Morphometric criteria for estimating sexual maturity in two snappers, Etelis carbunculus and Pristipomoides sieboldii

Issue:

Author(s): 
DeMartini, Edward E., and Boulderson B. Lau
Cover date: 
1999
Pages: 
449-458
Abstract: 

A gross measure of reproductive condition (ovary weight adjusted for body size and oocyte volume) is developed and evaluated as an alternative to commonly used gonad indices, for classifying the maturity status of individual ehu (Etelis carbunculus) and kalekale (Pristipomoides sieboldii), two species of eteline snappers (Lutjanidae) that contribute to the deep-slope handline fishery in Hawaii. Discriminant analysis and logistic regression, based on body length, ovary weight, and oocyte volume, were used to classify fish as either immature or mature. Discriminant analysis correctly classified the maturity of about 98% of both ehu and kalekale, with histological criteria as the standard for comparison. Logistic regression correctly classified maturity of 97% of the ehu and 100% of the kalekale. Misclassification errors increased by 3.75–5% (discriminant analysis) or 0–5% (logistic regression) if oocyte volume was excluded and only body length and ovary weight were used as predictors of maturity. For kalekale, estimates of lengths at which 50% are sexually mature (L50) were identical (29.0 ±1.8 [SE] cm fork length, FL; r2=0.92), when maturity was classified histologically or by logistic regression on body, ovary, and oocyte metrics. For ehu, L50 estimates were similar (r2≈0.96) for maturity assignments based on histology (27.9 ±2.4 cm FL) and on logistic regression using gross metrics (27.8 ±2.3 cm FL). We conclude that gross morphometrics can provide adequate proxies for histological evidence when categorizing sexual maturity in asynchronous, multiple-spawning fishes like eteline lutjanids. The potential benefits of using gross metrics for assessing sexual maturity in other serial spawners are briefly discussed.