Estimation of mortality coefficients and survivorship curves for minke whales (Balaenoptera acutorostrata) in Korean waters

Abstract

Population ecological characteristics of growth and mortality play an important role in understanding the population dynamics of marine mammals. The instantaneous coefficients of natural and bycatch mortality were estimated for minke whales (Balaenoptera acutorostrata) in Korean waters using a population assessment model composed of bycatch and abundance data. The survivorship curve of this population was fitted to the data, and then the curve was revised using age-specific relative bycatchability coefficients (q _t ). Instantaneous coefficients of natural and bycatch mortality of minke whales were estimated as 0.024/year and 0.076/year, respectively, and from this the survival rate was estimated as 0.905. This estimated survival rate was comparable to other cetaceans in other regions. The q _t for this population ranged from 0.020 to 0.193. The revised survival rates were higher when the q _t was taken into account. The mortality coefficient, survival rate, q _t and survivorship curves had not previously been determined for minke whale in this area. This estimate could serve as fundamental information to assess the status of this population and for conservation and rational management.

Keywords:

• mortality coefficient
• survival rate
• age-specific relative bycatchability coefficient
• survivorship curve
• minke whale

Acknowledgements

We wish to acknowledge the many volunteers who reported the bycatch of minke whales in Korean waters. This work was financially supported by the Cetacean Research Institute of National Fisheries Research and Development Institute, Republic of Korea.