Long-term trends in the age and size structure of marine fishes

Abstract

The phenotypic plasticity of marine fishes can generate demographic changes in response to harvesting, the environment, and interspecific interactions. Shifts in age and size can affect metrics of population viability related to reproduction, growth, and survival. This thesis involved the analysis of large-scale temporal trends in age and size structure of exploited fish stocks. In Chapter 1, the examination of 43 stocks allowed for the evaluation of sensitivity and response time in age structure to historic levels of fishing mortality. Significant responses were exhibited in 88% of stocks, attributed to fishing or management. Chapter 2 investigated changes in northwest Atlantic monkfish (Lophius americanus) size structure, finding a 48% reduction in body length over 55 years, with the average length of fish affected by survey gear, temperature, and depth. An improved understanding of the causes and consequences of these shifts improves our ability to predict and mitigate future changes