During 1990, a relatively high percentage of adult anadromous salmonids returning to the Snake River had marine‐mammal tooth and claw abrasions. From 1990 through 1993, annual incidence of these injuries ranged between 14.0 and 19.2% for spring–summer chinook salmon Oncorhynchus tshawytscha and between 5.4 and 14.2% for steelhead O. mykiss. Open wounds were observed on about one‐third of the fish with abrasions. Although these results suggest that predation by pinnipeds may be an important mortality factor for Snake River spring–summer chinook salmon, further research is needed to accurately define the magnitude of the predation.
ABSTRACT. Hematologic data gathered over a period of 4.8 years from 196 owl monkeys, Aotus trivirgatus, were analyzed to find if karyotypic differences existed. It was found that none of 30 animals of karyotypes K-I and K-VI developed hemolytic anemia, whereas 46 of 99 animals of K-II, K-III and K-IV did (p<0.005). Analysis of hemograms of normal owl monkeys showed that mean percent eosinophils varied markedly, K-I monkeys having lowest counts, 3.2 ~, and K-VI animals having the highest, 33 ~. These results establish that idiopathic eosinophilia and hemolytic anemia in this species are probably unrelated but susceptibility to both has a strong genetic component.
A system that allows anesthetization of juvenile salmonids before netting during a handling and marking operation is described. Our purpose for designing the system was to reduce or minimize any debilitating effects associated with these activities. When compared with smolts handled and marked in the traditional manner, use of the technique resulted in a significant reduction in the mortality of naturally migrating smolts of spring‐summer chinook salmon Oncorhynchus tshawytscha during a posthandling and marking seawater challenge performance test. The treatment resulted in lower, but not significantly lower, plasma cortisol levels; however, sample sizes may have been too small for statistical verification. With a little ingenuity, the technique should be adaptable to most smolt handling or marking operations.
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