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USGS1974

Electrophoresis as a management tool

The theme of this 1974 Northeast Fish and Wildlife Conference is 'A New Era'. Indeed, it is a new era for improved techniques to assist in management of our fish and wildlife resources for the maximum benefit of all. In some cases, the new techniques are primarily used in research.on fish and wildlife, and the results from the research are used to aid management and enforcement agencies in the decision-making process. One of the newer techniques that is being applied to problems in fisheries and wildlife is electrophoresis. In this paper, we review briefly the techniques of electrophoresis and illustrate research problems in wildlife and fisheries where the use of electrophoresis is now assisting or may potentially aid in management decisions.

Transactions of the Northeast Fish and Wildlife Co↗
USGS1983

Trends in organochlorine and mercury residues in common loon (Gavia immer) eggs from New Hampshire

Failed eggs collected from New Hampshire common loon (Gavia immer) nests in 1979 (N = 15) and 1981 (N = 21) were analyzed for organochlorines and mercury (Hg). In contrast to reports of previous samplings, DDT was not detected in any egg. PCB and DDE residues showed declining trends. Dieldrin was present at low levels in > 50% of the samples. Eggshell thickness was significantly correlated with DDE residues in the eggs of both sampling years; shell thickness is now (1981) comparable to that of museum specimens collected before 1946. Unlike organochlorine residues, Hg residues have shown no decrease in loon eggs. Percentage of loon eggs that contained > 0.5 ppm Hg increased between 1979 and 1981; 2 1981 eggs contained over 1.0 ppm Hg. Lead, zinc, cadmium, chromium and selenium also were analyzed in 1979, and residues were low and variable. Significance of these residue trends and other population factors for loons are discussed, and comparisons with residues of other loon populations in the United States and Canada are made.

Transactions of the Northeast Fish and Wildlife Co↗
USGS1978

Biochemical identification of mallard-black duck hybrids through a breeding program and in nature

From 1974 to 1976, a breeding program was used to produce black duck-mallard hybrids for the evaluation of inheritance patterns of serum proteins and esterases. In addition to the initial crosses, a series of matings in 1975 and 1976 were designed to evaluate inheritance patterns in hybrid matings with either black duck or mallards. At the F1 level, hybrids were easily distinguished. However, mallard or black duck crosses with hybrids were detectable as hybrids in only 11.5 - 22.6% of the progeny using serum proteins, and 22.6 - 38.8% using serum esterases. Concurrent with the breeding program, a field survey indicated hybrid frequencies ranging from 4% to 28%.

Transactions of the Northeast Section of the Wildl↗
USGS1980

Computer simulation models as tools for identifying research needs: A black duck population model

Existing data on the mortality and production rates of the black duck (Anas rubripes) were used to construct a WATFIV computer simulation model. The yearly cycle was divided into 8 phases: hunting, wintering, reproductive, molt, post-molt, and juvenile dispersal mortality, and production from original and renesting attempts. The program computes population changes for sex and age classes during each phase. After completion of a standard simulation run with all variable default values in effect, a sensitivity analysis was conducted by changing each of 50 input variables, 1 at a time, to assess the responsiveness of the model to changes in each variable. Thirteen variables resulted in a substantial change in population level. Adult mortality factors were important during hunting and wintering phases. All production and mortality associated with original nesting attempts were sensitive, as was juvenile dispersal mortality. By identifying those factors which invoke the greatest population change, and providing an indication of the accuracy required in estimating these factors, the model helps to identify those variables which would be most profitable topics for future research.

Transactions of the Northeast Section of the Wildl↗
USGS1980

Factors affecting waterfowl breeding density and productivity estimates in the Northeast

During 1977-79, information useful for making breeding pair and brood surveys was obtained while studying black duck (Anas rubripes) habitat selection and productivity in south-central Maine. Surveys should be initiated in relation to sunrise and sunset time. Morning versus evening counts, familiarity with the survey area, wetland dynamics of the study area, wetland surface water area, and allotment of relative survey effort are discussed as they affect the conduct and results of brood surveys.

Transactions of the Northeast Section of the Wildl↗