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Marine Biology & Ecology

From a decade of living and conducting field work in Belize, Dr. Heyman has developed what he calls the "multi-species promontory hypothesis". This hypothesis basically states that many species of reef fishes preferentially select the waters above the tips of reef promontories to aggregate in large schools for the purpose of spawning. In many species (particularly snappers and groupers), spawning is confined to only a few days a year, meaning that the effort must take advantage of the most advantageous conditions to maximize the likelihood that their offspring survive. These reef tip promontories are situated adjacent to very deep offshore waters and often have unique current and circulation patterns that improve survival rates of the developing fish larvae and promote successful settlement and recruitment of local and regional fish populations.

Heyman and Kjerfve (2008) illustrates this phenomenon at Belize's Gladden Spit, showing that at least 17 species of large, commercially important reef fishes spawn within a 6-ha area at a reef promontory tip at Gladden Spit, Belize. The physical oceanographic conditions at Gladden Spit are unique when compared to adjacent areas. Dr. Heyman is now developing a more complex model built upon data from 20 other similar locations elsewhere in the Caribbean. The purpose of this effort is to from an evolving and complex picture of the physical / biological relationships between geomorphology, ocean currents, and the reproductive biology of many reef fish species.

Through partnership and collaboration, the Marine & Coastal Geography Group at Texas A&M University hopes to expand these studies throughout Belize and across the Caribbean in order to characterize and untangle the subtle nuances of species assemblages and their associated physical and environmental cues. This work serves as the basis for the design of regional marine reserve networks that encompass multi-species spawning aggregation sites, thereby providing crucial protections and management efforts when most large reef fishes are at their most vulnerable to being captured. This important work is joined by Dr. Jay Rooker at Texas A&M - Galveston to evaluate the connectivity between reef fishes spawning sites and juvenile habitats using natural tracers (e.g. stable isotopes in otoliths) and tagging studies. We have a proposal pending that would support this work for 4 years.

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