COMPARISON OF FISH ASSEMBLAGES AND HABITAT USE OF NATIVE AND NON-NATIVE ESTUARINE SPECIES IN A FISHPOND COMPLEX IN HILO, HAWAI‘I

Date
2019-12
Authors
Tabandera, Ricky Kanaina
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Grabowski, Timothy .
Department
Tropical Conservation Biology & Environmental Science
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Abstract
Estuaries are highly productive systems that provide refugia for juveniles of many exploited nearshore fish species and represent essential nursery habitat. Traditional Hawaiian fishponds, called loko iʻa, were situated on areas to exploit the increased productivity due to the mixing of nutrient rich groundwater with seawater. These structures are essentially artificial estuaries; however, due to their impounded nature and varying levels of management, loko iʻa have the potential to differ in their ecologic role relative to the natural estuaries. I selected three fishponds located in Hilo, Hawaiʻi: Hale O Lono, Loko Waka, and Waiāhole and embayment of Hilo Bay shared by all ponds. These locations represent a broad range in size, salinity regime, habitat, and management strategy. I utilized temporally and spatially robust sampling, mark recapture methods, and habitat mapping to elucidate the effects of environmental conditions within a fishpond complex on fish assemblage habitat association and population parameters of five important game species: Striped Mullet Mugil cephalus, Kanda Osteomugil engeli, Yellowstripe Goatfish Mulloidichthys flavolineatus, Reticulated Flagtail Kuhlia sandvicensis, and Hawaiian Flagtail Kuhlia xenura. I found that a salinity and mud habitat proportion gradient had the greatest explanatory power on the composition of fish assemblages in this system. The embayment and Hale o Lono comprised one physicochemical and habitat grouping, whereas Waiāhole and Loko Waka ponds comprised a second, disparate grouping. The bay and Hale O Lono grouping comprised of species rich mesohaline conditions, whereas Waiāhole and Loko Waka grouping was depauperate and spring-water dominated. Population parameters of game species were observed to vary with location and habitat. Differences in apparent survival among locations appear to be the result of differences in habitat with mud being negatively associated with survival in most species. The fish populations in the embayment and fishponds do share some degree of connectivity as movement of Yellowstripe Goatfish was observed between Hale O Lono and the embayment; and Kanda movement was observed between Loko Waka and Waiāhole. Results indicate that limited connectivity to the marine environment results in conditions too osmotically challenging to support most native species. These findings can assist in prioritizing rehabilitation efforts in similarly spring fed ponds to reduce non-native species abundance and potential increase fish production.
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Wildlife management, Wildlife conservation, Conservation biology, artificial structures, fish distribution, fish nursery habitat, fisheries resources
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53 pages
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