We examined the levels of retention and utilization of 945 coho salmon (Oncorhynchus kisutch) carcasses released experimentally into seven spawning streams on the Olympic Peninsula, Washington. Most carcasses were retained in the streams and in adjacent forests, few were flushed beyond 600 m. Organic debris caught and held many carcasses. Much of the fish mass was consumed by 22 species of mammals and birds. The distances that carcasses drifted appeared to be related directly to the occurrence of freshets and inversely to debris load and carnivore scavenging. The capacity of many streams and rivers to retain carcasses has probably been reduced by human activities. The importance of coho carcasses to populations of carnivores and to the dynamics of lotic food webs merits additional study.
Petersen mark‐recapture estimates were as much as 8% more accurate than several removal techniques in estimating known populations of juvenile coho salmon (Oncorhynchus kisutch) in a small stream. When applying the removal efforts in rapid progression, catchability declined successively. If the population was allowed to recover for at least 1‐hour, catchability returned to levels that allowed reasonable estimates of the true population sizes by either method, but catchability between exposures to current did not equalize even after 24 hours. The 95% confidence intervals around the Petersen estimates always included the true population size, whereas those provided by the removal techniques sometimes did not.
1985. The retention of coho salmon (Oncoshynchus kisutch) carcasses by organic debris in small streams. Can. J. Fish. Aquat. Sci. 42: 1222-1225.Twenty marked coho salmon (Oncoshynchus kisutch) carcasses were placed in each of nine small streams on the Olympic Peninsula of Washington during the fall-winter spawning period. Distribution of the carcasses in 500 m of stream below each release site was followed for 4 wk. One week after placement, 78 of the 180 carcasses were found in the nine study reaches; 80% were found in the first 200 m downstream of the release sites. A general positive trend was observed between the number of carcasses retained and the amount of debris in the stream channel (r = 0.61). Terrestrial animals rapidly consumed carcasses during the experiment, and removed many of them to the riparian zone.Cent quatre-vingt cadavres marques de saumon coho (Oncorhynchus kisutch) ont ete r6partis 6galement dans neuf petits csurs d'eau de la peninsule Olympique (Washington) pendant la periode de fraie en automne et en hiver. La distribution des cadavres sur 580 m en aval de chaque lieu de iicher a kt6 suivie pendant 4 sem. Une semaine apres leur Iicher, 78 des 180 cadavres snt 6te trouves dans les neuf secteurs 6tudi6s; $0 % ont 6te trsuv6s dans les 200 premiers metres en aval des lieux de kcher. On a observe une tendance positive gen6rale entre le nombre de cadavres retenus et la quantit6 de debris pr6sents dans le chenal (s = 0,611. bes animaux terrestres ont rapidement mange les cadavres au cours de ['experience et ont en amen6 un bon nsmbre dans la zone ripicole.
Tributaries of the Clearwater River, Washington, support substantial populations of overwintering juvenile coho salmon Oncorhynchus kisutch. In 1983, a 4-year study was begun to determine if holes blasted in the mud substrate by explosives and subsequently flooded by creation of a small low-head dam could enhance these habitats economically. After treatment, overwinter survival and growth of coho salmon increased significantly.
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