Visual ecology of benthic and pelagic piscivores in coastal mid-Atlantic waters: Implications for predator-prey dynamics

Maintaining optimal visual performance is a difficult task in photodynamic coastal and estuarine waters because of the unavoidable tradeoffs between light sensitivity and temporal resolution, yet the visual systems of coastal piscivorous fishes remain understudied despite differences in ecomorphology and microhabitat use. We therefore used electroretinography to describe the spectral range, luminous sensitivity, dynamic range, and temporal resolution of the eyes of several benthic and pelagic piscivores common to coastal and estuarine waters of the western North Atlantic.  In general, most spectral ranges spanned 400-610 nm (with significant day-night differences in pelagic species) and differences in temporal resolution at maximum light intensities correlated with species-specific lifestyle and habitat. Benthic species exhibited higher light sensitivities and broader dynamic ranges than pelagic foragers. Pelagic species, however, showed larger day-night differences in both light sensitivity and temporal resolution than benthic species, consistent with diel foraging strategies in the former. Our results collectively demonstrate that pelagic piscivores are generally adapted to forage in bright photoclimates. We therefore suggest that recent anthropogenic degradation of water quality of coastal and estuarine environments may affect predator-prey dynamics (and therefore potentially restructure ecosystems) as eutrification and the associated increases in turbidity of coastal waters impede visually-foraging pelagic piscivores.