OLLA and SAMET: COURTSHIP AND SPAWNING BEHAVIOR OK TAUTOG 



onset 51 days after the three fish were placed in 

 the aquarium, the water temperature was in- 

 creased during a 9-day period (mean rate 0.04°C/ 

 h) and held for 11 days at 28.7°C ( + 0.2°; -0.1°C). 

 The temperature was then decreased over an 

 8-day period (mean rate 0.05°C/h) and held for 165 

 days from 14 December 1974 to 28 May 1975 at 

 18.7°C ( + 1.1°; -0.8°C). 



During the first 10 days of the animals' resi- 

 dency, the photoperiod was decreased from 13.18 h 

 to 12.25 h and then held constant through 22 Feb- 

 ruary 1975. Beginning on 23 February 1975 the 

 light schedule was set to conform with the natural, 

 increasing photoperiod. The interval from 14 De- 

 cember 1974 to 16 January 1975 comprised the 

 baseline nonreproductive period for Study 1. Ob- 

 servations on courtship behavior first began on 11 

 April 1975. 



Study 2 



Two males (54.0 cm TL and 55.3 cm TL) and one 

 female (47.0 cm TL) were introduced into the 

 aquarium on 28 August 1975 and kept in the 

 aquarium for a total of 225 days. They were ini- 

 tially held at 21.3°C ( + 1.9°; -1.5°C) for 80 days. 

 The animals were then the subjects of a long-term 

 study dealing with the effects of temperature on 

 activity and social behavior (Olla in prep.). Begin- 

 ning at light onset of the 81st day of the animals' 

 residency, the water temperature was gradually 

 raised over a 9-day period (mean rate 0.04°C/h), 

 held for 11 days at 28.7°C (+0.2°; -0.4°C), de- 

 creased during 8 days (mean rate 0.04°C/h), and 

 then held for 115 days from 14 December 1975 to 8 

 April 1976 at 20.2°C (±0.7°C). 



During the first 22 days of the animals' resi- 

 dency, the photoperiod was decreased from 14.23 h 

 to 12.32 h and then held constant through 2 March 

 1976. Beginning on 3 March 1976 the light 

 schedule was set to conform with the natural, in- 

 creasing photoperiod. The interval from 14 De- 

 cember 1975 to 15 January 1976 comprised the 

 baseline nonreproductive period for Study 2. Ob- 

 servations on courtship behavior first began on 29 

 January 1976. 



Observation Schedule 



Hourly observations made on the fish during the 

 light period of each study consisted of 15-min read- 

 ings. During each, the following measures of be- 

 havior (described in Results) for each fish were 



recorded for 50 counts in sequence at 18-s inter- 

 vals: 1) number of aggressive interactions be- 

 tween fish and identity of aggressive and submis- 

 sive individuals, and 2) number of courtship 

 interactions and identity of participants. Qual- 

 itative aspects of behavior were also recorded dur- 

 ing each reading. 



During the nonreproductive period, 12 hourly 

 observations (0700-1800 EST) were made daily in 

 4-day periods with intervals up to 3 days between 

 periods. A total of 28 observation days ( 336 h ) were 

 made in the nonreproductive period of Study 1 and 

 20 days (240 h) in Study 2. During the reproduc- 

 tive period 8 hourly observations (0800-1500 

 EST) were made daily. In Study 1 these were 

 taken in 2-day periods, with intervals up to 5 days 

 between periods, while in Study 2 there were 

 4-day observation periods with intervals of up to 3 

 days between each. During the reproductive 

 period a total of 15 observation days ( 120 h) were 

 made in Study 1, and 13 days (104 h) in Study 

 2. 



To compare differences in aggressive interac- 

 tions prior to and during spawning, we selected 1 1 

 typical days of observations during the nonre- 

 productive and reproductive periods of each study. 

 Data based on the hourly, means (0800-1500 EST) 

 from these days are presented in tabular form in 

 the Results. 



Once we discovered that gamete release oc- 

 curred in the afternoon on a daily basis and we had 

 become acquainted with the reproductive reper- 

 toire of the animals, we could predict approxi- 

 mately when daily spawnings would occur. There- 

 fore, in addition to the readings mentioned above, 

 we also began to observe the fish at least 60 min 

 and some days up to 150 min prior to and including 

 each spawning. In Study 1 approximately 35 h and 

 in Study 2, 25 h of observations were made prior to 

 spawnings. During 11 typical spawning days, data 

 collected in this fashion enabled us to determine 

 quantitatively: 1) if there were any changes in 

 aggression throughout the day as the spawning 

 time approached, and 2) how close (temporally) to 

 the spawnings, changes in courtship behavior 

 were manifested. 



Throughout each study and particularly prior to 

 each spawning, observations were made with the 

 use of a tape recorder. In addition, periodic motion 

 pictures taken throughout the spawning period 

 allowed us to analyze and interpret behavioral 

 components and sequences both in slow motion 

 and at stop frame. 



587 



