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Author Topic: "Living" Shoreline Artificial Reefs and "Tabby Reefs" - Sound School IMEP #4  (Read 1766 times)
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« on: February 11, 2014, 03:35:24 PM »

The Sound School Inter-District Marine Education Program Newsletter

                                                       - IMEP -

Habitat Information for Fishers and Fishery Area Managers

Understanding Science Through History

The Sound School – December 2013

The Return of the “Living” Shoreline Artificial Reefs

The Creation of Oyster Culture “Tabby Reefs” Looked to Protect
Shorelines and Provide Habitat Services Again

Tim Visel – The Sound School

In the early 1900s, New Haven, Connecticut Oyster Companies soon ran out of “growth out” oyster ground for oyster culture. The tremendous sets on the eastern New Haven Harbor side needed space to grow. Some of the densest seed oyster sets occurred on the east side off Morris Creek. The area rivers, especially the Quinnipiac River, were leased or offshore areas were declared “natural beds” and could not be leased or granted leaving New Haven oyster growers fewer grow out options. Some Connecticut oyster companies had already established a presence in Wickford, Rhode Island and then looked to the northern waters of Narragansett Bay for needed grow out ground. But by the 1900s, most of the best firm bottoms were already leased (still a sore point with the Quahog Bullrakers in Rhode Island) so oyster companies looked at less than optimal bottoms now to harden to make firm enough to support the weight of a thin shell base (to give some relief or wash aspect) and planted seed oysters. The reef aspect was important because depressions tended to gather silt and Sapropel (rotten leaves) and oyster growers needed to keep oysters from being suffocated or killed by hydrogen sulfide the so called “black water deaths.”

The “shell base” therefore was an important component of oyster culture that is today often overlooked. Currents were needed to keep the grow out grounds free of organics, leaves, dead seaweed and silt. The finest submerged bottoms were “taken up” before 1900 in many areas, especially in Wickford, Rhode Island. As oyster sets increased in New Haven, oyster companies experimented with hardening “soft” grounds. Areas that were soft were filled with rubble, concrete waste, coal clinkers and mixed with shell; basically anything that could change soft habitats into firm ones. Oyster growers soon noticed that this mixture with oyster shell became very firm and took the name of a precious colonial lime called “Tabby” and the name stuck. At the turn of the century New Haven even fielded a baseball team called the “New Haven Tabs.” Tabby was burned oyster shell lime used in a cement like mortar. In the late 1700s and early 1800s as the importance of returning shells for seed oysters became known, burning shells was soon forbidden. Some of the best examples of this come from western Long Island Sound especially the community of Mamaroneck, part of Colonial Rye, New York.  On page 33 of the History of Rye, New York 1660-1870 Board (1871) includes this passage:

“For the houses built of stone, abundant material was at hand in the coarse granite of the region, and in the great heaps of oyster and clam shells, when the Indians had left in many places, and which the early settlers found very large shell heaps for making lime.
All the early accounts say the editor of Novum Belgium speaks of the immense accumulations of oyster and clam shells and their use for lime. (page 40)Mr. John F. Watson, the author of historic tales of olden times (New York, 1832) mentions the fact upon the testimony of an old resident of the city then living that they used to burn lime from oyster shells in the park commons (page 99).”

In the late 1970s I had the opportunity to go bullraking in Narragansett Bay and witness chunks of this tabby base that was still occasionally raked up. It looks like coal, sand and bits of shell all glued together. In time this material hardened and is still hard a century later. Oyster shell in acidic conditions recombines and forms a hard road base. It was a driveway material of choice centuries ago because it does pack so hard. The oyster habitat service of tabby was of course to provide a firm base upon which to grow oysters. Now this concrete chunk, oyster shell mixture is looked to now to protect shoreline by creating wake breaks. Because of its calcium base it also “buffers” reefs from acidic conditions a growing worldwide concern while providing subtract to corraline red algae.

The Tabby bases in upper Narragansett Bay habitat case failed after 1938. So much silt was washed over these once soft habitats they became soft once again. Oysters suffocated in these artificial habitats but released oyster shells buffered acidic marine soils. When the 1950s and 1960s came with multiple storms one after another and colder temperatures, once productive oyster habitats eventually “failed.” Instead loosened marine soils and relic oyster shell buffered acidic conditions and facilitated the great Upper Bay Quahog sets in the same habitats once made suitable for oyster culture. Some of the densest clam sets were in fact over or in abandoned oyster leases.

By that time climatic conditions had turned against the oyster growers. Colder temperatures meant that oysters spawned later and had to survive colder winters and the sets came far too late for cultch. Shell surfaces quickly grow bio-films and within about a 20 day window oyster spat “slip off” and perish. Constant hurricanes then part of the North Atlantic Oscillation buried shell bases with living oysters killing them. By the 1950s most of the Rhode Island oyster houses had closed, but the great sets of Quahogs in the Upper Bay had already occurred. Strong storms in colder climates provide a “deep” Quahog set the ability to live deeper in cultivated soils. Clams that can live below the zone of protection verses a shallow set that can be preyed upon or just washed away. Great sets, those that are a “deep set,” occur about three times a century partially explaining the relatively long life span of quahogs. Clams do more deep into marine soils to escape predators and storms. Clammers often report this as well.

This paper was recently sent out to coastal groups attempting to reexamine the oyster company’s use of tabby reefs at the turn of the century with today’s renewed interest in coastal energy and sea level rise. It was modified slightly as a discussion paper for the habitat work group of the Long Island Sound Study.
It is therefore necessary to review the history of materials and quantities used – what materials are most suitable then and how “tabby” once formed. In acidic conditions, rain water can dissolve the shell forming a “slip” on rainy days. In dry, warm days this coating sticks and cements the aggregate again. The oyster shell road bases of colonial times had the reputation of being as hard as concrete and why it was a favorite road base material. It made an excellent shell base as well.

Tabby for Living Reefs

One of the materials looked at again especially with acidic ocean waters is waste concrete, the rubble mixture (processed concrete and oyster shell).

This paper was first developed last September for a group in Old Lyme, Connecticut. It reviews aspects of why oyster companies secured huge quantities of shell and some of the habitat services from it.  It has since been modified for a potential habitat Capstone Research Project at the Sound School.

Concrete and Oyster Shell Reefs

A “Tabby” Reef


Oyster aquaculture a century ago used shells for hardening coastal habitats that created firm bottoms that could support the weight of seed oysters.  But that use came after the first “shell” products of mortar called tabby and then road bases in mud prone areas.

“Shells were crushed for use in chicken feed, lime for farms, and primitive concrete called “tabby.” Virtually every low country town and many rural areas built and repaired roads with shell. In 1890, Charleston applied 36,000 bushels of shell to maintain Meeting Street.2”

Since the time of the first Colonial settlements, oyster shell was a resource of value, first as a way to produce a strong mortar, called “tabby” and later as a road base (pre-engineered street drains) as a soil buffer and finally feed for chickens to strengthen egg shells.  Only later in the 19th centuries did a growing oyster aquaculture industry realize the significance of recycling oyster shell for oyster culture itself. Oysters prefer to “set” upon a substance that has a similar pH and every bushel of shell could produce five bushels of “seed” oysters, sometimes many more.  Years later Connecticut and other oyster producing states soon enacted laws that forbid using shells for roads (although it does make an outstanding road base) limit how many bushels of shells you could collect in one day for chicken scratch and outlaw burning shells for lime/tabby outright.


Such “shell cultch” only laws have been in place in Connecticut for over a century, but rarely enforced. At the turn of the century, oyster fishers also noticed the oysters would set upon concrete, the problem was chipped concrete washed away (like shell) or quickly buried in soft sediments; it was denser than the lighter oyster shell.  Not so with larger concrete pieces and some of the first artificial reefs were constructed with surplus concrete pipes at the USFWS Boothbay Maine Fisheries Laboratory in 1966.  Here researchers found that lobsters preferred the manmade circular homes (concrete pipes) six times that of nearby natural reefs.

In southern areas as wood trestles across bays and bridges were replaced with concrete each poured “piling” was soon encrusted with thick oyster sets. It was hard not to notice that concrete soon made excellent spat (oyster) collectors.  (East River Guilford mooring area blocks 1974).

When the climate cooled after 1921, Connecticut oyster sets became infrequent and after 1931 they frequently failed. Oyster companies no longer had the capital to purchase mined relic oyster shells from the Housatonic River. Here an entire industry grew up along the shores of the Housatonic River that harvested relic or fossil oyster shells long buried by land erosion. “Shellermen” tonged up to sixty bushels of “blank shell” for use in oyster beds “cultch” each summer and got 8 to 10 cents per bushel for it, (see “Rivermen, Shellermen,” by Philip Teuscher, pg 18; Sea History, #50 Summer, 1989.  And there was a lot of them, when test core drillings were made prior to the breakwater construction at the mouth of the Housatonic River they showed oyster shells down to a depth of ninety feet. Oysters deep in the sediments were often huge and grew elongated into spade-like shell (commonly termed “shangs”) and someone who harvested by washing and moving them by a propeller was called a shellerman.  Millions of bushels of oyster shell was harvested this way and later special props developed for “shell kicking” was developed to wash up long buried shell. (Philip Teuscher, 1989).  As oyster sets diminished oyster companies could no longer afford to purchase “blanks” but saved their own shell to store and plant themselves. The days of the Connecticut shellerman were largely gone by 1950.

Today in fact oyster and clam shell is scarce, and when the State of Connecticut restored its remaining oyster reefs, in the 1980s in western CT, it had to buy bulk blank shell from the Chesapeake Bay region.  Oyster shell restoration programs often fail because the base oyster reef height has been so reduced it sinks into soft sediments. A shell base has been utilized in oyster culture for over a century consisted of using sand, gravel, broken brick, concrete waste, and even cobbles to firm up the bottom before laying down valuable oyster shell.  Concrete chunks are now being looked at for providing such a “shell base.”
In Florida, I learned (1973-74), some of the most prized material for making artificial reefs then was concrete.  Today it is a valuable component to coral aquaculture and known as live rock.  Its popularity as a sub base rock for live coral aquaculture is increasing3 and eliminates natural deposit over collecting.  A chip of concrete is exposed to coral to attract a coral “set.”  Concrete scrap or waste was valuable because it would allow corals to live on it. It is not acidic but basic and at the time, desired because it had the same pH as coral and could support many living organisms. In addition to structural reef benefits, encrusting organisms can cover steel and wood such as barnacles and blue mussels and are valuable, but this material does not support coralline red algae. Coralline red algae do appear in Connecticut during cold periods; when sea bottoms are alkaline, not acidic. It needs an alkaline substrate upon which to attach and grow.

A tabby reef is a moderate profile reef, designed to support a wide range of encrusting organisms and alter energy from storm waves and surges. It has structural benefits as ecological, habitat services, but not those associated with reefs built from old ships or retired railroad cars (high or strong profile reefs). They function like breakwaters but to do block energy pathways they redistribute and dissipate energy, they have similar bearing and compression features requiring careful site selection (so they will not completely sink into soft bottoms) and avoid burial by scour which can happen on high energy high profile reefs in high energy areas.  I prefer the old term of “Tabby,” a mixture of concrete and shell, because it is a natural constituent reef; it does have a life span and eventually disappears, much like the coming and going of natural oyster reefs or even sand bars for that matter.

Oyster Shells and Oyster Reefs
Many oyster shell reefs are being built for oyster culture down south, but many regions have relearned about the wave energy breaking ability of fringing oyster reefs, similar to tropical corals.  They can and do moderate shoreline erosion. Oyster shells both new and relic have become scarce and some historical man-made reefs used concrete as a base saving the surface for the laying of oyster shell. Such reefs do have wave energy suppression features as rounded mounds of living oyster on the top of the “shell base.”  These oyster reefs as in northern climates are periodic, Connecticut has had extensive oyster reefs but they only grow well in time of high heat and low energy, such as 1880-1920.  In times of cooler temperatures 1855-1879 or 1940 -1970, they are destroyed by hurricanes and storms. The two 1954 hurricanes destroyed much of Connecticut’s oyster reefs, and industry only recovered in the late 1970s.  Storms break apart these oyster reefs redistributing relic or ancient shell bases casting the shells out of the bottom and creating the conditions for increases in oyster reefs years later. This appears to be a 100 year cycle.

For more information concerning the value of estuarine shell to marine food webs and shellfish sets, click here for a link to our directory which includes “The Importance of Recycling Estuarine Molluscan Shell for Shellfish Sets” submitted to the DEP / EPA Long Island Sound Study Habitat Restoration Committee on November 16, 2011 – Revised on August 2012.

Tim Visel

The HIFFM  IMEP Newsletter is possible by an Inter-District Cooperative Grant (Public Act 94 -1) and regional marine education bulletins can be obtained or accessed on the Adult Education and Outreach directory by accessing the Sound School website: 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.

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 [email protected].

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« Reply #1 on: February 16, 2014, 08:34:24 PM »

Thanks got contributing this info to the site.

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