Fish Are Remarkable Architects

To the casual observer in the Gulf of Mexico, the seemingly sluggish red grouper is more of a couch potato than a busy beaver. But a new study led by researchers at The Florida State University reveals the fish to be both architect and ecosystem engineer.Most abundant along Florida's west coast but also found on watery ledges and in crevices and caverns from North Carolina to Brazil, the red grouper excavates and maintains complex, three-dimensional structures that provide critical habitats for the spiny lobster and many other commercially important species in the Gulf of Mexico. The researchers watched it work hard to remove sand from the sea floor, exposing hard rocks crucial to corals and sponges and the animals they shelter.In fact, the red grouper's sandy architecture is a monument to the interconnectedness of species and the vital role such connections play in the structural and functional diversity of the ocean, suggests Felicia C. Coleman, director of Florida State University's Coastal and Marine Laboratory."Watching these fish dig holes was amazing enough," Coleman said, "but then we realized that the sites they created served to attract mates, beneficial species such as cleaner shrimp that pick parasites and food scraps off the resident fish, and a variety of prey species for the red grouper. So it is no surprise that the fish are remarkably sedentary. Why move if you are clever enough to make everything you need come to you?"Coleman and Christopher C. Koenig -- her spouse and fellow faculty member in the Department of Biological Science -- describe their study in a paper ("Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico") published online Jan. 9 in The Open Fish Science Journal. Their co-authors are Kathryn M. Scanlon, of the U.S. Geological Survey, Woods Hole, Mass.; Scott Heppell and Selena Heppell, Department of Fisheries and Wildlife, Oregon State University; and Margaret W. Miller, of the National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Fla."Red grouper are the 'Frank Lloyd Wrights' of the sea floor," said University of California-Davis Professor Susan Williams, who collaborated with Coleman on an earlier, related study. "Its sea-floor associates include commercially valuable species such as vermilion snapper, black grouper and spiny lobsters. If the groupers are overfished, the suite of species that depends on them is likely to suffer."Working along the West Florida Shelf, Coleman and colleagues observed the red grouper's excavating activities during both its juvenile stage in inshore waters and its adult stage at depths of 300 feet."We suspected that the groupers created the habitat," Coleman said. "We found through a series of experiments that they not only dug the holes but also maintained them by carrying mouthfuls of sediment from the center of the pit to the periphery and expelling them through their gills and mouths, then brushing off the rocks with their tail fins."As juveniles, red grouper excavate the limestone bottom of Florida Bay and elsewhere, exposing "solution holes" formed thousands of years ago when sea level was lower and freshwater dissolved holes in the rock surface. When sea level rose to its present state, the solution holes filled with sediment. By removing the sediment from them, the fish restructure the flat bottom into a three- dimensional matrix, which is enhanced by the settlement and growth of corals and sponges. Spiny lobsters are among the many species that occupy those excavations, especially during the day when seeking refuge from roving predators.Loss of this habitat -- through the loss of red grouper due to intensive fishing -- has obvious consequences to the lobster fishery of South Florida, Coleman said. She warns that habitat engineers, like foundation species, must be maintained in a healthy state, or the consequences to fishery production could be severe."You can't remove an animal that can dig a hole five meters across and several meters deep to reveal the rocky substrate and expect there to be no effect on reef communities," Koenig said. "The juveniles of a species closely associated with these pits, vermilion snapper, are extremely abundant around the offshore excavations. It is possible that the engineered habitat is significant as a nursery for this species, which other big fish rely on as food. One could anticipate a domino effect in lost diversity resulting from the loss of red grouper-engineered habitat."Suggested changes in fisheries management intended to reduce bycatch of sea turtles in the long-line fishery by pushing the fleet further offshore would increase the fishing pressure on red grouper and other ecosystem engineers, such as tilefish, found at greater depths, contends Coleman."Imagine the impact not only on red grouper and tilefish but also on a suite of deep-water grouper for which we have very little information, other than the fact that some of them are critically endangered," she said.

Whopping Fish Declared New Species

The goliath grouper, including the Atlantic variety from Cuba (shown here), sports five rows of teeth in the lower jaw. The teeth help grouper to hold tight to prey, which they usually swallow whole. Credit: Rachel Graham/Wildlife Conservation Society Full Size 1 of 1The goliath grouper, including the Atlantic variety from Cuba (shown here), sports five rows of teeth in the lower jaw. The teeth help grouper to hold tight to prey, which they usually swallow whole. Credit: Rachel Graham/Wildlife Conservation Society A man-sized grouper that trolls the tropical waters of the Eastern Pacific Ocean for octopuses and crabs has been identified as a new fish species after genetic tests. Called the goliath grouper, the fish can grow to six feet (1.8 meters) in length and weigh a whopping 1,000 pounds (454 kg). Until now, scientists had grouped this species with an identical looking fish (also called the goliath grouper, or Epinephelus itajara) living in the Atlantic Ocean. "For more than a century, ichthyologists have thought that Pacific and Atlantic goliath grouper were the same species," said lead researcher Matthew Craig of the Hawaii Institute of Marine Biology, "and the argument was settled before the widespread use of genetic techniques." Once upon a time, about 3.5 million years ago — before the Caribbean and the Pacific were separated by present-day Panama — they were, in fact, the same species. Now, DNA tests have revealed the two populations have distinct genes, indicating they likely evolved into two separate species after their ocean homes were divided by Central America. Scientists disagree about how to define the term "species" and what separates species from one another biologically, though some say that a species is a group that can mate with one another and produce offspring that are not sterile. However, this biological definition doesn't always hold up, for instance, with coyotes and wolves (considered separate species), which can successfully produce fertile offspring. In this study, the scientists relied on differences in the fishes' genetic codes to establish the separate grouper species. The new Pacific species, now designated as Epinephelus quinquefasciatus, is described in a recent issue of the journal Endangered Species Research. The Atlantic variety, E. itajara, is currently listed as critically endangered by the IUCN, or International Union for Conservation of Nature. Due to its scarcity, E. quinquefasciatus also may be considered critically endangered. "In light of our new findings, the Pacific goliath grouper should be treated with separate management and conservation strategies," said researcher Rachel Graham of the Wildlife Conservation Society in New York. The research was funded by Programa Petrobras Ambiental, Conservation International Brazil to Projeto Meros do Brasil, The Summit Foundation, National Science Foundation and Hawaii Institute of Marine Biology.

Twenty Of World's 162 Grouper Species Threatened With Extinction

The first comprehensive assessment of the world’s 162 species of grouper, a culinary favorite and important commercial fish, found that 20 are threatened with extinction unless proper management or conservation measures are introduced। Eight species previously were listed by the World Conservation Union (IUCN) as under extinction threat, and the new assessment proposes adding 12 more.

A panel of 20 experts from 10 nations determined the extinction threat facing groupers, which are the basis of the multimillion-dollar live reef food fish trade based in Hong Kong and comprise one of the most valuable groups of commercial fishes in chilled fish markets of the tropics and sub-tropics. Around the world, consumers pay up to $50 per kilogram for grouper.
“This shows that over-fishing could decimate another major food and economic resource for humans, similar to the loss of the cod stocks off New England and Canada that has put thousands of people out of work,” said Roger McManus, a senior director of Conservation International’s Marine Program.
The ground-breaking workshop at the Department of Ecology and Biodiversity of the University of Hong Kong was the first systematic assessment of the commercially important species, said Dr. Yvonne Sadovy, Chair of the IUCN Grouper and Wrasse Specialist Group and Associate Professor at HKU.
“The results are worrying and highlight the urgent need for fishery management, more effective marine protected areas (MPAs), and more sustainable eating habits for consumers of these fishes,” said Sadovy, who organized the workshop.
The workshop is part of a worldwide study of marine life called the Global Marine Species Assessment (GMSA) by IUCN, Conservation International and numerous other partners that provides scientists with baseline data for analyzing threats to ocean species.
“This assessment forms part of a growing focus on over-fishing and conservation concerns for fishes in general,” said GMSA Director Kent Carpenter.
The workshop identified the need to better protect outer reef areas and to manage spawning aggregations of many of the threatened grouper species. Outer reef areas are often not incorporated into MPAs, and spawning aggregations necessary for continued reproduction of many grouper species are rapidly eliminated by uncontrolled fishing. Increasing international trade to meet an insatiable demand for grouper poses a particularly major threat.
The workshop outcome serves as another reminder of the need for sustainable fishing and consumption of important fish species. The threatened groupers are naturally vulnerable to over-fishing, and the continued decline of fish populations can threaten food security and livelihoods in source countries. Their pending inclusion on the IUCN Red List of threatened species also reflects the widespread failure to successfully manage fisheries associated with coral reefs.
Groupers are among the oldest fish on coral reefs, with some species reaching more than 50 years old. Several species only reach reproductive maturity later in life, making them particularly vulnerable to fishing before they mature. In addition, commercial fishing that targets reproductive gatherings of adults further hinders replenishment of unmanaged populations.
The threatened groupers include two species of coral trout grouper, which are mainstays of the live reef food fish trade in Hong Kong. Both can be found in Hong Kong fish markets, but they face heavy and unmanaged fishing pressure that is rapidly reducing their populations.
In North and South America, heavy fishing of grouper for the chilled fish markets also poses a significant threat. The Nassau grouper, once one of the most commonly landed groupers in the islands of the Western Atlantic Ocean, now is listed as Endangered under the U.S. Endangered Species Act and has virtually disappeared from most Caribbean reefs.
Adapted from materials provided by Conservation International.