FISHERY BULLETIN: VOL. 72. NO. 1 



susceptibility to environmental stress. The prob- 

 ability that fish would be able to respond and 

 escape potentially lethal environmental pertur- 

 bations during the inactive night phase would 

 be less than if the same stress were applied dur- 

 ing the day. Physiological responses would also 

 differ. Differential susceptibility to stresses as 

 related to the daily rhythm has been clearly 

 established (for discussion and review, see 

 Reinberg. 1967). 



During most of the summer and into early 

 fall, fish of the colony we studied had a fairly 

 well defined home range (Gerking, 1959) with 

 the basin acting as a focal point or home site, 

 providing a suitable night habitat for all-sized 

 fish. While larger fish (^30 cm) moved out 

 each day to feed, the smaller fish (^25 cm) 

 foraged along or in close proximity to the 

 basin walls. The adaptation of young fish re- 

 maining close to the home site may relate to 

 effectively protecting them against predators. 

 On one occasion while diving in early July 1972, 

 we observed three striped bass {Moroue .sa.r- 

 atilis, 80-90 cm) actively pursuing and attempt- 

 ing to capture young tautog (^25 cm) from a 

 group of 30 to 40. The tautog were within 1 m 

 of the basin wall at the onset of the attack. 

 They escaped from the predators by swimming 

 directly to the wall where they remained in 

 crevices. The older fish, not as susceptible to 

 predation, moves out to feed, resulting in a 

 fuller utilization of the potential energy re- 

 sources of the area and in the probable reduc- 

 tion of feeding competition among individuals. 

 The reduction in the probability of feeding com- 

 petition seemed especially critical since all 

 sizes studied preferred, to a large extent, simi- 

 lar-sized mussels. This daily movement of the 

 larger fish out of the basin also seemed to make 

 the home site a nursery for young fish. 



Our obsen^ations that tautog larger than 30 

 cm (approximately 5 yr or older) were not 

 present in the vicinity of the basin after the 

 end of October circumstantially agree with the 

 finding of Cooper (1966) that Narragansett 

 Bay fish of similar size wintered offshore. In 

 contrast, our results showed that younger fish 

 remained inshore throughout the year, winter- 

 ing at the home site in a torpid, nonfeeding 

 state. It is apparent that the younger fish are 

 highly dependent on the home site throughout 

 the year for at least the first 3 to 4 and perhaps 

 5 yr of their life. The habit of remaining inshore 



over. the winter is not unknown in labrids. 

 Green and Farwell (1971) found various-sized 

 cunner, Tautogolabrus adspersus, lying in a 

 torpid state inshore when temperatures fell 

 below 5°C. 



Although tautog feed readily on other types 

 of food, the most abundant food available and 

 found most frequently in the digestive tract 

 was mussels. Mussels were predominantly less 

 than 30 mm long, indicating an average age of 

 1 to 2 yr (Savage, 1956). The next most abun- 

 dant food found in the digestive tract was vari- 

 ous crustaceans, with only negligible amounts 

 of other items. It seemed that, on the basis of 

 our diving observations, the crustacean popula- 

 tion, in terms of a potential alternate food 

 source for the tautog in this area, did not ap- 

 proach the abundance of mussels in the 1 to 2 

 yr class. We surmise that the equilibrium of the 

 population, in terms of food resources, is highly 

 dependent on a single food item, with no alter- 

 nate potentially serving as a sustaining element. 



Environmental perturbations that would 

 directly affect 1- to 2-yr-old mussels or any of 

 the pre-adult stages, would lead to a high prob- 

 ability of stress in the tautog population. This 

 would be especially true for young fish (3 yr or 

 less) since they seem especially dependent upon 

 the home site. This dependence on the home site 

 raises the question of whether or not it is 

 within their capability to move out and seek 

 new feeding areas and if so, how successful 

 would they be. 



Another obvious limiting element of the 

 population is a suitable physical structure 

 which all-sized tautog require during their 

 night inactive phase and upon which young 

 tautog seem totally dependent. In areas where 

 food resources are in relative abundance to 

 support a population, the introduction of a 

 suitable physical habitat could lead to the es- 

 tablishment of new discrete colonies. 



ACKNOWLEDGMENTS 



We wish to thank the U.S. Coast Guard, Fire 

 Island, New York, and Charles Entenmann for 

 their assistance and cooperation. Our apprecia- 

 tion is extended to James Johnson, National 

 Marine Fisheries Service, and Case Groot, 

 Fisheries Research Board of Canada, for their 

 advice and encouragement concerning the ultra- 

 sonic tracking portion of the study. In addition, 



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