Table 2 Summary of the baseline estimates for parameters describing threats to Southern Resident killer whales, and the ranges considered in sensitivity testing
From: Warning sign of an accelerating decline in critically endangered killer whales (Orcinus orca)
Input parameter | Baseline (current) | Range tested | |
|---|---|---|---|
Prey impacts | Low | High | |
Prey abundance (index relative to long-term mean) | 1.0 | 0.5 | 1.5 |
Modeling demographic consequences of anthropogenic threats | |||
Climate change: percent decline in Chinook abundance over 40 years | No climate change impacts on prey | No decline in prey | 90% decline over 40 years |
Changes in Chinook size years to 8% decline | No decline | 20 y | 60 y |
Noise (percent of feeding time with disturbance) | 85% | 0% | 100% |
Contaminants | |||
Accumulation rate | 2 ppm/y | 0 ppm/y | 4 ppm/y |
Impact on calf survival (logistic slope) | −0.02 | −0.01 | −0.03 |
Half-life of PCBs in environment | No decline | 25 y | 75 y |
Total equivalents of PCBs plus other contaminants | 1.0 | 1.0 | 2.0 |
|---|---|---|---|
Other threats | |||
Direct human-caused mortality (potentially preventable) | 28.3% of deaths (included within annual mortality) | No reduction | All 28.3% of natural mortality prevented each year |
Inbreeding impact (lethal equivalents/diploid) | 6.29 LE | 0 LE | 12 LE |
Variance in male breeding success (sampled from beta distribution with mean=0.4) | SD = 0.4 | SD = 0.3 | SD = 0.5 |
Fishery reductions, closures, or relocations | No increase in percentage of Chinook available to SRKW | 3% increase | 25% increase amplified by another 40% improvement in size over 50 years |
Oil spill | None | Small: 1.08% frequency; 12.5% mortality Large: 0.21% frequency; 52% mortality | Small: 2.16% frequency Large: 0.42% frequency |
