FISHERY BULLETIN; VOL. 77, NO. 1 



able to assume that dependence on cover is related 

 to protection from predation. Large adult tautog, 

 not as vulnerable to predation because of their 

 size, move away sometimes considerable distances 

 from cover each day to feed (011a et al. 1974). 



With such a strong tendency to remain in prox- 

 imity to cover, the question arises as to what 

 causes a portion of the population to disperse. It is 

 clear that environmental factors are changing 

 with season as are the requirements of the fish. 

 Both species in the spring have emerged from 3 to 

 4 mo of torpor, which has required them to live on 

 stored energy reserves. The need for food arising 

 from winter deprivation, coupled with the in- 

 creased metabolic requirements resulting from 

 the increase of temperature in late spring, might 

 stimulate feeding and the competition for food. At 

 least until June, the major dietary component for 

 both species is Mytiltis cdulis 1 011a et al. 1975), 

 and thus competition for food would be both intra- 

 and interspecific. 



The spawning season for cunner also peaks dur- 

 ing June (Dew 1976). Thus we can e.xpect that 

 competition for participation in either group 

 spawning (Wicklund 1970) or pair spawning (Pot- 

 tle and Green'*) would increase. This increase 

 would relate either to participation in gamete re- 

 lease or male territoriality as related to pair 

 spawning. Although the majority of tautog 

 studied were immature and would generally not 

 be involved in the reproductive competition, it is 

 possible that the arrival from offshore of adults 

 that are in spawning condition (011a et al. 1974) 

 and which we know to be highly aggressive (011a 

 and Samet 1977; 011a et al. 1977) may also play a 

 role in the dispersal of the smaller fish. 



Competition in both species is manifested 

 through aggression (for tautog, OUa and 

 Studholme 1975; 011a et al. 1977, 1978; for cunner, 

 011a and Bejda unpubl. field and laboratory obs.). 

 The increase in aggression that may occur at the 

 perennial habitat as a result of competition could 

 cause this site to become suboptimal, at least for 

 some portion of the population. Seasonal changes 

 in levels of aggression within a population might 

 result in corresponding seasonal changes in the 

 carrying capacity of the habitat. 



"Pottle.R. A.,andJ. M.Green. 1978. Field observation.s on 

 the reproductive behaviour of the cunner, Tautogulahrux 

 adspersus (Walbaumi. in Newfoundland. Unpubl. manuscr., 

 27 p. Department of Biology and Marine Science.s Research 

 Laboratory, Memorial University of Newfoundland, St. John's, 

 Newfoundland A13 3X9. 



260 



Support for the idea that fish will leave a subop- 

 timal habitat is reflected in the results of the 

 transfer experiments where young tautog left the 

 cement block structures provided for them. Simi- 

 lar results were obtained with juvenile cunner 

 (Olla unpubl. obs.). In attempting to examine the 

 mechanism for habitat selection in the manini, 

 Acanthurus triostegus sandvicensis , Sale (1969b) 

 performed a series of laboratory experiments and 

 concluded from these that there was a higher in- 

 tensity of exploratory behavior exhibited when 

 animals were subjected to an inadequate envi- 

 ronment. Similarly, it could be concluded that 

 young tautog were showing greater exploratory 

 behavior when they left the experimental cover 

 provided for them. A portion of the fish that dis- 

 perse will be lost, with the probability of survival 

 decreasing as the amount of time taken to find a 

 suitable habitat increases. Nevertheless, through 

 this mechanism, fish are able to utilize seasonally 

 available resources. 



The return to perennial habitats from seasonal 

 ones in the fall may also be related to these becom- 

 ing suboptimal for the fish, but for different 

 reasons than those which caused dispersal in the 

 spring. At habitats which exist only seasonally, as 

 in the case with macroalgae and eelgrass beds, the 

 actual cover that these beds provide begins to 

 wane as they start to die back in the fall. Although 

 some sites were structurally more permanent, 

 such as Site B (the submerged pipe), the animals 

 did not use them as perennial habitats, and the 

 changes which were occurring to render them sub- 

 optimal were not obvious. Besides changes in the 

 environment, of prime importance for considera- 

 tion is the change in the animals' requirements for 

 cover. What served adequately in summer is not 

 adequate for winter. 



In observing cunner and young tautog in the 

 field during winter torpor, both species were found 

 in deep recesses and often buried under several 

 millimeters of sand, farther under cover than ob- 

 served during nighttime quiescence in summer. 

 This afforded them greater protection during the 

 winter. The seasonal sites studied did not provide 

 cover equivalent to that at perennial ones, which 

 have numerous deep crevices and holes. 



Laboratory studies on adult tautog confirm the 

 change in cover requirements during winter tor- 

 por (Olla etal. 1977; 01 la and Studholme 19781. As 

 temperature declined, the fish began to show an 

 affinity for those structures which would serve as 

 cover during the winter at least 1 to 2 wk before 



