102 



MARINE AND FISHERIES 



6-7 EDWARD VII., A. 1907 



dock, flounder, and species which deposit small floating eggs in the sea, take from 15 

 to 30 or 40 days unless the temperature be high, when 9 to 10 days naay be the time oc- 

 cupied in incubation, all the Clupeoid eggs hitherto studied appear to pass through the 

 stages of ombroyonic development far more rapidly than the fishes above referred to. 

 With the shad, and gaspereau or alewife, the conditions of spawning are wholly dif- 

 ferent, for both these fish leave the sea, which is their habitat, to spend a few weeks 

 in rivers up which they ascend to spawn in fresh water at no great distance above tide 

 limits. When the water temperature is 56° to 60° E., in late May, or in June, the shad 

 pass into their customary rivers, the males preceding the females. They ascend with 

 considerable rapiidity, and within 12 to 14 days are found crowded on the shallow 

 sandy or pebbly areas, generally some tributaries of a large river, and deposit their 

 minute senii-buoyant spawn. The number each fish produces is about 30,000, though 

 large examples have been known to yield 60,000 eggs, or even double that quantity. 

 They hatch out in 7 to 10 days, when the clear shallows are found to be alive with the 

 wriggling jelly-like little larvse. The alewife or gaspereau is usually somewhat earlier, 

 and enters the rivers about the last of April or the early part of May, when the waters 

 are in flood. They often mingle with the shad which follow them, so that the nets set 

 for shad capture gaspereaux in great quantities. They are able to surmount falls and 

 dams, if not more than 2 to 2J feet high, throwing themselves spasmodically forward 

 and flapping the tail vigorously. The strongly serrated abdomen is said to aid in sur- 

 mounting difficulties, but this is probably not so. Having gained the calm upper waters 

 solne distance above the reach of the tide, the spawning immediately commences. On 

 moonlight nights the shallow waters present a much-disturbed appearance owing to the 

 energetic movements of the mating fish, whose tails and fins project above the water 

 as they rush hither and thither. In a few nights the process is over, and the fish 

 within three weeks of their ascent are found descending in a very thin emaciated con- 

 dition. Some remain until July, but as the eggs take a very short time in hatching 

 out, the young fry are found abundantly before the end of June, as transparent worm- 

 like creatures less than one-fifth of an inch long (4*84 mm.). The ova are smaller 

 than those of the shad, viz., about of an inch (1*86 mm.), and they cling together 

 by means of their adhesive capsules in masses, becoming attached to stakes, submerged 

 roots, stones, &c. The yolk fills up the capsule, as in the sea herring and sprat, not 

 leaving a large perivitelline space, as is the case with the eggs of the pilchard and 

 shad. 



It is an interesting circumstance that young larvse of the Clupeidse are not only 

 distinguished by their exceptionally delicate structure and appearance, but by the ab- 

 sense or very sparse presence of colour spots or pigment. There is usually a linear 

 series of black stars or minute spots along the straight elongated digestive canal and 

 intestine (Plate VIIL, figs. 2, 3, and Plate IX., figs. 14 to 16) ; but not scattered, as in 

 so many young larval fishes, over the body, cranium, and embryonic fin-membranes, or 

 even over the yolk-sac hanging below the body of the fish. But the most distinctive 

 feature is the position of the anal opening or termination of the intestine — this aper- 

 ture being in most fishes at a point distant about one-third of the body's length from 

 the snout, more or less, some species having the anus midway along the ventral mar- 

 gin of the body; but in the case of herring, sprat, shad, pilchard and clupeoids gener- 

 ally, it is at a point about four-fifths distance along the under side of the body, and 

 very near, therefore, the basal portion of the tail. The position is slightly nearer or 

 further from the tail in different species, but in all it is so far posterior in position 

 that a clupeoid larva can be immediately determined by that feature. Even in a non- 

 clupeoid like the sand-eel (Ammodytes) , with the anal opening apparently far back 

 (vide Mcintosh and Prince, Life Histories of Food Fishes, Eoy. Soc, Edin., Vol. 

 XXXV., 1890, PL XIIL, figs. 6 and Y), it is nevertheless about semi-distant along the 

 ventral line ; and in the smelt its position is fully three-quarters of the body-length from 

 the snout. Further, the notochord is in a number of cases quite diagnostic in appear- 

 ance. This cartilaginous rod or primitive backbone is divided up into a series of seg- 



