Pre and Post Spawn Population Demographics for Yellow Perch in Southern Lake Michigan

Yellow perch were collected using gill nets in the southern Lake Michigan near Michigan City, Portage, and East Chicago in the summers of 2009, 2011, and 2012. Pre and post spawn fish demographics were compared using mean lengths, sex ratios, and CPUE to determine if there was a shift in the population structure following the spawn. Spawning occurred between mid May and early June, with the peak spawn in late May in all years, as shown by logistic regression analysis. The mean length of males increased 3% from 219mm pre-spawn to 225mm post-spawn, while the mean length of females increased 10% from 238mm pre-spawn to 261mm post-spawn. The proportion of males captured was 65 % pre-spawn and dropped to 6 % post-spawn. The results indicate that more, larger fish migrated into the area in the post-spawn period, suggesting that these fish spawned in a different location and then moved to the southern waters of the lake to feed on the large amounts of forage fish.