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      July 2012 Newsletter




Every human is born with enormous curiosity. Part of the joy of being a parent is witnessing the flowering of that curiosity in children. Our senses are not easily satisfied. We play with our food from day one. And then we expand our play to include the inedible. We soon become attached to these playthings and want to own them. Then we discover pets: animals we don’t eat but that serve as animate playthings.


It is still possible to “capture” a wild oyster and bring it home as a pet. It seems like an ideal way to observe the behavior of an animal that we already love. The first time I saw mention of this possibility was in a book entitled The Oyster: The life and Lore of the Celebrated Bivalve. Robert Hedeen, the author, describes how to domesticate a pet oyster on page 204. Put simply, he recommends wading out into the surf and bringing the oyster and its immediate salty environment home to raise in a five gallon fish tank.

If you are a scuba diver, you might even break off a small chunk of limestone shell upon which the oyster has established residence. Several oysters may cluster together on the same spent shell. They often point their shells skyward like the leaves of plants – not to reach towards the sun but to be able to more efficiently scoop food into their waiting bellies. Don’t clean the oysters. We also want some of its microscopic friends.

Now you have an aquarium full of brine with an oyster or two to feed. Hedeen recommends avoiding plants and fish. You won’t need a filter – the oysters will do that. Add a 60 watt light above. The idea is to use the light to create algae. Start with twelve hours of light and then reduce it to eight. You have also just started your own little algae farm. Hedeen does not mention a need to control the water temperature and a bubbler is optional. You must carefully mix fresh water with salt water. The proper salinity is important.

When I read how easy it apparently was to own a pet oyster, I wondered why more full size aquariums did not contain them. Obviously simulating the natural environment of an oyster can be a challenge. But the biggest problem is the food. Five gallons of water is peanuts for an oyster to filter. A mature oyster filters 15 to 50 gallons per day depending upon the size and season. Even tiny baby oysters filter the water they inhabit. They get fed in the process. A pet oyster requires supplementary algae in the form of concentrated algal paste. Microalgae costs around $250 per dry pound. You can Google it.

I did not fully appreciate the amount of algae an oyster consumes until I visited my first oyster hatchery. Ninety percent of the floor area of the hatchery was devoted to raising algae. At one end was a tiny vial of starter algae happily subdividing in the sunlight. At the other end were twelve oysters used for seed - in between, gallons of algae … a sea of algae. It is why oyster farms do not exist on land. It is why farmers don’t feed, check that, can’t feed their oysters. Bottom line? Only nature can feed oysters. She lets the sea do it.



Many ocean fronting states in the U.S. have “oyster garden” programs where private individuals obtain a small quantity of oyster babies (spat) already attached to shells. Such programs permit amateurs to “raise” oysters so they can watch them grow and change shape. The gardeners hang a container with a few hundred oysters from makeshift buoys or bob them from the dock. Like so many natural processes, it is amazing how fast oysters grow from May to September. Many gardeners give up their oysters at the end of the summer to oyster restoration or regeneration programs. The “spat-on-shell” are transported and placed in areas where reefs once were or now need to be. Some people get hooked on growing oysters in an oyster garden and start an actual farm for their own amusement and food. For those individuals who run these programs, that is the whole idea – to grow oyster farmers.

Once you start your own oyster farm, for fun or profit, you have the same problem as the person who wants an oyster or two in an aquarium. You want to keep them happy and healthy long enough to make the endeavor worthwhile. Few people eat their pets, so if you have an aquarium, you probably want a long experience. If you farm animals for fun, you are worrying about protecting your investment in time and money until you consume them. If you farm animals for a living, you don’t make money until you produce an animal you can sell. You seek an animal to raise to its highest potential for profit in the necessary amount of time. You look to the hatchery for good seed.



Hatcheries artificially create the circumstances necessary to encourage mature oysters to create seed. Scientists learned how to raise shellfish in a hatchery about 60 years ago. They have been employing selective breeding - choosing parents with desirable traits. The idea is to produce progeny that inherit speedier growth, more desirable shape, and improved resistance to disease.

Marine biologist Rob Rheault, Executive Director of the East Coast Shellfish Growers Association, further explains that there are two schools of selective breeding:

Old school: Take critters with desired traits and breed them. This approach has given us most of what we breed today for food (examples: plants that yield well and taste great and animals like cows that deliver 4X the historical cow’s milk or chickens with 5X as much breast meat) and for pleasure (examples: various "breeds" of dogs and koi). There is no need for sequencing or super computers.

The problem with this is that the phenotype (what we see) is the cross product of the genotype (the DNA) and how that DNA reacts with the environment (plus some random elements). So we are not sure whether a bred oyster survived and grew into a nice shape because it had the right genes or we just got lucky (example: maybe it lived in a great spot or had great food).

New school: More recently with the mapping of the genome and DNA sequencing (and super computers) we are able to match desired traits to genetics and then, when we breed animals with those specific genes, we are confident that the progeny has the desired genetic makeup - not that it just had parents that "got lucky".

Until quite recently, farm raising oysters for profit had three significant seemingly unsolvable problems.

      1. Oysters spawn in the summer. They spend energy doing so, slow down their growth, and can taste different around spawning time. Prespawn oysters can change their texture. Postspawn the meat quality deteriorates until the animal recovers.

      2. Oysters can take years to mature. Growth naturally varies by farm location and the growout methods used. A farm must contain simultaneous multiple grow-out crops to assure an ongoing fruitful harvest.

      3. Long term risk of financial ruin. Farmed oysters are constantly at risk. An entire crop can be hit by disease or a hurricane that can wipe it out.

      Farmers have lots of time to contemplate these problems. It is only human to try to solve them. As mentioned, we are born curious, we love to play with our food, and we want to protect what we own. Sounds like research to me! We need an expert opinion.




Watson: What if oysters simply stop spawning?

Holmes: Hmmm… A good question. If an oyster doesn’t expend its energy spawning, I suppose it will continue to eat all summer like a very small horse and grow like a shadow at sundown. We will be able to consume oysters in the summer without any spawny taste. Our larger crop will grow faster on the same small plot of land. Our risk exposure from disease or weather is reduced to a smaller time period.

Watson: Egad Holmes, I think you may have something there!

Holmes: Not so fast, Watson. Remember the tortoise and the hare?

As Holmes suggests, the recent history of the spawnless oyster is not without frustration and setbacks. The aquaculture research community has sought to formulate a method of breeding spawnless oysters that will not sacrifice other important qualities. Even while many farmers are growing them, research is ongoing. In areas of the U.S. that are dominated by aquaculture, interest in and use of them is the greatest. In areas where natural harvesting of oysters dominates, interest is still somewhat academic. As a consumer, you may have been consuming spawnless oysters for years without knowing it – especially if you have eaten oysters from the Pacific Northwest. There is only a market requirement to distinguish between “wild” and farmed oysters. A farmer makes his or her own choice which oyster seed to plant.

A hatchery must always begin with oysters that do spawn – even to create oysters that do not. All oysters that spawn do so in dramatically large numbers – millions of sperm fertilize millions of eggs. Interestingly, both oyster sperm and oyster eggs are milky white in color.

If you want to fully understand the technique to encourage oysters to spawn and produce seed that do not, you may need to return to school where you have access to a super computer and a powerful expensive microscope. An oyster that spawns has two chromosomes. One that doesn’t has three. A new breed of marine scientists are working on perfecting this new breed of spawnless oysters. Other scientists are using similar tools to furnish broodstock oysters that are immune to certain diseases. All the successful science eventually ends up in a hatchery.

There are a number of possible procedures to make the developing egg retain a third set of chromosomes. Such eggs are called triploids. Growers just call them "trips." These procedures are complicated and can involve various treatments. For example, just as the eggs have been fertilized and are about to undergo their first cell division, cold shock them or treat them with chemicals. Alternately, we can breed tetraploid animals with normal diploids. Tetraploids have four chromosones but are not sterile. This tetraploid-based method of producing triploids is most common in New England.

If you visit a hatchery that produces spawnless oysters, as I did recently in Dennis, Massachusetts, you will not see anything at all that suggests change. A small number of male tetraploid oysters and a small number of female diploid oysters are kept separate until the right moment when they are induced to spawn. The eggs are fertilized and begin the miracle of life. They are carefully monitored as they develop, become swimming larvae, and eventually become “spat.” The spat attach to a piece of shell – sometimes a tiny piece, sometimes a whole shell – where they hope to spend the rest of their lives.

The care and feeding of oysters that spawn and those that do not, is almost identical, with one significant exception: the spawnless oysters have the potential to grow faster. When they find the right environmental conditions to do so, they grow really fast. Farmers and researchers are both intent on discovering just what conditions will produce the best results. I found research in Massachusetts, South Carolina, and Virginia on the subject. Such research is underway worldwide.

So, you ask: Can you tell the difference? To answer this and other similar questions of comparison, OI sent a questionnaire to the East Coast Shellfish Growers Association (ECSGA). Here are some of the results:

[Please see Note 1 below.]



I found one farmer in Wellfleet, Andrew Cummings, who invited me to his Wellfleet farm. Andrew’s experience with spawnless oysters is pretty special. Prior to starting his own farm, he worked in Australia on a farm that was in full production of them. He learned to tune his farming procedures to their specific needs. Most importantly, he learned patience and precision. Some farmers who try to farm these oysters compare them to their conventional oysters early on, conclude that they do not conform to conventional shape standards, and abandon them prematurely. Andrew’s spawnless oysters grow fast! In one year, he can successfully bring a three inch C. virginica oyster to market.

Come awwwn, you say. Did you taste one yourself? Well yes I did, thank you very much. I comparison tasted one spawnless one year old three inch oyster and one normal four year old, also three inches long. Both were from the same precise farm and watery environment. And yes, there was a difference. The spawnless oyster seemed a tad more “pure.” It’s sorta like tasting a ripe banana and then banana ice cream. The meat of the four year old was denser, more substantial, a more complex taste. The shell of the one year old was thinner than that of its four year old counterpart. If you were served the two oysters side by side at a restaurant, you probably would not blink an eye and slurp them down. When you turn the spent shells over, the visible growth patterns of the two oysters are also quite different.

I should point out, that if I were tasting the oysters in mid to late summer, I would expect a dramatic difference in appearance and taste. The spawnless oyster would be fatter. That is the whole idea. With a spawnless oyster, the oyster spends its time eating and growing – not preparing to spawn, spawning or recovering from spawning.

Watson: So that settles it. The spawnless oysters are better!

Holmes: Not so fast Watson. Research is proving that these spawnless oysters do not out perform in all environments. Sometimes they just grow normally. It is very site specific. Success requires patience and care.

Watson: So what’s your conclusion?

Sherlock: Farmers are growing both spawning and spawnless oysters. It improves their options and that way they don’t put all of their eggs in one basket.

Watson: Good one Holmes. Ha. Ha. Ha…

Sherlock: Hey, it took thousands of years to perfect our edible oysters. Given his track record, I would not bet against the tortoise.



When we purchase oysters as consumers, we only own them briefly. The hatchery and farmers have done all the work. Our pleasure is increased to the max. Even shucking an oyster is fun.

With the addition of spawnless farmed oysters we have one more available nuance in taste and another reason to understand and fully appreciate what we consume. In the coming summer months, try some for yourself. They were raised quickly, but you can still take your time enjoying them. Ed.



Photo Credits: All photographs and graphics shown are the property of Oyster Information newsletter with the exception of the final oyster comparison photo which was provided by Diane Murphy and Cape Cod Cooperative Extension/Woods Hole Sea Grant. All four oysters are the same age. The two on the left are triploids. The two on the right are diploids. Thank you Diane.

Note 1: The full numerical results and background data of the OI questionnaire mentioned here are available by e-mail request from OI. The pie charts on view are based upon actual data but are presented here in summary pie form to convey their overall implications. Over 30 members of ECSA responded to the questionnaire. The demographic distribution of the respondents is also available by e-mail. OI offers thanks to those experienced members of ECSGA who generously completed the questionnaire.

Note 2: Several individuals freely provided their knowledge and resources to OI in an effort to produce a cohesive and informative result. Some of them also served as reviewers of the article prior to publication. We have tried to compose an issue worthy of their time. They deserve mention for their help but not blame for technical errors that may still have occurred. The final result is not a consensus opinion. OI  believes the article to be accurate.

We extend our special thanks to:

Standish Allen, PhD; William & Mary - Virginia Institute of Marine Science; Andrew Cummings; Marta Gomez-Chiarri, Professor, Department of Fisheries, Animal Veterinary Sciences, University of Rhode Island; Susan Machie, Algae Director, Aquacultural Research Corporation; Dana Morse, Extension Associate, Maine Sea Grant College Program and UMaine Cooperative Extension, Darling Marine Center; Diane Murphy, Fisheries & Aquaculture Specialist, Cape Cod Cooperative Extension & Woods Hole Sea Grant; Robert Rheault, Executive Director of ECSGA; Tom Rossi, President of 4Cs Breeding Technologies, Inc.; William Walton, Assistant Professor/Marine Fisheries, Extension Specialist, Auburn University Dept. of Fisheries & Allied Aquacultures & Alabama Cooperative Extension System.



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