18G THE PRODUCTIVITY OF THE SEA [PART II 



The stunted mussels measured, when transplanted, If to 

 IJ inches in length and 4634 bags were re-deposited. Each bag 

 contained on the average some 7000 mussels. Therefore about 

 32 millions of the shellfish were dealt with. 



Now we cannot assume that all these mussels survived in their 

 new home. Probably not less than half of them did so. The rest 

 were doubtless smothered by sand and mud, or destroyed by 

 starfishes, boring molluscs, sponges, worms, &c. We will assume 

 that 16 millions survived and underwent growth. 



The average weight of the dry organic substance (excluding 

 that of the shell) of one of the stunted mussels 1| inches in length 

 was 0*598 gram. The average weight of dry organic substance in 

 one of the same mussels of 2^ inches in length after transplantation 

 and growth (also excluding the shell) was 1*311 gram. Therefore 

 the average gain in dry organic substance was 0*713 gram per 

 musseP. This represents the growth during a period of about 

 eight months. Probably this period (April — November) represents 

 the principal growing period of the year, but nevertheless there 

 was probably some grow^th also during the winter months. The 

 area of Ringhole is 10 hectares or 25 acres. Now calculating 

 the gain on 16 millions of mussels we find that the productivity 

 of Ringhole in dry organic substance was 



1140 kilogrammes per hectare; 



or 9 cwts. per acre. 



I do not doubt that this is a minimum estimate. We must 

 remember that there is a certain amount of fishing for sea-fish in 

 the same area. This is small but only because the fish which 

 might have been caught there (dogfishes chiefly) had little economic 

 value. Then a very considerable bulk of invertebrate life, and 

 also planktonic life, not capable of utilisation by the mussels, must 

 also have been produced. There is a strong tidal flow in and 

 out of Ringhole, and since more of the ultimate food stuff of 

 animals (plankton) was probably produced in Ringhole than in the 

 open sea of Morecambe Bay it is the case that the inshore area 

 was probably depleted to some extent by the tidal circulation. 



^ This weight will obviously vary with the conditions of the shellfish, i.e. with 

 regard to spawning. 



