250 



Fishery Bulletin 105(2) 



for yellowfin (Masuma et al.^) and bluefin 

 tuna, Thunnus thynnus (Miyashita et al., 

 2000a). Spawning of captive yellowfin tuna 

 in landbased tanks in Bali occurred in late 

 2004 (Nakazawa^). Descriptions of larval 

 and juvenile development stemming from 

 these culturing programs have been pre- 

 sented for yellowfin tuna (Kaji et al., 1999; 

 Margulies et al., 2001; Waxier et al., 2001) 

 and bluefin (Kaji et al., 1996; Miyashita et 

 al., 2001). 



Little is known about the spawning be- 

 havior of tunas or the influence of physical 

 factors on spawning or egg and larval de- 

 velopment. Almost nothing is known about 

 the manner in which tunas aggregate for 

 spawning, their courtship and spawning be- 

 haviors, the duration of spawning events, or 

 the effects of physical variables on spawning 

 dynamics or early life stage development. 

 Since 1996, the Inter-American Tropical 

 Tuna Commission (lATTC) has maintained 

 a spawning population of yellowfin tuna 

 in large landbased tanks at the Achotines 

 Laboratory in Panama (Scholey et al., 2001; 

 Wexler et al., 2003). Our broodstock yel- 

 lowfin tuna have spawned over protracted 

 time periods (nearly year-round on a daily 

 basis) since October of 1996. This spawning 

 pattern has provided a unique opportunity 

 to study the daily spawning dynamics of 

 this species over multiple years. In this ar- 

 ticle we describe the courtship and spawning 

 behaviors of captive yellowfin tuna, their 

 spawning periodicity, the influence of physi- 

 cal and biological factors on spawning and 

 hatching, and the egg and early-larval de- 

 velopment of this species. 



20' W 



80° W 



30' N 



/"N- 



n Isla 

 ^ Iguana 



30' N 



7»N 



20' W 



sew 



Figure 1 



Location of the Inter-American Tropical Tuna Commission's 

 Achotines Laboratory, Republic of Panama. 



Materials and methods 



Development of the broodstock 



The yellowfin tuna broodstock was developed at the 

 lATTC's Achotines Laboratory, located at the southern tip 

 of the Azuero Peninsula of Panama in the northwestern 

 portion of the Panama Bight in the Pacific Ocean (Fig. 

 1). The broodstock was developed in collaboration with 

 the Overseas Fishery Cooperation Foundation (OFCF) of 

 Japan. The design of the seawater system, plus specific 

 details of the capture, handling, and feeding procedures 



2 Masuma, S., N. Tezuka, K. Teruya, M. Oka, M. Kanematsu, 

 and H. Nikaido. 1993. Unpubl. data. Yaeyama Experi- 

 mental Station, Japan Sea Farming Association, 148 Ohta 

 Ishigaki, Okinawa 907 Japan. 



■^ Nakazawa, A. 2004. Personal commun. OFCF (Overseas 

 Fishery Cooperation Foundation), Sankaido Bldg. 9-1.3, Aka- 

 saka 1, Minato-ku, Tokyo 107-0052, Japan. 



for the broodstock yellowfin tuna are described by Wexler 

 et al. (2003). We began collecting this species in coastal 

 waters in the vicinity of the Laboratory in early 1996, 

 and initially placed 55 individuals in the main brood- 

 stock tank (concrete, in-ground, 17 m diameter, 6 m 

 deep) in June and September of 1996. We captured an 

 additional 24 fish in September and October 1996 and 

 maintained them in a smaller (8.5 m diameter, 6 m deep) 

 in-ground tank as a reserve group. The tanks received 

 filtered seawater by intake lines that extended outside 

 Achotines Bay, and both tanks received biological filtra- 

 tion and partial recirculation. The water delivery for the 

 main broodstock tank flowed through an aeration tower 

 (400 m3/h) designed to aerate and degas the makeup 

 and recirculated water entering the tank. We installed 

 several translucent panels in the roof above the main 

 tank to allow exposure to the natural photoperiod. Water 

 temperature, salinity, dissolved oxygen (DO), and oxygen 

 saturation in the tanks were recorded on a daily basis. We 

 measured ammonia, nitrite, nitrate, and carbon dioxide 

 on a weekly or semi-weekly basis. 



