be fished according to the present standard. For the oysters taken by dredge and 
by diving, which are almost always fished in deeper water, 1!//,—5 fathoms, the 
conditions are less unfavourable, as the oysters there are all both longer and thicker. 
Table III shows the length of all the oysters obtained by diving 
” at 15 places during my investigations. The localities are situated between Løgstør 
and Thyborøn. The method of fishing was to anchor the usual boats for oyster 
diving on the bank by means of two anchors, so that they remained quite steady. 
The diver had a definite length of line each time, so that the depth being known 
we could approximately calculate how far he could travel round about the bank, 
and therefore how large an area had been fished. All the oysters on this area 
were as far as possible taken up and measured; hut it is impossible to fish the 
bank quite clean on account of various practical difficulties; sometimes the diver 
would estimate that ca. 50 oysters remained, for example, where there were large 
stones on which they were too firmly fixed. On muddy ground some might easily 
be covered by mud, and the water here is easily disturbed so that all the oysters 
could not be seen. It appears from Table III, that the full-grown. group is most 
strongly represented at 3 cm., just as for the oysters taken by pole-dredge, then 
at 9 cm. and not at 7 cm. as for the latter. A maximum for the young oysters 
occurs at 3 cm. 
Of all the 3404 oysters over 7 cm. obtained by diving, 3318 were tested 
by the standard 8 x 3 cm. (see Table III); only 1845 did not pass through this; 
some right up to 10 cm. could pass through like the oysters taken hy pole-dredge; 
at 8 cm. only 27 9/, were retained, at 9 cm. 70?/,. The details of these measure- 
ments appear in Table IIIa. I have given the Tables with the details appended, 
because they give a good view over the relative numbers of the oysters at differ- 
ent sizes living at this moment in the Lim Fjord. If the size of the oysters in 
the Lim Fjord should change, we have here a material by means of which we 
can detect the change. It is just such a material we lack for the plaice fishery 
im the Kattegat for the years about 1880. É 
That the Tables over the diving investigations have also an other and 
special worth will be shown later. 
Table II over the dredged oysters shows that they in general have their 
maximum at 9 cm., 8 cm. is the next almost as frequent and then 10 cm. They 
are thus distinctly larger than the oysters obtained by diving shown in Table III. 
This difference may arise from the fact that the diver took up all the oysters, 
both large and small; under ordinary conditions he only takes the large; but it is 
well-known that diving brings up more undersized oysters than any other mode 
of fishing. There is room here for individual choice. By means of the method 
used in the diving operations in the present instance we obtain the best picture 
of the kind of oysters which actually occur on the banks, since all are taken up 
as far as possible. We endeavoured to do something similar in our experiments 
with the pole-dredge; but it is remarkable that the dredge has a tendency to leave 
behind a certain intermediate size of oysters; this feature will certainly prove to 
be different under different conditions and with dredges of different construction. 
The important thing is that both our pole-dredging and diving experiments 
may be considered as giving the best possible information regarding the stock of 
