DISTRIBUTION OF FISH AND OTHER ANIMALS. 



The question has often been raised as to 



how far the young fishes brought up in the shrimp 



trawl, if not actually dead, are so seriously 



injured, that they would not recover, even if 



promptly returned to the sea. We have made 



many experiments, and kept many records bearing 



upon this matter. In 1893, we devised a series 



of " vitality" experiments, which were carried out 



on the Fisheries' steamer "John Fell," for several 



years. Sample fish from the various hauls, were 



placed, after their condition had been recorded, 



in a large tub, through which there flowed a 



constant circulation of sea water. The condition 



of the fish at stated intervals, half-an-hour and 



then hourly, was noted, and the ultimate recovery Fic " ^~Boat working a shrimp Trawl, 



or death. The result, naturally, depended greatly upon the kind of haul, the length of the 



drag, the weight of the catch, the muddiness, and other particulars ; but it was also found 



that some fish are much more delicate than others, and can stand less knocking about and 



pressure. Flat fish on the whole can stand more than round fish. Soles seemed to be 



specially hardy, about 95 per cent, surviving ; while Plaice came next, 81 per cent, of those 



caught, some with the fish and others with the shrimp trawl, having recovered after being in 

 the tub on the average for about an hour. It is obvious, then, that under ordinary circum- 

 stances the majority of such fish caught might still live if returned promptly to the sea. But 

 even if one puts the most favourable interpretation upon such experiments, it is obvious that 

 there is an immense amount of destruction going on in the Lancashire fish " nurseries." 



These extensive "nurseries" are an important link in the life-cycle of the more 

 sedentary fish of the Irish Sea. They depend upon the off-shore spawning grounds for 

 their supply, and in their turn they give recruits to the stock of adolescents and adults 

 on the fishing grounds. 



Taking the Plaice as a typical sedentary flat-fish, and the one to which attention has 

 been largely directed in our district,* we find that the females become mature in our seas at a 

 size of from 13 to 15 inches, and the males at about n inches ; they are probably at that time 

 about 3 or 4 years old. The spawning of the plaice takes place from February to the 

 end of May and the female fish lays from 300,000 to 400,000 ova. The egg is of 

 relatively large size, as edible fish-eggs go, being from i "6 mm. to nearly 2 mm. in 

 diameter. The spawning takes place in deep water, say 20 to 30 fathoms, at a distance 

 from land, and the egg floats at or near the surface of the sea during its development. 

 At a temperature of 10 C., the embryonic development, from the fertilisation of the egg 

 till the larva is hatched, takes about 12 days; and then there emerges from the egg- 

 covering a little plaice larva of about 6-5 mm. in length. At first the larva does not 

 eat, and subsists upon the remains of the nourishing matter that was in the egg ; but 

 this yolk sac only lasts for about a week, and shortly before it has disappeared the 

 larva begins to feed, at first upon Diatoms and minute larval Molluscs. A 

 fortnight later, three weeks from hatching, it measures about 7^5 mm., and now feeds 



* See the Memoir on the Plaice by F. J. Cole and J. Johnstone, appended to the Lancashire Fisheries 

 Laboratory Report for 1901. 



