August 30, 1883] 



NA TURE 



4>5 



OYSTERS, OYSTER FISHING, AND OYSTER 

 CULTURE AT THE FISHERIES EXHIBITION 

 A S long as the English " native " keeps its prominent 

 -**■ place in the market all questions concerning oysters 

 and oyster culture will have a special interest for the 

 British public at large. For the man of science oysters 

 are none the less interesting, although from a different 

 point of view. For him it is a great puzzle that up to 

 now we are in so profound a state of ignorance concern- 

 ing certain of the most important phases of life of a mol- 

 lusk so exceedingly numerous, which may indeed be 

 called very common, if not always plentiful, all along a 

 large extent of the European coast. Questions such as 

 the following : —Are oysters functional hermaphrodites or 

 not ? At what age can oysters reproduce their species ? 

 How long do the oyster larva; (the so-called ''spat") 

 swim about in the ocean as free and independent, al- 

 though minute, living specks ? What is the effect of 

 currents and temperature, both upon the growth and 

 upon the fertility of the oyster ? are or were up to very 

 lately wholly unsolved, and no really scientific inquiry had 

 thrown any definite light upon them. Even the anatomy 

 of the oyster was very imperfectly known, and it was 

 (inly last year that the researches of Dr. Hoek, exhibited 

 in the Netherlands department of the Exhibition, threw 

 a flood of light upon this point. These are the first 

 of a more extensive series of investigations which are still 

 in preparation, and which will treat of the embryology 

 and the food of the oyster, the fixation of the spat, and 

 the physical conditions under which the apparently very 

 fertile oyster beds of the Eastern Scheldt are placed. 

 These investigations have been undertaken and pur>ued 

 for three summers consecutively by the Netherlands 

 Zoological Society. 



The exhibit in the Netherlands department is the only 

 one in which the scientific side of the oyster question 

 comes into the foreground. Highly interesting from the 

 point of view of practical oyster culture are, however, 

 two exhibits — one in the Norwegian, one in the British 

 department, which we propose to describe somewhat 

 more at length. 



The Norwegian one is a bottle containing oysters from 

 the small lake of Ostrawigtjen, near Soggendahl, on the 

 south coast of Sweden. This lake, which is only about 

 800 feet long and 500 feet wide, with a depth of about six 

 fathoms, may be regarded as a real " hothouse " for 

 oyster culture, the temperature of the water being at the 

 end of last April no less than 22° C, whereas in winter 

 the water at a depth of three fathoms never registers any 

 lower temperature than f C, the average bottom tem- 

 perature in summer being 27 = C. Considering the lati- 

 tude in which the lake is situated, these temperatures are 

 indeed very remarkable, and have not yet been fully 

 explained. Some would ascribe it to a most luxurious 

 vegetation of Confervas which is found in the lake, the 

 partial decomposition and fermentation of which might 

 increase the temperature. It is, however, open to ques- 

 tion whether this confervoid vegetation must not perhaps 

 be rather looked upon as an effect than as a cause of the 

 high temperature. 



This lake incloses a natural bed of oysters, and already 

 at the end of March some of these oysters contain ripe 

 black spat. In the summer months the productivity of 

 course greatly increases, and up to November {i.e. nearly 

 nine months consecutively) ripe oysters with larvae in their 

 gills are met with. 



It need not be said that this is a splendid collecting 

 ground. The spat is collected on birch twigs which are 

 suspended in the water on wires stretched over it. 



In 1882 one thousand collectors were brought out, 

 each having a surface of about sixteen square feet, and 

 on these 730,000 young oysters were obtained, which were 

 than transferred to natural beds in the fjord close to 

 Stavanger. 



If the oysters were left where they are they would cer- 

 tainly grow very quickly ; oysters of one year sometimes 

 attaining a size of six to seven centimetres. For several 

 reasons, however, the transfer is regarded as more suit- 

 able for them. 



A most curious fact concerning this lake remains >et to 

 be told, viz. that it is situated 2j feet above high-water 

 mark ; that it is separated from the sea by a dry tract of 

 land with large boulders ; and that only between Septem- 

 ber and March, when the weather is very rough, fresh 

 sea water can gain access to the lake by the sea 

 being thrown across this tract of land. At the opposite 

 side of the lake a small rivulet of fresh water enters the 

 lake. 



A second " hothouse " for oyster culture appears to have 

 been discovered only very latelv : it is in most respects 

 similar to the first ; the depth is about 3! fathoms ; the 

 temperature in October was i8 : C, in April 21 C It is 

 situated at Vesetvig near Stavanger, on the Hardanger 

 fjord. 



The British exhibit, to which we would wish to call atten- 

 tion more especially, bears the name of Wootton, Isle of ' 

 Wight. It consists of models of ponds devoted to the 

 "basin culture '" of oysters, essentially different in prin- 

 ciple from " foreshore culture," which is at present more 

 successful and more generally recommended. 



" Basin culture " is nevertheless perhaps a future stage, 

 when once the acute practical intelligence of the o\stcr- 

 culturist and the investigations of zoologists shall have 

 succeeded in reproducing the natural circumstances under 

 which the oyster spat lives and thrives. At the confer- 

 ence on oyster culture held by Prof. Hubrecht, we were 

 told that investigations more especially relating to basin 

 culture were at the present moment being carried on in 

 Holland. The result obtained in the Isle of Wight was 

 this, that in the first year (1880) the number of the spat 

 obtained was about 25,000, in the second year (1881) 

 250,000, and in the third (1882) 1,500,000. Notwithstand- 

 ing this successful commencement, the final results have 

 as yet remained far below the expectation, since only a 

 comparatively small number could be brought to be mar- 

 ketable oysters. A difference between these experiments 

 and those carried on in the Netherlands, which may per- 

 haps prove to be one of fundamental importance, is this, 

 that no contrivances have b:en made use of in the Isle 

 of Wight to sufficiently aerate the sea water in the basins. 

 Lack of oxygen may have been the principal cause of the 

 great mortality of the spat. Moreover, a certain amount 

 of sea water was let in and let out at favourable tides, 

 and this must to a certain extent have interfered with the 

 reliability of the results. 



These experiments were carried on with oysters that 

 were imported from the Arcachon beds. 



The exhibits in the ostrei cultural department by Mr. 

 Fell Woods, the well-known director of the South of 

 England Oyster Company (Hayling Island), and by the 

 Whitstable Oyster Company, likewise deserve attention. 

 In both, specimens of shells of one-year-old oysters are 

 shown, the occupants of which are said to have produced 

 "black spat" at that early age. Even if these observa- 

 tions are well authenticated, it is nevertheless re:ognised 

 that such facts are very rare ixceptions, and that gene- 

 rally at three years, and more profusely still at from four 

 to six years, the maximum quantity of ripe spat is pro- 

 duced by the oysters, whose generative organs are most 

 active at that age (cf. Hoek 1 . 



France has only a comparatively small exhibit ; the 

 implements used in oyster culture at Arcachon are 

 there shown. The Netherlands are represented by a 

 more complete collection, showing both dredging and 

 collecting apparatus, so-called "hospitals," tiles, knives, 

 &c. Models of several oyster parks, partly constructed 

 in old fortifications, and consequently having a very 

 " defensive " aspect, are, moreover, exhibited, as well 



