FISHERY BULLETIN: VOL. 80. NO. 4 



On the basis of hundreds of observations and the 

 complete filming of 12 rushes, the spawning rush 

 may be broken down into six distinct periods: 1) 

 Pectoral swim up, 2) tail swim, 3) swim alongside 

 and tilt, 4) release, 5) circle and display, and 6) 

 swim down (Fig. 1). 



1) Pectoral swim up— A male approaching 

 from some distance a female which was up above 

 the bottom would swim upward at an angle of 

 10°-20° towards the female, using concurrent 

 sculling of the pectoral fins, usually of 2.0-2.5 

 beats/s. The dorsal and anal fins were folded 

 against the body. As he approached the female, 

 who rose slowly at a steeper angle to match his 

 ascent, the male began to turn laterally and 

 shifted to the second type of swimming. 



2) Tail swim— The male folded the pectoral 

 fins against his body and began undulating the 

 caudal fin and posterior portion of his body at 

 about 4 beats/s. Pelvic fins were usually about 

 one-half extended. The female continued to rise 

 slowly as the male approached her from behind. 

 This stage lasted about 2-5 s. 



3) Swim alongside and tilt— The male, using 

 the tail only, continued swimming and came for- 

 ward alongside the female, who was still moving 

 forward. Their bodies were close together, the 

 male slightly behind the female with his snout 

 about even with her eye (Fig. 2). Once alongside, 

 the male angled the dorsal portion of his body 

 outward at about 15°-20° from the female. This 

 took 0.5-1.5 s. During this phase, the male and 

 female turned laterally 90°-180° in the direction 

 of the female. 



4) Release — At the end of the turn to initiate 

 gamete release, the male started swimming for- 

 ward more rapidly than the female. As he over- 

 took her, he bent his body laterally towards her, 

 then broke in the opposite direction. At this time 

 the gametes of both sexes appeared to be re- 

 leased. The cloud could usually be seen, but the 

 exact moment of release was difficult to deter- 

 mine. In some cases the male, when he turned 

 toward the female, was sufficiently far forward 

 to actually cross slightly into her path. The sharp 

 break away from the female was accomplished 

 by a sharp flick of the caudal fin. This also served 



Figure 1.— Idealized spawning sequence of Lacknolaimus maximum under conditions where the female meets the male in mid- 

 water. The male (right) approaches and initiates the "pectoral swim up" action (1) followed by "tail swim" (2-3) when approaching 

 the female. The lateral turn in "swim alongside and tilt" towards the female (4-5) is followed by the "release" of the gametes (6). 

 "Circle and display" (7-8) precedes "swim down" (9). In this case the male is illustrated as returning in the direction opposite that 

 when spawning was initiated, but this is not always the case. Often the male will continue patrolling in the same direction. 



856 



