Larval Habitat Preference of the Endemic Hawaiian Midge, Telmatogeton Torrenticola Terry (Telmatogetoninae)

Document Type

Article

Publication Date

1-1-1997

Publication Source

Hydrobiologia

Abstract

Telmatogeton torrenticola Terry is a large endemic chironomid (last instar >20 mm) commonly found in high gradient Hawaiian streams on smooth rock surfaces with torrential, shallow flow and in the splash zones of waterfalls. We have quantified benthic water flow in larval habitat in a 50 m segment of Kinihapai Stream, Maui using a thermistor-based microcurrent meter. Under base flow conditions at sites suitable for larval attachment, depth was measured and bottom water velocity measurements were made ≈ 2 mm above populations. Larval densities ranged from 386.9-1178 m-2, habitat bottom water velocities from 13.4-64.2 cm s-1, and water depths from 1.5-50 cm. Bottom velocities of sites with zero larvae ranged from 20.8-21.8 cm s-1 with depths from ≈ 50 to > 160 cm. Larval densities were greatest in areas with high bottom water velocities and shallow depths. Stepwise multiple regression analyses showed that density could be confidently predicted best by Froude number (r = 0.81; p = 0.008). In the absence of Froude number as a regression term, the best variable to predict larval density was bottom velocity ratio: relative depth ratio (r = 0.75; p = 0.019). In addition, the torrential habitat of the larvae was always characterized by a periphyton community that appeared to be the primary food resource for the larvae. These data suggest that torrential flows over appropriate substrates are important factors regulating habitat availability for T. torrenticola and that reduced discharge (e.g. affected by water diversions) could significantly reduce the amount of available habitat for this organism and other flow sensitive stream fauna.

ISBN/ISSN

Electronic ISSN: 1573-5117; Print ISSN: 0018-8158

Publisher

Springer

Volume

346

Peer Reviewed

yes

Issue

1-3

Keywords

Benthic water velocity, Chironomidae, Habitat, Macroinvertebrate, Micro-flow, Stream depth, Tropical stream

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