DECLINE OF THE OYSTER FISHERY 101 



leave two successors to take the places of herself and a male. But to 

 accomplish this end she is called upon to deposit something like 16,000,000 

 eggs each year of her adult life. This condition has been brought 

 about by nature and must be accepted as the most economical possible 

 under natural conditions. It goes to show the magnitude of the death-rate 

 during the period between the egg and the adult and at the same time calls 

 attention to the magnitude of the causes which effect such a colossal 

 death-rate. Brooks has stated that "If all the eggs were to live and grow 

 to maturity they would fill up the entire bay in a single season. The fifth 

 generation of descendants from a single female oyster would make more 

 than eight worlds as large as the earth, even if each female laid only one 

 brood of eggs." 



The causes that have operated under natural conditions to prevent 

 the oyster from attaining any such undue prominence are observable or 

 self-evident. There are limitations in the kinds and in the amounts of 

 accessible matters, in the ability of the oyster to make use of these matters, 

 and in the climatic, physical, and biological conditions of its environment. 

 Natural forces react with varying effects upon embryonic, larval, spat, 

 or adult stages. It is not the same cause which effects the greatest destruc- 

 tion upon each, and in some cases this depends upon a combination of 

 causes. 



The heat of the sun when applied through a layer of water hastens 

 the activities and increases the chances for life, but when it acts directly 

 upon eggs, embryos, or larvae thrown up on the beach, it dries out and 

 kills them, whereas spats and adults may withstand exposure for a consider- 

 able tidal period. Cold, frost and ice act quickly upon the younger stages, 

 but the larger spat and adults are not so vulnerable. A transference of 

 frosty air from a distance may cool the surface water and this will gradually 

 sink, but it is not likely that oysters suffer much as a result because it could 

 only be the free-swimming stages that would come in contact with the 

 surface and they can sink into lower levels when they feel the cold. The 

 transference of cold from the surface to the bottom by convection is a 

 slow process and, besides, must lose effect in sinking through warmer layers. 

 In relation to changes of the temperature of the air or of the contiguous 

 land and rocks, a mass of water, in consequence of its low specific heat, 

 acts as a great protector of life. It is different in those cases where eggs, 

 embryos, larvae, and young spat are exposed wet to cold and frost, or 

 where adult oysters are subject to the weight and grinding movements 

 of ice on the beaches of tidal waters. 



Pure river-water will kill oysters in every stage of their existence. But 

 when mixed with sea-water or alternated by the ebb and flow of the tides 

 it seems to act as a stimulant. A rain storm can have little or no effect 

 upon any stage of the oyster that is already below sea or brackish water 

 but may do great damage to those exposed at low tide. The older ones 



