61 
that Abra in autumn of 1910 alone has a larger quantity of dry matter, namely 
9.54 gm., the other small Lamellibranchs 5.54 gm, all the worms together 9.42 gm.; 
all these small animals thus have a total quantity of dry matter of 24.5 gm. In 
the spring of 1910 the quantity of the above-mentioned animals was somewhat less. 
The young Mya are not all included here. 
Such momentary pictures of the fauna thus show, that the quantity of 
the food-animals is quite considerable, at any rate compared with the quantity of 
fish caught; we shall return to this matter later. 
In Table V however we find among the lower animals several, which 
like the fishes must also be referred to the consumers, namely Bucewnum, Nassa 
and Åsterias. 
Eclumus miliaris belongs in reality to the Zostera belt, which, as the Chart 
shows, extends somewhat out into the region investigated with quite a slight 
Zostera vegetation; Ophrioglypha probably is partly worm and partly detritus feeder. 
With regard to Åstertas rubens, this is present in such small numbers in the Table, 
that we cannot conelude anything as to its real abundance in the Bredning; it is an 
eager devourer of Lamellibranchs, and in an aquarium eats up an extremely large 
number of these in a short time. 
With regard to Buccinum, I have endeavoured in another way, by diving 
and by using a larger bottom-sampler, to determine the quantity in 1909 
somewhat more precisely (see Report XIX, 1911), and then found that 1.3 Buccrnum 
lived on each m.”%, thus in all ca. 20,000 barrels of 95 kg. each or 1,900,000 kg. 
rough weight, or ca. 30 gm. rough weight per m.? If we use the percentage of 
dry matter 11.62 Boysen Jensen found in the spring, Rørdam in the winter 
found 15.1'/,, we have 3.1s6 gm. dry matter, the shells not included, per m.?, or 
34.s6 gm. per 10 m.?, thus 5 times more than the Table shows. 
The quantity of dry matter for Nassa is seen from the Table V to be on 
an average 3.57 gm. per 10 m.?”; it must he considered to be much better represented 
in the Table than Bucernum, as it is much more numerous. In the great whelk 
fishery we carried out, the mass of Nassa was much less than that of Buccinum, 
so that there can be no doubt, that the mass of Bucezmum is in reality much 
greater than that of Nassa. 
The quantity of dry matter in these whelks is, as shown by the foregoing, 
much greater than the quantity of dry matter in the fish caught; the latter was 
only ca. 7.1 gm. per 10 m.” Although the fish caught do not represent all there 
is of fish-flesh in the Bredning especially eel, for example, of which there are 
many younger year-groups, yet we may assume, that the dry matter of the 
whelks is much greater in quantity than the quantity of dry matter in the fishes. 
If these large whelks and AÅstertas lived on the same small animals as 
the eel and plaice live on, it would be an awkward thing for the rational fishery 
in Thisted Bredning; they do not do so, however, at least not exclusively; we know, 
how eagerly the whelks attack almost all fish in the summer which they can get 
hold of, and all oysters which are open; but what they normally live on, we do 
not know, as it was only when something eatable had been given them, that I 
could find anything determinable in the stomachs of the whelks; probably they 
can also overpower large Lamellibranchs; but they can obviously go hungry for a 
