59 
their size, and lastly owing to the swiftness with which they can escape from such 
a small apparatus as a 0,, m.? bottom-sampler. We have therefore only the data 
of the fisheries statistics to rely upon. But with the help of these we can 
only ascertain what is caught yearly, not what lives, in this water.) I will 
therefore only count with round numbers in the case of the fishes. An exception 
may be made however for the plaice, regarding which specially detailed data are 
kept owing to the extensive transplantation of this fish; hut the data have other 
shortcomings, such as that they do not include the plaice destroyed by the whelks, 
and this amounts perhaps to a third of the whole year's catach. In order to 
counterbalance this defect, I have not deducted from the production, that the 
plaice when transplanted weigh ca. 7—10 kg. per 100, nor that other flat-fishes 
such as flounder, dabs, turbot, are included in the statistics; even then the stati- 
stics certainly show a smaller quantity than the catch actually has been. 
According to the fisheries statistics the following quantities of fish were 
taken in Thisted Bredning in 1908 and 1909: 

This would in part agree very well with my view, if it really is the case; but the 
foundation of Franz conclusion leaves a great deal wanting. Applied for example to a stock of 
partridges regularly kept down by shooting, it would not hold good, in spite of the fact that the 
»pheasants live for several years«. Most of them do not do so however; as the 0-group of 
the autumn, which is for the most part shot down, is much in excess in most years. I may take 
an even closer example Abra alba, which both in the Limfjord and in the North Sea (according to 
Franz) has so great importance for the plaice; he states that it may live until it is 5 years old 
to judge from the growth-rings on the shells. In the Limfjord it only lives 2 years, at least I 
have not been able to find any older, and these are even very seldom, on the soft bottom at any 
rate. Now it is just this species which in the Limfjord is so abundant in the autumn in contrast 
to the spring (see Table V); its Ogroup is prodigiously numerous in the autumn. It is of course 
possible, that it often only becomes 1 to 2 years old in the Limfjord, owing to its being much 
sought after by the fish, and may become older in the North Sea; but in that case its autumn 
group in the latter should show a maximum. We must have accurate information regarding this. 
In the Kattegat I have seen a similar, extremely numerous 0 group of Mactra subtruncata, 
which appears at certain places near the coast in autumn and which is eaten with great avidity 
by the plaice living there. This species also lives for several years, but it is certainly much more 
numerous at certain seasons of the year than at others. I should think it very probable that, on 
the shallower stretches of the North Sea, especially along the Schleswig and Jutland coasts, 
similar numerous 0-groups of the Lamellibranchs living there and perhaps of other animals 
appear in the autumn. 
F. mentions Solen pellucidus, Corbula gibba, Pectinaria and other species, which however 
are not important in the Limfjord; in Pectimaria I know there is also an enormous autumn group 
in the Limfjord, but not in Corbula and probably not in Solen. As said, I am much inclined to 
believe, that the North Sea as a whole does not have such great changes in the quantity of 
food with the seasons, but I would only advise against concluding that this is the case on the 
basis of the above reasoning. 
2) In Nissum Bredning, where the plaice is so extremely numerous, I have endeavoured 
to capture them with a 1, m.” bottom-sampler, and thus to determine their number; but though 
several plaice were caught with this apparatus, the accuracy is not sufficiently great. Such 
experiments are however being continued and will eventually succeed I hope. The watchfulness 
of the plaice is the greatest hindrance to an enumeration. 
