Movements and food habits of striped bass (Morone saxatilis) in Delaware Bay (USA) salt marshes: comparison of a restored and a reference marsh

There has been much recent interest in restoration of salt-marsh habitats t o their natural structure and function. However, the criteria for success o f such restorations are not well-defined. As part of a larger program to ev aluate the restoration of a former salt-hay farm bordering Delaware Bay, Ne w Jersey, USA, we monitored the response of a large predator, the striped b ass Morone saxatilis, to the restoration. During June to October 1998 we co mpared tidal and diel movements and food habits of juvenile and adult strip ed bass (n = 82, 212 to 670 mm fork length) between a restored marsh and an adjacent reference marsh with similar physical characteristics (depth, sal inity, temperature). Striped bass movements at both sites were characterize d by ultrasonic tracking with small, surgically implanted tags (21 d rated battery-life). Striped bass (n = 23, 421 to 610 mm fork length) were tagged and released near the main creek mouths at both the restored in = 14) and reference (n = 9) marshes. At both sites, striped bass tended to move up th e main creek during ebb tide. At the restored site, ebb tide upstream-movem ents ranged from 0.1 to 3.5 km from the main creek mouth(mean = 1.2 km). Du ring the upstream movement, the fish typically stopped every 200 to 300 m ( presumably to feed) for 1 to 2 h. At the reference site, few of the tagged fish moved farther than 100 to 200 m upstream from the main channel mouth a t ebb tide, perhaps in response to somewhat lower dissolved oxygen at this site. During flood tide, tagged fish at both sites moved out into Delaware Bay, where they remained within 200 to 500 m of the creek mouth. Striped ba ss were sampled with gill nets to determine additional aspects of habitat u se and food habits. Striped bass in both marshes were much more abundant at creek mouths (catch per unit effort, CPUE = 1.17) than in the upper reache s of the creeks (CPUE = 0.13). In the creek mouths, CPUE was greater at the restored site (CPUE = 1.8) than at the reference site (CPUE = 0.5). At bot h sites, most fish (approx. 80%) were collected on the late ebb or early fl ood tides, i.e. around low tide, when prey were presumably concentrated at the creek mouths. Stomach contents of bass from both restored and reference marshes (n = 59, 212 to 670 mm fork length) revealed that striped bass wer e eating mostly blue crab (Callinectes sapidus), grass shrimp (Palaemonetes vulgaris), sand shrimp (Crangon septemspinosa), mummichog (Fundulus hetero clitus), and various unidentifiable fishes (probably anchovies, Anchoa mitc hilli, and Atlantic silverside Menidia menidia). In conclusion, the restore d marsh supported larger numbers of striped bass than the reference marsh, but there was little difference in the pattern of creek utilization or food habits at either site. Thus, the restored marsh appears to be functioning in a similar manner to the reference marsh for these large predators.