408 



Fishery Bulletin 88(2). 1990 



(one-way ANOVA, F<0.01; a posteriori SNK test; Fig. 

 3D). In contrast to adult cunners, juvenile cunners (<5 

 cm) comprised more than 90% of the total cunners 

 sighted in the first three depth stations (i.e., 2-8 m 

 depth) along the transects. 



The number of shelters (a measure of substrate 

 heterogeneity) significantly increased with depth (one- 

 way ANOVA, P<0.01; Fig. 3E). This increment is due 

 to the increasing number of large rounded rocks ob- 

 served at the deeper (10-20 m) transects which create 

 large numbers of interstices (holes) suitable for pred- 

 ators' occurrence. 



Discussion 



A diverse assemblage of mobile predators inhabits the 

 shallow rocky subtidal zone at Pemaquid Point, Maine. 

 These subtidal habitats are utUized by these species for 

 multiple purposes such as nursery grounds, feeding 

 grounds, shelter, and reproductive activities (011a et al. 

 1975, MacDonald et al. 1984, Keats et al. 1987, Ojeda 

 1987). The occurrence and abundance patterns of these 

 species are, however, markedly seasonal and closely 

 follow the temperature regime typical of northwest 

 Atlantic waters. This suggests that temperature is one 

 of the major abiotic factors affecting the distribution 

 of these predator species on this coast, a finding in 

 agreement with other studies (Tyler 1971; Hacunda 

 1981; Ennis 1984b; MacDonald et al. 1984; Keats et al. 

 1986, 1987). 



Four temporally distinct components were recog- 

 nized in this predator assemblage: summer-fall resi- 

 dents, regular residents, summer periodicals, and 

 occasionals. Similarly, Tyler (1971) distinguished four 

 temporal groups in the demersal fish assemblage oc- 

 curring in Passamaquoddy Bay, New Brunswick, which 

 have also been recognized in other demersal ichthyo- 

 faunas of the Gulf of Maine (Hacunda 1981, MacDon- 

 ald et al. 1984). Three of the four categories of Tyler 

 (1971) were recognized in this study: "regulars," "sum- 

 mer periodicals," and "occasionals." No representa- 

 tives of Tyler's (1971) fourth category ("winter peri- 

 odicals"; i.e., species occurring only during winter) 

 were found in this study. This result, however, should 

 be taken cautiously because no samples were taken in 

 midwinter. The most conspicuous and abundant species 

 of mobile predators in this study were summer-fall 

 residents (e.g., cunners, pollock, lobsters, and sculpins), 

 which occurred for most of the warm period in shallow 

 rocky habitats. Summer-fall residents undergo small- 

 scale migrations, moving into deeper, warmer water 

 (>4°C) during winter and returning to shallow subtidal 

 areas in spring. These seasonal movements occur in 

 response to changes in water temperature and prob- 



ably to physical disturbances such as strong water 

 surges and storms along some e.xposed coasts. This 

 seasonal migratory behavior represents a behavioral 

 stratety to avoid freezing that involves no physiological 

 adjustment. An alternative strategy involves the elab- 

 oration of macromolecules which possess unique anti- 

 freeze properties (e.g., glycopeptides in sea raven and 

 winterflounder: Duman and De Vries 1974, Slaughter 

 et al. 1981). 



There are conflicting results in the literature concern- 

 ing winter migration and activity of cunners and lob- 

 sters. Several authors have shown that cunners and 

 lobsters do not migrate into deeper waters during 

 winter (Green and Farwell 1971, Cooper et al. 1975, 

 OUa et al. 1975, Dew 1976). However, investigations 

 have shown that cunners (Chao 1973) and lobsters (En- 

 nis 1984b) move to deeper waters in winter as sug- 

 gested in this study. Recently, Ennis (1984b) showed 

 that small-scale movements of lobsters in Newfound- 

 land were related to increased turbulance due to 

 storms. This is a likely explanation for the absence of 

 lobsters and cunners during winter at Pemaquid Point 

 in this study. As mentioned above, Pemaquid Point is 

 an exposed site (Ojeda 1987). During winter, this area 

 is severely affected by periodic storms and heavy water 

 motion that usually generate strong turbulence over 

 a wide depth range. For organisms that remain in dor- 

 mant states in shallow waters during winter (such as 

 cunners), water movements may severely restrict their 

 distribution. Most studies documenting the presence 

 of cunners in inshore habitats during winter have been 

 conducted in bays or in other protected areas away 

 from heavy water motion (e.g.. Green and Farwell 

 1971, Olla et al. 1975, Dew 1976). In contrast, docu- 

 mentation of offshore movements of cunners during 

 winter comes from studies conducted on exposed 

 coasts, such as that of Chao (1973). A similar situation 

 seems to occur in lobsters (Ennis 1984b) and probably 

 with crab species which strongly suggests that water 

 movement from turbulence and heavy surge is an im- 

 portant factor, in addition to water temperature, af- 

 fecting the temporal and spatial distribution of large 

 organisms in shallow subtidal environments of the Gulf 

 of Maine. 



Shallow rocky subtidal habitats along the northern 

 New England coast harbor a diverse community of 

 marine organisms providing abundant food resources 

 to seasonal fish residents, occasional migratory fish 

 species, and large crustacean predators (Ojeda 1987). 

 This is so despite the general paucity of kelp beds in 

 this coast, which are an important determinant of the 

 abundance and diversity of nearshore fish and large 

 decapod crustaceans on other temperate coasts (Quast 

 1968, Moreno and Jara 1984). In addition to acting as 

 feeding grounds, shallow rocky environments also 



