— 205 — 
med their yolk and commence to seek food for themselves. All extant accounts of such 
experimental culture refer to this point, and anyone who has studied the earliest pelagic 
stages of the fish will know how difficult it may frequently be to find the young larvae 
in the same water where the eggs, a short time before, were abundant. In the course 
of my own egg investigations at Lofoten in 1913, briefly referred to in Chap. III, I again 
had occasion to notice a phenomenon often before observed, viz, that at the time when 
the eggs of spring spawning fish abound, the water is almost destitute of all other orga- 
nisms, animal and plant life. This is perhaps especially noticeable in northern latitudes, 
where, as I have described elsewhere*) thousands of tons of sea water may be sifted, 
(down to a certain limit of depth) without revealing more than some few organisms. If, how- 
ever, the investigations are carried out according to the method employed in my own experi- 
ments in February-April 1913, viz; repeated examination of the same spots, it will be ob- 
served later on in the spring, (at a time varying probably as to date in different years) 
that enormous quantities of microscopical plant organisms (diatoms, flagellata, peri- 
dinea) suddenly make their appearance, being found in the form of a thick, slimy, odo- 
riferous layer on the silk of the net, which had previously been perfectly clean, containing 
nothing beyond fish eggs and some few crustaceans. It occurred to me therefore, during 
these last investigations, that it should be well worth while to endeavour to ascertain 
how far the sudden appearance of this extensive growth might be of importance for 
the continued existence of the young fish larvae. If the time when the eggs of the fish 
are spawned, and the time of occurrence of this plant growth both be variable, it is hardly 
likely that both would always correspond in point of time and manner. It may well 
be imagined, for instance, that a certain — though possibly brief — lapse of time might 
occur between the period when the young larve first require extraneous nourishment, 
and the period when such nourishment is first available. If so, it is highly probable 
that an enormous mortality would result. It would then also be easy to understand 
that even the richest spawning might yield but a poor amount of fish, while poorer spaw- 
ning, taking place at a time more favourable in respect of the future nourishment of 
the young larvae, might often produce the richest year classes. In this connection 
it must be remembered that one single cod may spawn millions of eggs. 
The French scientists FABRE-DOMERGUE and Binrrix have shown, in the course 
of two interesting works on the common sole and artificial incubation**) that the small 
larvae, even before their yolk is exhausted, commence to seek other nourishment, and 
those individuals which do not succeed in finding such become anemic, and die of hunger. 
This is, in the opinion of the writers referred to, the reason why all attempts at artificial 
incubation have hitherto proved so unsuccessful; these writers found, that when the 
young larvae were duly supplied with the requisite nourishment, 1. e. microscopical 
plant organisms, either cultivated, or taken direct from the sea, the anemia disappeared, 
and the individuals could be raised to later stages of development. 
The fishing industry furnishes many instances of variation in the time of the skrei 
fishery from year to year, the season sometimes commencing earlier, sometimes later. 
*) Fiskeri og Hvalfangst. 
**) Developpement de la Sole. Introduction à ’Etude de la pisciculture marine. Paris 1905. 
Fasre-Domercue: Etude sur la rôle et les procédés de la pisciculture marine. Bulletin de la 
marine marchande. Paris 1900. 
