structured to account for the effects of size, sex, age, and year class. Significant differences in internal otolith structure were found between eastern and western Georges Bank haddock, providing phenotypic evidence of stock separation between the two spawning components. Eastern Georges Bank haddock tended to have smaller internal otolith dimensions than western Georges Bank haddock; these differences appeared to be related to growth rates. Total classification success for each spawning component varied from 61% to 83% for the different age and year-class combinations. Results from this study may be helpful in forming consistent stock definitions that can be used by both U.S. and Canadian fishery management agencies for rebuilding stocks of haddock on Georges Bank.