Freeing Nemo: Aquarium owners releasing non-native fish could endanger marine ecosystems
University of Washington
April 7, 2004
Flushing your pet tropical fish to set it free is a bad idea. So is releasing it at the beach.
Intentional and unintentional aquarium releases have been a leading cause of freshwater fish invasions, but now researchers from the University of Washington and the Reef Environmental Education Foundation have found 16 non-native species of fish – apparently set free from home aquariums – in ocean waters off the southeast coast of Florida.
This is an unprecedented number of non-native marine fish in a concentrated geographic area, says Brice Semmens, a UW doctoral student in biology and lead author of a paper published in the journal Marine Ecology Progress Series.
Using data on the aquarium trade and shipping traffic, the study is the first to convincingly demonstrate that well-meaning pet owners can cause a "hot spot" of non-native tropical marine fish, Semmens says. The 16 species were found in 32 different locales along the coast of Broward and Palm Beach counties and in the upper Florida Keys. Some were in the Florida Keys National Marine Sanctuary.
Most of the species were seen at more than one place meaning more than just a few aquariums have been dumped, Semmens says. It is not clear which, if any, of the non-natives have established breeding populations, he said.
Emperor angelfish, imported by the U.S. aquarium industry in very large numbers, were the most commonly sighted non-native. Photo by Paul Humann.
The more times a species is released, however, the greater the chance of establishment, says Walt Courtenay, fisheries biologist with the U.S. Geological Survey in Gainesville, Fla., who is known around the world for his expertise on exotic fishes. He is not a co-author of the published paper.
"Typically, I'd say aquarium owners are more concerned with the status of our marine ecosystems than the general public is, yet many appear unaware of the potential pitfalls of releasing pets into the wild," Semmens says.
The study relied on information submitted by volunteer divers and snorkelers through the Exotic Species Sighting Program of the Reef Environmental Education Foundation, or REEF, based in Key Largo, Fla. Sightings were confirmed with photographs, video or corroboration by other divers.
The introduced species are native to the tropical western Pacific and/or Red Sea. Emperor angelfish, with their blue masks and bodies striped in blue and gold, were the most commonly sighted non-native species and are imported by the aquarium industry in relatively large numbers. Indeed, the researchers found a compelling correlation between how commonly ornamental marine species are imported and how often they were sighted. Another commonly sighted non-native was yellow tang, a bright yellow oval fish that is the most commonly imported species of the U.S. aquarium trade.
In contrast, Semmens says it is unlikely the exotics arrived in the ballast water of ships. If the fish were being introduced through ship ballast, one would expect the native ranges of the fish to correlate to where the ballast water comes from. Analyzing data on shipping traffic to Florida ports, Semmens and his co-authors found no support for this correlation.
While only a small number of introduced species might have devastating impacts, scientists are unable to predict which species will be destructive. The largest set of intentionally released marine fish was carried out in temperate coastal and inland seas of Russia in the 20th century. Sixteen species became established, with ecologically and economically devastating results, including harm to valuable fisheries, parasite introductions and the endangerment and extinction of native species.
"Releasing non-native reef fish is like playing Russian roulette with tropical marine ecosystems," Semmens says. Then, too, even if introduced species do not have dramatic impacts, their presence is unnatural and unwanted.
"Divers visit the reefs of Florida to see the region’s natural beauty and diversity. It is a unique and magical experience to dive on these reefs. Adding new species to the region is comparable to adding a few finishing touches to one of da Vinci’s masterpieces."
Co-authors of the paper are Eric Buhle and Anne Salomon, both UW doctoral students in biology, and Christy Pattengill-Semmens, science coordinator for the Reef Environmental Education Foundation.
Aquarium keepers need to be educated about the proper disposition of animals in their care, according to Paul Holthus, executive director and president of the Marine Aquarium Council, an international non-profit organization based in Honolulu that focuses on the way tropical fish are collected and handled before they are purchased.
"While it is against the law to release non-native marine fish into coastal waters, it’s a problem that can’t easily be policed," Semmens says. The authors say that education programs for dealers and aquarists could curtail exotic species introductions if implemented properly. Such programs would need to highlight the problems of introduced species and provide ways for aquarium owners to sell or trade unwanted fish.
This emperor angelfish (Pomacanthus imperator) was documented in Florida by Jason McCullough. Several additional sightings have been reported in the Pompano Beach area.
Introduced orbicular batfish (Platax orbicularis) (top) mingling with Caribbean-native Atlantic spadefish (below) on Molasses Reef, Florida Keys. Photo by REEF member John Stuart.
One of the more well known exotic species in the western Atlantic, the red lionfish (Pterois volitans) has been seen from New York to Bermuda to Florida. This picture was taken in Florida by REEF member Joe Froelich.
This bluering angelfish (Pomacanthus annularis) was documented on a reef near Pompano Beach, Florida by Deborah Devers, Vone Research.
The semicircle angelfish (Pomacanthus semicirculatus), also known as the Koran angelfish in the aquarium industry, was photographed by Linda Ianniello in Boca Raton, FL.
This "golden" angelfish is not an exotic species, but rather a genetic variant of the Atlantic-native queen angelfish (Holacanthus ciliaris). It was photographed by Linda Ianniello in Boca Raton, FL.
The Arabian angelfish (Pomacanthus asfur) was photographed by Tom Ferguson, taken in Dania, FL.
Here you can see the Arabian angelfish swimming near Atlantic-native tomtate grunts. Photo by Tom Ferguson, taken in Dania, FL.
The yellowbar angelfish (Pomacanthus maculosus), should not be mistaken as an Arabian angelfish. The location of the yellow marking is farther back on the body and it lacks the blue wash seen on the Arabian's head. This was taken in Pompano Beach by Deborah Devers, Vone Research.
This sailfin tang (Zebrasoma desjardinii) was photographed off Commercial Pier in Lauderdale-by-the-Sea by REEF member Denise Mizell in the summer of 1999.
A different species of sailfin tang (Z. veliferum). Photo by Linda Ianniello, taken at San Remo Reef, Boca Raton.
A racoon butterflyfish (Chaetodon lunula) has been sighted a few times on a reef in Boca Raton by a REEF surveyor. (this photo is not from Florida but is shown for identification).
A yellow tang (Zebrasoma flavescens) has been sighted by REEF surveyors near Boyton Beach. It can be distinguished from the juvenile phase of the Atlantic-native blue tang by the white spine (blue tang have a yellow spine at all phases of life).
This yellowtail sailfin tang (Zebrasoma xanthurum) was photographed by REEF member Peter Leahy in Boca Raton. It can be distinguished from a transitioning blue tang (one between juvenile and adult) by the lack of the yellow spine.
An orangespine unicornfish (Naso lituratus) was documented by REEF surveyor Peter Leahy on a reef in Boca Raton.
(this photo is not from Florida but is shown for identification).
This moorish idol (Zanclus cornutus) was photographed on a wreck in Pompano Beach by Michael Barnette in the January 2001.
University of Washington Newsroom: http://www.washington.edu/newsroom/news/2004archive/04-04archive/k040704a.html
Reef Environmental Education Foundation's Exotic Species Sighting Program: http://www.reef.org/exotic
