The following article and interview by Tom Pelton at WYPR in Baltimore (originally posted here in January) 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.
Tuesday, June 30, 2015
Monday, June 15, 2015
From Tim Visel at The Search for Megalops:
Thanks for your continued interest – email@example.com
The Search for Megalops
Special Notice # 1 – Blue Crab Winter Kill
- Habitat Transition Now Apparent –
Blue Crab Research in Long Island Sound
You do not need to be a Scientist to report!
(IMEP Habitat History Newsletters can be found indexed by date on the
BlueCrab.Info™ website: Fishing, eeling and oystering thread)
and CtFishtalk.com™-Salt Water Reports and
Tim Visel, The Sound School
June 15, 2015
Blue Crab Winter Kill
This spring has been somewhat discouraging for blue crabbers along the Atlantic Coast – first as an indication that a large amount of our over wintering blue crabs have perished and second a weak showing in the 2014 Megalops set. First winter kill reports from the Chesapeake Bay report as much as 30% have died but along our coast 60% or more from early reports. The long cold winter is now suspected to have allowed sulfide levels to rise especially under ice – to those lethal to Blue Crabs (and perhaps over wintering Terrapins as well). Winter kills of fish, oysters, blue crabs and turtles are not new but indications of rapid habitat change. Fish trapped in deep holes under ice can be killed from sulfide – the by product of organic matter digestion, coastal salt ponds appear to be the most vulnerable (and unfortunately one of the few habitat refuges for blue crabs) in our area. For example the Black Hall River in Old Lyme is now suspected if a sulfide fish kill last February (2014) when ice formed and about 1,000 striped bass were killed. Conversations with area blue crabbers mentioned previous winter fish kills of stripers– not as large but accompanied by the smell of sulfur. The most susceptible winter kill areas are small coves and bays with long “weak” connections to the Sound – frequently described as “poorly flushed.” Such areas tend to collect the deepest organic deposits – when in high heat these areas undergo ammonia/sulfide generation.
In the scientific literature such deposits are mentioned as “fine muds – low oxygen sulfuric oozes” but many fishers call it Black Mayonnaise (Sapropel). A cold winter with many powerful storms – turns over this marine compost much like a huge shovel releasing tremendous amounts of nutrients for spring algal blooms. Areas that once held deep soft deposits of organic matter undergoing sulfate digestion (sulfur reducing bacteria) can release a sulfuric acid wash with a dramatic pH drop – increasing toxic impacts. These kills are more frequently associated with black waters following storm events. In time coastal storms over a period of years may transition sulfuric oozes (black in our area from iron) to sandy shelly brown mixtures with some mud but loose and not sticky. It is these “recultivated” marine soils that can sustain heavy sets of shellfish such as the Long Island Sound and Narragansett Bay great Quahog sets in the 1950s and 1960s (cooler period more storms).
Habitat Transition -
A recent shell hash seagull survey (June 1) at the Niantic River state launching ramp (parking lot) yielded about 30% of dropped shells were in fact bay scallops (sea gulls don’t waste their time dropping empty shells to crack so this is a quick way of determining locally what’s around) and 60% were quahogs – the rest mussel, oysters and soft clam. Around January 20th bay scallops moved into the lower reaches of eastern CT Rivers. This is another indication of a major habitat transition – the return of bay scallops to Connecticut. Habitat transitions are usually marked by sudden climate and energy shifts and the increased occurrences of multi species winter die offs.
Habitat transitions in the historical literature are not quick they in the past took decades and a return of warm winters and few storms would help the blue crabs – last winter obviously did not.
Any reports of Blue Crabs (dead or alive) would be a help – all observations are important.
From Tim Visel at The Search for Megalops:
Megalops Report #3
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
May 30th, 2015
- An Early 2015 Season Forecast
- What to Expect for The 2015 Blue Crab Year
- The Western CT Event in 2011
Follow Megalops reports on the Blue Crab Info™ Northeast Crabbing Resources. IMEP habitat reports can also be found on the Blue Crab Forum’s™ “fishing, eeling and oystering” thread. Thanks also to Connecticut Fish Talk ™ for including Megalops Reports under the Saltwater Reports thread and the Blue Crab Blogspot™, for posting all Megalops Reports.
An Early 2015 Season Forecast
Several crabbers have asked about a 2015 season forecast and if this upcoming blue crab season will be better than 2014. It’s early but some indicators point to another very slow start. The excellent 2010-2012 seasons had reports of 1-inch crabs on the open beach fronts, on shellfish beds and in shallows along miles of the Connecticut coastline. That was in March, April and springs were warm – (Megalops report #2 April 23rd 2012). The past two years small blue crabs appeared in September – October in deeper waters offshore. The evidence was reported by Black Sea Bass fishers the past two years (Megalops report #6 October 24, 2013) (Megalops report #4 October 9, 2013). This was in deep water and far from the marshes – the better habitats. It is the creeks and head waters that provide the best protection until spring.
Recent conversations appear that the Megalops set last fall was larger than I thought and underestimated the predation by Black Sea Bass. Reports now indicate that nickel size blue crabs extended from central Long Island Sound to eastern Long Island New York to the west of Block Island to the Rhode Island salt ponds. The set was most likely stretched to tens of miles than a few miles concentrated in central Long Island Sound. These small crabs were in deep water and miles from shore. They must have suffered tremendous predation (as evidenced by Black Sea Bass catches) and faced a huge pool of potential predators. If any of these crabs made it to shore they had the cold and storms that followed. The presence of small crabs early along the coast would have been a good sign. But to date such coastal reports have be slow to materialize.
Large crabs showed in the Connecticut River to Milford in 2012 (Megalops #3 June 19, 2012) even before the official season opened. Winters were mild almost warm then and relatively quiet. That appears to be the opposite now, although our winter was on track to be mild until December 20th (I had blooming dandelions the middle of December) then it turned colder and then proceeded to break snowfall records.
The cold winter took a heavy toll of the Chesapeake Bay population to our south as “winter kills” reported to be 30% and I would expect the same here – perhaps more. The worst winter kill ever recorded was following the 1976-77 winter there and reported to have killed 48% and the shallow waters suffered the worst (Krantz GE 1977).
The last indicator I look at is the distribution of the run last year, but reflecting upon observations, most of the crabs were legal size (except for the Clinton Harbor region) and very few sublegal. In 2010 and 2011 at times the dozens of small crabs stripped bait from hooks in minutes in Clinton Harbor (Megalops report #11 July 27, 2011). Although this made for some frustrated rod and reel fishers it was a terrific sign to the blue crabbers and large number of small crabs were “coming up.” Last year I observed only a few small crabs, most crabs caught were adults – giving the appearance the fishery was by sustained by previous year classes which can only last so long.
Our fishery seems to be existing off the 2012 and 2011 perhaps even 2010 sets but that will soon “run out.” The absence of a widespread set is a negative sign for the season, but 2011 blue crab year also started slow. The next indication would be a set by July 1st. Small crabs 1 to 2 inches depending upon water temperature could shed to legal size by the fall – this season. The source of this set would most likely be a set carried north on the gulf stream, which depends upon wind shear and warm water rings that can spin off and hit eastern Long Island. (They also bring us the interesting tropical fish from time to time).
Many years ago researchers in the Cape Cod area came to the same conclusion that such blue crab larvae did in all likelihood originate from areas further south and were transported into salt ponds on the Cape and Islands. A 2004 report has this section “The Megalops stage lasts 6 to 20 days. It is likely that the crabs we recruit while a summer inlet is open originated from other ponds possibly quite remote from the Vineyard. The combination of prevailing southwest winds, northward flowing gulf stream as well as eddies and gyres that break loose from the stream could transport them from several hundred miles away during the 50 day plus or minus planktonic stage” (Blue Crab Ecology Review and Discussion Regarding Tisbury Great Pond, March 2004, William M. Wilcox, Martha’s Vineyard Commission). In a Rhode Island blue crab study Jeffries (1966 Internal Conditions Of a Diminishing Blue Crab Population) reported that after high producing years 1910-1915 in Narragansett Bay when it was possible to catch a bushel with one line on a morning tide crabs, had retreated to only two salt ponds Charlestown and Greenhill. The last appearance of large numbers of blue crabs happened in Pt Judith Pond in 1947. Reports during the same period in the Westport River, Buzzards Bay mention the same situation.
A Study Of The Marine Resources of the Westport River, Massachusetts Monograph Series 1968 John D. Fiske et all – (60 pages) has this comment.
“The Westport River is one of few regions the South Shore of Massachusetts where blue claw crabs (Callinectes sapidus) still occur in numbers sufficient to supply a family fishery – especially at Hix Bridge pg 39. The Blue Crab is a species which was formerly abundant on the South Shore but has been declining in numbers for at least the last decade. The cause of the decline of the crab in our waters is unknown.”
And on the Cape generally the same observation – A Study of the Marine Resources of Pleasant Bay – Chatham Orleans Fiske et al (1967) – pg 48 has this comment,
“It should be noted that during the 12 month sampling period biologists did not capture or observe one blue claw crab in the estuary (Pleasant Bay). During the course of interviews, many local fishermen expressed concern over the disappearance of blue claw crabs in the bay. In recent years, there have been similar reports from many areas along the southern shore of Massachusetts. Until recently many bays and tidal rivers supported substantial family fishing for these edible crabs. Since this species appears to be in marked declining, specific investigation should be conducted to find the case of this decline and to determined possible methods of rehabilitating the crab stocks,” pg 48.
The later series never reveals any information pertaining to the Blue Crab – and this period was the height of the negative NAO period, cooler and many storms – when the warmth returned to the Cape in the 1980s – the Blue Crab also returned.
A Habitat History is Important
By the time the 1960s occurred on Cape Cod or the Massachusetts south shore few could recall that in the 1890s the New Bedford Buzzards Bay area was once the “capital” for the Massachusetts commercial blue crab fishery. The causative factor for the southern New England Blue Crab population decline was in fact temperature related to climate patterns – cold. The cool temperatures most likely delayed the Megalops set as we are seeing now. Storms may have changed habitat types removing the Sapropel/eelgrass and leaving cobblestone/kelp 1950-1965. This period is now noted for its negative NAO climate pattern.
Dr. Willard Van Engel (1985 laws regulations and environmental factors relating to the Blue Crab 1880-1940 #347 VIMS VSG 99-07) a noted blue crab researcher in southern areas looked at environmental factors and hoped that an extreme event would help signal why blue crab catches fluctuate, and comments on page 47, “Extreme variations in those factors (environmental) are more likely associated with extremes in year class strength and fishing success. Only when accurate catch and landing data are available for times proceeding and succeeding the occurrence of any of those events can the degree of association be determined.”
Southern New England has again experienced a surge in blue crab abundance – following decades of heat, followed by a sharp reversal in winter severity – cold and many Nor’easters. We may now have in our area the extreme example that Dr. Van Engel long searched for.
What to look for is a widespread set of 1 inch crabs along the shore in shellfish beds by July – any sets much later than that would be good sign for 2016. This year head to those salt pond habitats they may have larger numbers of crabs that were protected from heavy winter storms.
See you at the Docks.
Tim Visel – (Blue Chip)
- What to Expect for the 2015 Blue Crab Year
I would like to respond to the many comments and questions about disappointing blue crab catches here last summer in Connecticut and the prospects for this season. For many western blue crabbers, the crabs “never arrived”. [Still no crabs.] Last year this of course is in stark contrast to previous summers and should we now be looking for a habitat failure for blue crabs for this year? I am reluctant to confirm a habitat failure, but ready to share what research information I have about cyclic habitat reversals here. I continue to appreciate the opportunity to reach so many crabbers on the Blue Crab Info™ website.
First of all, I hope that the remaining “Megalops Reporters” will continue to look for crabs, even reports of dead crabs or no crabs observed are important. I appreciate all the observations to date and no matter how brief, they add to our knowledge here of blue crabs in southern New England. As for the lackluster blue crab year (2014), so many crabbers have asked, “what happened?” and “why?” in response to disappointing catches in 2014. Almost immediately overfishing comes to mind, and I respond with a firm “No.” Our gear here is so limiting most of the blue crabs are not caught and face a very uncertain future in the deeper predator filled Long Island Sound. I did see crabs wasted, however (Megalops, August 2012), but overfishing did not occur in my view. I offer these explanations for last year’s sudden decline.
1) Increase in Coastal Energy and Rains– A series of coastal storms, hurricanes and Nor’easters- small crabs were just washed out of hibernating areas or cast loose by bottom disturbance (Notable periods in the 1950s and 1960s.) It wasn’t sudden if you looked at the Megalops sets after 2012. Huge amounts of organic matter also entered our estuaries after 2011. [This can impact blooms of algae by releasing huge amounts of nitrogen compost compounds similar to a fall overturn in lakes.]
2) Decrease in Temperature 2004 onward our winters have on average been colder and longer upstate New York last year had snow in May and we had some in October. Colder winters generally over time have not resulted in large blue crab catches, only smaller. A series of cold winters in our area appear to have the lowest landing impacts.
3) Extreme Heat – As our summers warmed, they have perhaps become “too hot” driving low oxygen conditions to that of sulfide toxicity – Sulfate reduction that took any remaining oxygen while producing toxic sulfide compounds in organic deposits: the so-called Black Water deaths of the past century, crabs would leave very warm shallows and head to the deeper, cooler, more saline pockets, that is what happened in 2011 and to a lesser extent in 2012 (Megalops #6, July 19, 2012, Megalops # 7, August 9, 2012).
4) Failed Megalops Sets – Predators- A series of native Megalops sets that just came too late; did not reach the salt ponds or marshes in time to be consumed in deeper waters by predators (Megalops #6, 2013) and (Megalops #4, 2014) Black Sea Bass was the species reported to be consuming small blue crabs in deeper waters.
Any or all of these factors contribute to low blue crab numbers. One of the things you see is just before a habitat failure catches actually increase from compression this would happen just before some of the largest fish kills of the last century. This is a frequent post low oxygen events (called Jubilees down south) crabs attempt to flee low oxygen by walking ashore followed quickly by fish kills and then sulfide toxicity (the rotten egg smells mentioned in many of the last century reports). Huge fish kills often follow crab kills, at Niantic Bay in the late 1970s (personal communication B. Porter, 1985) the most infamous Black Water death event in Moriches Bay, New York in July and August of 1917. Winter Flounder trapped in the Bay during high heat died in a low-oxygen sulfide event.
Other sulfide events are associated with noxious sulfide fumes staining houses (Mackenzie NOAA 1998) and on Narrow River (sulfide levels larger than the Black Sea, Gaines 1979) Rhode Island (and personal observations) of acidic fog droplets at Niantic Bay (personal communication, B. Porter, 1985) are also in the historical literature. The sulfur cycle has a role in wintertime survival as well.
What to look for—most organic filled bottoms can still contain blue crabs at higher tides (higher oxygen). At low tides, respiration can lower oxygen levels; this seems to be a natural tidal response – (see Tom’s Creek Study of Habitat Succession). In these times bottoms organics rot in heat and release gas bubbles at slack tides as the gas continues to be emit “bad” smells – look for a series of gas bubbles coming to the surface (Megalops #3, July 23, 2013). When crabbers can see bubbles, crabbing activity drops off measurably, crabs may hook up but let go immediately, an incoming tide bringing fresh oxygen, cooler water into these warm shallow areas and crabbing usually improves. In Central CT, low tide crabbing is often very poor on these very hot days.
Rivers often contain such organic deposits and crabbers on the DEEP Fishing Pier at Baldwin Bridge (July 20, 2013) were amazed to see streams of bubbles coming to the surface. They had never really noticed them before. This is a negative habitat sign, as well as hard bottoms sand and shelly before now covered with feet of Sapropel after a heavy rain. And the gas (bubbles) – in cold waters (more oxygen) tends to be methane, and in warm weather, (less oxygen) would be hydrogen sulfide gas, sulfur smelling and the rotten egg smell mentioned so many times in the historical fisheries literature. (The nighttime marsh smells of a very hot August summer is also the same process.) At higher tides and places with currents, these gas bubbles are hard to see and crabbing is generally better. At high tides when the salt wedge is strong, the best crabbing occurs; (The DEEP Baldwin Bridge Pier has allowed hundreds of families to come to the shore and catch blue crabs; it is quite a facility for fishers).
A series of coves that has incredible amounts of Sapropel (mostly from acidic oak and maple leaves) are North Cove, Middle Cove and South Cove in Essex. On July 20, 2014 low water the gas bubbles from organic deposits (foot of Park behind Main Street Essex Post Office) was continuous in all directions. Kayakers often report smells from these pockets of gas (sulfur) when transversing Sapropel deposits on days with little wind, similar to the “marsh gas reports” of the last century.
5) Other concerns- West Nile treatments, (see report Pesticides and Blue Crabs, July 24, 2012) salinity shock from heavy rains, low oxygen events and overfishing. I do not believe in any way it is overfishing here we have good laws and I found it to be impossible to overfish an area when the run and distribution of post Megalops was so even. In early July 2011 West Nile treatments certainly didn’t help, but it is my understanding that such treatments have been now sharply curtailed / controlled. Salinity shock (too much rain) that is mentioned in the historical literature often and I have seen a massive die-off of 2” crabs in the Connecticut River following a heavy rain. But some of the Megalops densest sets have come from salt ponds in the Fairfield- Western CT region and perhaps not as susceptible to rainfall events, (Perry Mill Pond). Low oxygen is possible but we should have seen massive fish kills also, but we didn’t, at least not to the extent found in the historical literature (The Great Narragansett Fish Kill of 1898).
Instead, I believe that massive amounts of organic matter have been washed compliments of recent storms (Irene, Lee and Sandy), into the lower reaches of estuaries in western CT and rotted, releasing sulfur rich Sapropel into the water column or producing hydrogen sulfide toxicity is not great for blue crabs.
Studies regarding sulfate and sulfide compounds toxicity to blue crabs find them to be extremely sulfide sensitive and result in “DIP”, “death in place” unable to escape and die almost instantaneously. If you refer to a blue crab report #12, August 2, 2011, see “western crabbers alarmed at dead crabs following intense heat and street water runoff event”. It appears that one event reduced blue crab catches in certain areas by half in just three days.
One of the limitations of compiling an environmental habitat history is that climate and storm impacts are usually reported and measured to impacts upon shore infrastructure and “us” – only - not habitat quality. Badly eroded beaches, destroyed homes or collapsed seawalls garner attention; you can see this by the federal and state response to the destruction of the 1950s and 1960s with flood and erosion control legislation. After federal authorization many coastal communities created flood and erosion control boards or committees. In the 1980s and 1990s as energy erosion events declined, they were often disbanded. High heat and the lack of energy (anoxia) was the news events for Long Island Sound in the 1990s. Very little evidence or research was being conducted about changes to finfish and shellfish habitats or over the long-term changes in them.
One of the few consistent remarks in the records of the Great New England Hurricane of 1938 was on sandy stretches hard shell clams were often cast upon heaps in the Southern New England. After the storm efforts focused upon the human tragedy, certainly not the habitat impacts to blue crabs. I don’t think blue crab habitat quality was on anyone’s’ radar after the 1938 hurricane. But substantial habitat changes were ahead for New England the hurricane nearly wiped out the Connecticut and Rhode Island oyster industry and shortly later had the greatest hard clam quahog sets in a half a century. Thousands of acres of eelgrass were gone and so were the habitats to sustain them, sometimes forever.
The warm period 1880-1920 a century ago was marked by extremes, hot in the summer and then mild in the winter, it wasn’t’ until 1931 that warm spells and quick freezes would kill large numbers of blue crabs in the Chesapeake Bay (Van Engel). The Chesapeake Bay would be the region to notice the difference between our temperature to water temperatures with 1931 being the key in which energy increased and temperatures cooled (Van Engel). 1931-1932 is mentioned in many reports as a key year for habitat change. This appears to the transition period between the hot and quiet 1890s and the storm-filled, colder 1950s.
Crab losses have been noted during storms and the Chesapeake Bay area was hit by severe storms of 1878, 1888, 1897, 1933 and 1936. At certain times extremely hot temperatures have created jubilees of low oxygen/sulfide toxicity and cold “winter kill” largely sulfide or starvation. Habitats were relatively stable until about 1944. The habitats were subject to a series of powerful hurricanes. The “story” of habitat changes in New England is much harder to determine because blue crabs are considered periodic mysterious visitors. The state of Connecticut Fisheries Management Plan of 1985 for example only has three paragraphs or so for blue crabbing but three pages for lobsters.
Others have mentioned disease and that certainly deserves a close look, but I do not find reference to diseases that would eliminate all year class sizes, 5 and up, 3 to 4, 1 to 2 and Megalops all at once and only impacting only the western third of the state. If anything could be said about the 2011 crab year was masses of blue crabs were leaving the Housatonic River region and moving east, something in the water (sulfide?) could have triggered movements before and after the July 2011 heavy rainfall. The reports of night time movements of crabs include striped bass fishers suddenly surrounded “by schools” of blue crabs. References of “ocean schools” of crabs can be found in the historical literature.
Western Blue Crabs Population Declined in Three Days - 2011
In 2011, western Connecticut was hit by immense rainfall and intense heat (Western CT Habitat Failure, August 2011, IMEP #7, September 30, 2014 – Fishing, Eeling and oystering thread). The season started slow – after the spectacular 2010 season, but then soared, and then by August catches declined by half (Megalops Report #12, August 2, 2011).
Did the increase in storms also wash Sapropel and eelgrass from coastal areas? I believe they did, 50 years ago as eelgrass populations declined so did the blue crab. The blue crab might have a better habitat association to light (not extreme) Sapropel /eelgrass organic deposits, I suspect that this habitat type to be related to storm energy and temperature, while cold (winter sulfide starvation) and energy (dislocation burial) may be negative in high heat while energy storms might be just as negative in very cold. George McNeil, a retired oyster grower who lived in Clinton once told me decades ago that winter Nor’easters could deposit as much as three feet of leaves over Hammonasset River oyster beds in a single storm and they would need to be raked off by March 15 or the oysters would suffocate. Dead oysters killed by suffocation were termed “stools” adult shells still paired even dead but empty. One can only imagine how much dead leaves and organic matter have been brought down our rivers and streams by Irene and Sandy. The rain effects in 2011 reduced crab catches by half in three days, with reports of dead crabs and brown water. Productive blue crab habitats in western Connecticut have never recovered from these heavy rains (from reports).
Connecticut has most likely experienced these dramatic habitat reversals before as the previous four sections indicate – each relates to a research area that can provide us with information ahead about the rise of blue crabs have after 1998- and now a possible decline.
A nearly complete inventory of all the Megalops reports can be found on the Blue Crab.info forum website, the global moderator for the site has made bulletin board space for them- see “Blue Chip” reports *under Northeast Crabbing Resources) Megalops reports. All the 2011 reports are now compiled on a Bulletin Board (Northeast Crabbing Resources) and the fishing, eeling and oystering thread on Blue Crab Forum™.
All the 2012 reports (except specialized reports) can be found on the Northeast Regional Crabbing – crabbing resources section also by date).
The 2013 reports are compiled by date and the first report 2013 is also on the current bulletin board. I am very grateful to the Blue Crab Forum™ for continuing to archive these reports as Connecticut crabbers looking into the apparent die-off of Western CT crabs. The run distribution and history of these pre-July 2011 reports are very important to compare to today.
I hope that this report the third this year, will be of interest to Blue Crabbers and researchers investigating Long Island Sound fishing resources.
Again my thanks to these few remaining 2011 western crabbers who continue to email me their blue crab observations – let me know if blue crabs “never showed”, that observation is important also. Every blue crab observation is important (perhaps more so) in western CT and many crabbers wait for some good news about large numbers of small crabs.
Email your blue crab reports to: firstname.lastname@example.org. 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 email@example.com.
The Sound School is Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.
Monday, May 11, 2015
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.
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™
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.
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 :
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: firstname.lastname@example.org. 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 email@example.com
The Sound School is a Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.