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CURRENT PROJECTS
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Coastal Alabama Breakwaters
Shorelines at the interface of marine and terrestrial biomes are one of the most degraded and threatened habitats in the coastal zone because of their sensitivity to sea level rise, storms, and increased utilization by man. Previous efforts to protect shorelines have largely involved introducing bulkhead and seawalls to dampen or deflect erosive wave energy, which detrimentally impact the nearby intertidal habitats that many marine organisms rely on. Subtidal oyster reefs are one example of natural reefs that could be an ideal structure for shoreline stabilization because of their breakwater capability, and could possibly even facilitate shoreline expansion by reducing wave energy and allowing shoreline vegetation to persist or expand.
Beyond shoreline stabilization, living reefs may provide additional ecosystem services such as habitat for resident species of shellfish and finfish, providing feeding resources for transient fishes, and improved water quality via the filter-feeding bivalves. Currently, the Fisheries Ecology Lab and the Marine Ecology Lab are evaluating multiple configurations and scales of breakwater oyster reef restoration projects along coastal Alabama. Master’s student Steven Scyphers is carrying out monthly surveys of fish and mobile invertebrate response to the restored oyster habitat through seining and gillnetting. Because oyster reefs provide habitat for small fishes and invertebrates, which support large fish species, we expect to find higher abundance and biomass of fish and invertebrates at the oyster reefs than at corresponding control sites with no biogenic structure. Results from this study and others could provide support for oyster reef and other living shoreline restoration practices. |
Alabama Oyster Reef Restoration
In addition to the multimillion dollar US fishery they support, oyster reefs are a critical component of healthy estuaries fulfilling several key ecological functions. Their unique role as both an exploitable fishery and an essential habitat provides a challenge to conservation and management. Oyster reefs provide habitat for finfish & shellfish. They also stabilize shorelines and remove suspended solids and phytoplankton from the water column. Many commercially important fisheries species are enhanced by the presence of oyster reefs. Their unique role as both an exploitable fishery and an essential habitat provides a challenge to conservation and management of oyster reefs.
In 2002, the University of South Alabama initiated a multi-disciplinary, multi-year program to enhance and restore oyster habitat in Alabama coastal waters. The Alabama Oyster Reef Restoration Program, funded by the National Marine Fisheries Service through congressional appropriation in 2002 and 2003, is designed to build upon previous and current oyster reef restoration/enhancement efforts within the State of Alabama. Although some areas of Mobile Bay (e.g., Cedar Point) still support oyster reefs of varying sizes, from a few square meters to tens of acres, overall coverage of oyster reefs in Mobile Bay has decreased over the last century. Numerous factors, many of which are of anthropogenic origin (e.g., destructive harvesting practices, poor water quality, and shrimp trawling), have contributed to this decline. As a result of these and other stressors, many historically productive areas for oysters (e.g., Bon Secour, Fish River) currently have few live oyster reefs present.
The three principle objectives of the Alabama Oyster Reef Restoration Program are (1) to develop the scientific understanding necessary to direct current and future oyster restoration and enhancement in Alabama coastal waters, (2) to assist in the development of a long-term strategy for sustained productivity of Alabama�s oyster resources and the associated ecological benefits that accrue from healthy oyster-based habitat, and (3) to provide this information to state and federal management agencies, the fishing industry and the general public through outreach activities. To address these objectives, the Alabama Oyster Reef Restoration Program has three major components: (1) large-scale reef creation activities performed in cooperation with the Alabama Department of Conservation, (2) targeted research projects performed by individual University of South Alabama researchers and (3) public outreach and communication.
Artificial Reefs as Restoration Tools for Alaska's Coastal Waters
Artificial reefs are widely utilized as devices for enhancing fish habitat and have demonstrated potential as marine habitat restoration tools. Pre-planned artificial reef designs integrate biology and engineering to create specific habitats that mimic natural habitat. These artificial structures encourage settlement by plants and benthic invertebrates, and provide both shelter and a forage base for fish. In May 2006, Alaska�s first artificial reef system was installed near Whittier in western Prince William Sound. The reef is comprised of pyramidal concrete structures called Fish Havens and spherical concrete structures called "Reef Balls". Master's student Brad Reynolds is surveying the artificial reef for two years to assess how it influences the immediate marine environment in comparison to natural rocky reef sites. The study will utilize intensive dive surveys, fish trap deployments, hook and line surveys, and stationary cameras to monitor and assess the efficacy of artificial reefs as a fish habitat enhancement tool with potential for future marine habitat restoration and enhancement projects in nearshore Alaskan waters. Project partners include the Dauphin Island Sea Lab, University of South Alabama, Prince William Sound Science Center, NOAA Restoration Center, and NMFS Habitat Conservation Division.
The red drum (Sciaenops ocellatus) fishery in the Gulf of Mexico (Gulf) is considered to be a success story with regards to returning a once depleted stock to a more favorable status. In 2004, and after eighteen years of intense management, it was determined that this fishery was no longer experiencing overfishing; however, because of a total ban on harvest in federal waters of the Gulf, little is known about the age structure of the adult population and if these stocks are currently being overfished. What is known is based on a series of studies conducted during the 1980’s in conjunction with the purse seine fishery and the 1990’s based on a National Marine Fisheries Service (NMFS) tag-and-recapture program and scientific collections off the west coast of Florida. Here, we present a study where our goals are to age, determine growth and condition, and assess methodology to quantify the adult population red drum population located in the offshore waters of the north-central Gulf (i.e. MS and AL). We will address MARFIN objectives 5a, estimates of the absolute abundance of red drum from the Gulf of Mexico, and 5b, age composition of adult red drum in offshore waters. Our specific objectives are to (1) determine the age distribution of adult red drum; (2) calculate and compare growth equations to historic studies; (3) assess condition through the measurement of morphometrics and the calculation of a gonadosomal index (GSI) and by determining the intraperitoneal fat (IPF) content; (4) examine relationships between age, abundance, and condition with season, environmental factors, and location through the use of multivariate statistics; and (5) evaluate the effectiveness of aerial surveys for population estimates through intensive ground-truthing using single-beam sonar, side-scan sonar, and a remotely operated vehicle (ROV). To address these objectives we will be working monthly in cooperation with two existing longline surveys, one jointly conducted between the National Marine Fisheries Service (NMFS) and the Dauphin Island Sea Lab (DISL), the other an independent survey by the Dauphin Island Sea Lab.
Estuaries as Essential Fish Habitat for Salmonids
Commercial, recreational and subsistence harvests of anadromous salmon profoundly affect the economic and cultural fabric of many North Pacific communities. Both coho and sockeye salmon support valuable fisheries in the North Pacific Region. One such community, Cordova, Alaska, has a commercial gillnet fishery with over 500 permitees. In addition, recreational anglers targeting mainly coho and chinook are the primary support for local hotels, lodges and restaurants. The economic and cultural role of salmon harvest is similar in many coastal cities along the Alaska coastline. The ability to effectively manage salmon populations is dependent on the proper identification and quantification of those parameters that effect survival and/or growth of salmon throughout their life cycle. For anadromous salmon (i.e., coho, sockeye, pink, chum, chinook and steelhead) this life cycle (Figure 1) includes rearing phases in freshwater, estuarine and marine habitats as well as return migrations through the estuarine and freshwater areas. Residency times in each of these habitats during rearing are highly variable both among and within salmon populations, particularly for freshwater and estuarine phases of life. Once in estuarine waters, juvenile salmon must physiologically adapt to oceanic conditions, assimilate information needed to return as adults, and avoid a new suite of predators. Returning adult salmon must also run a gauntlet of predators on their return migration through estuaries.
Despite the potential importance of estuarine habitats in the life cycle of coho and sockeye salmon, little is known about juvenile habitat use, residency, and survival in estuarine systems, particularly in coastal Alaska. Substantial evidence exists to support the potential importance of estuarine habitats to salmonid population and justify the need for the proposed study. For example, food availability in estuaries has been linked to survival of chum salmon, a species with an estuarine residence time of ~three weeks. For chinook, coho and sea-run cutthroat trout faster growth in estuaries has been linked to increase marine survival.
Impacts of Predators on Prey and Community Diversity
Ph.D student Glenn Miller focuses on the impacts of predator/consumer diversity on prey communities and the effects of consumer and prey diversity on the consumer community. Predators can have a strong impact on prey communities. Most available information pertains to single predator effects; however, multiple predators (predator diversity) may affect prey in non-additive and complex ways. In addition, single prey items can have different impacts on consumers than multiple or mixed prey items (prey diversity). Glenn examines these impacts by using field manipulations to alter the access of groups of predators to prey communities and observe the change in these communities through time. Laboratory experiments are also utilized to control the diversity of prey and consumers and record the changes in consumer fitness. This work is based in southeastern Alaska and the islands of coastal Alabama and Mississippi.
Red Drum - Blue Crab Interactions
One recent project in the fisheries ecology lab employed the use of acoustic tagging/tracking to study behavioral interactions of of blue crabs and red drum. This study, performed by master's student Nate Geraldi ('06), involved numerous trials of the presence and absence of predators and or structure were conducted to monitor the behavioral response of the blue crabs. This was done in two ways, first by tracking the movements of the crabs and red drum, and second by quantifying the feeding of blue crabs on six prey patches to examine the influence of predator presence on foraging behavior. The Lotek Map 6 system consists of 8 fixed hydrophones which are placed throughout the experimental sight. Acoustic tags are placed on each of the crabs and fish. Each tag has a unique ID which allows the receiver identify it. Every few seconds the tag emits a burst which is picked up by the hydrophones. A postion can be triangulated if three or more hydrophones receive the burst signal. The fisheries ecology lab plans on utilizing this system for future projects involving predator-prey interactions.
Shark Longline Survey
In May 2006 the Powers Lab in collaboration with National Marine Fisheries Service initiated a nearshore longline survey to investigate the abundance and distribution of coastal sharks in Alabama and Mississippi waters. Ten years of National Marine Fisheries Service bottom longline data indicate substantial differences in species abundance and distribution between the eastern and western Gulf of Mexico, divided roughly at Mobile Bay. These differences may carry important consequences for trophic transfer and food web dynamics between regions. As a result, the goals of this research are 1) to sample east and west of Mobile Bay to quantify any differences in distribution and abundance, 2) to use stable isotope and stomach content data to investigate potential dietary differences between regions. Additional laboratory experiments using captive reared sharks will shed light on the utility of stable isotopes in assigning trophic position for sharks. As researchers and resource managers consider multi-species management strategies, data like these are of paramount importance for adequate management of marine resources. NMFS Co-op PhD student Marcus Drymon
is heading this project.
Benthic Impacts and Foraging Ecology of Myliobatid Rays
The impacts of schooling mesopredators (smaller sharks and rays that are prey to large sharks) on benthic shellfish communities has become a strong concern for natural resource managers with the loss of top-down pressure from great sharks. Mesopredators, which occupy intermediate trophic levels, are being found as increasingly abundant in various parts of the globe as their predators are vanishing, and are often represented by the Myliobatidae (eagle rays). One such myliobatid species, the cownose ray (Rhinoptera bonasus), has already been demonstrated as integral to the destruction of some temperate shellfisheries on the east coast of the United States. However, the impacts of the schooling cownose ray have not been quantified in the northern Gulf of Mexico. Ph.D student Matthew Ajemian is examining the foraging ecology of two myliobatid species (cownose ray and spotted eagle ray - Aetobatus narinari) through gut content analyses, acoustic telemetry and field manipulation experiments where rays are excluded from natural foraging areas. From our studies on the movements and foraging behavior we aim to simultaneously advance knowledge on the feeding ecology of elasmobranch fishes (sharks, skates and rays), investigate classic foraging theories within highly tractable predator-prey systems, and provide valuable quantitative data towards proper management of benthic living resources. Utilizing two myliobatid species will allow us to better generalize foraging ecology and behavior in this group.
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Fisheries Oceanography of Coastal Alabama
Benthic Habitat Assessment Program
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As of August 2007, the Fisheries Ecology Lab has acquired instrumentation for the investigation of benthic habitats in both near and offshore locations through the use of sonar technology as part of a comprehensive benthic habitat assessment program. Specifically, a dual frequency sidescan sonar system and a single beam echosounder system were purchased for the following applications:
1) Habitat Characterization & Mapping
When used in tandem, both systems are capable of producing complete geo-referenced seafloor maps that will provide principal investigators with tools necessary to identify and estimate areal extents of varying benthic habitats that can support a variety of ecological communities (e.g. � seagrass beds, sub-tidal oyster reefs, and offshore natural and artificial reef structures). Additionally, the single beam echosounder system is able to provide investigators the ability to measure bathymetry as well as provide shoot height estimations during seagrass surveys adding a 3rd dimension to the data component.
2) Fisheries Applications
Both systems can be utilized for a variety of fisheries research tasks to include fish and zooplankton stock assessments, fish school size, density and biomass estimations, individual target measurements and habitat identification and mapping.
Additional functions outside of the applications listed above are as follows: search and recovery of lost instrumentation, sunken vessels or aircraft; identification and locations of bottom debris outside of permitted artificial reef areas; dredge operations monitoring; oyster reef restoration monitoring; oil and gas pipeline monitoring and minehunting.
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