SEA-FISHERIES LABORATORY. 69 



in order that we may usefully control these powers of production 

 of organic substance. Many things that are apparent in present 

 economic tendencies suggest that this control over the regenera- 

 tive power of the littoral seas simply must be acquired. 



The conditions that we speak of result in a shallow sea 

 densely crowded with marine organisms that have little or no 

 economic value : mussels, cockles, and shellfish that are mostly 

 unutilised ; small plaice, dabs, flounders, solenettes, sprats, 

 etc., that are not caught ; " sea-weeds " that contain enormous 

 stores of cellulose, chitine, and other substances that might be 

 used, but are not — and so on. 



Here we are only concerned with the plaice. The quantities 

 that come into existence annually in the sea from the Solway 

 Firth down to the coasts of North Wales are probably illimit- 

 able — in the sense that fishing operations, as at present carried 

 on, do not appear to make any sensible difference in their 

 abundance. Of all the plaice eggs that are spawned in the Irish 

 Sea every year only a rather small percentage become trans- 

 formed larvae. A certain combination of conditions, tempera- 

 ture of the sea, density, strength and direction of resultant 

 tidal streams and wind drifts, certain food organisms that 

 appear just at the right time and in the right quantity, intensity 

 of sunlight, etc. — probably all these and other conditions must 

 co-operate in a timed manner in order that a large proportion 

 of the fertilised plaice eggs produced during the spawning 

 period may develop into baby plaice. Then, just for the few 

 weeks that these larval plaice are living on the very shallow- 

 sea bottom just outside tide marks there must be plenty of the 

 right kind of food organisms in the sand and in the water 

 immediately over the latter — it will be no use if this plentifulness 

 of food occurs a few weeks earlier or later than the very few 

 weeks when the little plaice come close to the shore. A certain 

 small proportion of the latter, therefore, are well fed and survive 

 for a couple of years to be caught by the inshore trawlers, who. 



