FISHERY BULLETIN: VOL. 75. NO. 2 



TABLE 3. — Summary of duration and distance tracked and mean 

 speed of albacore tracked with ultrasonic transmitters. 



'bl s body lengths per second. 

 2 0500-1900 h. 

 3 1900-0500 h. 



15 16 17 

 TEMPERATURE °C 



FIGURE 1. — Percent of time (hours) spent in waters of various 

 sea surface temperature by albacore numbers 4, 5, and 6. 



for nearly an hour when the moon was suddenly 

 obscured by dense fog at about 0300 h. 



The mean swimming speeds calculated from the 

 tracking experiment are close to estimates of 

 swimming speed derived from passive tagging 

 results. For example, based on data given in the 

 Japanese Fisheries Agency (1975) report, two 

 tagged albacore, which were released in the 

 western North Pacific and recovered in the 

 eastern North Pacific about 3V£ mo later, traveled 

 at 1.1 knots (57 cm/s), assuming they followed a 

 great circle route and were caught the day they 

 arrived at the recovery location. The mean 

 swimming speeds found in this study are slightly 

 less than twice the calculated minimum swim- 

 ming speed necessary for an 80-cm albacore to 

 maintain hydrostatic equilibrium (Dotson 1977). 



Relationship of Albacore Movements to 

 Sea Surface Temperature 



The movements of the fish tagged with ultra- 

 sonic transmitters appeared to be influenced by 

 the distribution of sea surface temperature. 

 Figure 1 shows the percentage of the time that fish 

 numbers 4, 5, and 6 spent in waters of various 

 surface temperatures. Fish number 6 spent no 

 time in water with surface temperatures less than 

 15.0°C although roughly 20<7r of the waters 5 nmi 

 distant on both sides of the path followed by the 

 fish were colder than 15.0°C. Fish number 4 was in 

 water which had surface temperatures colder 

 than 15.0°C 12.5% of the time, while 35% of the 

 waters 5 nmi distant on both sides of the path 

 followed by the fish was colder than 15.0°C. Fish 

 number 6 was in water with surface temperatures' 



350 



warmer than 17.0°C 229c of the time, which 

 coincided with the percentage of area with 

 temperatures greater than 17.0°C. Water with 

 temperature higher than 17.0°C was not available 

 to fish numbers 4 and 5. 



These results indicate that the transmitter- 

 tagged fish spent very little time in water with 

 surface temperatures less than 15.0°C. This is 

 especially evident when charts showing the tracks 

 followed by the fish and the contoured field of sea 

 surface temperature observed by David Starr 

 Jordan at the time of tracking are examined. 

 Figures 2, 3, and 4 show tracks followed by fish 

 numbers 4, 5, and 6, respectively, and sea surface 

 temperature. In these figures, temperatures less 

 than 15.0°C, which are considered below the habi- 

 tat preference for albacore (Clemens 1961), are 

 shaded. Fish number 4 remained in the vicinity of 

 a band of water cooler than 15.0°C for nearly the 

 total time it was tracked, but did not appear to 

 enter it (Figure 2). Fish number 6 traveled on a 

 southerly course, in a corridor of warm water 

 which was sandwiched between two wedges of cool 

 water on 25 August, but did not enter the cool 

 water on either side except very briefly at the start 

 of tracking (Figure 4). When the fish passed to the 

 south of the cool water, where there was a large 

 area of water warmer than 15.0°C, the fish 

 changed its direction generally to a more south- 

 westerly course. 



Relationship of Albacore Movements to 

 Upwelling Temperature Fronts 



A well-developed temperature front occurs at 

 the boundary between cool, biologically rich 



