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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.
Snapper Foraging on Artificial Reefs
One economically important species that is subject to top-down control on reefs and has recently been classified as overfished and is undergoing overfishing is the vermillion snapper (Rhomboplites aurorubens). Landings of vermillion snapper were approximately 2.5 million pounds in 2002, but catch per unit effort (CPUE) has declined by 50 % since 1993. Unlike red snapper, vermillion snapper can be found as small juveniles on reefs and hard bottoms, as such, they may be an important prey item for other piscivores that reside around the reef matrix. Observations made during recent cruises conducted by the University of South Alabama’s red snapper tagging project have documented the regurgitation of juvenile vermillion snapper by red snapper on local charter boats. Although a recent survey of the diet of red snapper failed to identify any vermillion snapper in the gut contents, they had approximately 30% of the gut contents that were unidentifiable fish matter and about 50% of the fish they sampled had no prey items in their gut at all, leaving the possibility that predation by red snapper was occurring undetected. If large scale predation of vermillion snapper is occurring by reef piscivores, a more complete understanding of what role this species plays in the reef food webs may be critical to understanding the impacts of current stock rebuilding plans. According to the Gulf of Mexico Fisheries Council, the “indirect biological effects (of rebuilding vermillion snapper stocks) are difficult to assess and the effects of rebuilding the vermilion snapper fishery may be unrecognizable compared to those associated with rebuilding other GOM reef fishes”. It is critical that as marine fisheries management moves towards a better understanding of ecosystems to rebuild stocks, we expand our understanding of inter-species interactions.
The overall goal of our project is to examine multi-species interactions in reef fish assemblages in the Northern Gulf of Mexico and to assess how fishing and provision of structural refuge influences these interactions. Specifically, our objectives are to (1) assess the impact of red snapper on recruitment and mortality of vermillion snapper on offshore reefs; (2) evaluate how removal of red snapper, as well as other large piscivorous fish, modifies the reef fish community; and (3) examine how reef architecture affects these interactions. Objective 3 is of particular importance because the outcome of predator-prey encounters and competitive interactions can be altered by the availability of complex, structured habitat. For example, the provision of refuge for recruiting fishes can be the chief determinant of post-settlement and early juvenile survival for many marine species. We hypothesize that (1) within a typical reef fish community, there will be a negative relationship between red snapper density and post-recruitment survival of vermillion snapper (2) removal of large piscivores will result in an increase in the recruitment of reef specific fishes as well as an increase in overall reef diversity, and (3) there will be a positive relationship between reef habitat complexity and recruitment/survival of reef fishes caused by an increase in refuge space.
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 of Elasmobranch Mesopredators
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 typically 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 shellfish industries on the east coast of the United States. However, the impacts of the schooling migratory cownose and other mesopredator fishes) have not been quantified in the northern Gulf of Mexico. Ph.D student Matthew Ajemian is examining the foraging ecology of various mesopredators through gut content analyses and acoustic tracking. This past May (2007) the lab began a pilot project studying the movements of the spotted eagle ray (Aetobatus narinari) in Bermuda. Populations of these rays may be increasing and have raised concerns for Bermudian resource managers and conservationists as they are suspected predators of economically valuable conch (Strombus spp) and bivalves (e.g. Codakia). We aim to evaluate the role of A. narinari in Bermudian waters through studies of food consumption, movements, and predator-prey interactions. From our studies on the movements and foraging behavior of various mesopredators we aim to simultaneously advance knowledge on the feeding ecology of elasmobranch fishes (sharks, skates and rays), test classic foraging theories, and provide valuable quantitative data towards proper management of benthic living resources.
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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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