Long-term assessment of settlement and growth of juvenile winter flounder (Pseudopleuronectes americanus) in New Jersey estuaries

We examined patterns of metamorphosis, settlement, and growth for young-of- the-year winter flounder over a ten year period (1990-1999) in four estuari es spanning the coast of New Jersey, USA, with the objective to determine t he spatial and temporal coherence in these processes. We hypothesised that these processes could be influenced by large-scale climatic factors such as temperature and small-scale, local factors such as predator and prey abund ances and differences associated with the localised population structure of winter flounder. Newly settled juveniles were collected in late May/early June each year. Increment counts on sagittal otoliths were used to determin e the date of metamorphosis, and increment widths were used to estimate gro wth rates at two times, just after settlement and just prior to capture. A high level of consistency in spatial patterns among four individual estuari es was evident, and was largely driven by the northernmost site, Sandy Hook , which had higher fish densities and later metamorphosis than the three ot her sites, and faster growth rates than the two mid-coast sites (Barnegat B ay and Great Bay). In contrast to spatial patterns, consistent temporal pat terns were evident only in the timing of metamorphosis, which was delayed i n colder years at all sites. Weekly plankton sampling over the same ten yea r period at one site (Great Bay) yielded winter flounder larvae during a re latively narrow period in spring, with a later peak of abundance in colder years, in agreement with back-calculated dates of metamorphosis for settled juveniles. These patterns suggest that the timing of settlement is driven by large-scale climatic factors that influence the timing of spawning and/o r larval development. Interannual variability in densities and growth rates , however, appeared to be independent at each site, indicating control by l ocal environmental factors or genetic differences among local populations. The spatial consistency of growth rates suggests that appropriate nursery a reas can be readily identified for juvenile winter flounder. However, subse quent recruitment needs to be verified at the level of local populations to identify contributing source habitats. (C) 2001 Elsevier Science B.V. All rights reserved.