UPDATE (October 2010) — The results of the count are in! A total of 312 goliath grouper were counted, an average of 5.3 fish per site. The information tended to agree with other work that has shown that more goliath grouper are found on high relief structure such as shipwrecks and concrete pilings and culvert.
Most of the fish were in the 3-5 ft size range, which probably represents 5-11 year old goliath grouper. There was about an equal number of fish less than 3 ft and more than 5 ft.
What is next? Based on the success of this year’s count, we are tentatively making plans to do this again next year. We want to expand the number of sites that are surveyed. Also, the information will become more valuable when scientists are able to compare the data over a number of years. I want to be perfectly clear –this information will not be complete enough to tell us exactly what the status of the goliath grouper population is. It will be a small part of the puzzle, but it looks like it could help scientists develop better information.
Goliath grouper and the 2010 cold spell: Although not related to the goliath grouper count, we did want to provide readers with an update on the impact of this year’s cold weather on this fish. It is not good news. Hundreds to thousands of juveniles were reported to be killed by the cold temperatures in the nursery habitat of Everglades National Park. It is very difficult to say whether this will have an impact on overall abundance. Perhaps the large breeders were able to safely move to deeper water and the impact will be small or perhaps it will significantly impact the abundance of certain year classes. Only time will tell.
Begin Original Article (July, 2010)
In early June an ambitious group of scientists, citizen volunteers, charter boat captains, and county government staff undertook a survey of goliath grouper abundance on over 50 artificial structures along Florida’s southwest coast (Pinellas south through Collier counties).
The Great Goliath Grouper Count is a Florida Sea Grant Extension Program pilot project conducted with research scientists from the Florida Fish and Wildlife Research Institute to provide a regional snapshot of goliath grouper size distribution and abundance at spots they are known to congregate at throughout the region.
We are hopeful this approach may provide a cost-effective strategy for scientists to evaluate trends in goliath grouper abundance This was a pilot project to determine if a sufficient number of trained volunteers could collect valid data in such a comprehensive manner.
The true value of the effort will only be realized if it can be expanded and conducted in future years. Information is still coming in and being analyzed by fisheries scientists, so stay tuned for updates in future Marine Scene editions.
So far the results look promising and, although not certain, we hope to repeat the project next year. Over 60 scientists and volunteers participated and counted hundreds of goliath groupers. It would be completely impossible for a small team of research scientists to accomplish such a task.
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Why count goliath grouper?
Management of the goliath grouper, the largest member of the sea bass family, has become an intensively debated issue in recent years. Historically, goliath grouper was relatively common and highly conspicuous in portions of its range. However, it proved to be vulnerable to fishing pressure. Due to significant declines in abundance through the 1960s-80s, taking of goliath grouper was prohibited in U.S waters in 1990.
In 1994, goliath grouper was listed as critically endangered on the IUCN World Conservation Union’s Red List of Threatened Species. The species has since been protected in Brazil (2002), Puerto Rico (2004) and the U.S. Virgin Islands (2004).
Following the granting of protected species status, abundance has appeared to increase over the past decade, but the extent of the recovery is not clearly understood. Information on historical abundance is limited and not precise. Likewise, information on perceived increase in abundance over the past decade is limited, and it is difficult for fisheries managers to truly understand the extent to which it has recovered throughout its geographic range.
The most recent stock assessment (2004) indicated that the goliath grouper population in Florida waters was recovering, but that it may not experience full recovery until 2020 or later. Because the harvest of goliath grouper is prohibited, the conclusions of the stock assessment were made in the absence of certain types of biological information that is typically available for other species through the examination of harvested individuals.
It must be stressed that the information provided by the recent Goliath Grouper Count will be far from sufficient to answer the question of the present status of the stock. Instead, it is hoped the results will provide one small piece of the overall puzzle, especially if it can be conducted in future years. The Florida Fish and Wildlife Conservation Commission will conduct a statewide assessment later in 2010 and NOAA’s National Marine Fisheries Service will conduct a more comprehensive assessment in 2014.
Goliath grouper management
If you walk the fishing docks of Florida and talk with anglers, fishing guides and scuba divers you will quickly learn that management of goliath groupers is a controversial subject. On one hand, recovery of goliath grouper populations is a conservation success story.
On the other hand, some folks believe that the resurgence of this giant fish has upset the natural balance of fish on reefs. It just seems to make sense that when these large fish are abundant they would prey upon and reduce the abundance of other reef fish in the area.
This perception is reinforced by the fact that goliath grouper will opportunistically strike hook or speared fish. Many anglers complain that such activity can make it essentially impossible to fish an area with any hope of successfully bringing reef fish to the boat.
However, the picture is not as clear cut as it first seems — few things are in fisheries management. To date, stomach content analysis of goliath groupers has documented that about 85% of their diet consists of crustaceans (mostly crabs). The remaining 15% primarily consists of slow-moving fishes such as burrfish, catfish and toad fish. In the stomach contents of over 200 goliath grouper, no grouper and only a few snapper — about 3% — were found. Stomach contents are representative of prey eaten just prior to capture, and provide a short-term view of diet.
However, for an understanding of diet over long periods, as well as goliath grouper’s position in the food chain scientists use a method called stable isotope analysis. Results of this type of analysis show a relatively low position in the food chain, similar to that of pinfish, Lagodon rhomboids. These results tend to confirm that goliath grouper do not usually eat high-level predators such as groupers and snappers. This does not mean that a hungry goliath grouper, as many anglers have experienced, won’t opportunistically go after a struggling fish on a line or fish wounded by spear fishing.
However, the perception that these goliath groupers are consuming healthy groupers and snappers is not supported by scientific evidence. For an excellent review of goliath grouper biology visit the Colemen-Koenig lab at Florida State University.
What will be the future of goliath grouper management?
This is a good but difficult question to answer, and obviously I don’t have the answer. My guess would be that, given the previous decline in goliath groupers, fishery managers would be reluctant to take action in allowing some sort of limited goliath grouper harvest until they have a complete understanding of the population condition and what level of harvesting would be sustainable.
Right now the Florida Sea Grant Extension Program, as always, is guided by its research and outreach mission of providing scientifically accurate, unbiased information. We will work with scientists, anglers and divers to try and develop the best possible information that will enable resource managers to sustainably manage the resource in a manner that is fair to all resource users. Thank you volunteers!
Again, this ambitious project would not have been possible without the dedication of numerous volunteers who donated their time and boats to this effort. These are the type of people who truly try to make a difference. If we undertake the project again next year, we will be asking for help. We may be able to arrange charter and volunteer boats, but participants will have to cover their own costs.
Article compiled by:
UF/IFAS Collier County Sea Grant Extension
UF/IFAS Charlotte County Sea Grant Extension
UF/IFAS Lee County Sea Grant Extension
UF/IFAS Manatee County Sea Grant Extension