Diel movements of juvenile plaice Pleuronectes platessa in relation to predators, competitors, food availability and abiotic factors on a microtidal nursery ground

Abstract

The distribution and movements of juvenile plaice Pleuronectes platessa and their potential predators and competitors were recorded in a small microtidal (-20 cm) bay on the west coast of Sweden uslng underwater television and conventional nettlng techniques. There was generally close correspondence between the results obtalned by the 2 methods. Young plaice moved upshore at dusk and returned to deeper water at dawn. Larger predatory fishes also moved upshore at night but not as far as the plaice; they also entered shallow water later and left for deeper water earlier than the plaice. One interpretation of these nocturnal upshore migrations by plalce, therefore, is that they minimse predation risk. Although stomach fullness was greater at night, the availability of suitable food items for the plaice throughout the bay makes it unl~kely that the upshore movements were solely related to feeding. Because there was a strong diel temperature fluctuation In the bay, such movements also ensured that the fish remained in a fairly constant temperature. The main competitor of the plaice for food in July, the shrimp Crangon crangon, showed no such migratory movements and was mostly active during the day. The other dominant large crustacean (Carcinus maenas) was nocturnally active and did not markedly change its depth distribution over the 24 h period. The observed patterns of movement suggest that the timing of immigration and emgration is mainly triggered by changes in light intens~ty because only in C. rnaenas was any relationship found between activity and the phase of the tidal cycle.

Distribution, movements and diet of macrocrustaceans on a Scottish sandy beach with particular reference to predation on juvenile fishes

“…Crangon crangon and Carcinus maenas have both been shown experimentally to be more active nocturnally (Naylor 1958, Kitching et al 1959, Hagerman 1970, Dyer & Uglow 1978, van Donk & de Wilde 1981, and, in underwater television observations in the same area as this study, both species were seen more at night than during the daylight (Burrows et al 1994). In contrast, on a microtidal beach in Sweden, C. crangon were mostly active during the day while C. maenas were nocturnally active, with neither species showing migration (Gibson et al 1998). Abello et al (1991) found that Liocarcinus depurator were most active at night, but, contrary to the present observations, L. holsatus were most active during the day.…”

Ontogenetic changes in depth distribution of juvenile flatfishes in relation to predation risk and temperature on a shallow-water nursery ground

“…Shore crabs are most abundant at depths of > 2 m during the day, although they are shallower and more abundant at night (Ansell et al 1999). Overlap between this predator and the smallest plaice is therefore low, and any diel changes in the distribution of crabs is matched by those of the plaice (Burrows et al 1994, Gibson et al 1998.…”

Temporal partitioning of diurnal behavioural patterns of Coris julis and Diplodus vulgaris (Actinopterygii: Perciformes) in Mediterranean coralligenous habitats

“…Indeed, crepuscular periods represent a less favourable period for diurnal individuals, whose vision is not adapted to dim light conditions. This especially concerns young and smallsized individuals, which are exposed to a greater predation pressure than older and bigger fi sh (Helfman 1981, Gibson et al 1998). An increased activity of larger and older individuals later in the evening compared to smaller fi sh could also be related to a diet shift, as observed in lakes (Helfman 1981).…”