So this shouldn’t come as any surprise that I am doing yet another lionfish post. By this point you know the story. They are a Pacific reef predator that has been introduced to the Atlantic. They can now be found in great numbers throughout Caribbean and Florida reefs, but can also be found as far up the east coast of the US as Long Island! There are many potential problems of having this novel reef predator on already impacted reefs in the Atlantic, so its a situation people have been monitoring for quite some time. And their ever increasing numbers have led to attempts at eradication.
2011 will be no different. The first of three Florida Keys lionfish derbies was held earlier this week. Considerable cash and other prizes were offered to teams with the highest catch, and both the largest and smallest fish. Over 500 specimens were hunted and killed. That’s the good news. The bad news? It only required 10 teams of between 2-4 people showed up to catch the 531 lionfish. Last year, the same derby had 27 teams catch 534 fish. While one could argue that this year’s teams were more skilled lionfish finders, it is also likely that this is an indication of more lionfish. A catch per unit effort type thing.
Fisheries researchers often use catch per unit effort – CPUE – because sampling effort may vary from one time to another, or from one place to another, and so CPUE standardizes the individuals caught to the effort exerted. Not knowing anything about the actual number of total participants, if we use “teams” as the effort, this year’s CPUE was 53.1, over two and a half times more than last year’s CPUE of 19.8. So what does that mean? Now I am not a fisheries biologist by any means, and so I might be giving a totally oversimplified explanation, or I might be wrong altogether (and hope someone corrects me), but while CPUE is not a direct measure of fish population abundance, it is an oft-used proxy. The increase in CPUE this year from last year likely indicates an increase in population.
CPUE is itself problematic because it is typically fisheries-dependent data. Its value as an estimate of abundance varies with the catchability of the particular fish species surveyed and the efficiency of the gear being used. A major assumption of CPUE as a proxy for abundance is that the relationship between catch and abundance is linear, ie, the more fish, the higher the CPUE (you can learn more about estimates of abundance from this UNCW lecture) This is the assumption I am making with the lionfish population in the Florida Keys based on my simple, back of the envelope calculations. Again, there are problems using fisheries CPUE since it is often not proportional to abundance – fishers become more efficient over time and don’t fish randomly. But for the sake of this argument, it is probably safe to say that lionfish populations in the Florida Keys are on the rise. Stay tuned for more after the final 2 derbies.
Check back as I am sure I will make edits when more fisheries minded people read and comment.
EDIT: A follower sent me this video of a new tool being used to capture lionfish which may be more efficient than a typical spear gun. Plus I like the soundtrack.
Edit 2: A new blog has jumped into the fray of lionfish blogging, with this post of a very good video on the subject. The blog is SeaMonster – started by Jon Bruno and Emmett Duffy. It is really good, so you should definitely check it out.
New species get introduced into novel habitats almost like clockwork in the modern era. These are termed introduced or exotic species. Typically, these introductions are the effect of anthropogenic activity. Sometimes, these species become nuisances – spreading in their new habitats via natural processes, and creating problems for native species. These nuisance exotics are called invasive species.
So how do they get here? From a variety of ways, but perhaps most famously via ships’ ballast dumping. Ballast is simply material used by ships to control and maintain buoyancy and stability. Typically this is water, pumped into ballast tanks from the port the ship is sitting in at the time. This ballast water gets pumped in or out depending on the weight of the cargo on this ship, and so you can imagine how water could be transferred across whole oceans, bringing with it any species that happened to get sucked in to the ballast tank. This is a major source of marine invaders – including the now infamous zebra mussel, Dreissena polymorpha, which has become especially problematic throughout fresh waters of the Mississippi River, the Great Lakes, and the east coast. However, invasives can also come from aquaculture gear and species – especially as native species are fished out and replaced with non-natives to keep up food production. In addition to these non-native species used in aquaculture, other species hitch rides on them.
However, as you can see above, it is possible that all invasive species are not created equal – that is, maybe not all invasives are so bad. Green fleece, known as Codium fragile, has been introduced to the east coast of America for decades. Originating from Japan, it has typically viewed as bad – it is a buoyant species which needs hard substrates to attach, including living shellfish. It got the nickname “oyster thief” since it would attach to oyster shells, and whenever a storm or strong current event occurred, the buoyant macroalgae would be swept away, dislodging oysters and taking them away from reefs and culture sites. It is clear why this is considered a problematic species.
And yet, some recent research has shown that maybe Codium isn’t all that bad. Research which I have participated in has demonstrated that Codium may act as a viable alternative habitat for native bay scallops. Why? Bay scallops have evolved a strong association with seagrasses, and the Codium canopy likely provides the same upright structure to scallops. We observe scallops frequently in association with Codium in Long Island bays, and a study conducted showed that survival of free-released and tethered scallops was the same in eelgrass and Codium, suggesting that the invader offers a similar predation refuge. This was published last year in Marine Biology (See Carroll et al, 2010, below).
In addition, I have taken the research further. The aforementioned paper talked about survival on a relatively short time span – 1 week. In order to examine the longer term effects on growth I conducted a caged field experiment the past two summers at 2 field sites with eelgrass, Codium, and unvegetated sediments in close proximity to each other. The general findings have been that scallops in Codium grow at rates similar to scallops in eelgrass, however, there are site-specific differences. There are also no differences in mortality between the habitats – suggesting that dense stands of Codium aren’t having as detrimental impact of low dissolved oxygen as I originally thought. This work isn’t published yet, as I am working on a method to find the stoichiometry of the tissues, but some of the results are in the presentation I gave at CERF 2009 here: Thursday_SCI-045_1115_J.Carroll
However, I am not the only one who sees “positive” impacts of Codium. In the most recent issue of Marine Ecology Progress Series, a team of Canadian researchers, led by Annick Drouin, higher abundance and diversity of the faunal community in eelgrass meadows invaded by Codium fragile. Using a variety of sampling methods and field manipulations, the team demonstrated higher abundance and diversity of invertebrate organisms on Codium, and in eelgrass meadows invaded by Codium, than those without Codium. The pattern of fish abundance and diversity was not different – likely because they are highly mobile and can move easily between structured habitats. It is likely that Codium just generates MORE habitat, as it is branching and canopy forming. The important thing here is the ecological implication – the lack of a negative effect on native species by the presence of this “invader.” Perhaps Codium might not be so bad after all, especially as eelgrass is declining in many regions.
It is possible, then that “invasive” vegetation species in the marine environment may not always be bad. In many cases, invasives may be beneficial. Numerous studies (including the ones above with Codium) have demonstrated a positive effect of invasive algal species on native fauna. Typically, the vegetation is habitat forming, and invades areas where native habitat forming vegetation has already been lost. In essence, it is replacing a lost habitat, and creating a new habitat which is functionally similar to the species which declined/disappeared. That being said, invasive algal species can be detrimental to native macrophytes through competition. However, the benefit is in enhancing native fauna, which has potential fisheries ramifications. This requires further investigation, but it is entirely possible that non-native macroalgal species might have a positive effect on a number of native fauna.
The above photos, and the one of the moon snail farther up the page, are all illustrations of native species of Long Island associating with the invasive Codium fragile. Now, again, there are certainly detrimental effects of invasive species, so I am not trying to be too much of an apologist for them here. However, in the absence of eelgrass, it is entirely likely that the upright, canopy forming structure of Codium creates a habitat suitable to many seagrass associated fauna. As eelgrass is declining, invasive macrophytes might be important replacement habitats for a variety of native species. Understanding how these species affect native species will be key for management of estuaries moving forward. Particularly, once established, invasives becoming increasingly expensive and difficult to remove. If some invaders might be of benefit, that relationship needs to be well understood. Hey, invasives could help bring back the bay scallop in NY (and likely is having an impact), providing a habitat as eelgrass has disappeared from many Long Island areas. Who knows where else they might be beneficial.
There will be those of you out there who disagree. I don’t blame you. Calling an “invader” beneficial certainly goes against conventional wisdom. When we first introduced the idea of Codium as a potential scallop habitat to a shellfish crowd, we were scoffed at. However, the data don’t lie. And more research points to cases where invasives may actually facilitate natives.
Drouin, A., McKindsey, C., & Johnson, L. (2011). Higher abundance and diversity in faunal assemblages with the invasion of Codium fragile ssp. fragile in eelgrass meadows Marine Ecology Progress Series, 424, 105-117 DOI: 10.3354/meps08961 Carroll, J., Peterson, B., Bonal, D., Weinstock, A., Smith, C., & Tettelbach, S. (2009). Comparative survival of bay scallops in eelgrass and the introduced alga, Codium fragile, in a New York estuary Marine Biology, 157 (2), 249-259 DOI: 10.1007/s00227-009-1312-0
So wow. I’m not saying it has anything to do with me, but I made a post about lionfish a few months back, and had a very special guest blog by colleague Amber Stubler about her experience capturing lionfish with a spear gun and eating them. A commenter was concerned about that post, indicating that some research is showing that lionfish may contain ciguatera poisoning, so I had already decided to do a new post about that. But then, in the last 2 days, lionfish are making the news – first in Florida, then in the US Virgin Islands.
In Florida, dive master Randy Jordan of Emerald Dive Charters is the self-proclaimed “lion-tamer.” He has caught 331 lionfish to date, including his most recent haul, a 16 inch (!) 2 and a half pound fish. According to Fishbase, thats about as big as they get. According to the article, Jordan is scheduled to give a lecture on the subject on February 26th at the Loxahatchee River District meeting to talk about his special device to catch these invaders.
Then just yesterday, an article about the invasion problem in the USVI, where the lionfish now number in the thousands. The governing agencies there are planning meetings with divers, fishermen and businessmen to discuss the problem and how to combat it, and, in particular, to get divers and fishermen to report their kills. The worry is that these invasive voracious predators will wreak havoc on the local reefs and hit the major tourism industry.
Lionfish are getting a lot of attention currently. And I have advocated the consumption as an eradication plan. But as I mentioned, commenter John Rubattino from the USVI had commented his concerns about ciguatera poisoning being prevalent in fish caught there. This would create a major problem, as ciguatera is a food poison, and when humans consume fish that contain the toxin, they often experience nausea, vomiting, diarrhea, pain, dizziness, vertigo, chills, rashes, and other symptoms.
So how does one get ciguatera poisoning? Again, its a food poisoning which results from eating large predatory tropical fish which contain the poison. According to the CDC, these fish include barracuda, certain snappers and groupers, jacks, king mackerel and hogfish. But where does the toxin come from, since these fish don’t produce it themselves? Tiny microalgae. In particular, this toxin is produced by a harmful dinoflagellate known as Gambierdiscus toxicus. When it grows, it often settles on reef structure and macroalgae where it is consumed by herbivores and small predators. Then these fish are consumed, and so on and so forth up the food chain. But the toxin is not harmful to the fish. So the large predators listed above contuinue to accumulate (a process known as bioaccumulation, also here, one of the reasons why you shouldn’t eat too much tuna or many other fish due to mercury) the toxin. Then, when humans eat those fish, they get extremely ill.
So I did some research on the itnerwebs about lionfish and ciguatera. Lionfish already produce their own toxin, present in their spines, but the thought was as long as they were processed carefully, that would not be harmful to humans. Surprisingly, there is little information about lionfish and ciguatera. There are a few posts from the Caribbean Oceanic Restoration and Education (CORE) Foundation in the USVI about lionfish with ciguatera, and how to proceed. Attached 5. Ciguatera is a .pdf from the Caribbean Epidemiology Centre about ciguatera cases in the Caribbean.
So its now out there and at least something to think about. There haven’t been many reported cases, but it might be worthy of investigation in the future. Obviously, lionfish present a considerable risk to the coral ecosystems they are invading, and so eradication must be considered. A simple way is to encourage locals to fish and eat them, and hopefully fish them out. However, if they might present a risk to human consumption, this idea needs to change. Research is warranted to resolve these issues.
A few months ago I made a post about lionfish being fished an eaten as a way to eradicate these invasives from the Caribbean. One of the places where this was being done is Jamaica, and if you remember correctly, last week I posted about a tropical course that undergrads from Stony Brook get to take in the laid back paradise. My labmate, Amber Stubler, is there as well, working on her dissertation research, but also hunting and eating lionfish. So I thought she should tell us about it (also, all the pictures are Amber’s):
After much groveling, John finally convinced me to write a “celebrity” blog about my trip to Jamaica. Rather than bore you all with the details of my sponge research (which you can read about here, here and here), I decided to write about another issue going on throughout the Caribbean- the invasion of lionfish, and what the Jamaicans are doing about it. For those who did not know- Lionfish (Pterois volitans) are native to the Pacific and likely arrived in the Caribbean via the aquarium trade (however ballast water transmission cannot be ruled out). The earliest sightings of lionfish in the wild (confirmed by USGS) were in southern Florida in 1992, and since then lionfish have been reported from Long Island to Venezuela. The USGS website has a really awesome animated map of the invasion here, which goes from 1992-2010.
I have been coming to Jamaica on a regular basis since 2007, and saw my first lionfish in 2009. I specifically remember taking about a thousand pictures of it, because even the marine scientist in me cannot resist a pretty fish picture. Since then, their populations have exploded, and when I say exploded, I mean I saw one in 2009, and on this trip I could easily count between 15-35 fish in an area the size of a football field underwater. So at this point you should be saying, “Amber, what’s the big deal with these lionfish, after all they are pretty and quite frankly the Caribbean could use a few more fish.” The problem is that they are voracious predators who will eat small invertebrates, juvenile fish, and anything else that will fit in their greedy mouths. This poses a threat to all the indigenous reef species as the lionfish eat all of the native species’ food, or just plain eat all of the native species. Also these guys pack powerful venom in the spines on their fins, which will ruin anyone’s dive/snorkel adventure. And since these guys are invasive, they have few natural predators which means they are free to roam about the Caribbean.
This, my friends, is where we come in.
We’ve all learned a valuable lesson that the best way to get rid of a fish species is to eat them (examples: cod, Atlantic salmon, etc). So what’s a country like Jamaica to do? Eat ‘em to beat ‘em (which by the way is the Bahamas official lionfish slogan). The Jamaican Ministry of Agriculture and Fisheries has begun an annual lionfish derby where prizes are awarded for the most lionfish caught over a 3-day period. They also hold seminars on how to safely catch, clean, and cook lionfish. Here at the Discovery Bay Marine Lab, staff members regularly go on lionfish hunts, bringing back dinner for their families and samples for Dr. Dayne Buddo, who studies invasive species at the Centre for Marine Sciences, University of West Indies. Dr. Buddo has spearheaded (no pun intended) many public outreach events teaching locals about the biology of the lionfish, the impacts on the ecosystem, and how to treat a lionfish sting. He also shares some of his favorite recipes, and cooks the fish up for skeptical Jamaicans.
After seeing Dayne spear several lionfish during one of our “fun” dives (ie not for research purposes), I decided it was time to take part in the action. So I broke out my shiny new speargun (specifically bought for this trip), and started wreaking havoc on the lionfish at my study sites. Over a course of our 2-week trip we managed to kill about 36 lionfish, and although that doesn’t really sound like a lot, we actually only brought the speargun out about 6 times, which means that our average was about 6 fish per dive. The largest we caught was 13 inches, and roughly 1 lb, certainly not a record, but a lionfish of that size can produce 30,000 eggs at a time, so I like to think that our killing spree helped save the reef from a few future lionfish. The great part about this whole kill-every-lionfish-you-can ideal is that it is uniting the fishermen against one species and will hopefully help eliminate/decrease the lionfish population here in Jamaica. Jamaica is already one of the most overfished reefs that I have ever seen, so having the fishermen focus on an invasive species gives the native fish a break from fishing pressure and keeps food in people’s mouths.
You can do your part too! Check out this awesome cookbook to become a full-fledged invasivore, and donate to a great non-profit organization dedicated to marine conservation.
Some call them sea squirts. Some call them tunicates. To some it looks like pancake batter. Didemnum vexillum is a potentially harmful invader along the coast of New England, specifically in George’s Bank. Since it was first discovered in 2002, it has spread rapidly. As a colonial organism, it expands rapidly, forming vast mats of intertwined individuals. It needs a hard substrate to colonize, and the cobble bottoms off New England and south to Long Island Sound are ideal substrates. In fact, in Long Island bays, we often find Didemnum on cinder blocks and concrete pilings. This invader likely came here via important Asian shellfish, but the exact time and point of introduction are not known. Regardless, this species has received numerous bad press, mostly due to the fact that its preferred substrate is also valued habitat for commercially important sea scallops and groundfish such as cod and haddock. However, research from Woods Hole lab of NOAA’s Northeast Fisheries Science Center has started to investigate potential positive qualities of this invader, as some species are enhanced by the squirts presence. Some species of marine worms and Cancer crabs appear to thrive among Didemnum colonies. This could have food web implications. Marine worms are favorite food source of winter flounder, whose stocks are suffering. The crabs that thrive among the invader are also important food sources to higher trophic level organisms. In addition, if the crabs are consuming the sea squirt (which is total conjecture on my part, as the article doesn’t say anything about this), than that high amount of production from the squirts can then get transferred up the food chain. Granted, the invader isn’t good news, and that few species appear to like this new habitat does not in any way mean that this invader is not harmful. But it does support a research hypothesis that I am working with in local bay waters. Marine systems are incredibly resilient. There has been no instance of extinction of a native species due to the introduction of a new species in a marine system. There might be negative consequences, and in the case of Didemnum, the consequences are many. That being said, this research indicates that native species are able to adapt to invasive species. This has certainly been the case of Codium fragile, and invasive macroalgae, and scallops in Long Island waters. In my research, and my readings, it appears as though those “invaders” which are potentially habitat forming are much more likely to have some positive interactions with native species. There is still a lot to learn about Didemnum vexillum and its overall ecosystem impacts (some research underway at SoMAS has identified the ability of Didemnum to filter extremely small particles out of the water column, as well as investigated how colonies of Dideumnum might affect water column filtration in small coastal waters). And however unpopular, it is important that valid research results are always reported, even if they go against the common theme of invaders being strictly negative. All the information needs to be out there to paint the clearest picture possible. While it is unlikely that this new research will change many opinions, and while Didemnum is still harmful to some species, it is possible that the George’s Bank marine ecosystem is responding to the invader, adapting to the change, and will continue to support fisheries despite its presence. Who knows?