Thursday, July 26, 2012

Do crabs in Long Island Sound contain pesticides? A historical perspective.

The following is from Tim Visel, contributor to the CT blue crab reports you'll find posted here.

Subject: Habitat Information for Blue Crab Fishermen- Pesticides and Blue Crabs – Megalops Program History Report #2, December 2010

The first part of July 2012 had regional news and media sources revealing that residues of two pesticides (trace amounts) had been found in sick/dying Long Island Sound Lobsters.  Connecticut lobster fishers had for decades expressed concern over mosquito control programs and the chemicals included in them.  The point of record being lobsters (and blue crabs) belong to the same insect family as mosquitoes- thus what could be damaging to them could also potentially impact both food producers and the health of lobster in Long Island. Many crabbers have asked about potential blue crab impacts, not confirmed at present.

One of the questions raised in Program Report #2- The Search for Megalops December 2010 was two personal accounts of suspected pesticide impacts to blue crab populations’ decades ago.  This report is being made available to crabbers/others who wish to learn more about blue crab habitats and possible chemical impacts to blue crab populations – especially after the Long Island Sound lobster media reports.

There is no information available currently regarding CT blue crab health on this issue.

There is no fee to obtain any of the program reports, 1 to 4.
For more information about the Search for Megalops, contact

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 – email:

Where Do All The Blue Crabs Come From?
The Search for Megalops
Tidal Creek Clam Beds and Blue Crab Monitoring
Student Research Projects

Tim Visel, the Sound School – December 2010
The Need of an Environmental Fisheries History for
the Blue Crab Program Report #2
Blue Crabbing in the 1960s Central Connecticut

Growing up in Madison, Connecticut blue crabbing was always a high point of my summer vacation.  In our house soft shell crab was a special meal, but hard shell crabs made a great salad for sandwiches.  We used what everyone else used to catch blue crabs, a piece of fish, a section of twine and crab net-- a modest low tech gear to say the least.

The big unknown was would there be any blue crabs in the creek by the cottage we rented.  Some years were great and then some years none.  We never knew until we arrived, the question was where there any blue crabs?  Tom’s Creek in Madison was a typical saltwater creek – nothing really special except it was located at Webster Point in Madison next to the Marsh summer cottages.  Mr. Marsh the original developer of the cottages built a series of modest summer rentals (no heat but a fireplace) on the east side of Pent Road at Webster Point in Madison.  Originally a salt water farm owned by the Webster family, the parking lot for the cottages was adjacent to a salt marsh and in the middle of that marsh was Tom’s Creek at the west end edge of the Hammonasset State Park.  The creek was the key factor to our blue crabbing efforts, we rarely saw them along the shore but in the creek was a completely different matter.  Tom’s creek was a supermarket of seafood species, at high tide eels, snappers, flounder, at low tide clams, oysters and of course crabs.  At high tide we would cast fish heads on twine from the banks and at low tide seek the soft shells hiding beneath blades of sea lettuce.  Some years were great crabbing drawing dozens of Hammonasset State Park visitors to crab along the banks of Tom’s Creek.  We didn’t visit Madison in the spring but mostly July/August and by that time most of the crabs were five inches point to point.  It was with great anticipation that crab nets were loaded at Hamden for the trip to Madison.  Upon arriving the question was always the same did the blue crabs also arrive?

It was a good question because despite a previous good crabbing season the next year it could be few or none. For decades now, I always wondered why?  It would be two decades later that I would begin to put the pieces of the puzzle together which I might add is still very incomplete, but the better question is when does the blue crab larva arrive and better yet from what egg supply from which the larval stages are hatched? 

It was always a hit or miss with blue crabs in the 1960s but if the blue crabs weren’t in the snapper blues were in, so we always had something to catch and moved on.  But in wasn’t that easy with dad, he loved to crab and soft shells was a favorite.  So the absence of crabs in later years was more a problem with him than with my brother Ray or me.

Mosquito Spraying and Blue Crabs

It was 1971 or 72 that the first serious questions in my mind were raised about blue crab production.  We were commercial lobstermen at the time and my father announced that there were no blue crabs in Tom’s Creek.  We weren’t really surprised because of years past but this year was different.  He had seen people crabbing in Fence Creek, a smaller but similar creek to the west very close to East Wharf, Madison, where we had lobster pots.  He asked if the next time we went by to pull in Fence Creek and check it out.  We did several days later.  The usual treatment of a blue fish head and twine anchoring above the first bed over the oyster beds; we let two heads in – almost immediately they were covered with 2 to 3 inch (point to point) small blue crabs.  We had never seen so many small crabs.  Ray and I just looked at each other.  After just a few minutes we confirmed what our father had reported: over the oyster beds were tens of thousands of little blue crabs, some just an inch across.  We left the creek and returned the next day.  Next week Tom’s Creek became an active Blue Crab population.  It would be years later that I would put some of the habitat pieces together.            

First, the presence of small blue crabs over the oyster and clam beds of tidal creeks and the absence of small blue crabs along the open beach front.  In all the seines (minnow seines) we did along the Webster Point beaches for decades mostly failed to produce one immature blue crab.  While similar seines in the creek produced quite a few small blue crabs, I came to realize that ecological differences and habitat conditions of the shellfish beds provided perhaps more suitable habitat.  While the open areas of the beach did not (we would have picked them up in seines we frequently caught a smaller crab – with a calico shell we called lady crabs (Ovallipes ocellatus).  Secondarily, that something had happened to Tom’s Creek that had turned that environment at least temporarily against them (blue crabs).  Tom’s Creek had soft shell clams, hard shell clams and oysters such as Fence Creek, the tidal range was identical, no observed difference in salinity or temperatures.  Nothing I could think of could explain why Fence Creek, 1.25 miles away could have tens of thousands of blue crabs while Tom’s Creek had none – not one it seemed.  We tried to catch one but couldn’t on at least two attempts- not one crab.   

The difference in blue crab abundance between the two creeks was hard to explain.  We thought about it and it was my father who offered up an explanation.  Earlier in the spring the mosquito hatch had been quite severe along Hammonasset meadows and into the park camp grounds.  It was the practice back then that such heavy mosquito outbreaks were followed by spraying insecticide.  He concluded that some of it got into the creek and killed the small blue crabs (“Silent Spring” was one of his favorite books).  It was hard to ignore his theory but I doubted that this was the cause of the absence of blue crabs.  However our transplanted Fence Creek blue crabs did very well and were of source of large blue crab adults for us and numerous others from the Hammonasset State Park.  We would watch blue crabbers come and go and think of our blue crab transplant, why? 

In 1982 I would change my feelings about the blue crab and insecticide link.  On Cape Cod more than once I was called into investigate sudden die offs of crabs – green, fiddler and blue crabs.  In the two cases in Falmouth each was connected to watersheds containing cranberry culture/bogs.  On one occasion at Green Pond I noticed a cranberry grower applying chemicals to a nearby field – it was an insecticide.  The heavy blue crab mortality had occurred just after a heavy rain.  As soon at I noticed the cranberry bogs I thought of Tom’s Creek (after Ella Grasso’s administration the spraying for mosquito control was sharply curtailed) and the possibility of insecticide application could harm crabs, which in the Green Pond case had apparently also killed green crabs and fiddlers in large numbers. Since my employment at the University of Massachusetts, Cape Cod Extension Service, the cranberry industry has embraced IPM, Integrated Pest Management. Later that summer (1982)Green Pond would go anoxic and killed many small juvenile flounder that lived on or near clam beds – shell cover - something that has been found also in Connecticut habitat studies with bivalve shell litter a decade later.  Small flounder prefer shelly bottoms so did it seemed blue crabs on Cape Cod did also.

If Fence Creek had blue crabs and Tom’s Creek did not, this explanation insecticide seems plausible, but the next question was where did the blue crabs in Fence Creek come from and if they arrived into the creek in which form, we have never seen such large numbers of juveniles moving along the shore, perhaps they are easy prey for many species.  Instead we became suspicious that blue crabs arrived in our creeks as a very small microscopic stage and settled into habitats similar but not identical to the Chesapeake Bay setting among shellfish and clam populations in the creeks.  That would explain the sudden appearance of small blue crabs in April/May but that would need a female blue crab spawning population (tremendous) from the previous year.  We began to ask, where do all the blue crab eggs come from?

Standing Stock Populations – Annual Megalops Production Outside of Connecticut

Carrying Capacity for Blue Crab Habitats in Connecticut

The blue crab is amazingly fecund organism for its relatively short life span; a female crab is capable of producing up to 2,000,000 eggs in an abdomen egg sack called a sponge.  Similar to our lobsters here, this protruded egg mass is carried by the female until the eggs ripen and hatch.  They then are at the mercy of tides wind and currents as a planktonic crab larvae drifting or wandering.  The carrying capacity is limited by the size of the female spawning population and sufficient habitat after zoeal (microscopic) and Megalops stages six to 20 days later.

At the end of Megalops, blue crabs settle to the bottom and take on both pelagic and benthic characteristics they walk and swim seeking out lower salinity areas and shelter from numerous full salinity predators with plentiful food.  They need shallow somewhat protected areas often found in creeks. It is thought that tides and waves would kill Megalops set along the beachfront. It is at this time that blue crab in response to rapid growth begins now a lifelong shedding process, casting away exoskeleton (its shell) as a new soft shell is created.  Female soft shell crabs are especially vulnerable to predation so instinctively hide until the shell is hard in 5 to 10 hours.  They can be captured often protected by a clinging hard shell male.  It is at that point that fertilization often occurs.

Egg hatches vary as to temperature, in the Chesapeake region an early June hatch can produce visible blue crabs by August and three months later, November crabs can be 1 to 2 inches across.  In Connecticut, our populations reflect a much different story, we do not see millions of 1 inch crabs in November and December, and we now often see them in March or April, why?

In the 1980’s, and while working with Project Oceanology, a nationally recognized marine environmental educational program based in Groton, CT, we sought out the location of female crabs that had egged out or had developed a sponge.  We trawled the mouths of the Thames River and Poquonnock estuary, Pawcatuck, Hammonasset and East River systems in search of them.  We found a few but not the tens of thousands or millions that it would take to provide the survival necessary for the crabs now observed in CT.  That has matched observations from the recreational fishery itself; female sponge crabs in the 1960s were a rarity in Connecticut.  In decades of consistent shore crabbing I have only seen a few sponge crabs here in Connecticut, Rhode Island and Cape Cod.  Many crabbers mistakenly think that a darkened (apron) abdomen is an egg bearing female.  It is only considered egg bearing when the sponge egg sack is truly extruded.  Since high school, I have wondered why there are great population changes in blue crabs, some great years and then none.   They live to be 5 to 8 years; a good year should be followed by another?   In 1974, I asked the State for an experimental license to trap blue crabs for commercial purposes, noticing a pronounced fall migration out to deep water.  During this time my brother Raymond and I fished about 120 lobster traps between Clinton Harbor and the East River extending out to Faulkner’s Island. In the fall, we would catch large blue crabs; I began to believe that they don’t make it. So to me, in the 1970s it was resource going to waste.

Every year it seemed, in late November and early December we started trapping adult blue crabs in our lobster pots, first along the shore and finally in deeper water.  A local fisherman, John Walston, operated an eastern rig trawler out of Guilford Harbor confirmed this migration.  Mr. Walston, a commercial fisherman utilized a Wilcox flat net otter trawl primarily for catching winter flounder.  His towed area was between Kimberly and Faulkner’s Island and produced fresh winter flounder for local fish markets (1960s).  He also sold lobster bait and my interest was in that area.  While still in high school, I asked him about the blue crabs on deck and although he considered them a nuisance to his flounder business, he saved them for people he knew.  The area that he fished was the spot that female “blue crabs go to die”.  His words were to the effect that none make it out alive.  Asked when that happened, he responded February/March, “the starfish get them.”  That was the Kimberly reef area. My suspicions were apparently confirmed our blue crab year was a year-to-year event.

If none returned, then how was the reproductive cycle continued and if we have a great blue crab year, such as this one (2010) that must have needed a substantial female “sponge” population in 2009.  By 1988, after the Project Oceanology cruises, I was convinced that our population was perhaps not really “ours” but from somewhere else.  Perhaps connected to a transport system, we call the Gulf Stream.  My 1974 efforts were based primarily on resource waste and a new commercial fishing opportunity.  If large numbers of blue crabs were going to be eaten by starfish as claimed by Mr. Walston and other commercial fishermen, then returned females could not egg out, they didn’t have a chance.  Large numbers of “sooks” with eggs just didn’t happen in our waters (1970s).  In other words, the blue crabs not caught in the recreational fishery using primitive gears never returned and they ended up as a meal for hungry starfish instead. In 1978 I resubmitted a second proposal for a boat only Chesapeake style trap fishery October 1 to December 1, which was declined.  (It was thought that uncaught crabs returned to the same location following year.)

In the 1980s Gef Flemlin of the New Jersey Sea Grant Program then began working with Gulf Stream currents.  He documented those large rings of cyclonic rotations of warm water that on occasion would break away and sweep warm waters northward hitting the area between Long Island and the Cape.  It immediately hit me- that is where the eggs are coming from – down south from the Chesapeake Bay.

Bill Wilcox working for the University of Massachusetts Cooperative Extension Service and later the Martha’s Vineyard Commission has offered the same conclusion as a possible Megalops source (2005); his report is on the Internet.

“In the Chesapeake, the larvae (called zoeae) exit with the ebb tide and spend 30 to 45 days on the inner continental shelf passing through a number of life stages in the planktonic community. The final stage is only 1 millimeter wide.  They then metamorphose into the Megalops stage.  This stage is capable of swimming to the surface at night and downward during the day. At the right time it migrates vertically in the water column to ride wind driven currents as well as flood tide water’s back into the Bay.  There they look for an opportunity to settle into aquatic vegetation.  The Megalops stage lasts 6 to 20 days.  At the end of this stage, the Megalops molts into a juvenile crab (J1 stage) that is about 2.5 millimeters across.  It is likely that the crabs we recruit while a summer inlet is open originated from other ponds possibly quite remote from the Vineyard.  The combination of prevailing southwest winds, northward flowing Gulf of Stream as well as eddies and gyres that break loose from the Stream could transport them from several hundred miles away during the 50 day plus or minus planktonic stage.”[1]

The question remains if we do obtain Megalops from the Chesapeake region when do they arrive and where or what habitats do they prefer.  That is where high school marine science classes can help, they may be able to find them.  A logical place would be tidal creeks with living clam and oyster populations.  Samples of the bottom (not shellfish) could contain very small Megalops stage blue crabs.  That would necessitate a soft bottom community assessments and the use of a key to identify species.

Some of the assessment methods used with a very successful DEP program – Project Search might be suitable here.  Project Search has developed fresh water sampling techniques for use by volunteers and schools.

That program perhaps can be modified for an estuarine study – The Search for Megalops.

A second component would allow a seasonal boat only Connecticut River experimental trap fishery (not the hand operated pots) but the chimney style Chesapeake Bay “chicken wire trap”.  If large numbers of crabs did not return and are consumed by predators or killed by storms, it is a source of fresh Connecticut seafood going to waste?  Local CT River fishermen have often reported that the crabs never return in early spring- too much fresh water but did mention the local assemblages (mostly female) over wintering location off the Stonington Harbor Pawcatuck River (1960s). The third and more likely more controversial explanation is the link between insecticide use and blue crab mortality especially in the smallest sizes.  A final part of the puzzle might be determined by a DEP bottom trawl study of the area of Kimberly Reef and Faulkner’s Island focusing upon what Mr. Walston called the flounder bottom, east and north of Faulkner’s Island.  If large numbers of crabs go out to deep water (they need to go somewhere, we had millions of crabs in eastern CT last year); this area might provide some clues- he once termed it Connecticut’s blue crab graveyard.

Summary – It is clear that within the last decade, the population of blue crabs has soared; one would need to go back to the turn of the century to see such abundance.  It was a warmer than average period 1890-1920 and very hot in New England.  That is when so many shore communities started as a summer relief from the extreme heat in the cities.  That is also when numerous “salt water farms” such as the Webster Farm in Madison (Webster Point) were subdivided into lots for shore cottages along Connecticut’s coast. Blue crabbing became a popular shore activity at that time.

It is also true that a clear environmental history is needed for the blue crab and blue crab habitat.

If the summers continue to warm and winters become milder, the blue crab could indicate the first habitat shift of global warming here in Connecticut.

The increase, a welcome addition to crabbers and blue crab consumers alike, it comes as cold water species such as winter flounder and lobsters continue to fall.

Appendix I – Blue Crab Life Cycle Questions
Insecticides in Coastal Waters

I’m aware that blue crabs can survive several years as adults but even that is open to question – some say 3 to 5 years while other estimates go up to 8 years.

What was puzzling between the Tom’s Creek and Fence Creek event 1970-71 was the Blue Crabs were present in the creek bottoms in early spring – early enough to be influenced by mosquito spraying in May – June or the previous fall.  One explanation was the Megalops stage had arrived in the fall in large numbers in both creeks.  The suitable habitat appears to be shallow clam and oyster populations (even this needs to be confirmed) and over wintered in sandy shelly bottoms.  The explanation was that active insecticide fogging in the Dowd’s Campground had drifted into the Tom’s Creek Watershed.  (Spraying was common and I witnessed several spraying operations, the state mosquito control office, called the Vector Division, and was 1/2 mile north of Hammonasset State Park, where it continues today under a different name and mission).  One explanation was the insecticide had effectively killed the Megalops stage in Tom’s Creek while Fence Creek had no similar spraying.  As the Megalops started to grow in Fence Creek, the population difference became noticeable between the two systems. Local currents and tides made it impossible that only Megalops would be transported into Fence Creek and not Tom’s Creek.

What we didn’t notice and was quite apparent by absence, was adult blue crabs.  We usually didn’t start crabbing until late June or July.  Several earlier attempts did often yield blue crabs but they were rarely legal size 5 inches point to point.  It seemed to us at the time blue crabs grew to be legal size by mid to late summer.   Whatever had happened to Tom’s Creek had happened between late fall and early spring, the only difference was the mosquito control spraying.  Tom’s Creek had always been good – as areas that were adjacent, were also good for crabbing.

The stage that interested me the most was the Megalops stage but even that has its own questions.  Several papers on blue crab life history refer to the unique ability of blue crab larval stages when faced with cooler water temperature can in fact hibernate or suspend further development.  That would help explain the growth/survival differences between our waters and those of Chesapeake Bay.  In southern waters Megalops can grow longer and hibernate as juveniles in our waters Megalops hibernate over the winter and perhaps begin to grow when the waters warm in the early spring.  The blue crabs may be close to one year by date but only grew for more than 6 months.  That would explain slower growth in cooler waters – In late June in the Essex area only one in five crabs were legal by August only 1 in 25 crabs were “short” or sub legal (2010).  Catches in the Stonington area even in August showed larger numbers of crabs had yet to reach legal size.  (John Roy, senior aquaculture teacher, personal communication) – We really don’t know that much about blue crabs in our waters; additional studies therefore are warranted.  

Student research projects over the summer must be accomplished with field notes/observations, methods.       

[1] Blue Crab (Callinectes sapidus) ecology; review and discussion regarding Tisbury Great Pond, March 2004-modified May 3, 2004- Report by William M. Wilcox Water Resources Planner, Martha’s Vineyard Commission, Funding provided by the Riparian Owners of Tisbury Great Pond.

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