130
MALCOLM R. CLARKE
were in their f i s t year and considered a large, mature male with a
well developed gonad and mantle length of 64.0 cm taken in January,
to be in a second year class. He then concluded that this species
‘‘ does not reach maturity at the end of its first year ”. The author
has been able to supplement this work with observations on over 600
females and 6 males taken by commercial trawlers operating from Hull
and Grimsby; the mode of the size distribution for March has been
added to Fridriksson’s data in Fig. 18 and a tentative “growth”
curve has been drawn in. Because the curve is so steep it seems more
likely that the July specimens were hatched in the same year rather
than the preceeding year, although migration may influence the slope
of the curve and any conclusions must be considered preliminary.
It is interesting to note the marked difference in slope between T.
sagittatus and its near relative T. paci$cus which is also known to
migrate between deep and shelf waters.
Mangold-Wirz (1 963b) found that spermatophores developed in
males between 20.0-26.0 cm mantle length. Six males with mantle
lengths of 30-40 cm taken off northern European fishing grounds all had
spermatophores (Clarke, unpublished) as did an Icelandic specimen with
a mantle length of 64.0 cm. Mangold-Wirz (1963b) found only two fully
mature females having mantle lengths of 36.5 and 37.0 cm. Only two
out of over 600 northern European females were in spawning condition
and these had mantle lengths of 464-47.0 cm (Clarke unpublished).
These figures possibly suggest that the colder water individuals mature
at a large size, and it is interesting to note that beaks of specimens
taken off Iceland become fully darkened at a larger size than those of
specimens taken off Madeira. The extension of darkening has been
related to the onset of sexual maturity (i.e. appearance of spermatophores and expansion of nidamental glands) in some ommastrephid
species (Clarke, 1962b). The largest male from northern Europe, has a
mantle length of 64.0 cm (Fridriksson, 1943), the largest female 49.0 cm
(Clarke unpublished) and the largest unsexed specimen 76.0 cm
(Herzenstein, 1885). From the Mediterranean the largest recorded male
is 32.0 cm and the largest female 37.0 cm (Mangold-Wirz, 1963b).
I n the Icelandic, Faroese and Norwegian populations sampled with
commercial trawls, females greatly outnumber males (about 100 : 1)
(Clarke, unpublished) and they also outnumber them in samples taken
in the Catalonian Sea (Mangold-Wirz, 1963b).
Adam (1960a) has outlined the present poor state of knowledge
concerning the hectocotylus of the male; a male in the British Museum
(Natural History) caught at 62’40% 12’20’W has the right ventral
arm hectocotylized and spermatophores at a mantle length of 17.8 cm.
MALCOLM R. CLARKE
were in their f i s t year and considered a large, mature male with a
well developed gonad and mantle length of 64.0 cm taken in January,
to be in a second year class. He then concluded that this species
‘‘ does not reach maturity at the end of its first year ”. The author
has been able to supplement this work with observations on over 600
females and 6 males taken by commercial trawlers operating from Hull
and Grimsby; the mode of the size distribution for March has been
added to Fridriksson’s data in Fig. 18 and a tentative “growth”
curve has been drawn in. Because the curve is so steep it seems more
likely that the July specimens were hatched in the same year rather
than the preceeding year, although migration may influence the slope
of the curve and any conclusions must be considered preliminary.
It is interesting to note the marked difference in slope between T.
sagittatus and its near relative T. paci$cus which is also known to
migrate between deep and shelf waters.
Mangold-Wirz (1 963b) found that spermatophores developed in
males between 20.0-26.0 cm mantle length. Six males with mantle
lengths of 30-40 cm taken off northern European fishing grounds all had
spermatophores (Clarke, unpublished) as did an Icelandic specimen with
a mantle length of 64.0 cm. Mangold-Wirz (1963b) found only two fully
mature females having mantle lengths of 36.5 and 37.0 cm. Only two
out of over 600 northern European females were in spawning condition
and these had mantle lengths of 464-47.0 cm (Clarke unpublished).
These figures possibly suggest that the colder water individuals mature
at a large size, and it is interesting to note that beaks of specimens
taken off Iceland become fully darkened at a larger size than those of
specimens taken off Madeira. The extension of darkening has been
related to the onset of sexual maturity (i.e. appearance of spermatophores and expansion of nidamental glands) in some ommastrephid
species (Clarke, 1962b). The largest male from northern Europe, has a
mantle length of 64.0 cm (Fridriksson, 1943), the largest female 49.0 cm
(Clarke unpublished) and the largest unsexed specimen 76.0 cm
(Herzenstein, 1885). From the Mediterranean the largest recorded male
is 32.0 cm and the largest female 37.0 cm (Mangold-Wirz, 1963b).
I n the Icelandic, Faroese and Norwegian populations sampled with
commercial trawls, females greatly outnumber males (about 100 : 1)
(Clarke, unpublished) and they also outnumber them in samples taken
in the Catalonian Sea (Mangold-Wirz, 1963b).
Adam (1960a) has outlined the present poor state of knowledge
concerning the hectocotylus of the male; a male in the British Museum
(Natural History) caught at 62’40% 12’20’W has the right ventral
arm hectocotylized and spermatophores at a mantle length of 17.8 cm.