Size-frequency estimates of secondary production by Mysis relicta in Lakes Michigan and Huron

Abstract

Data from five Great Lakes studies of Mysis relicta populations were reanalyzed to calculate secondary production estimates using the size-frequency method. Production estimates (P) ranged from 0.25 to 3.2 g dry weight m −2 yr −1 . Average annual biomass {xxB} and mean annual density (xxD) were 0.11–1.11 g dry weight/ m 2 and 25–434 animals/ m 2 , respectively. P:{xxB} ratios varied only between 2.2 and 3.3. Maximum and minimum biomass values within a study varied by a factor of 519 for one study but by less than 17 for the others. Highest estimates of P, {xxB} and {xxD} were calculated for collections from a 50-m station in Lake Michigan despite the larger populations suspected to be present at greater depths sampled in the other studies. These conservative estimates provide a basis for scaling trophic interactions involving M. relicta and emphasize findings by previous workers that night-time sampling with vertical net hauls is the best available technique for quantitative studies of M. relicta populations in the Great Lakes.