Final Report on Five-Year Spiegel Grove Assessment

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Note the encrusting organisms after just 5 years and the Purple Reeffish, Photo by Mike Ryan
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Invertebrate community recruitment to the Spiegel structure, Photo by Mike Ryan
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Blackfin Snapper school on Spiegel Grove, Photo by Mike Ryan
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Large Arrow Crab, Photo by Mike Ryan
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Midnight Parrotfish and Bluehead Wrasses, Photo by Mike Ryan
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Cubera Snapper on Spiegel, Photo by Alison Johnson

This past summer, REEF completed its 5-year monitoring and assessment of the ex-Navy Landing Ship Dock, U.S.S. Spiegel Grove, intentionally deployed in 130' deep water as an artificial reef off Key Largo in June of 2002. At the time of its sinking, the Spiegel, at 510' in length, was the largest vessel intentionally sunk as an artificial reef. More recently, REEF completed its final report on the data collected, largely through members' efforts in the water these last few years, so a multus gratia (big thank you) from all of us at REEF to those of you who participated on the Advanced Assessment Team monitoring of the Spiegel. This was every bit your project as much as ours. I am asked quite often in the field how REEF surveyor efforts contribute to science, conservation, and education so I want to share with you some of our findings as the Spiegel assessment serves as a great example of the power of concerned and active citizen scientists to effect positive changes in our communities. For a full viewing of our final report, please visit our website at 5 Year Spiegel Grove Monitoring .

Before I highlight a few of our findings, let's go over what our methods were for conducting our Spiegel assessment. Surveys were conducted using the Roving Diver Technique (RDT), a non-point visual survey method that serves as the mainstay for most REEF efforts in the water. The purpose of this method is to gather a comprehensive species list with sighting frequency and relative abundance estimates, for fish species only in the case of this study. Staff and REEF volunteers all had to be members of the Advanced Assessment Team (AAT) for REEF (learn more about how to become an AAT member http://www.reef.org/programs/volunteersurvey/aat). Each monitoring event consisted of 4 days of two-tank monitoring dives at the Spiegel Grove and 7 surrounding reference sites.

The overall objective of the study was to assess any changes in fish community structure over time with the addition of the newly deployed artificial reef, changes not just to the Spiegel site, but changes to the surrounding natural reef sites as well. A central biological question as to the merits of vessel type artificial reef deployments is whether or not they add fish species in terms of both numbers of fish (biomass) and numbers of fish species (biodiversity) to the artificial reef and the surrounding natural reef sites. In other words, in the Field of Dreams metaphor, if you build it will they come and where will they come from? Ultimately, resource managers and other stakeholders hope that the addition of the artificial reef adds fish not only to the targeted site, but seeds surrounding reefs with the reproductive output from the resident fish population. The scale of these questions cannot be adequately addressed in a 5-year pilot study such as the one REEF just completed and that was not our charge but it is important to understand the concept behind sinking ships as artificial reefs. And we should commend Monroe County, the Upper Keys Artificial Reef Foundation (UKARF), and the Florida Keys National Marine Sanctuary (FKNMS) for funding this initial pilot study. A second socioeconomic question not addressed in REEF's work asks the important question of how much SCUBA diving pressure is decreased on natural reefs by the addition of a top recreational dive site such as the Spiegel and how much additional tourist revenue is gained? Finding answers to both the biological and economic questions above are critical in providing guidance for future marine resource management decisions on whether or not to deploy artificial reefs of this type and when and where the sinking of these large retired vessels is appropriate.

Okay, some quick highlights but again for the full report, please visit our website. Over the 5-year study, REEF conducted 76 RDT surveys on the Spiegel itself and another 445 survey dives on the surrounding 7 reference sites. 191 fish species were documented on the Spiegel Grove for all surveys combined. 46 species of fish were observed on the Spiegel just one month after deployment with the average number of species climbing to 76 per monitoring event thereafter. Approximately 3 years after deployment (Aug 2005), persistence in species composition at the Spiegel Grove site through time had increased to levels closer to those of the surrounding reefs. Striped grunts and Tomtates were immediate arrivals on the newly deployed site. Currently, 5 years post deployment, fish species composition on the Spiegel site is more akin to what you would expect on a deeper reef site including schools of Blackfin Snapper, Creole Wrasses, Bluehead Wrasses, Purple Reeffish, Sunshinefish, Bluerunners, Yellowtail Reeffish, Greenblotch Parrotfish, Tomtates, Spotfin Hogfish, Yellowmouth Grouper, Black Grouper, and the Federally protected Golilath Grouper (for a complete list of species sighted and statistical comparisons between study sites take a peak at the report). Blackcap and Fairy Basslets rarely occur in the Keys but interestingly, on several occasions, both have been surveyed on the Spiegel, most notably after hurricane storm surges from offshore. Of course, the Spiegel originally sunk on its starboard side was righted during Hurricane Dennis in July of 2005, confounding results of our survey shortly thereafter. And large, deeply sunk vessels such as this one certainly offer numerous hiding places to groupers in particular, making full visual assessments difficult. We have included in our report suggestions for future studies as well.

REEF would like to thank Mike Ryan of Horizon Divers for supplying important anectodal information about the Spiegel. He was one of the first divers on the newly deployed vessel and has logged more than 240 dives on site since then, meticulously recording fish and invertebrate sightings in the true naturalist vein. Also, REEF thanks Quiesscence Divers and Horizon Divers and Scott Fowler for providing boat and logistical support for all of our diving efforts over the past 5 years. This spring (2008), the Hoyt Vandenberg is scheduled for deployment a few miles off the coast of Key West. REEF will be leading the monitoring efforts over a similar 5-year time period and we'll keep you posted on our efforts. Two suggested readings are referenced in our report, one by Arena et al (2007) and the other by Leeworthy et al (2006) assessing biological and economic impacts of artificial reefs, respectively.

Happy Holidays everyone and if you are visiting Key Largo next year, visit the wreck and see for yourself how things are coming along.

 

Design by Joanne Kidd, development by Ben Weintraub