INSULIN-LIKE GROWTH FACTORS AS MARKERS FOR GROWTH RATE IN U.S. LARGEMOUTH BASS POPULATIONS USED FOR FOODFISH PRODUCTION

Largemouth bass are increasingly becoming more popular as a foodfish within the United States aquaculture industry, in part because pond-bank prices have been rising making it a more profitable species for farmers. Many of the private growers are located in the North Central Region (NCR) of the United States and rely on the Northern largemouth bass, Micropterus salmoides, subspecies for foodfish production. A significant limitation to largemouth bass foodfish production in this region is time to market. Many strategies, mostly focused on nutrition, have been attempted to increase the rate of weight gain and reduce time to market.

Because of its recent and rapid rise in popularity, largemouth bass have had little or no genetic manipulation for foodfish production. Most, if not all, of the focus on improving largemouth bass genetics has gone towards recreational angling and selection for large fish with no significant concern for fish age. For largemouth bass produced in the NRC, selective breeding has the potential to be one of the most effective methods of achieving market size at a faster rate than current stocks. This would translate economically to more money in the pockets of the growers and increase potential output to meet growing market demands.

As a first step toward the development of breeding programs focused on growth rate in Northern largemouth bass, growth data was obtained from source hatcheries and modeled to estimate age at market size. From these results, the predicted top two and bottom two performing populations were compared in a growth trial, which included the assessment of insulin-like growth factors I and II as putative biomarkers for growth, both at the genomic and transcriptomic levels. Significant IGF gene polymorphisms were detected across the populations; however, their distribution did not correlate with growth differences. On the contrary, faster growth rate was observed to be negatively correlated to muscle IGF II expression, suggesting its potential as a predictive biomarker to rapid growth.

This research combined statistical, genetic, and molecular techniques as a multi-step approach toward improving largemouth bass stocks for foodfish production. Studies such as this can be used as the building blocks towards genetic improvement of cultured largemouth bass populations, and yield results that can be put into action immediately to assist growers get the most out of current stocks.