Is Lake Trout Recruitment Impacted By Zebra Mussels in Otsego Lake, NY?

Zebra mussels (Dreissena polymorpha) became established in Otsego Lake in 2008 and by 2011 carpeted the Lake Trout (Salvelinus namaycush) spawning shoal at Bissel Point. The literature suggests that the presence of zebra mussels would negatively impact lake trout recruitment, because of reduced attractiveness of the substrate and the degradation of interstitial water quality within the substrate. In this study current lake trout recruitment was examined and compared to recruitment levels observed in 2003-2004 before the zebra mussel invasion. Emergent fry traps were used to capture lake trout fry swimming up from the substrate at the Bissel Point in April-May 2013 - 2015. Twelve emergent fry traps with a diameter of 81 cm (area=0.52 m²) were set on four linear transects in depths of 30, 60 and 90 cm, across the entire shoal. Fry recruitment between years was variable. Both the highest (4.83 m²/day) and lowest (1.59 fry/m²/day) recruitment levels occurred in the presence of zebra mussels. Fry recruitment was 3.44-3.96 fry/m²/day in the absence of zebra mussels. Therefore, contrary to expectations from the literature, lake trout fry recruitment in the presence of zebra mussels did not differ significantly from recruitment levels in the absence of zebra mussels.