FISHERY BULLETIN: VOL. 75, NO. 3 



Choat 1974); and L. phthirophagus (Youngbluth 

 1968). Pair spawning has also been described in 

 Cirrhilabrus temminckii (Moyer and Shepard 

 1975), although the authors do not discount the 

 possibility that group spawnings may occur as 

 well in this species. 



Species in which only group spawnings have 

 been documented include Thalassoma lucasanum 

 (Hobson 1965); T. hardwicki (Robertson and 

 Choat 1974); and the cunner, Tautogolabrus 

 adspersus, a coresident of the tautog (Wicklund 

 1970). 



At least two labrid species have each been 

 shown to possess both modes of gamete release. 

 The bluehead, Thalassoma bifasciatum, was first 

 seen to exhibit the dual spawning behavior under 

 natural conditions by Randall and Randall (1963). 

 Robertson and Choat (1974) observed similar be- 

 haviors in T. lunare. Both T. bifasciatum (Rein- 

 both 1967) and T. lunare (Choat 1969) are pro- 

 togynous hermaphrodites, a condition ". . . in 

 which the individual functions first as a female, 

 and later in life as a male" (Atz 1964). Although 

 protogynous hermaphroditism is rather wide- 

 spread in labrids (at least 30 species mentioned by 

 Robertson and Choat 1974), until now only the two 

 species mentioned above have been identified as 

 possessing both modes of spawning. 



Our aim in this work was to examine and de- 

 scribe the various components comprising court- 

 ship and spawning of the tautog. The studies were 

 performed on adults which were held under 

 laboratory conditions in a large aquarium. 



MATERIALS AND METHODS 



Two studies, spanning the 2-yr period of 1975 

 and 1976, were conducted on two different groups 

 of adult tautog, with each group consisting of two 

 males and a female. The fish were collected during 

 late summer and early fall at Fire Island, N.Y., at 

 temperatures ranging from 19° to 24°C. Scuba 

 divers, using hand-held nets, were readily able to 

 capture the fish at night when they are normally 

 quiescent. The animals were easily identifiable 

 with respect to their gender by the sexually di- 

 morphic mandible, which is more pronounced in 

 males (Cooper 1967). 



The studies were conducted in a 121-kl, ellipti- 

 cally shaped aquarium, 10.6 x 4.5 x 3.0 m, located 

 in a temperature-controlled room in which 

 natural diurnal changes in light intensity were 



586 



simulated (Olla et al. 1967). Layers of sand (0.6- 

 0.8 mm) and gravel (2-5 mm), 0.6 m deep, pro- 

 vided a natural substrate for the fish. Beneath the 

 gravel, seawater flowed through a network of 

 pipes on the floor of the aquarium from a series of 

 external filters containing sand, gravel, and oys- 

 ter shells, and which provided continuous circula- 

 tion and filtration. Water quality in the aquarium, 

 operated primarily as a semiclosed system, was 

 also maintained by addition of seawater from 

 Sandy Hook Bay. The pH averaged 7.5, salinity 

 averaged 24.0%o, and dissolved oxygen averaged 

 7.5 ppm. 



It had been previously determined that in the 

 natural environment a shelter area is a physical 

 requirement of tautog, particularly during their 

 nighttime quiescence. Shelter was, therefore, pro- 

 vided in the form of a triangular-shaped structure 

 consisting of three clay drainage tiles (30.5 x 60.9 

 cm) cemented together. The shelter was placed 

 approximately 3 m from one end of the aquarium 

 in proximity to viewing windows. Clumps of live 

 blue mussel, Mytilus edulis (5-17 kg), a major 

 component of the tautog's diet (Olla et al. 1974), 

 were introduced periodically to insure a continual 

 food supply which allowed the fish to feed ad 

 libitum. The mussels were placed 4 m from the 

 shelter and constituted a more or less fixed feeding 

 area. 



Diurnal changes in light intensity from morn- 

 ing to evening civil twilight were simulated by 

 banks of fluorescent lights mounted on the walls 

 above the aquarium and controlled by a series of 

 timers (Olla et al. 1967). A low level of night il- 

 lumination, 0.75 lx was provided by incandescent 

 bulbs, programmed to come on before the last row 

 of fluorescent lights was extinguished. 



Aquarium Conditions During 

 Animals' Residency 



Study 1 



One male [51.5 cm TL (total length)] and one 

 female (50.0 cm TL) were introduced into the 

 aquarium on 20 September 1974, with a second 

 male (59.0 cm TL) introduced 7 days later. From 

 this point, the animals were kept in the aquarium 

 for a total of 244 days. The fish were initially held 

 at 19.1°C ( +0.8°; - 1.6°C) for 50 days. The animals 

 were then the subjects of a long-term study deal- 

 ing with the effects of temperature on activity and 

 social behavior (Olla in prep.). Beginning at light 



