Spatial variation in growth rate of early juvenile European plaice Pleuronectes platessa

Abstract

Patterns and causes of spatial variation in RNA-predicted growth rates in mid-August were examined in young-of-the-year European plaice Pleuronectes platessa (‘YOY plaice’) at 22 beaches along a 300 km stretch of coastline in west Scotland in 3 consecutive years. According to restricted maximum likelihood models, growth rates varied among beaches (25 km scale), but these spatial patterns were not consistent across years. We found no evidence for spatial variation in growth at the scale of subregions (50 km) or regions (100 km). Growth rate was positively correlated with total length, both within and among beaches and years. In general, YOY plaice in mid-August grew more slowly than estimated ad libitum laboratory rates. Average growth rates by beach and year were inversely related to intraspecific competitor densities, but not interspecific competitor densities (brown shrimp Crangon crangon) or 2 environmental productivity metrics (nearshore chlorophyll a concentration and lugworm Arenicola marina cast density). Physical beach characteristics also explained a significant source of spatial growth variation, with fish growing faster at beaches with larger tidal range and wave fetch. Therefore, the hypothesis of sub-maximum growth due to intraspecific competition (density-dependent growth) was supported, but additional, previously unexplored processes related to physical beach characteristics appear to have important influences on the spatial growth dynamics of YOY plaice.