A Technique for Enumerating Kokanee Salmon (Oncorhynchus nerka) Fry Migrating through Streams, with an Appendix for Processing Catch Data by IBM 360 Fortran IV Computer Programs

A technique for enumerating kokanee salmon (Oncorhynchus nerka) fry migrating downstream was developed in Meadow Creek (a tributary to the Duncan River and Kootenay Lake, B.C.) and was used to obtain an estimate of 10.06 million kokanee fry in 1968. The hyperbolic relation between the nightly mean catch per net per minute (C) and nightly probable error (E) as the percent of the nightly total was expressed by log E = −0.5703 − 0.4568 log C; E was largest at the beginning and end, and smallest at the peak of fry migration. E was also calculated as the percent of the seasonal total, and in 1968 was ± 5.8%. Of this total, ±0.7% was accumulated during April, when 6.4% of the migration occurred; ±3.9% was accumulated in May, when 82.2% of the migration occurred; and the final ±1.2% was accumulated in June, when 11.2% of the migration occurred. The variability m abundance of try and spacing of groups of fry are considered to be the most important factors controlling the magnitude of error.Some aspects of migratory behaviour of kokanee fry in Meadow Creek were revealed and their effects on estimates of abundance are discussed.A series of IBM 360 Fortran IV computer programs for processing catch data are also given in an appendix.