2002 Progress Report: Determinants of Small-Scale Variation in the Abundance of the Blue Crab Callinectes Sapidus

EPA Grant Number: R827072C016
Subproject: this is subproject number 016 , established and managed by the Center Director under grant R827072
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Alabama Center For Estuarine Studies (ACES)
Center Director: Shipp, Robert L.
Title: Determinants of Small-Scale Variation in the Abundance of the Blue Crab Callinectes Sapidus
Investigators: Aronson, Richard B. , Moody, Ryan M.
Institution: University of South Alabama
EPA Project Officer: Packard, Benjamin H
Project Period: August 1, 2002 through December 3, 2003
Project Period Covered by this Report: August 1, 2002 through December 3, 2003
RFA: Alabama Center For Estuarine Studies (ACES) (1999) RFA Text |  Recipients Lists
Research Category: Targeted Research


The overall objective of this research project is to determine if local variations in the population densities and predatory activities of the blue crab Callinectes sapidus in the Mobile Bay estuary can be explained by local prey abundance. The abundance of blue crabs on large scales is influenced in different situations by such factors as larval supply, postsettlement mortality, predation, competition, cannibalism, and food supply, separately and in combination. Because the predatory fish that eat blue crabs range over large spatial scales, one simple a priori hypothesis to explain differences in abundance at this small scale is that abundance is related to the availability of food; at this scale, bottom-up effects should be more important than top-down effects.

This project will test one trophic linkage for bottom-up control of blue crab abundance on small spatial scales: the relationship of Callinectes and Littoraria, one of its principal prey species in the intertidal salt marshes of Mobile Bay (West and Williams, 1986) and elsewhere (Hamilton, 1976; Schindler, et al., 1994; and references therein). The study proposed here will: (1) test whether densities of Callinectes are positively related to densities of Littoraria; (2) test whether predation by Callinectes on Littoraria is density dependent; and (3) evaluate two simple, indirect methods of population estimation for blue crabs, which are based on the effects of the crabs on Littoraria populations.

To formally articulate the hypotheses to be tested in this study, it is necessary to define two aspects of predator-prey relationships: predation potential and predation pressure (Aronson, 1987; 1989). Predation potential is defined as the rate at which the prey of interest—Littoraria in this case—would be consumed were they readily available to predators. Predation pressure is defined as the natural frequency of attacks by predators on their prey. Predatory attacks can further be categorized as lethal or sublethal, a point that will become important in assessing predation pressure. If predation by blue crabs on Littoraria is density dependent, then dense populations of periwinkles, on a per capita basis, should experience greater predation potential and greater predation pressure than sparser populations. Predator abundance, predation potential, and predation pressure, therefore, should be correlated with each other. This would mean that predation potential and predation pressures, which are relatively simple to measure, should predict the abundance of Callinectes, which is more difficult to assess accurately (e.g., with baited traps that can attract crabs from outside the habitat). Listed below are the hypotheses to be tested in this study.

Abundances of Blue Crabs and Marsh Periwinkles

Hypothesis. Population densities of Callinectes are positively related to population densities of Littoraria.

Null Hypothesis. Population densities of Callinectes and Littoraria are not positively related.

Predation Potential and Predation Pressure

Hypothesis. Per capita predation potential and predation pressure on Littoraria are greater in habitats with higher population densities of Callinectes.

Null Hypothesis. Predation potential and predation pressure are not positively related to predator abundance.

Progress Summary:

To test the aforementioned hypotheses, we will measure five parameters: (1) population densities of Callinectes; (2) population densities of Littoraria; (3) predation potential, which will be assessed by tethering experiments with Littoraria; (4) predation pressure, which will be estimated from sublethal injuries (repaired shell cracks) in Littoraria populations; and (5) densities of Spartina shoots as they serve as an escape route for Littoraria from the water, and thus from predators. These parameters will be measured at two locations, Airport Marsh, Dauphin Island, and Point aux Pines, Bayou la Batre. Each location will consist of a putatively high and low predation site (four study sites in all).

Future Activities:

The field work is scheduled to start in March 2003. The proposed methodology has been tested and refined to ensure the effectiveness of the sampling techniques and equipment. The experimental and sampling design require that blue crabs are present within the study sites in high abundance, and will be conducted from March to November 2003.

Supplemental Keywords:

bottom-up effects, abundance, Callinectes sapidus, Littoraria irrorata, salt marsh, Spartina alterniflora, predation, predatory fish, predator-prey relationship, predation potential, predation pressure, baited traps, crabs, sublethal injury, trophic linkage, ecosystem, ecosystem protection, environmental exposure, risk, geographic area, water, aquatic ecosystem, estuarine research, chemical engineering, chemistry, ecology, ecological effects, human health, ecological indicators, assessment, indicators, environmental chemistry, Alabama, AL, artificial reef design, coastal ecosystem, coastal environments, estuaries, estuarine waters, fishery sampling, human modifications, land use, water use., RFA, Scientific Discipline, ECOSYSTEMS, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Aquatic Ecosystems & Estuarine Research, estuarine research, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Restoration, Aquatic Ecosystem, Ecological Effects - Environmental Exposure & Risk, Aquatic Ecosystems, Terrestrial Ecosystems, Habitat, Ecological Monitoring, Ecology and Ecosystems, Aquatic Ecosystem Restoration, coastal ecosystem, water use, watersheds, endangered species, Blue Crab Callinectes Sapidus, estuaries, predators, Alabama (AL), coastal environments, Alabama estuaries, ecosystem, conservation biology, environmental indicators, estuarine waters, water quality, human modifications

Relevant Websites:

http://www.southalabama.edu/aces/ Exit
http://www.disl.org Exit

Progress and Final Reports:

Original Abstract
  • 2003
  • Final

  • Main Center Abstract and Reports:

    R827072    Alabama Center For Estuarine Studies (ACES)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827072C001 Fluorescent Whitening Agents As Facile Pollution Markers In Shellfishing Waters
    R827072C002 Red Snapper Demographics on Artificial Reefs: The Effect of Nearest-Neighbor Dynamics
    R827072C003 Stabilization of Eroding Shorelines in Estuarine Wave Eliminates with Constructed Fringe Wetlands Incorporating Offshore Breakwaters
    R827072C004 Interaction Between Water Column Structure and Reproduction in Jellyfish Populations Of Mobile Bay (SGER)
    R827072C005 Effects of Variation in River Discharge and Wind-Driven Resuspension on Higher Trophic Levels in the Mobile Bay Ecosystem
    R827072C006 Results of Zooplankton Component
    R827072C007 Benthic Study Component
    R827072C008 A Preliminary Survey of Macroalgal and Aquatic Plant Distribution in the Mobile Tensaw Delta
    R827072C009 Fisheries-induced changes in the structure and function of shallow water "nursery habitats": an experimental assessment
    R827072C010 Effects Of Variation in River Discharge and Wind-Driven Resuspension on Lower Trophic Levels of the Mobile Bay Ecosystem
    R827072C011 Evaluation of Alabama Estuaries as Developmental Habitat for Juvenile Sea Turtles
    R827072C012 Effects of Salinity Stress on Natural and Anthropogenically-Derived Bacteria in Estuarine Environments
    R827072C013 The Role of Land-Use/Land-Cover and Sub-estuarine Ecosystem Nitrogen Cycling in the Regulation of Nitrogen Delivery to a River Dominated Estuary; Mobile Bay, Alabama
    R827072C014 Environmental Attitudes of Alabama Coastal Residents: Public Opinion Polls and Environmental Policy
    R827072C015 Synthesis and Characterization of an Electrochemical Peptide Nucleic Acid Probe
    R827072C016 Determinants of Small-Scale Variation in the Abundance of the Blue Crab Callinectes Sapidus
    R827072C017 Effects of Estrogen Pollution on the Reproductive Fitness of the Gulf Pipefish, Syngnathus scovelli
    R827072C019 A Model for Genetic Diversity Aquatic Insects of the Mobile/Tensaw River Delta
    R827072C020 Evaluating Trophic Processes as Indicators of Anthropogenic Eutrophication in Coastal Ecosystems: An Exploratory Analysis
    R827072C021 Effects of Anthropogenic Eutrophication on the Magnitude and Trophic Fate of Microphytobenthic Production in Estuaries
    R827072C022 Characteristics of Ship Waves and Wind Waves in Mobile Bay
    R827072C023 Methods Comparison Between Stripping Voltammetry and Plasma Emission Spectroscopy for Metals in Mobile Bay
    R827072C024 Changes in Water Conditions and Sedimentation Rates Associated With Construction of the Mobile Bay Causeway
    R827072C025 Cold-Induced Hibernation of Marine Vibrios in the Gulf of Mexico: A Study of Cell-Cell Communication and Dormancy in Vibrio vulnificus
    R827072C026 Holocene Sedimentary History of Weeks Bay, AL: Human and Natural Impacts on Deposition in a Gulf Coast Estuary
    R827072C027 Shelter Bottlenecks and Self-Regulation in Blue Crab Populations: Assessing the Roles of Nursery Habitats and Juvenile Interactions for Shelter Dependent Organisms
    R827072C028 Predicting Seagrass Survival in Nutrient Enriched Waters: Toward a New View of an Existing Paradigm
    R827072C029 DMSP and its Role as an Antioxidant in the Salt Marsh Macrophyte Spartina alterniflora
    R827072C030 A Preliminary Survey of Aerial and Ground-Dwelling Insects of the Mobile/Tensaw Delta
    R827072C031 Natural Biogeochemical Tags of Striped Mullet, Mugil cephalus, Estuarine Nursery Areas in the North Central Gulf of Mexico
    R827072C032 Resolution of Sedimentation Rates in Impacted Coastal Environments Using 137Cs and 210Pb Markers: Dog River and Fowl River Embayments
    R827072C033 Investigation of the Use of Pulse Amplitude Modulated (PAM) Fluorometry as an Indicator of Submerged Aquatic Vegetation Health in Mobile Bay
    R827072C034 Influence of Invasive Plant Species in Determining Diversity of Aquatic Vegetation in the Mobile-Tensaw Delta
    R827072C035 The Influence of Shallow Water Hydrodynamics on the Importance of Seagrass Detritus in Estuarine Food Webs
    R827072C036 Food Web Interactions, Spatial Subsidies and the Flow of Energy Between the Mobile Bay Delta and Offshore Waters: A SGER Proposal to the Alabama Center for Estuarine Studies
    R830651C001 Meteorological Modeling of Hurricanes and Coastal Interactions: A Stability Study For Vertical Pressure Levels
    R830651C002 Characterization of Glycoprotein Cues Used by the Parasitic Rhizocephalan Barnacle Loxothylacus texanus To Identify Its Blue Crab Host, Callinectes sapidus
    R830651C003 Survey of Diamondback Terrapin Populations in Alabama Estuaries
    R830651C004 An Assessment of Environmental Contaminant Levels in Water and Dragonfly Larvae Tissues from the Mobile/Tensaw Delta