12. Abundance and Sex Ratios of Parrotfish among Various Reef Sites of Calabash Caye, Belize

Abstract

Abundance and Sex Ratios of Parrotfish among Various Reef Sites of Calabash Caye, Belize

Donna K. McCullough, Ellen C. Tomlin, Kimberly T. Wright, Jill G. Schulze, Nancy E. Dalman

We investigated the sex ratios of parrotfish (Family Scaridae) at multiple reef sites off the coast of Calabash Caye, Belize. Parrotfish graze on reefs to consume tiny symbiotic algae living inside the coral and on larger reef algae that can overgrow and kill the coral. The growing coral competes with the algae for sunlight, so by feeding on the coral competitors, parrotfish play a key ecological role in reef health. We studies six different species of parrotfish; all are protogynic hermaphrodites that live in harem social systems. This means each fish begins life as an “initial phase” (IP) female and changes to a “terminal phase” (TP) male, which then controls a harem of IP females. Males must consume more food to support and maintain this transition; therefore we hypothesized more TP males than IP females would occur in deeper reefs, which generally have greater edible biomass than shallow reefs. We surveyed TP and IP ratios via established coloration differences along linear 20m transects on four reef sites that varied in depth with one being shallow, two intermediate, and one deep. The percentage of TP males ranged from 23-39% at the intermediate and deep sites, but was only 3% at the shallow site, supporting our hypothesis that TP parrotfish prefer food - rich deeper reef sites.