Age-specific mortality rates and causes of mortality in naturaloyster, Crassostrea virginica, populations

摘要

There are very few estimates of natural mortality rates in natural populations of oysters, Crassostrea virginica, (as opposed to abundant estimates from culture and tray type experiments). We offer two methods to estimate natural mortality rates over extended periods and multiple reefs systems for populations in the James River, VA under varying disease challenges. We convert size specific live and box data to age specific demographics, and then generate estimates of age specific mortality from either box ratio (#box / (#box + #live)) or inverse survivor ratios (Live(t) - Live (t + 1)/Live (t)). These are presented and compared with respect to oyster population density, prevalence and intensity data for Perk-insus marinus, and river flow data as a surrogate for salinity.