Influence of temperature on growth and survival of young-of-year rainbow smelt in St. Martin Bay, Lake Huron

Rainbow smelt are an important prey species for native and introduced piscivores in the Great Lakes, but also function as a predator on native fish and zooplankton species.  To better understand rainbow smelt early life history dynamics on a regional scale, spawning rainbow smelt and subsequent larval fish cohorts were surveyed in St. Martin Bay, Lake Huron during 2008-2009.  During 2008, rainbow smelt spawning runs lasted approximately one week due to rapidly warming water temperatures but occurred over a three week period in 2009 as a result of suppressed water temperatures.  Peak larval rainbow smelt densities in 2008 were double peak densities observed in 2009.  Length frequencies during both years revealed a second cohort of lake spawned larvae appeared in late June concurrent with an increase in larval density.  Survival of the early stream spawned cohort was lower in 2008 relative to 2009.  Average growth rates were higher during 2008 and were associated with higher mean water temperatures and lower larval densities later in the growing season.  Increased ability to predict rainbow smelt year class strength based on environmental conditions during early life history will benefit management of predator-prey dynamics in the Great Lakes.