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Extension of the range of most of the esocid species has posed a problem of interspecific hybridization which could be harmful to indigenous pike species. In this paper literature is reviewd and the success of reciprocal crosses is recorded, including drawings and photographs showing the development of progeny. Fertility of some F1 hybrids was also investigated since this tow would reflect on the biological relationship of the species. It appears that even though many species can be artificially hybridized, isolating mechanisms may prevent or retard hybridization under natural conditions.
The brook trout of Great Smoky Mountains National Park are relatively scarce and are found only in remote, headwater streams. They are also small and short-lived. Males outnumber females, especially among sexually mature fish. The fecundity is lower than in fish of comparable size in Wisconsin and Canadian waters. Under present conditions, any increase in exploitation of the brook trout in the Park or damaging alteration of the habitat might have serious consequences for the remanent populations.
Studies on two hemoflagellates of fish were carried out to determine biological parameters: host range, vector relations, in vivo culture, in vitro culture, pathogenicit, and cryogenic preservation.
In epizootics of channel catfish virus diseasse (CCVD) at four widely separated fish farms in 1968, affected fry and fingerlings spiraled, hung in a vertical position with head at the surface, or were distressed. In various combinations were edema, hemorrages, and anemia. The disease had a peracute to acute course, and stress to the fish preceded most epizootics. The virus induced formation of syncytial cells in affected cultures, which is considered at present to be of diagnostic significance. Secondary bacterial infections were found in fish with CCVD. Columnaris infection masked the symptoms of the virus disease.
The 1970 fall chinook salmon feeding trials indicated that dry pelleted diets were equal to moist pelleted diets with similar formulations. A superior diet was produced by reducing the ratio of dried whey product and wheat germ meal to 1:1 and eliminating cottonseed meal. This formulation feed at a 45-percent protein level was more efficient than other protein levels fed. Growth was not reduced when the soybean oil supplement was lowered from 6 to 2 percent of the diet. Two corn distillers' products that were substituted as partial replacements for dried whey product did not enhance fish growth. Storage of the Abernathy dry pellet at room temperature did not alter the nutritional adequacy of the diet.
A spawning and incubation channel constructed in 1959 on Abernathy Creek near Longview, Washington, has been used for seasons to incubate fall chinook salmon and chum salmon eggs. Survival of eggs from both species was higher than reported for other channels and controlled-flow projects. Studies included effects of sedimentation, egg planting density, and stage of egg development at planting on survival. In early experiments sediment in the upper sections substantially reduced survival. In later experiments, after the construction of a sand trap and settling chamber, survivals significantly increased.