Utilization of subtropical seagrass meadows by newly settled red drum Sciaenops ocellatus: patterns of distribution and growth
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abstract
Spatial and temporal variability in distribution and growth of newly settled red drum Sciaenops ocellatus were examined in the Aransas Estuary, Texas, USA. Overall, 1891 red drum larvae and early juveniles (4 to 30 mm standard length, SL) were identified from weekly epibenthic sled collections taken during the annual recruitment period (September-December 1994). Densities ranged from 0.0 to 3.4 ind. m-2, with peak values observed in mid to late October. Density varied significantly between habitats (Halodule wrightii vs Thalassia testudinum) and among sites. Otolith-based techniques were used to determine hatch-date distributions and individual growth rates of newly settled red drum. Hatch dates of individually aged red drum (n = 324) ranged from September 4 to October 30 (57 d). Hatch dates were used to separate individuals into 10-d cohorts and cohort-specific growth rates were estimated from exponential size-at-age plots. Cohort-specific instantaneous growth coefficients (g) ranged from 0.041 to 0.058 d-1 with highest values occurring for mid-season cohorts. Spatial and temporal patterns of recent growth (mean increment width over 5 d) were also investigated. Recent growth rates were highest for mid-season cohorts and relatively uniform between habitats and among sites. Since spatial trends in density were not explained by growth differences, we hypothesize that factors other than growth potential were influencing the distribution of newly settled red drum in the Aransas Estuary.
