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Shellfish seed collection substrates

This year marks the eighth year that I have been involved in the aquaculture industry. What I have observed in the countries I have visited, the people I have met, and what I have learned could easily fill a book. The process of change and adaptation to new concepts and ideas has been without doubt one of the more interesting things to watch, especially in the different regions with individuals or groups and their attitudes towards the shellfish industry as a business.

Efficiency, return on invested capital, product marketing, quality, and bottom line profitability are all too often forgotten or neglected. If you were to live by the rule that a smart person learns from their mistakes and a really smart person learns from the mistakes of others, I believe there would be a lot less focus on reinventing the wheel and more on the business of making money, which if you haven't asked yourself is the real reason that you are spending your time in this industry.

So as to make it clear, I am not trying to paint a picture of an industry full of capitalists whose only goal is the almighty dollar. We are in the business of producing food using a very small amount of the world's oceans, and by doing so efficiently we are giving these oceans and the species in them a very needed break.

Producing shellfish efficiently is made up of many different facets, from larval collection or management through to point of sale presentation that causes more people to eat more shellfish more often. To develop and offer solutions that will address the production needs of the industry now as well as in the future, our company operates within a culture of constant change or constant re-engineering.

Working with numerous manufacturing plants globally, which produce many different products, we are able to take advantage of what we know of advanced husbandry methods, and apply them to manufacturers' ability to produce equipment that improves greatly the efficiency of farm operations.

While this may sound rather simplistic, a thorough understanding of the different materials that are available, and how they and the manufacturer's design interact with the biological requirements of the species grown, are very important.

We also have to deal with the lack of adaptation to change by a great majority of the growers within the industry which becomes very frustrating at times because it just doesn't seem right to watch people take two steps backwards for each step forward.

To demonstrate this let's look at larval collection methods and substrate used for both oysters and mussels.

Within oyster collection there are a number of different methods that are currently practiced.

Oyster shells either by reef planting or remote set are still in use because they are freely available and because it is the way it has been done almost since the beginning of recognized culture methods. Their capital investment value is low, however the labor cost is very high and extremely physically demanding, actual efficiency compared to other methods is not very good. In fact once you calculate the actual cost per quality animal produced I wouldn't be surprised to find that most growers are working on some very slim margins.

The alternatives to this semi-natural method have evolved over the years and are interesting to follow and observe their development and efficiency.

Chinese Hats have nothing to do with China with the exception that they look like the traditional hats worn by field workers from that area of the world. They were developed in France a number of years ago however are not anywhere near as popular as they once were due to advancements in methods. Even though they were a giant step forward compared to shells there was still a lot of labor in preparing the hats with a slurry solution and the resultant harvest and separation of single animals at collection time.

French Tubes were the next development and what was significant is that a special process was developed to replicate the rough surface of a shell or rock during the manufacturing process similar to what the slurry produced on the hats had done. They were much more efficient then the Chinese hats in that they did not require the slurry preparation and at harvest almost all the animals were singles.

What is significant at this stage of the development is that the theory of the need for a substrate with a porous surface like a rock or shell was no longer valid and that a non porous, made of plastic, rough, increased surface area was workable.

Mini Hat Collectors are now one of the main methods of collection used in France, they do not require a slurry solution and interestingly enough have a relatively smooth surface area with only slight ridges to aid in settlement retention. Because they are smaller they are much easier to handle and harvest is very easy and quick due to their semi flexible nature which actually allows the settled spat to pop off the disc when it is flexed. Stripping machinery has been developed that mechanizes the process and a single worker can harvest a great deal of single seed in a very short time.

Oyster Collection Trays are the newest generation of advanced collection methods and really maximize increased collection per unit deployed as well as very much reduced labor per seed collected. Integrated fluted vents within a 2 ft x 2 ft frame will collect approximately 5000 - 7000 seed per tray. It has been stated that one person can strip up to 400 trays per day using a simple stripping table.

All the preceding will have different pro's and con's dependant on the site and the integration into the existing husbandry methods currently practiced. What is interesting is that the French tubes, the mini hat's and the collector trays all cost less then the Chinese hats, don't require the slurry solution and are by far much less labor, yet outside of France they are virtually unknown. The French were forced to be efficient due to consumption demands, growers elsewhere should be motivated by the efficiency and profitability or so one would think especially since consumer demand for quality product outstrips supply.

For the record it is important to understand that all plastics are not alike, there are hundreds of different polymers and when mixed together to give the end product different characteristics, there are thousands of different combinations.

The mixture of the polymers can react differently with the larvae of different species and can effect the collection accordingly. The effect of polymers on the biological aspects at the microscopic level was first brought to my attention by the Japanese with their Bio- Cord reactors where it was found that different polymer mixtures had a different effect on the BOD of the liquid that they were addressing.

I have witnessed this effect a number of times with different collection substrates so it is important that growers be cognitive that sometimes using the wrong product can produce different results. Worth noting is that all new plastic substrates should be seasoned before first use to maximize there abilities, as all new plastics leach a certain amount of gasses when first produced.

This is also very true in mussel culture however one of the most important underlying factors with this species is surface area for bysal attachment or maximum larval collection.

Currently the standard in the industry for collection substrate is either new or used polyethylene rope. The well used rope is the more sought after due to the increased roughness which adds to the surface area. There are machines now available that will fracture the outer strands of new rope to give it the attributes of used rope

Artificial Seaweed was developed by the Japanese more than a decade ago that due to its very high surface area allows up to (as reported by growers ) 50 times more larval collection per section then used rope. The only caveat is that with so much surface area one has to be more exact on the deployment time in that it will also act as a collector for other micro-organisms as well.

The cost per length is certainly higher than rope however it is not 50 times more and when you add in the reduced labor of pulling one rope vs 50 it is very significant and therefore much more efficient. It can be used either in a single or continuous format and has been used with very good success in the more progressive mussel growing regions.

When it comes to Mussel Socking used in single dropper applications or center core rope in continuous methods, the structure and mix of polymers is equally as important. It is surface area that is without doubt the biggest factor and when you compare what has been done globally you begin to see a trend of preventive measures to prevent fall off that if the focus had been on base surface area and proper seed stocking density that these preventative measures would probably not be required.

The New Zealand mussel industry is well known for their efficiency and mechanization and they were the first to understand the requirements of surface area for their operations. Working with a regional rope manufacture they developed a trademark Christmas Tree Rope as well as a Super Looped Rope that allows maximum harvest yield in a continuous application.

Using this as a base line, new single dropper socking has been developed that match or exceed the surface area that has been set by the Christmas Tree Rope.

What is interesting and very real in all of this discussion is that the regions that developed new technology seemed to embrace change and invest in equipment to increase their overall efficiency.

It is for this reason combined with the lack of adaptation to change by the majority of growers that we see the difference between those that are making money on a long term annual basis and those that are just getting by.

In conclusion, the answers are there for those that want them and are willing to be open minded enough towards change. If treated like a business the growing of shellfish is exactly that a business that can be quite profitable. More information and pictures of the proceeding substrates and materials can be viewed throughout the site or for those that wish I may be reached at don@fukuina.com for questions and comments.




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Email: kate@fukuina.com or don@bishopaquatic.com

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