Demographic analysis of trade-offs with deliberate fragmentation of streams: Control of invasive species versus protection of native species

Tools restricting the movements of invasive species (e.g. barriers) and reducing habitat fragmentation for native species (e.g. corridors, fishways) provide examples where actions taken to address one environmental concern can hinder efforts to address another environmental concern. We used perturbation analysis of stage-structured projection matrices to evaluate the efficacy of seasonally operated barriers and fishways for controlling non-native sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes while minimizing effects on non-target fishes. For non-jumping fishes migrating in spring, seasonally operated barriers without a fishway will not balance the management objectives satisfactorily. Migration phenologies of the seven common non-target fishes considered in our analyses overlapped considerably with the migration phenology of sea lamprey, with peaks in migration typically being 7–43 days (median 12) from the peak in the sea lamprey migration. Consequently, across species, years, and tributaries, 44–100% of the migratory runs of non-target fishes would be blocked under the 75-day operation period required to block 99% of the sea lamprey spawning run, on average. Reductions in the production of non-target fishes due to blocking were also projected to be similar in magnitude to reductions projected in the production of sea lamprey, unless density-dependent compensation was strong or overlap in migration phenologies between a non-target species and sea lamprey was low. Even under density-dependent compensation, providing a fishway is advisable and passage of non-target fishes may have to be highly effective to avoid population declines in non-jumping species that migrate between a Great Lake and its tributaries.     

Polychlorinated biphenyls and other organic chemical residues in fish from major United States watersheds near the Great Lakes, 1978

Twenty-six composite samples of fish were collected during 1978 from United States watersheds near the Great Lakes and analyzed for polychlorinated biphenyls (PCBs) and related organic chemicals. PCB mixtures resembling Aroclor 1254 were found in all samples, and mixtures resembling Aroclor 1242 (or 1016) were found in 77 percent of the samples. Total PCB concentrations in the whole-fish composite samples ranged from 0.13 to 14.6 ppm; 65 percent of the samples contained more than 2 ppm PCBs. DDT and its metabolites were found in all samples. sigma DDT concentration was 1.66 ppm, and 81 percent of the samples contained less than 1.0 ppm sigma DDT. Chlordane ranged from less than 0.001 to 2.57 ppm in 38 percent of the samples. Hexachlorobenzene was found in 65 percent of the samples, ranging from less than 0.005 to 0.447 ppm. Other chemicals identified by gas chromatography/mass spectrometry included petroleum hydrocarbons and chlorobenzenes, chlorostyrenes, chlorophenols, and chlorinated aliphatic compounds. Fish from the Ashtabula River (Ohio), Rock River (Ohio), and Wabash River (Indiana) contained extremely complex residues of chlorinated and other organic chemicals.     

Dose titration of oxfendazole against common nematodes of swine.

Oxfendazole, a benzimidazole carbamate, was administered as a 0.5% feed additive to 88 pigs naturally infected with two to four nematode species. Dose rates of 1.5 mg/kg of body weight, 3.0 mg/kg, 3.75 mg/kg, 4.5 mg/kg, 6.75 mg/kg, or 9.0 mg/kg were 100% efficacious against Oesophagostomum dentatum and 99.2% to 100% effective against Ascaris suum. Dose rates of 4.5 mg/kg, 6.75 mg/kg, and 9.0 mg/kg were 92.7%, 98.9%, and 99.5% effective, respectively, against mixed populations of Metastrongylus apri and M pudendotectus. Results were variable with Trichuris suis infections. Efficacy was based on the number of nematodes recovered at necropsy. Palatability and acceptability of the feed additive were good, and adverse reactions following administration were not observed.