WENNER: SPONGE-CORAL HABITAT FISHES 



Species Composition and 

 Relative Abundance 



Eleven trawl tows in the open-shelf habitat collected 

 470 individuals distributed among 26 species (16 

 families) with a total weight of 31.4 kg. Day catches 

 (11 species, 8 families) accounted for only 6% of the 

 number and 18% of the total weight of demersal 

 teleosts taken at this site, and were not dominated by 

 a single species. Night tows (22 species, 13 families) 

 were dominated by planehead filefish, Stephonolepis 

 hispidus, which accounted for 68% of the number and 

 46% of the weight of demersal teleosts at the open- 

 shelf site (Table 2). 



Trawl tows in the sponge-coral habitat (n = 57) 

 collected 22,046 demersal teleosts belonging to 102 

 species (37 families) and having a total weight of 

 1,832 kg (Table 3). The Sparidae dominated the 

 catches with the greatest number of species (9) and 

 accounted for 59% of the total number and 48% of 

 the total weight of demersal teleosts. The five most 

 numerically abundant families comprised 92% and 

 77% of the total catch by numbers and weight. The 10 

 most numerically abundant species accounted for 

 54% of the total abundance in all 57 trawl tows. 

 Catches of the southern porgy, Stenotomus aculea- 

 tus, were an order of magnitude higher than those of 

 other species (Table 4), contributing 57.3% of the to- 

 tal. This species also ranked first by weight, compris- 

 ing 42.1% of the trawl-caught fish weight (Table 5). 



Community Structure 



One's perception offish community structure in the 

 South Atlantic Bight depends upon the habitat and 

 time of sampling. Numerical classification indicated 

 that four major divisions were present, consisting of 

 12 site groups (Fig. 4). The first major division con- 

 tained, with one exception, otter trawl collections 

 made during the day (site group 1) and night (site 

 group 2) in the open-shelf area. A second division 

 within the classificatory scheme included all trawl 

 tows from reef 5 (site group 3). The two remaining 

 broad divisions were composed of day tows (site 

 groups 4 through 7) and night tows (site groups 8 

 through 12) from the five remaining reef sites. In 

 general, major faunal distinctions were made, not only 

 between collections from different habitats (open 

 shelf vs. reef), but also between day and night samples 

 taken at the same site. 



The groundfish communities of the open-shelf and 

 sponge-coral habitat formed 9 species groups con- 

 taining from 5 to 1 1 species (Fig. 5). Each group was 

 associated with specific spatial and temporal con- 

 ditions. The five species of demersal fishes in group 

 A showed a high frequency of occurrence and abun- 

 dance at all reef sites, as reflected in the moderate to 

 very high nodal constancy values (Fig. 6). The low 

 and moderate constancy values for this species group 

 in site groups 1 (5 open-shelf day tows, 1 day tow at 

 reef 2) and 2 (6 open-shelf night tows) are a result of 



TABLE 2. — Demersal teleosts taken in 3 'i Yankee trawl tows at the open-shelf study site, 

 South Atlantic Bight, spring 1978. n = number of occurrences in 5 day or 6 night otter 

 trawl tows. 



541 



