USE OF GONAD INDEXES TO ESTIMATE THE STATUS OF REPRODUCTIVE ACTIVITY OF FEMALE SWORDFISH, XIPHIAS-GLADIUS - A VALIDATED CLASSIFICATION METHOD

Gonad weights and results of histological analyses from 85 swordfish, Xiphias gladius, were used to develop a validated method for classific ation of the reproductive activity of female swordfish based on gonad indices (GI's). The validated method provides a significant improvemen t over previously published (unvalidated) methods. The method was show n to be independent of the length of individual fish, important when l ength is used as a criterion for selection of individuals from which s ummary statistics based on GI are being developed. Female swordfish we re found to be in a reproductively active condition when GI = In(gonad weight in gm)/ln(eye-fork-length in cm) greater than or equal to 1.37 5. Classification methods for species with comparable reproductive hab its and characteristics may be alike, and it is speculated that result s for other billfishes would be similar to those described for swordfi sh.