December 13. 1S94J 



NATURE 



16: 



The leading characteristics of French oyster culture are (i) 

 that the whole is under the regulation and supervision of the 

 State, concessions of ground being given to individuals or 

 companies {e.g. at about 30 francs the hectare at Arcachon) 

 for the purpose of forming oyster "pares"; (2) that certain 

 grounds are set aside or preserved as banks of breeding oysters 

 to supply the spat ; and (3) that the whole process of raising 

 the spat, and rearing and latlening the oyster, is not carried on 

 at one locality, but is subdivided and specialised, spat-production 

 taking place best at one locality, such as Arcachon, and fat- 

 tening for market at another, such as Marennes. 



Two species of oyster are cultivated. Osti-ea eJiilis, the ordi- 

 nary rounded flat oyster of northwest Europe ; and O. aiigulata, 

 the elongated Portuguese oyster. The latter, although increasing 

 in numbers in some places, and becoming of considerable com- 

 mercial importance, is not so highly thought of as is Ostrea 

 ediilis. 



There are now only two places on the coast of France where 

 spat is produced in sufficient quantity to be of commercial 

 importance. These are Auray, in the north, and Arcachon, in 

 the s juth, and these two localities supply all the other oyster 

 culture centres in France, and even export to other countries. 

 One merchant I met at Arcachon told me that he had already 

 sent eleven millions of oysters to London that season.' I 

 visited in all about ten different oyster-culture centres ; but as 

 several of these showed nothing special, they need not be 

 mentioned. The arrangements for the caplure and rearing of 

 spat were best seen at Arcachon, and for the further rearing 

 and the fattening of the adults at La Tremblade and Marennes 

 on the estuary of the Seudre. At .\rcachon I was fortunate in 

 enj )ying the hospitality of the excellent Biological Station, 

 which was established nearly thirty years ago by La Socicte 

 Scientifique d'Arcachon, and which was made use of by Paul 

 Bert in 1867 for his observations on the physiology of marine 

 animals. 



.'\rcachon presents remarkable facilities for the study 

 of shallow-water marine forms, and is of great interest to the 

 biologist, as well as to the ostreiculturist. Its vast inland sea 

 <lJassin d'Arcachon), which is about So kilom. in circumference, 

 contains at high tide about 15,000 hectares of area, and is, over 

 the greater number of the channels, about $ to 10 fathoms 

 in ilcpth, while two-thirds of the whole area dries at low tide, 

 in the middle of the "bassin," and north of the town of 

 .■\rcachon, is a small island. He des Oiseaux, and on the shores 

 of this, and on various other fiat sh.illow parts which are 

 expo.-ed at low tide, and which are called "cra.ssats," are 

 situated the oyster " pares." Some of these areas are reserved 

 by the State for the purpose of producing spat, a wise pre- 

 caution, although some of the parqueurs think the State reser- 

 vations unnecessary, as there are so many adult oysters over the 

 ground that plenty of spat is sure to be produced. Certainly 

 during the time of my visit, which was just when the free- 

 swimming embryos were settling down, the water over the 

 pares seemed to be swarming with them, and the spat was 

 making its appearance over all sorts of suitable submerged 

 objects. The summer of 1S93 **5, however, a particularly good 

 season, which the parqueurs attributed to the great heat. 

 Trobably calm weather and absence of rain during the critical 

 period when the young oysters are free-swimming, and then 

 settling down, h.as as much to do with a heavy fall of spat as 

 the actual temperature. 



The oyster reproduces at Arcachon between May and the 

 beginning of July, and the young animal leads a free swimming 

 existence for about a week before settling down as spat. The 

 paiqueurs examine carefully the condition of the spawn in the 

 old oyster, and at what they consider to be the proper time 

 (generally about the end of June) for catching the deposit of 

 spat, they place their "collectors" in position. It is of 

 importance that the collec.ors should not be put in the water 

 too soon, as they are liable to become coated with slime and 

 sediment, which will prevent the young oyster spat (" naissain ") 

 from adhering. The collectors are crates ("gabarets" or 

 "ruches") of earthenware tiles, coated with a limy cement 



' Two-year olds, measuring 5 to 6 cm. across, cost at the rate of ij fr.incii 

 fivr iooo,_ and somewhat older ones, measuring 6 10 7 cm., 25 francs per 1000. 

 These prices include packing and carriage as tar as Bordeaux, where they 

 meet tlic steamer. On an average only 1 per cent, die on the journey. From 

 the middle of March to the middle of .^pril is the best time to send young 

 oysters for stocking purposes to England. Before that it is liable to be too 

 culd in Eni^land, and later it is too hot in Arcachon for transportation to be 

 effected safely. 



NO. 1311, VOL. 51] 



which gives them a whitewashed appearance. The tiles are 

 like ordinary roofing tiles, about fourteen inches long by six 

 inches at one end and five at the oiher, and half an inch in 

 thickness. The cement with which they are coated is made of 

 lime mixed with sea-water and a certain amount of sand, so as 

 to form a creamy paste. Different proprietors use slightly 

 different proportions of lime and sand. The process of coating 

 (" chaulage") adds from one-sixteenth to one-eighth inch in 

 thickness to each side of the tile. It has to be done with 

 some care, so that the limy layer may be of the right nature, 

 sufficiently strong and adhesive, and yet readily detachable w hen 

 the time for "detroquage" comes, so that the young oysters 

 may be removed from the tiles without injury, and without 

 the necessity of breaking up the tiles, as used to be the case. 

 By the present method the little oysters and film of cement can 

 be flicked off rapidly by a skilled hand with a square-ended 

 knife, and the tiles preserved for use again the following year. 

 .■\ dozen or more millions of these tiles are probably employed 

 each year at Arcachon. The prepared tiles are arranged in 

 alternating rows lengthways and breadthways inside cases made 

 of strips of wood, so that the water may flow in readily between 

 and around them. The cases of collectors I measured were 

 about 6 feet x 2 feet and 3 feet in height, each holding 120 

 tiles arranged in ten layers. The alternating arrangement of 

 tne layers is intended to break up the currents of water as the 

 tide runs through the "ruche," form eddies, and so give the 

 young oysters a belter opportunity of affixing themselves to the 

 tiles. The tiles are all placed with the convex surface upwards, 

 as it ii very important that there should be as litile opportunity 

 as possible given for the collection of any fine sedimen; in 

 which the young spat might be smothered. The arrangement 

 of tiles above described is now considered the best at Arcachon. 

 Various other arrangements have been tried, and may be suited 

 to special conditions of bottom or depths of water. 



I was very fortunate in seeing some of the tiles just after the 

 young oyster spat had been deposited, and photographed such a tile 

 covered thickly with the minute amber-coloured specks. There 

 may be several hundred such young oysters on one side of a tile. 

 During my stay at Arcachon I found that the temperature of the 

 water varied from 74'F. tooverSo'F., and the specificgravity from 

 I 022 to I 024. However, it is known that no such high tempera- 

 tures are really required for spat production, since, e.^:, Captain 

 Dannevig has had an abundant deposit of spat in his pond near 

 Arendal in Norway, where the July temperature of the water 

 was only 63' F. To compare these with our own district, we 

 find that in the same week of July 1S93 'he water off the south 

 end of the Isle of Man was on the average about 60= F. with a 

 specific gravity ranging from I 025 to I 026, while shore pools 

 near the Biological Station at Port Erin, comparable as to ex- 

 posure with the oyster pares at .\rcachon, reached as hi^h a 

 temperature as 76' F. Dr. Bashford Dean ' and other authori- 

 ties state as their opinion, that a low specificgravity is necessary 

 for a good deposit of spat, but there is no unanimity on this point 

 amongst the practical men at Arcachon (some of whom are keen 

 observers, and are in the habit of taking the temperature and 

 specific gravity). 



After removal from the tiles, those young oysters which are 

 not sold to "cleveurs" away from .Vrcachon are kept for 

 another year or two in the pares. They are placed at first in 

 flat tiays having a floor and ltd of close galvanised wire netting, 

 of about half-inch mesh, and these tiays ("ambulances" or 

 "caisses ostreophiles") are placed between short posts in the 

 water on the oyster pare, so that the tide can run freely through 

 them, supplying the oysters with food and oxygen. They measure 

 about 6 feet by 4, and are 6 inches deep. They serve to keep 

 the young oyster, during the early period of its life, out of the 

 sediment, and they also protect it from its numerous natural 

 enemies, such as the starfishes and crabs, which manage to suck 

 or pick out the soft body, and whelks, such as Ftirfura, A/urex 

 and Nassa, which can bore a hole through the shell. The 

 ambulances are constantly looked after by the oyster men and 

 women, who come at low tide, when they are exposed, open the 

 lids, and pick over the contents, removing enemies and impuri- 

 ties which may have got in, taking out any dead oysters, and 

 rearranging those that are left, so that all may have a fair 

 chance of obtaining food and growing normally. The young 

 oysters grow rapidly in the ambulances, and soon have to be 

 thinned out. The larger ones are removed, and if large enough 

 are thrown into the open area's of the pare. In this way, by 



^ Various import.-uitJpapers in Bulletin U.S. Fish Com.nission. 



