Greinar (Vísindafélag Íslendinga) - 01.01.1943, Page 175

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It is evident, that when the squid enters the waters
round Iceland and moves along the coasts, it follows the
Gulf-stream. It is often accompanied by the Caa’ing whale
(Globicephalus melas, Traill.) and other teutophag whales.
Perhaps ommatostrephes in responsible for the migration
of the Caa’ing whale into northern waters during late
summer.
When the squid enters our waters about the middle of
August, it is rather small, only about 20 cm in length
measured from the anterior dorsal margin of the mantle
to the terminal point of the cauda. During the stay in the
fjords it grows much longer, as shown in the following
table. Four samples were measured in all during the
period August 3rd—October 14th, comprising 1058 indi-
viduals. In the table the figures have been smoothed by
means of the formula: Xa = Xa+1 +- x3a ' Xa \ and indicate
the length-distribution per mille. A glance at the table
gives a good idea of the increasing length during the
season. This phenomenon can only be explained in two
Avays. Either we have here to deal with a stock mixed up by
different age-groups, but in such a way that the younger
age-groups appear first and the oldest at the end of the
season. If this is the case, we may expect two or more
peaks on the Length-frequency-distribution curve, corre-
sponding to the year-classes, but this is not the case. The
other possibility is that all the stock is composed of a
single year-class and this is in accordance with the shapes
of the curves. They are almost bimodal with a single apex
very near corresponding to the mean-length. If we assume
we have to do with one year-class only in the stock, it is
evident that it must grow very fast during the season.
In the beginning of August the mean-length is 21.85 cm
and the size-limits 18—28 cm. A little over a month later
(Sept. 8th), the mean-length has increased to 28 cm and
the size-limits are now 22—36 cm. October 14th we fin-
ally find the average-length 31.27 cm, exactly the same
in Reykjavík 1939 as in Bíldudalur 1937, and the size-
limits are now 25—39. From all this we are forced to the