FISHERIES 



8 



tHken piftce at tlio flnrfrice ; Vint witli tho cod family we 

 boliuvo the opuriitiuii hurt iiut buoii ho diMliiictly otmcrvud. 

 Tho ova, however, aio undoubtedly mot with at tliebiirluco 

 n'lil at a Hhoit distmico boh)vv it. Entirely siibvursivo uti 

 these discoveriea of I'rofeHHor Sarnore of the popular notions 

 ubiiut tiHh-Hpuwniiig, it is even more unexpected to find 

 that both lie and Al. A. SV. Malm of Ootlienburj; have 

 iudependeutly atteertaiueil that the ova of that esstMitialiy 

 ground-linh the pluii:o (I'learouectes jilatemsa) follow the 

 eame rule of floating at the Burface. Other kinda uf float- 

 ing ova were also obtained by Siirs, some of which lie 

 succeeded in batching; and he has completely identified 

 the gurnard (Tiiyla) and the garfish (/ielloiie), in addition 

 to those before mentioned. It is evident, then, that the 

 flouting of fish ova during the development of the embryo 

 must be taken as tho general rule in several large and 

 distinct families of sea fish. >^ars has pointed out that 

 the development takes place at the bottom in the case of 

 those fishes especially whose ova are cemented together by 

 a glutinous secretion, or fastened in lumps to foreign 

 bodies, such as Algw, Ilydroils, itc. He mentions as 

 examples of this, among others, the herring (Clupca), the 

 capelan(0.iMeJ'M), the species of Cottu.i, Li/iaris, Ac. 



It is particularly worthy of notice that, according to 

 these observations of the Nor>< egian naturalists, all the 

 important kinds of fish taken by our line fishermen and 

 beam-trawlers, and the mackerel among such as are caught 

 by the drift-nets, may be reas inably included among tho 

 species whose spawn hoats at or near the surface of the 

 sea, and their ova cannot therefore be liable to the slightest 

 injury by any method of fishing which is carried on upon 

 or near the ground. For if that be the rule with the 

 spawn of the cod and haddock there can hardly be a doubt 

 about its being so likewise with the ova of ling, coal-fish, 

 whiting, pollack, hake, and that northern species, the tusk, 

 all belonging to the same family. Again, turbot, holibut, 

 brill, soles, plaice, dabs, and flounders are all closely allied, 

 and there can scarcely be a doubt that the same rule 

 applies to all which 8ars and Malm have established in the 

 case of the plaice, one of the most typical of this group of 

 fishes. The gurnard family must also be included in this 

 category ; the spawn of the red mullet, we believe, has 

 been observed floating in aquariums; and the dory, from 

 its close affinity to the mackerel, may be expected to follow 

 the same rule. On the other hand, we know that the 

 spawn of the herring is commonly found at the bottom, 

 although it by no means follows that the parent fish is 

 there when the ova are excluded ; for the full herring is 

 frequently taken in drift nets which are very near the 

 surface, and these nets are often covered with small 

 lumps of spawn. At the same time the specific gravity 

 of herring spawn is greater than water, and it sinks to 

 the bottom sooner or later if nothing intercepts it. 

 Theij is no evidence of its ever floating at or near the 

 surface as is the case with that of the cod. In fact, the 

 aggregation of the ova into masses of various sizes, and 

 the glutinous substance in which the ova are embedded, by 

 which they are enabled to adhere firmly to anything with 

 which they may come in contact, point to their remaining 

 in a fixed position during the process of development. It 

 might have been anticiiiated that the other members of the 

 herring family — the pilchard and sprat, for instance — would 

 also have spawned on the ground, but, so far as we are 

 aware, their ova have never boen found there. Indeed, 

 nothing is known of the spawning habits of the sprat, 

 although this little fish has the roe well developed in 

 December or January, when it is found in the greatest 

 abundance on our coast, and comes nearest to the shore. 

 The spawning of the pilchard is a matter nf some little 

 iotereat. The late Mr Jonatliaa Couch, who probablydevoted 



morn time to the study of the habits of tin's f].sh than any 

 other iciitiiyologist, btates> his belief that tlu; pilchard 

 spawned iit the surface, and the ova became mixod with a 

 large quantity of tenacious mucus which spread out like a 

 sheet on the water and kept them rit<ating. If tliis slmuld 

 be coiifiriiied, it will prove that even in tiio case of agglu- 

 tinated masses of ova, develoimiunt may iiatuially take 

 place in thuni far away from tho bottom. There appears 

 to bo little doubt that the pilchard spawns far out at sea, 

 as they are on chance occasions taken in spawning condi- 

 tion in the mackerel drift-nets early in the year ; and when, 

 some months later, the shoals of [>ilcliards approach the 

 land the roe shows no signs of development. These 

 circumstances favour the idea that pilchards are surface 

 spawner.s, as believed by Mr Couch. 



There are several other kinds of edible fish of whose 

 spawning habits we have no definite knowledge, but 

 enough has been discovered of the habits of most of the 

 fish which are valuable for the purposes of food, to show 

 that there need be no anxiety about their 8|)a\vn being 

 destroyed by any of the methods of fishing in ordinary use. 

 The only apparent exception to this statement is in the 

 cise of the herring, whose spiwn it has lieen alleged has been 

 destroyed by the beam-trawlers. But if the beam-trawlers 

 wish to avoid ti'iring their nets in pieces, they must work 

 where the ground is smooth; and in the few precise localities 

 where it has been positively ascertained that the herring 

 dues sp iwn, the general character of the bottom is rough. 

 That is the ground specially worked over by the line fisher- 

 men for haddock, cod, turbot, and other fishes, which come 

 there in numbers for the sake of feeding on the herring 

 spawn. There is a popular idea that all fish sjiawn is of a 

 moat delicate nature, and quickly loses its vitality if taken 

 out of the water for a short time, or at all knocked about. 

 This is probably true in those cases in which the ova aie 

 separated from each other after exclusion, and float freely 

 in the water ; but it is not so with the spawn of the her- 

 ring, or probably of other fish whose ova are embedded in 

 a tenacious nmcus. The experiments of Professor Allman 

 and of Dr M'Bain have shown that herring spawn does not 

 readily lose its vitality under rough treatment, and may 

 even be hatched out after having been exposed to most 

 unnatural conditions. Professor Allman states in his 

 Report to the Board of Fisheries at Edinburgh that some 

 stones covered with spawn were taken from the sea by 

 divers on the 1st of March 1862, not far frimi the Island 

 of May. Some of this spawn was forwarded to him and 

 came into his j)ossession after being kept in only a small 

 quantity of water for two entire days. He says :-r- 



" With the view of detprmining whether development would 

 proceed in coniinement, I ; laced some of this spiiwn in a gluss jar 

 with sca-wiiter, exposinj? it in a window looking to the east. The 

 sevci'sl .stiiges of devf lopment were regularly passed tlirough, and 

 on the 16th of J'..rch the embryo was fully formed, energetiu 

 movements werf performed by it in the ovum, and it seemed ready 

 to escape into the surrounding water. On the 16th some of the 

 embryos had actually e8ca[)ed, and were now about four-tenths of an 

 inch in length. They were of crystalline transparency, and swam 

 about with great activity, and with the remains of the yolk, reduced 

 now to a very small volume, still adhering to them. The specitio 

 eliaracti rs hail, of course, not yet become established, aud the little 

 fiah ali'orded no further evidence, beyond what we alreaily possessed, 

 to enalj* us to identify it with the young of the herring.' 



The young fish lived nearly a month in confinement, but 

 the specific characters were not even then sufiiciently per- 

 fected to identify the fish with certainty. There could be 

 no reasonable doubt, however, that the spawn was that of 

 the herring. After some account of other discoveries of 

 spawn, he thus concludes his report: — 



" It was shown by these experiments thnt the vitality of the 

 spawn was in no way injured by detacliing it from the spawning 



» Hutorv ofBritUh Fisha, vol. iv. p. 81 (1866). 



