SEA-FISHERIES LABORATORY. 107 



down from cultivated land and from domestic sewerage systems 

 carries essential food substances on which many lower 

 organisms feed, and these lower animals and plants are the 

 food of others, which are then eaten by the young fishes which 

 inhabit the nursery grounds. 



The tidal streams are unusually strong and tend to run 

 inwards to the Solway and Morecambe Bay from the channel 

 between Ireland and Scotland. The tidal streams coming and 

 going from St. George's Channel also tend to and from the 

 " Liverpool Bay " region — that is, the coast containing the Dee, 

 Mersey, and Kibble estuaries. Off the mouths of these are 

 extensive sand-banks, penetrated by shallow channels. Plaice 

 and other fish spawn offshore and the eggs and developing 

 larvae are carried by the tidal streams to the grounds that we 

 have mentioned. 



The extensive sand-banks in the bays and estuaries are 

 " alive " with small Crustacea (Copepods), cockles, other small 

 bivalve shellfish, and small worms. In the channels, and on 

 the foreshores where the ground is rough there are enormous 

 accumulations of mussels forming " beds " or " skears."" 

 These animals, when young and small, are eaten by plaice, 

 dabs, flounders, and other fishes, and their presence and great 

 powers of regeneration are the principal reasons why the region 

 in question constitutes one great nursery ground. The supply 

 of fish-food, represented by bottom-living Copepods, worms, 

 and small molluscs, is almost illimitable, and could doubtless 

 support a much greater fish population than that actually 

 present on the nursery grounds. This fish population itself, 

 we have reason to believe, is only a small fraction of that which 

 is theoretically possible of existence. 



In fact, such an area as that which we arc now describing 

 is certainly one of the most " productive " that exists, being 

 capable of yielding far more organic food substance than any 

 equal area of cultivated land. The annual quantity of mussel- 



