Assessment of Nursery Habitat Use By Larval Fishes in the St. Clair River Delta, MI

Recruitment of fish into wetland nursery areas is critical during the larval stage; however habitat factors responsible for good recruitment have been little studied. We surveyed twenty locations in the North and Middle Channels of St. Clair River Delta, between May and July 2010 and 2011. Larval fish were collected weekly with a 0.5-m conical net and quatrefoil light traps to assess community composition and abundance. We measured a wide range of abiotic and biotic factors to establish differences between nursery areas. Nursery area use was quantified by number of individuals of each species and total abundance of fish collected. We used multivariate techniques to reduce abotic variables to a simple variable, lotic input. We then compared that variable to  general community composition as determined by Non-metric multidimensional scaling (NMDS). Community composition correlated strongly (0.696, P<0.001) with lotic input. This suggested that nursery habitat use can be explained for different species by  lotic input, or how habitat differs from the main channel. Community composition also showed a relationship with relative submerged aquatic vegetation (SAV) density (MRPP, P=0.003). These data suggest nursery area habitat use varies by species, the density of SAV, and proximity to the main body of flowing water.