of the Fishery Board for Scotland. 15 



vitality of the fish. There are certainly instances in which 

 parasites appear to be injurious ; flat-fishes for example, have been 

 found to have had tlieir gills partially destroyed by the swarms of 

 young Caligid^e and Lemma adhering to them. On the other hand 

 there are numerous fishes such as cod, salmon, halibut, turbot, etc., 

 seldom free from parasites of one kind or another, though 

 apparently healthy. 



Eighteen species of fish parasites are recorded in this paper, 

 sixteen of which belong to the Copepoda and two to the Trematoda. 

 Five of the copepods and one trematode are apparently new to 

 science, the other trematode is new to Britain. 



The Eate of Growth of Fishes. 



The results of continued investigations on this subject are con- 

 tained in a paper by Dr. Wemyss Fulton in tlie present IJeport, 

 the fishes dealt with being the plaice, common dab, long rough dab, 

 haddock, and whiting. It is shown that the growth of flat-fishes 

 is very much slower than the growth of round-fishes. AVhile a 

 young haddock for example, at the end of its first summer's 

 growth averages in length about six-and-three-quarter inches and 

 weighs nearly an ounce-an-a-half, a young plaice of corresponding 

 age measures about two-and-a-half inches and weighs about one- 

 twelfth of an ounce. After the second summer's growth the 

 haddock averages nearly eleven inches in length and about six-and- 

 three-quarter ounces in w^eight, while a plaice of corresponding age 

 averages five-and-three-quarter inches and weighs a little over one 

 ounce. The differences in rate of growth are correlated with the 

 change in conformation which the fiat-fishes undergo. 



Growth is also shown to be closely related to the temperature 

 of the water, being accelerated in summer and retarded or arrested 

 in winter in inshore waters ; it is slower but more continuous 

 in the deeper water where the range of seasonal temperature is 

 much more restricted. Partly for this reason, and partly because 

 of the later period of spawning, young haddocks taken in autumn 

 in the deep water off the Shetland Isles are about two inches 

 smaller, on an average, than in the inshore water at Aberdeen, but 

 during the winter months they make up leeway considerably. In 

 areas like the Firth of Forth, where the seasonal change of temper- 

 ature is marked, the rate of growth varies accordingly, lieing rapid 

 in summer and very slow^ in winter, while young plaice on the 

 beaches, subjected to the greatest extremes of temperature, show 

 the greatest variation, growth ceasing in winter. 



The rate of growth of one and the same species may vary also 

 according to the locality and independently of the temperature. 

 Thus both the plaice, the common dab, and the long-rough dab grow 

 more slowly on the West Coast than on the East Coast, and the 

 same is true of the plaice in the south-eastern part of the North 

 Sea, where the water is derived from the Channel. The long rough 

 dab grows more rapidly in the Firth of Forth than off Aberdeen; 

 still more slowly off the Shetlands, and slowest of all in the Clyde, 

 where a dwarf race exists. 



