Publication Date

2009-05-14

Availability

Open access

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Biology and Fisheries (Marine)

Date of Defense

2006-10-09

First Committee Member

Jerald S. Ault - Committee Chair

Second Committee Member

Su Sponaugle - Committee Member

Third Committee Member

James A. Bohnsack - Committee Member

Fourth Committee Member

Steven G. Smith - Committee Member

Fifth Committee Member

Nelson M. Ehrhardt - Committee Member

Abstract

The goal of this research was to develop statistically robust ecosystem-based approaches, while optimizing data acquisition on relatively unexploited fish species in South Florida reefs, i.e., parrotfishes, Family Scaridae, in Biscayne Bay (with seasonal roller frame beam trawl surveys, 1996-2000) and Florida Keys (with annual Reef Fish Visual Censuses, 1997-2001), by following these steps: (I) analysis of information gaps for the stocks, including systematics, biogeography, population dynamics, reproductive ecology, trophodynamics, habitat use, and fisheries dynamics of Western Atlantic parrotfishes; (II) determination of primary research objectives from prioritization in Step I; (III) determination of essential fish habitats, ontogenetic shifts, migrations, and reef-seagrass habitat, from integration of stratified sampling design for fisheries-independent surveys, habitat selection theory-based analyses, and length-based analyses; (IV) estimation of population dynamics and fisheries-specific parameters encompassing life history demographics from empirical data or comparisons to theoretical expectations adapted to local conditions; (V) simulation modeling of a realistic range of fishing scenarios and demographic characteristics to evaluate the efficacy of potential traditional fisheries and spatial management strategies; and (VI) application of sampling optimization procedures and fisheries ecology approaches. Four scarid species had an estimated combined abundance of ca. 36.8 x 106 individuals in the Florida Keys. Connectivity among seagrass beds, coral reefs and deep waters had three major patterns: seagrass dwellers, reef dwellers, with inshore-to-offshore ontogenetic , and a seagrass-reef connection, using Biscayne Bay as an important recruitment ground. Marine protected areas of the Florida Keys National Marine Sanctuary did not show effects on abundance, size composition or spatial distribution of any parrotfish studied. Simulations suggested relatively short longevities (5-10 years), moderate body growth curvature, high instantaneous natural mortality rates (0.3-0.6 y super minus one), and low annual survival rates (27-54%). Simulated estimates of fishing mortalities ranged from 0.3 to 0.6 y super minus one, indicating low levels of exploitation, but low Spawning Potential Ratios (SPR = 23.5-26%). Proposed potential exploitation based on a legal minimum size equal to their size at first maturity and fishing rates equal or below to their natural mortality should secure SPR values at 45-48%.

Keywords

Reef Fish Ecology; Marine Protected Areas; Essential Fish Habitat; Marine Ecosystem Management; Coral Reef Fisheries

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