Oral Presentation Freshwater Sciences 2023

Characterizing Hydrological Habitats Used by Stream Fauna in East Maui, Hawai‘i (#541)

Yinphan Tsang 1 , Ayron M Strauch 2 , Jody Kimmel 3 , Skippy Hau 3 , Cody Ching 2
  1. University of Hawaiʻi at Mānoa, Honolulu, HAWAII, United States
  2. Commission on Water Resource Management, Surface Water Protection and Management Branch, State of Hawaiʻi Department of Land and Natural Resources, Honolulu, Hawaii, United States
  3. Division of Aquatic Resources, State of Hawaiʻi Department of Land and Natural Resources, Honolulu, Hawaii, United States

To test the current understanding of patterns in recruitment and habitat use in Hawai‘i, we surveyed 48 sites across 30 streams on Maui, Hawai‘i, with reaches categorized by elevation as mountain (>183m), mid-reach (60-183m), and near-mouth (<30m), were surveyed for species abundance and habitat conditions. Seven native fauna were identified– ʻoʻopu nōpili (Sicyopterus stimpsoni), ʻoʻopu nākea (Awaous stamineus), ʻoʻopu ʻalamoʻo (Lentipes concolor), ʻoʻopu ʻakupa (Eleotris sandwicensis), ʻōpae kalaʻole (Atyoida bisulcata), hīhīwai (Neritina granosa), āholehole (Kuhlia sandvicensis), and three non-native species -- Tahitian Prawn (Macrobrachium lar), Green Swordtail (Xiphophorus hellerii), Mosquitofish (Gambusia affinis). Habitat characteristics measured included elevation, depth, velocity, Froude number, and habitat types (i.e., pool, riffle, run). Types of terminal reaches at the stream mouth (i.e., plunge pool vs. estuary) were classified for each stream. We examined species distribution against the associated hydrological metrics with parametric and non-parametric analyses. As expected, ʻōpae and ʻalamoʻo used mountain reaches habitats, hīhīwai, nōpili, nākea were most abundant in mid-reach, and āholehole and ʻakupa exclusively utilized near-mouth reaches. Among non-native, Tahitian Prawn were found at reaches of all elevations, and Green Swordtail and Mosquitofish utilized mostly mid-reaches. All species were found in a similar range of habitat depths between 25 and 75 cm. Āholehole and nōpili were found at rapid flow, and ‘akupa were found in slower flow. Hīhīwai and ʻalamoʻo were surprisingly found together in many sites; Tahitian Prawn, hīhīwai, and nākea were also co-located in many. Unsurprisingly, Mosquitofish and Green Swordtail were found in the same sites. We found that terminal reach significantly affected species composition. Using non-parametric analysis, we found that Froud number would likely explain the distribution of Tahitian Prawn, ʻalamoʻo, and Green Swordtail. These findings verified the importance of hydrological characteristics to stream fauna distributions and provide critical information for prioritizing stream habitat conservation and management.