Wednesday, July 20, 2016

Reef Invaders

The prettiest pest I've ever seen
Probably one of the biggest projects ongoing on the marine sites in Honduras is the lionfish project. The lionfish is an invasive species in the Caribbean, originating from the Indo-Pacific, and most likely introduced here as a pet that got too big and greedy for a home aquarium. Their numbers have exploded, and they have now been found everywhere from north of Florida to the east coast of Brazil. Even the Mediterranean has been invaded, although how the lionfish got there is likely a whole different story. The Pez de Leon, as it is known in Spanish, is causing havoc wherever it goes with its sharp venomous spines that make it an unappealing snack for most predators. I mean, if you can choose between biting into a fluffy muffin or a cactus, I know which one I’d go for. To add to its fine qualities as an invader, a lionfish is not too picky about its own diet, eating pretty much anything bitesized and unlucky to be around when their stomachs grumble – little brother might want to stay a safe distance away! With no predators specialized in hunting them and by eating anything that comes their way, the lionfish are causing drastic changes in Caribbean reef dynamics.

Capturing lionfish is tricky business,
but not because they are fast. 

The projects here concentrate a lot around lionfish behaviour. There are projects that are undertaken in the lab, where a lionfish is provided a choice between a chemical cue, where another lionfish is put in a blackened bucket with small holes in it below water level, and a visual cue, where a see through, non-holey bucket is a temporary home to another lionfish. The test object is then given 30 minutes to choose whether it would like to hang out with the one it can smell, or the one it can see, and the trials are recorded with a GoPro. Why? Because currently the only method used for trying to reduce the numbers of lionfish is culling. If the lionfish were only hanging out up to 30 meters down from the surface that would be fine, but unfortunately they are known to have massive populations living in as deep as 300 meters. The few that we can see during our snorkels and dives are probably just the rejects and inbetweeners of Lionfish City, bullied out of town to settle in small groups planning a takeover of the world in a Pinky and the Brain style... The chemical cue vs. visual cue experiments are hoping to provide ideas for developing new traps for catching the lionfish, because culling can only do so much, especially as we cannot dive to 300 meters... not with a small budget anyway! Once the venomous spines are removed, the white flesh of lionfish is as tasty as any fish on the market, if not better. We got to try a ceviche made from the lionfish used in the lab and it was mouth-wateringly delicious! I know what you’re thinking, using the fish to contribute to their own demise by making them lab rats and eating them when the job is done – a bit cruel. But they are a delicious pest!

George getting up close and personal
in his hunt for the otoliths.
In vivo research of lionfish consists mainly of recording them in their natural habitat, and trying to find out where and how they prefer to hang out. Most times when I have seen a lionfish while out snorkelling, it has been floating alone behind a ledge of reef, looking serene and still as if meditating, but they are also known to aggregate in groups of two or more. In fact, the last time I saw lionfish we counted 8 individuals under one rock ledge! One aspect of the lionfish ecology research is to figure out if there are any differences in their activity levels depending on whether they are hanging out with their posse, or if they are lone rangers. This can also provide yet more knowledge for development of future traps, and especially their strategic placement on the reefs. If you think about it, there is no point leaving a mouse trap in the middle of the floor, if the mice always travel by the wall...

Gutted. Ugh.
Before the fish are given to the restaurant in the Beach Club, most of them are studied by dissection as well. These dissections determine their “normal” diet, and as part of Team Lionfish has also been to Utila (another site in Honduras), they are attempting to find out any if there are any dietary differences between the populations. Juvenile damselfish in Tela might be in a league of their own in terms of palatability, or just not as available as a food source in Utila. During the dissections otoliths are also removed from the fish. These are small, flat and circular bones in the head of the fish, and they grow in a similar fashion to trees, leaving annual growth rings that allow researchers to age the fish. Together with information about gonads from the same fish, the researchers can determine if the fish mature within the same timeframe in all populations, of if the environment might have an effect on the transition age from a juvenile to a fully grown adult with a need to breed. Of course, all this could also be governed genetically, which is why small clips are taken from the fins of each fish during the dissections for further DNA analysis in the States.

So, all this put together makes one impressive operation in an attempt to learn more about the Evil Invader of the Caribbean, and most importantly how to control it, because the lionfish have no self-control - in a year, one lionfish can produce up to 2,000,000 eggs. That’s one hell of a litter! Currently, it is more like trying to kill a colony of ants using just a pair of tweezers, but fortunately from what I have seen more and more people are picking up their tweezers. And the more people get concerned about the issue, the more resources it will gain, and the more advances will happen. And who knows, maybe in a year or two, instead of hankering for a dirty kebab after an all nighter, we’ll be looking forward to a plate with a nice crispy breaded lionfish and some plantain chips... NOM!

Just casually invading. Nothing to see here.

No comments:

Post a Comment