Geology topics

David A. Nortrup

Publications and source records attributed to David A. Nortrup.

2 recordsLinked to original sources

USGS2000

A new approach toward evaluation of fish bioenergetics models

A new approach was used to evaluate the Wisconsin bioenergetics model for lake trout ( Salvelinus namaycush ). Lake trout in laboratory tanks were fed alewife ( Alosa pseudoharengus ) and rainbow smelt ( Osmerus mordax ), prey typical of lake trout in Lake Michigan. Food consumption and growth by lake trout during the experiment were measured. Polychlorinated biphenyl (PCB) concentrations of the alewife and rainbow smelt, as well as of the lake trout at the beginning and end of the experiment, were determined. From these data, we calculated that lake trout retained 81% of the PCBs contained within their food. In an earlier study, application of the Wisconsin lake trout bioenergetics model to growth and diet data for lake trout in Lake Michigan, in conjunction with PCB data for lake trout and prey fish from Lake Michigan, yielded an estimate of PCB assimilation efficiency from food of 81%. This close agreement in the estimates of efficiency with which lake trout retain PCBs from their food indicated that the bioenergetics model was furnishing accurate predictions of food consumption by lake trout in Lake Michigan.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS1990

Contaminant residues in the bloater ( Coregonus hoyi ) of Lake Michigan, 1969-1986

Residues of DDT, PCBs, and dieldrin in Lake Michigan bloaters ( Coregonus hoyi ) decreased between 1969 and 1986. All values for contaminant residues were measured and reported as μg/g of whole fish, wet weight; the error limits represented the 95% confidence interval half widths. Total DDT content declined 87%, from 9.9 in 1970, when its use was banned, to 1.3 in 1974, and then averaged 0.88 in 1978–1986 with a low of 0.67 in 1986. Between 1976–1986, p,p’DDD averaged 0.08 and p,p’DDT averaged 0.1; p,p’DDE reached a low of 0.48 in 1980, then averaged 0.53 in 1980–1986. Dieldrin averaged 0.25 until 1974, when it was banned, peaked at 0.55 in 1978, and decreased to 0.20 by 1986. PCBs, first analyzed in 1972, declined 64% (from 5.7 to 2.2) between 1972 and 1980 and were at 1.64 in 1986. The great decline in PCBs occurred following the 1976 ban. A 49% decrease in the lipid content of bloaters from 1980 to 1986 suggested a dietary change possibly due to changing food source makeup.

Journal of Great Lakes Research↗