Growth potential of juvenile southern flounder, Paralichthys lethostigma, in low salinity nursery areas of Pamlico sound, North Carolina, USA

Field growth experiments were conducted in cages during June–August 1993, to compare growth rates of juvenile southern flounder, Paralichthys lethostigma (standard length (SL) 37 to 70 mm), in historically utilized (two creeks) and underutilized (two creeks) low salinity nursery areas within the Pamlico River Estuary of Pamlico Sound, North Carolina. Growth rates from five sequential trials were used to estimate the nursery areas' productive capacities for juveniles of this species. Instantaneous daily growth rates, measured as a function of changes in weight, showed that southern flounder placed in underutilized creeks exhibited significantly higher mean instantaneous daily growth rates (3.94·10⁻²±0.47) than southern flounder placed in utilized creeks (1.66·10⁻²±0.49). Thus, other factors such as colonization rate must be limiting production in nursery areas. Temperature was positively correlated with growth rate and accounted for about 20% of the variability in growth rates. The approach used in this study provides an alternative method of assessing critical nursery habitats for juvenile flatfish in estuarine environments. Assessment of nursery value in terms of potential productive capacity rather than realized production should prevent underassessment of value due to low levels of colonization in some years.