Industry takes stock
Production statistics do little to illuminate the true status of the sector
THE shellfish industry takes stock of how it is collectively performing when the official Marine Scotland Cultivated Shellfish Production Survey is published in June (bit.ly/Scottishshellfish2019). The year on year (2017/2018) production figures showed a decline for all species, whether for the table or for on-growing. Does this indicate that 2018 was a poor year? After all, we had a long and exceptionally hot summer, with some areas unable to harvest due to natural algal bloom issues.
Or was the decline more to do with the successful 2017 production year and higher than average output figures?
The figures actually reflect the performance of the shellfish seed which was placed into the water two or three years before, and the fact that shellfish production follows natural conditions – far more than allowed by an accountant’s spread sheet!
Undoubtedly, there continue to be a range of challenges for shellfish growers, the greatest being natural variability of both seed and the growing conditions.
A more balanced view of the statistics requires a longer time frame and a basic understanding of key influences.
Scottish oysters
During 2018 Scotland continued to maintain the existing approved zone status for all notifiable shellfish diseases.
In terms of oysters, all seed stock can only be supplied by hatcheries approved as disease free, and any movement of part grown stock must be assessed as part of a biosecurity plan to limit any potential disease spread risk.
To date, such a system has ensured that oyster herpes virus has remained outwith Scotland. Caution in securing seed supplies is wholly warranted as infected stock has the potential to cause extremely high levels of mortality in juvenile Pacific oyster.
In areas of the North Sea, France, England, Northern Ireland and Ireland, such losses have to be made up by inputting vastly more seed. This ensures adequate survival to achieve sufficient outputs for the market.
Such a seed hungry production system has significant additional costs, which would be difficult to sustain in Scotland. Seed costs are higher here because we only source from disease free suppliers; but the environmental considerations make this a worthwhile exercise.
Growers will plan ahead for their seed requirements and, typically, there are no hatchery shortages.
However, if exceptional, natural on-growing losses occur due to weather conditions, there can be limited opportunities to make up shortfalls by supply of part grown stock from other disease free areas.
Hence, we can see variability in market outputs for a wide range of economic and production reasons.
Strength of demand
It is worth pointing out that the production survey does not reference market conditions or desirability of Scottish production, other than
“There continue to be a range of challenges for growers, the greatest being natural variability of both seed ons’” and growing conditi
individual commodity prices.
There has never been stronger demand for Scottish oysters within all the market sectorsfrom farm gate sales to supermarkets.
Unfortunately, we are not an industry where the supply tap can be turned on and off in an instant. No one is going to enter oyster farming as a business opportunity on a gold-rush basis.
The businesses we have remain committed to producing high quality oysters for an appreciative customer base.
Obviously, the consumer network is growing and so we will hope to see our producers progressively expanding production and encouraging new entrants into the industry to ensure the knowledge, experience and legacy of producing sustainable shellfish in Scottish lochs is maintained.
For reassurance, the combined Pacific oyster production figures for the table and for on-growing amounted to almost 8.27 million shells in 2018, more or less the same level since 2015.
Going native
The Pacific oyster is the bedrock of the Scottish industry and without such production it would be difficult to perceive that native oyster (Ostrea edulis) cultivation would have been sustained in recent years.
Again, the shellfish production statistics do little to illuminate the true status of this sector – or the development opportunities which may be emerging.
Much is currently being made of the potential for native oyster habitat regeneration, and the desired re-emergence of the species over large areas of the North Sea, English Channel and beyond.
There are a range of issues driving this interest and the recent Native Oyster Restoration Alliance (NORA) conference held in Edinburgh considered these (see Fish Farmer, July 2019).
From a Scottish cultivation perspective, native oysters have always been in the mix, but only commercially undertaken by a few producers due to the specialist nature of such production.
And disease free hatchery seed production can only be attempted on a small scale. With a long grow out period of around five years, and a tendency to be extremely sensitive to site cultivation conditions, numbers within the low hundreds of thousands, are currently produced for the table.
The native oyster market attracts a premium price from connoisseurs, which makes maintaining a cultivation business as a stand-alone precarious, but with potential rewards.
It is worth noting that despite the price premium received, production outputs for the table have progressively declined since 2009.
On-growing (part grown stock in the water) outputs have varied dramatically from nothing to more than a million shells, and reflect, in part, the availability of batches of hatchery seed and success in keeping them alive.
Are we beginning to see stock for on-growing produced by cultivation substitute for shells destined for the table market, as greater demand is building up from restoration projects?
Whether this occurs will ultimately depend on the success of restoration projects and the ideology driving them; the native oyster is a Biodiversity Action Plan species with international conservation objectives.
Self-recruitment may be a goal for some of these restoration projects, hence their success may remove the requirement for cultivated stock to augment the established populations.
On the other hand, in many current projects the regenerated native oyster habitat is not likely to become subject to harvesting and so these schemes are unlikely to supply the table market as a food resource.
There is also the question of how climate change resilient the native oyster will actually be. At what point will it be decided that chasing a rewilding dream in an environment that has become hostile to some of our native species is a good use of public resources?
Natural balance
In a Scottish context, there is another factor in supplying restoration projects with native oysters.
Many areas where restoration is being considered are non-approved for disease purposes. The principal disease agent of native oyster is Bonamia spp., which Scotland has largely managed to prevent spreading in the wild.
If restoration projects wish to relay stock which is partly resistant or has been challenged and survived Bonamia, this is not a product we can produce in Scotland as we are disease free.
Therefore, Scottish shellfish producers or approved hatcheries will be restricted to those restoration projects requiring unchallenged stock.
Ironically, the farming of Pacific oysters and the need for seed is not only assisting with the viability of hatcheries and allowing niche species such as the native oyster to be supplied, but also helping create suitable habitat for the natives.
Most well-established Pacific oyster farm sites will report that native oysters have taken up residence around and often under their trestles on the foreshore.
Presumably, they settle on to the course substrate often containing empty shells- with juveniles originating from the small pockets of wild stock we can still find, principally on the west coast.
Maintaining biodiversity in Scotland may well be best achieved by en
suring our scattered small beds of native oysters remain undisturbed and protected from disease – a role which some of our shellfish cultivation businesses have been quietly undertaking in many locations.
Such incidents of increased biodiversity associated with shellfish cultivation are not uncommon (we will be hearing more of the scientific evidence for this at this year’s conference), but difficult to quantify as a benefit to the nation when considering at face value annual shellfish production statistics.
Mussel production
In Scotland, volume production of shellfish is reliant on the blue mussel (and what we now know are a range of hybrids of the Mytilus spp.).
Seed supply is currently solely dependent on collection of ‘spat’ from the wild and natural selection for viability and growth characteristics.
Annual success of spat collection at individual sites has been the major factor impacting industry outputs- with combined production for the table and on-growing amounting to 9,000 tonnes in 2018, based on the official statistics.
In 2017, this was nearer 13,000 tonnes but that year was noted to be a highly productive year for seed at many locations around the Scottish coast.
The natural variability of spat abundance within and between years dependent on location means that many shellfish businesses must take a balanced view of the likely availability of this raw resource.
Resilience for any production business is based on the spreading of risk between inhouse spat collection and securing opportunities to buy spat in from other areas or sources.
The apparent fall in 2018 outputs is of significance as in 2009 the industry produced only 500 tonnes less than the current 7,000 tonnes for the table.
In the intervening years we have seen a major rise in the efficiency of businesses, considerable investment and larger sites established.
If the resilience of the mussel cultivation industry is based on seed supply, that is where we need to focus our efforts to ensure continued success and consistency of production.
We are not alone in Scotland in recognising that mussel seed supply is the cornerstone of the cultivation industry.
Various other countries in the northern hemisphere have found similar constraints in predicting mussel spat supply, and the health of the wild stocks upon which they are reliant for both fisheries and aquaculture. Finding NAEMO
That is relatively easy in this case! The North Atlantic and European Mussel Organisation (NAEMO) will hold its first meeting in Oban on October 30, hosted by the ASSG with support from Marine Scotland.
Last year’s ASSG conference was the catalyst for the formation of this group, led by Åsa Strand, who gave an interesting analysis of mussel stock issues in Sweden, and blue mussel stock dynamics in the northern hemisphere.
The conclusion was that no one organisation or international body had sufficient long-term evidence of the distribution or dynamics of the species.
The NAEMO meeting will be an opportunity to bring together a wide range of international researchers with an interest in this area.
ASSG conference 2019
Building the resilience of the Scottish shellfish cultivation industry is the overriding theme for this year’s event in Oban, from October 31 to November 1- a theme that fits well with the roles of our sponsors, Crown Estate Scotland and Marine Scotland.
On the first day, international experts will consider the suitability of bivalves for aquaculture production.
The various levels of consumer expectations, in terms of supply to the key market sectors, will be covered by UK industry leaders.
On the second day, the focus will be very much on industry development- covering deep water mussel cultivation in the Irish Sea, and also the scientific evaluation of the environmental benefits and biodiversity dividends associated with mussel longline systems.
There will also be an assessment of the community benefit arising from shellfish cultivation, including determining an acceptable overall scale of production within the coastal environment.
From a Scottish industry perspective, we will be focusing on the underlying requirement for hatchery seed supply to support oyster growers, against a background of disease and stock issues in other European countries.
And, of course, the conference will feature the Best Scottish Shellfish competition, sponsored by Highlands and Islands Enterprise, and the annual dinner on the evening of October 31plus outstanding seafood lunches on both days.
For the full programme of events, visit the ASSG website (www.assg.org.uk)
Dr Nick Lake is CEO of the Association of Scottish Shellfish Growers.