Densities, diets, and growth rates of larval Alewife and Bloater in a changing Lake Michigan ecosystem.

Transactions of the American Fisheries Society
By: , and 

Links

Abstract

Variability in abiotic and biotic factors during larval stages has profound impacts on fish recruitment. In Lake Michigan, where the composition of lower trophic levels has undergone considerable changes in the past decade, managers are concerned that fish recruitment could be negatively affected. We hypothesized that spatial variation in Lake Michigan larval fish density and growth can be explained by various environmental predictor variables. In July 2015, we sampled larval fish and zooplankton at 24 sites (distributed among eight transects) around Lake Michigan. We measured larval fish densities and estimated growth rates and diets of the two most abundant species: the Alewife Alosa pseudoharengus and Bloater Coregonus hoyi (prey fish that represented 89% and 4% of the total catch, respectively). Larval Alewife densities at a given site ranged from 0 to 42.57 larvae/100 m3, but no explanatory variables explained the variation. Alewife mean growth rate equaled 0.50 mm/d, and fish age and zooplankton density best explained growth variation across sites. Larval Bloater densities ranged from 0 to 1.16 larvae/100 m3, and mean growth rate was 0.21 mm/d. Across all sites, 67% of larval Alewife stomachs were empty, whereas only 16% of Bloater stomachs were empty. Larval fish growth rates observed in our study were at least 40% slower than those reported in previous decades for both Alewife and Bloater. Worsening prey environment for pelagic larvae, such as Alewife and Bloater, during the era of abundant dreissenid mussels could reduce the probability of strong year‐classes, which in turn may affect growth and survival of recreationally important salmonine predators.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Densities, diets, and growth rates of larval Alewife and Bloater in a changing Lake Michigan ecosystem.
Series title Transactions of the American Fisheries Society
DOI 10.1002/tafs.10171
Volume 148
Issue 4
Year Published 2019
Language English
Publisher Wiley
Contributing office(s) Great Lakes Science Center
Description 16 p.
First page 755
Last page 770
Country United States
State Illinois, Michigan, Wisconsin
City Frankfort, Ludington, Manitowoc, Racine, St. Joseph, Saugatuck, Sturgeon Bay, Waukegan
Other Geospatial Lake Michigan