Mortality - Aggression and Starvation

Crab survival and population-level rates of mortality are primarily dependent on algorithms governing crab aggression and movement in response to environmental conditions. The average mortality rate (#.m$^{-2}$.hr$^{-1}$) over the entire estuary due to aggression by other crabs was $\approx 0$ between December to April, but increased with crab density both at the fine-level triangle and estuary scales during other times. 92.7% of all mortality was caused by aggression and only 6.9% was caused by starvation of small instar crabs that occurred primarily during February-March and August-September. The relative size of the attacking crab was always larger than the size of the killed crab, on average at least 1.7 times or more larger (Fig. B15). Other minor causes of death were asphyxiation due to a crab's inability to escape low DO waters (Appendix A.5.14) and crab's reaching their life expectancy.