Does salinity affect somatic growth in early juvenile Atlantic croaker, Micropogonias undulatus (L.)?

Factors affecting recruitment of fishes remain one of the most studied but least understood issues of fisheries science. Understanding the causes of r ecruitment variability remains elusive because factors that affect the grow th and survivorship of young fishes are complex and dynamic. Here we focus on the influence of salinity on growth of early juvenile Atlantic croaker, Micropogonias undulatus under laboratory conditions as part of a larger stu dy to relate short-term fluctuations in growth rates of young estuarine-dep endent fishes with variability in abiotic environmental factors. Body growt h of juvenile Atlantic croaker was significantly (P < 0.001) different amon g all of the three salinity treatments with growth in 5 parts per thousand > 20-5 parts per thousand = 20 parts per thousand. A Linear response to the changing treatment suggests an additive effect of changing salinity on bod y wet weight (WW) growth. Juvenile Atlantic croaker in the 5 parts per thou sand treatment grew in WW by a factor of 3.88 relative to initial WW. Fish in the 20-5 parts per thousand treatment grew in WW by a factor of 2.90, wh ile fish in the 20 parts per thousand treatment grew in WW by a factor of 2 .17. Otolith diameter also varied significantly with salinity, and there wa s a significant positive relationship between changes in body WW and change s in otolith diameter growth (r = 0.68, P < 0.02, n = 12). The correlation between body and otolith growth justified our use of otolith data to infer that substantial fluctuation in the early growth of early juvenile Atlantic croaker from field collections was inversely cross-correlated with salinit y and water temperature. Assuming that the probability of survival during t he nursery period increases as postlarval fish grow, salinity-induced plast icity in growth rates implies that the site and habitat into which post-lar val fish settle can potentially influence recruitment dynamics. This study demonstrates that there is the potential for fluctuations and spatial varia bility in salinity to cause significant variability in short-term growth ra tes for juvenile fishes within estuarine nursery areas. (C) 1999 Elsevier S cience B.V. All rights reserved.