28 DEPARTMENT OF THE NAVAL SERVICE 



6 GEORGE V, A. 1916 



(1) The most suitable surface of attachment for kelp consists of a stony or 

 rocky bottom at a depth of from 3 to 6 or 8 fathoms (in Canadian waters). "Most of 

 the large plants of kelp that I have seen were growing in from 4 to 6 fathoms of 

 water (low-tide measurement). Apparently the nature of the rock has something to 

 do with the result, presumably through the surface it possesses. Sandstone and lime- 

 stone rock-bottoms are usually devoid of kelp. Conglomerate and granite are favour- 

 able. Kelp need never be looked for along sandy or shingly shores, nor where there 

 is a mud bottom. 



(2) Kelps flourish most luxuriantly where there is a maximum tidal current of 

 from .3 to 5 knots an hour. Beds are found where there is much slighter water move- 

 ment, but, generally speaking, the less the movement of the water,~the less luxuriant 

 is the kelp growth. I have observed no growth of kelp where the " tide-rip " reaches 

 a maximum of 6 or more knots an hour. Apparently Macroc7jstis grows preferably 

 in somewhat stronger currents than Nereocystis (see the remarks on the kelp growth 

 in Barkley sound and oif Banks island below). 



Salinity is one of the chief determining factors of the growth of kelp. It does not 

 grow in brackish water (see the results for Howe Sound, etc.). Nereocystis can 

 apparently attain a moderate size in water of less than two-thirds ocean salinity (mean 

 density 1-019) and where the salinity occasionally sinks temporarily to much lower 

 values (density 1-013, for example), but both length and weight increase distinctly 

 with increased salinity, as will be shown below. Macrocystis does not grow at all until 

 a higher salinity is reached. While Macrocystis has been observed in Barkley sound, 

 with density of the containing water as low as 1-0185, too few readings were taken to 

 determine the average value with accuracy (1-0195 for three readings). The average 

 of readings off the north coast of Vancouver island, where Macrocystis is common, 

 was 1-022, and the lowest figure observed 1-021. 



(4) The effect of temperature is less certainly demonstrable. According to 

 Setchell," temperature is one of the chief factors affecting the distributing of different 

 species, but there seem to be no available data bearing on the effect of temperature on 

 the growth of particular species. In sheltered bays in the strait of Georgia, where 

 local bodies of water attain a moderately high temperature (60° to 65° F.) for a month 

 or more at the height of summer, disintegration of Nereocystis appears to commence 

 sooner than usual. 



LIFE-HISTORY OF " NEREOCYSTIS " AND " MACROCYSTIS.'' 



Nereocystis is a yearly plant, growing rapidly in spring, reaching maturity in 

 July or later, and then decaying at a greater or less rate. Many plants are torn away 

 from their anchorages, and the beds considerably depleted in this way with the onset 

 of winter storms. Others probably decay till the pneumatocysts burst, and the plants 

 then sink. The beds are thickest from July to September or October. Many are 

 probably visible throughout the year, the young plants attaining some size before 

 the older plants have completely disappeared. 



The plants are propagated asexually by spores. The exact time at which the 

 spores are set free is a matter of importance, since it must be taken into consider- 

 ation in fixing the best time to cut the beds. According to Rigg,^ kelp plants can be 

 cut after July 15 without interfering with spore-discharge and so with next year's 

 crop. This conclusion is based on observations in the Puget Sound region. As far 

 as I could judge, in more northern waters the plants reach full size at a slightly later 

 date, and it might be desirable to defer cutting until a somewhat later period. More 

 information is required on this point. 



• Setchell, ibid., pp. 135-137. 

 ' Rigg, ibid., p. 186. 



