82 COMMISSION OF CONSERVATION 



The entrance to the bay, whether wide or narrow, the deep channels and 

 the broad flats, the presence or absence of islands, the water brought down 

 by rivers, and all such conditions, have to be taken into consideration, as 

 well as the situation of the oyster beds, in the interpretation of the plankton 

 and in the selection of places from which to collect it. A person un- 

 informed in these matters might be confining his attention to a region 

 where there are no oyster larvse at a time when they are plentiful else- 

 where. The larvse do not by their own activity wander far from their 

 birthplace. There is a falling off in quantity depending upon the distance 

 from the centre of origin. If centres are not far apart the dispersing larvae 

 may intermingle, if the centres are distant there may be intervening 

 masses of water devoid of larvse. Plankton taken off one side of a small 

 island may contain oyster larvse while that from the opposite side does 

 not. On the way from one oyster bay to another the water does not 

 ordinarily contain oyster larvae. If it does, it is because of tide currents. 

 In going outwards into the gulf of St. Lawrence or into Northumberland 

 strait from an oyster region the larvse soon dwindle out. Over a deep- 

 water bed the numbers diminish from lower to higher strata. Storms, 

 breakers, tide currents generally cause larvae to sink, but if not too violent 

 the larvae may become habituated to them. In shallow water the dis- 

 turbance may reach to the bottom and whirl up larvae in the same way 

 that it does ooze, sand, mud, and weeds. 



In estimating the number of larvse in an area at different periods, or 

 in calculating the productiveness of different areas, it is usually sufficient 

 to make a relative comparison. This ma}^ be done by dragging a plankton 

 net through the water under the same conditions and for the same distance 

 in the different cases and measuring the volume of bivalves collected; 

 then making microscopic preparations from the under settlings by spread- 

 ing out a uniform thin layer and counting the number of oyster larvae 

 under a definite size of cover-slip or in a certain field of view. The more 

 nearly the examination can be made to cover the whole area and the 

 greater the number of tests, the more accurate will be the conclusion. At 

 the beginning of the season oyster larvae will be few and smaU, although 

 mussel and clam larvse may be plentiful and of various sizes. At this time 

 counting is difficult on account of the small size and similarity of different 

 species, but an estimation of numbers is not so likely to be required as the 

 recognition of their presence. On June 26, 1905, plankton taken up Ship- 

 yard basin (Malpeque) showed few oyster larvse; that across Keir bay 

 (out from the March water) contained many; that off Ram island few. 

 Mussels were few, clams numerous. On July 11, 1904, between Ram and 

 Curtain islands there were many oyster larvse but few mussels and clams. 

 On the 14th over the Curtain Island beds there were many oysters, few 

 mussels, more clams, and an odd quahaug or scallop. On the 27th I took 

 the best catch for the season. Most of the larvae were now grown to their 



