USE OF COHORT ANALYSIS TO ESTIMATE ABUNDANCE, RECRUITMENT AND SURVIVORSHIP OF NEWFOUNDLAND MOOSE

Abstract

The use of a fisheries model (CAGEAN) to perform cohort analysis of Newfoundland age-specific moose kill data was investigated. Cohort analysis was used to estimate temporal changes in moose population abundance, recruitment, and age-specific survivorship and vulnerability to hunting. Different populations displayed 1 to 3 cyclic fluctuations between 1966 and 1991 with density varying from 0.5 (1973) to 4.0 moose/km² (1990). Cohort abundance estimates generally compared favourably with aerial survey results, and indirect indices determined from hunter questionnaires. Sensitivity analysis indicated that abundance estimates were most sensitive to changes in natural mortality. Cohort analysis was less reliable as an estimator of calf recruitment and the method cannot directly measure productivity or early calf survival. Estimates of age-specific vulnerability to hunting and age-specific survivorship for males and females were compared for two time periods. Calves were least vulnerable to hunting, yearlings were the most vulnerable and vulnerability increased with age for males over 7 years old and females over 10 years old. The major age-specific Differences in mortality patterns for female moose between two time periods was the low mortality rate of calves (4%) during the 1978-80 period subsequent to 7-9 years of uninterrupted population growth. Generally, the fisheries computer model provides useful demographic information for research and management purposes but important limitations exist.