Density and Distribution of Larval Fishes in Pentwater Marsh, a Coastal Wetland on Lake Michigan

Abstract

In order to better understand the importance of a Great Lakes coastal marsh on fish production, the fish larvae of Pentwater Marsh, a drowned river-mouth wetland on Lake Michigan, were studied over a 3-yr period. Fish larvae were sampled at night by push nets in the channels and bayou-mouths and drop nets in the shallow, vegetated bayous of the marsh. Larval fish diversity and abundance were highest in 1984, perhaps due to more stable temperatures, higher water levels, and/ or increased submerged vegetational cover. In all years, carp (Cyprinus carpio) dominated the catch with marsh-wide densities of up to 30 larvae/m 3. Subdominant species included sunfish (Lepomis spp.) and various minnows (Cyprinidae). Eighteen taxa were identified. Larval fish densities were 2 to 100 times higher in the shallow-water bayous than in the bayou-mouths and river channels. Larval fish densities were generally higher than documented for other wetland areas. However, previous studies may have underestimated densities since shallow-water sampling was not included and they were conducted during years of low water level. Coastal wetlands likely harbor greater numbers of young fishes than previously reported, emphasizing the importance of such areas to the ecology of the Great Lakes.