HOBSON and CHESS: TROPHIC RELATIONS OF THE BLUE ROCKFISH 



Figure 10.— Ctenophores off Mendocino. Beroe forskali (left), missing piece probably taken by planktivore, and Pleurobrachia hachei 



(right). Scale indicator = 1 cm. 



Event 12— The process abruptly reversed with a shift to northerlies that gusted to 30 K for 2 days, and sea temperature fell to 11.5°C 

 on 25 January. 



Event 13— In another abrupt reversal, 3 days (27-29 Januarj') of 15-25 K southerlies (with rain) resulted in sea temperature rising to 12°C. 



Event 14— Reversing again, northerlies of 12-20 K on 30-31 January drove sea temperatures down to 10.5°C, at which point (1 February) 

 the thermograph malfunctioned. Southerlies predominated while the thermograph was inoperative, and when it was reinstalled on 11 

 February, rising sea temperature 2 days later (13 February) equaled the season high of 12.5°C. But when northerlies returned the next 

 day the downwelling season began its decline. 



Event 15— Two days of 20-25 K northerlies (19-20 February) resulted in the season's largest 24-h change in sea temperatures. 



Event 16— Sea temperature rose to 11.5°C on 3 March following 8 consecutive days of 8-15 K southerlies (with rain), or weak north- 

 erlies (to 6 K). An abrupt shift followed, as 2 days of 15-25 K northerlies (4-5 March) resulted in the season's second largest 24-h change 

 in sea temperature— the first time since November that sea temperature had fallen below 10°C. 



Event 17— After a week of light variable winds, during which sea temperatures remained essentially unchanged at about 9.8°C, southerlies 

 increased to 15-20 K (on 15 March) and sea temperatures began rising to begin the final downwelling episode of the 1980-81 down- 

 welling season (which was followed by the abrupt reversal that marked the beginning of the 1981 upwelling season, see Figure 4). 



731 



