5.1 Determining minimal biomass
5.2 Determination of the cutting periods
5.3 Control of harvesting practices
5.4 Substratum maintenance and improvement
It is essential to conserve a minimal biomass to ensure stock regeneration after each harvest. After the Fucaceae harvest, however, seaweed fishermen believe that they have left the littoral completely denuded.
To obtain an objective view of the impact of the harvest on a stock, a study was made of exploited zones and also adjacent unexploited control zones. The study showed that only 95 percent of the exploited zones had been harvested, leaving at least 5 percent of the original biomass. The obvious explanation is that it would be a waste of time to collect all the seaweed from rocks that are always covered by a thick seaweed growth.
Whatever the seaweed fishermen may say, the littoral is never entirely exploited. There are areas where harvesting is forbidden, where seaweed is scarce or access difficult or impossible.
A portion of the biomass is therefore always preserved. We do not know if it is sufficient to renew the stock or even what minimal amount of the biomass is needed for stock restoration. Have algologists and phyto-sociologists found answers to these questions?
A few tufts left on the rocks cannot repopulate the shores. Recolonization is accomplished by sexual reproduction when fertilized female gametes are implanted on the bare substratum.
A minimal biomass able to produce gametes is therefore a requisite for repopulation. Because there is no record of a disappearance or rarification of the resource, it can be assumed that the minimal biomass has always been preserved, even if undefined, throughout the history of seaweed exploitation.
The Applied Algology Department of the I.S.T.P.M. recently determined a yield quota for Laminaria, limiting the maximum harvest on the North Brittany coast to 40,000 tons of fresh seaweed. Although study of minimal biomass has just begun, they suggest that harvests surpassing this limit might impede resource renewal.
Does this scientific view contradict that of seaweed harvesters? The seaweed harvester is both peasant and sailor and understands farming. He understands that there is no spontaneous generation; that no seaweed will grow if the coasts are truly left bare. For him, the exploitation of a seaweed bed and of a prairie are comparable. The concept of resource conservation exists for the harvester but is interpreted differently.
The possibilities of stock regeneration seem infinite. "Even when everything is cut, it grows back" they say. "Even the farmer cuts the hay every year". The first statement is based on the idea that the tendril remaining after the harvest is enough to allow the plant to grow again, but this assertion is false. The growth zone is located at the junction of the frond and the stipe in Laminaria, and is apical in Fucaceae.
The parallel drawn between land and sea leads to the belief that annual harvesting actually maintains the seaweed bed, encouraging growth, and that unexploited seaweed beds may be lost, like fallow land gone to seed.
Although biologically unsound, the seaweed harvester's understanding of resource renewal led to the gradual adoption of measures intended to ensure rational resource exploitation. The question is whether these measures have had a positive impact on exploitation or have simply provided a framework for its management.
To answer this question we will first examine existing measures as a whole. They can be divided into the following four groups:
a) cutting period and age at harvest;
b) harvesting methods;
c) maintenance and improvement of the substratum; and
d) shore maintenance.
5.2.1 Seaweed maturity
5.2.2 Perception of need - inserting the harvest in the annual work calendar
5.2.3 Cutting periods
5.2.4 Exploitation rotation
The determination of the cutting periods responds to biological and also social imperatives.
There exists two concepts of seaweed maturity: that of the scientist and that of the seaweed harvester.
5.2.1.1 The viewpoint of the population dynamics specialist
The population dynamics specialist can use models combining natural mortality and weight increase to define the moment at which the population reaches its maximum weight. By varying age at first catch and effort, he determines optimal exploitation conditions. In this case, however, the fundamental difference between the plan and animal worlds should be noted. For seaweeds, negative growth is normal. It appears at two levels, first over an annual period and then over the life span of the seaweed (about 5 years for Laminaria).
Each year, after the emission of spores, the plant tissues which held them are disorganized. They are dilacerated by the agitation of the sea, causing apical wear. The leaf is broken and weight is lost.
Moreover, while the stipe continues to grow, the leaf reaches its maximum length by about the third year. During the third and fourth years, apical wear overcomes growth and size decreases progressively.
Therefore the plan reaches maximum weight during the third year. It is important to learn whether this is also true of cohorts. This, however, requires data on natural mortality not currently available, and this aspect of the study could not be pursued.
Even when growth and mortality parameters are known, they apply to the given area only. They vary considerably depending on where the seaweed is grown:
a) submerged or exposed zone;
b) depth;
c) exposure (wave-beaten of sheltered mode);
d) amount of sunshine received; and
e) hydrodynamism (currents).
Even for the same population these factors vary, demonstrating how difficult it is to obtain a global view of biological phenomena.
5.2.1.2 The viewpoint of the seaweed harvester
The seaweed fisherman's perception of these phenomena is different. For him, the concept of seaweed maturity is not globalized but related to the plant's seasonal evolution, which he understands quite well.
As the season opens at the end of April, the first loads of Laminaria are not very dense. Most seaweed fishermen believe that Laminaria increase their weight by one-third during the course of the season, attaining maximum weight in July or August. The names they use to refer to the first seaweed harvested describe it as "tali moan" and "tali dister" (thin or skinny Laminaria), and "paper butum" (cigarette paper). "It loses all its weight drying" they say. "It shrivels away" and "it isn't ripe".
The mayors responsible for choosing harvest dates in each commune are aware of these problems. In 1904, the mayor Landunvez spoke of these plant resources in the following terms in a request that the Marine Minister modify regulations then in force:
Seaweed can certainly be compared to wild prairie grass; it has its periods of germination, of growth, of blossoming and maturity. Its harvest should be authorized only from the moment when this sea grass reaches a certain development, in April or early May.
Similar ideas are expressed by Mr. E. de Poulpiquet, mayor of Plouguerneau, in the preamble of an ordinance regulating seaweed harvesting in 1811:
Because it is of major importance to the community that the cutting or harvesting of black seaweed take place at a fixed date acceptable to the community and because this sea grass is most valuable when it has reached full maturity but deteriorates and loses all value if cut in any amount and at any season.....
Determination of the open season is not influenced by questions of maturity alone. Intemperate weather imposes other constraints.
5.2.2.1 Allowance for drying time
Because adequate sunshine is essential to the proper drying of seaweed, the open season must occur in the summer months.
5.2.2.2 Importance of plowing time
In the Upper Léon region, it was customary to open the seaweed harvest in February. This cutting was well timed to provide fertilizer for the fields about to be plowed. The objection that the seaweed harvested at this time was not fully developed was countered by the argument that the longer the seaweed grew, the greater the risk that it would be torn out by bad weather. According to this reasoning, waiting until May would result in waste of the resource.
Our own observation is that while Fucus are certainly present in the cast, they are not a major portion of it, even today when no harvest may take place for several years in certain areas. The management practice mentioned above is therefore based on faulty reasoning.
5.2.2.3 Other needs
On Batz Island, a harvest regularly took place in September to stock fuel for the winter.
5.2.3.1 Opening the season
The Fucus harvest takes place in May when these seaweeds reach full development. The seaweed fishermen of Plouguerneau patiently awaited this time in order to offer a product of the highest quality, saying that local farmers were willing to wait and pay more for their product than buy lower priced seaweed elsewhere, earlier.
Ascophyllum reaches maturity near Michaelmas (29 September) and the season is extended to include that date. At Landéda in 1926, the harvest lasted from 17 June to 31 October. The season for Fucacaea was from 14 May to 17 July.
Soon after large-scale exploitation of lichen began off the coasts of Léon in about 1905, it was observed that lichen reached its optimum development in the summer. Dates for the open season were set accordingly.
Seaweed fishermen on the west coast of the Léon region were accustomed to beginning their harvest of Laminaria in mid-April; much sooner than in the Pagan region. Although they knew that the season began too early, and "Eun hanter re abred" (Too soon by half) became a local proverb, these fishermen resigned themselves to this early season in order to shorten the long period of winter inactivity.
Even an early season was an improvement over the previous time, when harvesting occurred throughout the year. It was not until after the war that plant maturity was taken into consideration and the opening date set at 15 April.
5.2.3.2 The length of the open season
Colbert's ordinance of 1681 officially adopts measures long in practice. These allowed each parish to choose the dates and the duration of the shoreweed harvest. These dates usually corresponded to saints' days, as in Porspoder in 1788, where "The seaweed harvest will begin on the Eve of Saint Mark's Day, 26 April, and end on Saint Jean's Day".
The "fabriciens", or parish officials, were careful to choose a date coinciding with a phase of the moon, and therefore a tide.
The review of regulations makes frequent reference to the insistence of certain politicians that these regulations be formulated by a central authority, either monarchic or republican. The last dispositions made before the reform of 1975 established April to June as the harvesting season for shoreweed. Figure 4 illustrates the evolution of the opening and closing dates of the shoreweed season.
The season has been extended during recent years; a relaxation of local discipline which reflects a loss of interest in these seaweeds.
On the other hand, more and more Laminaria are being harvested and the Laminaria season has been shortened. Harvesting was permitted year-round from 1853 until the 1920s, when the opening date was set in mid-April. While in theory the season ended on 31 December, harvesting ceases, for all intents and purposes, after 15 October, when bad weather makes drying too difficult. Some communes officially adopted this date. Moreover, many boats are laid up for the season at this time. The Merchant Marine counts only nine months of navigation per year for seaweed harvesters. It should nonetheless be mentioned that some communes, like Plouarzel and Landéda, decided to set two different dates for the opening of the Laminaria season. In 1954 they were as follows:
|
Communes |
Opening Date |
Closing Date |
|
|
Harvest at sea |
Harvest from shore |
||
|
Plouarzel |
15 March |
1 June |
1 October |
|
Landéda |
15 March |
1 May |
30 October |
Lichen are harvested in the summer only; the open season extending from June through September throughout the Léon region. Since 1975, the opening and closing dates have been established at the national level under the jurisdiction of the Director of Maritime Fisheries.
A plan is devised to exploit several sectors, one at a time. The usual practice is to exploit each sector once every two or three years, although this is not universal. In the case of Laminaria, seaweed harvesters understand that the young plants left after each harvest require about two years to develop fully, and will simply shift harvest activity to another sector if the seaweed they find are not sufficiently developed to make harvesting worthwhile. Stocks were large enough to permit this rotation. Average production for a traditional seaweed harvester was approximately 30 tons of dried Laminaria, or 150 tons wet. Based on an average density of 15-20 kg per m2, one boat requires one hectare per year, which is a relatively small area on the sea.
In the Pagan region, where seaweed harvesters are allotted a family plot for the shoreweed harvest, competition is no problem. The harvester often reserved half of his large plot for the following year, resulting in a bi-annual rotation, or even three or four year rotation in places where seaweed grew slowly.
It can be stated that the practice of seaweed rotation exists but that its application is limited.
Resource conservation may also be accomplished by regulation of effort (tools, labour).
Manpower is sometimes strictly regulated. Each unit is assigned a quota of labourers. A municipal ordinance at Landéda in 1875 stated:
Unless a household is larger, no more than five persons may accompany each horse. No more than eight people may accompany each boat or cart, and all shall be residents of the commune.
5.3.2.1 Tearing versus cutting
Only cutting tools are permitted, and those which tear out seaweed are prohibited. Seaweed harvesters still believe that the roots are able to regenerate new plants. There are, however, isolated cases of the use of prohibited tools.
"Rastell-houarn" is a common iron garden rake, different from the wooden garden rake called "rastell-an-tevenn" or "rastell-vehan". It may be taken to the shore to gather driftweed but is prohibited when used to pull black seaweed from nearby rocks to be added to driftweed to increase its value. At Landéda, this practice is referred to as "skraba bleo war a c'herreg", or "combing the hair of the rocks".
"Krog-sillad" is a tool formed by a very long handle (3 to 4 metres) and a metal part made of three to five teeth perpendicular to the handle. Its name may vary by region; it is called "krog sillad" in the Pagan region, "krog-bad" or "krog-soun" in Porspoder and "krog-dragi" in Batz. This tool is legally used to gather driftweed which has not yet reached the shore. It use is prohibited when it is turned like a corkscrew to wind Laminaria around it and then pulled to tear them from their roots. If this practice was once wide-spread, it is because it seemed advantageous. Prohibition of seaweed tearing raises the interesting question of which method, cutting or tearing, is best adapted to the rational exploitation of marine plant stocks.
This question was considered as early as 1772, when tearing was permitted on the recommendation of three members of the Academy of Sciences, who concluded that "this plant, when cut by sickle, as advised by Article Four of the Declaration of 1731, does not reproduce until the rotting root detaches itself from the rock, whereas after tearing out, filaments remain which reproduce it the following year."
In 1838, Pinchon, De Blois and DeLannigou, of the agricultural society of Morlaix, sought a solution to this problem. They had an experiment conducted by an "intelligent sailor" who reported that "the torn plant grew back larger and more quickly than the cut plant."
Perez (1969) undertook experiments on Laminaria digitata at Porspoder. He chose two zones of equal area (150 m2) equally rich in seaweed. The Laminaria were harvested by cutting in one zone and by tearing in the other. Perez concluded that "cutting as commonly practised (on the stipe) presents no advantage over tearing, since a cut zone and a torn zone are repopulated at the same density and speed."
Furthermore, tearing is more profitable for the fisherman, adding the weight of the stipe to that of the leaf. The problem of cutting versus tearing was evaded in 1971 when the professional seaweed fleet was mechanized. The 75 boats operating off the coasts of Finistère and the Côtes-du-Nord are equipped with hydraulic scoubidous.
We made a further effort to determine if either method had an effect on size at first catch. Samples examined showed that in both cases, plants were harvested at 70-80 cm or about 2 years of age, a point of low fertility.
5.3.2.2 Prohibited uses of certain tools
Each of the seaweed fisherman's tools is intended for a specific use. They can, however, be used in uncustomary ways which are prohibited.
The "guillotine": The guillotine is normally used to cut Laminaria. In 1855, the mayor of Lampaul-Ploudalmézeau, in response to some residents' protests, stated that "The use of long-handled sickles, from above, to cut shoreweed under water at high tide, is prohibited, in order to prevent degradation of the seaweed bed." Using the guillotine in this fashion allowed some harvesters, ignoring the regulation, to begin their harvest at high tide and well before the others. Their boats would be almost full at mid-tide when the other residents arrived on shore with their teams.
The rastell-aod or rastell-vor: The rastell-aod or rastell-vor is a tool commonly used to trap and collect floating seaweed. Although it is meant to be used from the beach, some fishermen in the Haut-Léon used it from their boats, preventing seaweed from drifting towards the harvesters waiting on shore.
As we have seen, trapping seaweed offshore is forbidden in some parts of the Pagan region. Use of the rastell-aod is forbidden where seaweed may be gathered only when it has reached dry land.
This tool is certainly advantageous for harvesting driftweed. In order to equalize harvesting capacity on Batz Island, the few men remaining are denied the use of the rastell-aod when fishermen are absent serving in the army and their wives are obliged to harvest the seaweed.
Specific and efficient action has been taken to avoid resource waste. In many communes, for instance, the practice of "bijin-diro" is forbidden. This practice consists of cutting as much seaweed as possible while the tide is out, relying on the incoming tide and a favourable wind to carry it to shore. If the wind drops or turns, the seaweed is scattered towards the open sea. Bottom weed sinks and is lost. The risk involved is great and prohibition of this practice well-founded.
5.4.1 Extending the biotope
5.4.2 Protecting the biotope
5.4.3 Eliminating parasites
5.4.4 Prohibited zones
5.4.5 Other direct measures
At the end of the 19th century the municipality of Plouguerneau tried to extend the rocky portion of the coast by covering sanded areas with flat stones and blocks, thereby increasing the potential seaweed bed. This seems to be the only effort of this kind ever made in Brittany, although it is a common practice in Wales and Ireland.
Our field inquiry established that, although this effort has not been repeated elsewhere, seaweed fishermen are aware of the possibility of extending the seaweed bed, just as they observe that seaweed quickly covers the pilings to which they moor their boats.
"Anyone fishing for crustaceans, abalone or other shellfish along the coastline of the commune is required to return to their original position any rocks displaced by their activity" (Plouguerneau, 1925).
This regulation is justified by two negative effects which the over-turning of rocks has upon the biotope:
- The top of the rock is covered by attached animals and vegetation. If the top of the rock is turned over into the bottom sediment, they are deprived of light and water circulation and hence of oxygen. The organisms die and then decay, still attached to the rock.- Consequently, the smooth bottom of the rock, once exposed, is slow to acquire a new algal covering. A balanced (climax) population is achieved only after several stages of bacterial and diatomic interaction, often requiring several years (Huve, 1969).
Seaweed productivity is unavoidably affected by the displacement of the rocks. Municipal ordinances prohibiting rock displacement by seaweed harvesters and shellfish fishermen show that coastal populations recognize the need for such regulation.
Laminaria harvesters have always tried to eliminate competitive species present in the seaweed bed. Although it is an annual, Saccorhezia bulbosa has always been the most troublesome of these because of its huge frond which blocks light penetration. One of the author's uncles likens elimination of this plant to underwater weeding.
There seems to be no record or memory of any specific case of reserved or prohibited zones. At Plonguerneau in 1890, a municipal ordinance sets dates for the seaweed harvest and reminds the population that harvesting is allowed in authorized areas only. Our research found no other mention of the existence of prohibited zones suggested by this ordinance.
It should, nonetheless, be mentioned that harvesting was prohibited on docks, jetties and in other port areas. This prohibition was intended to avoid damage to port facilities rather than for management purposes.
The harvest of Zostera marina found on sandy shores is an important activity along the entire west coast of France. Competition arose between fishermen and seaweed harvesters in the Portsall region, where the fishermen's wives dug in the sand for Nephtys sp., which their husbands use as bait for pollock. Because their digging destroyed seaweed beds, seaweed fishermen in 1926 successfully obtained a regulation restricting the Nephtys hunters' access to the beds. This is an example of action taken to protect the seaweed industry.
