Aberrant Crystallization of Pollock (Pollachius virens) Otoliths

Abstract

The occurrence of aberrant crystallization in Scotian Shelf pollock (Pollachius virens) sagittae was examined. The crystalline structure of the aberrant form was calcite, in contrast with the usual aragonite. The frequency of abnormal crystallization increased with fish length, and otoliths of fish originating from certain geographic locales had a significantly higher incidence. However, the extent of calcitic crystallization did not increase with fish length and was inversely correlated with frequency of occurrence; completely calcitic otoliths were rarely found. The region where centres of calcitic crystallization most frequently occurred was in the vicinity of the rostrum. While the causal mechanism for the aberrant crystallization could not be identified, it appears likely that to permit the simultaneous deposition of calcite and aragonite, the organic precursor for subsequent crystallization must differ locally on the surface of affected otoliths.