Prey catching in the archer fish: angles and probability of hitting an aerial target

When trying to squirt down aerial arthropods, archer fishes (Toxotidae) hav e to cop image of the target by refraction of light at the water surface. I t has been suggested, and accepted, that Toxotes the effect of refraction b y squirting vertically. In our previous study, however. Toxotes jaculatrix would avoid chatareus was observed to squirt under a wide range of angles, including angles much smaller than 90 degrees. The aim of the present study was to asses in T. chatareus (N = 15), the frequency distribution of angle s used. the relation between angle and probability to hit. the relation bet ween target height and angle, and the smallest angles the fishes can use. T he outcome was a distribution with a range of 102-58 degrees and a median o f 74 degrees, no relation between angle and probability to hit, no relation between target height and angle and a smallest angle of 45 degrees. The re sults clearly indicate that T. chatareus does not evade the refraction effe ct by squirting only vertically (90 degrees), but masters a considerable re fraction effect thanks to a mechanism that is not investigated here. The ca pacity to hit prey under a wide range of angles is seen as an important ada ptation to the natural habitat where the visibility of prey is restricted r eserved.