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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 "aquaculture"

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    ItemOpen Access
    Cold summer stream temperatures reduce recruitment of native cutthroat trout populations
    (Colorado State University. Libraries, 2007) Coleman, Mark Anthony, author; Fausch, Kurt D., advisor
    Translocation is a key strategy for conserving subspecies of native cutthroat trout Oncorhynchus clarkii, which have declined markedly throughout their native ranges in North America. Previous research showed that translocation success in high-elevation southern Rocky Mountain streams was more likely in warmer streams, and suggested that cold temperatures could limit juvenile trout recruitment and explain translocation failures. However, the effects of cold temperature on recruitment had not been previously investigated. I studied these effects using an integrated laboratory and field approach. In the lab, age-0 Colorado River cutthroat trout O. c. pleuriticus were subjected to one of three natural temperature regimes during two years, which averaged 7°C, 8.5°C and 10.0°C during the warmest summer month. From hatching to swimup, mean survival was high during both years, ranging from 97% (warm regime) to 85% (cold). After swimup, warm regime fry had much greater survival and grew more than 60% larger, on average, than cold regime fry by the onset of winter in the 2003 experiment. The pattern of lower survival in colder temperature regimes held through mid-winter, with 76% survival (warm regime), 62% (intermediate), and 29% (cold). Likewise, during the 2004 experiment, survival to early winter ranged from 44% (warm regime) to 10% (cold). Most mortality in all treatments occurred during a recruitment bottleneck encompassing a 4- to 6-week period following swimup. A response surface analysis of percent dry weight data indicated that the energy content of fry at swimup was lower in colder regimes, and declined during the recruitment bottleneck in all regimes. In the field, I monitored temperatures and conducted surveys to estimate densities of age-0 fry at peak emergence in six headwater streams that varied in thermal characteristics. Density and growth increased with Celsius degree days during the growing season. My results indicate a strong recruitment bottleneck after swimup, when temperature-related energy deficits probably cause significant mortality. Fisheries managers in the southern Rocky Mountains may increase translocation success of native cutthroat trout by selecting sites with ≥800-900 degree days during the growing season, and fry grow to ≥30-35 mm by the end of the growing season.
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    ItemOpen Access
    Measuring the effects of ammonia and dissolved oxygen on juvenile burbot (Lota lota) growth and survival
    (Colorado State University. Libraries, 2021) Vaage, Ben, author; Myrick, Christopher, advisor; Angeloni, Lisa, committee member; Clements, Will, committee member
    Burbot, Lota lota are a candidate species for commercial aquaculture because of their palatability and optimal growth at temperatures similar to those used in freshwater trout aquaculture. However, data on burbot environmental tolerances and requirements are sparse, especially with reference to water quality parameters relevant to aquaculture, such as un-ionized ammonia (UIA) and dissolved oxygen concentrations. First, we used a two-phased approach to evaluate the effects of un-ionized ammonia on the growth and survival of burbot. We measured the acute toxicity of ammonia to juvenile burbot (mean SL: 144 ± 6 mm; mean wet weight: 27.3 ± 3.4 g) and calculated a 96-hr LC50 of 0.58 mg·L-1 UIA. We then measured the 60-d growth, food consumption rate, and performance of burbot (mean initial SL: 190 ± 6.9 mm; mean initial weight: 67.0 ± 4.5 g) reared in 0.00, 0.03, 0.06, 0.12, or 0.19 mg·L-1 UIA using a 20-tank flow-through system under optimal temperature (14.7°C) and dissolved oxygen (DO > 80% saturation) conditions. Elevated ammonia concentration significantly reduced daily food consumption and subsequent growth. Fish exposed to 0.03 and 0.06 mg·L-1 UIA showed temporal acclimation to UIA, achieving food consumption and growth rates on par with control fish after 30 days of exposure. The estimated effective UIA concentrations for 10 and 20 percent reductions in growth (EC10 and EC20) based on our data are: EC10 = 0.03 ± 0.006 mg·L-1 and EC20 = 0.050 ± 0.004 mg·L-1. We recommend rearing burbot under conditions that keep UIA levels ≤ 0.03 mg·L-1 based on our finding that above 0.03 mg·L-1 cause measurable reductions in growth rate. Following the ammonia studies, we exposed juvenile burbot (19.5 ± 2.2 g) to five dissolved oxygen concentrations (5.0, 5.8, 6.6, 7.4, and 8.3 (control) mg·L-1) for 9 weeks at 15°C. Variability was high in all treatments, and food consumption and growth rates did not differ among DO levels, although fish at 8.3 mg·L-1 grew ca. 29% larger than those at 5.0 mg·L-1. We also measured short-term hypoxia tolerance and resting routine oxygen consumption rates (MO2) of burbot that had been chronically acclimated to the same DO concentrations. Burbot acclimated to 8.3 mg·L-1 lost equilibrium (LOEcrit) at a significantly higher concentration (1.85 ± 0.33 mg·L-1) than that of the 7.4 and 6.6 mg·L-1 acclimated fish (1.50 ± 0.37 and 1.49 ± 0.27; respectively), while all other groups were intermediate (1.67 ± 0.28). The MO2s were not statistically distinguishable among acclimation groups (p-value = 0.25), but MO2 trended lower with decreasing DO concentrations typifying an oxyconforming species. In summary, juvenile burbot are quite tolerant to DO concentrations down to 5.0 mg·L-1. We recommend rearing burbot at DO concentrations > 7.0 mg·L-1 and that minimum short-term DO concentrations be kept > 4.0 mg·L-1in culture environments where multiple stressors may be present.