Rountree and Able Abundance, growth, and foraging habits of Mustelus cams 



529 



ference in the y-intercepts between sexes was ob- 

 served for weight (ANCOVA, P<0.001; Fig. 5), sug- 

 gesting that females may have been born slightly 

 heavier (approx. 42 g) than males. A highly signifi- 

 cant length-weight relationship was obtained (Fig. 

 6). No differences in the length-weight relationship 

 were found between sexes. 



Habitat use patterns 



Habitat type (tidal creek versus adjacent bay shoals), 

 time of night, and tide stage (ebb versus flood) had a 

 strong effect on CPUE of smooth dogfish in gill-net 

 collections (Figs. 4 and 7). Most smooth dogfish were 

 captured on flood tides (Fig. 4), with flood tide CPUE 

 averaging 1.1 fish/net h (SE=0.2>, and ebb tide CPUE 

 averaging 0.5 fish/net h (SE=0.1). Catches were 

 greatest at 2 100 h ( 3 fish/net h ) and declined sharply 

 by 0300 h (<0.6 fish/net h), and dropped to near zero 

 by 0600 h (Fig. 7). Catches tended to be greater in 

 the bay shoal habitat than at the creek sills (Fig. 4), 

 with CPUE averaging 1.2 fish/net h (SE=0.2) and 

 0.6 fish/net h (SE=0.1), respectively. Abundance of 

 YOY in weir samples varied significantly (P<0.5) 

 among Foxboro, Schooner, and New creeks, averag- 

 ing 3.7, 0.3, and 0.8 individuals/weir, respectively. 



Foraging habits 



Dominant prey of YOY smooth dogfish included the 

 shrimps Crangon septemspinosa and Palaemonetes 

 vulgaris, polychaetes, and the crabs Callinectes 

 sapidus, Libinia spp., and Ovalipes ocellatus (Table 

 3). The diet of YOY included several other small de- 

 capod crabs, razor clam (Ensis directus), and small 

 fishes (Menidia menidia and Fundulus heteroclitus). 

 Often, YOY dogfish stomachs contained the walking 

 legs or chelae of crabs, rather than entire individuals. 

 Soft shell individuals of the various crab species were 

 also frequently consumed. Whole crabs, other than 

 those recently molted, were rarely observed. 



There were no strong tidal or hourly trends in gut 

 fullness (Fig. 8). No empty stomachs were found. 

 Stomach fullness averaged 5.04 9c body wt(SE=0.21, 

 re=136), and 4.21 % body wt (SE=0.21, ra=107) for 

 individuals captured during flood and ebb tides, re- 

 spectively. Stomach fullness increased slightly from 

 early evening (averaging about 4 % body wt at 1900 

 h) to early morning ( averaging about 5 9c body wt at 

 0600 h). Three fish examined during mid-afternoon 

 also had high levels of food in their stomachs (4-6 % 

 body wt at 1200-1300 h). Intestine fullness remained 

 remarkably constant regardless of time of night 

 (hourly means ranging from 0.4-0.5% body wt, and 

 1.5-1.9 % body wt for the small and large intestine, 



Time ot net check 



Figure 7 



Hourly mean abundance (CPUE per hour per net) of smooth 

 dogfish collected during the night with gill nets set in marsh 

 creeks and adjacent bay habitats during 1990. Data are 

 grouped by ebb- and flood-tide stage. Vertical lines are ranges. 



respectively). We did not observe any strong decline 

 in stomach fullness or any increase in intestinal full- 

 ness that would suggest noncontinuous feeding. 



Discussion 



Life history stages and seasonal abundance 

 patterns 



Smooth dogfish are seasonal residents in New Jer- 

 sey estuaries; adults are present April-September, 



