CT Oyster Reefs During The Great Heat 1880-1920 IMEP 19

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The Sound School Inter-district Marine Education Program
Newsletter IMEP #19

Habitat Information for Fishers and Fishery Area Managers
Understanding Science Through History

Connecticut Oyster Reefs During The Great Heat 1880-1920
Are Natural Oyster Beds – Sustainable?
ISSP/Capstone Project Proposal
A long term view is needed to define what natural abundance is and what is not
A Possible Quinnipiac River Oyster Pond Study, New Haven, CT
Capstone Questions/Proposal Topics for Sound School Students
Tim Visel, September 2011 – The Sound School
Capstone Catalog - June 2014

{IMEP Habitat History Newsletters can be found indexed by date on the CT Fish Talk™ salt water reports thread and The Blue Crab™ info fishing, eeling and oystering thread websites}

Foreword June 2014 –

Since this Capstone proposal was developed three years ago several research initiatives have commenced looking at geo historical data for oyster restoration and shell middens left by Native Americans for evidence of climate change.  Key to this historical review is evidence of habitat reversals – periods of time in which oysters thrived and then for reasons which remain unclear suddenly did not.  The section on the prehistoric oyster shell heaps of the Damariscotta River by Harold W. Castner (1950) was recently reprinted by the Damariscotta Historical Society, the Boothbay Register, and Boothbay Harbor Maine in 2004 has been added as the third appendix.  The layers of shell and organic matter humus mentioned by Castner are representative in many ways of Connecticut estuarine core studies of the 1990s.  The comments about the remains of trees unfamiliar to this climate are now of special interest.  Mr. Castner was already making climate connections a half century ago.  Core studies are also under review for local evidence of habitat reversals including cores taken in salt marshes.

Abstract –

The morphology and characteristics of natural oyster reefs can be divided into two basic habitat regions, river and estuarine.  Questions have been raised recently about the how energy determines a habitat clock for oyster reefs or when oyster beds start to form and grow – then mature and eventually fail or die.  Energy is usually a hurricane or tropical storm starts an oyster reef "habitat clock" and it also can end it.  Oyster productivity may not be totally from biological factors but include climate and energy parameters as well that can only be measured over long term periods.  We are fortunate because of a record of oyster sets and oyster growing conditions before Connecticut's golden age of oystering can be attributed to shell shape and temperature.  The examination of Native American shell middens - historic shell heaps – even dead shells can provide us important clues about the habitat condition of past oyster populations, and how frequent sets over time occurred and even climate factors that tend to bury oyster reefs.  (See Making Dead Oysters Talk Kett. B. W. 1988).

Two basic types of oyster reefs exist – a soft bottom and hard bottom type.  The soft bottom is typical in medium to low energy habitats with high rates of organic deposition (harbors and bays) hard bottom reefs are found in high energy areas offshore fringing the coast immediately adjacent to river natural beds.  Although hard bottom oyster reefs give the appearance of stability they exist in an unstable environment (waves –storms) and therefore subject to periodic high energy events (see CT Great Island Connecticut River Oyster Reefs).  They may come and go responding to long term climate patterns such as the North Atlantic Oscillation or NAO.

Medium to low energy reefs can grow several feet in a decade as generation after generation grows on top of each other.  Riverine oyster beds can have a mixture of reef types – dependent upon the energy (location) they obtain from currents – soft bottom to hard bottom.  They also exhibit over time the largest changes in shell shape.  For a complete description of these beds see Sound School publication #33 – A Review of Fisheries Histories for Natural Oyster Populations in Tidal Rivers MH/SF-9.  It is available as part of our Adult Education and Outreach Program.

Introduction –

The role of energy pathways (waves, currents) in the creation of oyster reefs has been well defined in the scientific literature (See Paul Galtsoff, the American Oyster 1964 USFWS Index of Shell shape).  The ecology and function (environmental services) of oyster reefs are currently under review.  Part of that study examines long term trends or habitat histories for such areas.  The pattern of oyster reef growth from oysters in historic shell middens reports in Maine (Harold Castner study) to today should be measured in hundreds, possibly thousands of years.  However, the larger more powerful the energy pathway period the faster an oyster reef can occur.  This in part explains the periodic heavy sets upon offshore natural beds (reefs) from New Haven west to Greenwich, CT and the absence of them to the eastern Long Island Sound areas at the turn of the last century.  It also describes the energy from current flows in tidal rivers and the source of larvae that can set on storm washed or "cleaned" offshore areas.  Offshore oyster reefs (frequently call natural beds) are largely governed by storm energy (intensity) and temperature.  The open sections of eastern Long Island subject to intense storms and cooler waters have not contained such reefs for hundreds of years.

River natural oyster reefs can grow much faster because of currents or "daily tidal energy."  Two decades of growth for example created oyster reefs in the Neck River in Madison to grow 3 to 5 feet high – interfering with established recreational navigation.  In 1963-1983, such rapid growths are rarely mentioned for off shore "high energy" natural beds.  Pipe penetration tests of the Neck River revealed accumulation of live oysters that grew from 1971 to 1981.  Although a two bushel day landing limit was in place for the Neck River from 1966 to 1973 it did little to control the upward reef growth and from 1973 to 1981 oysters grew upward with no harvest due to shellfish closures from bacterial contamination.  The East River oyster beds exhibited similar habitat conditions.  Prior to 1966 the year in which the East River had its first harvest closures from high bacteria levels commercial oystermen kept the oyster beds "closely cropped" and worked these oyster beds with limits set by the Guilford Oyster Ground Committee.  Harvest ranged between 5 to 8 thousand bushels per year (Joe Dolan personal communication to Tim Visel 1978).  In 1978 it was suggested that the Neck River be dredged by the Army Corps of Engineers to control the oyster over growth problem but instead it was opened to natural growth seed oystering. 

Offshore areas are subject to higher energy and much more severe events (storms) but less often reefs may take hundreds if not thousands of years to build.  Even the concept of a reef is somewhat of a misnomer as the reef itself is often migratory but the habitat "clock" is so long we cannot measure or see it move.  Only during that strongest energy events "hurricanes" can we see habitat clocks quickly change.  Not so with river natural beds here the energy is much more constant and therefore habitat clocks much shorter.  We can see and measure the changes – depth increases with changes in river morphology depth decreases in areas of slower currents, within decades – not centuries.  All oyster reefs require some work (energy) natural or man provided.  Once the first oyster sets and a reef forms they begin to succeed and created a habitat history when buried.  This is especially true in the Oyster River in Old Saybrook where successional accounts mention periodic burial. Oyster reefs by their very nature appear to be static habitat types but historically have patterns or cycles.

Historical Accounts of Habitat Succession -

These cycles of abundance or habitat clocks were recorded in the historical literature and appear to mirror climate conditions.  We now recognize these patterns of temperature and rainfall as the North Atlantic Oscillation or NAO for short.  Several oyster fishermen felt that Connecticut inshore oyster abundance between energy events was more governed by rainfall and disease outbreaks than harvesting.  Others felt the offshore natural beds were controlled more by storms driven energy events that cleared silt from reefs and dislodged long buried shells cleaning them for potential spatfalls (see the McNeil account of New Haven's lost natural oyster beds on The Sound School Adult Education directory). 

It seems natural that periodic great sets of oysters would and did occur but the natural beds could also suffer long lasting "shell loss" – a reduction in the setting surfaces for oysters from storm burial or harvesting.  As oysters themselves begin to grow they naturally trap organic matter.  In this natural process however loose shells or oysters are buried.  Removal of the top shell layer stops the reef building but reduces the potential of future spatfalls.  Early oyster culture practices soon realized the importance of these surface "blank shells" to the oyster fishery, however, the extent of the shell loss today remains poorly understood.  It is today compounded by a high organic low pH bottom conditions which is apparently dissolving shell faster that it can be replaced.  (This high heat/high organic loading is made worse by a generally lowering of ocean water pH now described as ocean acidification.  This has severe implications upon bivalve aquaculture worldwide). 

Severe energy events such as hurricanes or cold or Northeasters have a history of reversing pH soil declines so that after them estuarine pH conditions may be more suitable to shell accumulation than warm acidic periods of dissolution.  Therefore natural beds may come and go - naturally as a result of energy "pathways" organic burial and temperature (climate).  It may be possible to obtain habitat histories of these rivers and cove areas with core studies.  It may also help explain deposits of fossil shell under many feet of non oyster bed materials such as those found in Maine as described by Harold Castner and the condition and growth of ancient river oyster populations. 

John Volk former Chief of the State of Department of Agriculture Aquaculture Division an expert SCUBA diver once remarked that oyster shell bases in the Housatonic River were tens if not hundreds of feet deep but shell bases on the Bridgeport Natural Bed was less than two feet and that largely consisted of mixed sand and shells (personal communication to T. Visel).  Other studies located long buried shells and sand layers as part of the Coastal Energy Impact Program study (CEIP) from the 1970s (Volk personal communication).  Obviously at some point in time other LIS areas had been productive for oysters but no longer so.  These areas were and continue to be subject to energy – coastal storms burial and re exposure of shell bases over hundreds of years.  Warmer temperatures (those associated with a positive NAO) also correlate to increasing or decreasing oyster sets (a negative NAO).  Researchers in the 1970s also reported alkaline sea water pH – a period now recognized as having cooler water temperatures.  In warm periods shell loss appears to increase and perhaps related to an organic burial/Sapropel low pH conditions.

Other species may have also benefited by oyster populations and this habitat association appears to be especially noticeable between winter flounder and shellfish populations that produce bivalve shell or estuarine shell "litter."   Estuarine shell does has structural or reef habitat benefits.  Warmer temperatures and few storms appear to favor strong oyster recruitment potential we call "Sets."  Warm periods appear to favor terrestrial vegetation and burial factors that seem to be regulated by weather patterns.  Habitat services from oyster shell include energy modification, buffering acidic bottoms and structure – habitat modification.

Hard Bottom, High Energy Reefs – Food Web Benefits 

Bivalve shell also appears to have an increasing role in pH habitat quality for both hard and soft shell clams.  Connecticut oyster growers of the last century noticed excellent sets of Mercenaria (hard clams – Quahogs) on bottoms recently shelled for spatfall or transplanted seed oyster beds.  The presence of shell is now associated with buffering marine soils.  Frequent accounts also include the appearance of winter flounder over a nearby oyster population, oyster reefs could influence habitat clocks for others species as well, that has been one of the more recent habitat questions.  This appears to be true for winter flounder habitat in our area.  Low pH acidic organic bottoms Sapropel have been linked to necrotic fin rot disease in winter flounder.

The ecology of soft bottom and hard bottom oyster reefs are quite different, the soft bottom and more shortened habitat clock growth areas provide the larval stock to inoculate higher energy offshore areas.  Spawning may occur within the normal salinity ranges but on deeper higher salinity reefs spawning is infrequent or not at all.  Gonads may ripen but spawning is nowhere near what is produced from riverine natural beds.  Here sets grow quickly to two years as space constraint slow growth, it was these seed oysters that were replanted bedded to growing or fattening beds*.  The inshore beds protected from high salinity predators should be considered a future spawning resource as seed stock or set for offshore areas.  The oyster industry in Connecticut maintained such spawner sanctuaries well into the 1960s.  These areas were cleaned down to a firm shell base mixture of adult oyster set over them to act as a preserve of spawner stock.

* The term bed comes from the use of term bedding stock from bed down for winter – to put down a bed of hay a term to signify a collection or group or organisms in this case oysters.  European origin, colonial term was oyster flats or clam flats.  The term flat still has agriculture meaning as a collection of similar plants.

Soft Bottom Reefs in Medium Energy Estuarine Areas -

Sometimes a reef can be started by a series of clusters groups of set oysters on a single exposed shell or fragment of shell or even a blade of vegetation.  This can occur over relatively soft bottom and over time small shells fall from the oyster clusters which in tend to grow larger and closer.  Eventually (which can take tens of years) the bottom is covered with a crust of oysters which now grow upward as shells are now trapped between the clusters forming a firm base for the upward expansion and its habitat clock is now visible.  Under this crust and noticeable with a driven metal pipe is soft organic sediments or Sapropel ooze below – often containing a high sulfide smell (personal observation Oyster River, Old Saybrook).  Upward growth or reef building will continue until energy or water temperature constrains growth as the weight of the reef building compresses the organic layers below.  Eventually the reef will block or change energy pathways – the energy river currents themselves at its sides may erode it the back or shore side may build up and the entire reef if subjected to waves or storms may migrate towards the shoreline.  The erosion process releases shells which before being buried in acidic sediment (Sapropel) can obtain sets as the "reef now moves.  The movement may take tens of years to observe so the only way to look at this is with core studies.

In estuaries periodic high energy events can destroy the reef, which now is subject to increased energy and rebroadcast the shells and shell fragments over a wide area.  Oystermen of the last century frequently found these types of reefs immediately offshore of rivers in embayments with high organic matter deposition.  They would report breaking through the oyster "crust" to rich soft organic deposition layers below (see George McNeil account in New Haven's Lost Natural Oyster Beds).  These oysters will have the long and tall shells, called dogs.  Oysters that moved into soft bottoms will grow again representing are called jackknife oysters resembling the shape of folded pocket knife.  They have this characteristic shell shape on all soft bottoms.  When seed oystering in the 1970s I would occasionally break past this crust into the soft organics below.  As oystering continued below this layer very often a large band dead oyster shells can often be found.  Large shells significant a steady yet very slow "habitat clock."  Some relic oysters uncovered by dredging projects in New England are often much larger than we often see today.

In southern areas and on rare occasions in New England reef clusters can be started on waste shells from the Atlantic ribbed mussel.  Here predation by skunks and raccoons can scatter shell debris on soft bottoms which can obtain oyster reef sets (Personal observations).  Oysters can and do frequently set on such shells and oyster clusters in tidal creeks are found very close or adjacent to dense populations of the ribbed mussels.  Atlantic Mussel shells have been collected in Tom's Creek, Madison, CT covered with oyster sets completely covering the shell.  Shell fragments from predation frequently were observed with partial, eaten shells and raccoon footprints nearby.  Other times oyster sets were so intense seaweed and other marine vegetation can have oyster set on it.

Cove and Bay Seed Oyster Sets Have Shorter Habitat Clocks.

In larger bays and coves oyster set may occur in areas in which it will never mature or survive (heat in summer, freezing in winter).  Sets in shallow zones in areas of gravel, shell fragments and clean tidal pebbles may be intense but succumb to shore driven waves or winter freezes.  An area of heavy oyster setting is still found on the western edge of Clinton Harbor as told to me by George McNeil – a series of pebble bars set heavy with oysters but would be washed to the shore into the marsh.  Called thatch oysters – one could easily gather several bushels of nicely shaped seed oysters on pebbles that by December would all die and continue to do so every year (Personal observations 1970s).  The early history of the culture of oysters involved moving seed oysters from dense vulnerable areas to deeper (safer) areas to grow.  Madison and Clinton frequently see the sets of "rock oysters" on stones along the shore – much to the misery of the occasional summer swimmer – they grow fast and have extremely sharp shells.  They occur after unusually dense widespread oyster sets.  However many coves and bays receive tremendous organic loads, leaves, forest litter and dead grasses quickly build up smothering oyster sets.  These events are often recorded as organic/shell layers in core studies.

Oyster on firm sandy bottoms tend to have rounder thicker shells, soft bottoms oysters have thinner more elongated shells.

Site of Study – Can We Find Shell Layers in the Upper Quinnipiac "Salt Pond"

The upper reaches of the Quinnipiac River widens and forms what has been called an oyster pond but it really just headwaters of the Quinnipiac River at Fairhaven.  From time to time the pond has held thousands of bushels of soft bottom oysters.  The last significant harvest was 1980-84 with approximately 200,000 bushels of seed oysters being harvested (John Volk, personal communication 1986, and Tim Visel observations same period) small skiffs and scows towed hand hauled seed oyster dredges working the edges of the river where a soft bottom set had matured – sets from 1978-79 which were excellent matured quickly.  As with many soft bottom sets the oysters quickly over grow crowding out each other and killing oysters underneath.  Heavy sets occur on "lip" or mantle shell areas sets occur here because the new calcite oyster shell is cleaner and suitable for a spatfall.  As much of the oyster pond areas was deeded out to private ownership a century ago permission would of course be needed from the deed holder(s).  As seed oystering continued the oyster crust was penetrated and large oyster areas then dropped into organic ooze.  It is thought that the weight of the oysters collapsed into the soft ooze below.  This appears to be a natural process perhaps hastened by seed oystering.  Conversations with some seed oyster fishers then indicated the bed was shifting almost daily – this must have left a larger layer of shell buried – a core sample could possibly show previous layers.

Suggestions for a Capstone Project

With appropriate permission and deed research the following tasks are suggested for this project (one or more, see Supervising Aquaculture Teachers).

1)   Locate and identify any leased or granted oyster beds, important for letters of permission also for the upper pond area (Quinnipiac River). 
2)   Obtain a scientific and educational permit from the Dept of Agriculture – Aquaculture Division, Milford, CT  (Dave Carey, Director)
3)   Contact Tessa Getchis at Sea Grant UCONN Avery Point, Groton and provide a copy of study for comment/review.
4)   With tongs or hand dredge complete a shellfish survey looking for natural oysters in a selected area (areas). A metal pipe 10 feet long also may be a help.  This can identify the existence of buried shell layers.
5)   If oysters are located index for habitat type hard or soft and shell shape from Galtsoff 1964 – map locations for oyster populations.
6)   Contact local shellfish companies arrange for visits inform them what you are doing and why.
7)   Build and present a PowerPoint with research paper that can be shared online – as a basis for continuing research.  Long term project for students in the future can benefit from previous studies.
8)   Several environmental organizations may be interested in this work and possibly provide funding for internships.  Several exist in the New Haven area,
a)   The Quinnipiac River Watershed Council
b)   The Nature Conservancy – Connecticut Chapter
c)   The CT Fund for the Environment
d)   The New Haven Land Trust

9)   Contact the Long Island Sound Study – the Habitat Restoration Committee might be interested in a presentation. Their office (the study) is in Stamford, CT.  The study maintains an extensive website.
10)   Can you compare your study to others in CT or New England region, interested students in this Capstone project should read the internet paper "Making Dead Oyster Beds Talk."  It is an excellent article which describes many of the research questions presented here.  Also please read oysters setting in New Haven Harbor by John Volk it is paper #8 on the Sound School directory (shellfish/finfish directory – MH 6 Marine Historical #6.

Summary -

To understand the role and ecology of oyster populations we need many more long term studies that include energy as well as harvest or culture practices.  For example, the success of the Connecticut oyster industry of the last century was largely due to reducing environmental constraints associated with the lack of energy – the 1880-1920 period known as "The Great Heat"1 – clean washed shells, a slightly alkaline pH soil and absence of silt.  Once industrial practices modified habitats with this manmade "energy" oyster production soared – when energy was removed oyster productivity collapsed, without energy inputs these populations were not sustainable and diminished to natural habitat parameters2 such as the NAO.  The same could be said for terrestrial agriculture – harvest/culture energy and habitat succession.  One could quickly see this transition habitat wise with lawn care, the natural environment in the sea is not as evident or as quick. 

Oyster restoration is now the topic of several research studies but often miss the importance of energy and temperature.  Without considering climate and energy restoration is hit or miss and only successful for relatively short periods of time.  It may prove very costly in some areas but others it may be relatively cheap – only as supplemental cultch (shell) surfaces.  In knowing the difference we may substantially shorten habitat clocks and ignore areas in which the habitat clock has long since passed.  That is the goal and purpose of this student research.

For more information about conducting a shellfish survey or spat collection experiment please see Tim Visel in the Aquaculture Office.

Program reports are available upon request. For more information about New Haven Environmental Monitoring Initiative for IMEP reports, please contact Susan Weber, the Sound School Adult Education and Outreach Program Coordinator, at susan.weber@newhaven.k12.ct.us

For information about The Sound School website, publications and/or alumni contacts, please contact Taylor Samuels at [email protected]
The Sound School is a Regional High School agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.

Appendix 1

Table #1 Oyster Sets of The Great Heat 1880-1920 Period

For a period of about four decades New England summers were becoming especially hot first beginning to moderately warm in 1881 – afterward each summer seemed to become hotter and duration more pronounced peaking in 1896 to 1899.  The heat waves of 1896 and 1898 were particularly severe and deadly to the southern New England lobster fishery but blue crabs and oyster fisheries now soared with these warmer temperatures.  The rise in oyster sets was quite noticeable and described as The Great Oyster Sets – 1899 being called the set of the century for New Haven growers. 

After 1912 summers became cooler and by 1920 winters became more severe and cooler springs often delayed or had inconsistent oyster sets.  According to George McNeil whose father J. P. McNeil operated a oyster business at 62 South Water Street (where The Sound School Cafeteria is today) noticed the Portland Gale 1898 (in all probability a rare November hurricane) cleaned shells the year before the 1899 set which Mr. McNeil described as the strongest set in a century (personal communications to T. Visel 1980s).  This "gale" destroyed the 1898 set but provided the washed or "clean" shells for the 1899 set.  The State of Connecticut Shellfish Commission began to list the success of the oyster set – in 1887 and this chart in the July 1953 – July 1955, Report of Shellfish Commissioners – Office of the Shellfish Commission, 185 Church Street, New Haven rooms 711 – 715, for those interested in history – Dr. John S. Rankin who would later found the marine sciences program at UCONN was one of three shellfish commissioners at this time.

As the weather became colder and sets came late or not at all.  After 1912 the Connecticut "Great Oyster Sets" were gone.  (The relatively cooler water temperatures have been frequently mentioned as the result of a negative phase NAO.  The NAO pattern of warmer and cooler temperatures is now the subjects of dozens of research projects that are reviewing fisheries and climate change – T. Visel, June 2014).

Table 1
Oyster Sets of The Great Heat 1880-1920
CT Report of The Shellfish Commissioners

Year         Set - Description           Number of Natural Bed Boats     
1882        Ok-Probably          -
1883        Ok-Probably          -
1884        Ok-Probably          300 
1885        Ok-Probably          -
1886        Ok-Probably          - 
1887        Abundant              -   
1888        Light               - 
1889        Light               - 
1890        Great Set             - 
1891        Fine               - 
1892        Fine              - 
1893        Fair               - 
1894        Fine               256 
1895        Fine               247 
1898        Good              302 
1897        Uneven             196 
1898        Failure              122 
1899        Fine              276 
1900        Only Fair              324 
1901        Light               217 
1902        Poor              81 
1903        Very Poor             24 
1904        Splendid             258 
1905        Scattering              267 
1906        Very Poor             193 
1907        Very Poor             157 
1908        Scattering              177 
1909        Poor              131 
1910        Poor              138 
1911        New Haven Only         154 
1912        No Set              136 
1913        Failure              98 
1914        Light               117 
1915        No Set              68 
1916        No Set              43 
1917        No Set              28 
1918        No Set              21   
1919      Bridgeport Bed Only      161 
1920        No Set              126 
1921        No Set              73 
1922       Set from Spawning Beds        41 
1923        A Little             57 
1924        No Set              31 
1925        Fairly Good Set         40
1926        Fairly Local Sets         40
1927        No Set              21 
1928        Good Inshore Set         9 
1929        Scattering              20 
1930        Fine                34 
1931        No Set              32 
1932        No Set              9 
1933        No Set              17 
1934        Good              11 
1935        Very Light              14 
1936        No Set              34 
1937        Light Set              47 
1938        Very Poor             28 
1939      Fair Set (Mostly destroyed by pests) 12 
1940        Fair Set              37 
1941        Very Light Set          24 
1942        Very Poor Set          29 
1943        Light Set             22 
1944        Fair to Good           11 
1945        Fair              20 
1946        Fair – Spotty          31 
1947        Very Light             27 
1948        Very Poor             27 
1949        Poor              20 
1950        Poor              29 
1951        Very Poor             10 
1952        Very Poor              9 
1953        Very Poor              3   
1954        No Set              4 
1955      Very Poor             3 
1956        Poor              7 
1957        Fair              4 
1958        Very Light             0 
1959        Poor              1 
1960        Poor              12 
1961      Poor               5 
1962        Poor              - 
1963        Poor              - 
1965        Poor              - 
1966        Fair to Good          - 
1967        Light               - 
1968        Good              "S" License Holders # Issued) 
1969       Fair to Good          ? 
1970        Fair to Good          ? 
1971        Fair to Good          ?

In 1965 – 1966 the NAO pattern leaves a negative phase and now turns positive - resulting in warmer New England winters.  After 1966 oyster sets in Connecticut after started to improve.  As the NAO turned strongly positive and waters warmed oyster sets improved and then became intense and widespread into the 1980s.

Appendix II

What is a Commercial Level Oyster Set?

Students who have access to run or sample of oyster cultch containing a set can quickly determine the commercial level – a bushel contains approximately 500 blank shells (average)    0 – 2,000 set – poor    (set per bushel measure 0 to 4 set/surface
      2000, 4000 – good
      4,000 – 8,000 – very good to excellent
      8,000 – 10,000 – excellent
      10,000 – outstanding
      20,000 – fine or abundant (great sets)
(50,000 set/bushel has been documented by Clyde Mackenzie of NOAA in 1968 on lots of Long Island Oyster Farms, New Haven Harbor).  Some of the heaviest sets ever recorded is off Morris Creek New Haven Harbor on lot 151 or in the lower farm River Estuary between East Haven and Branford.  Good oyster sets returned to Connecticut as waters warmed again in 1973. 

What is a commercial level "set?"
This paper written for Connecticut Shellfish Commissions in 2007 describes the method for determining a set and the price paid to natural growth seed oyster harvesters.  Anything below 2,000 set to the bushel was the lower purchase limit.  A bushel of shells contains about 500 blank shells or 25 coffee cans lightly shaken.

The "Set"

The set occurred each summer with the natural spawning of oysters in creeks, harbors and rivers.  First, eggs and sperm were fertilized in the water column and then matured. Next, this "spat" settled to the bay, cove or near shore bottoms looking for a place to "set."  Clean oysters shells were the preferred place to start the four-to-five-year process of growing to an adult.  Oyster growers and natural growthers knew this, and laws were enacted concerning the return of shells to the water so that ample setting surfaces were present.  Oyster growers would plant hundreds of thousands of bushels of oyster shell on owned acreage to supplement the natural set.  The rate at which they would plant was 1,000 to 2,000 bushels of clean, dock dried "cultch" per acre.  Stirring with the use of cotton maps (once used to remove starfish) flipped over shells and washed silt from them.  After a heavy rain such beds would often be "stirred."

In late July, Connecticut oyster growers would carefully look for signs of the first "spat fall" and would microscopically examine sampled shell surfaces looking for it.  This event would signal almost around the clock shell planting, as the period of setting was limited and had a defined "window" of success.  Shells planted too soon were subject to natural marine fouling and silt covering the shells with a slippery coating.  Too late and the young oysters had perished for lack of suitable substrate.  It was a gamble that clean oyster shells would be on the bottom just as the oysters' larvae (spat) stopped drifting in the water and settled to the bottom or "set".  A few days either way would make or break the commercial outcome five years later.  By August, the oyster setting period was considered usually over, although some historical records mention a few sets in September and even one as late as the beginning of October.  (George McNeil, personal communication - Tim Visel 1970s).

What Is A Good Set?

According to George McNeil and Hillard Bloom, a good set was around 4,000 per bushel of oyster shells.  Fewer than 2,000 per bushel was seen to be the lower limit of purchasing "seed" oysters.  It was anticipated that, at best, only 500 oysters out of 2000 would survive to market size (about twenty dozen per bushel) 6 to 8 thousand set per bushel was excellent, and over that "outstanding".  That may seem like a lot, but a bushel of shells can contain up to six hundred shells – or over a thousand potential setting surfaces.  At 2,000 set per bushel, that would only be about 2 small "set" oysters per surface or less.  To the eye the new set is only about the size of a flake of pepper.  I have seen some shells with over 100 set on one surface (New Haven Harbor Quinnipiac Dredge Vessel Survey 1971).

Determining the Set Count

Before seed oysters (newly set oysters on shells) were purchased, the set count needed to be calculated.  Oysters were harvested from an area which was sampled.  These samples combined to predict the average set per bushel.
Shells would be collected from 5 bushels and each sampled until 5 coffee cans of shells would be taken.  25 coffee cans of shells equals that of one bushel – and the shells are then "counted out."  The other method is to take one coffee can from each bushel – count that out and multiply by 25. At about 25 shells to the can at 2 set/shell or 50 set/can x 25 = 1250 set/bushel or low to "poor."  I have seen some shells with up to 50 set on each or about 1000 set/can x 25 = 25,000 set/bushel which is outstanding.  (MacKenzie, Jr. from NOAA {1970} "Oyster Culture in Long Island Sound" recorded oyster sets of up to 50,000 set/bushel.)

Price Paid By Volume

According to Richard Roberts, a natural growther for many years, it was too time consuming to count out each bushel of set, so the prices were paid on a per bushel or volume basis.  If the set count per bushel average was 2,000 and the price negotiated, then it is possible that 200 shells with an average of 10 set, or 2,000 could be combined with 800 empty shells or "blanks" in a bushel measure.  Or it could be 1000 shells at 2/shell, the price would be the same, 2000 seed oysters in a bushel measure.  If the set count dropped, a price was renegotiated.  If the count dropped below commercial levels, buying from natural growthers would stop.  At this time all oysters from waters closed to direct harvesting was considered a "seed oysters"  "Set" oysters and sized larger "seed" often had different prices.
Appendix 3

A Historic Trilogy by Harold W. Castner
The Prehistoric Oyster Shell Heaps of the Damariscotta River

Just previous to the Civil War, Professor Chadbourne of Bowdoin College, made a thorough study of the deposits, and established for all time, conclusive proof that these shells had been left there as a result of ancient feasts, and at a time so far in the past, he dared not attempt computation.  He found many individual piles of shells ten or fifteen feet in diameter and several feet deep.  Beneath this, the soil was made up of a diluvial deposit of sand, gravel and rocks, resembling the land adjacent to the deposits.  There were numerous bones of animals, birds and beavers, and even a sturgeon's plate.  A dark line ran through the bottom of the great mounds, showing the possibility of vegetable mould, formed during temporary abandonment of the place.  Shells under this layer were decomposed, or turned to lime, as if acted upon by fire.  He obtained shells of other types than the oyster and found some clam, quahog, and several kinds.

Despite the loss of hundreds of tons of shells by erosion and commercial uses, a great volume still stands exposed to view.  Scientific investigation revealed that there were three distinct periods of construction of these heaps.  In each case there was a period of abandonment, during which time a thick layer of vegetable mould accumulated over the shells.  The lowest layer of shells extended over about one eighth of the present known area.  This layer was about three feet thick, and at the base, many large tree trunks were found which had decayed to powder, leaving conical hollows around which the shells were packed.  Directly above this layer was a strata of mould which was some five inches thick.  It has been quite accurately determined that it takes about one hundred years to accumulate an inch of mould.  We can, therefore fix the period of this first abandonment at about five hundred years.

The second layer of shells was larger and more extensive.  This was about six feet thick and covered by mould to the thickness of about three inches, or, let us say, an interval of three hundred years of the second abandonment.  In this second strata of mould were found trunks of large trees which were of unknown species in this climate.  They were two or three feet in diameter and had grown up entirely over this second strata of shells.  These trunks were better preserved than those of the first strata, but although they held their form, they easily crumbled in this hands.

The third strata of shells had a layer of about three inches of mould over it.  An intimate study of this top layer of mould caused scientists to agree that it was about three hundred years ago when the last deposits were made, or at the time of the Wawenock Settlement, at this place of abundant food supply.


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