North Hilo (Hilo Palikū) Coastal Fishery Assemblages: Global Climate Change Impacts Modeled Along a Highly Constrained Hydrological and Precipitation Gradient

Akau, James Jacob
Hart, Patrick
Tropical Conservation Biology & Environmental Science
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For centuries coastal fish communities have sustained human populations throughout the Hawaiian archipelago. Fish populations not only provide sustenance, but have also been and continue to be a source of inspiration for Hawaiian culture. The advent of global climate change and corollary increases in sea level temperature has compromised coral reef health and disrupted the ecological stability of nearshore systems. Global climate change and associated elevated atmospheric carbon dioxide has affected watershed function, especially rainfall magnitude and frequency. Since 1958 average rates of precipitation have decreased from 5 to 40 %. Coastal and estuarine environments are especially sensitive to runoff and stream discharge, which affect food availability for fishes, juvenile recruitment, benthic substrate, salinity levels, and fish community composition. To examine the effects of global climate change on coastal ecosystems, I’ve compared salinity levels, benthic substrate, fish community assemblages, species relative abundances, and food web structure across a precipitation gradient from Pepe‘ekeo (6000mm rain/yr) to Laupahoehoe (300mm rain/yr) along the Hilo Paliku (North Hilo), Hawai‘i coastline. To investigate the effects of variable fresh water inputs to near shore fishery assemblages, I compared recorded fish biodiversity, species relative abundances, and benthic substrate at Pepe‘ekeo and Laupāhoehoe using fish visual surveys on SCUBA and free diving. While free diving, I also used a Hobo data conductivity logger to measure salinity levels spatially and over time at Pepe ‘ekeo, Kolekole, and Pepe‘ekeo. Corals, which provide habitat and food for fishes, are sensitive to extreme fluctuations in salinity. Most corals have a salinity tolerance range between 28.7. Coral percent cover and fish biodiversity was significantly greater at Laupāhoehoe when compared to Pepe‘ekeo (P < 0.001). This demonstrates that more coral provide a more variable habitat for greater fish diversity, and that changes in rainfall and coastal salinity levels are important to maintain this diversity. With an understanding of how decreased stream flow will impact near-shore fish communities, we can begin to develop adaptive management strategies to maintain stream flow during periods of drought or return water to streams from diversions. This information can help to develop and support effective near-shore fisheries management at the community and legislation level. Keywords: precipitation gradient, fishery assemblage, food web dynamics
Aquatic sciences, Conservation biology, Environmental science, Benthic Habitat, Coastal Salinity, Fishery Community Assemblages, Global Climate Change, Precipitation Gradient
61 pages
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