A Behavioral Study Of The Hawaiian Goby-Shrimp Relationship And The Effects Of Predation On The System

Abstract

The belief that the relationship between certain gobies and snapping shrimp (Alpheidae) is mutualistic typically includes the assumption that predation is a selective force driving the co-evolution of the relationship. In this study, I first showed the importance of the Hawaiian shrimp goby (Psilogobius mainlandi) to the sheltering behavior of its associated alpheid shrimp. Shrimp spent 53.6 ± 21.8 percent of light hours in the day outside burrows with gobies present, but only 6.9 ± 3.4 percent of the time outside without gobies present. I then examined effects of predation by experimentally excluding predators on gobies from several I.S-m square plots and observing the subsequent density and size of gobies. Over the 5 months of predator exclusion, no significant effect on goby density was detected (ANOYA; p = 0.345). The most conspicuous results of the exclusion were the changes in the size classes of gobies (ANOVA, P < 0.001). Plots with exclosures had a mean of 2.23 more large gobies (> 4 cm TL) than plots with no exclosures. In a final part of the study, I documented the daily cycle of activity of the snapping shrimp, Alpheus rapax, with an associated goby present. The results indicate that A. rapax increases foraging and burrow maintenance activities toward the end of daylight. Overall, this study was able to test the widely held assumption that predation can be a selective pressure on the goby-shrimp association.