Some factors governing prey selection by the 15-spined stickleback, Spinachia spinachia (L.)

Using mysids as prey, the relative importance of four characters governing prey selection by Spinachia spinachia (L.) were examined. Moving prey were taken in preference to stationary prey of equal length and when the fish were hungry they could be induced to take moving non-optimum sized prey in preference to optimum sized stationary ones. A comparison of the frequency of attack on portions of the prey showed that heads were preferred to tails and darkened mysids to light ones. The order of preference was dark colour > head > light colour > tail and there was some indication that the stimuli presented by these characters were additive. It is concluded that the fish attacked the head of the prey because of its shape (greater thickness and presence of appendages) and darker colour. The colour of the prey did not affect the size (length) of prey taken. In general, the stimuli presented by the four characters could be ranked in the order movement ⩾ length > colour > shape.