Isolating the influence of growth rate on maturation patterns in the smallmouth bass (Micropterus dolomieu)

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 62; no. 4; pp. 844 - 853
• Main Authors: Dunlop, Erin S, Shuter, Brian J, Ridgway, Mark S
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.04.2005; National Research Council of Canada
• Subjects: Agnatha. Pisces; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Freshwater; Fundamental and applied biological sciences. Psychology; Micropterus dolomieu; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Freshwater environment; Aquatic environment; Vertebrata; Life history; Growth rate; Pisces; Micropterus dolomieu; Fishing
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f05-045

In this study, we examine the divergence in growth and maturation between two populations of smallmouth bass (Micropterus dolomieu) introduced from a common source a century ago. To determine if the divergence in maturation is simply a plastic response to differences in growth rate, we use a new approach to estimate and then compare the probabilistic maturation reaction norms (PMRNs) for each population. The PMRNs for 5-year-old males are similar in the two populations, suggesting that the observed divergence in maturation is largely a plastic response to growth rate differences. For one population, we document the time course of maturation changes for the 60-year period from 1937 through 1990; while the mean length at maturation for 5-year-old males exhibits a steady downward trend (beginning at 31 cm and ending at 26 cm), their PMRNs vary over a much narrower range (25–27 cm) and do not exhibit a consistent temporal trend. These observations are consistent with the hypothesis that most of the observed change in maturation since introduction is a product of phenotypic plasticity, driven by environmentally based differences in growth rate. Our study provides an instructive example of how the PMRN approach can be used to isolate the role of growth rate variation in generating life history differences.