Earlier this year, we produced a video documenting Academy researcher Luiz Rocha’s work in Belize studying invasive lionfish. These predators, originally from the Indo-Pacific, found their way to the northwest Atlantic in the 1990s—likely through an aquarium release—and have steadily moved south over the past fifteen years.

The lionfish are wreaking havoc in the area because they voraciously gobble up smaller, native fish—threatening everything from coral reef ecosystems to local economies based on fishing and tourism. In addition, eradication appears impossible and whatever is keeping them in check in their native Indo-Pacific habitats—researchers around the world are trying to find out what—appears to missing in the Atlantic.

“Prey in the Indo-Pacific could simply be more aware of the danger lionfish pose,” Rocha says. “There could also be parasites keeping the lionfish in check in their native habitats.”

Bad
A recent study in PLoS One determines that humans may be the only threat to lionfish in their new home. An international research team looked at whether native reef predators such as sharks and groupers could help control the population growth of lionfish in the Caribbean, either by eating them or out-competing them for prey.

The team surveyed 71 reefs over three years, in three different regions of the Caribbean. Their results indicate there is no relationship between the density of lionfish and that of native predators, suggesting that, “interactions with native predators do not influence” the number of lionfish in those areas.

The researchers did find that lionfish populations were smaller in protected reefs, but researchers attributed the lower numbers to targeted removal by reef managers, rather than consumption by large fishes in the protected areas. As Rocha mentioned in the video last spring, encouraging the hunting and human consumption of these spiny fish may be reefs’ only hope.

Ugly
Recent submersible dives deep off the coast of Fort Lauderdale, Florida reveal that these invasive lionfish populations aren’t just spreading southward—they’re also heading to great depths, out of the reach of their only predators, human hunters.

“We expected some populations of lionfish at that depth [300 feet], but their numbers and size were a surprise,” says Stephanie Green, of Oregon State University, who participated in the dives.

The lionfish are growing to an unusually large size—as much as 16 inches. “A lionfish will eat almost any fish smaller than it is,” Green says. “Regarding the large fish we observed in the submersible dives, a real concern is that they could migrate to shallower depths as well and eat many of the fish there. And the control measures we’re using at shallower depths—catch them and let people eat them—are not as practical at great depth.”

Rocha confirms this. “Even if control efforts are successful in shallow water, we can’t reach these deep fish.” And the lionfish at great depths can easily move to shallower areas. In addition, “these larger fish produce more eggs,” Rocha says, creating even larger populations.

(Rocha is hoping to join on subsequent dives. He was invited on this recent submersible dive, but was attending a conference on Indo-Pacific fish in Japan at the time. A video of the dives is available here.)

Good
We want to end on an upbeat note, and Rocha has a recent study in Marine Ecology Progress Series about the spread of lionfish down the coast of South America and into Brazil. The fish haven’t reached that far yet, but given their rapid spread, it seems to be only a matter of time.

Working with other Brazilian researchers, Rocha investigated movements of various fish species across the Amazon-Orinoco plume (AOP), where the Amazon and Orinoco rivers meet the Atlantic Ocean. The study describes the AOP as “a large freshwater and sediment runoff between the Caribbean and the Brazilian Provinces that represents a ‘porous’ barrier to dispersal for reef organisms.”

The scientists found that while a few “vagrant” species recently crossed the barrier heading north, “species headed south don’t spread as quickly,” according to Rocha. “The currents make it tricky to cross.”

This could be the first bit of good news in stopping the spread of lionfish. “This means we can keep an eye on it and control the lionfish as they cross, keeping their numbers down,” Rocha says.

Next
Rocha and colleagues here at the Academy and in Europe are beginning a population genomic study of the invasive lionfish. This study will look at fine-scale genetic diversity of lionfish among the different Caribbean islands. Rocha will start collecting samples in two weeks in Curaçao. The samples will then be analyzed by Academy researchers—including Rocha’s wife, Claudia—here at the Center for Comparative Genomics.

“We want to see if there is gene exchange between different island populations,” Rocha explains. “This will help us determine how successful local efforts to control lionfish can be if larvae are coming from other locations. This study can help inform how resources are used to control different populations.”

The fight against invasive lionfish continues…

Image: Alexander Vasenin/Wikipedia

When Academy curators Terry Gosliner and Luiz Rocha traveled to Saudi Arabia this spring to study marine life in the Red Sea and the Gulf of Aden, the contrast awaiting them couldn’t have been starker. Beyond the enclosed campus of King Abdullah University of Science and Technology (KAUST), about an hour north of Jeddah, stretched a parched terrestrial landscape with daytime temperatures hovering near 105 degrees. But once the researchers boarded the 80-foot-long catamaran, they soon ventured into a rich underwater landscape teeming with life.

For the two-part, KAUST-sponsored expedition, Gosliner, Rocha, and a team of 15 international scientists spent two weeks documenting fish diversity in the Red Sea. On the second two-week portion, Rocha and five other researchers continued to explore tropical reefs within the Gulf of Aden, in the territorial waters offshore from Oman. The invitation to collaborate on this general, comprehensive survey arose from Rocha’s participation at a 2012 KAUST conference organized by Michael Berumen that produced a research paper coauthored by Rocha, Berumen,  Brian Bowen, an associate researcher at the University of Hawaii, Joseph DiBattista, a post-doctoral fellow at KAUST, and Michelle Gaither, a post-doctoral fellow at the Academy.

“The sand dunes and rugged mountains along the Saudi coastline reminded me of Baja, California,” says Gosliner. “And the Red Sea’s narrow body of water, caused by tectonic activity and fault lines, is not unlike the Sea of Cortez,” he adds. “That said, the Red Sea has unique features that make it very interesting from a scientific perspective.”

The Arabian Peninsula, wedged between Northeastern Africa and Asia, is bordered by oceans and seas on three sides. The Red Sea, along its western coastline, has a very small, shallow connection with the Indian Ocean. “Because of this geographic separation, it has a lot of unique species,” says Rocha. “There is a lot of endemism in the Red Sea.”

Coastal Oman, at the southeastern end of the peninsula, is open to the Indian Ocean. “It also has many unique species,” says Rocha, “but for a different reason.” The sea is more affected by upwelling that does not impact marine habitats in the rest of the Indian Ocean. Upwelling, caused by wind blowing from coast to ocean, pushes away warm waters on the ocean’s surface. Cold water rises from below to fill the gap.

“You won’t find coral reefs in these conditions—they can’t thrive in cold temperatures,” says Rocha. “Not only is this fauna unique, but the tropical reefs in the Western Indian Ocean are the least known in the world.”

The researchers brought back 350 specimens of nudibranchs and fish for morphological and genetic analysis. The new specimens fill a surprising gap in the Academy’s renowned fish collection.

“We have 250,000 jars of fish at the Academy, about 3 million specimens and 11,000 species,” says Rocha. “Almost everything we brought back is new to the collection. We had very few fish from Oman.”

Another surprise was Gosliner’s assessment of the leading environmental threat to sustaining the region’s biodiversity. “This is an active zone of human activity,” he explains. “To the north, it’s a major shipping corridor through the Suez Canal into the Mediterranean. In the south, you have the Somali pirates.”

And the source of the most severe harm to the ocean biome?

“Overfishing,” says Gosliner. “That has greater impact than all the other activities put together.”

Last but not least: How did the Red Sea get its unusual name? According to Gosliner, a leading theory is that periodic outbreaks of algal blooms caused by dinoflagellates temporarily changed the water’s color.

“When early explorers toured the area,” he says, “they may have seen that phenomenon we now call a ‘red tide.’ But the waters are a sparkling turquoise blue most of the time. So the Red Sea is truly a misnomer.”

Barbara Tannenbaum is a science writer working with the Academy’s Digital Engagement Studio. Her work has appeared in the New York Times, San Francisco Magazine and many other publications.

Image: Terry Gosliner

What the…?

Remember this video we produced a while ago about the super cool mimic octopus? It compresses and conforms itself to look like a sea snake, flatfish, or lionfish—adjusting its look for different situations. Thanks to these brazen habits, it can swim in the open with relatively little fear of predators.

Well, it now appears the mimic octopus has a companion mimic. Last summer, Godehard Kopp of the University of Gottingen, Germany took this video while diving in Indonesia. A black-marble jawfish is seen closely following a mimic octopus as it moves across the sandy bottom. The jawfish has brown-and-white markings similar to the octopus and is difficult to spot among the many arms. The octopus, for its part, doesn’t seem to notice or care.

Kopp sent the video to Rich Ross and Luiz Rocha here at the Academy, who identified the jawfish species. Since this association had not been recorded before, they published their observations last month in the scientific journal Coral Reefs. The authors surmise that the jawfish hitches a ride with the octopus for protection, allowing it to venture away from its burrow to look for food—a case of “opportunistic mimicry.”

“This is a unique case in the reefs not only because the model for the jawfish is a mimic itself, but also because this is the first case of a jawfish involved in mimicry,” says Rocha, assistant curator of ichthyology. “Unfortunately, reefs in the Coral Triangle area of southeast Asia are rapidly declining mostly due to harmful human activities, and we may lose species involved in unique interactions like this even before we get to know them.”

Luiz Rocha and his colleagues set about finding out how coral reef fish make long distance journeys across the Atlantic (about 3500km/2200 miles near the equator) or the freshwater and sediment discharges of the Amazon and Orinoco rivers in South America (about 2300 km/1500 miles).

Coral reef fish don’t move a lot as adults, so the long held belief was that the fish dispersed in their larval stage. The larval stage can last 10 days for some species and 100 days for others and it may take 50 days to cross the Atlantic. Looking at the variables and the distribution for 985 species, the researchers found that the larval stage actually had little to do with which fish crossed the large distances and barriers—or how they managed to do it.

Dispersal seems to factor on other specifics—the size of the adult fish, whether the fish could use flotsam, or sargassum mats, as habitats across the barriers and if the fish were generalists—able to adapt to new habitats and food. Luiz and his collaborators published their findings last week in the Proceedings of the Royal Society: B. From the abstract:

Successful establishment after crossing both barriers may be facilitated by broad environmental tolerance associated with large body size and wide latitudinal-range. These results highlight the need to look beyond larval-dispersal potential and assess adult-biology traits when assessing determinants of successful movements across marine barriers.

Luiz gave us some examples:

The Brown Chromis (Chromis multilineata) is a great example of a fish that has a short larval stage but crosses barriers using floating substrate.

Many species of parrotfishes in the Caribbean have long larval stages but are restricted to the Caribbean, and found neither in Brazil nor in the other side of the Atlantic.

Some species of wrasses of the genus Halichoeres cross the Amazon barrier but don’t survive on the other side because they can’t find their preferred habitat. In this genus, the specialists tend to have smaller geographical ranges than the generalists. One of the examples is Halichoeres poeyi, a wrasse that lives not only in coral reefs, but also rocky reefs and seagrass. This wrasse is continuously distributed from South Brazil to Florida, and all of the other (more specialized) species in this genus are different in either side of the Amazon barrier.

The study built upon a paper the team published in 2008—a culmination of five years of work, creating a database of 1,300 Atlantic species of coral reef fish. The database includes many variables for each species—biogeographic data, reproductive mode (which is a proxy for length of the larval stage), spawning information, size as an adult, habitat needs, and more.

Luiz Rocha joined the Academy less than a month ago, as a curator of ichthyology, specializing in coral reef fish. Originally from Brazil, he fell in love with these fish at an early age—snorkeling since the age of five! He comes to the Academy from the University of Texas. Stay tuned for more of his research.

Image by John E. Randall, WorldFish Center – FishBase, EOL