Diversity, Abundance, and Spatial 

 Distribution of Fishes and Crustaceans 

 in the Rocl<y Subtidal Zone of 

 the Gulf of Maine* 



F. Patricio Ojeda 



Department of Zoology, University of Maine, Orono, Maine 04469 

 Present address: Departamento de Ecologfa, Facultad de Ciencias Bioldgicas 

 Pontificia Universidad Catdlica de Chiile. Casilla 1 14-D, Santiago. Chile 



John H. Dearborn 



Department of Zoology, University of Maine 

 Orono. Maine 04469 



Shallow subtidal habitats of the Gulf 

 of Maine harbor important popula- 

 tions of decapod crustaceans and a 

 variety of fish species (Bigelow and 

 Schroeder 1953, Cooper et al. 1975, 

 Hacunda 1981). Because of the eco- 

 nomic importance of lobsters, con- 

 siderable work has been done on the 

 biology and autecology of this spe- 

 cies along the northwest Atlantic 

 coast (see, for example, Campbell 

 and Stasko 1986, and papers cited 

 therein). Additional attention has 

 been given to the study of lobster 

 ecology since Mann and co-workers 

 suggested in the 1970s that lobsters 

 were "keystone predators" (sensu 

 Paine 1969) in these systems (Mann 

 and Breen 1972, Breen and Mann 

 1976, but see Miller 1985). There 

 are relatively few published studies 

 dealing with other common preda- 

 tors, such as fish and crabs, inhabit- 

 ing shallow subtidal habitats of the 

 coast of Maine. With few exceptions, 

 most studies on fishes have dealt 

 primarily with aspects of feeding 

 and reproductive biology of single 

 species (e.g., cunners: Chao 1973, 

 011a et al. 1975; sculpins: Moore and 

 Moore 1974; wolffish and cod: Keats 



•Contribution of the Department of Zoology, 

 Migratory Fish Research Institute, and Ira 

 C. Darling Center of the University of 

 Maine. 



et al. 1986, 1987). Long-term tem- 

 poral and spatial changes of demer- 

 sal fish assemblages along this coast 

 have been analyzed by Tyler (1971) 

 and Hacunda (1981), and more re- 

 cently, MacDonald et al. (1984) have 

 studied temporal variation of in- 

 shore fish assemblages in Passama- 

 quoddy Bay, Canada. To date, how- 

 ever, mobile predator assemblages 

 (including fish and crustacean spe- 

 cies) have not been comprehensive- 

 ly studied along the coast of the 

 Gulf of Maine. 



Our study first describes the com- 

 position of large mobile predators, 

 particularly decapod crustaceans 

 and fishes, occurring in rocky sub- 

 tidal habitats at Pemaquid Point, 

 Maine, and secondly examines their 

 distribution, diversity, and abun- 

 dance patterns on spatial (bathy- 

 metric) and temporal scales. The in- 

 formation gathered in this study is 

 then analyzed in terms of seasonal 

 impacts of those species in shallow 

 rocky shores and the importance of 

 these environments as nursery areas 

 for these species. 



Materials and methods 



The study site was a rocky, shallow, 

 sublittoral area off the southwest 

 side of Pemaquid Point, Maine 

 (43°50'N; 69°31'W). This is a wave- 



exposed area. The substrate down 

 to ~10-12 m (below Mean Low 

 Water Level, MLWL) consists of a 

 sloping, relatively flat ledge. Large 

 rocks and boulders characterize the 

 bottom between ~12-20 m depth. 

 At depths greater than 20 m the 

 substrate is primarily sand with 

 occasional boulders. A detailed de- 

 scription of this study area, in- 

 cluding zonation patterns of benthic 

 organisms, is given in Ojeda and 

 Dearborn (1989). 



Two methods were used to sam- 

 ple the mobile fauna of this region: 

 gillnets and underwater observa- 

 tions. To determine diversity and 

 abundance of fish species, two 3 x 

 40 m experimental gillnets con- 

 sisting of four panels (graded in 

 mesh size from 10-20 mm to 60-70 

 mm) were randomly set in parallel 

 on the bottom, perpendicular to the 

 shore at depths between 5 and 23 

 m, and about 300 m apart. 



Fish were sampled monthly for 2 

 to 3 days from June 1985 to October 

 1986, except in July, October, and 

 December of 1985, and January 

 1986. Gillnets were usually set with- 

 in the first hour after sunrise and 

 retrived an hour before sunset. All 

 captured fish were fixed in a 5-10% 

 solution of buffered (borax) formalin- 

 seawater mixture, placed in labeled 

 plastic bags, and transported to the 

 laboratory for further analysis. Pre- 

 served fish were identified, counted, 

 measured (total length = TL) to the 

 nearest 1.0 mm, and wet weighed 

 to the nearest 1.0 g on a Mettler 

 P1200 balance. 



Temporal changes in fish abun- 

 dance were determined by using a 

 catch-per-unit-effort (CPUE) mea- 

 surement. This index was calculated 

 as the total number of fish captured 



Reference to trade names does not imply en- 

 dorsement by the National Marine Fisheries 

 Service. NOAA. 



Manuscript accepted 20 December 1989. 

 Fishery Bulletin, U.S. 88:403-410. 



403 



