FISHERY BULLETIN: VOL. 86, NO. 3 



1983) and for the years 1969-70 along a transect 

 off Newport, OR (Lough 1975, 1976). These studies 

 suggest that while larvae are hatched in the near- 

 shore, shallow-water environment preferred by 

 adult Dungeness crab, they subsequently move 

 alongshore and offshore, and then inshore, often 

 over considerable distances. Larvae hatched off 

 California and Oregon in late winter have been 

 hypothesized to move northward with the Davidson 

 Current before its reversal in March- April, and off- 

 shore as a result of upwelling, Ekman transport, 

 estuarine runoff, and geostrophic flow, depending 

 on location and season (Lough 1976; Wild and Tasto 

 1983). Later stage zoeae are typically found pro- 

 gressively further offshore, and it seems to be the 

 megalopal stage that returns inshore (Lough 1976; 

 Reilly 1983). The megalopal stage is the strongest 

 swimming stage (Jacoby 1982), but there is no direct 

 evidence to indicate that their inshore movement is 

 active. 



There are five species of crabs of the genus Cancer 

 in British Columbia (Hart 1982), and larvae of C. 

 oregonensis also occur in abundance in offshore 

 waters along with C. magister (Lough 1975). Cancer 



oregonensis has no commercial importance, but since 

 it occurs with C. magister, data on both species of 

 crabs are included in this study. Comparisons of 

 occurrence between the two species may provide 

 insight into possible environmental mechanisms or 

 processes that influence transport from offshore 

 areas to the inshore juvenile habitats, which the lar- 

 vae of both species must reach. 



This study establishes the seasonal and spatial 

 occurrences of Cancer megalopae along a transect 

 over and beyond the continental shelf off the west 

 coast of Vancouver Island (Fig. 1). The geograph- 

 ical area is of particular interest because of the loca- 

 tion of a major regional crab fishery near Tofino 

 (Jamieson 1985; Noakes and Jamieson 1986) and the 

 resulting importance of understanding factors influ- 

 encing the magnitude of local larval crab settlement. 

 The oceanography off Vancouver Island has been 

 relatively well studied (Freeland et al. 1984; Thom- 

 son 1981), and because of the intrusion of Juan de 

 Fuca Strait waters into the general longshore ocean- 

 ographic regime and the relative increase in topo- 

 graphical complexity of the continental shelf, it is 

 considerably more complicated than that found 



Figure 1.— The survey transect line, with stations, over which this study was conducted. 



526 



