Publication Abstract

The cryptic responses of hatchery-reared sole to a natural sand substratum

T. Ellis, B.R. Howell amd R.N. Hughes

The cryptic responses of burial and colour adaption of hatchery-reared sole were compared with those of wild sole in laboratory experiments. Both reared and wild sole selected a sand substratum in preference to a hard substratum. Reared sole quickly buried despite no previous experience of sand. Light motivated burial of reared and wild sole. Motivation to bury was apparently as strong in reared as well as wild sole, shown by the number of repeated attempts to bury into a hard substratum. The efficiency of burial of reared sole was, however, lower than that of wild sole, but increased after placement on sand. Motivation to bury is therefore hard-wired, but efficiency is affected by experience. The reactive distance of reared sole to a standardised predation threat was the same as that of wild sole and was shorter when buried (6 cm), than when not buried (15 cm). Burial therefore affected the decision to respond to a predator threat, indicating that burial is a cryptic behaviour. Munsell colour charts were used to determine the time required for reared sole to match the skin colour'tone' ofwild sole after placement on sand. Adaption of colour value (lightness) took 4-7 d, but adaption of chroma (intensity of colour) and hue took considerably longer, 3 3 d and 69 d respectively. It is therefore recommended that flatfish reared for stock enhancement exercises are conditioned to sand prior to release due to the relatively long time required for crypsis to improve through colour adaption and burying.

Reference:

T. Ellis, B.R. Howell amd R.N. Hughes, 1997. The cryptic responses of hatchery-reared sole to a natural sand substratum. Journal of Fish Biology, 51(2): 389-401