1 This report presents an assessment carried out by Environment & Resource Technology Ltd of the littoral seaweed resource and management options in the Western Isles. The work was commissioned by Scottish Natural Heritage and Western Isles Island Council, with partial funding from LEADER (the Western Isles and Skye and Lochalsh LEADER Programme), in response to the possible future increased exploitation of the resource and concern that this should be conducted in a sustainable manner.
2 A programme of field surveys in the Western Isles was carried out from 2-13 September 1994. A number of sites surveyed during the 1940s were revisited with the aim of re-evaluating the size of the Ascophyllum nodosum resource.
The distribution and abundance of other potentially exploitable seaweeds (Porphyra umbilicalis, Mastocarpus stellatus, Chondrus crispus and Palmaria palmata) was also assessed.
3 Densities of Ascophyllum for individual sites varied between 4.60 and 24.07 kg/m2. Total tonnages were greatest for survey areas in the Uists, particularly Loch Maddy (19,587 t) and Loch Eport (13,572 t).
4 In most areas, results from sites revisited were very similar to those of Walker (1947). The greatest difference appeared in the results for Loch Maddy, where the estimated total biomass was only 49% of that from the earlier survey. The figure obtained in the present survey is more consistent with historical harvest data.
5 Biomass figures from Walker's (1945-1946) reports for the areas not re-surveyed in the present study were used to extrapolate total Ascophyllum resource estimates for each island. The estimated total standing crop for the Western Isles is 107,552 t.
6 Porphyra spp and the carragheen species (C. crispus and M. stellatus) are widely distributed in the Western Isles, but only in relatively small quantities. They are locally abundant at some sites but the distribution is too patchy for harvesting apart from on a very small scale.
7 Ascophyllum harvesting practices and management strategies are reviewed for the Western Isles, Orkney, Ireland, France, Norway, Iceland and Canada.
8 At present, approximately 3,000-4,000 t (wet) of Ascophyllum per annum is sold to Kelco from the Uists via a local haulage company. Approximately seven self employed harvesters are involved on a regular basis, with harvesting sites located around Benbecula and South Uist. A small amount is harvested in Lewis by Tavay Organic Products Ltd.
9 Harvesting practices in the Western Isles have remained more-or-less the same for over 100 years. Seaweed (Ascophyllum and any Fucus spp mixed with it) is cut by hand during low tide using a sickle. Cutting height is variable and approximately 15 cm on average. The reharvest interval is 3-4 years.
10 Similar hand cutting methods are used to at least some extent in all of the other Ascophyllum harvesting countries. Mechanised harvesting, using barges which operate at high tide, is also used in Norway, Canada and Iceland.
11 Regulations governing harvesting practices exist only in France, where strict twice-yearly cutting seasons are set, and in Canada, where Federal Government regulations control use of cutting equipment and set a minimum cutting height. The Canadian Federal Department of Fisheries also initiates biological research relevant to resource management.
12 Information on the C. crispus and M. stellatus harvesting industries is reviewed for Ireland, France, Canada and the USA. Palmaria palmata and Porphyra spp harvesting are also discussed briefly.
13 Information on the effects of seaweed harvesting is considered in relation to the recovery of the species population being harvested, direct impacts on other fauna and flora, and indirect effects on the wider ecosystem.
14 The immediate effects of Ascophyllum harvesting on the target population have been studied in Canada. In practice, harvesting does not leave the entire population cropped to an even height. Mechanical harvesting left longer stumps, on average, than hand harvesting using a cutter rake.
15 Recovery of a harvested Ascophyllum population is by regrowth of cropped plants and by recolonisation by germlings. The latter method is more important where entire plants have been removed, and is much slower, often allowing colonisation by opportunistic species and initiating an ecological succession.
16 The length of stump left after harvesting is crucial to recovery rates since regrowth depends on the number of uncut basal shoots and the potential for lateral branching of stumps. Rate of regrowth also depends on the age structure of the population, the extent and pattern of branching, the presence or absence of grazers and the degree of exposure of the shore.
17 The time taken for recovery of commercially harvested Chondrus beds in Canada depends on the type and severity of harvesting methods used, and varies between six and 18 months.
18 Removal of the Ascophyllum canopy through harvesting has a direct effect on numerous associated organisms. Evidence exists that effects may persist to some extent for several years, but more research is needed on this subject.
19 Indirect effects of seaweed harvesting may possibly result from the loss of algal productivity to the ecosystem. No such effects have been demonstrated, however, and current knowledge of energy pathways is insufficient to allow firm conclusions to be drawn.
20 Any management strategy for the Ascophyllum harvesting industry must provide for the protection of both the resource itself and its associated ecosystems. Sustainable harvesting practices are those which can be continued indefinitely without reducing yield, and which allow for recovery of associated species populations adequate to maintain their stability.
21 At present there is insufficient specific information on the autecology of Ascophyllum in the Western Isles, and on impacts of its harvesting on non-target species generally, to allow the formulation of comprehensive management plans.
22 A demonstration project is proposed to provide relevant information on the effects of Ascophyllum harvesting in the Western Isles.
23 Management guidelines are presented based on current knowledge.
24 Current and historical harvesting of seaweed in the Western Isles is reviewed. In the twentieth century this has been based almost exclusively on sales to the alginate industry and to one company within this market (Kelco, formerly AIL).
25 The harvesting of Ascophyllum for alginate production reached a peak in the 1970s when three drying plants were operational in the Western Isles (one in Lewis and two in the Uists). Together the Uist plants were processing ca 12,000 t (wet)/year weed at this time. Now a quarter to a third of this amount (all from the Uists and Benbecula) is transported unprocessed to Kelco's two alginate production factories in Scotland.
26 Tangle has also traditionally been collected for sale to the alginate industry (and to a lesser extent for local use as a fertiliser). Kelco currently purchases ca 220 t/year of air-dried tangle from the Western Isles.
27 Tavay Organic Products Ltd based in Lewis harvest and process an unknown quantity of Ascophyllum for sale as a fertiliser/soil conditioner or as the base for such products.
28 Around 50-60 people on the Western Isles gain some form of revenue from seaweed. Of this total some 20-25 individuals are employed on a regular basis in connection with Kelco's and Tavay's exploitation of the Ascophyllum resource.
29 In 1995 a washing and milling plant will be established in Benbecula to treat Ascophyllum harvested for Kelco. A semi-automated system of tangle collection is also planned. These new developments should give a moderate boost to the amount of Ascophyllum and tangle sold to Kelco and to the number of those obtaining income from seaweed exploitation.
30 Total gross income from seaweed on the Western Isles is difficult to quantify accurately, given the lack of information on the Tavay operation. It has been estimated as between £270,000-£450,000 in 1994, but is probably towards the lower end of this range. Those cutting and collecting seaweed for Kelco receive about £80,000-£90,000 per annum at present.
31 The production of seaweed in the Western Isles/Scotland is shown to be a very low percentage of the total European harvest of brown algae, possibly less than 2%. Norway and France are the two major producers, but Ireland and Iceland also harvest more than Scotland.
32 The main markets for seaweed and seaweed products are reviewed. Phycocolloids represent by far the largest market for European seaweeds and will remain so for the foreseeable future. Alginate is the only phycocolloid of direct relevance to the Western Isles.
33 The alginate industry (Kelco) will continue to be the major buyer of Western Isles seaweed, at least in the short term. There are limited prospects of selling to alginate producers other than Kelco, and only a moderate increase in sales to Kelco can be realistically envisaged. There are evident dangers from such a heavy dependence on one sales outlet.
34 The strengths and weaknesses of the Western Isles seaweed industry are analysed along with the market opportunities and threats. A strategy is proposed which focuses on two aims:
a) to undertake a planned diversification into other markets for seaweed products;
b) to re-examine ways of adding value to seaweed supplied to the alginate industry yet remaining cost competitive.
35 Aside from the alginate industry, all the markets for seaweed which are reviewed in this report are low volume; specialist food products (eg health foods, novelty foods) and cosmetics are the two main high value areas which are highlighted as market opportunities for diversification.
36 A review of seaweed processing potential on the Western Isles is recommended, focusing on process innovation, energy efficiency, and integration of processing for the alginate and other markets.
37 Further recommendations include the integration of seaweed development within local/regional development initiatives and the provision of support in areas where seaweed businesses tend to fall short (R&D, quality assurance/control and marketing).
38 Allowing for a minimum three-year regeneration period to ensure sustainability, the upper limit for Ascophyllum exploitation in the Western Isles is in the region of 37,000 t (wet)/year. This figure would be lower if designated areas were left unharvested as recommended in this report.
39 The resource potential exists for a sustainable expansion of the industry in line with the principal market opportunities outlined in this study, ie a moderate increase in the current level of supply to the alginate industry and the exploitation of limited amounts of seaweed for higher value, low volume markets.
40 The scale of red seaweed collection in the Western Isles is currently very small. The resource potential for sustainable growth in harvesting cannot be estimated at present, although there may be market opportunities in high value/low volume sectors which would allow modest expansion of this activity.
