president's address. 31 



standing of the metabolism of the sea and of the possibility of increasing 

 the yield of local fisheries. 



But on studying these Danish results in the light of what we know 

 of our own marine fauna, although none of our seas have been examined 

 in the same detail by the bottom-sampler method, it seems probable that 

 the animal communities as defined by Petersen are not exactly applicable 

 on our coasts and that the estimates of relative and absolute abundance 

 may be very different in different seas under different conditions. The 

 work will have to be done in each great area, such as the North Sea, the 

 English Channel, and the Irish Sea, independently. This is a necessary 

 investigation, both biological and physical, which Hes before the oceano- 

 graphers of the future, upon the results of which the future preservation 

 and further cultivation of our national sea-fisheries may depend. 



It has been shown by Johnstone and others that the common edible 

 animals of the shore may exist in such abundance that an area of the 

 sea may be more productive of food for man than a similar area of 

 pasture or crops on land. A Lancashire mussel bed has been shown 

 to have as many as 16,000 young mussels per square foot, and it is 

 estimated that in the shallow waters of Liverpool Bay there are from 

 twenty to 200 animals of sizes varying from an amphipod to a plaice 

 on each square metre of the bottom.^' 



From these and similar data which can be readily obtained, it is 

 not difficult to calculate totals by estimating the number of square 

 yards in areas of similar character between tide-marks or in shallow 

 water. And from weighings of samples some approximation to the 

 number of tons of available food may be computed. But one must 

 not go too far. Let all the figures be based upon actual observation. 

 Imagination is necessary in science, but in calculating a population 

 of even a very limited area it is best to believe only what one can 

 see and measure. 



Countings and weighings, however, do not give us all the informa- 

 tion we need. It is something to know even approximately the number 

 of millions of animals on a mile of shore and the number of milHons 

 of tons of possible food in a sea-area, but that is not sufficient. All 

 food-fishes are not equally nourishing to man, and all plankton and 

 bottom invertebrata are not equally nourishing to a fish. At this 

 point the biologist requires the assistance of the physiologist and the 

 bio-chemist. We want to know next the value of our food matters 

 in proteids, carbohydrates, and fats, and the resulting calories. Dr. 

 Johnstone, of the Oceanography Department of the University of 

 Liverpool, has already shown us how markedly a fat summer herring 



-" Conditions of Life, in the Sea, Cambridge Univ. Press. 1908 



