Swimming performance profiles, relating fish size to swimming time, were established for three strains of rainbow trout (Salmo gairdneri). No differences were found in slope of regressions; only in level at each size of fish. Swimming performances of New Zealand and Sand Creek strains did not differ, but were superior to the Manchester strain. In stamina results from 189-day-old fish from individual matings of seven strains and various crosses, similar strains and crosses had closely matching profiles whereas profiles of unrelated groups were variable. Comparison of slowest, average, and fastest growing fish within the New Zealand strain showed that swimming ability was not related to growth rate.

Hematology, blood chemistry, glycogen levels, and plasma protein composition were measured on samples of female, male, and precocious male fingerlings, male yearlings, and 2-year-old jack chinook salmon. Precocious male fingerlings varied from immature fingerlings in levels of total plasma protein, cholesterol, and various plasma protein fractions, and were more similar in characteristics to jack salmon and yearlings.

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Tests were made of the swimming ability of fall chinook salmon (Oncorhynchus tshawytscha) during and after yolk sac absorption. Two sources of fish were used: hatchery fish incubated and reared in constant‐temperature well water and migrants from an incubation channel supplied with creek water of variable temperature. Two testing procedures were used: impingement tests using a fixed screen and constant water velocities with percent impinged as the measure, and stamina tests using increases in water velocities at fixed intervals with time of displacement as the measure. As the fish developed, a period of reduced swimming ability occurred shortly before complete yolk sac absorption. The slump coincided with the period of peak migration from the channel and may be a cause of migration and an important factor in survival.

Identification of individual fish is often important in fisheries research and management. Marks to be used should be inexpensive, relatively permanent, easily applied, allow a great variety of marks, and not affect behavior and feeding. Finclipping, tagging, and branding often do not meet all of these requirements.Marine polychaete annelids marked with a commercial "caustic pencil" containing 40% silver nitrate and 60% potassium nitrate were identifiable for more than 30 days [2]. Silver nitrate marks were easily distinguished for at least 5 mo on eels (Anguilla anguilla) and different varieties of mirror carp (Cyprinus carpio) [1,3,4,5]. Results on the use of silver nitrate for marking channel catfish (Ictalurus punctatus) are reported here. MATERIALS AND METHODSAll fish in this experiment were marked with commercially available silver nitrate applicators, which consist of a round wooden stick, 15 cm long by 2 mm thick, with a medicated tip about 8 mm long that is impregnated with a preparation of 75% silver nitrate and 25% potassium nitrate. These applicators were obtained from a veterinarian at a cost of 5 cents apiece, in lots of 100. However, they can be purchased from veterinarian supply companies for about 2 cents apiece.Several dozen channel catfish ranging in weight from about 200 to 350 g were used with 250 various combinations of marks. Marked fish were usually maintained in individual aquaria. I narcotized a few fish with electric shocks before marking them, to study discrete marking on rigid fish; however, most fish were hand-held in air and not anesthetized. The areas of the fish tested for marking included the sides, ventral surface, fins, and head. Dipping the applicator in water before the mark was applied (as per instructions) appeared to reduce the effectiveness of silver nitrate. Better marks resulted when the moisture on the fish activated the chemicals. RESULTS AND DISCUSSION The caustic chemicals immediately produced a broad white mark at the contact point of the applicator with the fish (fig. 1). This white mark faded to a thinner, pale mark after about 6 h. This pale mark (fig. 2) resulted from cauterization of the skin by the caustic action of the silver nitrate and was relatively permanent. The potassium nitrate apparently sterilized the mark area and prevented infection. Small pieces of skin were found near the area of cauterization for several days after marking, and elevated scar tissue was observed on some marked fish --particularly on those marked on the ventral surface. Marks on the sides of fish were most easily recognized, due to the contrast between the dark THE PROORESSIVE FISH-CULTURIST