Scientists are perplexed with the variation they’ve been seeing.  They say that it has come on too fast to be anything involving melting ice sheets.  The popular opinion right now is that it is mainly caused by a combination of Northeast winds over the ocean and a reduction in the ocean current running from Florida up the coast (not the Gulf Stream, but a prevailing near-shore current mainly caused by Southwest trade-winds).  The winds haven’t been particularly strong, just persistent.  

So, what is causing the winds?  Bill Chameides posted on the Duke University site that it could be a result of a phenomenon known as the North Atlantic Oscillation (NAO).  The NAO is a smaller cousin of the ENSO (El Nino/Southern Oscillation).  Essentially, its a periodic shift in wind patterns that can cause a sloshing back and forth of the entire ocean.

One hole in this theory is that the NAO has not been particularly intense.  Another theory (similar in affect, really) is that rising sea levels are causing changes in global atmospheric circulation.  According to this theory, the sea levels will not rise uniformly around the entire world, but will in effect slosh back and forth as they rise.

Many questions still remain such as how long will it last?  Is this a very temporary anomaly, is it the beginning a longer trend, or is this just a taste of things to come when the sea levels rise?  One thing for sure is that we don’t need a storm surge from a hurricane coming ashore during a freak high tide (or anytime, really).  As for how it will affect our commercial fishing seasons, no one knows.  There are different portions of the marsh being exposed to tide and current as well as some portions that are spending more time under water.  This is sure to effect our oyster seasons, but good or bad?  Who knows?

For more information, check out NOAA’s news, alerts, and up to the minute tidal information here.  You can also read more about it here and here.

Right now, roe shrimp are being caught (the females with eggs), so I guess we should start there.  Shrimp lay their eggs (500,000 – 1,000,00 per female) in the ocean up to a few miles offshore, but mostly near the beach.  Within a day the egg (1/64 of an inch) will hatch and the new larval shrimp will feed on the yolk reserves.  The shrimp is about the size of a plankton at this point and will stay in this form through four more stages. 

First, the shrimp will develop a mouth and an abdomen so it can begin feeding on algae.  This is the protozoan stage, and the shrimp will grow to about 1/12 of an inch in this stage.  Then, there are three mysid stages where it will begin to develop legs and antennae and grow to about a fifth of an inch.

After that, there are two post larval stages where the shrimp will assume the overall appearance of an adult shrimp and grow to about a quarter of an inch.  So far, this process has taken about two weeks, and the shrimp has moved from the ocean back into the creeks where they will continue growing.  Adult shrimp grow very rapidly, and will molt about a dozen times in their life.  This is closely related to the lunar cycle as they do it on the new moon, so they can be more hidden from predators. After shrimp are fully grown, they will move back out to the open waters, which is when we have our fall run of white shrimp.

An adult shrimp’s body is divided into three segments, the head, the thorax, and the abdomen.  The head and thorax are fused together and covered by a carapace which also encloses the gills.  Shrimp heads have eyes on stalks and the long antenna.  There are fourteen pairs of appendages.  The three pairs closest to the head are modified mouth parts, the next five pairs are walking legs, then there are five pairs of swimming legs, and finally one pair that form the tail.  Shrimp are considered decapods (like crabs and lobsters) because they have ten pairs of legs that are used for walking and swimming.

My favorite part of the shrimp, though, is the muscular body, which I find to be a good vessel for cocktail sauce.

source: http://www.scwildlife.com/pubs/septoct2008/shrimp.html

The uses of chitosan don’t stop there though.  It is also a fantastic natural fertilizer, defends against fungal infections, and is used to help purify liquids like water and, my favorite, beer.  It has even recently been developed into a polyurethane coating that actually heals itself.  Cars that heal their own scratches?  Shrimp rule.

So, what do shrimp use chitosan for, you may ask.  Well, chitosan plays an important role in their life cycle as well.  After shrimp molt (which happens on a regular basis), the chitosan forms a framework for the fusion of calcium carbonate, which is the main ingredient in the exoskeleton.  Calcium Carbonate, by the way, is present in any seawater.

Now, how much will this help you next time you’re done with a fresh, local shrimp dinner?  Probably not so much unless you are a chemist, but you can always put them around your plants to help fertilize and prevent a fungal infection.  Please, do not use shrimp shells instead of band-aids.

Fresh SC Shrimp

In preparation for the opening of shrimp season I am going to drop some science on y’all in a three part series, starting with the most common shrimp question, “what kind of shrimp are there in South Carolina”.

Of the 2000 species of shrimp that exist in the world, the South Carolina lowcountry can lay claim to three of them, white shrimp, brown shrimp, and pink shrimp.  White Shrimp (Litopeneaus setiferus) are the most sought after by commercial fishermen and restaurants alike for their size and flavor.  They spawn in the spring (now), and are what the shrimpers will catch first (May, early June) and last (Oct. – Dec.) in the shrimping season.  Brown Shrimp (Farfantepanaeus aztecus) spawn in the fall and are what the shrimpers will be catching during the summer months.  Although smaller in size, the brown shrimp have a great flavor and are commonly used in shrimp dips, popcorn shrimp, shrimp salad, and my favorite, pickled shrimp.  Pink Shrimp (Farfantepanaeus duorarum) are the least common on the SC coast and also spawn in the spring.

Knowing which shrimp are being caught during the season can help you determine if a restaurant is really serving fresh shrimp, or lying to you (common practice, unfortunately).  White shrimp are easily identified by the green color at the end of their tail (before cooking).  If it is July, and the restaurant is claiming fresh, local shrimp, ask to see an uncooked shrimp.  If there is green on the tail, its highly doubtful that its fresh, although it may be local and frozen.  In which case, ask to see the package it came in.  It will tell you where it was caught.  If it says Thailand, I at least, will get up and walk out.  The main way the general public can help our commercial fishermen is to be educated and DEMAND to only be served local seafood.

I wish I had thought of this.  I really do.  But, the honor actually belongs to Dr. Louis E. Burnett of College of Charleston’s Grice Marine Laboratory.  Dr. Burnett is studying the bacteria Vibrio campbellii which attacks blue crabs, oysters, and shrimp.  He became interested in the way this bacteria affects the performance of the organisms in the field. 

Dr. Burnett and his team came up with this treadmill as a way to simulate the activities of shrimp in the real world.  The treadmill is contained within a respirometer so that the scientists can measure oxygen uptake.  The treadmill is also used to study blue crabs in the same way.  You can check out the College of Charleston site here.

Now, enter YouTube.  The video became an internet success and has been put to every song imaginable.  It has landed Dr. Burnett on MSNBC and countless radio shows.  Although it is in fact humorous, I would like to thank Dr. Burnett and his team for the work they’re doing and let him know that the commercial fishermen in the Charleston area appreciate his efforts.

Unfortunately, this is a question we may be experiencing in the next few days.  I just saw in the local news that the low temperature for Friday night is supposed to be 15 degrees!  In Charleston, SC!  The wind is going to be out of the North at 15-20 which will put the wind chill around 10.  Friday is forecast to have 16 hours below freezing.  Tomorrow and Saturday don’t look much better, either.  Luckily for us, the low tides are going to be first thing in the morning, right in the coldest part of the day. 

So, back to the question, “what temperature does saltwater freeze?”.  Well, it actually depends on the salinity of the water.  The more salty, the colder it has to be.  Generally speaking, though, the water in this part of the Atlantic freezes at 28 degrees F (or -2 degrees C).  This only becomes an issue for us oystering in South Carolina once or twice a year, if at all.  With wind chills at 10 when the tide goes out and the oysters become exposed, the water around them will freeze.  This essentially freezes the oysters into the mud.  Imagine trying to pick rocks with razor blades attached to them out of frozen mud.  Sounds like fun, right?

This can have a definite impact on shrimping as well.  Right now the water temperature in the Charleston Harbor is 53 degrees.  With a North wind and temperatures well into the teens and twentys for the next few days, the water temp will drop quickly.  If it gets to 45 degrees, it will kill the shrimp in our waters.  This will not only affect the catch right now, but next season as well as the smaller white shrimp in the creeks (that will be big white shrimp in the ocean by spring) will be killed.

Jeff and I will be out the next few days, and if my fingers warm up enough to type, I’ll give a report.  Oh yeah, and Zack (in Hawaii), Setzer (in Costa), and any other friends in the tropics- you’ll get yours.

It is still generally accepted that a bushel is a unit of measurement for dry volume, or stuff other than liquids mainly in agriculture (like oysters).  As such, it can be further broken down into 4 pecks or 8 gallons.  The trouble comes when we refer to a bushel on the commodity markets where it is used as a unit of weight.  And bushels of different commodities weigh different amounts.  For example, a bushel of oats in the USA is 32 pounds (Canada is 34 pounds), but a bushel of barley is 48 pounds.  Malted barley is 31 pounds.  And so on and so forth.

With the oyster industry both weight and volume are used.  Some oystermen refer to a bushel as a unit of weight, usually anywhere between 45 and 60 pounds.  We measure our bushels the old way, as a unit of volume.  We fill up a wire bushel basket and then round off the top to account for any voids left by the oysters.  The weight is usually right around 50 pounds, give or take.  The problem with doing oysters by weight is that the majority of the weight of an oyster is in the shell, so if you have oysters with thick shells, you may end up with a much smaller bushel by weight.

So, back to the question, how many oysters are in a bushel?  Basically, I don’t know; I’ve never counted.  It depends on how big the oysters are and what kind of bushel you’re talking about.  The more important question is probably “how many people will a bushel of oysters feed?“.

…with the first day of winter we’re also getting ready to say goodbye to the warm temperatures we’ve been having.  Its going to be back down below freezing for the next couple of nights after a cold front passes.  Hopefully we haven’t seen the last of the 70’s in December, though.

DNR Planting Oyster Shell

We are lucky in South Carolina that our shellfish harvest has remained stable for the last 30 years.  This is in part to the efforts of DNR’s oyster shell recycling program.  As demand for bushels of oysters for backyard oyster roasts goes up, it is important now more than ever to create new habitats for oysters to grow.  One way that everyone who eats oysters can help with this is by recycling your shells after your oyster roast.  You recycle your cans and bottles, right? 

When oysters spawn in the late spring and early summer months, they release free-swimming larvae that is locally known as “spat”.  The spat spend the first two weeks of their lives adrift and at the whims of the tide and current.  After that, they look for a suitable place to attach to and begin building their calcium carbonate shell.  Unless they are disturbed, they will remain where they have attached for the rest of their lives.  Their shell will then in turn provide a landing spot for more spat.

The most desirable material for spat to attach is other oyster shells.  There has been success with other materials as well, such as wooden stakes, hog wire, and concrete, but shell is by far the best (and most natural).  What we do on our lease is look for areas where there are no oyster beds next to areas where the oysters grow well.  We will plant the shells on a mud flat and let it sit until the spat are out.  They will attach to the shell and repeat their life cycle until a few years have gone by, and we have a new spot to harvest oysters.

DNR does essentially the same thing, but on a much larger scale.  They collect and plant tens of thousands of bushels of shell every year.  Click here for more information and to find the recycling location nearest to you.

This week, though, the tides actually move backward in time for one cycle, and then forward for the next.  For example, yesterday afternoon low tide was at 4:17pm, but low tide this morning was at 4:07am, when it should have been around 4:45.  I guess its not that big of a deal, and it does straighten out by the weekend, but the tides are one of those things you usually consider dependable.  They go in and out, and they wait for no man.

I spoke with a few captains around the docks, and no one had a good explanation.  The only thing I can come up with is the fact that Venus, Jupiter, and the moon are pretty close to being in alignment in the night sky right now.  Kind of like the deal with spring and neap tides, they must have some sort of gravitational effect on the earth.  The nuts and bolts of the matter is that we don’t have a low tide during daylight hours for the next few days.