Ecology, abundance, diversity, and distribution of larval fishes and Schindleriidae (Teleostei: Gobioidei) at two sites on Oʻahu, Hawaiʻi

Abstract

Light traps were deployed in Hanauma Bay (the Bay) over a 2.5-year period to determine the effect of physical factors on the catch of larval fishes and Schindleriidae. Significantly more larval fishes and Schindleria were caught in light traps moored over sand habitat than in those over rubble, coral, or mixed habitats. The currents of the outer reef of the Bay were mapped using drogue analysis, but the recorded pattern (shoreward and westerly) did not explain the catches of larval fishes or Schindleria. Other measured physical factors (e.g., wave height, wind speed, temperature, etc.) were not statistically correlated with light trap catches; only tidal range had a significant (p=0.017) relationship with Schindleria catch. The strong swimming abilities of late-stage larvae and adult Schindleria can probably overcome small-scale physical factors, specifically currents typical to the Bay. Only 119 fish larvae were caught in 81 samplings, considerably less than reported in other regions. This is probably due to an absence, in Hawaiʻi, of the most common species caught in light traps elsewhere. In Kaneʻohe Bay, paired silent and sound traps were used to determine if sound is an attractant or deterrent for larval fishes and adult Schindleria. Sound appeared to be a deterrent for larval shorefishes (p=0.13) and Schindleria (p=0.058), and an attractant for larval reef fishes (p=0.104). Shorefishes and Schindleria may use sound to avoid predation and reef fish may use sound to recruit to suitable habitat. Schindleria, with two species in Hawaiʻi, are progenetic, cryptic fishes and little is known about their ecology. Otolith and histological analyses revealed that both species have extremely high growth rates: Schindleria pietschmanni grows an average of 0.72 mm/day and Schindleria praematura grows an average of 0.60 mm/day. For both species, females were found to be larger than males (p=0.007, p=0.001) and in S. pietschmanni, temperature was negatively related to growth rate and size (p=0+). This genus is abundant in Hawaiian waters (3600+ were caught in my light traps) and may be an important part of the energy budget of a reef, due to sheer number, fast turnover, and high productivity.