OLLA ET AI. SEASONAI, DISPERSAL. OF IlINNER AND TAUTOC 



would accept and remain at a different site. Four 

 fish captured at Site A, the perennial habitat, were 

 affi,xed with ultrasonic tags and released at either 

 of two seasonal sites. Three fish were released 

 separately at Site B (no. 5-7; Table 4) and a fourth 

 at Site C (no. 8; Table 4) and individually tracked 

 for 48 to 72 h. The fish appeared to accept the 

 transfer to a different habitat with all four fish 

 remaining within several meters of the release 

 site. 



The close association with cover exhibited by 

 fish ultrasonically monitored at both perennial 

 and seasonal habitats indicated the possibility 

 that the apparent dependence on cover might be 

 such that a fish would remain at any object that 

 afforded cover. To examine whether the presence 

 of cover was the sole determinant of habitat accep- 

 tance, we transferred a fish from Site A to a struc- 

 ture constructed of cement blocks, measuring 40 - 

 40 X 40 cm, and located on a sand bottom 50 m 

 from a habitat with which fish were associated 

 (Site F). The fish (no. 9; Table 4), during the first 5 

 min after release, circled the structure and moved 

 farther away with each circuit, showing little, if 

 any, attraction. When about 10 m from the struc- 

 ture, it swam shoreward and reached Site F about 

 5 min later. The fish remained at this site during 

 the next 24 h, showing the same degree of move- 

 ment exhibited by fish no. 3 (Table 4) which had 

 been previously captured and released at this site. 



It was possible that the fish moved from the 

 structure because of its proximity to a natural 

 habitat, therefore affording it a choice. It was also 

 possible that social factors related to the release of 

 a single fish rather than a group may have played 

 a role in the rejection of the structure as a habitat. 

 To control for these factors, we next released fish 

 in a group of 10, 4.5 km from their home range and 

 100 m from the nearest natural habitat at which 

 conspecifics were present. To broaden the scope of 

 our queries we included the possible influence of 

 factors such as food and naturally occurring cover 

 on habitat selection. Two cement block structures 

 ( 120 ' 40 > 40 cm) were placed 10 m apart. Both 

 were identical except that while one consisted 

 simply of bare cement blocks, the other contained 

 clumps of mussels and algae iUlva sp.), naturally 

 occurring food and shelter material. Two groups of 

 10 fish each (15-23 cm) captured at Site A, were 

 released together at each habitat while being ob- 

 served with scuba. Within 5 min of being released, 

 the fish left both structures, swimming away in 

 various directions. 



The habitats were then modified by the addition 

 to each of a fish trap. To the habitat which con- 

 tained mussels and algae the trap added was over- 

 grown with various fouling organisms and had 

 been in continuous use over a period of 4 to 5 mo, 

 capturing both tautog and cunner. The fact that 

 this trap captured fish consistently led us to con- 

 clude that it provided an attractive stimulus or set 

 of stimuli. The trap added to the bare structure 

 was new. A group of 10 fish ( 10-25 cm), captured at 

 Site A, was released at each habitat. As previ- 

 ously, the fish left the bare habitat within 5 min. 

 Dispersal from the other habitat was more 

 gradual with the last fish leaving about 60 min 

 after release. In all instances, the fish departed, 

 indicating that factors in addition to those pro- 

 vided were necessary for mediating habitat selec- 

 tion. 



DISCUSSION 



It was clear from the results of trapping, tag- 

 ging, and direct underwater observation that 

 some portion of the cunner and young tautog popu- 

 lations dispersed in late spring. The dispersal was 

 from the boat basin (Site A, which we termed a 

 perennial habitat) to habitats that were utilized 

 only seasonally. Once adopting a seasonal habitat, 

 the fish appeared to remain there until fall. Then 

 there was a general movement back to a perennial 

 habitat, but as was evident from the capture of 

 tagged fish at perennial sites outside of the study 

 area, not necessarily the one from which they dis- 

 persed in the spring. Once arriving at a perennial 

 habitat, the fish remained to overwinter in torpor, 

 not emerging until sometime in early spring when 

 the temperature reached 5° to 6°C (011a et al. 

 1974, 1975). 



Supporting our findings for seasonal movement, 

 Briggs (1977) found a marked increase in the 

 number of young tautog captured during the fall 

 at the Kismet artificial reef, 6 km from our study 

 area. This increase, we surmise, also reflects the 

 movement of fish from seasonal habitats to one 

 which appears to be perennial. 



In attempting to define habitat requirements for 

 both species, it is apparent that cover is a critical 

 factor. During the day when these fish are active, 

 they remain within several meters of cover, and at 

 night when quiescent and unresponsive, they are 

 either in, against, or under cover (Olla et al. 1974, 

 1975). Once becoming torpid in winter, they re- 

 main under cover until spring. It seems reason- 



259 



