We describe a method of estimating the spawning escapement of coho salmon (Oncorhynchus kisutch) from capture–recapture data. Traditional capture–recapture analyses do not directly provide estimates of escapements; however, we show how simple modifications to the Jolly–Seber method can estimate the total number of fish returning to a river including those that enter and die between sampling occasions. Spawning runs of Pacific salmon were simulated and their escapements estimated using capture–recapture. The performance of the maximum likelihood estimators (MLEs), the censored MLEs, the constrained MLEs, and less-biased estimators in estimating the run sizes and providing estimates of precision were evaluated. Simulation results indicated that constrained MLEs provided the most appropriate estimates of escapement and that standard errors be computed using the large-sample variance formulae evaluated at these estimates. These methods were used to estimate the escapements of coho salmon to a small river on Vancouver Island in 1989 and 1990.

Groups of about 10,000 smolts of coho salmon Oncorhynchus kisutch were marked with one of two types of fluorescent tags: visible implant fluorescent filament (VIF) and visible implant fluorescent elastomer (VIE). Fish were also tagged with coded wire tags and adipose fin clipped to assess fluorescent tag retention and marine survival. Ocean recoveries were reported through the coastwide mark–recovery database. Returning fish were examined for the presence of tags, and survival and exploitation data were compared among groups. Fluorescent tags in approximately 90% of fish bearing them were easily seen in natural light. Probabilities of recovery, either in fisheries or spawning escapements after fisheries, and survival rates, did not differ significantly between coded‐wire‐tagged fish with and without fluorescent tags (either type). Short‐term losses of fluorescent marks were about 5%; long‐term losses between application and recovery were about 28% for VIE but were not statistically significant for VIF. Losses were attributed mainly to the inexperience of the people marking the fish, to handling related losses, and to problems with the catalyst in the elastomer.

Sixteen species and juveniles of four taxa of parasites (Myxosporea, 4; Monogenea, 1; Trematoda, 5; Cestoda, 4; Nematoda, 2; Acanthocephala, 2; Copepoda, 2) were encountered in 1550 sockeye salmon (Oncorhynchus nerka) smolts and presmolts examined from 15 Fraser River lakes, Nimpkish Lake on Vancouver Island, and Lake Washington, Washington State, U.S.A. The most common taxa were Diphyllobothrium sp. (spp.?) plerocercoids, Philonema agubernaculum, Eubothrium sp., and Proteocephalus sp. Various statistical techniques (K - nearest neighbour and cluster analyses based on Jaccard and percent dissimilarity matrices) were used to compare the parasite fauna in sockeye from the different lakes. K - nearest neighbour analysis demonstrated that considerable overlap existed among many of the studied lakes, whereas little overlap occurred among other lakes. Cluster analyses revealed similar faunas among some lakes within biogeoclimatic zones and lakes of similar trophic status. Cluster analyses also revealed parasites that tended to co-occur. Parasites with similar modes of transmission or geographic range tended to cluster together.

Uncertainty can be incorporated into area‐under‐the‐curve (AUC) and peak count estimates of salmon escapement by conducting replicate fish counts and developing independent escapement estimates over several years. We describe a bootstrap procedure that follows the trapezoidal AUC method and incorporates the uncertainty associated with fish counts, the shape of the spawner curve, observer efficiency, and residence time. However, the procedure does not incorporate all sources of uncertainty or address the problems posed by sparse surveys or nonzero first or last counts. For the peak count method, the procedure was modified to include the uncertainty from fish counts, observer efficiency, the expansion factor, and the timing of scheduled flights with respect to peak spawning activity. Data from spring‐run, stream‐type chinook salmon Oncorhynchus tshawytscha in the Nicola River, British Columbia, were used to demonstrate the procedures' applications. Replicate aerial spawner counts were similar and repeatable, and annual residence times were consistent over 4 years. The AUC escapement estimates were precise, reliable, and accurate when compared with independent mark–recapture escapement estimates, whereas the peak count escapement estimates were precise but less reliable and accurate. We expect that AUC escapement estimates calculated from the mean residence time of 4 years will be less biased (−8% to +5%) than peak count estimates from the mean expansion factor of 4 years (−14% to +21%). The procedures that we describe for incorporating uncertainty into AUC and peak count escapement estimation should enable fisheries biologists to more adequately assess changes in abundance and stock status.

Sockeye salmon (Oncorhynchus nerka) smolts were captured from the outlet streams of Cultus Lake, British Columbia, in 1985 and 1986, and from Fraser Lake, British Columbia, in 1986. Samples collected in 1985 were reared in salt water. Samples collected from each lake in 1986 were divided equally into two groups: one group was reared in fresh water, the other was maintained in salt water. Initially biweekly, and later monthly, subsamples from each group were examined for seven parasite taxa: Myxidium salvelini, Diplostomulum sp. metacercaria, Phyllodistomum umblae, Eubothrium sp. (immature), Proteocephalus sp. (immature), Neoechinorhynchus salmonis, and Salmincola californiensis. The maximum life-span was greater than the duration of the experiments (32–40 weeks) for all species in hosts reared in fresh water (except for S. californiensis, which was removed from all freshwater hosts). Survival of M. salvelini, P. umblae, and S. californiensis was reduced in hosts reared in sea water. No differences in survival of each of Diplostomulum sp. metacercaria, Eubothrium sp., Proteocephalus sp., and N. salmonis were observed between hosts held in fresh water or salt water. Implications for the use of these parasites as natural tags are discussed.