556 



NA TURE 



{April 1 6, ii 



buoyantly as any of the foregoing ; and the same was 

 proved to be the case with the eggs of the sole and lemon- 

 dab — all these, moreover, being obtained in the act of 

 spawning far out at sea, and in comparatively deep water. 

 The ova of the long rough dab and the common dab were 

 also added to the list of those with floating eggs. The 

 notion, therefore, that such fishes seek the shallow water 

 for the purpose of spawning is visionary, and mainly rests 

 on the preconceived opinion that the eggs are deposited 

 on the bottom. 



Amongst the eggs of the cod floating on the surface of 

 the water off the Island of May, in April, were vast 

 numbers of very young sand-eels. The late Mr. Buckland 

 states that they spawn in " May, June, and September," 

 and that they deposit their eggs in the sand. They would 

 rather seem to spawn in spring, and their eggs probably 

 avoid the sand as much as possible by floating on the 

 surface of the water. Sand is a most objectionable site 

 for the eggs of certain fishes, and no less so for the 

 embryo. 



Without going into further detail, it is evident, there- ! 

 fore, that the eggs of many of the most valuable food 

 fishes thus float near the surface of the sea, e.g. those of the 

 cod, haddock, whiting, bib, and other Gadoids, mackerel, 

 gar-fish, red mullet, weever, plaice, long rough dab, common 

 dab, lemon-dab, sole, common flounder, and probably 

 sand-eels. There is hardly a marine fish, excepting those 

 of the herring group, which appears in our markets, but 

 has this remarkable provision in regard to its eggs. It 

 would also appear that some of these eggs range thiough- 

 out the water, so as to be caught by a tow-net sunk many 

 fathoms beneath the surface. 



There can be little doubt that this wonderful provision 

 is one of the main reasons why such marine fishes have 

 held their own in the struggle for existence — not only 

 with respect to their predatory neighbours, but still more 

 in regard to the persistent inroads on their numbers made 

 by man. Marine fisheries have hitherto been conducted 

 as if practically inexhaustible, both lines and trawlers 

 taking as much from the sea as possible, while no margin 

 has ever been afforded the spawning fishes. 



Let us for a moment glance at the working of this 

 arrangement. The comparatively small eggs of the chief 

 food fishes rise to the surface, or nearly to the surface, 

 wherever the shoals of adult fishes happen to be feeding, 

 and this occurs not during a brief period, but it extends 

 over a considerable space of time. The tiny young in 

 their helpless state are carried, along with multitudes of 

 eggs, by every tide into sheltered creeks and bays, in the 

 shallow water of which they find both safety and food. 

 We aie familiar with these tiny embryos, furnished with a 

 yolk-sac — and so fragile that they would fall an easy prey 

 to hosts of swimming crustaceans on which, in the adult 

 state, they would hardly deign to feed — near the surface 

 of the sea ; but a hiatus yet remains in the history of the 

 young cod, for instance, between the date of complete 

 absorption of the yolk-sac and that in which it is found 

 swimming in the forests of tangles in the laminarian 

 region — for example, off the Castle and Pier Rocks, or 

 even venturing into the harbour. There, as a rule, it is 

 free from the pursuit of both liners and trawlers, and 

 quietly grows apace, feeding on the swarms of minute 

 crustaceans and the myriads of very young mussels which 

 characterise such a region. In the early part of the season 

 they range from one and a half to two inches, and are 

 variegated with a scries of pale spots, somewhat rect- 

 angular in outline. The general colour is olive, lighter 

 or darker according to circumstances, though a few of the 

 larger examples have a reddish hue, such as signalises 

 the "rock-cod" of the liners, but the pale spots are 

 similar. Many of these young cod are infested by para- 

 sitic crustaceans {Ckalimus), which adhere by a long 

 median process that penetrates the skin. They are ac- 

 companied in the laminarian region by the young of the 



coal-fish, whiting, pollack, rockling, long-spined cottus, 

 and lump-sucker. 



Sars is of opinion that the intermediate stage — about 

 which, as above-mentioned, our knowledge is imperfect — 

 is passed by the young cod-fish in the shelter of the jelly- 

 fishes, on the rich grounds off the Loffoden Islands. It is 

 true that once or twice young cod, of the intermediate 

 stage, and coal fish have been caught in our seas in the 

 tow-net in July, but the result of the present observations 

 gives no support to this view. The jelly-fishes in our 

 seas are not in sufficient numbers at the time of the inter- 

 mediate stage, especially in regard to the spawning in 

 April, to act as shelter-forms to the young fishes. It is 

 probable that as soon as they gain sufficient strength to 

 withstand the force of the ordinary ebb-tides, they remain 

 amongst the tangles and other seaweeds of our rocky 

 shores, to which they have meanwhile been carried by the 

 currents. While a few, therefore, are found here and 

 there near the surface of the sea amongst other pelagic 

 types, the majority of those in the intermediate stage 

 probably swim somewhat deeper. 



The after-history of the little cod of one and a half 

 to two inches, which are found in considerable numbers 

 off the Pier and Castle Rocks in the beginning of July, 

 appears to be as follows. They remain in the laminarian 

 region for some months (many being captured even at 

 this season), and rapidly increase in size on the rich and 

 abundant food placed within easy reach. Moreover, it is 

 probable that in this region they are much less liable to 

 the attacks of predatory fishes than in the open sea. We 

 find, indeed, that, while young haddock and whiting 

 abound in the stomachs of cod, haddock, gurnards, and 

 other fishes, it is rare in our seas to find young cod of the 

 size we are now considering. Prof. Sars, on the other 

 hand, procured them abundantly in the stomachs of the 

 pollack (a fish which swims high) off the Norwegian 

 shores ; but it has to be borne in mind that they form the 

 chief feature of the young fish-fauna of the region at the 

 time indicated. As they grow larger and bolder, they 

 seek deeper water, and are found in numbers near rocky 

 or rough ground, such as oft" the Bell-rock, and the North 

 Carr rocks, and indeed all along the rocky eastern shores. 

 They then mingle with their progenitors on the various 

 fishing-banks, and are caught in numbers by both hook 

 and trawl. The main cause of this migration from the 

 shore seawards is probably the nature of the food, which, 

 as the animals grow older, becomes of a different charac- 

 ter, the larger Crustacea especially — such as hermit-crabs, 

 Norway lobsters, and many short-tailed crabs — being 

 eagerly sought after, along with various kinds of fishes. 

 So far as our knowledge at present goes, a cod probably 

 takes between three and four years to attain full growth. 



A feature which requires special mention is that, when 

 the shoals of young cod are watched at any of our rocky 

 shores during several months, one is struck by the fact 

 that throughout the period many small forms are present, 

 that is, some do not appear to have grown ; but we have 

 seen that the spawning of the adult fishes extends 

 over a considerable period, and, further, that only a 

 portion of the eggs in any given fish come to maturity 

 at once. There is thus a succession of young fishes 

 coming at a certain stage shorewards, and another 

 migrating outwards. This and other facts already men- 

 tioned show how intimately the inshore ground depends 

 on the off-shore ; in other words, the eggs and very young 

 fishes are carried from the offing by every tide during the 

 season, while a constant stream of young' fishes of a large 

 size goes to swell the ranks of the adults beyond the three- 

 mile limit. The prosperity of the one region is thus 

 intimately associated with that of the other. 



In this rapid sketch, then, it will have been observed 

 how complex are the relations which surround the increase 

 of marine fishes. Conspicuous above all others, how- 

 ever, is the remarkable provision whereby the eggs of 



