Northern Clingfish(Gobiesox maeandricus): Environmental wave forces and the effect of water levels on their distribution

Abstract

Diurnal exposure to air during fluctuating tides and forces imposed by rushing waves make the intertidal zone, the habitat of the Northern clingfish, uniquely difficult to survive in. The goals of this study were to answer (1) what are the relevant wave forces acting upon the fish on the San Juan Island and (2) how do changing water levels and thus daily time spent under water percentages (DTUW%) affect their distribution? Dynamometers were built and distributed at 3 locations on the San Juan Island to measure the maximum wave velocities. Results show that over all, wave velocities acting on the island do not exceed 4m/s. Clingfish may have the ability to withstand higher velocities than those measured. A transect was set up at the Reuben Tarte (RT) beach and fish distribution was recorded during the lowest tides between June 30, 2014-July30, 2014. Water heights to reach MLLW were calculated at RT using the law of cosine and these values were later correlated to NOAA’s daily water levels to find DTUW%. Clingfish were found exclusively in areas that had at least 80 DTUW% which leads to the conclusion that water levels and thus DTUW% are important determinants in clingfish survival.