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C.V.W. Mahnken

Publications and source records attributed to C.V.W. Mahnken.

4 recordsLinked to original sources
USGS1999

Growth, smoltification, and smolt-to-adult return of spring chinook salmon from hatcheries on the Deschutes river, Oregon

The relationship between smoltification and smolt-to-adult return (SAR) of spring chinook salmon Oncorhynchus tshawytscha from the Deschutes River, Oregon, was examined for four release groups in each of three successive years. Fish were reared, marked with coded wire tags, and released from Round Butte Hatchery, Pelton Ladder rearing facility, and Warm Springs National Fish Hatchery. Smolt releases occurred in nearly the same place at similar times, allowing a direct comparison of SAR to several characters representing smolt quality. Return rates varied significantly among facilities, varying over an order of magnitude each year. The highest average SAR was from Pelton Ladder, the lowest was from Warm Springs. Each of the characters used as metrics of smoltification - fish size, spring growth rate (February-April), condition factor, plasma hormone concentration (thyroxine, cortisol, and insulin-like growth factor-I [IGF-I]), stress challenge, gill Na+,K+-ATPase activity, and liver glycogen concentration - varied significantly among facilities and seasonally within hatchery groups. However, only spring growth rate, gill ATPase activity, and plasma IGF-I concentration showed significant relationships to SAR. These characters and SAR itself were consistently lower for fish released from Warm Springs Hatchery than for fish from Round Butte Hatchery and Pelton Ladder. This demonstrates that differences in the quality of fish released by facilities may have profound effects on subsequent survival and suggests that manipulations of spring growth rate may be used to influence the quality of smolts released from facilities.

Oregon↗
USGS1987

Safe pre-release disease treatment with formalin for fall chinook salmon smolts

Standard formalin treatment (167 μL/L for 1 h) applied to presmolts and smolts of fall chinook salmon ( Oncorhynchus tshawytscha) 80, 62, 52, 38, 24, and 10 d prior to seawater exposure did not affect freshwater growth or survival during a 20-d period in seawater. There was no consistent effect of treatment on gill Na + , K + -ATPase activity.

Progressive Fish-Culturist↗
USGS1970

Tektite 1, man-in-the-sea project: Marine Science Program

The Tektite experiment was designed to provide data for a number of behavioral, biomedical, and engineering studies in addition to the marine sciences program. Conditions for some of these studies were not altogether compatible with the program for the marine sciences. For example, isolation imposed by human behavioral studies precluded physical contact with the surface team, even though such contact was physically possible and desirable for the conduct of the marine sciences program. Isolation also imposed on the scientific team the duty of all in-habitat maintenance, both scheduled and unscheduled, thereby taking substantial time from scientific research. In addition, between 10 and 20 percent of the waking time was devoted to performance of psychological tests required for the biomedical studies. Most of the experiments were directed toward detecting potentially adverse changes and thus were accepted as necessary and desirable. The only health problem to affect the scientific program during the dive was a minor external ear infection contracted by all the divers. Nonetheless, the experiment demon. strated, at least to our satisfaction, the advantages of underwater habitation and saturation diving for biological and geological research. A major advantage is the opportunity for continuous monitoring of organisms or processes. In addition, underwater habitation provides for considerably more research time in the water than surface diving or intermittent bottom dwelling, and this advantage increases greatly as the depth of habitation increases. Even in the relatively shallow depths at which Tektite 1 was conducted, the undersea team could spend appreciably more time at work in the water than their colleagues on the surface. Finally, Tektite 1 demonstrated that the scientist who lives in the sea need not have the extensive qualifications of a professional diver. Of the four scientists of the in-habitat team, only Crew Chief Waller was so qualified; the other three had used scuba as a research tool, but on a relatively limited basis. Any healthy, well-conditioned marine scientist with a basic diving background is capable of extending his research into the shallow sea on a full-time basis. It is hoped that many such scientists will in the future be able to utilize the undersea laboratory.

Science↗