FISHERY BULLETIN: VOL. 86, NO. 3 



8.4° to 14.4°C, and from 7.6° to 8.8°C at 50 m, dur- 

 ing the period 17 April to 7 July (Table 1). Warmest 

 surface temperatures were in May and July, and at 

 50 m, were warmest in June. 



Species Occurrence 



Three species of crab larvae predominated in the 

 plankton collected. The porcellanid crab, Petrolisthes 

 cinctipes, predominated in waters within 8 km of 

 shore, while C. oregonensis and C. magister domi- 

 nated in more offshore waters. Other crab species 

 were present but at much lower abundance than 

 these three species. Megalopae of C. oregonensis 

 were of comparable abundance to C. magister at 

 most stations sampled. 



Surface Abundance 



Presence of crab megalopae at the surface was 

 dependent on time of day, with slight differences 

 in timing of maximal abundance occurring between 

 the two Cancer species (Fig. 3). At 9.3 km offshore 

 in June, C. oregonensis was several orders of mag- 

 nitude more abundant and also seemed to peak in 

 abundance a little earlier in the evening and later 

 in the morning than did C. magister. Relative abun- 

 dance of both species declined in the middle of the 

 night. 



Data in Figure 3 was smoothed by eye (Fig. 4) 

 to allow megalopal abundance data from the 

 transect to be weighted by time of capture at 

 night. Multiplier values were determined, and these 

 were used to adjust actual abundance data by 

 sampling time for the May and June sampling 

 periods (Tables 2, 3). Only these data were weighted, 

 and since day length changes with time of year, ad- 



justment of data collected more than two weeks on 

 either side of 14 and 15 June was considered 

 inappropriate. 



In hindsight, some data (indicated by asterisks in 

 Tables 2, 3) was found to have been collected at a 

 time when megalopae were just beginning to reach, 

 or had just left, the surface. The calibration slope 

 (Fig. 4) is very steep at both these times and it was 

 impossible to estimate accurately a meaningful scal- 

 ing multiplier for these data. Our estimated mega- 

 lopal abundance at these stations should be viewed 

 with particular caution; a zero value may not in- 

 dicate that megalopae were absent, but only that 

 they were not at the surface. 



Bongo tows during the day poorly sampled the 

 abundance of C. magister megalopae (Table 4) 

 shown to be present by nighttime neuston tows 

 (Tables 2, 3). This was possibly due to sampling the 

 total column below only a few square meters of sea 

 surface, because of integration of the results, or to 

 avoiding the net by the megalopae. It was unlikely 

 because of failure to sample deeply enough, since 

 on the continental shelf, tow depth approached bot- 

 tom depth. Megalopae (maximum per tow was 4) 

 were primarily collected by bongo gear at stations 

 where they were abundant in neuston samples at 

 night, but relative abundance estimates obtained 

 from bongo nets are considered only useful in a 

 general qualitative sense because of the low absolute 

 numbers caught. 



Temporal Occurrence 

 (Time of Year) 



No Cancer megalopae were found in samples col- 

 lected shortly after dusk on 27 February-4 March. 

 Cancer megalopae were first observed on the next 







9 



19 



28 



37 



56 



74 



93 



111 



130 



148 



185 



8.8 

 8.8 

 8.7 

 8.8 

 8.6 

 8.7 

 8.7 

 8.5 

 8.5 



8.5 

 8.4 



8.8 

 8.7 

 8.1 

 8.8 

 8.6 

 8.7 

 8.6 

 8.5 

 8.4 



8.5 

 8.6 



7.9 

 8.2 

 8.3 

 8.2 

 8.2 

 8.2 

 8.0 



8.0 

 8.4 



12.2 

 13.4 

 13.4 

 13.1 

 13.8 

 13.3 

 11.8 

 11.9 

 11.5 



11.0 

 11.4 



9.2 



9.5 



8.6 



9.6 



9.3 



9.8 



10.0 



10.3 



10.5 



10.0 

 10.0 



7.6 

 7.9 

 7.9 

 8.2 

 8.2 

 8.2 

 8.1 



8.7 

 8.4 



12.2 

 12.2 

 12.3 

 12.8 

 12.7 

 12.9 

 12.9 

 12.8 

 12.7 

 12.7 



11.4 

 9.0 

 10.4 

 12.3 

 9.4 

 10.5 

 12.0 

 12.2 

 12.2 

 12.4 



8.0 

 8.0 

 8.3 

 8.1 

 8.7 

 8.5 

 8.5 

 8.6 



13.5 

 14.0 

 13.3 

 13.3 

 14.4 

 14.4 



11.0 

 9.0 

 10.0 

 10.7 

 13.3 

 13.3 



7.6 

 7.7 

 7.7 

 8.6 

 8.6 



530 



