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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.

No (shark fin) Soup for You!

Well, more bipartisan cooperation this week, which after almost 2 full years of bickering is a bit refreshing.  Especially when it comes to a fisheries related issue – shark finning.  Yesterday, the bill went through the Senate, and this morning, passed through the House.  Now all Big-O has to do is sign the thing into law.  Although some measures of protecting sharks have been in place for some time, shark finning was popular since the fins fetch considerably more dollars than other shark meat.  This practice involves catching sharks, cutting off their fins and throwing the finless fish back overboard.  I guess this is in an attempt to maximize landings of valuable meat, as I assume catch quotas are on a poundage basis.  Now, all sharks landed have to be kept whole.  Additionally, other vessels cannot transport fins.  Not knowing much about the shark fin trade, my guess is that most shark people will see this as good news.  Of course, there is always exceptions, and a smooth dogfish fishery will be allowed to continue finning practices, but such is the cost of compromise in getting enough support for the bill to pass.  Hopefully this is all a step in the right direction.  WhySharksMatter over at Southern Fried Science blogged about it today, so check it out.  Also, to learn more about shark finning, check out this post from Ya Like Dags from last month.

As a side note, Dr. Demian Chapman over at The Institute for Ocean Conservation Science uses genetic tools to identify shark fins in order to see if illegal species are being traded.  Pretty interesting stuff, which was recently highlighted in Popular Science.  A blogged about a lecture of his which I attended back in October, and also wrote this piece for the school website (albeit with some serious edits by my supervisor).

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