Publications

Ten species were commercially harvested in Lake Oahe, among which bigmouth buffalo (Ictiobus cyprinellus) predominated (63.8% of the total weight), smallmouth buffalo (Ictiobus bubalus) and goldeye (Hiodon alosoides) ranked second, and third. Variations in the seasonal and annual production of buffalo were governed by market conditions and availability. Production of minor species...

Trawls of various designs and sizes were compared to evaluate their use for monitoring and harvesting fish populations in Lake Oahe. Catches of a 10.7-m semiballoon trawl, selected to monitor changes in the fish populations from 1965 to 1970, showed a downward trend in the abundance of all species, except walleye; the decline was largest in the lower area of the reservoir with a slight...

The limnetic crustacean zooplankton of Lake Oahe was dominated by copepods. Cyclops bicuspidatus thomasi was the dominant crustacean throughout the lake. Mesocyclops edax, Diaptomus ashlandi and Daphnia pulex were major components of the zooplankton in the deep, downstream portion of the lake while Bosmina longirostris and Daphnia retrocurva were important constituents in the river-like...

The physical and chemical characteristics presented provide a description of Lake Oahe and establish bases for certain characteristics which may alter as the reservoir ages. Water temperatures were strongly influenced by wind-driven currents and water depth. The duration of thermal stratification varied from about 3 wk in the upstream portion of the reservoir to about 15 wk near the dam...

No abstract available.

No other lake as large as Lake Erie (surface area, 25,690 km2) has been subjected to such extensive changes in the drainage basin, the lake environment, and the fish populations over the last 150 years. Deforestation and prairie burning led to erosion of the watershed and siltation of valuable spawning grounds. Marsh spawning areas were drained. Lake-to-river spawning migrations of...

Man's activities have caused great changes in Lake Michigan in the past 120 years. Although changes in water chemistry and lower biota have been generally modest (except locally), those in native fish stocks have been vast. Exploitation, exotic fish species, and eutrophication and other forms of pollution all have played a role in bringing about the changes (mostly declines in abundance)...

Potential commercial fish production was estimated for U.S. waters of western Lake Erie in 1969 from pounds landed and pounds discarded. Periodic observations of catches in haul seines and trap nets revealed that about 37% of the catch (by weight) in haul seines and 26% of that in trap nets were low-value fishes that were discarded. Projection of these discarded catches to include the...

Total mercury in a variety of substances is determined rapidly and precisely by direct sample combustion, collection of released mercury by amalgamation, and photometric measurement of mercury volatilized from the heated amalgam. Up to 0.2 g fish tissue is heated in a stream of O2 (1.2 L/min) for 3.5 min in 1 tube of a 2-tube induction furnace. The released mercury vapor and combustion...

The thermal regime of Lake Michigan is described on the basis of the analysis of 1,671 bathythermograph casts made in 1954 and 1955. The beginning, duration, geographic extent, and ending of thermal stratification were determined from 51 thermal profiles from all areas of the open lake. The lake gained heat for about 5 months (mid-March to mid-August) and lost heat over the rest of the...

Total and dissolved phosphorus, nitrate, and chlorophyll a were measured at four stations in northern Lake Michigan (inshore Michigan, offshore Michigan, offshore Wisconsin, and inshore Wisconsin) and one station in southern Green Bay during 16 sampling periods in 1965. The nutrients were measured at depths of 2, 5, and 10 meters and chlorophyll a at 2 meters. In Green Bay total...

Fishery productivity of the Great Lakes has declined drastically since settlement of the area. Premium quality fishes of the Great Lakes such as whitefish, lake trout, and walleyes have been replaced by less desired species. This change is attributed to selective overfishing, pollution, and the extreme instability of fish populations. Sea lamprey predation is still a vexing problem but...