EFFECT OF TRAWLING ON INVERTEBRATES. 37 



absence of proof), swarms of the young would settle on the 

 sites thus bereft of their predecessors. This interchange 

 between the surrounding water and the bottom was pointed 

 out in the Trawling Report, thus : — ' The sedentary fauna of 

 any such ground ' — referring to fishing-banks — ' brought up in 

 the trawl, does not, however, give the whole explanation, for it 

 has to be remembered that almost throughout the entire year 

 a constant succession of eggs or young forms is given off by 

 the inhabitants ' (on the bottom), ' while there is another and 

 less minute increment derived from the older forms which are 

 forsaking pelagic life to settle on the banks\' It is the vast 

 abundance of the pelagic fauna (which often has no connection 

 with the particular ground examined), for instance, that is so 

 important in regard to the food of the herring. 



Again, the forms immersed in the sand are, for the most 

 part, free from serious injury. This was pointed out, speaking 

 of certain annelids, in the Trawling Report, as follows : — ' The 

 trawl has little or no effect on such as the foregoing, for their 

 tubes in general are buried in the sand, their lives being passed 

 in boring through it — for food and for shelter. So difficult is 

 it to interfere with annelids sunk in the sand that one may 

 sweep over a sandy surface, in which rare forms lurk, again 

 and again, without discovering their presence. Even if a 

 dredge is dipped, perhaps, only a head with its tentacles 

 will reward the haul. Yet the sand may teem with them 

 from 5 fathoms shorewards, and every spadeful — at extreme 

 low water — may produce several. A single storm would appear 

 to inflict greater destruction on these than it is possible to 

 do by trawling^.' 



A careful summary of the effects of the trawl on the sea- 

 bottom and its fauna was given at the end of the chapter on 

 the 'Fauna of the Trawling- Grounds in relation to Food- 

 Fishes V and, with all the experience since gained, it is 

 doubtful if any change can conscientiously be made. The 

 only fact of moment to be stated is that it is several years 



1 Report, Royal Commission on Traioling, 1885, p. 370. 



2 Ibid., 1885, p. 368. 



3 Ibid., p. 370. 



