COASTAL HABITATS CURRENT RESEARCH<<
 
Artificial Reef Research through the Years
Compilation of 11 major research projects (printer-friendly 54K pdf)
 
Research Bibliography
A list of publications which have resulted from the above research projects (printer-friendly 22K pdf)
 
User Benefits and Economic Impact of Artificial Reefs in Southeast Florida
 
Improved Stone Crab Production Through Habitat Enhancement
 
The Effects of Man Made Structures on Nearby Resident Fish Communities
 
Bioaccumulation of Toxic Metals by Organisms Colonizing Artificial Reefs Constructed from Fossil Fuel Wastes
 
The Relative Importance of Recruitment, Attraction and Production of Reef Fishes on Natural and Modular Artificial Reefs
 
Variation of Reef Dispersion to Manage Targeted Fishery Assemblages
 
Limits to Recruitment of Spiny Lobster in Florida: Assessment of Artificial Enhancement Techniques
 
Nutrient Cycling and the Optimum Productivity of Shallow-Water Artificial Reefs And Influence of Artificial Reef Shelter Characteristics on Fish Community Structure and Production
 
Optimizing Artificial Reef Design: Feeding Habits and Forage Area Interactions of Fish Assemblages
 
The Future of Florida Spiny Lobster: Developing a Predictive Model and Putting Artificial Shelters to the Acid Test
 
Hydrodynamics Processes at Artificial Reefs and Effects on Plankton and Baitfish Abundance
 
 
COASTAL HABITATS CURRENT RESEARCH<<
 
User Benefits and Economic Impact of Artificial Reefs in Southeast Florida
Lead Researcher: Walter Milon
Project Number and Duration: R/LR-E-9-PD, 1984 - 1988

Question: Artificial reefs are popular among anglers and divers in Florida, which has more public artificial reefs than any other state. How popular are the artificial reefs in Florida's largest county, Dade County and what is their value to fishermen and divers - and their economic benefit to the community as a whole?

Project: Researchers mailed a survey to 3,600 registered boat owners in Dade County and received about 1,600 responses. The surveys sought detailed information about how often the boaters visited artificial reefs and their activities there, as well as biographical information on the boaters and specifications about their boats. The researchers then
analyzed the data using a variety of statistical methods.

Results: Slightly under a third of the fishermen who responded to the survey said they fished on artificial reefs during the six-month period , while about 13 percent of the divers who responded said they made diving excursions on artificial reefs. Both divers and fishermen indicated they would be willing to pay for new artificial reefs - as did boaters who did not even visit the reefs (though non users would pay less than users.) The researchers estimated the economic benefit of Dade County's artificial reefs system at between $17.5 and $128.3 million, though these figures do not include the value of the reefs to operators of charter fishing and diving boats.

Impact: The study resulted in a Florida Sea Grant publication,"The Economic Benefits of Artificial Reefs: An Analysis of the Dade County, Florida Reef System." One of only a handful of papers to document the economic benefits of artificial reefs in Florida and nationally, the paper is a valuable resource for public policy makers or private groups involved in artificial reef research or projects.

Publications: Articles about this research appeared in journals including Policy Studies Review, Marine Resource Economics and the Southern Journal of Agricultural Economics.

Related Research: In a 1998 study, Florida State University researchers found that visitors to the artificial reefs off a five-county area in the Florida Panhandle spent $358 million over a 12-month period. The expenditures generated 7,468 full- and part-time jobs and over $76 million in wages and salaries in Escambia, Santa Rosa, Walton, Bay and Okaloosa counties, according to the study, The Economic Value and Importance of Artificial Reefs in Northwest Florida. "The study confirmed that the Florida artificial reef system is very important in drawing people to our waters," said Mark Bonn, a co-author and FSU professor of tourism.
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Improved Stone Crab Production Through Habitat Enhancement
Lead Researcher: Bill Lindberg

Project Number and Duration: R/LR-B-14, 1984 - 1988

Question: Relished for their delicate white meat, stone crabs, Menippe mercenaria, are among Florida's most valuable seafood products, but overfishing and habitat loss pose serious threats to the crab population. Could artificial reefs help ensure the population remains robust?

Project: Researchers built several artificial reefs out of a range of different materials -- including culverts, pilings and blocks -- then arranged them in different configurations on the ocean bottom Florida's Gulf coast near Cedar Key. They kept track of the sizes and genders of the crabs that colonized the reefs through diving expeditions. By marking crabs on one visit and then sampling the population at a later visit, they also kept track of how long individual crabs remain at the artificial reefs. A statewide crash in stone crab populations in 1984-85 and a hurricane in 1985 posed major hurdles, but the researchers still managed to gather useful data.

Results: Perhaps most significantly, the project found that widely spaced reefs attracted more stone crabs, higher numbers of females, and larger crabs than closely spaced reefs. They also found that it made little difference what material was used in the construction of the reef, but that the shape of the structure was important to the crabs (they preferred horizontal holes). The researchers further found that the crabs remained at the artificial reefs for short periods of time.

Impact: The project revealed much about stone crab behavior and contributed to broader understanding of the ecological function of reefs. Provided the technical impetus for larger, more comprehensive projects related to fisheries and structure that continue into the present day.

Related Research: The crab project has evolved into what researchers describe as the largest experimental artificial reefs system in the nation. Built over several years, the Suwannee Regional Reef System spans 24 nautical miles north and south of the mouth of the Suwannee River. Among other topics, researchers have studied how the reef affects gag grouper populations and how the reefs affect the flow of waterborne nutrients. To date, nearly $2 million, principally from state government sources, has been invested in construction of the reef system and research there.

Quote: "The entire reef research program at UF began with this first modest project." - Bill Lindberg
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The Effects of Man Made Structures on Nearby Resident Fish Communities
Researchers: William Alevizon, J.C. Gorham and several graduate research assistants.

Project Number and Duration: R/LR-B-20, 1985 - 1987

Question: The classic debate over artificial reefs is whether the reefs increase fish numbers or merely concentrate fish in one place. Could a carefully controlled study of the impacts of artificial reefs on the fish communities in a Florida marine sanctuary help move this debate in one direction or the other?

Project: Researchers counted and identified the fishes living in a flat, sandy habitat in two six-hectare (14.8 acres) study sites in Looe Key National Marine Sanctuary in the Florida Keys. Next, they built two artificial reef groups, each consisting of 12 small PVC- and concrete blocks, near the sites. They then censused the fishes in the study sites every three months for one year.

Results: Of the five most abundant species - green razorfish, Hemipteronotus splendens, pearly razorfish, H. novacula, rosy rasorfish, H. Martinicensis, slippery dick, Halichoeres bivittatu and the sand seabass, Diplectrum formosum -- researchers saw no change in the total numbers of adult and juvenile fish on the sandy habitat, or in the proportion of one species to another, in the pre- and post-reef censuses. The researchers next took the project a step further, building a large artificial reef at the center of one reef group. Nine months later, numbers of all but one of the most common species had increased 100 percent - yet numbers remained unchanged on the natural reef group. Both the earlier and later results appear to demonstrate that, at least in this case, artificial reefs resulted in an increase in fish stocks rather than a concentration of existing stocks.

Impact: By demonstrating one scenario in which artificial reefs did not have a negative impact on surrounding fish populations, the results provided support to public and private efforts in Florida to develop new artificial reefs and enhance existing ones. Through studies such as this one, artificial reefs are coming to be seen as more than just convenient 'fish attractors' In a report on the project, Alevizon wrote, "...The rational use of manmade reefs may substantially extend our ability to protect natural endangered systems, by providing the option of increasing available suitable habitat."

Publications: At least two articles about this research appeared in the Bulletin of Marine Science.

Related Research: The researchers also used the reefs to test the hypothesis that increasing the nooks, crannies and other structural pieces of the reef would increase the stocks of young fish on the reefs. Results were positive.
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Bioaccumulation of Toxic Metals by Organisms Colonizing Artificial Reefs Constructed from Fossil Fuel Wastes
Researchers: John Trefry, Iver Duedall and Simone Metz.

Project Number and Duration: R/LR-B-21, 1987 - 1989

Question: During the 1980s, some interests in Florida sought to divert solid waste from on-site storage due to concerns over the leaching of harmful chemicals and metals into groundwater. One such waste was oil ash waste, a byproduct of burning petroleum to generate electricity. Could the waste instead be transformed into safe and beneficial artificial reefs?

Project: To stabilize the oil ash and minimize leaching, researchers combined it with fly ash, lime and cement, then shaped it into blocks and smaller bricks. They used the material to build two small artificial reefs on the ocean floor about two kilometers (1.2 miles) from Vero Beach. They also built two identical reefs out of concrete blocks and created two control areas with no reefs. The researchers then tested the marine organisms that colonized the reef, fishes that eat the organisms, and the surrounding sea water to determine the extent of the release of the trace metals into the environment.

Results: Researchers found that concentrations of some trace metals in "biofouling" organisms such as jingle shells collected from the oil ash blocks were close to those collected from the cement blocks, while others differed - with nickel and vanadium levels were as much as six times higher in organisms from the oil ash blocks. The higher levels, however, did not appear to damage the organisms. The researchers also found that, in general, levels of several trace metals in water collected near the oil ash blocks and cement blocks were similarly low. Lastly, concentrations of copper, zinc, vanadium and nickel in liver and flesh samples from Sheepshead, Archosargus probatocephalus, and Gray Triggerfish, Balistes capriscus, collected from near the oil ash and concrete reefs were similar to samples from fish collected near the nartural control areas.

Impact: Researchers concluded that stabilized oil ash reefs could provide a practical and beneficial use of waste material. Researchers worked closely with Florida Power & Light, facilitating the rapid transfer of the idea to the private sector.

Publications: An article about this research appeared in The Marine Pollution Bulletin and was presented at three international symposiums.

Related Research: During the period of this study, comparable work was being carried out at the State University of New York at Stony Brook and at the Institute of Marine Environmental Protection in Dalian, China. Researchers associated with the Florida Sea Grant study also were involved in these other studies. Researchers continue to do research on stabilization of phosphogympsum waste in Louisiana.

Quote: "The oil ash and control reefs were constructed with the aid of divers in just one day, and monitoring of the reefs was carried out for one year. Leaching of trace metals from the blocks was extremely slow, and only limited instances of enhanced bioaccumulation of metals were observed. However, pressure from environmental groups led the electric power industry and the State of Florida to discontinue construction of artificial reefs from stabilized waste material." - John Trefry
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The Relative Importance of Recruitment, Attraction and Production of Reef Fishes on Natural and Modular Artificial Reefs
Researchers: Lead researcher: Michael McGowan. Others: Patrick J. Walsh, James A. Bohnsack and William J. Richards.

Project Number and Duration: R/LR B-22, 1987 - 1989

Question: This project sought to address several questions surrounding artificial reefs. These included 1) Does the size of the reef make a difference in how many fish settle on the reef versus how many visit and then move on? 2) How do the fish assemblages on similar-sized and natural reefs differ? 3) How many and how diverse are the fish larvae that occur near the reef, and how many larvae settle on the reef?

Project: Researchers built 50 identical concrete artificial reef blocks -- essentially, large (2950-kg. or 5700 lb.) square blocks with two holes in each wall -- and sunk them in varying small- to large groups about 6.4 kilometers (four miles) east of Key Biscayne in Dade County. They also monitored a much larger, natural live-bottom reef nearby. The researchers' methods varied depending on their goals:

1) To probe the impact of reef size on visiting and resident fishes, divers counted, identified and measured fishes using standard visual methods, including counting large fish as they approached the reef and using small mirrors to peek into the reefs' openings and count smaller fish. They classified resident fishes as fishes seen on more than one census or fishes known to be reef residents and visiting fishes all fishes spotted only during one census (or that appeared to be using the reef only for temporary shelter or feeding.) Fish classified as transients were fish that moved away during sampling and appeared not to react to the reef.

2) To determine the role of the artificial reef in attracting larvae, the researchers towed a specially made 1-meter net behind a boat. Fastened to a "sled" made of PVC pipe, the drag of the net caused it to rise slowly to the surface, so that the water column was sampled as uniformly as possible. The researchers made multiple tows, then identified captured larvae in the laboratory.

Results: Researchers found that the largest proportion of fishes (65 percent) that appeared on the reef were residents, while 20 percent were visitors and 16 percent were transient. Generally speaking, the larger the reef, the more fish arrived to colonize it. These included several species valued commercially or recreationally, including yellowtail snapper, Ocyurus chrysurus, and snowy grouper, Epinephelus niveatus, although these fish tended to disappear from the reef after a period of time. Other commercially important species also colonized the reef, including hogfish, Lachnolaimus maximus, lane snapper, Lutjanus synagris, and mutton snapper, Lutjanus analis. Overall, the researchers found that the number and weight of fish on artificial reefs was far higher than on similar-sized natural reefs.

In 16 one-day cruises and a total of 96 samples, researchers also collected 41,821 fish larvae from the area within the artificial reef. Perhaps most interestingly, they found that the amount of larvae varied in direct proportion to the amount of zooplankton in the water during the previous month - in other words, spawning and survival of fish larvae directly followed the availability of plankton for forage. The larvae of herrings, the family Clupeidae, jacks, the family Carangidae, clingfishes, the family Gobiesocidae, and gobies, the family Gobiidae, tended to dominate, while larvae of coral reef species, were few and far between.

Impact: This study provided quantitative data on the impacts of artificial reefs that will prove useful for reef planners and managers.

Publications: Articles about this research appeared in The Bulletin of Marine Science and a book, Habitat Structure: The Physical Arrangement of Objects in Space.
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Variation of Reef Dispersion to Manage Targeted Fishery Assemblages
Researchers: Bill Lindberg, Thomas Frazer and William Seaman.

Project Number and Duration: R/LR-B-23, 1989 - 1990

Question: A study of how artificial reefs affected the population of stone crabs, Menippe mercenaria, found that widely spaced reefs attracted more stone crabs, and larger crabs, than more closely spaced reefs. How would reef spacing impact reef-dwelling or reef-visiting fish species such as grunts, Haemulidae, or jacks, Carangidae?

Project: Researchers arranged concrete culvert pipes in two contrasting patterns at depths of 12 meters (39.3 feet) in the eastern Gulf of Mexico. In one pattern, the pipes, typically two meters long and one meter in diameter, were arranged in concentrated "clumps," while in the other pattern they were more dispersed. The researchers then counted and identified the fish on a monthly basis for an 11-month period between Nov. 1989 and Oct. 1990, though poor visibility prevented counts in August and September.

Results: Researchers observed approximately the same number of fish species on both types of reefs (38 on the clumped reefs and 40 on the dispersed reefs), though the monthly median number was always higher for the clumped reefs. Absolute number of fishes was higher on the clumped reefs, with eight species in five families (Haemulidae, Carangidae, Serranidae, Ephippidae and Sparidae) comprising 96 percent of all counted fish. These included many visiting pelagic species, which comprised 83 percent of all counted fish and were observed in greater numbers on the clumped reefs. Of all the counted fishes, only one species typically targeted by fishermen, the black sea bass, Centropristis striata, was seen in sufficient numbers to be statistically evaluated. In its case, there were no significant differences in black sea bass numbers on the clumped or dispersed reefs.

Impact: The results provide information that may be useful to artificial reef builders in planning and designing reefs. Those interested in creating reefs for recreational diving, for example, might consider clumped reefs because of their demonstrated higher monthly diversity of fishes. Fishery managers might also consider clumped reefs as a method to enhance overfall fish abundance.

Publications: Articles about this research appeared in the Proceedings of the International Conference on Ecological System Enhancement Technology for Aquatic Environment and the U.S. Symposium on Artifical Habitats for Fisheries.

Related research: Coupled with the project on stone crabs (R/LR-B-14), this project spurred the development of the Suwannee Regional Reef System in the northeastern Gulf of Mexico. This large-scale experimental reef system has been used in a series of state- and federally funded research projects since 1990 to more rigorously test the impacts of habitat patchiness on patterns of reef fish abundance and production, and to identify the underlying ecological processes.

Quote: "We often hear that science progresses by learning from failed experiments, and this project was a good example. It produced inconsistencies in the results, and incongruities with theoretical expectations, that caused us to re-examine the questions being asked and how we were attempting to answer them. The outcome was a much more rigorous and definitive research program that has yielded results now being applied directly by fisheries managers." - Bill Lindberg
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Limits to Recruitment of Spiny Lobster in Florida: Assessment of Artificial Enhancement Techniques
Researchers: Lead researchers: William Herrnkind and Mark Butler. Collaborators included John H. Hunt and several graduate research assistants.

Project Number and Duration: R/LR-B-30, 1993-1995

Question: How many young spiny lobsters, Panulirus argus, (with carapaces up to 50 mm) remained in Florida Bay following the cyanobacterial blooms and sponge die-offs of the early 1990s, and how many sponges and other sheltering structures did the bay contain? With answers, could researchers develop a computer model that would predict the outcomes of future sponge die-offs on the spiny lobster population?

Project: Faculty and graduate research assistants did nearly 1000 30-minute visual searches of crevices, ledges, sponges and other potential lobster habitats and captured all observed young lobsters for measurement. By noting the terrain where lobsters were found (for example, hard bottom versus sand) they were able to compare the spiny lobster productivity for different terrains. Along randomly chosen transects, researchers also recorded the horizontal dimensions and categories of all structures big enough to serve as lobster shelter. The results of the lobster searches and habitat surveys were extrapolated to provide estimates for a roughly 505-square-mile nautical area between Grassy Key and Key West.

Results: The estimated population of young lobsters was pegged at 67 percent of the original population in the area affected by the cyanobacterial blooms and sponge die off. About 32 percent of the region was composed of hard bottom of the type that harbor young lobster, including sponges and coral heads. The data enabled the researchers to design a computer model, known as an Individual Based Model, that operates by assessing, one by one, the fates of millions of "cyber juvenile lobsters" under the reduced-shelter conditions produced by sponge die offs. The model that showed that: 1) loss of sponges resulted in increased mortality of young lobster at the time the lobsters left their algal habitat to occupy crevices : 2) mortality would be highest where there was no alternative structure and 3) estimated mortality of exposed lobsters ranged from 1 percent to as high as 30 percent.

Impacts: The lobster census and bottom survey provided essential background data for future assessments of the condition of the spiny lobster nursery in Florida Bay. The computer model was the first ever developed for spiny lobster, a step toward a more comprehensive model that could one day help fisheries managers accurately predict future population levels. The model could also be expanded for use in other fisheries.

Publications: Articles about the research appeared in journals including the Canadian Journal of Fisheries and Aquatic Science, Crustaceana, The Bulletin of Marine Science and publications of the American Fishery Society.

Related research: The project was the impetus for a later Florida Sea Grant (R/LR-B-38) project that tested the hypothesis that shelter for the predator-vulnerable early juveniles matters a lot in determining recruitment to eventual fishery stock.

Quote: "In the later project, we experimentally tested whether sponge-sized concrete shelters placed in spongeless areas could bring the early juvenile survival recruitment back to natural, pre-sponge-die-off levels. The answer is yes." - William Herrnkind
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Nutrient Cycling and the Optimum Productivity of Shallow-Water Artificial Reefs And Influence of Artificial Reef Shelter Characteristics on Fish Community Structure and Production
Researchers: Alina M. Szmant, Anne-Marie Ecklund, James Bohnsack and several undergraduate and high school students.

Project Numbers and Duration: R/LR-B-34 and R/LR-B-36, 1990 - 1993 and 1993-1995

Question: The first of these related projects sought to determine whether artificial reefs with lots of internal structure trapped water-borne nutrients and boosted primary production, as well as fish numbers and diversity. When results proved inconclusive, researchers launched a second project aimed at determining how the internal complexity and structure of reefs impacted the densities, biomass and predator-prey relationships in fish.

Project: In the first project, researchers sank four sets of pyramid-shaped artificial reefs in 10 meters (32.8 feet) of water off Palm Beach County, leaving one set hollow and filling the other three with concrete rubble. They painted one of the filled reefs with anti-fouling paint to prevent all primary production. Believing that the 15 months allotted for the experiment might not be enough for natural nutrient enrichment to occur, they added fertilizer to the second filled reef. In the second project, researchers added "predator exclusion cages" to gauge how the absence of predators would impact fish populations and performed additional fish censuses at the reefs.

Results: Researchers found no difference in the amount of algae or other primary production that appeared on the fertilized and unfertilized filled reefs (though, as expected, the reef painted with anti-fouling paint remained clean). However, the researchers did find that the anti-fouled reef had a lower number of fish species, leading them to suggest that primary production at artificial reefs has a positive impact on the number of fish there. They also found that small colonial invertebrates such as hydroids added structure and habitat for small newly recruited fish. In what researchers ranked as their most important finding, they found that the filled reefs had more fishes, and a higher diversity of species, than the reefs lacking any structure. In the second project, which explored this result, the researchers found that filled reefs had significantly more Tomtate grunts, Haemulon aurolineatum, gray triggerfish, Balistes capriscus, surgeonfishes, Acanthurus spp. and juvenile drums, Equetus spp. Researchers also found that reefs protected by predator cages had many more juvenile fishes, suggesting that shelter is an important characteristic for growing fishes.

Impact: The results show that artificial reefs should be built with a large number of smaller sized and shaped crevices and holes, especially in shallow waters. The Dade County artificial reef program took this into consideration when it designed the Sunny Isles restoration project. The study also contributed to a greater understanding of coral reef fish ecology, which could lead to more accurate and efficient fisheries management.

Related Research: None.

Publications: This research was the subject of at least one dissertation and was presented at an artificial reef conference in Florida.

Quote: "The most diverse and productive communities in the oceans are coral reefs, and they are so diverse because of the variety of coral growth forms. If we want to create man-made reefs that really result in new production, we should learn from nature's own handiwork, and build into our reefs the diversity of architectural complexity that attracts such a great diversity of life forms." - Alina Szmant
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Optimizing Artificial Reef Design: Feeding Habits and Forage Area Interactions of Fish Assemblages
Lead Researcher: Stephen Bortone

Project number and duration: R/LR-B-35, 1993-1995

Question: With artificial reefs seen as one solution to decline in fish stocks, scientists would like to know the most effective reef configuration - the size and shape of the artificial reef - for boosting fish numbers. This project sought to begin addressing this question by asking a more fundamental question: What do fish eat at artificial reefs and where exactly do they feed?

Project: Researchers collected specimens representing 25 of the most common reef-dwelling species from bridge rubble artificial reefs between 2 and 5 kilometers offshore in the northern Gulf of Mexico near Panama City. Depending on size, divers speared or netted the fish, which were then preserved using Formalin solution. The researchers then removed the fishes' stomachs and analyzed their contents.

Results: Scientists identified 44 taxa of prey altogether, including two algal divisions and eight animal phyla, including polychaetes (segmented worms in the phylum Annelida), three classes of mollusks, two classes of arthropods, echinoderms and chordates. Seventeen of the 25 fish species had clear dominant prey items. The breakdown included 1) The fish eaters: cardinal fish, Apogon pseudomaculatus, the tomtate grunt, hameulon aurolineatium, the gag grouper, Mycteroperca microlepsis, the gray snapper, Lutjanus griseus, flounder, Paralicthys albiguta and greater amberjack, Seriola dumerili 2) The Xnathid crab eaters: black sea bass, Centropristis ocyurus, cubbyu, Equetus umbrosus, the gulf goadfish, Opasanus beta, Rypticus maculates and the belted sandfish, Serranus subligarius. And 3) Polychaetes eaters: the pigfish, Orthoprists chrysoptera, and the cocoa damselfish, Pomacentrus variabilis. The scientists couldn't determine the preference of seven of the remaining fish species because their stomach contents were unidentifiable. Overall, the study determined that the most important prey items were fishes followed by xanthid crabs, while algae was not an important prey taxa. The study also determined the feeding fish could be organized into seven distinct guilds: lower structure pickers, ambush predators, lower structure crustacean predators, upper structure pickers, upper structure predators, water column pickers and reef associated open water feeders.

Impact: Understanding of what fish feed on, and where they feed, should provide clues to scientists and managers on what artificial reef configurations may impact different fish species.

Publications: Articles about this research appeared in journals including Gulf of Mexico Science.
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The Future of Florida Spiny Lobster: Developing a Predictive Model and Putting Artificial Shelters to the Acid Test
Researchers: William F. Herrnkind and Mark Butler.

Project number and duration: R/LR-B-38, 1995-1997

Question: This project sought to determine two things: 1) Is it possible to create a computer model that could predict the number of juvenile spiny lobsters entering the Florida fishery based on environmental changes to the lobster habitat? 2) How effective are artificial reef structures as substitutes for sponges, the natural shelter for young juveniles?

Project: For the first goal, researchers developed a computer model with a flexible user interface that allowed users to input a wide range of data, including the effect of harmful algal blooms on sponges and the impact of artificial shelters. For the second, they placed concrete "shelter" blocks on a series of small (500 square meter) and large (10,000 square meter) sponge-free sites in Florida Bay. They did quarterly censuses of the sites along with similar sites that contained no sponges and sites with many sponges. Because sponges typically provide habitat for juvenile lobsters, they counted all lobsters with carapaces less than 50 millimeters in size.

Results: For goal one: The researchers ran model simulations to predict the impact of harmful algal blooms and resulting sponge die-off on the abundance of juvenile spiny lobsters, their use of shelters, and their emigration rate. The model predicted that during years of harmful algal blooms, overall lobster abundance would actually increase 15 percent, in part because the die-off accompanied an unusually high supply of postlarvae from offshore and in part because less-preferred shelters were available. The predictions, the researchers said, were "strikingly similar" to what researchers and fishermen observed in the field - lobster populations increased as compared to the years before the die-off. For goal two: The experimental concrete shelters rapidly recruited both new settlers and older juvenile immigrants, with abundances typically exceeding sponge-free sites and comparing well to the sites with good sponge cover.

Impact: Although it needs further testing, researchers said the model has promise as an effective tool for predicting future fishery stock. The research also seems to indicate artificial shelters could be used for mitigation and enhancement efforts.

Related research: This project resulted from an earlier Florida Sea Grant project, (R/LR-B-30) that showed that a computer model could be used to predict lobster-sponge interactions.

Publications: Two especially important papers resulted from this research, one in Marine and Freshwater Research and one in The Journal of the American Fisheries Society. The first showed that special artificial shelters can sustain juvenile survival and recruitment after the loss of natural sponge shelters. The second demonstrated that artificial shelters can replace natural sponges on a large scale.

Quote: "Irrespective of whether or where artificial shelters are deployed for shelter rehabilitation, we believe their importance has been ecologically demonstrated on a relevant scale."
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Hydrodynamics Processes at Artificial Reefs and Effects on Plankton and Baitfish Abundance
Researchers: Peter Sheng and Ed Phlips

Project Number and Duration: R/LR-B-43, 1997 - 1998

Question: Do artificial patch reefs have different hydrodynamic conditions -- such as different degrees of turbulence or upwelling or masses of suspended sediments - depending on their size? And do changes in nutrient and plankton concentrations correspond with changes in the stocks of baitfish near reef sites?

Project: Researchers installed instruments designed to measure the current, turbidity, phosphorous, nitrogen, clorophyll a and other variables in the water at an artificial reef in the Suwannee Regional Reef System in Florida's gulf coast. They placed the instruments at two locations around the reef and recorded measurements during four separate sampling days. Unfortunately, due to instrument failure, measurements were only recorded for one reef, so reef-to-reef comparison was not possible.

Results: Researchers found no correlation between the total suspended solids in the water and tidal currents or wind and waves, nor did they find evidence of elevated levels of phytoplankton or particulate organic carbon around the reef. However, there was evidence that particulate organic carbon concentrations near the bottom correlated with current velocities. That observation supports the idea that sediment resuspension is dependent on current velocity.

Impacts: The project shed light on how to design and place instruments for future similar experiments. With time, such experiments could yield data that will help fishery managers better design artificial reefs to enhance fish stocks and the reef fisheries.
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