II. Fisheries

Separating the effects of environmental variability from the impacts of fishing has been elusive but is essential for sound fisheries management. As the fisheries management policy moved toward an ecosystem approach, it is important to understand interactive effects of fishing and climate. 

 Using 50-year long fish time series data collected from the California Cooperative Oceanic Fisheries Investigations surveys, we developed a novel approach to examine fishing effects on fish populations within the context of a changing environment by comparing exploited to unexploited populations. 

 We found that fishing had reduced resilience of fish populations facing environmental variability and elevated boom-and-bust of exploited populations. Such elevated variability was caused by fishing-induced age-truncation effects (ATE), which results in juvenescent populations with increasingly unstable population dynamics because of changing demographic parameters such as intrinsic growth rates. 

We also found that fishing forced exploited stocks to "put eggs in a single basket" and reduced spatial heterogeneity of exploited populations. We continue to investigate fishing effects on age structures of exploited populations from data, theoretical and field works aspects in a global scale.