The application of certain techniques of fisheries statistics to an isolated population of brook sticklebacks, (Culaea inconstans) at Delta Marsh, Manitoba
Acere, Thaddaeus Olai
The field study was done during the summers of 1969 and 1970. Assumptions and several methods used for mark-recapture population estimates are discussed. Estimates of population size were computed by the modification of the Petersen method (Bailey, 1951) and the stochastic model of Jolly (1965). Results from the two methods were compared and neither gave consistently higher estimates. Confidence limits and standard errors for the estimates are provided. Survival rates, total mortality rates and instantaneous rates of natural mortality are computed, all of which are found to vary from one interval to the next. The largest biomass, based on estimated population size was found in September 1-5, 1969, when there was the greatest surge of yearlings into the estimable population size. Culaea inconstans in Delta Area, Lake Manitoba matures in the second summer of life, when between 29 and 65 mm in total length and one year of age. Spawning starts at the end of May after migration into the creeks and channels in the marsh. By June 11-12 the yearlings are under 20 mm in total length. The greatest part of growth is completed in the first summer of life. Fish set the first ring, a false check, in otoliths within the first month of life and the annual ring is set by adults on June 1 of the second summer of life. Aging of fish was done by reading otoliths and plotting length frequency histograms. Condition factor was found to be variable.