Experimental evidence of sediment preference by early life history stages of windowpane (Scophthalmus aquosus)

We evaluated sediment choice by young-of-the-year (YOY) windowpane, Scophthalmus aquosus, in the laboratory. We gave transitional (8–18 mm SL) and larger juvenile windowpane (32–89 mm SL) a choice of sediment mixtures, all of which were within the range observed in the field (tested range: sand–<1% silt/clay; mud–40-45% silt/clay). Observations (n=1619 in four 48-h trials) were of three kinds: location, burial behaviour, and pigmentation pattern (transitional or juvenile pigmentation). We also tested the effects of food availability and light level on sediment preference. Windowpane of all sizes preferred sand over mud in 65–84% of all observations, but there were differences in sediment preference, burial behaviour, and pigmentation pattern between the transitional and juvenile stages. Transitional windowpane were observed on sand less frequently, buried less often, and exhibited larval pigmentation more often than juveniles. Further analyses showed that transitional fish had a higher probability of moving from the preferred sediment (sand) during hours of darkness, and both stages had a higher probability of moving onto mud when food was absent. Juveniles were also more active when food was absent, but to a lesser extent than transitional fish. We believe that habitat selection may play a crucial role in determining the distribution of YOY windowpane under natural conditions and will aid in our interpretation of post-settlement distribution patterns of field populations in near-shore and estuarine environments in the Middle Atlantic Bight, USA.