Influence of habitat on density, species richness, and size distribution of groupers in the upper Florida Keys, United States of America and central Bahamas

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)



First Committee Member

Kathleen M. Sullivan - Committee Chair


The influence of habitat on the density, species richness, and size distribution of groupers (Pisces: Serranidae) was studied in the upper Florida Keys, USA and the Exuma Cays Land and Sea Park (ECLSP), central Bahamas. Four reef types were examined: relict spur and groove; high-relief spur and groove; relict reef flat; and patch reefs.The size distribution of groupers differed among reef types with the majority of grouper observed on deeper (10-20 m), low-relief, relict spur and groove reefs consisting of smaller individuals (5-15 cm), whereas the majority of individuals on shallower ($$35 cm). There were significantly more larger individuals on reefs protected from spear-fishing than on unprotected reefs. There were no significant differences in the density of groupers related to the time of day surveys were conducted. Seasonal differences in density were found for graysby (Cephalopholis cruentata) in two sites and for black grouper (Mycteroperca bonaci) in patch reefs. There were significant differences in the density of individual grouper species among reef types. For most species, these differences were related to the geomorphology of the reef type and not to any specific quantifiable habitat variable. Red grouper density was significantly influenced by both the type and biotic composition of the reef surveyed. Grouper were found to preferentially utilize space within a site with particular habitat features. The presence of a cleaning station significantly affected the space utilization of groupers. Habitat influences the behavior and space utilization of groupers on a particular reef, but, in general, not grouper density. Each reef type has a grouper assemblage which differs in density, species composition, and size distribution. The habitat preferences of graysby, black grouper, and red grouper (Epinephelus morio) are examined in detail. The use of marine fishery reserves as a management tool for replenishing grouper populations is examined.


Biology, Ecology; Biology, Oceanography; Agriculture, Fisheries and Aquaculture

Link to Full Text


Link to Full Text