Foraging time strategy of small juvenile plaice: a laboratory study of diel and tidal behaviour patterns with Artemia prey and shrimp predators

Abstract

The natural pattern over time of foraging and migration in juvenile plaice Pleuronectes platessa has evolved to enhance the survival of the fish. It is a product of endogenous rhythms and direct responses to biological and physical conditions, including their predators and prey. This study aimed to determine the relative roles of these influences through experimental manipulation of the physical and biological conditions. Infrared television cameras and illumination were used to observe freshly caught juvenile plaice in the light and dark over 24 h periods in arena tanks. Single Crangon crangon and Arternia nauplii were added to these tanks as predators and food respectively. The behaviour of juvenile plaice in the light was dominated by swimming on the sand surface, with little activity on the bottom during darkness. Most swimming on the bottom occurred 0 to 2 h after the expected tlme of high water. Activity in darkness largely comprised swimming In the water column or at the surface, with most swimming seen 2 to 4 h after high water. Off-bottom swlmming was also seen at this time in the light. Arlemia as prey reduced swimming on the bottom during the light period, but had no effect on off-bottom activity. The presence of single C. crangon in the tank had no discernible effect on behaviour. Different functions are proposed for pelagic and benthic swimming. Both may be used for migration while pelagic swimming may avoid predators on the bottom at night. Benthic swimming may be used for foraging.

Increased turning per unit distance as an area-restricted search mechanism in a pause-travel predator, juvenile plaice, foraging for buried bivalves

“…The plaice did not home in on patches of D. vittatus from a distance and intensive search behaviour always began in or near a patch, suggesting a localized cue. Juvenile plaice forage mainly in daylight (Edwards & Steele, 1968;de Groot, 1971;Lockwood, 1980) and detect their prey by sight (Blaxter, 1968;de Groot, 1971;Burrows, 1994 bivalves in the dark (Blaxter, 1968;Burrows et al, 1994), possibly detecting the respiratory currents generated by these prey (de Groot, 1971). However, it is not known whether the cue triggering intensive search was visual, tactile or chemical.…”

Increased turning per unit distance as an area‐restricted search mechanism in a pause‐travel predator, juvenile plaice, foraging for buried bivalves

“…The plaice did not home in on patches of D. vittatus from a distance and intensive search behaviour always began in or near a patch, suggesting a localized cue. Juvenile plaice forage mainly in daylight (Edwards & Steele, 1968;de Groot, 1971;Lockwood, 1980) and detect their prey by sight (Blaxter, 1968;de Groot, 1971;Burrows, 1994). They also attack buried T II.…”

“…Plaice foraging movements are mainly close to the substratum and effectively two dimensional (Gibson, 1980;Holmes & Gibson, 1983;Burrows, 1994;Burrows et al, 1994). Short moves are separated by stationary pauses, which last from a fraction of a second to several minutes (Gibson, 1980), allowing easy identification and measurement of individual movements.…”

“…Short moves are separated by stationary pauses, which last from a fraction of a second to several minutes (Gibson, 1980), allowing easy identification and measurement of individual movements. Juvenile plaice are thought to detect their prey primarily by sight (Blaxter, 1968;de Groot, 1971;Burrows, 1994) but they never initiate attacks on D. vittatus from distances >1 cm (Ansell, 1995), suggesting that less conspicuous prey are detected only at short range.…”

Effect of fisher’s soak tactic on catch pattern in the Danish gillnet plaice fishery

“…Regarding length dependency, there was an indication of a higher probability for smaller individuals to be caught at day than at night. Indeed, it was observed in a laboratory study that the behavior of juvenile plaice in the light was dominated by swimming on the sand surface, with little activity on the bottom during darkness (Burrows, 1994). .…”