Hale Whales: Target reproduction numbers and sensitivity analysis for Resident Killer Whales
Date
2021-08-10
Authors
Hobson, Bronwyn
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Abstract
We used two existing population projection matrix models of female resident killer whales (Orcinus orca), the target reproduction number framework developed by Lewis et al.in 2019, and sensitivity analysis to determine target reproduction numbers and identify key parameter values to aid in population recovery strategies. From the earliest model, proposed by Brault and Caswell in 1993, we determined the net reproductive value for the combined Northern and Southern resident killer whale (NRKW and SRKW) populations from 1973-1987 to be R0 = 2.01. We also determined closed form and numerical expressions for target reproduction numbers targeting survival probabilities for the first three life stages of the model. For the most recent model, proposed by Vélez-Espino et al.(2014),using data from 1987-2011, we found the net reproductive value for the SRKW population to be R0 = 1.41. After performing a sensitivity analysis on each net reproductive value (R0), we found that survival probabilities of juveniles and reproductive females were key population parameters to aid in population growth and recovery.
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Keywords
target reproduction numbers, Orcinus Orca, matrix population model, Lefkovitch model, sensitivity analysis, net reproductive value