Caribbean Reef Fishes

December 3, 2012

Katriina Ilves diving

More than 20 feet under the ocean’s surface near Andros Island in the Bahamas, Dr. Katriina Ilves pauses to observe a coral reef teeming with marine life. The Academy’s Chaplin postdoctoral scientist* rarely stops to take it all in during a dive, but when she does, she’s struck by her surroundings.

Large fishes swim above the undulating reef, radiant with its prismatic hues, and small fishes dart around sea fan corals and sponges below. Parrotfishes use their plate-like teeth to scrape algae off the coral structure that feeds and shelters them, creating an erratic crackling that counters the rhythmic bubbling of Ilves’ breathing.

Buoyant in the water, Ilves snaps into action, scooping a rainbow of fishes into a hand net. Constantly attentive to her airflow, she must stay in sight of a fellow diver while she searches for fishes for the Academy’s collection.

Ilves and her team emerge after an hour underwater. They quickly head ashore to identify and sort the collected fishes, tag and photograph them, take tissue samples, and preserve the fishes for future study.

It’s a collaborative effort. For the Andros expedition, Ilves’ team included ichthyologists Carole Baldwin of the Smithsonian and Mark Westneat of Chicago’s Field Museum; coral and fish experts Andrea Quattrini and Ron Eytan; and ichthyology affiliate Gordon Chaplin, whose connection to the project took root more than 60 years ago at the Academy.

Ilves’ research builds upon that of Gordon Chaplin’s father, Academy patron and reef-fish enthusiast Charles C.G. Chaplin, and Academy Ichthyology Curator Dr. James Böhlke. Beginning in the 1950s, they collected reef fishes all around the Bahamas, including near New Providence Island and Andros Island—the same areas where Ilves collected this year and during her 2010 trip to the region. With support from the National Geographic Society’s Committee for Research and Exploration and private donations, she is comparing her data on fish diversity and relative abundance to the historical data to determine how these reef communities have changed over time.

“The collections help us understand what the reef community was like before the major onset of development and tourism in the Bahamas and before changes in temperature and ocean chemistry that may be connected to climate change,” Ilves says.

Some coral reef habitats have changed drastically over the past five decades as development and tourism have expanded in the Bahamas. Coastal development as well as wastewater, fertilizer, and pesticide runoff have caused habitat degradation in reef areas close to human population centers. According to Ilves, these kinds of changes can affect reef food supplies and cause fierce competition for space on reefs.

Ilves found striking differences when comparing her 2010 data to Böhlke and Chaplin’s data on reef-fish communities near New Providence, home to Nassau, the largest city in the Bahamas. Plant-eating fishes, particularly parrotfishes, were more prevalent in 2010 than during the historical time period—likely due to an increase in algae, their main food supply, which often thrives in polluted environments.

Comparing the historical data to the 2010 data also indicated a relative increase in squirrelfishes, which spend their days inside the crevices of the reef, and a relative decrease in cardinalfishes, smaller fishes that inhabit this same area. Ilves posits that squirrelfishes may be stronger competitors for limited space in the now-degraded habitat.

 “We want to see if there are the same kinds of changes around Andros, which is 30 miles away but the least inhabited island in the area,” Ilves says. “Our hypothesis is that perhaps the reefs near Andros have remained in a more natural state than those around New Providence Island, and therefore what we’ll find at Andros is that the communities today will more closely resemble communities of 50 years ago.”

With the recent implementation of conservation efforts throughout the Caribbean, reef habitats could improve, Ilves hopes. Whether she returns to the region again for additional collecting depends upon future environmental and developmental changes in the region as well as the results from this year’s fieldwork. As Ilves analyzes her data, her Academy connection strengthens her ability to draw conclusions about how reef-fish communities have changed over time.

“We have access to this long-term data set, which for marine systems is unbelievably rare,” Ilves says. “It’s great to be able to use those data to address questions about how fish communities respond to the degradation of their habitat and whether such ecosystem changes can be reversed.” 

Meet Dr. Ilves and her colleagues at the Academy on December 8 during Fish Discovery Weekend. On both Saturday and Sunday, December 8 and 9, see rare and bizarre fish displays, meet fish scientists, and enjoy hands-on fun. Ichthyology Collection Manager Dr. Mark Sabaj Pérez will share stories about his field research in the Amazon, Mongolia, and closer to home. Meet more Academy ichthyologists and ask them about our fish collection representing more than 10,000 species from around the world. Children can make a fish hat and play an adaptation game. Free with museum admission.

This story was adapted from the Fall 2012 issue of Academy Frontiers. Photo by Andrea Quattrini.

*Ilves is now a Rebanks Fellow in the Department of Natural History, Ichthyology, at the Royal Ontario Museum.

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