A Comparison of the Removal and Mark-Recapture Methods of Population Estimation for Juvenile Coho Salmon in a Small Stream

Abstract

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.

Electrofishing — Theory and practice with special emphasis on salmonids

“…This time may vary widely depending on species, size, temperature, electric field strength, skill of the fisherman etc. Peterson and Cederholm (1984), working with juvenile coho salmon, found that catchability returned to acceptable levels after a 1 hour time lapse, but that it did not quite equalize even after 24 hours. If the catchability is reduced as a result of handling, r will be below expectation and the population size y therefore overestimated.…”

Brook Trout Removal as a Conservation Tool to Restore Eagle Lake Rainbow Trout

“…In addition, due to lower electrofishing efficiency for small fish (Bohlin et al 1989), age-0 brook trout are difficult to capture. Bogard Spring Creek had deep undercuts, high quantities of large woody debris, and in some areas, overhanging vegetation, which probably further lowered the removal efficiency for small fish (Peterson and Cederholm 1984;Shepard and Nelson 2002). However, as recommended by Kulp and Moore (2000), removals were delayed until late summer to allow age-0 brook trout to grow to larger sizes, thus increasing their susceptibility to electrofishing while water temperatures were still warm.…”

Amphibian molecular ecology and how it has informed conservation

“…Many amphibians are difficult or impossible to observe directly in the field: most species are nocturnal, and the vast majority spend significant portions of their lives underwater, underground, or in otherwise cryptic habitats. Information regarding population size and landscape use by animals has traditionally been gathered through direct observation (Arnason 1973;Peterson & Cederholm 1984;Johnson et al 2001), but these methods are often not feasible for amphibian population biologists. Genetic data are relatively easy to collect, especially for amphibian species that gather in breeding pools where entire cohorts can often be sampled nondestructively with a relatively minimal effort (Polich et al 2013).…”