2005. Small-scale spatio-temporal variability in ichthyoplankton and zooplankton distribution in relation to a tidal-mixing front in the Irish Sea. e ICES Journal of Marine Science, 62: 1021e1036.This study examines the spatio-temporal dynamics of fish larvae and their prey at a tidalmixing front in the central Irish Sea. The distribution of ichthyoplankton and zooplankton was analysed in relation to environmental variables (depth, surface temperature, surface salinity, and water column stratification) using Redundancy Analysis (RDA). Significant interannual variability in the formation and position of the tidal-mixing front coincided with large differences in the species abundances of both ichthyoplankton and zooplankton. During the summer, ichthyoplankton and zooplankton communities were structured by a combination of depth and hydrography, and the variability in species composition was directly related to the average value of the stratification parameter. Several ichthyoplankton species were consistently associated with frontal waters, while fewer species were concentrated in mixed water masses throughout the sampling period. The distribution of individual zooplankton species was also examined, and water mass affinities were shown to vary with developmental stage.

The small-scale variability in condition and growth of dab Limanda limanda larvae was investigated in relation to a tidal-mixing front (Manx West Coast front) off the west coast of the Isle of Man, Irish Sea. RNA:DNA ratios and otolith microincrement analysis were used to estimate nutritional status and recent growth rates of larvae captured on 5 May 1999 in mixed, frontal and stratified waters associated with this front. RNA:DNA ratios were significantly higher at the Manx West Coast front compared to mixed waters, although recent growth rates did not vary significantly with water column stability. More favourable feeding conditions associated with frontal waters from previously reported large-scale investigations in the Irish Sea were reflected on a smaller spatial scale. Although frontal accumulation of dab larvae was not observed in the current study, dab larvae found in the stratified and frontal waters were significantly larger than those captured in the mixed waters. This pattern could suggest an offshore movement of dab larvae into more favourable waters as they develop.