60 D3PARTMENT OF THE NATAL SERVICE 



8 GEORGE V, A. 1918 



larger compartments of the pound, or pond, the ill-effects may not become apparent 

 for several months, but slowly and surely the lobsters' health and vitality are under- 

 mined and tbey finally succumb to the adverse conditions. 



No doubt, by a long course of breeding and artificial selection, it might be pos- 

 sible, in the case of the lobster, just as in the case of our domesticated animals, to 

 breed a stock that would be less sensitive to the ill-effects of confinement, but, until 

 we have bred such a strain, the nearer we can make the conditions of confinement 

 approximate to the conditions in which the animal lives in the sea, the lower will be 

 the mortality. 



MUDDY BOTTOM. 



Next to the copious growth of weeds, blinding and encumbering the lobsters 

 which had wintered at Long Beach, perhaps the next most unfavourable condition 

 was the mud. There is, of course, mud and mud. Every lobster fisherman knows 

 perfectly well that during winter and early spring the largest catches are made off 

 shore, on muddy or sandy bottom. In late spring or early summer the fishermen 

 move their traps towards the shore, and find the best fishing on rocky bottom along 

 the side of kelp or other kinds of sea-weed. But, while the lobster finds a congenial 

 home on a soft sea-bottom, it does not follow that the animal, when compelled to pass 

 the winter in Long Beach pound, necessarily finds the mud therein equally congenial. 

 The mud of the pound has a disgusting odour, largely due to the gas, sulphuretted 

 hydrogen. Every one who is familiar with this gas knows its characteristic odour, 

 and the characteristic odour could be obtained anywhere in the central area of the 

 pound Ity simply driving a wand down into the mud. For example, at low water on 

 the morning of August 8 a spruce wand six-sixteenths by seven-sixteenths was pushed 

 5^ feet into the mud by the mere pressure of the hand. This was at the north end of 

 our engine house. At the south end, 3 feet were found. At the south end of our 

 hatching boxes, 5 feet. At all points, on withdrawing the wand, the characteristic 

 odour of sulphuretted hydrogen was experienced, and the adherent mud had all the 

 appearance of a sulphide precipitate. 



That the gas was really sulphuretted hydrogen became evident in another way. 

 The gas-ladened mud blackened any board, oar, or boat that was painted with white 

 lead, and which remained in contact with the mud for a few hours. Moreover, it 

 precipitated soluble salts of silver, copper, iron, etc., and there is no doubt that the 

 surface of the gill filaments were darkened and their function partially destroyed by 

 sulphides or other particles of mud. In this way it is easy to understand how the 

 gills of lobsters in the pound gradually turned, first, to a grey colour, and finally 

 became almost black. 



Dr. MoGill, chief analyst of the Inland Revenue laboratory, Ottawa, made an 

 examination of the mud, the super-natant sea-water, and the gills of an adult lobster 

 which had died in the pound. He reports as follows: ''The mud is chiefly silica, with 

 a considerable amount of inter-mixed sulphide of iron. The gills of the lobster con- 

 tained iron and phosphates, with a possible trace of sulphur." 



Dean Goodwin, D.Sc. of the Kingston School of Mining, reports a similar finding 

 to that of Dr. McGill. 



MORTALITY. 



The severe conditions under which the animals passed the winter seem to have 

 affected their general health and caused a rather high death-rate. Of course, it is 

 quite impossible to estimate the death-rate among lobsters in their natural habitat. 

 In the sea, allowance must be made for those that die of hunger, or are killed by 

 enemies. In the pond and pound the adults have no enemies, and, consequently, 

 should show a low rate of mortality, otherwise there would be no reason for placing 

 them in sanctuaries. We can only form an idea of the rate of mortality in sanctuaries 



