FISHERY BULLETIN: VOL. 75, NO. 3 



curred right up until and after each spawning. The 

 subordinate male continued to be restricted in its 

 movements by the heightened aggression directed 

 towards it and remained almost exclusively at 

 either end of the tank, usually in midwater. The 

 female, besides showing a minimal change in 

 shading (i.e., early saddling, Figure la), as well as 

 an occasional responsiveness to the dominant, also 

 engaged in activities not directly related to spawn- 

 ing, such as feeding, swimming (with no apparent 

 interactions with the other animals), and resting. 



While the female either briefly followed after 

 and/or rested near the dominant or exhibited no 

 response to the rushes prior to this period, as the 

 morning progressed she responded with progres- 

 sive shading changes of varying magnitude. For 

 example, within several seconds after a vigorous 

 rush by the dominant male, the saddle oftentimes 

 increased in depth and width. On some occasions 

 the saddle took on a pale yellowish hue. The an- 

 terior half of the dorsal fin became a mottled 

 white, ending at the same posterior border as the 

 saddle. In addition, faint, white vertical stripes 

 became evident on the caudal areas of the body, 

 originating at the posterior edge of the saddle and 

 extending just past the caudal peduncle (Figure 

 lb), similar to that described by Bridges and 

 Fahay (1968). The pattern could vary, with these 

 stripes modified into a kind of" checkerboard. 

 Along with this shading, the female often erected 

 her dorsal fin very briefly (1-2 s) immediately 

 following a rush. 



Unless spawning was imminent, i.e., occuring 

 within 15 to 30 min, these shading changes in the 

 morning were retrogressive. A particular pattern 

 might not last for more than 10 to 20 s or, at the 

 longest, several minutes, followed by fading, with 

 only a thin saddle persisting. 



During the afternoon as the time of spawning 

 approached (30-60 min prior to spawning), the 

 dominant male became more responsive to the 

 female, as evidenced by the increased intensity of 

 the rushes. As these continued the female began to 

 erect the dorsal fin for progressively longer 

 periods, anywhere from 5 to 15 s. During fin erec- 

 tion the total area of white spanning the saddle 

 and the dorsal fin was now maximized and, we 

 believe, served to increase the female's conspicu- 

 ousness. 



In this same period she began to swim at times 

 only with the pectorals and also intermittently 

 began to flex the caudal fin upward. When caudal 

 flexion first began, it usually followed a rush and 



592 



was accomplished by a series of small lifts in which 

 the female raised the caudal fin progressively 

 higher. 



The responsiveness of both the male and female 

 was at its peak for the 15 min prior to spawning. 

 While the number of rushes during each of the 

 15-min hourly observations throughout the day 

 averaged 1.2 (Study 1) and 3.3 (Study 2), the 

 number of rushes in this 15-min period preceding 

 a spawning increased to an average of 6.4 (Study 

 1) and 9.4 (Study 2). Aggression by the dominant 

 towards the subordinate male was not sig- 

 nificantly different between morning and after- 

 noon for Study 1 (P>0.05), but increased sig- 

 nificantly in the afternoon of Study 2 (P^0.05; 

 sign test; Dixon and Mood 1946; Table 2). 



During the 15-min period prior to spawning, the 

 saddle of the female was almost maximally de- 

 veloped, appearing whiter than it had been earlier 

 in the day, and extending fully down the abdomen. 

 The caudal checkerboard or striped pattern was 

 now much more clearly defined. In addition the 

 vent began to dilate. 



The behavior of the female also began to change. 

 She was now more active, and often swam by using 

 only the pectoral fins. When the male moved 

 rapidly towards her in a rush, she often erected the 

 dorsal fin and flexed the caudal fin before the male 

 had reached her rather than afterwards. The du- 

 ration of the upward caudal flexion continued to 

 increase. Accompanying the caudal flexion was 

 the forward tilting of the body at about a 20° to 30° 

 angle, serving to expose maximally the dilated 

 vent. 



TABLE 2. — Sign test comparing mean number of agressions per 

 hourly observation by dominant male towards the subordinate 

 male Tautoga onitis during the morning (0800-1100 EST) and 

 the afternoon (1200-1500 EST) on 11 spawning days of Studies 1 

 and 2. 



