Decline in growth rate of juvenile European plaice (Pleuronectes platessa) during summer at nursery beaches along the west coast of Scotland

Abstract

This study concludes that declines in growth rates of young-of-the-year European plaice (Pleuronectes platessa) (YOY plaice) during summer vary spatially and between years and that these dynamics are not driven by temperature, body size, or competition. RNA-predicted growth rates of YOY plaice on the west coast of Scotland declined linearly between mid-July and mid-September, with faster declines at beaches and in years where growth rates were initially high. Absolute growth estimates rarely approached ad libitum laboratory rates, and relative declines in growth rates were unrelated to temperature or body size allometry, indicating that maximum growth was rare. However, the absence of inverse relationships between spatial or temporal growth variation and YOY plaice or brown shrimp (Crangon crangon) densities suggests that competition did not limit growth. There were no consistent trends in morphometric condition factor, biochemical composition, or energy content during summer, indicating that apparent growth declines did not result from energy storage and did not result in depletion of energy stores. Influences of extrinsic factors (such as prey conditions, physical disturbance, and predator densities) on the diet, mediated by behavioral decisions to optimize growth with other ecological constraints, require further investigation as causes of growth variation in YOY plaice.