| dc.description.abstract | From the mean values it can be seen that herring of the "Southern-type"
in both years have the same growth rate as those of the "Northern-type".
The conclusion must be, therefore, that the correlation, "N-type"
- slow growth -, "S-type" - faster growth -, as revealed by an
analysis of mature winter-herring, is due to the dominance of fastgrowing
"S-type" herring of southern origin in the composite "S-type"
winter-herring, and vice versa, a dominance of slow growing herring
of northern origin in the composite samples of "N-type" winter-herring.
This conclusion is not incompatible with the observations made by
Marty (1956), that growth rates tend to decrease when the stock is
rich and the observation of Østvedt (1958), that a rich stock seems to
be dependent on a rich influx of "N-type" herring.
Admittedly it is a weakness pertaining to the present material that
the "S-type" herrings are few in the samples and it would be worthwile
investigating fat herring from the waters of Møre-Trøndelag to see
if any significant difference in growth-rates of "S" and "N"-type can
be discerned there.
The strong dominance of the year-class 1918 as II-group in 1920
shows that a rich year-class of herring under such circumstances as then
prevailed, may be recognised at the early stage of II-group, a point well
worth noting for routine survey purposes. | |
