66 
If we estimate that every plaice in Thisted Bredning eats 10 gm. daily for 
ca. 240 days in the year, this gives a rough weight of ca. 2400 gm. per annum; 
as the plaice in 1910 increased on an average 375 gm. from April to November, 
this gives an increment which is about ”/,th of the rough weight of the food 
consumed, a figure which agrees very well with the amount eaten by fishes reared 
in a pond. The ca. 360,000 transplanted plaice would, with a gm. per day, eat 
ca. 86,000 kg. dry matter annually; but as most of them are caught before they 
have been in the Bredning 8 months, this figure is certainly too high. Taking 
the monthly statistics in account among other things, I should imagine that ca. 
50,000 kg. of dry matter would correspond better to the annual consumption of 
the plaice in Thisted Bredning. This gives for each of the 65 million m.? in this 
Bredning a production of 0.77 gm. per m.? or 7.: gm. per 10 m.? If we assume 
that the eels, both young and old, eat twice as much, the total consumption of 
these two species would be ca. 23.1 gm. per 10 m.? annually; thus in reality not 
a great amount by comparison with the annual production of dry matter of up to 
200 gm. per 10 m.? The connection of Mya with this will be discussed later. 
In Nissum Bredning, where the plaice does not digest the contents of its 
stomach each day, the residue of 4.1: gm. im the morning must be deducted from 
the total evening contents of 8.4 gm., so that ca. 60 plaice here per day only eat 
4 gm. in all, or 0,067 gm. per individual. Now we know from the investigations 
of many years (see e. g. Report XVIII 1909 Table C), that there are at least 
40—60 times as many plaice per "]-unit of area in Nissum as in Thisted Bred- 
ning; as each plaice in the former eats ca. 0.067 gm. day, ca. 50 plaice would 
devour 50 X 0.067 gm. or 3.35 gm. on the same area, where one plaice in Thisted 
Bredning eats 1 gm.; in other words, 3.35 times more plaice food is used per m.>? 
in Nissum Bredning than in Thisted Bredning; thus annually 3.35 X 7.7 gm. or 
25.8 gm. per 10 m.? against 7.7: gm. in 'Thisted Bredning. 
The food consumption of the plaice in Nissum Bredning is thus much 
greater than the calculated amount of the food of the plaice and eel together in 
Thisted Bredning (23 gm. per 10 m.?). This result is not surprising, when we know 
that in Nissum Bredning outside the 6 meter line practically no other animals are 
found at all times but the plaice; here whatever is eaten, is eaten by the plaice. 
lt is not my intention, naturally, that too much weight should be attached 
to these figures and the results of the calculations; they should rather be regarded 
as a first experiment in breaking a way where hitherto any calculation or even an 
estimate based on figures, measure and weight, has been impossible; that the 
preliminary results obtained are so reasonable as they are, has in fact surprised 
me, but they also encourage the hope of obtaining even better in the future; im 
any case they have been able to show, that the plaice in Nissum Bredning really 
eat less per individual than in Thisted Bredning, and we can thus understand 
their small annual growth in Nissum Bredning. There is certainly overerowding 
in the latter; but no little food is produced on the bottom per m.? though certainly 
less than in the central Limfjord. 
There is therefore evidently a limit to the extent we can carry on the 
transplantation of the plaice; the density may be too great; where this limit lies, 
is for future investigations to determine. We shall probably hardly be able to find 
