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The Decline of Seagrass Meadows

Zostera! Eelgrass, Zostera marina, is a flowering, marine vascular plant that remains submerged all the time. This is quite a feat for vascular flowering plants, and only a few dozen species world wide are capable of growing completely submerged in a marine environment. Eelgrass creates and extremely important habitat, its upright structures and complex root system create a 3-D living space for many different types of animals. It is (or was) the dominant habitat forming SAV (submerged aquatic vegetation) throughout much of the coastal waters in the northeastern United States. Unfortunately, for various reasons, eelgrass meadows have seen drastic declines, and in many locations eelgrass only exists in a mosaic of small patches. This is extremely bad news as many of the important, and formerly important, commercial and recreational fisheries of the northeast US are dependent on Zostera at some part of their life cycle as a nursery and foraging ground. Some of the species are finfish like tautog, bluefish, fluke, winter flounder, porgies, while others are shellfish such as blue mussels, hard clams, oysters, bay scallops, and blue crabs. Many of the aforementioned species support or once supported vibrant fisheries. Many of those fisheries have collapsed, also for various reasons. However, is it possible there is a link between the crash of the fisheries, the decline of Zostera and the failure for recovery on both ends?

Bay Scallop on Eelgrass

Argopecten on Zostera! Bay Scallops, Argopecten irradians , have developed a very close relationship with eelgrass, Zostera marina. As larvae, they are passively transported, and tend to settle in eelgrass meadows when the current is dampened by the 3D structure of the seagrass. This same 3D structure provides post-set juvenile scallops a spatial refuge from predation. Even as larger juveniles and adults, scallops are capable of, and have been shown to, actively select eelgrass habitats.

Other species also use eelgrass

grass shrimp A number of other species utilize eelgrass as a habitat. Included are grass shrimp, like the Palaemonetes pugio, other decapods such as blue crabs, bivalves such as hard clams, gastropods (snails), and numerous fish species, including winter flounder, tautog and cod.

More Lionfish, Oh My!

Lionfish from my Fiji dive trip. It was upside down under a coral ledge

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.

From American Museum of Natural History

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.

4 comments to More Lionfish, Oh My!

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