Thursday, October 30, 2014

Blue Crab Fishery Declined Throughout US East Coast in 2013

NOAA recently released its report summarizing commercial fisheries in 2013. The commercial harvest of blue crabs declined in every US East Coast state with substantial harvests. The total US harvest of hard blue crabs decreased about 25% from 2012, although the value actually increased 3%. The full report can be found here. Gulf Coast graphs will follow in a separate post soon. Blue crabs fell to the 15th largest catch of a species by weight and the 9th greatest dollar value.

Thursday, October 9, 2014

2014 Connecticut Blue Crab Report #4

From Tim Visel at The Search for Megalops:

ISSP and Capstone Project
The Sound School Regional Vocational Aquaculture Center
The Search for Megalops - Program Report #4
October 7, 2014
You Do Not Need to Be a Scientist to Report

·        Blue Crabs Set Off Faulkner’s Island

·        Sound School Reports – Charles Neal, Ceondice Johnson, Steve Joseph and Sean Bishop

·        Black Mayonnaise May Indicate Habitat Failure for Blue Crabs

·        Black Mayonnaise Can Lead to Sapropel

  • Conowingo Dam Study and Blue Crabs

Megalops Blue Crab Setting Off Faulkner’s Island Mid-September

For the third year in a row our blue crab Megalops set appeared mid-September, very late compared to 2010 and 2011 crab years and most likely too late to add to our dwindling blue crab population. Between September 12th to 18th, fishers reported black sea bass consuming large numbers of blue crabs about the middle of September almost to the same weeks as last year (Megalops #10, October 2, 2013) (Megalops Special #6, October 24, 2013) and reflect cooler spring temperatures.

Several requests have come in from southern blue crabbers wanting a blue crab habitat assessment from Hurricane Agnes (1972) to present. Storms such as Agnes or now Lee, Irene and Sandy for Long Island Sound are major habitat events especially when indexed for temperature. I will try to look at this over the winter; general trends do appear: a series of cold winters, low catches, gradual warming (but not hot), better catches. I don’t think many blue crabbers will be surprised here. Many habitat assessments, however, do not include soil pore size, grain size, pH and oxygen redox depths. I also look at habitat types and predator/prey relationships. I just don’t know enough about Chesapeake Bay, so I hope a delay is not disappointing.

 I will also delay some assessments for New England until the NOAA models for the North Atlantic Oscillation (NAO) are finished. The NAO has again turned negative, a sign of an early “polar vortex” (a horseshoe shaped storm pattern) and a cold, snow filled winter for us here in New England.  I use the NAO for one of the long-term habitat quality indicators.

New England blue crab populations are hanging on, it’s to early to declare a habitat failure but remaining populations should be considered “residual legacy” as size is frequently an indicator as well as three cold winters in a row. Historically three cold winters in succession were reflected in sharply lower landings. The truth of the matter is deep water sets late in the fall don’t make it and we are fishing on the past year’s survivors. Compare the three-year classes in the July 11th, Megalops #8 2011 report to current reports and the difference is very apparent.

Cooler Waters On October 5th Essex town dock the bottom temperature at a morning still high tide was 62 F at Indian River, Clinton 60 F. Look for crabs to be active in the deep saline holes (traps better than handlines) as they prepare to burrow in for the winter ahead.

Thanks for the emails and comments. All such observations and reports are helpful as we follow blue crab population trend. I do appreciate all the information entering year four of the Megalops habitat study.

Tim Visel
The Sound School

Megalops Blue Crab Set Observed Off Faulkner’s Island

Thanks to Charles Neal of our Sound School for giving me this report of September 12, 2014:

Charles Neal
September 12, 2014

7:30 AM – Friday – I went fishing with my cousins. We went out for a day of porgy and Black Sea bass fishing by Faulkner’s Island in Guilford, Connecticut. We had a good day, but noticed we were catching more sea bass than porgies. After venturing home to prepare fish for a meal, when cleaning the sea bass, I noticed the stomachs had small blue crabs in their bellies. I cleaned four of them and they all had small crabs they had consumed in their stomachs. We were in 70 feet of water and it was about 10:00 AM when we caught the fish. The fish weighed about 3 to 4 pounds each. The blue crabs we found in their stomachs were about an inch point to point about the size of a nickel.

Also fishers reported black sea bass full of blue crabs on September 14 at Long Island Shoal off of Old Saybrook. Steve Joseph, also of Sound School, reporting large black sea bass feeding on mud crabs at the Branford Beacon the same week. Examining gut cavities you can tell much about “what’s around” and this is one way of finding a post Megalops or star set (Special Report #4, April 25, 2014).

Crabs Return to Shore Areas in New Haven – Ceondice Johnson

Ceondice Johnson
Sound School Senior                                                                                      8/18/14

On my nineteenth survey I used one trap, the wing trap, bated with raw chicken. The sky was partly cloudy. I was out for about an hour and caught one large male green crab that was very active and very aggressive. It was about five inches wide.  With the temperatures very warm (75°F), it seems as though the crabs moved from the shallows (no small crabs).


On my latest survey, I used a hoop trap bated with chicken. As the water has gotten less warm, less green crabs have been seen. There has been an increase in snappers and big blue fish. Also not many spider crabs, but they are larger than before. One small blue crab was observed. I haven’t seen a difference in using menhaden and chicken as bait. I also noticed a male fiddler had been picking at the bait also. The first day back at school I noticed many large blue crabs were back along our docks.

Sean Bishop
Sound School
Milford Beach – September 28th, 2014
Cazwall Cove

Sunday afternoon I found a blue crab shell on Anchor Beach in Milford by Holley Avenue. The crab shell was about 6 inches wide (point to point). I found blue crab shells on the beach before but these are the first large ones I have found. The day I saw them they were on the tideline. I check the tideline for sea glass and corals. I have seen live blue crabs swimming around during high tide and in the cervices between the rocks. I suspect blue crabs were still in this area on September 29th.

Black Mayonnaise May Indicate Habitat Failure for Blue Crabs

More and more attention it appears to be gathering around the country as it relates to terrestrial organics and possible roles in habitat failures. High heat can be just as habitat damaging as very cold. It is ironic that energy (storm strength) and duration has huge implications for habitat quality in each temperature range. One of the areas now receiving attention is the accumulation of black mayonnaise in southern areas. Florida recently commissioned several studies regarding the Indian River lagoon, similar organic deposits have been noted on Cape Cod, Boston Harbor and in the Saugatuck River in Connecticut. More recent news about the Saugatuck River conditions seems to have improved. New York Harbor has been looking at black mayonnaise deposits for over a decade.  Western states are looking at it as well. Sapropel formation found on page 22 of CAP Arizona project contains this section.

Arizona is finding that organics behind reservoirs here already formed Sapropel and accumulating waxes ruining irrigation drip equipment:

“The oxygen deficit conditions at the lower depths may cause sediment nutrient release through the process of reduction. If the sediment/water interface is exposed to prolonged periods of anoxia, reducing conditions allow the formation of nutrients previously unavailable for organisms that cause taste and odor changes in the water. This reduction may lead to Sapropel formation, a compound that is high in hydrogen sulfide and methane, and has a shiny black color due to the presence of ferrous sulfide. This compound is responsible for the occasional “rotten-egg” odor associated with releases from the hypolimnion layer through the lower portal on the intake towers.

Nutrients, such as nitrogen and phosphorous, become unbound from their ionic association with metals, such as iron, and manganese. This process may free up nutrients, which contribute to algae blooms in the canal system. Precipitates of iron and manganese cause discolored water and treatment problems” (P.22, 2011 Annual Water Quality Report, Prepared by the Water Control Department contributing efforts by Arizona State University, July 2012, Central Arizona Project).

With studies on Long Island (duck farm organic residues) New York, Florida’s Indian River and Cape Cod’s Buttermilk Bay, we are finding more and more about the black mayonnaise – Sapropel relationship. As we learn more about it and its ability to seal circulation within it (waxes), many habitat pieces that have so long perplexed biologists are now falling into place. Black mayonnaise is the building material of Sapropel when deprived of oxygen. With oxygen it is a benefit to some; with thin deposits nourishes eelgrass patches and good flows, it helps the blue crab Megalops but take away the oxygen and those same eelgrass meadows now become sulfur-killing fields, except near ground waters upwelling on shore fronts

It explains why in the early 1980s sections of Buttermilk Bay on Cape Cod and Eel Pond heavily loaded with black mayonnaise still had surviving populations of Mya, the soft shell clam along tidal edges (shellfish surveys conducted by the Bourne/Sandwich Shellfishers Association). At low tide a reverse hydraulic pressure would release tidal ground water and keep soil pores open to exchanges of oxygen (if this sounds like a sand/bead backwash cycle on a filter system, it is, only a natural one).

Organic patches were backwashed out keeping this “thin band of life” between mid-tide and the low tide line. Below the low tide, the soft shell clams were dead. But just a few feet above they were doing fine. Soft shells are a favorite food for blue crab Megalops. So a light sandy organic matter soil mixed with shell fragments with soft shell clams and eelgrass is prime blue crab star (past Megalops) habitat. Take away the oxygen and crabs move out, and if sulfides increase fast enough, kills crabs through contact (during test pits on the beach detected upflowing ground water; it is cool even on hot summer days).

It is the sulfide layer in winter that kills crabs in place. Cold water allows deep sulfide layers to leach out. Sulfide levels tend to rise to the top of black mayonnaise under ice and crabs now in a hibernated state cannot escapes as they can in the summer. “Sulfide jubilees” here the sulfide kills the minute the Megalops touch the bottom, hundreds of thousands of crabs at a time (Green pond EEL pond observations, Cape Cod, 1982) and the crabs have no defense. It gives the appearance of “winter kill” but freezing did not do it. On the contrary, crabs benefit from the heat in these composts and temperatures directly in them (not exposed tidal flats) rarely drop below 35 F. Even on winter days the black color of these deposits absorb heat as a solar bank to be released at night.

Charles Beebe of Madison illustrated the power of the winter sun to me in 1978. Our 16-foot Brockway skiff was locked in ice in Clinton Harbor and chopping it out each day, well it was taking its toll. After about a week of heavy complaints, he arrived in his green pickup truck with half a bag of rock salt and orders for Ray (my brother) and I to get a bag of charcoal briquettes, a tall order in February. We found some and placed the bag down on the ground. Mr. Beebe proceeded to jump on it. Soon we were circling the skiff in a mixture of ground up charcoal and rock salt. Within minutes (it was noon) crackling and popping happened. The ice sagged and then broke; the skiff was free. He left muttering something like “I need to teach you both everything.”

In 1988, George McNeil of Clinton gave a similar account of saving the oyster boats at City Point, New Haven, Connecticut (then Oyster Point). In 1931, several oyster boats were locked in deep ice, only this time it was coal dust at the end of South Water Street from a coal business, mixed with rock salt. The heat plus the salt did the trick; he chuckled when he heard of Mr. Beebe’s charcoal briquettes – same idea. The point is, black mayonnaise can absorb tremendous amounts of heat, and if deep enough, kick start the Sapropel process. Eelgrass at the end helps in developing these killing fields (sorry to all the eelgrass reports, but the eelgrass habitat history is very mixed as much good as bad in our area).

This is a quote from an article last February investigating mysterious die-off of eelgrass from the University of Copenhagen (Jens Borum) and Marianne Holmer from the University of Southern Denmark:

“The biologists explain that ‘eelgrass plants trap the mud’ that is washed away from chalky seabeds, and they also trap the poisonous sulfides. The high concentration of sulfides that is trapped in the midst of the older eelgrass that is less capable of withstanding the effects of the poison gets killed off, leaving only eelgrass that encircles the deposits of sulfide-rich mud. They state that the fairy circles of eelgrass (death) caused by the build up of sulfides is also found elsewhere in the world’s oceans.”

At the turn of the century, during intense heat, David Belding, a renowned shellfish biologist then, gave an account of the impact of organic matter upon marine soils and his 1910 report is just as valid today. He found many other biologists during this period the habitat change aspects of sulfide:

 “Organic Material: Clams are usually absent from soils containing an abundance of organic material. Even if the slimy surface does not prevent the set, the clams that take lodgment soon perish. Organic acids corrode their shells and interfere with the shell-forming function of the mantle. Such a soil indicates a lack of water circulation within the soil itself as indicated by the foul odor of the lower layers of soil, the presence of hydrogen sulfide, decaying matter, dead eelgrass, shells and worm. If such a soil could be opened up by deep ploughing, or resurfaced with fresh soil to sufficient depth, it would probably favor the growth of the clam. 

 Soils in which organic acid caused by vegetable decay, are present prove unsatisfactory for the catching of seed and interfere to a slight extent with growth by destroying the shell, often giving to the clam a black appearance which makes it less suitable for marketing.” (A Report Upon the Soft-shell Clam Fishery of Massachusetts Including the Life History, Growth and Cultivation of the Soft-shell Clam (Mya arenaria), David Belding, MD Biologist, 1910)

Several crabbers have noticed bubbles coming off leaf deposits (mostly methane) (Megalops #7, August 16, 2013) and deep leaf accumulations as poor crab habitat. In high heat the gas becomes hydrogen sulfide; the rotten egg odor of coastal areas when it is hot. That is why most large fish kills are preceded by accounts of smells of sulfur and mostly occur during hot and low energy periods. When oxygen is low, the toxic sulfur cycle resumes and the first toxic impacts are to the benthic bottom dwellers and dead crabs. John Hammond, a retired oyster grower on Cape Cod, used to say this stuff is bad for the fish and fishers; it is. When sulfur levels get high, blue crabs may walk out of the water, most benthic organisms can’t do that. Down south in the historical literature, they were called “jubilees.”

But even here they happen in extreme heat in New England Niantic Bay had a small jubilee accompanied by sulfur smells [Crabs Pick Land Over Niantic Bay, August 7, 2009, WTNH, Jamie Muro] and the infamous August 1898 die-off of Narragansett Bay, Rhode Island contains similar accounts. I agree with Dr. Scott Nixon who in 1992 said that a century before the account of A Meade could not be improved. I also agree and repeat Dr. Mead’s account here as it first appeared in 1898 after a long heat wave.

“On the 8th and 9th of September the water became extremely red and thick in various localities from East Greenwich to Providence, and the peculiar behavior of the marine animals attracted much attention. Myriads of shrimp and blue crabs, and vast numbers of eels, menhaden, tautog and flatfish came up to the surface and to the edge of the shore as though struggling to get out of the noxious water. Indeed, the shrimp and crabs were observed actually to climb out of the water upon stakes and buoys and even upon the iron cylinders which support one of the bridges and which must have been very hot in the bright sun…”

 When you read these accounts, they often share the same features within case histories: 1) a sudden or severe period of rain during extreme heat, 2) chocolate, purple or red waters, 3) algal blooms, 4) sulfur smells, 5) fish kills and 6) black waters. The smell of hydrogen sulfide or the rotten egg smell is mentioned in 9 out of 10 cases. Sulfur compounds are highly toxic and over time can be the source of “natural pollution” that kills finfish and shellfish.  Black mayonnaise, fresh organic marine compost is deprived of oxygen and turns deadly into Sapropel, creating sulfide waters.

A sulfide block is now suspected of impacting some coastal alewife runs. Although a Sapropel bottom has become in many areas a dominant habitat type and may signal a massive habitat reversal; we know very little about recent deposits. It just has not been a process of habitat change, which until recently focused almost entirely upon man-made pollutants. Anyone who has noticed an increase in leaves over previously firm bottoms or deposits that give off sulfur odors, drop me an email. All bottom habitat type observations are important as we learn more about habitats that may or may not support Megalops (blue crabs).

Black Mayonnaise Can Lead to Sapropel and Toxic Compounds

As mentioned in Special Report #8, the first accounts of the toxic impacts were from the agricultural community with older Sapropel, the built up organic matter behind dams. The New Haven Agricultural Experiment Station tested several sources of marine mud used as fertilizer and found it contained a high sulfuric acid content, four times that of “regular” stable manure (Report of the Connecticut Experiment Station, 1879).  As this organic matter collected deposits above effectively sealed it from oxygen in the water column. In time as the deposit deepened, the bottom layers became Sapropel and sulfur rich. Dredging in the coastal zone frequently removes these Sapropel deposits and is much of the reason after dredging projects local fishers often report improved fish catches and firmer bottom conditions after the source of sulfide waters are removed. Sapropel builds behind dams in high heat, or in in the marine zone behind blocked coastal inlets or above bridge and railroad tidal restrictions. It was the winter flounder fishers of eastern Connecticut in the 1980s who first grew concerned over deepening deposits of black mayonnaise (IMEP#15, 1and 2, April 2014) over bivalve flounder nursery habitats, which eventually signaled a huge winter flounder habitat failure. European organic matter pollution a century ago created an entire habitat classification system, the Saprobien System, in 1909.

One of the best current case histories of Sapropel (called sludge) is regarding the Long Island, New York duck farms which discharged into small creeks and bays collected on the bottom (Long Island Duck Farm History and Ecosystem Restoring Opportunities, Suffolk County, Long Island, New York). Here these bottom sediments become Sapropelic and shed sulfide and ammonia, nutrient for harmful algal blooms (HABS).  They rot in high heat and lower oxygen conditions and when sulfate bacterial reduction shed hydrogen sulfide gas (H2S). The presence of this “benthic flux” has been associated with the increase of the brown algal strains, which can directly utilize area (ammonia) nitrogen compounds. Descriptions of the benthic flux follow the patterns (descriptions) of fisher observations a century ago described by Mead, Narragansett Bay 1898 and later, Gaines for the Narrow River in Rhode Island, (1988). Sapropel and its impacts to bottom habitats has not been discussed for decades.

This description of page 16, Appendix D, February 2009, U.S. Army Corps of Engineers Duck Sludge fits the description provided by Stevens of Essex nearly a century before (North Cove, Essex, Connecticut, Marine Mud Harvests, 1879).

    “These organic rich sediments, often several feet deep, became soupy, black, clayey silt that had a rich odor of hydrogen sulfide, so potent that home owners adjacent to Moriches and Great South Bays complained that the paint on their homes were being discolored (Nichols, 1964, O’Connor, 1972)”

 And with decreased habitat energy (tidal flows, restrictions) smells got worse as experienced by other barrier split/ inlet systems, further descriptions (I bid) is provided by the comment below:

“Ecological degradation that was associated with the accumulating of nutrients throughout the estuarine bays continued throughout the history of the duck industry, and was heightened when the Moriches inlet was closed (Nichols, 1964 Lively et al, 1983) in the early 1950s.”

Sapropel habitat concerns are just not marine; the original classification of organic pollution, both natural and man-made, was developed in fresh water rivers (IMEP #23, August 29, 2014 – All IMEP Habitat newsletters can be found on the Blue Crab Forum™ – Eeling, fishing and oystering thread and CT Fish Talk™ Saltwater Reports, 1909). Sapropel can accumulate and show the basic characteristics in fresh water as (Megalops Report#8, 2014).

This is a description of Sapropel from a 1997 Arizona CAP study of reservoir and canal irrigation system. System managers were concerned with “organic rain,” organic matter that forms a sediment that when disturbed releases hydrogen sulfide, changed the odor and taste of water. In summer heat these water reservoirs have periods of anoxia and organic matter reduction occurs in the bottom sediments. It is a natural condition enhanced by high heat and increased biomass (organic) rains. Releases of Sapropel slurry into water distribution systems led to water customer complaints (odor and taste) and were implicated in filter system failures and clogging (waxes) agricultural drip irrigation equipment.

Water system operations soon launched “investigation” studies seeking answers to these complaints. Eventually the problem was linked to bottom water releases. In summer large bodies of water tend to stratify, surface warm water on top and colder water below (visitors to lakes in Maine will identify with this while swimming). The colder water below will become anoxic (oxygen limited) while organic debris inputs are now (grasses, leaves, woody residues from forest soils) and washed into water bodies. When that happened, waxes formed a byproduct of “leaf digestion” and the waxes clogged irrigation equipment.

Results from sampling trip to Lake Pleasant (Arizona):

“The anoxic conditions that occur in the hypolimnion during summer thermal stratification in most lakes are a result of high epilimnetic biomass that “rains” through the metalimnion and thermocline becoming trapped in the hypolimnion. This may lead to increased BOD in the hypolimnion and, therefore, an oxygen deficit. The oxygen deficit may have profound impacts on water chemistry and composition. If the sediment is exposed to prolonged periods of anoxia, reducing conditions may prevail. This may lead to the formation of Sapropel. Sapropel is high in H2S and CH4 and has shiny black color due to the presence of ferrous sulfide. This has been anecdotally referred to as the “rotten-egg” odor associated with high levels of discharge from the hypolimnion into the Waddell forebay. During the fall overturn, large amounts of sediment may be disturbed and entrained in the outlet ports of the towers.”

This is the report of Robert DeGoursey describing of black mayonnaise deposits in the Pattagansett River in August 1988 of East Lyme, Connecticut (Shellfish Survey with Gasoline Jet Pump):

“Robert E. DeGoursey, UCONN Dive Team Leader
Diver/ Video Survey of the Upper Pattagansett River Estuary, East Lyme, Connecticut

16 August 1988      UCONN Marine Sciences Initiative

Transect 3- 50 meters north of the Amtrak bridge

Area Surveyed: Approximately 25 meters in the center of the river proceeding west to east.   Depth: 1 meter

Sediment type: “All sediments observed were very fine grained, soft, unconsolidated and easily re-suspended. Divers could easily penetrate the bottom by hand to 1 meter with little resistance. No hard substrates were located. The surficial layer of sediment was oxygenated to approximately 1 cm. Characteristic H2S odor was produced when sediments below the redox layer were disturbed.”

A further second examination with the use of a hydraulic gasoline water jet pump revealed a buried oyster bed at 2 meters depth. The relic oyster shells were brought to the surface with glass shards, coal cinders and clinker chunks (thought to be remnants of steam trains coal refuse), an old bottle and the leather remains of an old shoe. Closer to the Amtrak causeway water high pressure fluidization did not allow divers reaching down far enough to pick up oyster shells. The UCONN dive team (Peter Auster, Bob DeGoursey) estimated that the high pressure water jets had removed about 1 meter from the surface, the pipe held into the hole had allowed divers to pressure fluidize about another meter with additional lead weights had penetrated another meter and the arm thrusts that had perhaps added about another meter. Any shell debris or relic oyster habitats had to be at least 3 meters and deep or more. Efforts to further examine this habitat history were suspended by high amounts of hydrogen sulfide gas being suspended in the immediate area (T. Visel personal observation).  This organic substance had most likely putrefied in high heat and then formed a layer of Sapropel.”

We were looking at black mayonnaise not realizing that at about 6 feet of depth it was Sapropel, the bacterial reduction of organic matter created without oxygen; the sulfur cycle and generating all the sulfide gas. Elizabeth Craig of the Norwalk River Watershed Association in her article “Good News From Norwalk Harbor: Flounder Population Recovers” (In the Mainstream newsletter, Fall 2013) sums it up for the rebound in winter flounder in Norwalk Harbor:

“Residents and homeowners in the Norwalk River Watershed, especially those living along river or stream banks, continue to play an important role in keeping Norwalk Harbor and the Sound healthy, so here is your friendly fall reminder not to dump leaves into the River or storm drains and wetlands. While this leaf litter is ‘natural,’ organic and biodegradeable, in excessive amounts, as it decomposes, it uses up most of the dissolved oxygen in deeper water and makes the bottom water uninhabitable for fish and other animals. Leaves and yard waste blown into the river and wetlands form a black gooey paste known to boaters as “black mayonnaise.” When black mayo forms and becomes thick enough, it destroys spawning areas of bottom dwelling (benthic) fish such as flounder. Unlike many fish that spend their time swimming, benthic fish are very dense and have negative buoyancy, which allows them to lie effortlessly on the ocean floor or bury themselves, like flounders and sole who can remain hidden in sand because of their flat body shape.

Leaf litter is known to gardeners as “Black Gold.” Used in your garden to enrich soil, it is black gold, but dumped into the river, these same leaves settle on the harbor’s bottom and become the notorious ‘Black Mayonnaise,’ destroying important fish habitat.”

The sulfur cycle and its deadly habitat impacts are not found in many estuarine studies (a bias reflected perhaps in the not so nice eco-biological services of such deposits), but black mayonnaise exists and its deeper more toxic counterpart Sapropel does also.

Conowingo Dam Study and Blue Crabs

 The Conowingo Dam study offers a unique opportunity to examine the long-term organic digestion of leaf material (contrary to many published studies, leaves form most of the nitrogen sinks in estuarine waters) in the sulfur cycle. This dam no doubt trapped leaves coming down the Susquehanna River and with tannin signatures (See IMEP #23, #26 Blue Crab Info™, Fishing eeling and oystering thread), we might be able to distinguish the organic source material fingerprints of what comprises this organic deposit.

The Conowingo sediments should have leaf paraffin that seal these deposits with increasing depth. Cove profiles (deep cores) below 12 feet should show elevated sulfur levels. The sulfide problem was described by oyster farmers here a century ago who noticed that the teens oyster shell was dissolving quicker in these “black bottoms” (George McNeil) and this material may signal increased shell loss for the oyster industry. * Blue crabbers are justified in their habitat concerns; the Conowingo sediments may tell us more about Sapropel formation than the Indian River Florida Black Mayonnaise Study currently underway. Due to the fact that the Conowingo has unconsolidated sediments (loose), some exceptionally deep cores are possible (no boulders). Since we know the age of the dam, we can tell how quickly Sapropel can from and such deep cores could tell us much more. Dislodged Sapropel deposits release sulfur compounds that quickly turn into sulfuric acid. A sulfide wash is toxic to most organisms including blue crab Megalops. Acid bottoms in high heat dissolve bivalve shell and may explain sudden soft shell clam failures as well; a favorite food of young blue crabs. Acid waters could be part of the loss of shell on oyster bars as well.

This Chesapeake Bay habitat study of Conowingo Pond could be the most important review to date. It could tell us much more about how sulfide impacts blue crab habitats. Next newsletter will detail cold-water habitat failures.

*Some of the first export organic matter studies from estuarine marshes were conducted in Chesapeake Bay. David Correll in Estuarine Productivity (Chesapeake Bay Center for Environmental Studies, Smithsonian Institute, 1978) reported export from tidal marshes of 200 grams of organic carbon per year per meter (p. 647). The Conowingo is watershed source entirely and tannin signatures (source) from organics not mixed with marine source organics. Therefore identifying sources should be all terrestrial, etc. – a clear look at Sapropel formation.

Thanks again for your interest and support.

Tim Visel

Every observation is valuable as we learn more about our blue crab population.

The Search for Megalops is part of a Project Shellfish/Finfish Student/Citizen Monitoring Effort supported by a 2005 grant to The Sound School from the National Fish and Wildlife Foundation grant #2005-0191-001.

Program reports are available upon request.

For more information about New Haven Environmental Monitoring Initiative or for reports, please contact Susan Weber, Sound School Adult Education and Outreach Program Coordinator at

The Sound School is a Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.

The latest Search for Megalops (blue crabs) newsletters can be found on The International Blue Crab Blog Spot™, The Blue Crab Info™ Forum (Northeast Crab Resources) and Connecticut Fish Talk™ Salt Water Reports.

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