SEAWATER OBSERVATIONS ON THE PACIFIC COAST OF CANADA 709 



regular sequence of monthly mean temperatures at these stations for 

 this year (Fig. 10) . The more regular 1951 "offshore" conditions were 

 associated with a regular decrease of monthly mean temperatures at 

 these same stations from Amphitrite in the south to Langara in the north. 

 Although the oceanographic surveys were conducted during the months 

 of August and July, the sequence of coastal temperatures for each year 

 showed the same pattern as that following in August; so it should be 

 possible to predict changes in the oceanographic state of the "offshore" 

 waters from an examination of the surface temperature trends exhibited 

 by these daily seawater stations. 



During the summer of 1950 there was an excellent tuna fishery off 

 the Canadian Pacific Coast. In the following summer, 1951, very few 

 tuna were caught in the same area. Tuna are a warm water fish and 

 their occurrence in Canadian Pacific waters could be due to the warm 

 water cloud circulation observed in the August 1950 oceanographic sur- 

 vey previously mentioned (Fig. 8). A correlation between the varia- 

 ble "offshore" temperature distribiuion of 1950 and 1951 and the sea- 

 ^vater temperatures measured at coastal sampling stations has been pos- 

 tulated. The value of this correlation will be immeasurable if it can be 

 extended to serve as a means of prediction of the availability of tuna 

 to the fisheries in this marginal region. 



Daily Seawater Observations Assist Fisheries Investigations 

 Fisheries biologists are finding significant correlations between 

 changing ocean conditions and fluctuations in the availability of fish. 

 These studies have only been instituted in recent years because of the 

 inadequate catch statistics for previous years. The scope of these studies 

 covers the effect of ocean environment on spawning populations, juve- 

 nile fish and adult migrations. It has been demonstrated that the daily 

 seawater observations can be used to monitor the changes in the con- 

 ditions of the sea in the several climatic regions on the Pacific Coast. 

 It is now only a short step to the next logical phase of using these daily 

 observations to assist in the prediction of fish availability. 



Investigations have already been made into the possibilities of a 

 correlation between the July sequence of coastal station temperatures 

 and the offshore tuna fishery, with quite encouraging results. The tuna 

 fishery for 1952 was as unsuccessful as that for 1951, and an examination 

 of the July and August mean temperatures for the same four coastal 

 stations showed a similar characteristic of a regularly decreasing tem- 

 perature from south to north. It was not possible to make an offshore 



