Geology topics

T.J. Desorcie

Publications and source records attributed to T.J. Desorcie.

4 recordsLinked to original sources

USGS2008

Lake trout population dynamics at Drummond Island Refuge in Lake Huron: Implications for future rehabilitation

The Drummond Island Refuge (DIR) was established in 1985 as part of the rehabilitation effort for lake trout Salvelinus namaycush in Lake Huron. Since then, several strains of hatchery-reared lake trout have been stocked annually at the DIR. An intensive lampricide treatment of the St. Marys River during 1998-2001 was expected to lower the abundance of sea lamprey Petromyzon marinus within the DIR by 2000. We conducted annual gill-net surveys during spring and fall to evaluate the performance of each of the strains of lake trout as well as that of the entire lake trout population (all strains pooled) in the DIR during 1991-2005. The criteria to evaluate performance included the proportion of "wild" fish within the population, spawner density, adult survival, growth, maturity, and wounding rate by sea lampreys. Wild lake trout did not recruit to the adult population to any detectable degree. During 1991-2005, the average density of spawning lake trout appeared to be marginally sufficient to initiate a self-sustaining population. Survival of the Seneca Lake (SEN) strain of lake trout was significantly higher than that of the Superior-Marquette (SUP) strain, in part because of the higher sea-lamprey-induced mortality suffered by the SUP strain. However, other factors were also involved. Apparently SUP fish were more vulnerable to fishing conducted in waters near the refuge boundaries than SEN fish. The St. Marys River treatment appeared to be effective in reducing the sea lamprey wounding rate on SEN fish. We recommend that the stocking of SEN lake trout in the DIR, control of sea lampreys in the St. Marys River, and reduction of commercial fishery effort in waters near the DIR be maintained. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2006

Spring-summer diet of lake trout on Six Fathom Bank and Yankee Reef in Lake Huron

We examined the stomach contents of 1,045 lake trout (Salvelinus namaycush) caught on Six Fathom Bank and Yankee Reef, two offshore reef complexes in Lake Huron, during late spring and early summer 1998-2003. Lake trout ranged in total length from 213 to 858 mm, and in age from 2 to 14 years. In total, 742 stomachs contained food. On a wet-weight basis, alewife (Alosa pseudoharengus) dominated the spring-summer diet of lake trout on both of these offshore reef complexes. Alewives accounted for 75 to 90% of lake trout diet, depending on the lake trout size category. Size of alewives found in lake trout stomachs increased with increasing lake trout size. Faster growth of juvenile lake trout on Six Fathom Bank and Yankee Reef than on Sheboygan Reef in Lake Michigan was attributed to greater availability of small alewives on the offshore reefs in Lake Huron. Our findings indicated that alewives inhabited Six Fathom Bank and Yankee Reef during spring and summer months. Thus, our study provided support for the contention that alewives may have interfered with natural reproduction by lake trout on these offshore reef complexes in Lake Huron.

Journal of Great Lakes Research↗

USGS2002

The growth-temperature relation and preferred temperatures of juvenile lake herring

Lake herring, Coregonus artedi, were once extremely abundant in the Great Lakes where they functioned as a major trophic integrator, directly linking the planktonic crustacean resource to lake trout. Salvelinus namaycush. Lake herring populations in the Great Lakes collapsed during the middle third of the 20th century due to overfishing, degradation of critical habitat in major production areas, and interaction with exotic species. Fishery and habitat impediments to the recovery of lake herring have been removed, and it may now be possible to reestablish the species in its former habitats in the Great Lakes if adverse interactions with exotic species can be controlled within acceptable limits. To determine the potential for thermal niche overlap and adverse interaction with exotic fishes, juvenile (age-0) lake herring were held in the laboratory at 5, 10, 15, 18, and 21 C, and fed ad libitum for 54 days. The optimum temperature for growth in weight was about 14.5 C, indicating the fundamental thermal niche was 12.5-16.5 C. Fish used in the growth study were also tested in a vertical thermal gradient tank to measure their final preferendum. The final preferendum, 16.5 C, was in close agreement with the optimum temperature for growth and within the fundamental thermal niche. Both the optimum temperature for growth and the final preferendum have been used as measures of thermal niche, but this is the first time both measures were made on the same group of fish. Published information on the fundamental thermal niche, preferred temperatures, thermal habitat use, and feeding habits of alewives, rainbow smelt, and ruffe, indicates they will co-occur in spring, or summer with age-0 lake herring and that collectively they pose a predation threat to small, age-0 lake herring.

Advances in Limnology↗

USGS1999

Variation in net trophic transfer efficiencies among 21 PCB congeners

We tested the hypothesis that the efficiency with which fish retain polychlorinated biphenyl (PCB) congeners from their food strongly depends on K ow and degree of chlorination of the congener. We used diet information, determinations of concentrations of individual PCB congeners in both coho salmon ( Oncorhynchus kisutch ) and their prey, and bioenergetics modeling to estimate the efficiencies with which Lake Michigan coho salmon retain various PCB congeners from their food. The retention efficiency for the tetrachloro congeners averaged 38%, whereas retention efficiencies for higher chlorinated congeners ranged from 43 to 56%. Not including tetrachloro congeners, we found neither decreasing nor increasing trends in the efficiencies with which the coho salmon retained the PCB congeners from their food with either increasing K ow or increasing degree of chlorination of the PCB congeners. We concluded that (a) for PCB congeners with 5−8 chlorine atoms/molecule, K ow and degree of chlorination had little influence on the efficiency with which coho salmon retained the various PCB congeners in their food, and (b) the efficiency with which coho salmon retained tetrachloro PCB congeners in their food appeared to be slightly lower than that for higher chlorinated PCB congeners.

Environmental Science & Technology↗