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Department of Fish, Wildlife, and Conservation Biology

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https://hdl.handle.net/10217/100423
These digital collections include theses, dissertations, faculty publications, student publications, and datasets from the Department of Fish, Wildlife, and Conservation Biology. Due to departmental name changes, materials from the following historical departments are also included here: Fishery; Fishery and Wildlife Biology; Wildlife Biology.

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Browsing Department of Fish, Wildlife, and Conservation Biology by Subject "aquatic ecology"

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    Advancing the science and practice of conserving hihiwai: using ecology and traditional ecological knowledge to identify and overcome threats to an endemic Hawaiian gastropod
    (Colorado State University. Libraries, 2021) Ka'awa-Gonzales, Kiloaulani E. C., author; Pejchar, Liba, advisor; Clements, William H., advisor; Niemiec, Rebecca, committee member
    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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    Seasonal trophic niche dynamics of mottled sculpin and juvenile brown trout in a regulated Rocky Mountain river
    (Colorado State University. Libraries, 2023) Platis, Nitsa, author; Kanno, Yoichiro, advisor; Johnson, Brett, advisor; Kampf, Stephanie, committee member
    In temperate ecosystems, resource availability fluctuates seasonally due to changes in environmental conditions and productivity throughout the year. Intra- and inter-specific trophic niche overlap under resource limitation is a measure of competitive interactions and influences species coexistence and community dynamics, but patterns of this overlap are highly variable among regions and communities. In this study, we analyzed stomach content samples and stable isotope signatures to evaluate seasonal trophic niche dynamics of mottled sculpin Cottus bairdii (80-130 mm total length) and juvenile brown trout Salmo trutta (80-200 mm) in the Blue River, Colorado, USA, where aquatic production varies seasonally and has been reduced due to upstream dams. Prey biomass (i.e., benthic macroinvertebrates) peaked in spring and declined through summer and autumn. Stomach content and stable isotope analysis results revealed diet composition of mottled sculpin and brown trout shifted seasonally in response to changes in resource availability. In autumn, both species exhibited the highest frequency of empty stomachs and expanded population trophic niches due to increased inter-individual diet variation despite decreased individual trophic niche breadth. Interspecific trophic niche overlap was relatively high across all seasons, but the lowest degree of overlap occurred in autumn of both years. Isotopic analysis revealed similar trends of wider isotopic niches and reduced overlap in autumn compared to spring. Taken together, our data indicate that seasonal variation impacts individual and population-level trophic niche dynamics, as well as interspecific niche overlap between mottled sculpin and juvenile brown trout. These two species occur sympatrically in many coldwater streams throughout North America, and our findings indicate trophic segregation under resource limitation may serve as a mechanism that facilitates their coexistence.