A correlation between phototactic response and first-feeding of Atlantic halibut (Hippoglossus hippoglossus L.) larvae

The correlation between positive phototaxis and feeding incidence at first- feeding for groups of Atlantic halibut larvae ranging in age from 210 to 24 0 degree days, post hatch, was examined. Phototactic response was measured as the fraction of larvae that responded by horizontal swimming towards a l ight source, and the median travel distance for the responding fraction of larvae. Within the ranges investigated, larval age, size or proportion of d eformed larvae had no significant effect on the phototactic response, or on the feeding incidence (deformed larvae excluded from analysis). The fracti on of larvae responding phototactically and the median travelling distance for responding larvae were significantly correlated. Feeding incidences aft er 24 and 48 h were also significantly correlated with both measures of pho totactic response. The possibility of using phototactic response in quality assessment is discussed.