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Development of Two New Sampling Techniques for Assessing Lake Trout Reproduction in Deep Water
Author(s) -
Riley Jacob W.,
Thompson Neil F.,
Marsden J. Ellen,
Janssen John
Publication year - 2010
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/m09-213.1
Subject(s) - electrofishing , reef , fishery , salvelinus , trout , environmental science , waves and shallow water , abundance (ecology) , reproduction , fish <actinopterygii> , oceanography , ecology , biology , geology
Efforts to restore lake trout Salvelinus namaycush at shallow sites have yielded minimal success in the lower four Great Lakes, and management agencies are examining offshore deepwater reefs as possible sites for restoration efforts. Previous techniques developed for assessing egg deposition and fry relative abundance in shallow waters are not viable for use on deep offshore reefs. To assess lake trout reproduction at deep reefs, two new methods (deepwater egg traps and remote electrofishing) were tested in Lake Champlain, Vermont. Deepwater egg traps were paired with buried egg bags to compare egg collections between the two types of gear at shallow sites in Lake Champlain. After testing, the new egg traps were deployed in Lake Michigan to quantify egg deposition at two sites within the Mid‐Lake Reef Complex. There was a significant positive correlation between estimates of egg density in the paired deepwater traps and buried egg bags and no significant difference between egg densities in the two types of gear. In Lake Michigan, eggs were collected at depths greater than 35 m; the egg densities within the Mid‐Lake Reef Complex were above or similar to egg densities at shallow sites in Lake Michigan. To assess fry relative abundance, a remotely operated electrofisher with video was tested on different densities and life stages of lake trout fry in the laboratory and was used to detect fry in Lake Champlain. The remote electrofisher detected fry in 90% of laboratory trials and 34–56% of field trials. Fry were vulnerable to the electrofisher at all developmental stages, and fry detection from the remote electrofisher was proportional to fry density in the laboratory and fry catch per unit effort from traditional emergent fry traps. These methods provide the potential to detect and quantify lake trout egg deposition and detect fry at deep offshore sites and may improve evaluation of the contribution of deep reefs to lake trout restoration.