number taken below 57° F. was only 3.5 percent of the summer's catch. In certain 

 areas where a large amount of feed is present, it is likely that the fish will 

 cross over to feed in these colder bordering regions; however, tuna taken in water 

 below 57° F. were seldom far from the warm water. The possibility of albacore 

 being present in large numbers in the colder waters, but not actively feeding, was 

 not supported by results of the gill-net fishing. 



An examination of figure 35, showing water temperatures off the Wash- 

 ington and Oregon coasts from September 13 through 26, indicates temperatures 

 favorable for tuna, although no catches were recorded durin;; this period. Warm 

 v/ater does not necessarily insure the presence of albacore, and while the main 

 barrier to determining the extent of the tuna' s habitat in the northeast Pacific 

 is probably water temperature, the distribution and the abundance of fish in any 

 area may be more closely related to availability of feed. 



Fishing operations in Alaska waters extended from Prince of Wales Island 

 to within 100 miles of Cape St. Elias, but water temperatures were generally cold 

 and catches of albacore were confined to the region paralleling Dixon Entrance. 

 An examination of the chart (fig. 34) showing isotherm and catches- in southeastern 

 Alaska during late August shows a definite offshore trend of the 57 isotherm in 

 this region. If the conclusions reached earlier in the paper as to the effect of 

 water temperature being a limiting factor are correct, it would seem improbable 

 that tuna \-flll be found in the colder waters north of Dixon Entrance in sufficient 

 quantities to warrant exploitation. These observations would probably hold true 

 in an average year, but it is possible that in some years oceanographic and mete- 

 rological conditions may prevail which would produce warmer v;ater farther to the 

 north. 



The northerly progression of warm water as referred to above does not 

 imply a mass movement or northerly current of water but has reference to the sea- 

 sonal warming tendency in the geographical regions mentioned. A clearer picture 

 of this warming of surface water in the northeast Pacific can be attained by re- 

 ferring to fif^ure 36. This chart plots the position of three U, S. Coast Guard 

 weather ships off the Pacific coast. Surface temperatures were recorded daily 

 from these stations and the mean weekly temperatures were computed and are graphed 

 adjacent to each station. Data for Ocean Station Oboe are incomplete as this sta- 

 tion did not maintain a fixed position after the latter part of July. 



On examination of the mean water t emperatures at Ocean Station Peter, it 

 will be noted that there is a steady rise in water temperature until late August, 

 when a sharp drop is recorded. This drop coincides with three intense summer 

 storms in the Gulf of Alaska, which took place between August 24 and September 1. 

 These summer storms play an important part in the cooling of surface waters by 

 wind-mixing and interchange of warm surface layers with cooler underlying water. 

 Because of the relative steepness and the shallow depth of the thermocline in the 

 north Pacific waters as compared vdth more southern waters, the effect of v/ind- 

 mixing upon the surface temperatures will be much more pronounced in this region. 



It is interesting to note that the maximum summer surface temperature 

 recorded at Ocean Station Peter is only 55° F., while water temperatures in the 

 same latitude, closer to shore, off Vajicouver Island were recorded as high as 

 61 F., and surface tanperatures off the northern Queen Charlotte Islands were re- 

 corded up to 58° F, This would indicate a "pouching" or "sandwiching" of warm 

 water north along the continental edge of the north Pacific coast. This condition 

 is closely supported by the data collected by the Canadian oceanographic vessel 

 HMCS Cedarwood in August 1950 (Waldie and Doe 1950) . This occurrence of warm water 



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