16 



small, that we cannot trust them. Another bottom-sampler, with a fishing-capacity 

 of 1,2 m^ was then constructed and used in the investigation of 34 stations (see 

 Chart, p. 14) scattered over the whole area of Thisted Bredning outside the 6 meter 

 line. The catch with it was 53 Buccinum, somewhat evenly distributed over the 

 whole area, but in the easteru part the uumber was distinctl}' greater, just where 

 in 1910 the most whelks were also found. This series of stations also gave 1,3 

 Buccinum per m-'; but I must consider it a chance, that the numbers for both the 

 large and the small bottom-sampler show just the same result, 1,3; the reason is, 

 that the small oue also takes quite small Buccinum. 



I would not trust this apparatus alone either and arrauged for a diver to 

 go down to the bottom at dift'erent plaees in Thisted Bredning, to investigate how 

 many Buccinum he was able to find ou a definite area; a method I had earlier 

 used in the oyster investigations. The area investigated by the diver was deter- 

 mined from the anchored boat "by the length of the air-tube, but also in another 

 manner, by measuring an area of the bottom w'ith a line. Buccinum however was 

 not so easy to take as the oysters; they are more buried in the soft bottom and 

 only appear when the diver has disturbed the bottom with his feet; they collect 

 specially in the foot-prints. 



At one place the diver investigated ca. 106 m^ and took 100 Buccinum 

 a secoud » ? » » 36 » » »128 » 



- third » » » » 106 » » » 70 » 



- fourth » » » » 106 » » » 97 » 



At the last two piaces the diver was of the opinion that lie had only 

 caught Yard of the Buccinum present there. If we therefore multiply the last two 

 numbers with 3, he observed altogether 729 Buccinum on 354 m-, or ca. 2 Bucci- 

 num are found per m^. 



Owing to the difficulties of the diving operations on soft bottom, we kept 

 him to the less soft, where we know that most Buccinum are found; owing to 

 this probably we got a number somewhat greater than that given by the bottom- 

 sampler, uamely 2 instead of 1,3 per m^. Whichever number we take as basis for 

 a calculatiou of the uumber of Buccinum living in Thisted Bredning, we find great 

 quantities of whelks there. 



Outside the 6 meter line the area of Thisted Bredning is, namely, ca. 65 

 million m-; consequently, we find either 84,5 millions or 130 millions of 

 these whelks on the whole area, in addition to the smaller whelks 

 (Nassa) which are ca. 5 times more numerous. 



If we reckon in round numbers with 100 miUions of Buccinum, this gives 

 ca. 19,131 barreis := 26,754 hectol., as 5,200 Buccinum ou an average make one 

 barrel. In comparison with such numbers, the quantity fished by us in 

 1910, 480 barreis, is obviously quite iusignificant; the stock is easily 

 able to replace the number of whelks fished, if that is to say the cou- 

 ditions for their growth are present. 



Professor W. Johanupeu has kindly undertaken a numerical revision of 

 the numbers found by means of the large bottom-sampler (1,2 m-) and has given 

 me the foUowing information about the result. The number of Buccinum, 1,3 per m- 

 or ca. 85 millions, found in Thisted Bredning outside the 6 meter line in October 



