690 



Fishery Bulletin 101(3) 



Espiritu 



Santo 



North 



(n=7,654) 



Espiritu 

 Santo 



South 2100 



(n=1 3,754) 2159 



Time 

 Percent ^^'^^ 

 Arrivals qIOO- 



0159 



B 



0900- 

 0959 



Figure 4 



Percentage of visits by 23 yellowfin tuna at dif- 

 ferent times of day at monitoring stations ESN 

 (A) and ESS (B). Circle with dashed line indi- 

 cates an equal percentage of returns occurring 

 every hour of the day. 



Conclusions 



Twenty-three yellowfin tuna were tagged with coded 

 ultrasonic beacons during a five-month period between 

 11 April and 12 September 1998. These tunas were cap- 

 tured, tagged, and released <150 m from two monitoring 

 stations: Espiritu Santo North (ESN) and Espiritu Santo 

 South (ESS), which were separated by 500 m, at the 

 Espiritu Santo Seamount in the southern Gulf of Califor- 

 nia (24°42'N: 110°18'W). The monitors were deployed for 

 a period of .'SO months, ranging from April 1998 to October 

 2000, during which they recorded tagged tunas swimming 

 within their 150 m range of reception. The tunas ranged 

 in length between 71.0 and 155.0 cm TL and in mass from 

 7.2 to 73.1 kg. The tunas stayed at the Espiritu Santo 

 Seamount for varying time periods. Nine of the 23 tunas 

 left the seamount on the same day that they were tagged. 



Two of the nine returned to the seamount twice for a single 

 day, one within a week of tagging and another after 2.5 

 months. Five additional tunas stayed at the seamount for 

 intermediate periods, ranging from two to six weeks. Four 

 individuals stayed for longer periods of time, ranging from 

 6 tol8 months. Tunas were present at the seamount at all 

 times of the day. They moved in and out of the range of the 

 monitors, most often staying for periods <14:59 min. Fifty- 

 three percent of the visits to ESN and 37*7? of the visits 

 to ESS were of this duration. Smaller percentages of the 

 visits, 2K^ and 20'/r^ , lasted 15:00 to 59:59 min, respectively. 

 The majority of visits were <1 hour in duration and only 

 a few exceeded an hour. The intervals spent away from 

 the seamount were also brief Sixty percent of all absences 

 at ESN and 65';; of the absences from ESS were <1 hour. 

 Ninety percent of the visits to both sites were <5 hours. 

 Only 0.17c of the visits exceeded 23 hours. Tuna individuals 



