Publications

Today's inland commercial fisheries are small independent operational units widely dispersed on lakes, impoundments, and streams throughout the vast central plains. The problems of the fisheries are diverse and unique to local conditions. Inland fisheries are particularly important to the Nation in times of international conflict because they are distributed throughout the area and the...

Through a combination of ecosystem homeostasis and the perversity of man and nature, oftentimes the significant biological changes effected by environmental modifications are not detected until long after the initial change has taken place. The immediate impact, which may range from the spectacular to the undetectable, is a deceptive measure of the long-term and often more important...

More than 300 pairs of fine and coarse mesh plankton net samples were collected in the northern basin of Lake Chad during an 18-month period, June 1967 to November 1968. The seasonal distribution and abundance of the dominant species of Rotifera and Crustacea are given in addition to a general description of the hydrology and circulation of the northern basin of the lake. The composition...

Blood cell types of the sea lamprey, Petromyzon marinus, are described and identified and the lineage of mature circulating cells in peripheral blood is traced to blast cells in the hematopoietic fat body. The fat body appears to be the phylogenetic precursor of bone marrow in higher forms, since blood cells originate and begin maturation in this tissue. Experimental animals were...

Five female American brook lampreys, Lampetra lamottei, collected in lakes Michigan and Huron averaged nearly twice as long and about six times as heavy as American brook lampreys of normal size. Three factors suggested that the giant lampreys may have fed parasitically after metamorphosis: morphological adaptations of the species for parasitic life, their large size, and absence of...

A program for plotting bathythermograph transect data on a computer (IBM 1130) printer is available from the Great Lakes Fishery Laboratory. Temperature values are printed in positions proportional to their depths and distances from shore. Contour lines are drawn manually through the plotted points.

A study of the effects of temperature and salinity on ionoregulation in the alewife, Alosa pseudoharengus, revealed that concentrations of sodium, potassium, and calcium in plasma and muscle were similar in fish adapted to fresh water and those adapted to sea water. The non-stressed alewife is apparently an excellent ionoregulator in both environments. Acute exposure to cold caused a...

Abstract has not been submitted

Scale samples collected in 1948 were used to estimate the instantaneous total mortality rate (0.70) and growth for lake trout (Salvelinus namaycush) in Lake Superior before the population had been significantly reduced by the sea lamprey (Petromyzon marinus). Indirect evidence indicates that the instantaneous natural mortality rate was probably 0.10–0.25. The Ricker model was used to...

Lake herring eggs stripped and fertilized from a local stock were incubated in a constant-flow incubator at constant temperatures ranging from 0 to 12.1° C. Rate of development, percentage survival, percentage of abnormal and normal hatching, and length of fry at hatching were determined. The average incubation time from fertilization to 50% hatch varied from 37 days at 9.9-10.3° C to...

Salient features of the development of the industry from about 1815 to 1968, changes in fishing gears and methods, changes in the kinds and abundance of fishes caught, and the attendant effects of disappearing species on the stability of the fishery are described. The history and present status of the walleye, yellow perch, and eight other fishes, still taken in commercial quantities...

The commercial fishery for walleyes (Stizostedion vitreum vitreum) in Lake Erie virtually collapsed in the late 1950's. The extreme decline in production was attributed primarily to a succession of weak year-classes, caused by habitat deterioration (increased water temperatures, enrichment, and pollution) in western Lake Erie. Unusually high fishing intensity and high yields of walleyes...