In my last column I discussed my trip to Norway observing mussel farms and polyculture applications of mussel and salmon growout. This past August, Dr. John Bonardelli and I returned to make presentations at the European Aquaculture Society (EAS) conference and to attend AquaNor 2001. Having experienced this beautiful country in February was great in itself, but to experience it again in August in the same year was a real treat.
The presentations that John and I gave were on the engineering, biology, and commercialization, for profit, of polyculture applications. There was a wide variety of presentations from all over Europe and some Middle-eastern countries, with a very broad topic range, and it was very interesting to see the diversity of information from the many countries involved. In contrast, most conferences in North America have great information flow, but are usually limited to opinions from a handful of countries.
Our presentations on polyculture were well received, since we were asked to focus on the business aspect, or the dollars and sense side of the industry. With the current low price of salmon, we were able to get a great deal of attention from the salmon growers when we suggested placing mussel longlines around the perimeter of the salmon grow-out lease site. We demonstrated how, in one grow-out cycle for mussels, you could expect a revenue of approximately 1,800,000 Kr (US$ 200,000) from 1 hectare (2.5 acres). (In a future column I will discuss more on polyculture applications.)
In February John and I spent most of our time in the north part of the country. This time, we traveled more to the central and south regions. Unfortunately the southern part of Norway's mussel industry has been plagued with toxic algae over the last few years, which has severely limited harvest, as well as making supply of market products very unpredictable. The northern farms are not nearly as affected by this issue, but methods to overcome this problem will have to be developed if the industry is going to reach the set objectives. Different husbandry practices are a possible solution, as well as relocation of sites, and algae defense or detoxification systems.
Besides the grid-like parallel longlines that I described in my last column, there are also single surface longlines, common in North America, and double surface longlines similar to those used in New Zealand.
Continuous tape-type webbing that is both a collector and primary grow-out substrate is in use in many locations. As well, the new ladder system offered by Xplora is undergoing testing at a few mussel sites. There are also numerous farms using single dropper methods.
I mentioned in my earlier column that in general, the husbandry methods may be efficient from a handling and mechanization process, however from an animal management perspective and growing efficiency, there are a number of downfalls.
From my travels and meetings with growers over the years, I have developed, through observation, a sense of best management practices that through trial and error, have set a standard for overall efficiency. The goal of overall growth cycle management is to manage the production from larval collection through harvest, so as to reduce the growout cycle and increase the yield, and to create a consistent product to market.
In most cases when you use collectors as a primary grow-out substrat, you end up with a wide variation in size at harvest. This is due in part to the fact that some animals grow faster than others, and as a result will consume more of the available food than animals that grow more slowly and are directly adjacent to them on the substrate. The result of this natural variability is that by the time of first harvest, 18 to 30 months depending on latitude, there will have been a number of animals that grew very quickly, which results in overcrowding of the substrate and subsequent fall off. There will also have been a large number of mussels that are undersized due to lack of food caused by competition. The result at the time of harvest is that only 40-60% of the original set are grown to market size, leading to additional labour, cost and grow-out time for the rest of the undersized mussels.
The other significant challenge to mussels grown with this husbandry practice is inventory control. Having animals of so many different sizes does not allow for adequate stock assessment in the water, nor does it allow you to plan reliable harvest schedules.
In contrast to this there are growers who collect seed and, depending on site specific growth rate, they will strip and sort the seed as soon as they reach a minimum size, which can be anywhere from 10-35mm in length, and then re-deploy mussels within engineered or density controlled socking, which match seed size with mesh opening and stocking density. This allows for animals of similar size to grow evenly without over-crowding. The result of this is reduced grow-out time and almost 90% to market efficiency at time of harvest.
Norwegian growers are currently getting higher income than North American growers for their product, due primarily to demand. Most product enters the EU in bulk, and is then redistributed to direct market distribution systems.
While there are a large number of independent farms, there are already a number of companies that are consolidating for supply and growth. The success of the salmon industry and its experience in this area will no doubt influence the growth of the shellfish sector.