MEPS 328:267-273 (2006)  -  doi:10.3354/meps328267

ABSTRACT: Pleuronectid flatfish are generally thought to utilize stereotypical anti-predator behavior to reduce encounters with potential predators. In this study, we tested the relative vulnerability of 3 juvenile (Age-0) flatfish species to predation under controlled laboratory conditions. Predators consumed significantly more English sole Parophrys vetulus than either Pacific halibut Hippoglossus stenolepis or northern rock sole Lepidopsetta polyxystra in clear water (0 nephelometric turbidity units, NTU), suggesting differing anti-predator strategies and/or capabilities. In contrast to halibut and rock sole, which remained buried and inactive, English sole were often observed actively moving about. As a result, English sole were encountered more frequently by predators than the other 2 species, suggesting that they were more conspicuous to the predators. This was further evidenced by a higher frequency of stalk encounters for English sole, whereby the predators detected and approached them prior to prey flushing. However, as an estuarine-dependent species, English sole are generally exposed to lower densities of predators in an environment that tends to be highly turbid. When similar trials were conducted at higher turbidity (18 NTU), predation rates on English sole decreased to rates comparable to that for halibut and rock sole in clear water (0 NTU). Although English sole appeared more vulnerable to predation, their behavior may have evolved in response to, and be mitigated by, the turbid nature of the estuarine nursery environments to which they recruit, where predation pressure is significantly reduced in comparison to open coastal habitats.

KEY WORDS: Anti-predator behavior · Predator–prey interactions · Juvenile flatfish · Estuarine dependence · Turbidity