THE EFFECT OF GENETIC IMPROVEMENT ON YELLOW PERCH: CHANGES IN GROWTH RATES, FILLET YIELD AND OVERALL GENETIC DIVERSITY
Yellow perch (Perca flavescens) is a particularly important aquacultural and ecological species in the Great Lakes Region (GLR). The demand for yellow perch has remained very high due to its cultural standing as a "peoples's fish" in many Great Lakes states. Yellow perch aquaculture has received tremendous interest in the Great Lakes Region and elsewhere in the U.S. during the past 10 years due to their high market demands and the decline of wild populations, yet despite this opportunity, rapid expansion of the yellow perch aquaculture industry has not occurred, particularly due to observed significant differences among strains for weight gain and food conversion ratios.
A genetic improvement program underway since 2007 at the School of freshwater Sciences, University of Wisconsin - Milwaukee, has produced three generations of captive, genetically improved perch, using growth rates as primary selective trait. Two geographical strains were developed using fertilized eggs collected from the wild (Choptank River, Chesapeake Bay estuarine system; and Perquimans River, Albemarle Sound estuarine system), and subjected to indoor flow-through and recirculating conditions. These strains were selected due to their superior growth and domestication, compared to other geographic strains from the GLR and other parts of the native distribution range. Fish were initially randomly mated and spawned, then the resulting larval perch were fed a combination of live feeds (rotifers, Artemia nauplii, etc.), feed trained to accept formulated feeds, and weaned off live feeds. Fingerlings were then pooled and randomly assigned tanks under flow-through conditions, and fed at 1.5-1.8% calculated biomass ration. These pooled cohorts were then reared for 12 months, and final selection of 90th percentile top-performing fish in terms of weight were selected and developed into filial broodstocks. Selected fish were genotyped using microsatellite markers, and PIT tagged.
Overall effects of the selection process have been positive, with a mean reduction of 3.5 months to reach market size (8.5 months for F3 cohort, vs. 12 months for F1 cohort), an increase in mean weight after 12 months. Genetic diversity indices show moderate decreases in heterozygosity due to directed mating and trait selection.