Dorsal spines have been shown to provide precise age estimates for Common Carp Cyprinus carpio and are commonly used by management agencies to gain information on Common Carp populations. However, no previous studies have evaluated variation in the precision of age estimates obtained from different sectioning locations along Common Carp dorsal spines. We evaluated the precision, relative readability, and distribution of age estimates obtained from various sectioning locations along Common Carp dorsal spines. Dorsal spines from 192 Common Carp were sectioned at the base (), immediately distal to the basal section (), and at 25% (), 50% (), and 75% (section 5) of the total length of the dorsal spine. The exact agreement and within‐1‐year agreement among readers was highest and the coefficient of variation lowest for . In general, age estimates derived from had similar age distributions and displayed the highest concordance in age estimates with . Our results indicate that sections taken at ≤ 25% of the total length of the dorsal spine can be easily interpreted and provide precise estimates of Common Carp age. The greater consistency in age estimates obtained from indicates that by using a standard sectioning location, fisheries scientists can expect age‐based estimates of population metrics to be more comparable and thus more useful for understanding Common Carp population dynamics. Received April 2014; Accepted March 31, 2015
The construction and operation of dams represents one of the most significant anthropogenic impacts to the aquatic environment of freshwater ecosystems and includes changes in flow, temperature, water chemistry, sedimentation, and nutrient delivery. Despite the substantial changes caused by dams, we have a limited understanding of how dams influence important rate functions of fish, including growth rates. This study measured the growth rates of Rainbow Trout Oncorhynchus mykiss from successive captures of individually marked fish over seven annual increments within four river sections downstream of Libby Dam on the Kootenai River, Montana. We modeled the influence of hydropower‐related environmental variables on Rainbow Trout length and weight growth rates using linear mixed‐effects models. The top models predicting annual length and weight growth rates contained measures of water chemistry (ratio of total N to total P [N:P]) during the growing season, winter substrate coverage by the diatom Didymosphenia geminata, and an interactive term between winter D. geminata coverage and fish size at tagging. Winter D. geminata coverage and N:P were negatively correlated with annual growth rates, but the interactive term indicates that the influence of winter D. geminata coverage disproportionally affects smaller fish more than larger fish. We hypothesize that N:P and D. geminata are influencing Rainbow Trout growth rates through lower‐trophic‐level impacts. Top Rainbow Trout length and weight growth models explained 94.6% and 92.2%, respectively, of the annual variability in growth rates, of which 87.7% and 76.2%, respectively, were attributable to fixed effects. An experimental nutrient addition study and robust trophic monitoring efforts in the Kootenai River downstream of Libby Dam would be an effective means of independent corroboration of these study results. If successful, nutrient addition may be an effective management strategy to improve annual Rainbow Trout growth rates, mitigating for the nutrient retention occurring in the large reservoir upstream of Libby Dam.
North American Burbot Lota lota maculosa occupy habitats from deep, cold lakes to prairie streams. Controlled laboratory trials were conducted to evaluate the growth, immune response, and thermal stress physiology of juvenile Burbot subjected to fluctuating, high diel temperatures. Age‐0 Burbot from a captive propagation program associated with population restoration in the Kootenai River, Idaho, were tested in temperature cycles that imitated summer conditions observed in regional stream habitats. The diel temperature cycle for the treatment group varied from 18°C at night to 27°C during the day, whereas the control group was held at a constant temperature of 14°C. We evaluated survival, growth, feed efficiency, heat shock protein 70 (hsp70) levels, hsp70 gene expression, serum lysozyme levels, and proximate body composition in samples taken from fish before, during, and at the completion of the trials. Both treatments had high survival and similar growth rates, but the control group gained significantly more weight and had better feed conversion rates than the treatment group. Mean hsp70 expression and hsp70 abundance were significantly higher in the treatment group but varied between sampling events and between tissue types. Expression of hsp70 in treatment fish was highest on day 15 for muscle tissue (251 times the control value) and on day 30 for liver tissue (1,131 times the control value), with variable abundance of hsp70 at both sampling points. Serum lysozyme levels were not different between treatments. An additional short‐term trial was conducted to evaluate the response of Burbot to upper lethal temperatures, with daily maxima approaching 32°C. Despite being commonly referred to as a coldwater stenotherm, the Burbot displayed resilience to thermal stress, and were able to withstand temperatures exceeding 31°C. Received September 13, 2016; accepted May 12, 2017 Published online July 31, 2017
In response to population declines of North American Burbot Lota lota maculosa (hereafter, Burbot), conservation aquaculture methods have been developed for this species. In general, Burbot are relatively resistant to many salmonid pathogens; however, cultured juvenile Burbot have experienced periodic epizootic disease outbreaks during production. A series of trials was conducted to determine the virulence of select bacteria isolated from juvenile Burbot after outbreaks that occurred in 2012 and 2013 at the University of Idaho's Aquaculture Research Institute. Initial clinical diagnostics and sampling resulted in the isolation of numerous putative bacterial pathogens. To determine which bacteria were the most likely causative agents contributing to these epizootics, juvenile Burbot received intraperitoneal (IP) injections of select bacteria in log-phase growth. Mortality associated with specific isolates was recorded, and more comprehensive challenges followed this initial screening. These challenges used side-by-side IP and immersion methods to expose Burbot to potential pathogens. The challenges resulted in significantly higher mortalities in fish after IP injection with two Aeromonas sp. isolates compared to controls, but no significant difference in mortality for immersion-challenged groups was observed. Results demonstrate that two Aeromonas sp. isolates cultured from the epizootics are virulent to Burbot.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.