42 EFFECT OF TRAWLING ON CRABS. 



lobsters, and 2013 crabs,— from that in 1883-1887. The 

 decrease, however, seems to be in no way connected with the 

 trawling industry. An increase both in quantity and value 

 has since occurred. Trawling close inshore with a small- 

 meshed net (naturalists') often produces large numbers of 

 swimming crabs, but such is a rare occurrence on board an 

 ordinary trawler. 



While, therefore, in trawling the injury to the crustaceans 

 inhabiting the bottom is considerable, it has to be borne in 

 mind that the pelagic crustacean fauna is one of the most 

 marked features in the ocean, from the north to the south pole, 

 and some of its members, e.g., barnacles attached to floating 

 timber, sessile-eyed crustaceans, schizopods, and thysanopods 

 are large enough to be the food of haddocks and herrings. 

 Moreover, vast swarms of the smaller copepods nourish the 

 younger food-fishes, and other types, again, are eaten by the 

 larger fishes. Near the mouth of the Forth, at certain seasons 

 (viz., in autumn), the water near the 'Hairst' at Crail is almost 

 thickened by Thysanoessa. The tow-nets, under these cir- 

 cumstances, soon become filled with their masses. Some, how- 

 ever, may be disposed to treat the pelagic crustacean food, in 

 connection with the nourishment of the fishes, with indifference, 

 deeming such small animals of little moment in contrast with 

 the more substantial denizens of the bottom. Irrespective of 

 the circumstance that where they abound other and larger 

 forms are in their wake, the fact that so gigantic an animal as 

 the right, or whalebone-whale of commerce, lives solely upon 

 such pelagic food in the Arctic seas, is sufficient to show how 

 important an element this floating or swimming fauna is in 

 regard to the welfare of the fisheries. The larger part of the 

 masses in the tow-net, kindly used in 1893 by Dr Allan of 

 Glasgow on board the whaling-ship ' Aurora ' of Dundee, con- 

 sisted of the little crustaceans (copepods) above-mentioned, 

 and this in the actual food-line of the whale as it swam to and 

 fro in the water near an ice-pack. In our own waters, in 

 addition to what is mentioned above, the sea-acorns, which so 

 extensively cover rocks, stones, shells, and other structures 

 within tide-mark, as well in deeper water (not to speak of 



