Dissertation title: Understanding growth patterns of coastal largemouth bass: integrating bioenergetics and life-history theory
Compared with those found in freshwater, estuarine populations of largemouth bass (Micropterus salmoides) exhibit substantially different vital rates. Largemouth bass found in Alabama’s Mobile-Tensaw River Delta are characterized by slow growth, high condition, and low annual survival consistent with other coastal populations. Although largemouth bass are extremely abundant in this system, fish exceeding 5 lbs are extremely rare (see 2008 B.A.I.T. Report). Much interest has been directed toward determining if the size structure of the population could be enhanced. Increasing harvest of largemouth bass has been a common fisheries management approach to enhance growth, yet high condition factors suggest that intraspecific competition is low in this population.
My dissertation research is focused on examining largemouth bass life history and growth patterns in the Delta by determining their allocation of energy to somatic growth, reproduction, and mesenteric fat reserves throughout life. Currently, we have found somatic energy density to be 22% higher for coastal versus freshwater largemouth bass, indicating that greater consumption is necessary to obtain growth rates comparable to freshwater populations. Further, the quantity of mesenteric fat reserves remains high throughout the year in both sexes, contributing to their observed high body condition. High fat reserves may provide resources to compensate for periodic stressful salinity levels; however, high caloric density reduces the somatic scope for growth in weight. Additionally, a portion of the population devotes energy to reproduction early such that they spawn in the first year of life, which could be an adaptive strategy to overcome high mortality rates. Thus, somatic growth may be reduced in favor of allocating energy towards processes that enhance their survival and reproduction, thereby increasing their lifetime fitness. By estimating the metabolic cost of salinity at varying temperatures as a function of body size using flow-through respirometry, I will be able to reparameterize the largemouth bass bioenergetics model for coastal systems. Combining bioenergetics with life-history analyses allows us to determine how these freshwater fish adapt to a dynamic estuarine environment.
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