Reproductive Success of Smallmouth Bass Estimated and Evaluated from Family-Specific DNA Fingerprints

Abstract

This paper presents the results of the first attempt to estimate and identify factors influencing individual reproductive success in a fish species, under natural conditions, after the progeny have dispersed from their site of origin. Using family-specific DNA fingerprints, the reproductive success of male smallmouth bass in Lake Opeongo, Ontario was estimated and evaluated at the point when their offspring were fall young-of-the-year (YOY). For the 1992 spring spawning season, we generated family-specific fingerprints using DNA of fry captured from 116 nests in Jones Bay. In the fall of the same year, 283 YOY were captured by electrofishing along the shoreline of the study area. Using DNA obtained from fin tissue, a fingerprint was generated for each fall YOY and compared to the family fingerprints to determine the family of origin. Males were considered successful if at least one of their offspring survived to the fall YOY stage. Although 27.7% of all males who acquired eggs (N = 57) had at least one offspring surviving to the fall YOY stage, only 5.4% of all spawning males (N = 11) produced 54.7% of the total number of fall YOY captured. If recruitment frequently depends on the success of such a small number of males, then population abundance will be extremely vulnerable to adverse natural and anthropogenic impacts. Because natural resource managers cannot differentiate these few successful males a priori, they cannot differentially protect them from potentially adverse human activities, such as opening the fishing season on a preset date that may fall before the end of brood-guarding in a given year. The evaluation of variables that might influence differences in male reproductive success included male length and age, spawning date, number of eggs and fry within a nest, nest depth, and dominant substrate type both within and surrounding the nest. Logistic regression analysis indicated that none of these variables were significant predictors of male reproductive success (P > 0.05). Additionally, linear regression analysis suggested the lack of a relationship between the number of fall YOY produced per male and these variables. However, a goodness-of-fit test to the Poisson distribution indicated that the number of YOY produced per male does not occur at random (P < 0.001), suggesting that reproductive success was influenced by factors not measured in this study.