Feeding trials using fall chinook salmon finglerlings were conducted at the Salmon Cultural Laboratory, Longview, Washington, during 1971 for the purpose of improving the Abernathy diet formula. The results indicated that cottonseed meal could replace a portion of the fish meal in the diet without reducing fish growth, but similar substitutions of wheat and corn gluten meal reduced growth. Fish growth was significantly increased when a diet containing 50 percent protein and 3,350 kcal per kilogram was fed as compared with a diet containing 45 percent protein and 3,350 kcal per kilogram. Soybean lecithin proved to be equal to soybean oil as a caloric source when fed at 2 percent of the diet. Two types of dried whey product with different levels of lactose content produced similar growth response. Reducing the dried whey portion of the diet to 5 percent did not affect growth, nor did methionine supplementation produce any effects. Anchovy meal was unsuitable as a replacement for herring meal.

The percentage body weight contributed by the ovaries and frequency distributions of ovarian egg diameters were reliable indicators of the spawning season of largemouth bass, in West Point Reservoir in 1977.

Two formulations of the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) - the butyl ester (BE) and the propylene glycol butyl ether ester (PGBEE) -- had 96-h LC50's to cutthroat trout and lake trout ranging from 490 to 1,200 microgram/liter in static tests. A third formulation -- the isooctyl ester (IE) -- was not toxic to cutthroat trout or lake trout at concentrations below 60.000 microgram/liter. The butyl ester (2,4-D BE) was slightly more toxic than 2,4-D PGBEE, and the toxicity of both esters increased as water temperature decreased.

Stomachs of 1,064 alewives, 1,103 yellow perch, 246 spottail shiners, 288 trout-perch, 454 slimy sculpins, and 562 fourhorn sculpins from Lake Michigan were examined for food contents. Fish were sampled primarily from March to November and nearly all were caught at the bottom in the southeastern part of the lake near Saugatuck, Michigan. Pontoporeia was the most commonly reprented food item in the stomach contents of the fish examined, with immature midges, Mysis (a type of freshwater shrimp), copepods, cladocerans, fingernail clams and crayfish also being represented. Different species consumed different proportions of foods. Zooplankton was the principle food of alewives and spottail shiners, but was also consumed in small quantities by yellow perch and trout perch. Mysis was important to fourhorn sculpins, in addition to Pontoporeia. Immature midges were a major portion of spottail shiners and trout perch, also being consumed by alewives. Fish were often the most important food of yellow perch in the largest size category. Crayfish were a sizable portion of the diet of yellow perch on rocky bottoms, but sparingly on smooth bottoms. Spottail shiners also ate substantial numbers of fingernail clams.

The razorback sucker, which has declined in abundance in the upper Colorado River primarily because of man's impact on the environment, has been recommended for listing as "threatened" in the U.S. Department of Interior's list of threatened or endangered species. During the present investigation, razorback suckers were nevertheless found in relatively large concentrations at two restricted locations -- the mouth of the Yampa River and a flooded gravel pit connected to the Colorado River near Grand Junction, Colorado.

Significant changes have occurred in the distribution of trout in streams of Great Smoky Mountains National Park since 1900. By the mid-1970's the original range of the native brook trout had been reduced by about 70% and the species was relegated to suboptimal habitat in head water streams. Most of the stream sections lost by brook trout became the territory of the introduced rainbow trout, which in 1977 occupied about 80% of the Park waters. After 1950, brown trout introduced in State waters outside the Park established reproducing populations in some 50 miles of stream formerly occupied only by rainbow trout. If current trends continue, the recovery of brook trout in Park water may be difficult, if not impossible, and brown trout may occupy much of the territory now held by rainbow trout.

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.