Relating Environmental Fluctuation and the Early Growth of Estuarine Fishes: Ontogenetic Standardization

Abstract

Variability in early growth rates of estuarine-dependent juvenile fishes in relation to large-scale meteorological forcing may be detected following the removal of ontogenetic growth trends. Here we develop a general approach for the ontogenetic standardization of otolith daily records and demonstrate the usefulness of this approach in terms of relating the early growth of juvenile Atlantic croaker Micropogonias undulatus to concurrent environmental fluctuation. For these data, a linear/constant ontogenetic growth function provided the best fit to the inferred growth histories of individual fish. Whereas daily proportional growth declined linearly during the presettlement period, constant proportional growth ensued during the postsettlement phase of the first 50 d of early life. The recognition of such stage-specific shifts in growth trajectories is essential for accurate ontogenetic standardization. Daily postsettlement growth could be ontogenetically standardized for individual Atlantic croaker by reference to postsettlement growth constants. When averaged for individual fish, standardized daily growth was coherent with meteorological forcing at two widely spaced sites, as was shown by cross-correlations among standardized growth, salinity, and water temperature.