Population Dynamics of Two Coral Reef Fishes: An Empirical and Modeling ApproachEPA Grant Number: U915834
Title: Population Dynamics of Two Coral Reef Fishes: An Empirical and Modeling Approach
Investigators: Wilson, Jacqueline A.
Institution: University of Florida
EPA Project Officer: Lee, Sonja
Project Period: August 1, 2000 through August 1, 2003
Project Amount: $81,661
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems
The main goals of the research study are to: (1) quantify the effects of density-dependence and age-class interactions on the dynamics of two coral reef fishes (the sharknose goby, Gobiosoma evelynae, and the broadstripe goby, G. prochilos); (2) investigate spatial variation in habitat quality, or the strength of density-dependence, and determine its effects on goby population dynamics; and (3) use the field data to develop and parameterize a stage-structured population model that will be used to quantify the relative importance of processes occurring during different life-history stages.
The proposed field work will consist of two parts spanning over 3 years (May-August 2000-2003), and is being conducted in St. Croix, United States Virgin Islands. Patch reefs will be surveyed to quantify spatial and temporal variation in settlement of gobies. These surveys will identify habitats that consistently support higher numbers of fish relative to other areas (i.e., identify habitats that differ in quality). In addition to surveys, during the three field seasons, large, manipulative field experiments will be conducted to test for differences in habitat quality among coral heads and to quantify the effect of resident fish on settlement (i.e., quantify within and between age-class competition and the effect of density-dependent settlement), growth, and survival within different quality habitats. The final part of this study will involve the development of a discrete-time, matrix-based, stage-structured population dynamics model to evaluate how density-dependent settlement and post-settlement survivorship of different age-classes will affect the population dynamics of gobies in habitats varying in quality. This relatively simple modeling approach will be used to evaluate the dynamics on particular coral heads that differ in their strength of density-dependence and give some idea of which life history stage is most sensitive to density-dependent survivorship. The model also will indicate which life history transition will contribute the most to the growth rate of the populations and which transition is most sensitive to perturbations. The demographic parameters in the model will be the input of settlers and survivorship of individuals through each stage with a time step of 1 lunar month, which is the time between settlement pulses. The model will separate the adult reproductive stage, juveniles, and settlers, and incorporates density-dependent survival for each life stage. The transition to different stages will be modeled as a decreasing function of density for all three stages, and a Beverton-Holt survivorship function will be used to define this relationship. Population equilibria and their associated stabilities will be examined as a function of the different parameters in the model. The stability analysis will be of particular interest in terms of understanding how varying strengths of density-dependence will affect equilibrium densities.
The discrete-time, matrix-based, stage-structured population dynamics model will be used to evaluate the dynamics on particular coral heads that differ in their strength of density-dependence and give some idea of which life history stage is most sensitive to density-dependent survivorship. The model also will indicate which life history transition will contribute the most to the growth rate of the populations and which transition is most sensitive to perturbations.