Page:The Zoologist, 4th series, vol 1 (1897).djvu/426

398 fine pigmentation appears, and shortly afterwards the silvery hue commences—the Whitebait stage.

Mcintosh and Masterman thus summarize the early Herring:—"The young larva, hatched at from 5 mm. to 7 mm. in length, lives near the bottom till about 10 mm. is attained by a rapid increase in length. The attenuated post-larval Herring then migrates upwards through the mid-water to the surface, the midwater stage lasting from about 10 mm. to 23-24 mm., and the surface stage from 24 mm. to 27-28 mm. [roundly speaking, one inch or thereabouts], when a movement shorewards takes place, and the littoral habit is acquired."

Their further increment and subsequent erratic movements are a more tangled skein to unravel. Growth and maturation are complicated and confused by a double spawning period. Data give a length of three inches the first twelvemonth, to five inches the second year, and to eight or nine inches the third year, when sexual maturity is attained; but British and foreign observers are not quite in unanimity thereon. It would appear though that in the case of the Baltic as well as British Herring there are two marked spawning seasons, the so-called winter and summer Herrings. The same Herrings, however, do not spawn twice annually, the summer and winter stock being races apart, whose spawning localities essentially differ. Winter spawners frequent inshore brackish waters, whereas summer spawners are more strictly sea-dwellers, coming near the coast, but not into estuaries at spawning season. The Clyde, Forth, and Plymouth Herring are winter, the North Sea group summer breeders. The former estuarine fish come and go within a limited area, the latter offshore have a wider sea migration. In both cases, though, it is a see-saw towards and away from the coast, the so-called summer Herring spawning in deeper water further distant from land.

The supposed mystery of the fish returning to their own special grounds, Cunningham thinks is due to their habit of herding in shoals. Temperature and food drive the fry up an estuary, and there as they grow, meeting older brethren, associate and accompany them back to the sea-spawning ground.

Of other Clupeoids, it is singular that the Sprat is much more used as an article of diet in England than in Scotland, though to