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BlueChip

Habitat Information for Fishermen –
Blue Crabs and Climate Change?
Tim Visel, August 2012
The Search for Megalops – Blue Crab Research for Students
Great Blue Crab Years and Then None?

This proposal (Project Finfish/Shellfish) was one of a series that looked at Long Island Sound inshore fisheries which would involve Sound School students (and students from other high schools) in data collection from habitat observations. In 2006, The Sound School started a series of special projects for marine species the first by Juliana Jakubson, (The Terrapin- Brink of Extinction – A Success Story) and quickly included other species, alewives, oysters and clams, winter flounder, conch (Sound School Green Festival, June 4-6, 2010), lobsters and blue crabs. These Capstone Project Proposals should be available shortly.

The 2007 and 2010 blue crab seasons in Connecticut were extraordinary, especially for the Connecticut River. Dense populations of blue crabs surrounded Nott Island, Essex in such numbers few could recall (2010). Many researchers have proposed that global warming trends would see pronounced shifts in prevalent species – declines in some but pronounced increases in others. After 2000, blue crabs seemed to be one of the species increasing (along with black sea bass, oysters and soft shell clams) and those that were once prevalent here: bay scallops, winter flounder and lobsters were declining or had greatly declined in Connecticut.

The 2007-2010 blue crab years did not resemble the 1960s crabbing. In 2010 in late July the catch rates at the Essex Town Dock was about 90crabs/hour. That was not the blue crabbing I experienced growing up in Connecticut. Back then, a good haul in central CT (1960s)was a dozen large crabs, and that was a multi-hour trip. Questions regarding the blue crab/lobster populations began in 1999, the year blue crabs were seen in the CT River in greater numbers. If blue crab populations were increasing the Megalops sets would provide important clues to long term habitat change.

Program Report #1 “Habitat Questions for Long Island Sound Species Shift for Climate Change” – Blue Crab Great Years and Then None? September 8, 2010 examined possible climate induced habitat shifts and blue crabs being an indicator species.

Program Report #2 “Tidal Creek Clam Beds and Blue Crab Monitoring Student Research Projects” – The need of an environmental fisheries history for blue crabs, December 2010. This report examined an environmental fisheries history and pollution concerns.

Program Report #3 “The Search for Megalops – Aquaculture Science Projects for ISSP” – The Connecticut 2010 Blue Crab Season, March 2011. The report looks at marine habitat research projects for high school students.

Program Report #4 “The Search for Megalops – You Do Not Need to be a Scientist to Report” reviews potential Megalops survey sites, August 25, 2011; An organizational plan for citizen monitoring along the Connecticut shoreline.

All Four program Reports are available from the Sound School, contact susan.weber@new-haven.k12.ct.us

Program Report #1 is the most requested report and included here. For more information about citizen habitat observations and reports, contact susan.weber@new-haven.k12.ct.us and request to be placed on the Search for Megalops Mail List Reports; they are free via email.

- The Search for Megalops -
Blue Crab Great Years – and then None?
Timothy C. Visel, The Sound School
September 8th 2010
Habitat Questions for LIS Species
Shift from Climate Change
Program Report #1

This year (2010) has been a great year for Blue Crabs for crabbers in Essex and the rest of the state in general. Blue Crabs are incredible fast growing doubling every molt (shedding the old shell) so they reach maturity in 13 to 14 months, and signify in our area a crab of 5 inches point to point with a hatch date of October – February. The problem is that in our area a historically shortened growing season prevents most sooks (females) from ever sponging out (egg out). In a half century of shore crabbing I recall seeing three or four sooks sponge out (egg visible) here in CT. I believe and subscribe to the larval drift explanation – a warm ring or (rings) of the Gulf Stream current delivers a supply of Blue Crabs larva to us. This event is also I believe responsible for the many tropical (fish) that arrive each fall at the eastern end of Long Island Sound. Large numbers of egg bearing females must now be in Connecticut waters if our Megalops set and blue crabs are in fact, “Connecticut crabs.”

Early Indications Of A Blue Crab Great Year -

In March (2010), I obtained calls from Guilford Shellfish Commission that thousands of small blue crabs were on clam and oyster beds – in shallow off shore water. This was indeed unusual for open shore areas, but more common in the past few years. In 2008 similar observations of small 2 inch crabs were reported in our Sound School Aquaculture upweller projects. Baring any powerful Nor’easters I suspected it was going to be a good year. They were in February/March about an inch across which fits the growth profile here – by May 3 inches, June 4 inches and July 5 inch legal size crabs should predominate and they did in shallow warmers areas. This varies according to water temperature; warmer water is usually attributed to faster growth. Since 2004 the increase in crab population in the CT River fishery was quite noticeable.

Warmer Waters Favors Long Island Sound Crabs -

A colleague went crabbing over the weekend in Stonington – colder water and slower growth resulted in only 1 in 5 crabs were of legal size while off the Essex Town Dock the same day, a small crab undersized is now very scarce. (August 2010), although blue crabs live for a few years, current scientific debates range between 3 to 8 years; few survive more than one year in our waters because of the difference in habitat and ecology. In the fall as temperatures drop and sunlight angle decreases crabs leave the upper estuaries for deeper waters to hibernate. At this point the ecology of Long Island Sound turns sharply against them. Upon leaving they don’t encounter the vast square miles of shallow sea grass soft bottom beds in which to hide in the Chesapeake Bay region. Instead they find relatively open bottoms (mostly hard containing little structure) and subject to both new and intense predator prey relationships with intense winter storms that can dislodge them in while in their “winter” hibernation. Once that happens blue crabs fall victim to our starfish, a common blue crab and shellfish predator.

Predator Prey Relationships – Signals of change?

Striped Bass is the first predator (a century ago people used to use large lobsters as striped bass bait) a well known lover of crab and lobsters. Migrating crabs out would first need to get by those late fall stripers. Next they find an abundant supply of tautog (blackfish) a voracious predator of both crabs and lobsters. If they make to deeper water (and away from areas subject to fresh sets – (rainstorms) long periods of rain which kills them in the rivers) they must dig into the bottom and survive the spring starfish assault. The densest area of over wintering blue crabs in LIS to my knowledge is between Kimberly Reef and Faulkner’s Island. Storms during the winter tend to dislodge the crabs and now barely able to move are easy prey for several prey species. I can recall walking along Hammonasset Beach after a storm (1960s) and watching seagulls feasting upon blue crabs thrown up on the beach. The past two decades has seen a resurgence of the channeled whelk commonly known as conch. Whelks have been known to predate upon hibernating; blue crabs and the two populations may be linked.

Environment and Growth -

Because of a few short weeks of our summer our warm estuaries support the middle of the life cycle, the best the Megalops to pre spawned adult stage and grow about an inch a month –rough timeline – again varies as to water temperature and depth.
October to February – 0 to 1 inch- 30 days – to 60 days
March – 1 inch – 90 days – but could be from a fall hatch
April – 2 inch – 90 to 120 days – after heavy spring rains and salinities change now enter rivers and creeks.
May – 3 to 4 inch crabs; enters most estuaries at 4 months
June – 4 to 5 inch 8 to 12 months old
July – 6 inch up to 12 months or more
August about the same
Sept – Oct 7 to 8 inch crabs are possible at 12 months or more
Nov – Dec migrate from shallows to Long Island Sound at 13 to 14 months
However the past few years have multiple year classes; these present a pronounced 2” size and a much larger 3 to 4” size. They survived the winter! Instead of one “year class” we may now have several.

Habitat Concerns – What is Happening to the Ecology of Long Island Sound?

The habitat quality for the blue crab seems to be improving, while at the same time lessening for that of the northern lobster, the colder and stormier 1950s/1960s is thought to have greatly impacted blue crab populations in Long Island Sound.

If large numbers of crabs do make it past hibernation stage now most agree (about 60 days) they emerge in the spring and must quickly find food and shelter. We should begin to see large adult crabs in March/April which we did not in the 1960s. A large northeaster can also be devastating – four years (2005-2006) ago we had another start to a great year but a late northeaster arrived. Willard and I saw thousands of dead 2 inch crabs under the Baldwin Bridge in Old Saybrook after several days of heavy rain; the fresh water apparently had killed them. (They were whole dead crabs not shed shells). What we did see in 2008 and 2010 was huge numbers of 2 and 4” crabs in June, too large for one year; they must have survived the winter, apparently much more successfully than the adults. That seems to be the case now according to some blue crabbers at the Essex Town Dock this past summer.

I’m sure a few adults make it in the east, but for most they find the lack of sea grass beds hard to overcome. John Walston in the 1960s who once fished out of Guilford for Winter flounder with a trawl net would land 2 to 3 bushels of big female blue crabs until February - from then on just dead crabs and starfish by the thousands which would “wipe them out” in his words. When at the University of Connecticut Sea Grant Program (1980s), I saw the first underwater videos of the Kimberly reef area and the bottom was just covered with starfish and dead blue crabs. I used to lobster the area (1960s) and each fall I would pick up a few large adult Blue Crabs in my lobster traps and wondered what in the world were they doing here? The absence of a large adult spring fishery March – April and the absence of sponge crabs with exposed egg pads (sponge) in May – June (which should predominate the female population) we just usually don’t experience this and leads to the larval dispersal concept from southern areas. If returning females return for year 2, 90% should be sponge because most are fertile at year 1. We should see this at popular fishing locations. We should be able to locate and identify large populations of female sponge crabs. The past few years did not represent historic fisheries- unless you to back to a hot period at the turn of the century (1890-1920). At that time blue crab in our area became significant and a major supplier to the New York City market – Fulton Fish Market.

That is why (and not uncommon) species living beyond its normal habitat range show great fluctuations in abundance which for in New England is usually the case. Here in CT (storms, predators, salinity). We don’t know that much about the blue crabs in our area – tagging is difficult but we do know that females seek out deep water in which to spawn (probably assures maximum egg dispersal). I think it can be said that none of the females return from deep water – however William Warner mentions this in his book Beautiful Swimmers on page 118. (It’s a great book).

“As the summer of their spawning near its close – old females go out to sea in great numbers to die.”

If our females survive both gauntlets of predators (fall migration out spring and return) the winter storms and spring rains the DEP offshore trawl surveys should pick up large numbers of sooks egg carrying females offshore in nearly spring. We usually don’t see males in the estuaries until late spring early summer but I will ask if DEP has some current blue crabs studies underway that could provide some insight into this question. Some accounts from fishermen remember crabs overwintering in deep channels of lower East River (Guilford/Madison)-(Charles Beebe personal communications, 1970)

Where do all the Blue Crab eggs come from?

Are we seeing the habitat impact of a warmer Long Island Sound?
Note: refer to Capstone/ISSP High School Student Project Proposal – Project Shellfish Finfish
Long Island Sound Habitat Restoration Committee Proposal Power Point Presentation July 2010.

To answer that question we would need to know more about the Megalops stage in our state of special interest would be the shallow water habitats that this stage is known to seek out. Field surveys and microscope examinations might be able to find the Megalops – and setting areas. But the key habitats would be those that hold and sustain post Megalops success.

If crabbing success is connected with temperature, the densest Megalops should be found in the warmer western Long Island Sound, the areas that hold post Megalops should be the salt ponds coves and creeks that contain bivalve shell or populations. These crabs might over winter better and appear in greater numbers before central and eastern sections.

To obtain a coast wide “look” observers could model the Audubon Society “bird census” or even the crabbers themselves. Often the data/catch shifts from fishermen can provide significant information about the ecology of local areas. Rhode Island Sea Grant launched a very successful citizen monitoring program (one of the first such programs – called Pond Watchers, for Rhode Island salt ponds).

Project Shellfish/finfish seeks involve marine science and biology high school students in field studies and subject of a EPA/DEP habitat restoration committee of the Long Island Sound Study in July 2010. The school systems of Guilford, Madison, Old Saybrook and Branford have expressed support for such a school project/class assignment.

Copies of the July 2010 Proposal for Project/Shellfish/Finfish are available from our adult education program. Email susan.weber@new-haven.k12.ct.us
Our school web site is www.soundschool.com