ENHANCING DIET ANALYSES OF PISCIVOROUS FISHES IN THE NORTHWEST ATLANTIC THROUGH IDENTIFICATION AND RECONSTRUCTION OF ORIGINAL PREY SIZES FROM INGESTED REMAINS

Biological interactions among species can play a dominant role in stru cturing marine fish communities. Specifically, predation may represent a significant source of mortality for larval and juvenile fishes. Ana lysis of predator diet requires accurate information on the identity a s well as the sizes of prey consumed. In examinations of stomach conte nts of piscivorous fishes, the condition of recovered prey items varie s substantially not only in the large range of digestive states encoun tered but also in the occurrence of partially consumed fishes. To esti mate the original sizes of well-digested and partially consumed prey f ishes we constructed a series of predictive equations relating total l ength, fork length, and weight of fish to seven morphometric measureme nts including dorsoventral body depth, eye diameter, caudal peduncle d epth, pectoral-fin length, opercle length, cleithrum length, and denta ry length for ten common prey fishes in the Northwest Atlantic. All re lationships were highly significant, with coefficients of determinatio n typically exceeding 0.90 and mean percent prediction errors less tha n 10%, indicating that reliable original size estimates are obtainable from incomplete fish remains. To aid in field-based identification of prey fishes, we extracted and examined opercles, cleithra, and dentar ies from each fish. Careful examination of bones revealed prominent di agnostic characteristics with clear differences among family taxa, dem onstrating their potential utility as identification tools. Used colle ctively, the predictive equations and the diagnostic features of the b ones should allow for inclusion in diet analyses of prey items previou sly designated as unidentifiable or unmeasurable, and thus increase th e amount of dietary information obtainable from stomach contents analy ses of Northwest Atlantic piscivores.