57 a 
IX. The annual production in general. 
What the Tables directly show with regard to the mass of animal life per 
square unit of area, refers only to the mass of animals present at a given 
time; but what I specially wish to know is, how great is the quantity of organic 
dry matter which each species produces each year per square unit at the different 
places, thus the annual production; this would give the best information 
regarding the amount of food which is annually available. 
If we could compare the mass of the animal species, for example in the 
autumn, with the quantity of corn which is still unreaped on a corn-field, and 
could consider everything present as the year's production, the matter would be 
simple enough; but it is much more complicated for the sea-bottom. The quantities 
of dry matter found do not for example all grow up in one year or less, as in 
the case of the corn; some part does it is true, but others are several years old, 
such as the mass of the large Echinoderms, large Lamellibranchs and 
Gastropods. When we know the age of the different animals, we can 
distinguish the one-year old of rapid growth and the old, and by excluding these 
we can obtain some insight into the annual production for some species at least. 
Thus, in the Limfjord in the autumn we might be able to calculate the quantity 
present of Abra, Pectinaria, many other worms, in part Solen pellucidus, young 
Mya etc., to obtain the production of the year; in the Kattegat however we must 
exclude from the year's production most of the large Cyprina, Modiola and others, 
as also the large Echinoderms. "These last contain further so little organic dry 
matter, when the calcareous matter is deducted, that they are on the whole of 
practically no importance as food producers. But if we included the small, young, 
quickly growing Lamellibranchs in the Tables for the whole year's production in 
the Limfjord we should make a great error; since in autumn the quantity of for 
example Abra is certainly greater than in spring, which is connected with their 
birth in spring and their rapid growth in summer, but during the whole of this 
time, as soon as they have reached a suitable size, they have been exposed to the 
attacks of plaice, eel and other fish, Åsterias, perhaps Buccinum and other animals; 
we should therefore make too small an estimate, if we took the autumn incre- 
ment to represent the whole production of the year. 
We cannot attain therefore to more than an idea of the annual production 
of a bottom-fauna for the present; hut on the hasis of our study of the age of 
the animals, growth-rings on the shells of the Lamellibranchs, the rapidity with 
which a species grows up from spring to autumn etc., we can obtain a better 
estimate. For example, I have investigated Nissum Bredning with large trawls for 
many years every spring and every autumn, and seen that such enormous quan- 
tities of Ascidiella aspersa occur every autumn, whilst scarcely any are found in 
spring, that the annual production in its case must certainly be enormous. This 
can also be seen from the numbers in Table V. 
In late summer Proto ventricosa appears on the Zostera in our fjørds in 
such quantities, that every net used here is at once filled with these animals and 
to such a degree that every single mesh is jammed with them, and the whole net 
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