Alpheid shrimp and gobiid partnerships are widespread across the tropics. Most of the work that has been done on these shrimp-goby relationships has been done in the Red Sea (Luther, 1958; Magnus, 1967; Karplus, 1981; Karplus et al., 1981; Polunin and Lubbock, 1977) and Japan (Harada, 1969; Yanagisawa, 1978, 1982, 1984). There have also been a few smaller studies on an Atlantic association (Karplus, 1992) and only one on the Hawaiian association (Moehring, 1972).
Nearly every report of the shrimp and goby relationship has noted that they are symbiotically mutualistic (reviewed by Karplus 1987). The alpheid shrimp dig holes in the predominantly sandy habitats where they live, providing protection for the gobies. The gobies stay at the entrance of the hole during the day, in close enough proximity to dart in for escape and at night for a resting hole. The gobies, which have much keener eyesight, provide a kind of ‘advanced warning system’ by being able to see potential predators earlier. The goby relays this information back to the shrimp through 1) its head-first entries and 2) a series of tail flicks which the shrimp detects through its antenna that are ‘continuously positioned on the fish’s body' (Moehring, 1972; Karplus, 1987, 1992).
Until recently, only Yanagisawa (1984) has attempted to correlate the behavior and abundance of shrimp gobies with predators. His study showed that in areas of a reef in Okinawa where predator abundance is low, the gobies roam farther from their burrows and are more abundant. In areas where the predator abundance is high, there are fewer shrimp-goby relationships and they are more cautious in their behaviors. This study was done, however, only as a sidenote in a larger ecological study of shrimp-gobies, and could not rule out any confounding factors that may have caused predator abundance to vary (ie. plankton distrubution, habitat, etc.). Given the large assumption that shrimp and goby live symbioticaly to avoid predation, it seems very important to quantify exactly what predators do to the system.
In French Poloynesia, Thompson (2004) experimentaly manipulated the environment to increase predator abundance in an effort determine the effect on the shrimp goby pair. He found that increasing predators, done by introducing large obsticles in the sand for predators to hide near burrows, decreased the abundance of shrimp gobies and decreased the number of large gobies in a sample plot.
Thompson's study is important in understanding the effects of predator additions to a system, but noone has determined what would happen to a system where predators are absent. Thus, the goal of this study is to determine if the same results are reached through an alternative method to Thompson's predation study whereby predators are excluded instead of increased.
