Toward Metapopulation Ecology of Coral Reef Fishes
Marine metapopulations occur where local populations of sedentary adults are replenished by offspring that disperse between those populations. Understanding metapopulation dynamics is clearly important for marine conservation (e.g., design of marine reserve networks) and management (e.g., stock boundaries and dynamics). My lab has examined population dynamics of coral reef fishes in the Bahamas at three spatial and temporal scales in an effort to link local dynamics with processes operating at the metapopulation level: (1) patches over weeks, which provide insight on the behavioral mechanisms of local demographic density dependence; (2) reefs over years, which provide evidence of whether or not local density dependence scales-up to reef-scale population regulation; and (3) islands over years (and beyond), which provide the relationship between local demography and larval dispersal, what we call “demographic connectivity.” We have found that (1) predation, often interacting with competition, is a common mechanism of local density dependence; (2) local density dependence does indeed result in population regulation at the reef scale; and (3) only by integrating measures of local larval production with genetic measures of larval dispersal could we accurately estimate the level of demographically meaningful connectivity that allows the regional metapopulation to persist. The challenge for the future is to fully integrate (a) knowledge of local ecological processes with (b) knowledge of larval dispersal from population genetics and oceanography with (c) knowledge of human uses of marine resources from social sciences. This grand synthesis will provide holistic understanding of marine metapopulations and metacommunities for more effective fisheries management and conservation.
MARK HIXON is the Sidney and Erica Hsiao Endowed Professor of Marine Biology at the University of Hawai‘i. He studies the ecology and conservation biology of coral reefs, especially involving fishes, focusing on enhancing ecological resilience against ocean warming and invasive species. Mark was honored in 2004 by the Institute for Scientific Information Citation Index as the most cited author on coral-reef ecology in the United States. A Fulbright Senior Scholar and Aldo Leopold Fellow, among other awards, he serves on the editorial boards of several scientific journals. Mark is past chair of the U.S. Marine Protected Areas Federal Advisory Committee, and the Ocean Sciences Advisory Committee for the U.S. National Science Foundation. His public outreach includes TED talks and TV appearances.