Reproductive Success of Stocked Lake Trout in Southwestern Lake Michigan

摘要

The purpose of this study was to examine the relative vulnerability of lake trouteggs and fry to predation or other biological interaction with native and exotic species at natural and artificial spawning sites in southern Lake Michigan. The authors focused especially on spawning activities at the Burns Harbor breakwater in Indiana, because it is the only site in southern Lake Michigan at which lake trout are presently known to spawn in substantial numbers. Data were collected in an effort to assess the efficacy (and efficiency) of remote video and sonar as indicators of spawning activity. The authors used divers to explore new sites and evaluate their potential as spawning habitat. Autumn collections of eggs by gangs of egg nets and egg traps were used as a direct indicator of spawning activity at various sites in southwestern Lake Michigan. Instantaneous spawning intensity was measured by deploying buoyed gangs of egg collecting devices, and cumulative egg deposition by burying egg bags in the substrate. The authors estimated the densities of emergent fry at Burns Harbor in spring by deploying fry traps, and trawled near spawning areas in an effort to capture post-emergent fry. The authors examined the guts of potential lake trout egg predators captured during IDNR lake trout gillnetting operations in fall, and the guts of potential fry predators captured by trawling and in fry traps during the spring. During the winter of 1994-1995, the authors reared wild-spawned lake trout eggs and samples of stripped eggs obtained from gillnetted lake trout. The authors performed laboratory experiments investigating the characteristics of round goby (Neogobius melanostomus), a new exotic species in Lake Michigan, as a potential lake trout egg and fry predator. The authors also investigated the effect of zebra mussel fouling on overwinter survival of lake trout eggs in the laboratory.