FISHERY BULLETIN: VOL. 73, NO. 4 



the substrate surface. On a vertical substrate, they 

 may swim up and down and from side to side, 

 slowly searching an encrusted pile or bulkhead 

 wall for food. When a food item is sighted, the fish 

 grasps and ingests it as well as some of the 

 encrustations, ejecting much of the excess. 

 Foraging in this manner, the fish may cover an 

 area of no more than 4 to 5 m- until satiated. 

 Similar search patterns occur along the bottom or 

 in close proximity to rocks, logs, and other struc- 

 tures. 



When feeding on M. edulis, which comprise a 

 significant part of their diet during part of the 

 year (Table 3), the fish grasp and ingest with the 

 anterior canine teeth, then crush the shell with 

 their pharyngeal teeth in much the same manner 

 as described for tautog (011a et al. 1974). 



Food Habits 



Our analysis of digestive tract contents showed 

 that cunner forage on a variety of organisms (Ta- 

 ble 3), mainly invertebrates, as has been reported 

 previously (Richards 1963; Chao 1973). While 

 Richards found amphipods to be the most impor- 

 tant food item for cunner in Long Island Sound 

 and Chao reported mussels (both Mijtilus edvlis 

 and Modiolus modiolus) to occur most frequenty in 

 gut contents of fish collected at Nahant, Mass., our 

 analysis for the sizes studied showed two major 

 food items, Mi/filus edulis and Idofea haltica, 

 comprising 24.8% and 44.8%, respectively, of all 

 food consumed. Our data showed a significant 

 seasonal shift in the utilization of these two major 

 forage species. During the May-June period, M. 

 edulis predominated with 57.1% with only 0.5% /. 

 haltica present. During July-August, the foraging 

 pattern changed with /. haltica then being the 

 major component of the diet at 72.1% and only 4.3% 

 M. edulis present. This trend continued into the 

 September-October period with 61.7% and 13.0% 

 for /. haltica and M. edulis, respectively. 



Examination of the digestive tract contents 

 from young tautog (105-260 mm) showed that they 

 were feeding predominantly on M. edulis 

 throughout the feeding season (Table 3). Other 

 items present occurred in varying and sig- 

 nificantly lesser amounts. 011a et al. (1974) report- 

 ed the same pattern in feeding for larger tautog. 



DISCUSSION 



Cunner and tautog, the only labrid inhabitants 

 898 



of north temperate waters of the western Atlan- 

 tic, are often found co-residing on "reef" habitats 

 south of Cape Cod. The geographical area in which 

 these animals are found is beyond the northern 

 limit for hermatypic corals. Hence, the "reef" 

 habitat, as we define it, includes any natural or 

 artificial structure or relief which provides a habi- 

 tat for various species dependent, to some degree, 

 on shelter sites (Smith and Tyler 1972), e.g., cracks 

 and crevices, and also serves as a substrate for a 

 variety of attached fauna and flora utilized as food 

 items for resident fish. 



Both cunner and tautog are active during the 

 day and inactive at night. The inactive phase of 

 nighttime is characterized by complete quiescence 

 or sleep, a typical trait for labrid species in general 

 (for examples see Hobson 1965, 1968, 1972; Starck 

 and Davis 1966; Tauber and Weitzman 1969; 

 Collette and Talbot 1972). 



As was discussed in an earlier paper (011a et al. 

 1974), the low level of responsiveness which is 

 characteristic of the sleep phase of labrids and 

 species of similar habit indicates that there is a 

 reduction in the potential to avoid or escape en- 

 vironmental stress that may be imposed during 

 the night. 



Both of these species require shelter sites as 

 resting places during the night sleep phase. 

 Cunner of all sizes and tautog of less than 250 mm 

 also appear to require a close association with ob- 

 jects affording shelter by day and during the 

 winter, when they remain in a torpid condition. It 

 is, therefore, obvious that the "reef" habitat, as a 

 provider of shelter sites, would be a limiting factor 

 in the population size of these two species. Any 

 interspecific competition for shelter sites encoun- 

 tered by the cunner would probably be limited to 

 tautog less than 250 mm, with both species 

 requiring shelters of similar type and size. The 

 amount of available shelter for coral reef species is 

 an obvious limiting factor of population size (Sale 

 1972; Smith and Tyler 1972. 1973). 



An attempt to attract or to increase populations 

 of shelter-dependent species has been the 

 development of man-made reefs using a variety of 

 substances including automobile tires and bodies, 

 construction rubble, sunken barges or ships, etc. 

 (see Rickards 1973; Steimle and Stone 1973). The 

 construction of man-made reefs would be most 

 successful in areas in which sufficient food 

 resources are available for the fish to be attracted 

 or where the potentiality for food accretion would 

 be increased by the addition of an appropriate 



