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

How will climate change affect different species? Will organisms be able to adapt quickly enough to survive in a rapidly changing environment?

Researchers at the University of Oxford are attempting to predict this with small, short-lived birds like the great tit (Parus major). In a study published this week in PLoS Biology, the scientists discovered that great tits living in a forest near Oxford have been able to survive and adapt to a 1°C temperature increase over the past 50 years.

After analyzing those 50-plus years of data collected on the birds in their habitats, the authors studied when the birds lay their eggs relative to spring temperatures, as well as how the birds have tracked the shifts in peak caterpillar numbers caused by the changes in temperature. They found that the birds are now laying their eggs an average of two weeks earlier than they did 50 years ago, primarily as a result of phenotypic plasticity.

Phenotypic plasticity enables organisms to adjust their behavior rapidly in response to short-term changes in the environment. Jack Dumbacher, curator and department chair of Ornithology & Mammalogy here at the Academy, explains, “It’s heritable but it’s not an evolutionary, or genotypic change. There’s no change in the genes.”

The authors’ predictions show that phenotypic plasticity could allow the great tits—and similar birds—to survive warming of 0.5°C per year, easily outpacing the current worst-case scenario of 0.03°C from climate models.

Dumbacher says that while this study is interesting and a good reminder how adaptable one species may be, he emphasizes that temperature increase is just one effect of climate change. Temperature variance and extreme weather are other effects with unknown results to various ecosystems, he says. In addition, Dumbacher reminds us that the great tits and caterpillars play roles in a much larger ecosystem, where the web of relationships is so interdependent that one small change to one small organism in that web could easily affect other species.

One effect of climate change that Dumbacher stresses (and the study does not mention) is invasive species. As temperatures change, habitat ranges change for different species, which can result in one species invading the habitat of another. One example Dumbacher gives is the Northern Spotted Owl (Strix occidentalis caurina). These birds have been able to adapt to a 1°C temperature increase over the past 100 years but are now facing a fierce competitor in the Barred Owl (Strix varia), an eastern species that now finds itself in the same territory as the Northern Spotted Owl.

“Climate change is more than a one degree temperature increase,” Jack says. “And while a species may demonstrate plasticity within different temperature regimes, it’s likely that ecosystems are not as adaptable. This why climatologists have such a difficult time predicting the effect of climate change on organisms.”

Image: Luc Viatour/Wikipedia