Monday, May 11, 2015

Age by Association: Barnacles may tell us when blue crabs shed their last shell


Guest post from Christine Ewers-Saucedo at the University of Georgia:

Determining the age of blue crabs is challenging. Size is not a good predictor, as blue crabs only grow when they molt – and whether a crab molts or not depends on various factors, such as gender, nutritional status and temperature. However, some of the animals that can attach to blue crabs grow continuously, such as the conspicuous barnacle Chelonibia testudinaria. Its size provides an estimate for the minimum time since molting. But growth rates, crucial to convert size to age, were not available until now.

Large female barnacle with several dwarf males attached.
We recently published a study that determined growth rates for this barnacle on blue crabs and two other host species, loggerhead sea turtles and horseshoe crabs. The motivation for this study was the peculiar sexual system of this barnacle in which large hermaphrodites (with both male and female reproductive organs) coexist with dwarf males. The existence of dwarf males in hermaphroditic systems is baffling: hermaphrodites reproduce as both male and female, so how can males, which are lacking the female function, compete with them for reproductive success? Theoretically, high mortality rates, low growth rates or a low number of competing hermaphrodites (small mating groups) should allow the maintenance of males. We found that mortality rates are indeed higher than in most purely hermaphroditic barnacle species. Given their commensal life style on blue crabs and other animals, this is not surprising. They can only survive as long as the host is alive and keeps its shell.

            While the main point of this study was to explore barnacle reproductive strategies, it also provided application new tool for blue crab researchers. We can now determine the age of barnacles based on their size. This may help improve our understanding of the age structure of blue crabs in the field. This is particularly important for understanding the “age” of mature female crabs. Once mature, females stop growing and retain their carapace (shell) for the rest of their life. They also undergo a spawning migration from low salinity estuaries to high salinity coastal areas where barnacles are more common. Thus, barnacles provide an opportunity to determine how long individual females have been in high salinity spawning areas.


Ewers-Saucedo, C., M. D. Arendt, J. P. Wares, and D. Rittschof. 2015. Growth, mortality, and mating group size of an androdioecious barnacle: implications for the evolution of dwarf males. Journal of Crustacean Biology 35:166-176.

2015 Connecticut Blue Crab Report #2

From Tim Visel at The Search for Megalops:

The Search for Megalops—Report #2—April 2015
The Sound School Regional Vocational Aquaculture Center
Blue Crab Research in Long Island Sound 2015
You Don’t Need to Be a Scientist to Report

·                     Hope for a Great Crab Year Fades as Cold Continues
·                     Did Coldwater Reduce Crab Catches on Eastern Seaboard?

Follow Megalops reports on Resources, CT Fish Talk™, Saltwater Reports and The Blue Crab Blogspot™

Introduction
With cold air seemingly refusing to budge – crabbers are concerned about the 2015 blue crab season here in Connecticut.  For some western CT blue crabbers the crabs last year “never arrived.”  This spring is very different than a few years ago which had large blue crabs being caught in the Guilford – Branford area before the blue crab season “officially” opened on May 1.  It seems whether we like it or not we are in a colder period – winters now contain the “polar vortex” bringing energy and precipitation to a cooler New England.  

Snowfall records have been broken for Boston and others had snow amounts not seen since the 1960s.  Some may recall of the gales of February 1964 and ice walls along Hammonasset Beach in the winter of 1965.  The 1960s were tough for coastal residents – colder winters and some of the busiest hurricanes seasons to hit the Northeast.  The cycle of Sapropel may be ending and with it some of habitat characteristics that signaled the increase of Blue Crabs in 1998.
For most of my fisheries history research I rely upon US Fish Commission Reports between 1880-1920. But when it comes to the Blue Crab fishery during the negative NAO of the 1950s and 1960s, I look to the same period for Commercial Fisheries Review articles. Thanks to Charles Beebe (late of Madison), I was able to spend a summer day at the NOAA Milford Shellfish lab, 1969`or 1970? Back then it was under the Fish and Wildlife Service Bureau of Commercial Fisheries (It was before the new building). I helped make chicken wire oyster spat collectors for a day. Everyone was very nice and let me take back some publications; two of which were “The Blue Crab and Its Fishery in Chesapeake Bay, Parts 1 and 2” by W. A. Van Engle, then Associate Biologist of the Virginia Fisheries Laboratory, Gloucester Point, VA.  I still have them and from time to time give them a review.

In my most current habitat research into the cause and effect of Sapropel and sulfide kills (sulfide waters and black water deaths) oyster growers a century ago also complained of black waters, off flavors and dead oysters in high heat. This was often in the vicinity of black bottoms with strong odors- and mentioned occasionally by clammers. I suspect those bottoms of producing killing sulfide levels.

In winter, blue crabs would also hibernate in these soft bottoms, protected perhaps by the hint of sulfide to keep starfish away. But these sulfide compounds do produce an odor (and perhaps off flavor) and on page 15 of Part 1 is found this paragraph of June 1958 publication CMFR15 is found this quote:
“Crab dredgers report that in winter in the vicinity of Cape Henry, crabs are often of strong odor, here shells deeply pitted and produce a very small quantity of very inferior meat, and catches of this kind are quickly dumped overboard. 

Theses crabs may be remnants of “ocean” schools (Truitt, 1939). Those with a strong odor are called “ticky” crabs, possibly because the odor is similar to iodoform which in turn is similar to the odor of bed bugs (bed ticks).”
This off taste or off flavor is mentioned in the historical oyster and clam literature as well. This is an 1876 reference to habitat condition and flavor concerns for oysters:
“The American oysters, like our own, do not prosper on every kind of soil indiscriminately. In pure sand they do not fatten, and grow very little; in mud they contract an unpleasant taste, and also run the risk of being smothered; but in mixed soils of sand and mud they develop to an astonishing degree, especially when the water is slightly salt.” (Source: U.S. Commission of Fish and Fisheries, Part III Report of the Commissions, 1874-1875, Wasting GPO 1876, pg. 297 – Oyster Industry of the United States)

There is even a slight reference to the types of bacteria that live in this anoxic organic matter that today are linked to shell disease. The Von Engle quote mentions “shells deeply pitted” the same type of bottoms off New York associated with the first 1970s lobster shell disease observations.
After 1931 habitat conditions changed it became cooler and stormier; crabs retreated to deeper areas and you can see the development of crab pots then– a response perhaps to habitat refugia to catch them in deeper holes, banks and channels. That happened to some extent last year in Connecticut the surviving blue crab populations were compressed into smaller, deeper salt pond like areas.  If you fished those areas you caught good numbers. Habitat compression can explain wide differences in catches over a large geographical region.  Compression into those suitable habitats gives an appearance that the fishery is stable (or even increasing) while other areas appear to be languishing.  Compression (jubilees) are most often linked to declining environmental conditions that influence bottom habitat quality.  Dr. Rhoads (Yale University) predicted a habitat compression scenario connected to Sapropel for Long Island Sound Lobsters nearly two decades before it happened (1984).  Warming temperatures and the spread of Sapropel are linked to massive lobster die offs.  In the heat of summer warm water near the “sediment – water interface facilitated the release of toxic sulfides and ammonia from the sediments, for the weakening or killing lobsters.”  * [Potential Climate Change Impacts On Marine Resources of the Northeastern United States, Fogarty et al 2007 page 22)]The impact of this organic toxic release was devastating to western Long Island Sound lobster population in the late 1990s.  The migration of blue crabs from western areas in 2011 may have signaled a larger habitat compression event – often described as Blue Crab Jubilees – also occurring in warm (hot) periods and also linked to organic matter digestion in historic Mobile Bay studies.

Look for the best crabbing in areas that was protected from our winter storms, deep locations such as salt ponds and bays.
 Expect the first signals of surviving crabs to be seen by May 15.
Thank you for your continued observations and questions.
Tim Visel

Hope for a Great Blue Crab Season Fades as Cold Continues
The trend in blue crab landings over time indicates warming-- less storm filled periods have the highest catch figures. However, excessive heat and a tropical system I feel contribute to sulfide toxicity, “Black Water” deaths in the north and “Jubilees” in the south, both low oxygen high sulfide events can be just as damaging as cold winters and storms. We can observe the low oxygen high sulfide events when blue crabs walk out of the water, which happened in Niantic Bay a few years ago. A very cold winter can kill adults but the most noticeable change is that our Megalops set is very late and perhaps destroyed. Several years later that impact is reflected in a sharp drop in landings. Between temperature extremes and storms combined with a relatively short life span its no surprise that Blue Crab landings over time fluctuate. One of the habitat areas of concern is the sulfate reduction of organic matter, organic waste, mostly terrestrial leaves, in high heat. This can deplete oxygen and then produce sulfur compounds as a “natural” low oxygen sulfate/bacteria reduction pathway. In times of cold or a rain/flood these oxygen-limited deposits are dislodged and creates a sulfuric acid wash. This aspect is most likely to occur immediately after a tropical system – creating a series of habitat limiting conditions, fresh water toxicity, sulfide toxicity followed by a sulfuric acid wash. I believe these conditions can be enhanced by sediment accumulations – such as those behind terrestrial dams carried downstream in thick slurries (see related articles regarding recent Conowingo Dam concerns).

Did Coldwater Reduce Crab Catches on Eastern Seaboard?
The declines of blue crabs in Chesapeake Bay has greatly alarmed some blue crabbers there, seeking management solutions to population concerns. Some of the frustration about fisheries management is often the emphasis upon the landings not habitat; we had that happen recently in Connecticut with lobster fisheries- increases in the legal gauge size, V-notching of female lobsters and finally a closed lobster season (not seen in New England since Rhode Island did it in 1904).

Did it help- most likely no in terms of habitat quality, it got hot and lobster habitat quality declined here although the public perception was that it could help the heat was the real problem. Certainly the V-notching, of female lobsters sought to enhance reproductive capacity (always good) but it would need to get colder to fully rebuild the lobster population here in Connecticut.  Reproductive capacity is important but just as significant as the predator/prey ratio.  One of the things that did come out recently and something that I noticed also was the predation of shorts (sublegal lobsters released in daylight). In shallow water you could watch Tautog attack these small lobsters and kill them, without cover while hauling traps we would drift away from a rocky kelp covered bottom over smooth sand.  In very shallow water (in the late 1960s, early 1970s it was colder and water clarity much better – less plankton). You could watch lobsters darting to escape Tautog predation, which was to increase in abundance into the 1980s.  I lobstered with my brother Ray for 15 years and we often wondered how many shorts we released in daylight never made it to the sparse cover our area of the coast provided, cobblestones and kelp was the key habitat for small lobsters, it is most likely patch eelgrass and sand mixed with shell for blue crabs. Some southern blue crabbers have raised similar questions about predation from red drum.  In an 1887 description of Maryland’s fisheries it mentions a large drum fishery, the bait for which was blue crabs,
“In this fishery the hooks are baited with crabs or menhaden and thrown well out into the surf, after which they are slowly drawn to land, the first (drum) seizing them as they pass through the water.  It is said that the catch of drum in this way is frequently so large that there is a good deal of difficulty in disposing of them locally in the locality, and many are thrown away for lack of a market” pg 426 Geographical Review of The Fisheries – Maryland:  Saltwater fisheries.  The Fisheries and Fishing Industries of the United States – by George Brown Goode, Section II for the year 1880 Washington GPO 1887.”  Drum is frequently mentioned in the historical literature as a serious predator of blue crabs.   
 
Habitat Change Is Evident In Some Areas
Recent hurricanes have dislodged a tremendous amount of organic matter, which sent downstream in high heat kills eelgrass and covers estuarine shells. It is sulfur-rich and termed Sapropel.  Long periods of a negative NAO pattern tends over time to remove Sapropel deposits; a setting the stage for the cycle of eelgrass [Note although much has been written about the importance of eelgrass to blue crabs, some of the best blue crab catches for the Chesapeake occurred when eelgrass populations were low, I suspect estuarine bivalve shell cover to be just as important to blue crabs in the Megalops state as eelgrass meadows which at night can shed high temperature toxic sulfide compounds.]
Eelgrass seems to have its own habitat clock and the sandy-“clean and green” eelgrass has cover (structure) benefits to Blue Crab Megalops but at the end of long hot periods eelgrass tends to collect organic matter buildup and assist sulfate reduction “the brown and furry” eelgrass, a strong negative factor to Megalops’ survival. A better indicator may be habitat stability followed by warmth, such as New England recently experienced. The past decade New England has seen some outstanding blue crab years but regulations have remained basically unchanged for a century. Something occurred here that made habitats better for blue crabs when eelgrass populations were still very low.  The last major die off of eelgrass in New England started in 1982 opposite the increase in Blue Crabs.

The predator-prey relationship has also been mentioned regarding red drum, also a significant factor and recorded in the historical literature. In an effort to protect oysters from drum accounts include placing of brush occurred here to protect oysters around the turn of the century in western Connecticut.  In 1828 several Connecticut Captains took “natural bed oysters from the Saugatuck River, and planted them between two hummocks near Keysers Island (called Manresa today) South Norwalk.  These men planted bushes around the oysters to keep the Drumfish from eating them” pg 122. 

Annual report of the Bureau of Labor Statistics of the United States Vol 5, Part 1, 1889.

The Drumfish mentioned is most likely Black Drum listed today as an exotic species by CT Dept of Environment and Energy.  A specimen however over 15  lbs was caught off the New Haven Breakwater in 2001.  In southern waters black drum is a serious oyster predator at times comprising 30% of diet (Brown et al Estuaries and Coasts Vol 31 pages 597 to 604).  The reference of the extent of the protection by this effort leads me to believe that it was warmer then – 1820s as Drumfish must have been so prevalent as to cause such a concern.     

Predator-prey relationships also tend to follow life cycle changes - that appeared with oyster culture and starfish in Long Island Sound.

Cold weather over time appears to be the largest factor and why so many times limits on catches just no longer work- (recent case of the lobsters in Connecticut) and in the face of declining resource abundance management efforts tend to protect or conserve reproductive capacity while habitat capacity is often overlooked. Most likely the best example of this is the spawner sanctuaries set up in association for oyster culture in Connecticut a century ago.

When oyster sets started to fail in the 1920s, the oyster industry here sought to place “spawners” on cleaned areas to increase reproductive capacity.  This effort expanded in the 1940s as temperatures continued to cool (especially after 1931). This excerpt is from a 1953-1955 State of Connecticut Shellfish Commission Report, page 4, under the section titled, “Spawning Beds:”
“Report of the Shell-Fish Commissioners - Spawning Beds
During the period from July 1, 1953 through June 30, 1955, the program of establishing spawning beds, as described in the 1950-1953 report of the Shell Fish Commissioners, was continued.
After investigation and field tests by Dr. V. L. Loosanoff, Laboratory Director of the U.S. Fish and Wildlife Service at Milford, Connecticut [now NOAA], and through the cooperation of some of the oyster growers who supplied the spawners and the labor, new spawning beds were established in the following areas [1954]:
West Haven—in the Cove River, located just westerly of Bradley Point
Milford – in the Wepawaug River
Southport – in the Mill River
The Shellfish Commission [State of Connecticut] sincerely hopes that the public will respect these spawning beds, since it appears that they offer the major hope of revitalizing the oyster crop in the State of Connecticut.”
Although the aquaculture industry supported the oyster spawner sanctuaries, they did not over time prevent oyster set failures. It was gradually getting colder and storm frequency and intensity increased.

The best oyster sets now occurred in salt ponds where warmer temperatures created habitat refugia, of warmer waters. Although the concept of spawner sanctuaries continued for decades oyster sets still declined for decades. Having sufficient oyster spawn in the waters is often not enough – habitat conditions need to be “just right” – clean, shell surfaces with warming waters that follow a mild winter. The 1950s and 1960s were known for long periods of habitat instability; sharp differences of hot than cold, quiet and then extremely stormy. Many seasons’ oyster spat arrived too late for planted oyster shells or froze in severe winters. When you look at the blue crab/oyster landing statistics, they tend to follow each other.

In the absence of habitat quality information pollution and overharvesting are often offered up as logical reasons for resource declines. While the simple fact was gradually the climate was turning against the oyster and oyster fishers as well. The problem is the expansion of the oyster industry occurred during a period of immense pollution and very hot weather (1890s) and it collapsed in cold (1960s).

Blue Crab Habitat Expansion After 1998
Long Island Sound perhaps is a good place to examine this habitat refugia concept for blue crabs. I was very much surprised by the recent surge in blue crabs here recently and historical records do indicate a large-scale habitat reversal even in New Haven Harbor itself. The only difference is being so far north we need long periods to see large changes in abundance.  Southern areas perhaps not so much – more Southern areas have shorter time periods, as heat perhaps is not that much of a factor. Perhaps predators have larger roles in southern areas. Energy also is perhaps a negative factor for the smallest blue crabs, as estuarine shell and vegetation also reverse in long cycles. Adults might be able to withstand high energy colder cycles better. More recent examination of sulfide formation in low oxygen marine soils appears to govern Megalops sets as extremely hot may be just as important as extreme cold. Combined with all these factors it is most likely “natural” to have large changes in blue crab abundances.  When you examine the historical Blue Crab literature you see that mentioned many times.

Fishery managers tend to stay within the traditional management techniques but habitat quality, environmental quality and predator prey ratios are extremely difficult to address (Special Report #4, 2014).  That is why it is necessary to take a step back, so that the picture can take a much larger, broader view. Storms and temperature with overlapping habitat clocks for habitat quality (and of course predators) fills in many biological blanks for the reproductive analytical management models.

Another basic premise that has plagued fishery management models is habitat stability, most of the models assume or assign a fixed value to habitats, (such as the eelgrass issue) but as fishers already know habitats are not stable long term, they change eelgrass meadows come and go and with them their habitat services. Prey species increase or decrease (many respected biologists have weighed in on the dramatic increase in Maine’s lobster catches recently noting that Cod a known huge predator of lobsters is at “historic” low population levels). Temperatures and organic loading (from humus as well as natural sources) change estuarine marine soil pH and the turbulent 1930s and 1940s decreased habitat quality for the soft shell clam sets.  Estuarine habitat quality impacts population levels.

One of the best papers on the Internet that describes these early habitat quality attempts is a monograph bulletin titled, “Back Bay” / Currituck Sound Data Report Introduction and Vegetation Studies Cooperative Studies 1958-1965 compiled by Bureau of Sport Fisheries and Wildlife, North Carolina Wildlife Resources Commission Virginia Commission of Game and Inland Fisheries.
The report describes observations of duck hunters and the habitat succession of grasses in part with observation of storms, salinity and flushing rates. Grasses would come and go and so would the population of ducks. We now know for example the eelgrass declines of the 1930s was devastating to Brant but that other grasses favored other species.

If you are interested in environmental history, this report is one of the most comprehensive I have found. It is on the internet. “Back Bay-Currituck Sound Data Report” subtitles “Introduction and Vegetation Studies.” This 1964-1965 report includes Currituck Sound references dating back to the 1820s, providing an environmental history relating to inlet modifications (energy pathways), salinity changes and changes in dominant species – a habitat reversal noticed by researchers and duck hunters.

When ocean water exchange increased in Currituck Sound, higher salinity species became dominant; when exchanges declined, fresh water species reversed. This is a quote that describes this process; found on page 5 of this report:
“Weiland (1897) in a paper aptly entitled “Currituck Sound, Virginia and North Carolina – A Region of Environmental Change, “ stated: ‘One of the most important geological changes which has taken place along the Atlantic coast in recent time was the closing up of the Currituck Inlet, North Carolina, by drifting sands in 1828. Previous to that year this inlet formed such a passage from the ocean through a narrow outer beach into the waters of Currituck Inlet to Pamlico Sound now. With the closing of the Currituck Inlet there was the conversion of upwards of one hundred square miles of shallow salt to brackish water area to fresh water; and it is within the memory of men now living that the resultant changes were immediate and striking.

Previously the sound had been a valuable oyster bed. Within a few years the oysters had all died out and their shells may now be seen in long rows where they have been thrown out in the dredging for a boatway in the Coinjock Bay, a southwestern extension of the Sound. Further, there were such changes in vegetation as brought countless thousands of ducks of species that had been only occasional before. The salt water fishes were driven out and fresh water fishes took their place.”

Throughout the report references to dredging casting up buried oyster shells (reefs) providing direct evidence again of long ago habitat reversals. This is a long report, over 150 pages, but well worth the time. The region has a fascinating environmental history and this report was compiled during the 1960s, a time of great energy (numerous coastal storms) and colder winter temperatures. I found a few references to blue crabbing and close to any inlet, most likely have some excellent blue crab habitats. Although, the 1965 report focused upon the decline of ducks (hunting), which many areas along the eastern seaboard experienced; mild winters also improved habitat capacity for waterfowl as well – when winters turned more severe duck hunters noted the changes.

Anyone interested in the transition of grasses or habitat types will find this report to be of interest – and such excerpts describe the changes in habitats tend to exhibit over time.

For Connecticut continued cold may reduce the blue crab population, but will it increase the lobsters?  Only time and observations will tell, at least we might be able to better follow the habitat conditions from now on. The fishery management aspect of a habitat driven Megalops set has so often a target or threshold biomass (stock assessment) that is determined with no apparent connection to a habitat quality or habitat conditions needed to fulfill it.

Observations therefore could help answer some of these blue crab habitat questions. Certainly by mid-June a clearer view of the 2015 blue crab season in the northeast should be apparent.

All observation of blue crabs are important as they add to a long-term habitat history.

Email your blue crab reports to: tim.visel@new-haven.k12.ct.us.  All blue crab observations are valuable as we learn more about our blue crab population. Questions? Send me an email.

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.



* Potential Climate Change Impacts On Marine Resources of the Northeastern United States, Fogarty et al 2007 page 22 

Friday, May 8, 2015

2015 Connecticut Blue Crab Report #1

From Tim Visel at The Search for Megalops:

The Search for Megalops – Report #1 – March, 2015
The Sound School Regional Vocational Aquaculture Center
Blue Crab Research in Long Island Sound 2015
You Do Not Need to Be a Scientist to Report
March 2015
Tim Visel
·         Introduction to the 2015 Blue Crab Season
  • Atlantic Seaboard Blue Crab Indices Decline
Follow Megalops reports on Resources, CT Fish Talk™, Saltwater Reports and The Blue Crab Blogspot™.

Introduction to the 2015 Blue Crab Season
For many Connecticut blue crabbers last year’s season was often disappointing; numerous checks at the Baldwin Bridge DEEP fishing pier drew mostly negative comments such as, “What happened?” or “Where are they?” were frequently heard.  It is hard to explain how the Connecticut River Blue Crab Fishery declined so quickly when area newscasters, The Hartford Courant (June) and Fox TV News came to the Sound School last July for a Blue Crab report. Sound School’s Chris Jennings and Ceondice Johnson, both students, and Steve Joseph worked hard to catch a few blue crabs to show for the camera. In July, Steve Joseph, a teacher here was able to catch one blue crab just a few minutes before the cameraman and Fox anchor reporter, Katie Corrado, arrived to show for the camera. The Fox News’ broadcast on JULY 14, 2014 showed catches at the DEEP Marine Headquarters and adjacent to the fishing boardwalk which I feel saved the report.  Earlier in the spring, The Hartford Courant reporter, Greg HLadky, covered the rise in Connecticut’s blue crab population since 1998 in a June, 2014 article titled, “Could Global Warming Turn the Sound into Blue Crab Haven?” The 2014 blue crab season would however for most crabbers fall far shorter than previous years had. West of the Connecticut River, 2014 catches were non-existent or very slow all year.  CT River catches I observed at the Essex Town Dock never broke 8 crabs/hour ----with four lines this was the blue crabbing I experienced in the 1960s growing up in Madison, CT, not the recent past with catches of 65 to 100 crabs per hour (Megalops #3, July 23, 2013).  Those high catches seem so distant now, so are the very warm “calm” winters we had leading up to these high catch figures. 

Some blue crabbers last year did well however, knowing where habitat refugia occurs; it is these habitats (salt pond or deep coves) that hold the last good populations – and crabbing was good and at times very good. In times of declining habitat quality crabs can become compressed into those areas. In many respects, last year resembled for me blue crabbing in the 1960s  (Great Blue Crab Years and Then None, September 8, 2010 – reissued Blue Crabs and Climate Change, August 2, 2012 – Northeast Crabbing Resources – Blue Crab Forum™); good catches in some years and very few in others.

 2014 Blue Crab Season
Habitat compression can skew the season, if you knew where better than average quality habitat was (and the reason some veteran crabbers told me you need to find the crabs; they won’t find you!) chances are you did great. If you relied on previous habitat quality locations from a few years ago your chances are pretty good last year was poorer.  That happened in the Saugatuck River where once excellent spots for blue crabbing in 2011 suddenly became leaf filled and sulfide smelling areas (IMEP #27, September 30, 2014, Blue Crab Forum™ Fishing, Eeling and Oystering thread) and crabs left. The 2011 Megalops reports give an account of what happened when heavy July rains hit western Connecticut for days, then September 7th Storm Lee, and before that Hurricane Irene in 2011.  After these three rain events some productive blue crab habitats in western Connecticut were gone- not gone as recognizable areas but gone; in terms of habitat quality, changes can happen that fast (the late season, 2011 Megalops reports mention this change (Blue Crab Forum™ Northeast Crabbing Resources, 2011 reports compiled).

Thanks to some reports from Black Sea Bass fishers our CT Megalops Set (Long Island Sound) occurred late again (Megalops #4, October 9, 2014) for the third year in a row.  Worst still the reports of sponge crabs, crabs with an egg apron or mass dropped suddenly.  That does not give a positive outcome for this year, only time will tell. The only female sponge crabs were observed east of the Connecticut River last year (2014).

In 2010 I made a presentation before the Long Island Sound Study that we were using entering the season 1.7 degrees below average, but a hot summer soon erased that decline, yet a cold spring can delay the Megalops Set, an early appearance in March-April had incredible impacts on the Blue Crab season in 2010.  That happened again after very mild winters and a warm spring in 2012, which had legal size blue crabs in the lower Connecticut River being observed on April 17th (Megalops #2, April 23, 2012) and Long Island Sound temperatures of 46° on St. Patrick’s Day. This year Long Island Sound temperatures were around 34°, twelve degrees less.

Since the NAO* turned negative since 2010, our winters have become colder and snow filled.  I expect a much cooler than average spring (considering it snowed here a week ago) and we now have a giant ice cube up north ready to release cold melting spring water into Connecticut for weeks.
*For those interested in the climate feature NAO, the climate website for the State of North Carolina, I feel has the best description; it is found on http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml

2015 Blue Crab Season
How does this season look?  Slow, I am afraid, the constant pounding of estuarine bottoms from a series of Nor’easters can’t be good for small crabs, winter flounder and hard shell clams (even lobsters) may have much better habitat quality, but not so for blue crabs. Several crabbers have already asked and I was not that optimistic.

I think this year’s blue crab season will be a challenge for most blue crabbers here in CT.
All blue crab habitat observations are important. Thank you for your interest and observations as the Search for Megalops turns five years old.

Tim Visel, The Sound School

Atlantic Seaboard Blue Crab Production Indices Decline
During the past few weeks, some of the Atlantic Seaboard population catch statistics have come in- all show declines (see Blue Crab Blogspot™). Some of the indices are also in and many mention a decline in the smallest sizes- the 1 to 2-inch range. I have noticed this here in Connecticut as well. This year classes (Megalops set) appear to be missing or not nearly as abundant as 2010 or 2011 and last year’s cold winter certainly had an impact upon the Connecticut River fishery (Megalops #3, August 20, 2014).  Although crabbers tend to notice the larger crabs, the most important indicator for the future is what’s “coming up.” The Megalops reports’ observations in 2011 and 2012 include numbers of small or sublegal crabs surpassing those of legal 5-inch point-to-point sizes.  In other words, there were more sublegal crabs from legal (based upon observations). Chances are that if you caught a crab last year, it was large; very few small crabs were observed last year, except in shallow salt ponds or coves. I stopped in at the usual places last year and observed only 3 small 2-inch crabs where as in 2011 I observed at times dozens if not hundreds of them in the same area.

Range Changes – Possible Retreat From Northern Areas?
Going back to Bigelow and Schroeder (1955) they wrote that Cape Cod tended to be the dividing line between the crab indices with the blue crab “southern” species and those more typically found in the Gulf of Maine rock and Jonah “northern” species. While that appears to be the physical boundary, the Gulf Stream has much to do with some southern species going far north as do our climate patterns. For hundreds of years fishers have noted the influence of warm waters moving north bringing “southern” fish along with them, even at times the blue crab (Megalops). Cape Cod did more to steer away the Gulf Stream than divide the Atlantic Ocean into realms of species dominance – if the Gulf Stream hugged the coast of Maine it would get those tropical species each August as we do here in Connecticut.  Two years ago, several seahorses were caught in blue crab traps in Clinton Harbor – everyone knew they weren’t “native”.  I used to see pilot fish circling our mooring chains off Webster Point in Madison, Connecticut in the 1970s usually in late August when water temperatures were the highest.  I never used to think about what happened in the fall when water temperatures dropped, they most likely perished. 

This Gulf Stream feature does complicate the more northern blue crab fisheries as well and the question could be asked if our Megalops sets are reinforced by transport up here by winds and currents. The year that measures the point of increase for New England is 1998.  The index for all three states (CT, RI, and MA) shows improvement in blue crab indices all at once in the same year (1998). Blue crabs have made it into Great Bay, New Hampshire in 2010, although not in great quantities and the southern portion of Maine in 2012.

 Now the indices to our south have turned negative and we don’t know yet when this will bottom out, no one is really certain. Expect these northern blue crab populations to gradually decline as cold water reduces the population range. I have mentioned the NAO, the North Atlantic Oscillation several times before (if you want to visit a state that has done an excellent job talking about this, it’s North Carolina) population cycles that has to be considered, predator-prey relationships have a part for certain, but habitat capacity and habitat quality most likely have the largest roles and the areas we know the least amount.

Rhode Island has also noticed an increase of blue crabs (especially in 2010) and is now looking at Megalops settlement in coastal salt ponds:  the Massachusetts inshore seine survey showing the same for the Cape and Islands – recent increases in the smallest blue crabs. One of the first questions at the beginning of the Megalops newsletters was could the Chesapeake Bay Megalops make it into Long Island Sound and under the correct conditions add to the blue crab fishery here.  Perhaps the Rhode Island Megalops study (to be released shortly) may answer that during high reproductive periods southern Megalops may hitch a ride to northern waters; I believe they do.

Fishers and a Long Term View
The biology also has a factor in recent catches and blue crab fisheries management. Blue crabs have relatively short life cycles; they have enormous reproductive capacity and have the ability to respond quickly to increases in habitat quality/quantity. The boom and then bust of crab catches [The same could be said for the northern Gulf of Maine Shrimp industry]. When habitat quality is favorable, enormous reproductive potential is ready when habitat quantity declines reproductive capacity is wasted, and within parameters extinction events, an almost total habitat failure can happen (both at once). The best example to dates I have found is Bay Scallop Fishery (1910 to 1915) in Narragansett Bay, Rhode Island. As habitat conditions failed for bay scallops during the Great Heat (1880-1920), bay scallops practically disappeared from a huge deep-water bay scallop fishery there of the 1870s. 

By 1910 finding a bay scallop was rare, but by 1924 after two bitter cold winters, bay scallops were back in Rhode Island, as they, with a very short life span (30 months) quickly became a dominant shellfish species again.  At first Rhode Island fishery managers were shocked, they just didn’t have any reason for the sudden bay scallop surge, into the hundreds of thousands of bushels (1924); eventually it was summarized due to fishery management efforts, closed fisheries. But when you examine the management efforts then there was nothing left to manage, the bay scallop had gone and with it a way of life along Narragansett Bay.  But in the 1920s Bay scallops returned (not as much as the 1870s) and also the coldest winters in New England in 50 years – fishery managers commented that despite the brutal cold winters bay scallops returned not in spite of them, but because of them – they like cold and energy. Bay scallops have again “returned” to the Cape Cod and Islands. Winters have been colder with storms and bay scallop catches have generally improved in northern areas.
Blue Crabs it seems do not “like” the same conditions; hurricanes and tropical storm rains can wash Megalops from coves and bays and then flood bay bottoms with built up organic matter from land. This appears to be happening in the Saugatuck River from July 2011 on into Irene and then Sandy (Megalops Report #12, August 2, 2011). This organic matter is under the proper conditions can become sulfide rich and toxic.  Bay scallops and blue crabs can swim so they can both move in areas of high density to low – and in respect to bay scallops act somewhat like marine locusts – consuming enormous quantities of green algae and when food supplies diminish moving into a new cove. The historical fisheries literature is filled with references that talk about sudden appearances of bay scallops and how some coves were filled one day and empty the next. The habitat capacity, perhaps, ran out and they moved on to new areas (this led to some bay scallop jurisdiction conflicts on Cape Cod in the 1950s).  This also explains why blue crabs when faced with toxic sulfide levels simply leave the water. Habitat capacity and quality are huge factors but need to be assessed over time. One New England example is the hard or round Quahog clam.  The Quahog clam is a shellfish that can live to be 80 years (or perhaps more). Although Quahogs usually spawn every year, the big sets or jumps in habitat capacity occur after cold periods with hurricanes. Here coastal energy (read marine soil cultivation) is applied at great depths from waves- turning sulfide rich organic soils over – releasing the sulfides and organic acids into colder well oxygenated seawater that is now basic, slightly alkaline. This is the marine soil that has the highest habitat capacity – for shellfish sets, loose sand, free of sulfuric acid and mixed with estuarine shell; these are the bottoms that produce the “great sets” as they did in Narragansett Bay after the 1938 hurricane and the hurricane seasons of 1954-55.  This was a habitat reversal of huge scale, measured by increased Quahog catches; long dormant bottoms acidic and much filled were re-cultivated and rinsed of acids. The sets two to three years after these hurricanes (soil stabilizes) and the Quahog sets were huge reflected years later in dramatic increases in Quahog harvests.  This was (1950s, 1960s) in a negative NAO period – colder water favored the quahogs. Blue crabs, however, declined during this period. Quahogs were in shallow water coves and bays as well as the deep waters and when it became warmer an Eelgrass/Sapropel habitat soon reduced habitat quality and capacity quahog sets declined, that is why Cape Cod Quahogers despised eelgrass in the 1960s and 1970s; they watched as it “took over” and changed the habitat quality for hard shell clams.  The marine soils now in high heat became acidic, killing clam larvae and then suffocating the adults. Quahog fishers at the time watched as clam habitats were overrun by eelgrass but there was really nothing they could do. Waters warmed in the 1970s, 1980s and 1990s and bay scallops became scarce. However, blue crab prevalence now increased

This was also a blue crab “cycle” a century ago. The Great Heat 1880-1920 brought a similar habitat reversal; acidic bottoms and eelgrass trapping organic matter in high heat and Sapropel destroyed the deep water bay scallop habitats of Narragansett Bay, when the habitat capacity – quality declined so did sets of bay scallops, but blue crabs greatly increased.

The eelgrass Sapropel habitat type extends its coverage during periods of high heat and low energy, cold and energy destroys this habitat and with it eelgrass meadows. The same period saw however a dramatic increase in blue crabs (1880-1920) on as the climate warmed and storm intensity declined – eelgrass flourished and Sapropel deposits grew deep.  Blue crabs as well in these habitats seemed to reverse conditions then and lobster populations fell sharply during the hottest heat waves of the 1890s.  You can only see these influences of climate if you look at the long-term historic fishery statistics. A habitat history, if you will, combines temperature and energy as dominant factors, not pollution or catches.  In fact, catches first appear to be the best indicator of previous habitat quality changes, to energy and temperature, which to my knowledge still remains out of our control, or just natural.
In other words, the ups and downs of a fishery catches largely are beyond our control and there are many examples in the fisheries’ literature; in the 1870s striped bass here were small – 8 pounds and that was a newsworthy catch, but The Great heat (1890s) the Cape and Islands had fishing clubs that specialized fishing for these huge cow stripers. In times of great heat for Striped Bass, they can reach enormous sizes and in times of great cold, they do not.

It is still too early to reflect upon the declines of the more southern blue crab catches for us here in Connecticut, but for the first time I see signs of a large habitat reversal here under way (striped bass kill Black Hall River). Other examples exist, but it’s still too early to show in the catch statistics. The Cape Cod Quahog fishers of the 1970s for example declared war on eelgrass, but it was a habitat war they could not win; it was just getting warmer; now it seems to be getting colder. We might not like the outcome of this one either, an event that could take decades to play out; we may not like the score but still forced to watch the game.

We should know in a year or so if Quahogs set heavy in Long Island Sound deep waters again, monitoring Quahogs sets in Narragansett Bay (if the cold continues) are also important. Another historical indicator for Long island is Great South Bay (NY). After the 1938 and 1954-55 hurricanes, the Quahog sets in Great South Bay were huge, but largely failed in the heat when there were few storms (1974-2004).

Sulfide Kills Possible to Hibernating Blue Crabs
One habitat factor that is still understood is the cycle of Sapropel and its ability to produce sulfide “waters.” The largest component of Sapropel in our area is trapped terrestrial leaves.

Some of our coves (and rivers) have obtained leaves from a newly removed forest canopy – in some places several feet.  This is the Sapropel I wrote about last year.

In shallow areas with eelgrass, this accumulation at first enhances blue crab habitat quality, but when it deepens it “putrefies” and sulfur reducing bacteria consume it creating toxic amounts of sulfide releasing it into the water column or when disturbed by currents or ice. In other words, at the end of its habitat succession the eelgrass/organic meadows became deadly and a source of toxic sulfides.
I am getting a few reports about dead adult blue crabs; although many reference the cold, I do suspect sulfide toxicity.  One of the rivers that has been impacted by leaves is the Saugatuck, so that one is key to watch, but many estuaries that receive raw storm water or street water without recharge basins I believe also obtained huge amounts of organic matter after Irene and Sandy. Spring runoff also carries large quantities of organic matter. It could take years for these organic deposits to “recycle.”

Our trees are back and with a leaf-burning ban in the 1970s, larger amounts of organic oatmeal (leaves) are entering watercourses. The oatmeal first described and known to me by the Quahog fishers of Lewis Bay on Cape Cod (1981) was ground up leaves and dead grass swept into streets and ground up into a pulpy brown “oatmeal” slurry that in heavy rains is washed into bays and coves.  I think everyone has seen this in the fall by road curbs and sometimes filling street basins.  Towns try to keep them cleaned as they themselves become putrefied and contribute to sulfide levels. If the basins are not cleaned they start composting themselves. During The Great Heat, 1880-1920, manure from dairy farms was the source of putrefying organic matter – most of the trees were then cut down for pastures but today it is the renewed forest canopy and paved water courses that deliver organic matter (leaves) to estuarine habitats.  Organic matter can overwhelm habitats changing them. This happened in Europe 1865 to 1915 approximately the same time as our Great Heat- in fact, the climate period we experienced then is remarkably similar to that of the European “Great Stink” a few decades before our last warm period. Here Europe’s rivers filled with organic matter, manure and sewage, putrefied at times, forcing people to flee from the noxious fumes.

It was two biologists, Marsson and Kolkwitz, who developed the pollution index of organic matter and the damage it can cause to environments called The Saprobien System (Sapropel) (See Megalops Reports #8, September 4, 2014, #2, February 2014 and #4, October 7, 2014).  Dick Harris of EarthWatch™ has studied the Saugatuck River for decades and is one of the first researchers to ring the alarm bell for the damage from organic matter, primarily leaves.

The cycle for Sapropel and eelgrass over it has in my opinion helped blue crabs, but in the end, this can cause sulfide kills in high heat. Rhode Island recently had one of these warm water sulfide kills in Greenwich Cove. It just got too hot.

Such events often mark transitions between the cycles, the end of one and beginning of another. Some of the species that seem to be abundant in the transition years are kingfish and weak fish.  The other in (heat) that signals massive habitat quality change is the blue crab, and in cold the bay scallop. Both blue crabs and bay scallops appear in the fisheries history to quickly fill habitat voids – opposite each other in relative abundance.

The 2015 blue crab season for Connecticut following two years of a delayed Megalops set could be an indicator for blue crab populations that increase and decrease in cycles and recorded catches. That is why all observations are important. In a few weeks, the Chesapeake Bay winter dredge survey will be released providing key information on blue crab survival of a very long winter.

Email your blue crab reports to: tim.visel@new-haven.k12.ct.us. All blue crab observations are valuable as we learn more about our blue crab population. Questions? Send me an email.

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

Tuesday, April 28, 2015

Modest Increase in Chesapeake Bay Crab Population

Winter Dredge Total Estimate

Winter Dredge Female Spawn



The numbers are out and the Chesapeake Bay crab population has increased by 38%. Most importantly, the number of spawning age females has increased 47% and the stock is no longer overfished (below the 70 million threshold in the second figure), as it was a year ago.

While this is all good news, the number of spawning age females (estimated to be 101 million this year) is still less than half of the 215 million that would support a productive and sustainable fishery. It will be essential to keep protecting spawning age females for the blue crab recovery to continue.

Click here to go to the Maryland DNR website for more data on the crab population and description of the winter dredge survey that collects the data. The figures above can be found on the DNR website.

You can also read more about the 2015 data in the Baltimore Sun.

Friday, February 20, 2015

Female Blue Crabs Go the Extra Mile

The Washington Post recently ran an article on the status of blue crabs in Chesapeake Bay. The first few paragraphs and a link to the full article are posted below. The Post site has a nice graphic of the blue crab life cycle.



 February 12  
Deep under the cold, dark waters of the Chesapeake Bay, the answer to whether the decimated blue crab population can survive lies buried in mud.
Tens of millions of female crabs are scattered across the floor of the lower bay in southern Virginia, where the estuary pours into the Atlantic Ocean, waiting out winter for one of the most important events in their short lives. When spring comes, they will inch closer to the ocean with billions of eggs.
It’s a critical time because the blue crab population is reeling, facing some of the lowest numbers in history. Officials are desperately hoping that steps taken to protect females last year will allow the fishery to rebound from the edge of disaster. But those efforts are also mired in a debate over the best way to protect the crabs.
As females go, so go blue crabs. Last year, scientists estimated that there were only 68.5 million females old enough to spawn, far below the 215 million that officials say are needed to overcome natural threats such as predators and cold — and human threats such as commercial overfishing — without depleting the population. This year’s count is underway by Maryland and Virginia scientists at 1,500 locations.
The blue crab, Maryland’s state crustacean and a symbol of pride for the region as much as a resource, is more threatened now than at any time since biologists started to record numbers in the late 1940s. Both watermen and state officials are deeply worried about blue crabs’ future. Sixty years ago, the Chesapeake Bay yielded 75 percent of the crabs harvested in the United States; now the withered stock yields about 35 percent, according to a report by the Maryland’s natural resources department.
Some watermen say the steps taken by Virginia, Maryland and the Potomac River Fisheries Commission to rescue crabs after the population’s free fall in 2008 haven’t worked. The states cut the number of females that can be fished by about 30 percent. When the stock rose only to fall hard again last year, Virginia cut the number of females that could be fished by an additional 10 percent during the spawning run.
Smithsonian scientists worry that efforts to save females might produce a serious side effect: overfishing males. When male crabs decline, those remaining mate more often, and sometimes can’t regenerate their sperm supply quickly enough, according to a study by the Smithsonian Environmental Research Center.
Read the rest of the article at the Washington Post by clicking here.

Monday, February 2, 2015

American Indians, Colonists had an Appetite for Crabs

Flickr photo by Rhea C

SmithsonianScience.org has an article about my lab's recent paper on blue crab remains found in Chesapeake Bay archaeological sites.

By John Barrat

Native Americans and America’s early colonists ate many more blue crabs than modern researchers previously thought, according to a team of scientists studying crab remains unearthed at archaeological sites in the Chesapeake Bay area.
Because so very few crab shells have been recovered in archaeological digs in the midAtlantic, anthropologists and others have long assumed that crabs were eaten rarely, if at all, by Native Americans or colonists there.
Now a comprehensive review of 93 archaeological sites across the Chesapeake Bay dating back to 1,200 B.C. has turned up evidence showing quite the opposite.
“I don’t feel confident saying crabs were consistently a dietary staple for Native Americans, but they are found in so many different sites across so many different time periods that we know Native Americans and the colonists were clearly eating them,” says Torben Rick, an anthropologist at the Smithsonian’s National Museum of Natural History. Rick was lead author of a recent paper on the subject in Journal of Archaeological Science.
The researchers found little mention in archaeological studies of the remains of blue crabs in the Chesapeake region, says Matt Ogburn, a crab ecologist at the Smithsonian Environmental Research Center and co-author of the paper. 

“Initially, when we began reviewing Chesapeake sites, we thought we might find 100 or, if lucky, 200 pieces of crab remains and claws to work with. But it turned out there is a lot more out there than we expected,” Ogburn says.

As the paper reveals, by looking into museums and other repositories “we identified and evaluated more than 900 crab remains collected from archaeological sites,” Ogburn adds. The findings ran counter to “the widely held hypothesis that people in the past did not eat crabs,” the scientists say.
“Blue crabs were an important food source for Native Americans, Euro American colonists, and African Americans,” Rick, Ogburn and their co-authors write in their paper. “They are found at a wide variety of site types, including George Washington’s Mount Vernon Estate, a series of plantations and manors in Maryland, a 17th century Native American site, and a 19th-20th century African American domestic site (Sukeek’s Cabin). These crab remains range in age from the early 17th century to the 20th century, suggesting continuous consumption of crabs from prehistoric times and across all major cultural or ethnic groups (Native American, Euro American, African American).”
Why hasn’t previous research found evidence of crabs? The answer is in the shells.  “The blue crab carapace is so fragile and friable that it just doesn’t preserve that well over time,” Rick says.  The shell pieces have often gone unrecognized during archaeological digs.
In this new study, Rick and the other scientists conducted experiments with crab remains showing just how susceptible blue crab shells are to being scattered by scavengers, dissolved and etched by acidic soil, and fragmented into tiny pieces during decomposition and burial. Because the  shells break into such tiny pieces, archaeologists needed special tiny gauge screens to recover the  fragments.
By measuring the excavated the crab parts–primarily pieces of claws and shell parts–the researchers determined that large crabs were more common in the archaeological collections compared to crabs caught in the Chesapeake today.
“Large crabs overall seem to have been quite a bit more common in prehistoric times than they are today,” Rick says. “That’s what we would expect, but it is good to have scientific confirmation that today’s smaller crabs are in part the result of an intensive fishery that removes large crabs from the population.”

Wednesday, January 21, 2015

Discovering the Monster Crabs of the Old Chesapeake

The following article and interview by Tom Pelton at WYPR in Baltimore describes new research from my lab at the Smithsonian Environmental Research Center on ancient blue crabs. Click here for a link to the original WYPR story and podcast of the audio interview. For our paper in the Journal of Archaeological Science, click here.

Discovering the Monster Crabs of the Old Chesapeake

Blue crabs are an important part of the Chesapeake region’s culture, diet, and economy. But crab remains are rare in archeological sites around the Bay. This has led some scientists to believe that Native Americans did not eat the beautiful swimmers that today we find so delicious.
 “What we know about Native Americans ate is based on some historic records, but also on looking at the trash piles that Indians left, mostly on the shoreline of Chesapeake Bay,” said Tuck Hines, Director of the Smithsonian Environmental Research Center. “And the majority of those trash piles are made up of oyster shells. But not much in the way of blue crab remains are generally found in those trash piles or ‘middens.’”
It might make sense that Native Americans did not eat blue crabs.  After all, blue crabs were not a commercially harvested species -- even by European Americans -- until after World War II, when the crab pot was invented as an underwater trap. 
In the century before that, oysters were the most popular food from the Chesapeake.  It the past, highly targeted seafood included terrapin, American shad, and sturgeon -- all of which were over-fished nearly to extinction, until little was left to eat in the Bay except the ornery, edgy blue crabs.
Maybe Native Americans had no reason to mess with blue crabs centuries ago -- because they had so many other, larger morsels of protein they could pluck from the bay with more ease.
The problem with this theory is that records from the 1600’s show that Native Americans were interested in blue crabs as a source of food.
“If you look back at the records of when colonists arrived, and negotiated fishing peace treaties, including hunting and fishing rights in the Chesapeake Bay region, those descriptions and those treaties including rights for crabbing for finfish as well as a collection of oysters,” Hines said.
If Native Americas were negotiating for crabbing rights, why are crab shells missing from Indian archeological sites, while oyster shells and even fish bones are common?  To solve  the mystery, Hines and colleagues at the Smithsonian re-examined old trash piles around the Bay using a new technique.  They used sieves with a very fine mesh.
Scrutinizing historic sites more closely with these sieves, the researchers discovered  tiny fragments  of crab shells in 93 different Native American refuse heaps  around the Bay, some dating back more than 3,000 years, according to an article that Hines and colleagues published last month in the Journal of Archeological Science titled, “Archaeology, Taphonomy, and Historical Ecology of Chesapeake Bay Blue Crabs.”  His co-authors are Torben Rick, Matthew Ogburn, Margaret Kramer, Sean McCanty, Leslie Reeder-Myers  and Henry M. Miller.
Their conclusion was:  Native Americans, in fact, ate plenty of crabs.  But the shells broke down over the centuries, perhaps in part because of acid rain from coal fired power plant pollution in the 20th century.
“The main part of the blue crab that carries forward in these middens are the tips of the claws, which are the most calcified hard part of the crabs,” Hines said.
Analyzing the size of tips of the crab claws they found, the scientists extrapolated how large the crabs must have been. They concluded the crabs caught by Native Americans were much larger than they are now – some twice as large as the typical five inch crab caught today.
“We’ve found middens that contain crabs as large as 10 inches, which is a quite large crab,” Hines said.  “So that’s interesting.”
These giant crabs were not a different species. They just lived longer, because they faced less fishing pressure.  Crabs today typically do not live more than two or three years because most are quickly scooped up by watermen using dredges or pots. Every year, about half of all the adult crabs in the Chesapeake Bay are caught.  But back in Native American times, maybe one percent of blue crabs were harvested every year by people using baited lines and dip nets.
So blue crabs lived as much as twice as long, and grew up to twice as big. Imagine those meaty crab feasts on the Old Chesapeake Bay, with those monster crabs.
The lesson we can learn today from these ancient garbage heaps is that we can have more of what we love if we take less.
....................................
(Photo at top of Tuck Hines and blue crab from Smithsonian Environmental Research Center)