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PostPosted: Wed Jul 19, 2017 10:51 am    Post subject: Marine Soil Experiments Clam Growth & Setting 1890-1930 Reply with quote

IMEP #59-A
Marine Soil Experiments Clam Growth and Setting Habitats – 1890-1930
The Use of Natural Quahog and Steamer Soft Shell Clam Seed
Areas for Aquaculture
Nantucket, Jamaica Bay and Quahog Seed Transplants of the Last Century
July 2016
Habitat Information for Fishers and Fishery Area Managers
“Understanding Science Though History”
(IMEP History Newsletters can be found indexed by date – Title on the BlueCrab.info™ website: Fishing, Eeling and Oystering thread) and on Connecticut Fish Talk™ (See Saltwater Reports thread)

This is a two part report – 59-A and 59-B.

Readers should review IMEP #58 January 20, 2016 for a better understanding of this report. This paper includes an 1890 survey of Long Island Sound containing an early description of Sapropel bottoms. Climate factors do influence the capacity of marine soils to sustain shellfish sets in shallow waters.


Floods can create soil instability as exampled by agriculture soils under water for a few days once dry again they need time to repopulate good bacteria and rebuild soil functions. Constant soil cultivation (energy) also deserves a habitat look – many current shellfish management plans mention zone rotation and seed shellfish surveys. This makes for a good shellfish management practice as it allows marine soils to stabilize. Constant soil instability either on land or beneath shallow estuarine waters is disruptive to organized culture (forest fires or flood/hurricanes). It is both natural however to have fires storms and floods. Change the bacterial makeup of soils and it alters the biological processes in them. Shellfish recruitment into marine soils is still an area of unknown.

What makes some soils better than others or why shellfish sets change in them so rapidly is still under review. Natural seed beds though raises an interesting policy dilemma that is only size here ensures a constant harvest and is a good thing but often not as grow out in heavy set areas where mortalities can be total. There just not enough or space or food for all the clams. Habitat quality is often a factor as well. Shallow sets subject to freezing is often cited historical example. It is here that local shellfish management agencies should invest in some survey resources. Researching and mapping areas that produced excellent oyster setting beds was the foundation of the oyster culture industry. Identification of natural hard clam seed beds could produce thousands of bushels of seed while producing few marketable size adults is also noted in the historic literature. The “problem” of heavy sets in these soils is well documented in the historical fisheries literature – if provided sufficient space to grow (as with the oyster industrial practices of thinning cultivating heavy oyster sets on cultch) these oyster natural seed beds could sustain immense recreational and commercial shellfisheries. The same could be true for hard and soft shell clams. Understanding the history of seed beds could provide important clues for Aquaculture.

Capstone questions –
1. Can clam farmers test marine soils for Quahog growth characteristics
2. Do we know enough about marine soils to map clam habitat setting preference?
3. Does the existence or presence of Sapropel restrict soft shell clam sets?
4. Can we rebuild and culture natural clam seed beds for Mya or Mercenaria?

Students interested in this historical research should complete a FFA nonexperimental SAE form available in the aquaculture office.

CTE standards include: Aquaculture #6, #9 and Natural Resources #4, #9, #14

Introduction Natures Natural Seed Beds

Against the energy from storms or the impacts of temperature upon coastal fish and shellfish habitats, our fisheries management policies sometimes pale. They may help start seafood cycles or act to extend them, but cannot overcome massive habitat change. That is why when faced with habitat failures, aquaculture often came into existence based upon the ability to secure sources of high quality seed - the foundation of modern agriculture. This is especially true with clam culture, the grain pore size and pH of marine soils has huge implications on productivity. Certain soils were made more suitable by cultivation (Fisheries and Oceans Canada, June 16, 1997) (Cultivating sea bottoms for clam planting).

Fisheries management policies based upon size has been less than a complete success for both finfish and shellfish populations when examined overtime. Shellfish management the most resembles terrestrial agriculture from its dependence upon soil, pH and soil “health” (and yes, marine soils have healthy and unhealthy aspects) and access to seed. Time does have an impact as well. Marine habitats succeed over time, much slower than land habitat succession; it can also start faster. The historical fisheries literature is filled with a sudden abundance of seafood - sometimes it was a shock-not fully appreciating perhaps the habitat changes over time that made such populations now possible. That introduces the ability to provide energy into marine soils to help create better habitat conditions – that requires work, “energy” into them.

One of the factors not often considered in the historic oyster fisheries is the energy expended in the capture fisheries that itself extends habitat succession, similar to lawn care. The rapid expansion of the oyster industry for example in the 1880s to 1890s was made possible in part by the increase of both marine power systems and technology, larger and more powerful dredge vessels. Acres of estuarine bottoms were cultivated, cleared off loose organic matter (Sapropel) and kept clear from accumulating organic matter on settling beds (termed “stirring: and to represent natural energy from clearing). Energy can both start and end habitat succession and as much as we highlight on the negative aspects of energy and bottom “disturbance” habitats are created and maintained by energy. I often us the lawn care example of energy (the lawn mower) used in maintaining a certain habitat value or type of lawn. Remove the energy (lawn mowing) and habitats will quickly succeed into something else. In the marine environment, buffered against extreme change by the sea itself - habitat succession takes much longer, which has allowed a bias to occur; we see the damage from hurricanes, but cannot see the habitat changes below the tide lines. It can also occur much faster as well - that is often in the historical fisheries literature as a sudden “new” find of seafood.

Mr. Hammond, the retired oyster planter on Cape Cod called it our “bias of perspective.” We just didn’t have the lifespan or ability to observe many marine cycles as well as those that followed forest fires. That was because the life spans of shellfish, especially quahogs, were so long. To follow the cycles he thought oysters were the better species to research, but even that was problematic. He was using fish catch statistics as a way to gauge habitat quality, combining it with his observations and weather/climate conditions on Cape Cod. By 1981 he had noticed a build up of a black greasy deposit, he called humus that was killing off clams in shallow waters.

To Mr. Hammond, New England cycles of seafood most likely had been in this situation before many times before. With New England climate cycles, it would be natural to see such seafood cycles and that small bays and cores from them have a habitat history. I mention this again as it directly relates to the quahog fishery and the sudden “shock” of the extensive clam bed “discovered” off Nantucket in 1913 (readers should also read IMEP #5Cool. On NOAA bulletins in the 1970s, the area between Great Point and Tuckernuck Pond were still listed as the “Quahog Grounds” (NOAA Angler’s Guide, Section II, Nantucket Shoals to Long Island Sound, 1974).

The Portland Gale of 1898 is suspected of cultivating (by wave and storm action) a large, shallow section of Nantucket Sound. The storm, immensely destructive to shipping and coastal ports with much loss of life, had to have energy impacts into the bottom and alter the soil characteristics in them. In the fisheries’ records, you do see larger quahog sets after storms in colder water years later followed an increase in clam landings (Narragansett Bay, R.I.). It is also suggested that such intense soil cultivation could have changed the structure of benthic predators – it could have eliminated some clam predator prey species as well. (Cycle Mackenzie et al Marine Fisheries Review part 1, 2002).

Heat Waves Can Change Coastal Soils

Quahogs in southern New England had died out by the 1890s. Soil conditions had likely changed to Sapropel-eelgrass in the south and sulfur reduction had made them likely acidic and put out at times a sulfur smell. Theses soils likely now had toxic sulfide pH qualities. Cooler areas in the north, like Nantucket, likely held out (habitat quality) longer and in a short time seed quahogs were planted (bedded) in the southern areas, especially Jamaica Bay near a burgeoning market, New York City, just a scant few miles away. It is thought that these nearshore soils had failed and with them the fishery. Belding 1912 mentions that for soft shell clams “such a soil indicates a lack of water circulation with in the soil itself as indicated by the foul odor of the lower layers of soil, the presence of hydrogen sulfide, decaying matter dead eelgrass, shells and worms. If such a soil could be opened up by deep ploughing or resurfaced with fresh soil to sufficient depth it would probably favor the growth of the clam” pg 21.

At first the supplies of Nantucket quahogs I suspect was a surprise to local fishers and there was so much seed, no one really complained. But in time, sizes would diminish as accumulated adults were caught up, giving the appearance of over-harvesting, but not including the positive cultivation aspects of the harvesting practices themselves, the cultivation, marine soil improvement aspects. In the quahog fisheries, you see this and time after time in the other historical shellfisheries’’ and in research as well, the most productive areas were the ones worked “really hard.” One account from the Tauton River in the oyster fishery (US Fish Commission (1880s) describes a lease holder failing to renew his oyster lease felt determined to leave nothing behind for the successor. He scraped and dredged the bottom bare all fall, leaving nothing of value, but was able at the last possible time to renew his lease in the spring and found triple the seed oyster set. He calculated that a thorough scraping “had done the bottom some good;” it had.

The most thorough “scraping” of the bottom occurs during hurricanes and although the 1898 storm is called The Portland Gale, it was a hurricane in November, it was beyond the “normal” hurricane season because the waters were very warm then from unprecedented heat waves all summer long (New England would later suffer a “Ice Famine” in 1899). Lakes and ponds were so warm then, ice did not form, so often our calendar does not make or can define nature).

The bottom cultivation event set into place soil conditions that likely favored the quahog. Immense sets in a defined area occurred and the fishery soon followed. Was this bed sustainable over time? No, because the same factors that created it would in time destroy it - habitat succession. Was this the fault of fishers? No. Despite many reports to the contrary, fishers like farmers cannot control climate factors which are connected to habitat quality.

This is where fishery management often steps in, and I suspect that in 1928 or 1929 as catches declined, the harvest of seed quahogs was stopped (In the absence of Nantucket shellfish records, I am generally relying from information on other areas’ accounts mostly Belding) believing this was a good thing to do - it was not. This management response often occurs it is much easier (and possible) to look at the fishing for increasing yields, but often they are not connected. In fact for marine soils limited cultivation is beneficial and not a detriment as is often reported. Similar to terrestrial soils – soil compaction possibly decreases and limit the bacterial benefits. These soils need oxygen and cultivation creates the soil “pore” space to exchange it. Therefore in time soils can “improve” and “decline” in terms of capacity to sustain shellfish sets is related to soil circulation as Belding described in Massachusetts.

Dr. Belding himself weights in on the practice of bedding small seed quahogs writing in 1920 “that the Eastham Orleans and Wellfleet Selectmen may give for a period if not over two years, under such conditions as they may deem proper, to any inhabitant of the respective towns, licenses to bed quahogs in any waters, flats or creeks where there is no natural bed, not covering more than 75 feet square in area, and not impairing the private rights of any person or materially obstructing any navigable waters. The object of this law was to make possible the advantage of a favorable market, as the quahauger could “bed” this catch until the market and the price went up, otherwise he would be compelled to ship at a low figure. Undoubtedly the originators of this act did not forsee that in this way they had taken the first step toward quahog farming, as the success of bedding quahogs has demonstrated to the quahaugers of this section (of Cape Cod) the practical benefits which would be delivered from quahaug culture.”

The truth of matter was according to Mr. Hammond that such large beds of clams (or oysters) are not sustainable in a natural world – that such large populations soon sustained greater and greater populations of clam predators – that in the end overfishing is likely explained as a contest between man and natural predators who would have the last clam. The Connecticut Oyster Industry according to George McNeil a retired oyster grower from City Point New Haven and Clinton, CT learned the painful way as oyster culture became more established it seemed to “nourish” greater amounts of starfish. In time entire vessels would by rigged with huge cotton mops to try to keep growing starfish populations at bay. This aspect was also brought out in comments by retired bay scallopers in Niantic Bay – that there was and so many bay scallop after the cold and hurricanes in the 1950s (it is thought now that the cold enabled bay scallops to live in the shallows during this negative NAO period) that by the 1960s the Waterford – East Lyme Shellfish Commission had a starfish predator control program – as each season saw greater numbers of these predators.

According to George McNeil some deep water oyster beds had to be abandoned to “rolling” starfish balls – starfish became ball like gripping each other to roll with the tides and entering a planted oyster bed spread apart like an advancing army killing any oyster they wanted. When they caught starfish balls in the mops they knew the end was near – the industry started clearing and rotating beds to avoid this predator build up. John “Clint” Hammond would mention a problem with Quahog clam bedding many times – that it was the equivalent of ringing natures dinner bell that great quahog sets were like a surrounded army in ancient days surrounded and enable to escape slowly killed in a predator massacre. He had seen these areas before after storms the remains of such “vanquished” quahog beds which now consisted of only dead shells. He had also seen the remains of Native American shell middens and have noticed conch shells mixed with the quahogs no doubt to him at least this predator/prey relationship was an old one. The low salinity areas were protected from this serious predator.

Belding in his 1920 report mentions this as well, although in this period of heat quahog did not flourish in the shallows (pg 52).

“In some localities there may occur a slight loss from the winkle, a natural enemy of the quahog. The culturist can by more or less labor, according to their abundance, keep them off his property. As the winkle is valuable for bait, the actual loss of time will be minimized, and even if unmolested the damage will be slight.”

In time this predator/prey relationship would be reviewed and the first records of a fishery for conch would by the Nantucket and Martha’s Vineyard Islands. In the same waters that also held quahogs. In the 1900s it was Cape Cod and the Islands which had cooler waters is where the quahog held out the longest. In the southern waters sets had failed and continuous fishing depleted the beds until it is thought natural predation had turned the bottom into grave yard of empty shells. When New York City markets needed quahogs they looked at the Cape and Islands for the last supplies.

As some Cape Cod planters started to also culture or “bed” quahog as seed oyster supplies dried up (1950s) they ran into problems with conch. The channeled whelk Busycon canaliculatum was problematic but was trapped first with staked horse shop crabs and later box traps. The first traps were patterned after the wood milk crates first used to store clams (plastic milk crates would also find multiple uses). They noticed that channeled whelk could climb over the milk crates, but knobbed whelk preferred a subterranean attack from below and largely unseen. The knobbed whelk Busycon carica however could move into shallow areas in cold and proved to be a more challenging predator it preferred to attack quahogs from below burrowing to them out of sight.

Very shortly clam planters in Waquoit Bay in Falmouth started putting bottoms on quahog boxes (Olin Kelley personal communication, T. Visel 1982). I was able to watch these old quahog boxes put to use as the Narragansett Upper Bay opened up to bullraking as Olin Kelly of Waquoit Shellfish bought thousands of bushels at a time of low price to “bed them down” until the market prices improved. When asked about the boxes it was mentioned to me they would keep the “winkles out.” It was here that I saw immense growth on planted seed clams. (T. Visel 1982) Mr. Kelley in this many conversations then by eliminating winkles clam grew at tremendous rates and set heavy under shells in Waquoit Bay. To Mr. Kelly the exchange of sea waters and slightly cooler conditions favored the growth of clams in the 1960s.

The natural carrying capacity came in as well, the heavy sets of clams no doubt increased clam predators and I use Mr. Frank Dolan’s (Guilford, CT) example of this - nickels on a school yard, he gave as an example to me decades ago. Throw a few nickels in a school yard chances are they would probably be missed, but bring a dump truck full of nickels and dump it - it would quickly “attract attention.” This is true with our shellfisheries according to Mr. Dolan then a hydraulic clammer in Connecticut. (A more detailed account of Mr. Dolan’s advisor on soil cultivation can be found in NEFSC Tech memo 220 2011. This bed soon became a whelk (conch) feeding ground feasting on abundant clams. The predators would now “do well” (and I don’t think it’s coincidence that some of the first mentions of a conch trap fishery would come from Nantucket decades later). With size limitations, it just most likely did not pay to work these areas (Again, historic Nantucket fishery reports or records may in the future fill in much of this habitat history here, T. Visel) and heavy sets now faced normal habitat carrying capacity and now a growing prey population. The absence of energy now worked against this fishery. Soils succeeded and in time, soil pore space collapsed, predation increased decreasing quahogs in a killing field resembling a surrounded army with no hope of escape.

What was thought to be a good management tool - minimum clam sizes- now worked against this carrying capacity. Heavy sets meant slow growth (as mentioned many times in the quahog and soft clam historical literature). They just didn’t reach legal size quickly while greater predation now occurred. The end was most likely a slaughter, as the prey population now surged and then collapsed leaving behind the dead shells of millions of clams and marine soils waiting for yet another cultivation event (storm) that may be in decades or centuries later. In all probability, the big winners in a size regulation effort was conch (predators), not “us.” Many just did not “reach” legal size. In this case, minimizing shellfish sizes in my opinion worked against this seed source and stopped cultivation (harvest) aspects similar to agriculture. Some areas have and will again be sources of tremendous amounts of seed quahogs, but not adults. (T. Visel personal observations of Paines Creek, Dennis Mass seed quahogs in excess of 100 clams to the square foot). This creek had several sand bars and large amounts of “honey sand” large sand grains – in the upper reaches ware sand bars with covering of organic matter. A bathroom plunger (a type of device modified with a collection net) was a quick way to determine the substrate type. A few plunges yielded hundreds of small quahog seed clams. Small clams at the surface (pea size) with dime size clams below. Local soft shell clammers had notified me of this natural seed bed. The channel edge had thousands of seed clams an area depression about a foot in diameter yielded over 100 seed clams, no adults were observed. It was mentioned that a cold winter could freeze these seed clams but winters now seem to be mild and seed had survived. The key factor in is resource question is why Mr. Hammond urged the studying of 1880-1920 period (see IMEP #40) he felt held many clues to a habitat “reverse” as he described it as part of a long historical habitat cycle.

The collapse of the “cold water” species and increased rise in warm water species was most noticeable on Cape Cod. The Chatham, Massachusetts community and those that had coastal ponds in the 1950s harvested huge amounts of bay scallops while in the 1880s had harvested huge amounts of soft shell clams; he termed it a “reverse” of species. To him the 1800-1920 period oyster sets was an important clue - a warm period followed by cold. He also countered men’s influence upon oyster habitats and looked at the rise of humus (organic compost covering oyster habitats) and the work expanded to keep oyster beds clean. While oyster sets increased, so did nature’s humus - a much larger foe than “us” was perhaps “leaves?” and much of the oyster industries past production can be limited to the work it took to maintain oyster habitats, much like agriculture. When nature provided the “work” we are often surprised by habitat succession; we shouldn’t be when we can provide it also.

I respond to all emails at tim.visel@new-haven.k12.ct.us.

When quahoging or when talking to quahog fishers many accounts described areas that seemed to catch more quahog seed than others - at times these accounts of enormous seed capacity seemed to be difficult to believe. In time I have come to believe that as they indeed accurately described unique habitat (soil) conditions – some areas were better at generating seed and other habitats (soils) better at growing it out to legal size. By the time I had started a position with the University of Massachusetts in 1981 I had already conducted about 15 inshore fishing gear workshops with the University of Rhode Island University of Connecticut and eastern Long Island New York. It was during these inshore fisheries workshops I was exposed to the concept of “seed beds” and a trade in seed quahog clams. Some areas seemed to catch a set every year (for a more in depth look at Marine Soil Cultivation For The Quahog see the Cultivation of Marine Soils (1989) To Increase Clam Production on The Sound School publications list Sound School – publications directory) in fact so much so they would starve – or push each other out of the bottom for green crabs and other clam predators.

These areas were once harvested not just for food “legal size” shellfish but also for seed and like the oyster and bay scallop fisheries sometimes seed was moved, either to elicit better growth or to keep it from freezing, especially with bay scallops. From some accounts tens of thousands of barrels of seed clams were being moved in the 1880s from deep water to shallow areas. Quahog – populations near New York City “died out” in the 1880s as it warmed – adults were “harvested out” and these clam fisheries soon declined, now suspected to be the result of a warming (hot period) and a habitat recruitment failure (marine soils in the south failed first in the increasing heat). When you examine in the fisheries records, fishery failures often follow habitat failures – frequently listed as over fishing but usually related to severe changes (over time) in habitat conditions. The problem with habitat change in the marine environment is that it is so slow – moderated by extreme temperature changes by the sea itself. It is also out of sight. The 1880s into the 1890s had record “heats” that in time transitioned near shore fin and shellfish habitats. The 1890s were especially hard on southern New England’s cold water species (IMEP #55-A) and many “stead fast” species collapsed, the quahog, lobster and bay scallop. Despite accusations and blame there was nothing the fisheries managers could do. It got very hot. At times farmers and fishers are subject to climate habitat impacts as well. Even if all fishing and ceased the end result would have been the same.

Climate Patterns Important to Marine Soils

When I returned to the University of Connecticut Cooperative Extension Service – Sea Grant Cooperative Program in 1983 Connecticut was in a period of drought. The Dean of College of Agriculture UCONN then gathered all the Cooperative Extension Agents together (myself included) to review the serious agriculture situation that Connecticut farmers were now facing. After several hours of developing protocols and creating a plan to deal with the drought and then two hours of plan discussion the dairy agent rose in the back and asked the Dean politely if a good plan will make it rain? The response was no but it was a habitat lesson that I will never forget - a good plan (fishery management) won’t return good or previous habitat conditions as well for fish or shellfish either – for clams however we may have been able to “help.” Nature provided at times it seems the best habitats for tremendous clam sets into estuarine and subtidal soils. We have often failed to take advantage of that. Over time marine soils change as well subject many times from the same soil characteristics as the land. When winter flounder populations dropped in southern New England – many hand hauled otter trawl fisheries were closed and in those salt ponds habitat (soils) actually failed faster. The otter trawls themselves were actually “leaf rakers” and helped winter flounder keep habitats clear of Sapropel. When that hauling activity stopped leaves accumulated and it actually caused habitat conditions to worsen. (See IMEP #41 Arnold Carr letter of 1983). The increase of Sapropel would have severe toxic consequences for marine soils in times of high heat and low energy. Flounder small boat trawlers watched as sandy/shell covered alkaline soils became sulfur smelling and subject to acid conditions. These soils were covered by Sapropel which emitted toxic compounds but sealed soil spaces, porosity needed for oxygen exchange. When this occurred these bottoms likely became fungus covered and emitted hydrogen sulfide in the water. Any hard shell clam can perish from sulfide – starvation if bottom conditions do not change.

Clam Culture – Cultivation can in time and the correct soils reverse this habitat condition.

Often in descriptions of good “setting” ground the waste of seed or slow growth is frequently mentioned. Many times these habitats collect far more seed that the habitat can sustain (called the carrying capacity) and they were moved to other grounds (similar to Agricultural practices) for better growth. In the process of harvesting seed and scratching, lifting and washing of marine soils seemed to improve later local clam sets. The historical literature is also filled with accounts of sulfide and sulfuric acids impacting clam growth and sets. Over time as soil conditions changed to a bigger clay percentage or increased organic matter clam sets soon declined. The largest natural cultivation events in the marine environment soil wise are from strong storms. Here waves, currents and tides act to free soils of excess organic matter (the source of sulfide and sulfuric acids) rinses subtidal marine soils and enables them to “catch a set.” This is most often more seen with the soft shell clam (it is often shallow water and therefore more noticeable by fishers). One account in the Rhode Island Annual Report (1905) of the Commissions of Inland Fisheries see page 107 highlights this situation.

“Another case in point was observed at Greene’s Island on the east shore of this island is a long flat in 1901 was set so thickly with (soft shell) clams that 7,910 were counted in a single shovelful.” And mentions the natural mortality of these intense sets (and appears in the Cape Cod quahog literature as well). The “protection” of these small seed clams is a regulatory dilemma – these heavy sets had yet to approach “legal size” but Rhode Island fishery managers noted the huge mortality of such seed clams in protected areas. For nearly all these seed clams that “set” very few would ever reach legal size. (This seed potential is now lost).

In the 1970s Martha’s Vineyard and Nantucket used to employ a hydraulic lift “Hanks Rig” to move large quantities of soft shell clam seed that set heavy in the shallows but would have starved to death if not moved. A newspaper article titled “Clams Being Moved To Ensure Growth in Edgartown Project” appeared in the Cape Cod Times, June 19, 1977 (courtesy of Ron Ribb). This program was very successful according to John Hammond and other shellfishers I met while working on Cape Cod but large scale seed transplants were discouraged then (many seed transplants were off the books – fishers who could see this excess natural “waste” often would just move the seed themselves). Sometimes as regular fishing activities seed was moved to worked areas for reseeding purposes but ended as regulations and penalties increased for seed possession – in several cases “natural seed beds” beds that obtained far to heavy a set to grow were lost to the fishers and fishery when “cultivation ceased.” They just exceeded habitat carrying capacity, most likely perished. Fishers fearing legal fines or suspension of permits did not harvest the seed themselves for transplanting. (Workshop attendee conversations at URI, 1980s).

In a 1905 report (mentioned earlier Rhode Island Report of Commissions of Inland Fisheries pg 107) contain comments on the impact of harvest energy – the cultivation of soils is found this statement regarding the soft shell clam fishery.

“Summing up, them, the apparent conditions caused by digging over the clams, we find that continual digging may be beneficial to a clam bed by thinning out a too thickly set area and thus promoting more rapid growth in those that are left”

It was also noted that “over digging” could be negative and suggested a “sort of rotation of areas” to maximize production capacity of these habitats – still in use today but does not address the huge seed potential that is frequently wasted.

One of these seed accounts is written for bay scallops in Niantic Bay (see IMEP #7 on the Blue Crab Forum Feb 25, 2014, Niantic Bay Scallop Seed Transplants 1916 to 1935).

Some seed programs still exist for Quahogs and bay scallops but under municipal control and most often in northern New England towns in which local shellfish committee control still exists.

It is these natural seed habitats that may provide some clues as to which “soil” conditions seem to be the most productive. Cultivation does seem to be an important “energy” factor. Some of the largest quahog sets appear after a short but intensive storm filled periods – hurricanes in northern areas followed by cooler waters. In Rhode Island these quahog sets were known as the “great sets” of the 1950s and recorded later in higher quahog clam landings. Harvest energy is also recognized as a harvest/reproductive factor. Most quahoggers (bullrakers in many cases) nearly always agree to the benefits of working (cultivation) of subtidal marine soils – again a quote from the 1905 Rhode Island report highlights this belief – on page 105 under section VI The Continued Investigation of the Life History of The Clam (soft shell) Methods of Artificial Propagation and Cultivation on page 105 contains these comments (it is during the Great Heat 1880-1920 in which soft shell New England clam populations then soared).

“Owing to the great abundance of clams every where, the size attained was not very great. The clams were so crowded together that they could not attain full size” and “it is the common opinion of the clammers that digging over the clams stimulates growth. The idea which they seem to have is that the loosening of the earth (soil) about the clams is as good for them as it is for a hill of corn or potatoes.”

When I was working on Cape Cod shellfishers often cited the “thinning of carrots” example as on agriculture practice to the aquaculture managements of natural seed beds, certainly the Rhode Island report alludes to this, the number of set once mature could never fit into a shovelful.

“Another case in point was observed at Greene’s Island on the east shore of this island is a long flat in 1901 was set so thickly with clams that 7,910 were counted in a single shovelful.”

And mentions the natural mortality of these intense sets (and appears in the Cape Cod quahog literature as well). The “protection” of these small seed clams is a regulatory dilemma – these heavy sets had yet to approach “legal size” but Rhode Island fishery managers noted the huge mortality of seed clams in protected areas in 1905 pg 106.

“A portion of the shore was set aside by the Commission for the purposes of experiments, and was not dug over at all. Alongside this protected area the shore has been visited almost daily by the clammers. In the protected area the clams were so thick at the time of setting that there was not room for the growth of all of them, and so, as they increased in size, many were forced out upon the surface, so that in a short while the ground was thick with shells. The ice carried off many of the small clams in winter, and the gulls and black ducks destroyed many more; but still they were so abundant that there was no opportunity for growth, and their size has increased but little, averaging now but a little over an inch” (1905 RI).

The State of Massachusetts Pleasant Bay Report mentions the positive impact of estuarine bivalve shell on the setting of quahogs themselves 1967 – Massachusetts Marine Bulletin series (courtesy of Bruce K. Carlisle – Massachusetts Coastal Zone Management Office).

In a study of Marine Resources of Pleasant Bay Cape Cod – May 1967 Philip G. Coates, John D. Fiske, Clinton E. Watson, Monograph Series #5 – Division of Marine Fisheries pg 38 mentions where divers found heavy concentrations of quahogs were sandy mud (habitats) covered by empty quahog shells. (This condition “shell hash” is frequently mentioned by shellfishers).

“The most productive quahog bottom is characterized by sand mud covered with a thin silt accumulation. In one area where diver biologists found quahogs to be exceptional thick, the bottom was covered with great numbers of empty quahog shell these mats of empty shells were indicate of extensive mortality which occurs in this crowded population of quahogs. In many areas, especially the upper portion of the estuary, rapidly spreading eelgrass growth was noted to be taking over quahog setting and growing bottom.”

The association of oyster shell to clam sets was well known to the Connecticut oyster industry as told to me by George McNeil of the McNeil Oyster Company of City Point, New Haven and Clinton, Connecticut. When producing market oysters on lots (3 to 5 years old) when large numbers of quahogs appeared in the oyster dredges it was a sign that the oysters (the desired crop) was thinning out and production dredges had caught up the surface oysters and now penetrating the soil. He gave the example of beneath the soil potatoes except hard clams especially large ones were of little value and often just shoveled over board. Clams then were often of little value. It is important to remember that at times clams (softshell) were not as sought after as they are today. When Mr. McNeil spoke of the soft shell clam industry in New Haven Harbor was more important as salted “string” bait for offshore long liners (Cod Fishing) and before that pig food – not the steamed often seasoned soft shell clams of today. In fact when you consider a bushel of soft shell clams retails for some 200 dollars or more it has become the “gold” of the seafood shellfish market - that was always not the case.

The oyster industry then wanted 5 to 7 inch oysters for markets out west that demanded a large oyster a “Philly” oyster 240 count to the bushel. That has also changed in the industry as well with a smaller cocktail oyster marketed today. Hard shell clams were not a readily marketable product in Connecticut until the 1960s. That is due to the fact that the best quahog soils were in deep water sub tidal soils and not subject to a hand harvested fishery. When hydraulic harvest dredges were introduced in the late 1950s market conditions to began to make harvesting possible. When the prices of hard clams increased in the 1970s the hard shell fishery become significant and the association of bivalve shell to quahogs beds well known. An account of this association can be found in appendix #1 (John Volk account). The ability to culture these marine soils could raise the carrying capacity if thinned and managed like oysters. In time good soils would show “sharps” and less quality soils “blunts.”

And the stunting of seed clams - long a problem with dense sets mentioned on the same page of Pleasant Bay (Coates et al 1967) and the fact that such areas to produce excellent natural sets but slow growth and natural mortality prevents much of a legal harvest – in fact most of the food production (commercial valve) is lost although sets remain consistent. This is an excellent description of a natural clam quahog seed bed on Cape Cod in the 1960s.

{From the same 1967 Cape Cod Report – Pleasant Bay Coates et al State of Massachusetts}.

“An important observation of this study was that in the most dense concentrations, individual quahogs showed considerably less new shell growth then individuals in lesser concentrations. Because of this, one of the major study recommendations was that dense populations of sub-legal quahogs be thinned out and transplanted to other areas in the town” and the following -

“The high concentration of seed quahogs in the bay and the problem of overcrowding is further pointed out by a transplant project conducted in waters of Harwich and Chatham (Cape Cod). For many years, fishermen of both towns have been aware of a large bed of seed quahogs located along the Harwich shore of Pleasant Bay. This bed is on the edge of the major area worked by Chatham and Harwich fishermen. Fishermen generally avoid this bed of quahogs because the number of legal-sized quahogs are relatively few in comparison to the great number of seed quahogs present. Oddly, the general condition of this bed continues without any noted change in the ratio of legal-sized quahogs to sub-legal size. The reason for the unchanging character of this overcrowded bed has been attributed to the fact that competition for food results in very slow growth and that natural mortality occurs prior to their attaining harvestable size. While mortality among the larger quahogs appears to be high, the condition of the bed in perpetuated by excellent natural setting.”

Although the study recommends seed transplanting from this area which as the study includes this recommendation) when I arrived on Cape Cod in 1981, 14 years later most of the hard clam habitat mentioned in the study was transitioning into soft bottom/eelgrass Sapropel habitats. The hard shell clam reproduction and growth were “list” in these areas. Ron Ribb a local manufacturer of quahog rakes and other shellfish equipment recalled the changes in bottom habitats in the late 1970s to me during several visits. In 1981 – 83 when I was employed by the University of Massachusetts Cooperative Extension Service, many shellfishers recalled the advance of eelgrass/sapropel (locally called Black Mayonnaise) had just suffocated acres of hard shell clam habitats, he was forced to adjust his rakes for a now growing softer bottom. Several clammers also mentioned a positive impact of bivalve shell cover, perhaps a pH buffer but several mentioned predator protection as well. As eelgrass grew into these shelly setting grounds clammers also mentioned sets ceased, and dead quahog clams could be found under dense eelgrass growths Sherril Smith, DMF shellfish survey 1982).

Mr. Ribb in a conversation during one of my visits mentioned years ago quahoggers would help move seed – sometimes under municipal guidelines. They could see the habitat conditions at times push the seed from the soil itself – for easy prey of (crabs) and seagulls. On the Cape Cod islands themselves hydraulic harvesting was used to move soft clam seed (he provided some old newspaper articles along with John Hammond) and mentioned in IMEP post #2 Feb 2014 on the Blue Crab Forum™. There were a smaller version of the “Hanks Rig” and moved hundreds of bushels of small clams, having found natural seed habitats that set so thick they produced few adults. He mentioned that fishers would find these dense seed beds and thin them out – planting areas that held good “bottoms” but little seed. The good bottom reference is mentioned many times in the shellfish literature and nearly always refers to soil characteristics including gritty sand, shell hash or loose soils.

A similar situation occurred in Connecticut around the oyster industry. In the Connecticut a seed oyster fishery from rivers and creeks, natural growthers those that handled seed oysters culled “blank shells” on the banks – eventually those shells would be exposed to sets, bank sets of oysters could in time expand to the lower edges. Some areas were good at producing seed oysters but not adults. The sets were so intense that overcrowding caused a terrible mortality and very few oysters survived to an adult. These areas were identified and utilized as a source of seed, with small oysters transplanted to higher salinities (better growth) and space to develop a round shell shape. That practice became the foundation of extensive oyster culture.

Bay scallopers also moved small bay scallop seed, driven a shore by storms millions of scallops would perish if not moved and many accounts can be found of small boat scallop fishers coming together to move scallop seed (See IMEP #7, The Blue Crab Forum™.

NOAA Technical Memorandum NMFS-NE-220

Review of the Ecological Effects of Dredging in the Cultivation and Harvest of Molluscan Shellfish

US DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service Northeast Fisheries Science Center Woods Hole, Massachusetts
December 2011

Historical and Anecdotal Observations on Dredge Harvesting

Historically, opinions on the best methods for shellfish dredging have varied widely. Fishermen who used hand tongs or rakes often considered dredging detrimental to shellfish, while those who operated dredges believed that dredging of the seafloor enhanced the environment for clam and oyster recruitment (Glude and Landers 1953; Manning and Dunnington 1955; Visel 1990b). Rake and tong fishermen believed specifically that dredging activities could injure, smother, or kill shellfish; increase exposure to predation; interfere with successful recruitment; destroy eelgrass; or damage the seafloor (Glude and Landers 1953; MacKenzie et al. 2002b). In contrast, dredge operators felt that bottom cultivation improved seafloor conditions, kept sediment from becoming too compact for habitation by clams, and enhanced bivalve recruitment and growth rates. Anecdotal observations by fishermen have suggested that dredging may be more efficient than hand tonging or raking and results in less shell breakage, mortality, and unintentional burial than manual techniques (Kyte and Chew 1975; Coen 1995). Further benefits of dredge harvesting may include reduced mortality among target species, decreased impact on the benthos, increased catch rates, and reduced labor as compared to nonmechanical collection methods (Coen 1995).

Observations made by shellfish growers can provide valuable data on harvesting impacts and recovery. Harvesters sample the seafloor each time their gear is deployed (Cranfield et al. 1999), a level of effort which exceeds sampling regimes associated with most experimental studies (Dorsey and Pederson 1998). Access to local knowledge held by fishermen allows for a better understanding of habitats when selecting areas for study (Peterson et al. 1995). Frank Dolan, a Connecticut clammer for over fifty years, associated poor clamming and high clam mortality with acidic sediment conditions. He monitored acidity by rubbing clam shells together in a bucket of seawater; formation of a white cloud indicated “sour” or low pH substrate, while shells from healthy beds produced no cloud when rubbed together (Visel 1990a). Dolan indicated that spreading a light coating of shell to remediate or “sweeten” sour bottom could improve setting of shellfish. These anecdotal observations suggest that dredging and adding shell may actively increase pH levels. Dolan also believed that differences in sediment pH can impact shell morphology and observed that clams grown in “sweet” areas exhibited sharp edged shell margins compared to slower growing clams with blunt shell edges found in “sour” areas of little or no shell cover. He found that rotation of shellfish beds, light shelling, and allowing a 5-7 year waiting period before harvest were key elements to good shellfish production (Visel 1990a). He avoided detrimental practices such as early harvest, which exposes small clams to predation, planting in water deeper than 30 ft and cultivating in areas with too much clay. Dolan found cultivation of oysters to be associated with improved growth and enhanced production of hard clams. Interviews conducted with long time clammers and oystermen provide a rich history of observations concerning habitat and resources and suggest that shellfish cultivation may improve bottom environments and increase clam and oyster abundance (MacKenzie 1979; Rice et al. 1989).

Anecdotal evidence suggests that disturbance from large-scale coastal storms is often followed by large natural clam sets, likely because of removal of surface detritus to reveal clean sandy bottom (Visel 2008, 2009). Storms and hurricanes in the marine environment act much like forest fires in terrestrial habitats by facilitating succession from one type of community and habitat to another through wave action and sediment transport. Natural storm disturbance, which washes silt and organics off the seabed, mimics the action of hydraulic dredging (Visel 2008, 2009). Extended periods without benthic disturbance can reduce sediment quality with a corresponding decline in clam populations. The concept of “marine soil cultivation” using dredges, rakes, and tongs has long been advocated by the shellfish industry to loosen and oxygenate sediments and to remediate unoxygenated and heavily silted bottom devoid of clams. A lack of shellfish cultivation in certain coastal areas of Long Island Sound may have resulted in reduced shellfish sets and a loss of potentially harvestable clams and oysters (Visel 1990b). Cultivation efforts which remove silt from cultch may create good settlement habitat for oyster spat and may benefit clam recruitment by increasing sediment pore size to improve water circulation (Visel 2006). Many fishermen believe mud bottoms are detrimental to shellfish and that turning over of oyster shell matrix improves clam and oyster production (Lenihan and Micheli 2000) by promoting settlement of larval shellfish (Coen 1995) and keeping the bottom free of silt and organic matter (Ingersoll 1881; Visel 2006).
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