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Effects of Post-impoundment Shore Modifications on Fish Populations in Missouri River Reservoirs
In the Missouri River main stem reservoirs in Montana, North Dakota, and South Dakota, hydrodynamic processes have decreased the lengths of shorelines and changed their configurations during the first 20 to 25 years of impoundment. Physical changes to the shore probably influenced fish abundance and species composition by changing the quality and quantityt of spawning and nursery habitat.
Research Report
None
Research Report
None
Carp, River Carpsucker, Smallmouth Buffalo, and Bigmouth Buffalo in Lewis and Clark Lake, Missouri River
Studies of age composition, growth, length-weight relation, reproduction, year-class strength, and food habits were conducted from 1962 to 1964 on carp, river carpsucker, smallmouth buffalo, and bigmouth buffalo in Lewis and Clark Lake, a main stem Missouri River reservoir impounded in July 1955. Slow growth of these fishes was attributed to low standing crops of plankton and bottom fauna which may have resulted in excessive turbidity and rapid water exchange in the reservoir. All four species produced strong year classes in the 2 years following impoundment of Lewis and Clark Lake; reproduction since that time has been poor. These species did not produce year classes comparable in abundance to thos which occurred following impoundment because of unfavorable environmental conditions. The probable major limiting successful reproduction was lack of rise in water level durig the spawning period.
Some Chronic Effects of DDT on Cutthroat Trout
Effects on cutthroat trout (Salmo clarki lewisi) of periodic exposure to different levels of DDT in bath and in food were determined over a 20-month period involving one spawning cycle. High dosages produced a marked increase in mortality, probably by reducing the resistance to nonspecific stressors; survivors fish in high-dosage lots were significantly larger than those in control and low-DDT lots. Intermediate and low dosages of DDT generally did not measurably affect mortality, growth, or reproductive potential, indicating that a threshold level exists around 0.1 p.p.m. monthly in contact form and around 0.3 mg. DDT per kg. of fish weekly in the diet for the toxic effects of DDT.
Food Habits of Striped Marlin and Sailfish Off Mexico and Southern California
Stomach contents of 924 striped marlin landed in the sport catches at Mazatlan, Sinaloa, and Buena Vista, Baja California, Sur, Mexico, and San Diego, California, and of 197 sailfish from Mazatlan and Buena Vista were examined. The striped marlin and sailfish fed primarily on pelagic fishes and cephalopods. By volume the major foods were squid (principally Dosidicus gigas) for striped marlin at Mazatlan and for striped marlin and sailfish at Buena Vista, northern anchovy for striped marlin at San Diego, and threadfin for sailfish at Mazatlan. Locally differences in food habits were pronounced, and some seasonal and yearly differences were found.
Predatory Behavior of Some Shore Fishes in the Gulf of California
A study area in the Bahia de Palmas, was established and predatory behavior in some Gulf of California shore fishes was studied to define certain general activity patterns.
Life History of the Spottail Shiner (Notropis Hudsonius) in Southeastern Lake Michigan, the Kalamazoo River, and Western Lake Erie
Spottail shiners (Notropis hudsonius) were sampled from portions of Lake Michigan, the Kalamazoo River, and Lake Erie to determine ages, growth rate, sex ratios and life history information.
Review of Fishery Studies on Missouri River Main Stem Reservoirs
The six main stem Missouri River reservoirs are described, and information available through 1964 on plankton, water chemistry, fish populations, and water management is discussed. At maximum pool, these reservoirs have a capacity of 76 million acre-feet and a surface area of 1.2 million acres. Each of the upper reservoirs is larger in capacity and area than the sum of the lower three reservoirs. Fishes common in this system are bigmouth buffalo, carp, river carpsucker, yellow perch, goldeye, northern pike, sauger, walleye, white crappie, black crappie, and freshwater drum. Available information on growth rates, year-class strength, and relative abundance of common species is described. Limiting factors of the environments are the turbidities, wind, and fine soils. Research needs and problems relative to fish production are discussed.
