42 



Part III. — Twenty-first Annual Report 



off from it by The Gut, and is more distant. The Fisher Bank plaice 

 must at all events travel a long distance from the beaches in the course 

 of their growth. 



That plaice do travel great distances has been shown by the experi- 

 ments I made some years ago by marking large numbers in the Firth of 

 Forth and neighbourhood. It was found that they migrated northwards 

 along the coast, and some which had been liberated in the Firth of Forth 

 were caught a year and more afterwards in the Moray Firth, more than 

 150 miles from the place where they were set free. Still later, another 

 was re-taken near Dunnet Head, on the north coast of Caithness, near 

 the Orkney Islands, which must have travelled at least over 200 miles 

 from the place of liberation. In all these cases the movement of the 

 plaice was in a direction opposite to the prevailing surface current.* 



From observations I have made on the rate of movement of the plaice 

 confined in the large tidal-tank at the Bay of Nigg Laboratory, some 

 idea may be gained of the distance that might be covered in a short 

 period. The plaice there are tame and swim leisurely around the tank 

 near the surface, especially at feeding time, and I found that while 

 gently swimming in this way they moved at the rate of from 100 to 140 

 feet in a minute. This leisurely movement, if continued for one hour, 

 would take them a distance considerably over a mile ; when disturbed, 

 as by pushing a stick into the water, they dart off with great rapidity. 

 Since the smallest plaice taken on the deep-water grounds w^as some 

 years of age, it is easy to understand how a distance of 50 or 100 miles 

 can be traversed by them by a leisurely movement, even if it were 

 accomplished at long intervals. 



Flounder (Pleuronectes flesus). 



In the hauls on the trawlers comparatively few flounders were taken, 

 and they were for the most part large, although not always taken to 

 market. From the known habitat of this fish — more shore-loving and 

 estuarine than the plaice in its early stages, and never wandering into 

 deep water when adult — this was to be expected, and the observations 

 made are chiefly of interest in connection with its migrations from the 

 shallows into moderately deep water. 



The facts establish two well-marked migrations of the flounder from 

 the shallow water to the deeper water, one in early spring and the other 

 in autumn. The statistics of the " Garland" may be first summarised. 

 At the seven stations in the Firth of Forth, in 575 hauls of the net 

 throughout the year for ten years 1886-1895, the 321 flounders taken 

 were thus distributed in the different months ; the Table also shows the 

 distribution of the flounders taken in St. Andrews Bay in the same 

 period, and in the Moray Firth by the " Garland " in the years from 

 1886 to 1900:— 



Eleventh Ann. Pup., Part III., p. 186. Fifteenth ibid., p. 374. 



[Table. 



