SEA-FISIIER1ES LABORATORY. 149 



five millions of young plaice were hatched in 1905 at 

 Port Erin, and were set free in the sea round the south 

 end of the Isle of Man. It is important also to note that 

 large numbers of fry from the previous year's operations 

 which were left to develop in the pond passed through 

 their metamorphosis and grew rapidly, being found of 

 various sizes from one to five inches in length during their 

 first year of life. The largest of these young plaice, 

 spawned, hatched and reared in captivity, which we have 

 taken from our pond, measured over six inches. 



Marked-Fish Experiments. 



This work was commenced by Mr. Johnstone last 

 year, and has been carried on further with the co-opera- 

 tion of Dr. Travis Jenkins on the steamer. The essence 

 of the experiment is that certain picked living fish are 

 marked with distinctive numbers in the manner described 

 further on by Mr. Johnstone, and are set free at localities 

 duly noted — those of such fish which are subsequently 

 captured being returned, with particulars, to our labora- 

 tory for observation and record. The object of the 

 experiment is three-fold. The results may be expected 

 to give us information : — 1st as to the growth of the fish, 

 2nd as to the migrations of the fish, and 3rd as to the 

 numerical proportion of the fish caught, and consequently 

 as to the intensity of the fishing in our seas. The results 

 are rather startling. For the details Mr. Johnstone's full 

 account given below should be read, but the following 

 may be taken as a summary of the matter : — In the case 

 of the Lancashire stations about 50 per cent, of the 

 marked fish have been re-captured which may be an 

 indication that the fishing is so intense that half of the 

 available fish are captured in the year. Whether this is 

 " over-fishing " it is impossible at present to say, but the 



