Abstract: Harvesting models are based upon the ideology that removing large, old individuals provides space for young, fast-growing counterparts that can maximize (fisheries) yields while maintaining population and ecosystem stability. Yet, this compensatory density dependent response has rarely been examined in multispecies systems. We combined extensive datasets from coral-reef fisheries across a suite of Pacific islands and provided context to the universal assumptions of compensatory density dependence. We report that size-and-age truncation only existed for 49% of target coral-reef fishes exposed to growing fishing pressure. In contrast, many of the remaining species slowly disappeared from landings and reefs with limited change to their size structure (i.e., less or even no compensation), often becoming replaced by smaller-bodied sister species. To understand these remarkable differences, we next constructed phylogenies for dominant fish families and discovered that large patristic distances between sister species, or greater phylogenetic isolation, predicted size-and-age truncation. Isolated species appeared to have greater niche dominance or breadth, supported by their faster growth rates compared to species with similar sizes and within similar guilds, and many also have group foraging behavior. In contrast, closely related species may have more restricted, realized niches that led to their disappearance and replacement. We conclude that phylogenetic attributes offered novel guidance to proactively guide multispecies fisheries management and improve our understanding of ecological niches and ecosystem stability.

Biography: Dr. Peter Houk is a research professor at the University of Guam Marine Lab interested in coral-reef and fisheries ecology. He works in partnership with many governmental and non-governmental organizations throughout the Pacific, and in particular, Micronesia. His research focuses on the interplay between population ecology, conservation biology, and oceanography. He works with a variety of organisms and systems and is always seeking new collaborations. In Micronesia, his work aims to improve scientific frameworks to support and evaluate policies related to fisheries, climate change, land-based pollution and other human stressors. Website: https://www.uog.edu/ml/labs/houk.php