Relation of Prey Availability to Habitat Selection for Red Drum in Bayou St. John, An Urban Waterway in New Orleans, Louisiana

Red drum (Sciaenops ocellatus) are an important game fish for Louisiana.  In an effort to help restore the fishery in Bayou St. John (BSJ), red drum habitat use and its relation to potential prey items in BSJ were analyzed from August to December 2010.  During this same time period, the movement of seven red drum fitted with internal acoustic telemetry transmitters was documented by receivers moored at three sites along BSJ (north, central, and south sites).  These data were utilized to determine habitat selection.  Three gear types were used to assess prey availability: minnow traps, seines, and PONAR dredges.  Minnow traps were used to assess benthic epifauna while seines were used to sample nearshore fish assemblages.  Both gear types were fished at each site monthly with three replicates taken per site.  A PONAR dredge was used to sample benthic fauna at each site on 10 December 2010.  Remote sensing data indicated that red drum were not randomly distributed in BSJ (Chi-square, randomization p < 0.001).  The average number of monthly receiver detections at the three sites was found to decrease southward:  north site = 8346, sd = 2908; central site = 2899, sd = 1858; south site = 44, sd = 48.  The two most abundant organisms sampled using minnow traps were Harris mud crab (Rhithropanopeus harrisii) and bluegill (Lepomis macrochirus).  The abundance of R. harrisii was found to be significantly different from a random distribution, with average abundances being highest at the most north site and lowest at the south site (Chi–square = 11.315, p = 0.003).  The abundance of L. macrochirus among sites was not significantly different from a random distribution (Chi–square = 2.178, p = 0.337).  While significant differences in nearshore fish assemblages were detected, the low Global R values suggests these differences may not be ecologically pertinent (ANOSIM, R= 0.157, p= 0.002).  Preliminary PONAR dredge data also suggest a higher abundance of organisms collected at the northern site.  These results suggest that red drum are choosing different habitats within BSJ (e.g., northern sites) and that habitat selection may be related to benthic macroinvertebrate abundances.  It also appears that fishes as potential prey play less of a role in determining red drum habitat selection in BSJ.