Thursday, May 16, 2013

2013 Connecticut Blue Crab Report #2

From Tim Visel of The Search for Megalops:


The Sound School – the ISSP and Capstone Project Proposal
Building a Network of Citizen Monitors
The Search for Megalops
The Connecticut Blue Crab Population Habitat Study 2010-2015
You Do Not Need To Be A Scientist To Report!
 

The Search for Megalops Program Report #2 Blue Crab Year

  • Southern crabbers receive poor survey news
  • Climate patterns continues for another 60 days
  • Watch for Megalops “waves”
  • Energy events transition habitats
  • It’s not over, three opportunities for rebuilding stocks
  • A blue crab report from the field
  • Blue claw crabs in Barnegat Bay, New Jersey
 

May 15, 2013

Southern crabbers receive poor survey news –

Two days after the first program report for Connecticut Blue Crabbers Chesapeake Bay crabbers also received grim news.  On April 19th Virginia and Maryland released the results of a Chesapeake Bay wide winter dredge Blue Crab survey – both showed huge drops in the number of estimated sub legal blue crabs.  The winter dredge survey looks at the number of adult hibernating crabs and the number of young crabs estimated to shed into the fishery (Legal size) within 6 months.  It can also provide an estimate of the numbering over wintering female blue crabs that could potentially spawn.  The winter dredge survey is conducted by both states and combined in the late 1980s as a cooperative study.

The 2010 and 2012 Chesapeake Bay blue crab years were very high (similar to CT reports) but took a dip in 2011 – also similar to Connecticut catches but the results in 2013 look grim, back to 2006 levels.  The winter dredge survey reported that much of the small year one crabs (2 inches) suffered a loss of nearly a half billion crabs.  That year class seems to have taken a large hit, perhaps signifying a habitat “event.” 

The 2013 Chesapeake Blue Crab fisheries may face catch limits, but it is far too early to predict the full impact of the survey but early indications do not support higher than average catches.  One of the factors acknowledged in the report is a growing awareness of the predator/prey relationship of red drum.
Number of Over Wintering Female Blue Crabs Holds Hope

The only glimmer of good news from the Chesapeake survey was an increase in the number of over wintering female blue crabs that recorded an increase of 95 million to 147 million (Marine Resources Commission Commonwealth of Virginia Press Release, April 19, 2013).  That stock has the potential to provide an immense Megalops capacity and this section is a quote from the release.

 

“Adult females are the cornerstones of the joint Virginia-Maryland stock rebuilding program that began in 2008, when a fisheries management framework was established to conserve adult females because they can spawn an average of three million new crabs each brood and release about three broods per year.”

 

Enhancing the population of female crabs was enacted with a prohibition of Virginia’s winter dredge fishery in 2008.  Many reports mention that the Chesapeake Blue Crab season is off to a slow start, but warmer temperatures could change that.

Climate Pattern Continues for Another 60 Days


Latest information for New England shows cold air will remain in place over central Canada influencing our weather for at least another two months.  New England can expect cooler temperatures and drier conditions, then turning sharply warmer.  The horseshoe storm pattern typical in North Atlantic Oscillation periods shows no sign of moving signaling a coastal low storm track that should make us in Connecticut uneasy – it’s this horseshoe shaped storm track that historically ushered in powerful coastal storms and Northeasters up the New England seaboard.  Colder air this spring could bring devastating results to already a less than certain Connecticut blue crab season.  Without a quick sharp rise in water temperatures we may face losses similar to those reported for the Chesapeake.  Many crabbers feel in fact, we may have already lost the over wintering adults.  As of May 3rd no reports of blue crabs have come, most of the same time as last year had one or two reports every week.  It’s still early yet for a complete prediction but the next few weeks are critical.

Watch for Megalops “Waves”

One of the features of blue crabs larvae mentioned in earlier reports is it ability when faced with colder temperatures to suspend post Megalops development – some accounts claim for up to four months.  So some of the last reproductive Connecticut larvae crabs may have survived the winter and we should see those “star” crabs on or before June 15th.  A second wave of Megalops from a 2013 reproductive cycle should appear July 30th to August 15th.  This is of course depends upon habitat quality, and the Hurricane Sandy.

The impact of bottom disturbance is thought to be significant upon hibernating adult crabs, seeking muck bottoms adults often will find eelgrass in soft bottoms and borrow in and wait the cold temperatures living on stored fat reserves from the summer.  A strong storm can rip up the soft bottom and eelgrass exposing the crabs to a whole host of predator species, conch, and starfish but perhaps the most aggressive is the Blackfish (Tautog) which will punch the crabs back with its teeth breaking its shell.  A Guilford fisher from the 1960s used to trawl near Kimberly Reef Long Island Sound for winter flounder who described it once to me as Connecticut’s Blue Crab graveyard – an area between Faulkner’s Island and Kimberly Reef where blue crabs would try to find soft protected bottom for the winter – only to be pulled out of the mud by Northeasters providing a feast for conch and starfish (Mr. Walston personal communication).  Catches of winter flounder by trawl nets would yield two the three bushel of large blue crabs until February or March after that Mr. Walston claimed “they were all dead.”  Some people living in the Guilford area may recall this older eastern rig trawler with trawl nets by the Guilford Sluice dock in the 1960s.  Although the adults would benefit from a mild and calm winter severe cold and storms were devastating to the adults as recorded in the areas north of Connecticut.  For the smallest reproductive life stage in shallow water – with bivalve shell litter and vegetation it might be different.  It is possible for the reproductive size to survive this energy appearing as a wave of Megalops from the hibernating Zoea stage.  This would occur as a wave of Megalops in the spring as a “carryover” from the previous summer productive cycle.  To make it they would need to be in shallow protected areas such as salt ponds.

Where to look for the first Megalops this year could be in some of the salt ponds in the Bridgeport/Fairfield region which have reported incredible Megalops sets in 2009 and 2010.  A big question here and its asked frequently is the impact of not only cold temperatures but also of bottom disturbance – upon the very small Megalops.  The truth of the matter is we just don’t know – we have two indicators to consider temperature and energy so it will be difficult to be certain about each.

Energy Events Transition Habitats


The energy pathway of storms and of course Sandy now is the largest question.  The energy of Sandy for sub-tidal marine habitats is similar to the habitat changing impacts of terrestrial forest fires.  Only in this case it is rare to have a series of devastating forest fires on the same land – there is just not enough fuel to support them but in the marine environment that is not the case – energy events happen in cycles and history tell us that a series of hurricanes in the same or similar geographic region can in fact happen – in fact the 1950 hurricane season here in New England had three Hurricanes Able, Dog and George all with similar storm tracks.

If the energy events come in a quick series habitats did not have time to re-stabilize and if combined with changes in temperatures they “reverse.”  We have seen a series of habitat reversals in Connecticut the past two centuries and with each a change in species.  (See Blue Crabs and Climate Change Report # 11, July 27, 2011 and Blue Crabs and Climate Change 8/2/2012).  The habitats had not fully re-stabilized from Irene but the eastern and central blue crab seasons were good, last year now have had two very powerful hurricanes (now Sandy) and habitats have started to reverse – the buildup of muck (Sapropel) appears to be lessening and firmer bay bottoms now appear to be holding larger amounts of juvenile winter flounder.  It’s still too early to make a call about blue crab populations in general, but the 2013 season could help answer the energy question also.  It looks like the cold has perhaps dealt a blow to the post Megalops stage, the question is still open on the impact of energy on the Megalops sets themselves – the largest question is year 2 class the 3 to 4 inch range, if they were able to survive this energy in the shallows.

It’s Not Over – Three Opportunities for Rebuilding Stocks


One of the first studies to identify a spring wave of Megalops after a winter season was a 1965 study of the Blue Crabs in Texas by William More.

In this study a significant Megalops stage was found in Texas bays during February/March then August to October and two district waves of Megalops were reported.  Other researchers were also identifying this spring and summer sets – perhaps as a survival mechanism and also two years or two reproductive cycles (successful waves) combined to enhance a single season total catch.  The reproductive success safety could also then be spread over two years despite poor conditions in one.  “Seasonal patterns of availability, based on the occurrence of Megalops in plankton samples taken in Gulf passes to major bays, varied from bay to bay (Table 2).  Megalops were present in the samples during all months, but the largest catches were recorded in spring and summer.  Similar availability patterns were reported in Louisiana by Darnell (1959) Pg 218” – A Study of The Blue Crab in Texas William R. More (1965).

If the spring Megalops was lost a summer set is still very possible – if both sets are lost than a very poor season results.  It is possible than Connecticut native Megalops set could have survived the long winter and be visible as star crabs in June.  If not then surviving females (if in large numbers) could provide star crabs in August.

The third opportunity is a transported Megalops set from the Chesapeake Bay itself – pre Megalops that gets carried from the bay and hitches a ride on Gulf Stream currents and prevailing winds, deflected into northern areas in midsummer.  This has been thought to be a major influence in our Connecticut fishery and to the Cape and Islands further north.  So we have three chances for a Megalops set this summer, one significant set should be noticeable by August.

A Blue Crab Report from the “Field”


As vocational educators and institutions we strive to have young people experience “real world situations” in educational formats.  For the marine environment that involves “boots on” field work and in this case a small blue crab study.  Two Sound School students who attend from Cheshire Connecticut conducted such a study for blue crabs while on vacation last summer, and Cole London wrote up this experience for our newsletter.

Field work (an old agriculture term) can be its own challenge, changing weather, biting insects, the unpredictable equipment failures, etc but this case science can also be enjoyable and a “work” experience at the same time.

Perhaps a Capstone Project in a few years? 

Thanks for the article – Tim Visel

 

Blue Claw Crabs in the Barnegat Bay, New Jersey By Cole B. London

     My Megalops Study for blue claw crabs was completed in the Barnegat bay in the Town of Seaside Park, New Jersey.  Seaside Park is located on the barrier island named Island Beach.  In the State of New Jersey a legal “keeper” blue claw crab for non-commercial use is 4.5 inches from point to point.

     The water depth of the bay varied from a low tide of three to five feet and a high tide of six to eight feet.  This study began on August 7, 2012 and ended on September 3, 2012.  The purpose of the study was to examine and record the characteristics of the blue crab population.  There were a total of 160 hard shell crabs caught, 0 soft shells.  There were 22 females and 36 males caught which measured 4.5 inches or larger from point to point.  The remaining 102 blue crabs were less than 4.4 inches from point to point; many of these were much smaller as in 3.4 inches or less.  There was no sponge crabs caught. 

     I went out in a 20 foot runabout using four sided wire traps to catch crabs in a habitat of vegetation during the daytime in sun and overcast skies.  I also crabbed from a pier using the traps, drop lines and a net.  The habitat of the pier had some vegetation but was mostly muddy/sandy habitat.  The traps were purchased and the drop lines were assembled from wood, white cord and a metal clip.    The bait was mainly bunker which was purchased frozen and cut into three sections then clipped in the bottom of the trap and clipped to the drop line.  On a few occasions chicken was used.   I did not notice that the crabs liked on bait type over the other.  I did notice that the crabs did not like the bait frozen or even cold, warm and oily seemed to be the attraction. 

     The conditions were varied throughout, sunny, cloudy, windy, choppy, at night with or without moonlight.  The pier had overhead illumination.  Day time catches ere smaller in the quantity of crabs and the larger crabs were caught in a vegetated habitat.  Large quantity catches were in the high tide, maybe because there was more room for them to swim or move around and be seen.  The small crabs, 3.5 inches or less were abundant in the PM.  They definitely were attracted to the overhead illumination and to a flashlight beam which made them easy to scoop up in the net, no drop line required.  The trap would yield multiple catches at one time because they could not escape once the line was pulled and the trap closed.  With the drop line only one at a time was caught.  This was done slowly and carefully so the crab would not feel the movement and release the bait and jump off before I could reach it with the net and scoop it up.  

     I made 17 trips crabbing which resulted in a total catch of 160 blue claw crabs.  About 65% of the catch was less than 4.5 inches point to point.  The largest was a female of 6.5 inches point to point and the larger; keeper crabs were caught mainly in a habitat of vegetation.  The water temps ranged from a low of 71 to a high of 78 degrees.  Catch quantity did not seem to be impacted by water temperature and the catch was varied at all temps.  The catches in quantity and size increased from August 25th to September 3rd.  The best catch was from the pier on August 25 in the clear PM where I caught seven crabs 4.5 inches or larger and 22 smaller.  It was the best because these seven were the most caught of that size during any one session.  Bigger crabs were caught at night overall and there were less day light hours at the end of August.  I definitely caught more crabs in the PM.  All crabs were treated respectfully and returned safely to their habitats.  Cole London, Sound School   

Some of the first bottom trawl surveys should be starting soon for New Haven Harbor; we should have some additional information shortly.

All reports of surviving Blue Crabs are significant, but it’s still very early to predict the entire season.

If you observe any blue crabs this spring (even dead ones) send in a report.  All observations are helpful.  June is a busy month for us at Sound School but hope to get one report out before graduation, see you at the Docks.

Tim

Email blue crab reports to: tim.visel@new-haven.k12.ct.us

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 susan.weber@new-haven.k12.ct.us

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

 

No comments:

Post a Comment