1. Introduction
Irrespective of the feeding mode adopted in adult life, most early life history stages of fish are selective predatory planktivores. This involves sensory detection of individual
Ž prey by the predator, prior to initiation of the predator strike Arnold and Holford, 1990;
. Browman and O’Brien, 1992; Miller et al., 1993 . Most first-feeding fish larvae are
Ž .
dependent upon vision for prey detection Blaxter, 1986 , although non-visual senses Ž
have also been implicated in prey detection by selective planktivorous fish larvae Batty .
and Hoyt, 1995; Salgado and Hoyt, 1996 . This is in contrast to the non-selective particulate mode of feeding displayed by juveniles and adults of some fish species, in
which gill rakers are used to filter prey from the environment without prior discrimina- Ž
. tion of individual prey Janssen, 1980; Gibson and Ezzi, 1985; Batty et al., 1986 .
Selective planktivory and non-selective particulate feeding are both active feeding behaviours and are not to be confused with passive prey engulfment, which may occur at
low rates, especially in marine species that must drink seawater for osmotic control Ž
. Tytler and Blaxter, 1988 .
The success of prey capture by planktivorous fish larvae depends upon larval age, size, and motor and physiological competence, all of which increase during ontogeny
Ž .
Blaxter, 1986 . Detection of a prey organism does not always result in a predator strike, implying a prey selection process is involved. Studies that compare the prey spectra
available in the environment with prey ingested by fish larvae, confirm that prey Ž
characteristics besides size strongly affect patterns of prey selectivity Checkley, 1982; .
Ž .
Magnhagen, 1985; Govoni et al., 1986; Meng and Orsi, 1991 . Jenkins 1987 suggested that some fish larvae display innate prey preferences at an early age, whereas others
Ž .
suggest that learning plays an important role in prey selection Werner et al., 1981 ; such that fish positively select for and are more effective at capturing prey that are
Ž .
familiar Checkley, 1982; Meyer, 1986; Coughlin, 1991; Wahl et al., 1995 . In this study, feeding performance of larvae of the greenback flounder Rhombosolea
tapirina, was assessed in two light regimes, irradiance of 5–6 mmol s
y1
m
y2
and total darkness, to confirm that greenback flounder larvae are primarily visual feeders. Feeding
response of two groups of larvae, one with prior exposure to rotifers only and one with Ž
prior exposure to both Artemia and rotifers, was then examined in the light 5–6 mmol
y1 y2
. s
m to determine the effect of prior prey exposure on subsequent prey selection.
2. Materials and methods
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