No abstract

Rainbow smelt Osmerus morda\. introduced into the Great Lakes watershed (Crystal Lake, Michigan) in about 1912, began coloni/ing the Great Lakes in the 1920s. The species now is found throughout much of the Great Lakes watershed of Ontario and in the Mississippi-Missouri drainage as a result of inadvertent or intentional introductions. Gill-net and trawling surveys in 1989 and 1990 of 79 lakes (92 separate times or sites) in the Winnipeg River svstem of the Hudson Bay drainage in northwestern Ontario, southeastern Manitoba, and northeastern Minnesota revealed or confirmed the presence of rainbow smelt in 19 lakes and extended the species* known range in the Rainy, English, and Wabigoon river systems. Rainbow smelt also were discovered in Lake Winnipeg late in 1990 and in Lake of the Woods in early 1991. Elsewhere, the establishment of rainbow smelt in new water bodies often has been associated with changes in native fish populations. The potential now exists for further spread of rainbow smelt in this watershed as far as Hudson Bay.

Table II. Comparison of Experimentally Determined with Calculated Adsorption Parameters adsorption adsorption rate capacity, We (g/g) constant, ky (min~1) vapor exptl caled % dev exptl caled % dev CCI4 0.741 735 chloroform 0.728 0.693 +5.1 780 834 -6.5 benzene 0.404 0.409 -1.2 1029 1031 -0.2 p-dioxane 0.476 0.483 -1.4 1083 971 +11.5 sec-butylamine 0.331 0.337 -1.8 928 1066 -12.9 1,2-dichloroethane 0.616 0.583 +5.7 1048 916 + 14.4 chlorobenzene 0.545 0.527 -3.4 799 859 -7.0 acrylonitrile 0.404 0.375 +7.7 1160 1251-7.3 cm:!/g and a structural constant k of 1.5 X 10-8 (cal/mol)-2. Thus, at a relative pressure, P/Po, of 0.0936 the adsorption space Wv was 0.467 cm'Vg, and at a P/Po of 0.3448, Wv was 0.478 cm:Vg.Values for the kinetic adsorption capacity We were calculated for the various vapors by using Equation 7, inserting into

This study examined populations of white suckers (Catostomus commersoni), in two physically and chemically similar lakes in the vicinity of, and receiving heavy-metal fallout from, a base-metal smelter complex near Flin Flon, Manitoba. The white suckers occupying Hamell Lake, Saskatchewan, which is contaminated by Zn, Cu, and Cd, showed signs typical of a population under stress when compared with the population in Thompson Lake, Manitoba, which contains much lower levels of these metals. Hamell Lake white suckers showed greatly increased growth in length and weight, increased fecundity, and earlier age of maturation, but reduced spawning success, reduced larval and egg survival, smaller egg size, and reduced longevity compared with Thompson Lake white suckers. We attribute these differences to elevated heavy metals in Hamell Lake waters, particularly in early spring, a most critical period in the reproductive cycle of these fish. Effects of the metals on other species of fish in Hamell Lake are also discussed. Key words: heavy metals, fish, population, stress, white sucker

Rising angler interest in walleye Stizostedion vitreum, a general decline in natural recruitment in some waters, and increasing demands for stocking have produced a need to evaluate stocking strategies. Such evaluations were the subject of the Walleye Stocks and Stocking Symposium summarized herein. Among walleye stocking evaluations reported in the symposium, 32% of fry stockings, 32% of small‐fingerling stockings, and 50% of advanced‐fingerling stockings were considered successful. Further improvement in stocking success requires research into the factors that affect survival. Matching stocking times and places to appropriate food resources appears to be a key element in successful introductions of young walleyes. Walleye stocking should be tailored to each system, not based on a set number and size offish. Genetic and chemical markers facilitate comparisons of fry stocking with fingerling stocking under similar biological and environmental conditions. Anglers surveyed contended that fishing experience is more important than catch rate, an attitude that will help managers shift the public's attention from stocking to maintenance of habitat and water quality.