Multi-Species Marine Traps
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Fukui's Monthly News Letter
Mussel culture basics (part 1)
The famous Vince Lombardi, former coach of the Green Bay Packers Football Club and icon to management theory training, would start each training camp for both his veteran and rookie players with the same statement.
Holding up a football he would say: "Gentlemen, this is a football". While this may sound a little simplistic, it drove home the point of sticking to the basics. Once the basics were drilled over and over again, Lombardi would then start building with enhancements that produced results.
In the shellfish industry, we could use a lot more of Lombardi's approach because once you know the basics everything else will fall into place.
From the questions we get asked regularly on the dynamics and use of mussel growout gear, it's clear that, especially in developing areas, there's a need for more basic information.
So in the words of Mr. Lombardi: "Ladies and Gentlemen, this is a mussel!"
In this column, I will explain the basics of seed. Part II of mussel culture basics will discuss: socking, equipment, harvesting and processing. If you look at the flow chart on the next page, you can see how each of these basic elements differs when put together in the "big picture", the mussel culture process.
There are two ways to acquire seed: hatchery production or wild collection.
Hatchery-based production has the advantage of consistent genetics and controlled development cycles. This is important in areas where there is a mixture of desirable and undesirable species. It also makes a difference in climates that allow only a mid to late summer spawn. The ability to introduce an animal spawned in the winter for immediate spring deployment can cut as much as six months or more off its complete growout-to-market-size cycle.
The only challenge is that once mussel larvae are hatched they need to be held in a nursery until the optimum size for socking (½" to ¾") in smaller mesh pepper seed socking is reached. Since mussels are healthy eaters the cost of feeding them during the nursery stage can add a lot to the growers' seed cost.
Nevertheless, the cost of hatchery seed averages between 15¢ to 22¢ (US) per pound.
Wild seed collection is carried out by deploying collectors down-current of wild mussel colonies. Depending on the area, larval production is, in general, caused by accumulation of food ingestion and temperature change. In the northeastern part of North America, once the water reaches 10C or 50F mussels will generally spawn, though there are instances of spawning at much lower temperatures.
The larvae will usually follow the current flow. Depending on wind conditions, best collection sites can be identified in advance by sample collection or local knowledge.
Collectors usually consist of used rope (trap warp) or new rope. The newer fuzz ropes or artificial seaweed, which has been in the market for about five years, can greatly enhance collection techniques with some reports of artificial seaweed collecting at a seed-per-foot rate that is 50 times more than that of rope.
Deployment of collectors is in single droppers of 6' to 15' dependent on the site depth and stratification of larval density. In some areas continuous collectors are deployed, which, when combined with mechanical stripping equipment, reduce labour cost and increase yields significantly.
Again, varying by site, collectors are normally harvested once the shell size is large enough to be socked, or when the timing of the socking best suits the grower.
The downsides to wild collection are possible predation from ducks or starfish and undesirable species or secondary set.
Unfortunately, the data with respect to the actual cost per pound of wild seed is inconsistent because of different reporting methods and that all related time and equipment cost is not taken into account. I have heard claims of 5¢ to 20¢ (US) per pound. The most naive statement I have heard is that wild seed is free! Sorry, but equipment and time are not free.
Once the seed has been grown to its desired size, it is harvested and then graded to increase the efficiency of seed conversion and to consistently match the seed size to the mesh size of the socking. Seed grading has still not been recognized in a lot of areas. Where it is practiced, however, there is a much more efficient husbandry format with higher yields and less labour.
Stay tuned for part 2.
Contact Don Bishop at:
Fukui North America
PO Box 669
110-B Bonnechere St.W.
Eganville, Ontario K0J 1T0
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