Use of 'cageless' barriers to enclose small starfish in short-term field experiments

Abstract

Although small starfish may exert significant grazing effects on hard substrata, quantification of these effects has been difficult because of methodological limitations. Previously, caging small starfish for field experiments has failed because animals can escape through cage meshes and confounding effects may arise as the starfish can feed on organisms growing on the fences themselves, rather than the surface under investigation. Here, we investigated the efficiency of alternative barrier methods, such as antifouling paint and sticky barriers, for shorter-term experimental manipulation of the herbivorous starfish Parvulastra exigua. Laboratory and field manipulations tested the hypotheses that barriers are efficient in retaining starfish within plots and that the chemical repellent of the barriers does not affect the normal functioning of starfish. The results showed that the sticky barrier did not deter P. exigua, but antifouling paint retained greater numbers of individuals within barrier plots than in controls, with no short-term effects on starfish righting response.