Advancing the science and practice of conserving hihiwai: using ecology and traditional ecological knowledge to identify and overcome threats to an endemic Hawaiian gastropod
Date
2021
Authors
Ka'awa-Gonzales, Kiloaulani E. C., author
Pejchar, Liba, advisor
Clements, William H., advisor
Niemiec, Rebecca, committee member
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Abstract
Aquatic gastropods are valuable indicators of stream health in tropical ecosystems globally. Sustaining gastropods on islands is particularly important because these species provide numerous ecosystem services such as water purification, nutrient cycling, mediating the transfer of carbon through food webs, and providing sustenance for people. Hihiwai (Neritina granosa) is an amphidromous snail that was used as a subsistence food source in ancient times by Native Hawaiians and is still harvested today. Yet, this species is of conservation concern and both the ecological factors associated with its density and distribution as well as the socio-cultural knowledge associated with this species are largely unknown. Bridging Traditional Ecological Knowledge (TEK) and western science, which requires valuing indigenous knowledge and leadership and incorporating these ways of knowing into conservation science and practice, is an effective strategy to address this paucity of information in local and Indigenous communities. TEK is particularly important on islands where indigenous communities steward their often imperiled cultural and natural heritage. Evaluating the factors contributing to hihiwai loss and recovery using a combination of western science and TEK could serve as a model for Indigenous and local communities at the marine/freshwater interface globally. To address these knowledge gaps, I surveyed four streams on the Hawaiian Islands of Molokai and Maui to 1) determine which characteristics of stream systems are associated with Hihiwai population density across age classes, and 2) evaluate the size distribution of adult hihiwai as a function of stream characteristics. Specifically, I used stratified random quadrat sampling to assess hihiwai densities along an elevational gradient in streams with (n = 2) and without (n = 2) diversions. I collected data on stream characteristics such as width, depth, velocity, discharge, temperature, shading, and substrate. I found that hihiwai recruits, juveniles and adults were more abundant in diverted streams, all size classes and adult length were positively associated with stream depth, adult hihiwai were more likely to occur at higher elevations, and there was an inverse relationship between adult size and density, with larger hihiwai more likely to occur where adults were least abundant. In parallel with the stream surveys, I conducted semi-structured interviews with 20 local community members on Molokai to examine how traditional ecological knowledge and local experience can be used to better understand the ecology and cultural value of hihiwai, and to engage local communities in the conservation of this species and its habitat. Three major takeaways were identified as relevant for understanding the drivers, impacts, and next steps for hihiwai conservation: 1) community members believe that hihiwai populations are decreasing due to a combination of direct (overharvesting, water diversions) and indirect (higher stream temperatures, invasive plants) anthropogenic effects; 2) The perceived decrease in hihiwai abundance on Molokai has resulted in fewer opportunities for local people to connect with each other and spend quality time (eating and picking hihiwai), a loss of historic knowledge of hihiwai and cultural identity, and has disrupted the transmission of cultural and ecological knowledge to the next generation; and (3) Community members emphasized the need for informed local conservation leaders who represent the interests of the local Molokai people to guide and enforce hihiwai and Hawaiian stream management. Although community perceptions of whether bottom-up or top-down management strategies would be more effective were mixed, there is a general consensus that a change in values toward hihiwai harvest and possible harvest limits are needed to ensure healthy hihiwai populations in the future. My findings from this cross disciplinary study highlight the overlap, as well as the novel information that can emerge from integrating ecological and social research. Bridging the gap between western ecological science and TEK through local community collaboration will be critical for developing effective management plans that ensure ecological and cultural sustainability of hihiwai in Hawaii.
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Subject
aquatic macroinvertebrates
gastropods
traditional ecological knowledge
community-based conservation
aquatic ecology
Pacific Islands