Neuroendocrine Mediation of Photoperiod and Other Environmental Influences on Physiological Responses of Salmonids
Neuroendocrine Mediation of Photoperiod and Other Environmental Influences on Physiological Responses of Salmonids

Author: Hugh A. Poston

Publisher:

Published: 1978

Total Pages: 20

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Manipulation of photoperiods, combined with modifications by other environmental conditions such as temperature and salinity, can alter growth, smoltification, and sexual maturation of salmonid fishes by way of a neuroendocrine pathway. The extent of responses of salmonids to environmental changes, however, is restricted by circadian endogenous metabolic rhythms that cannot be completely overcome by external factors. The success of the manipulation of photoperiod depends primarily on four factors: the daily length and the duration of the light treatment; the season and time of day during which fish are exposed to light; the age, sex, size and species of fish; and the type of physiological response under consideration. Although gaps remain in the available information, salmonids apparently need systematically changing, intermittent periods of darkness for optimum long-term stimulation of growth, reproduction, and migration.

Proximate Composition and Caloric Content of Eight Lake Michigan Fishes
Proximate Composition and Caloric Content of Eight Lake Michigan Fishes

Author: Donald V. Rottiers

Publisher:

Published: 1982

Total Pages: 16

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The proximate composition (percentage lipid, water, fat-free dry material, ash) and caloric content of eight species of Lake Michigan fish were measured: lake trout, coho salmon, lake whitefish, bloater, alewife, rainbow smelt, deepwater sculpin, and slimy sculpin. Except for alewives, proximate composition and caloric content did not differ significantly between males and females. Although the caloric content of all species varied directly with lipid content and inversely with water content, an increase in lipid content did not always coincide with a proportional increasein caloric content when other components of fish composition were essentially unchanged. This observation suggests that the energy content of fish estimated from the proximate composition by using universal conversion factors may not necessarily be accurate.

Acute Toxicity of Six Forest Insecticides to Three Aquatic Invertebrates and Four Fishes
Acute Toxicity of Six Forest Insecticides to Three Aquatic Invertebrates and Four Fishes

Author: Herman O. Sanders

Publisher:

Published: 1983

Total Pages: 12

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Technical grade and field formulations of six experimental forest insecticides -- methomyl, carbaryl, aminocarb, trichlorfon, fenitrothion, and acephate -- were tested for acut toxicity against three species of aquatic invertebrates, (a daphnid, an amphipod, and larvae of a midge), and four species of fish (bluegill, rainbow trout, fathead minnow, channel catfish). Five of the six insecticides were highly toxic or extremely toxic to the daphnid, amphipod, and midge larvae. The sixth insecticide, acephate, was not toxic to invertebrates at concentrations up to 50 mg/L. Five of the insecticides ranged from highly toxic (methomyl to channel catfish) to relatively non-toxic (trichlorfon to fathead minnows); the sixth, acephate, was only slightly toxic to the fishes tested.

Population Biology of Yellow Perch in Southern Lake Michigan, 1971-79
Population Biology of Yellow Perch in Southern Lake Michigan, 1971-79

Author: LaRue Wells

Publisher:

Published: 1983

Total Pages: 28

ISBN-13:

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This study was based mainly on gill-net collections of yellow perch made during July and August 1971-79, in southern Lake Michigan at Grand Haven, Saugatuck, South Haven, Benton Harbor, and New Buffalo, Michigan; Michigan City and Gary, Indiana; Waukegan, Illinois; and Milwaukee, Wisconsin. Geographical abundance varied and were partly attributable to differences in fishing mortality.

Ecology of Larval Fishes in Lake Oahe, South Dakota
Ecology of Larval Fishes in Lake Oahe, South Dakota

Author: William Roland Nelson

Publisher:

Published: 1980

Total Pages: 24

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The time and location of spawning, food and larvae, and habitats used as nursery areas by young-of-the-year fishes were studied from 1972 to 1975 in South Dakota waters of Lake Oahe, a main stem Missouri River reservoir. Sampling locations were in the tributary rivres -- the Grand Moreau, and Cheyenne -- and their embayments. Year-class strength of river-spawning species was strongly correlated with river flow rates during the spawning season. Success of reservoir-spawning species was primarily dependent on above-average water levels, which inundated terrestrial vegetation to provide a substrate for egg deposition and cover for larvae. Preserving adequate streamflow and enhancing reservoir shoreline areas by managing water levels, seeding vegetation, and eliminating grazing alongshore would probably ensure adequate reproduction of most areas.

Monthly Catalog of United States Government Publications
Monthly Catalog of United States Government Publications

Author: United States. Superintendent of Documents

Publisher:

Published: 1979

Total Pages: 1130

ISBN-13:

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February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index