Geology topics

M. Keith Cox

Publications and source records attributed to M. Keith Cox.

3 recordsLinked to original sources

USGS2019

Energetic status of Alaskan Chinook Salmon: Interpopulation comparisons and predictive modeling using bioelectrical impedance analysis

Adult Pacific Salmon Oncorhynchus spp . undertake energetically demanding migrations wherein they must have adequate energy reserves to survive to spawning locations and reproduce. Proximate analysis provides insight into available energy stores (e.g., lipids), but the ability to non-lethally monitor energetic status may be useful for managers to better understand how energetic status affects salmon populations in light of population declines and threats from climate change and habitat alteration. Chinook Salmon Oncorhynchus tshawytscha (N = 129) were sampled for proximate analysis from four populations in Alaska to examine variation in energetic status pre- and post-spawning migration and to create predictive bioelectrical impedance analysis (BIA) models for this species. We also tested two BIA devices (Q2 and CQR), whether models were generalizable to a con-specific (Chum Salmon Oncorhynchus keta), and the feasibility of integrating BIA into field studies. Populations sampled pre- spawning migration had higher percent lipid (N = 77; mean = 42.57%) than those collected post spawning migration (N = 52; mean = 19.71%). Total percent lipid and water were more accurately predicted from the Q2 device based on BIA measurements (RMSE = 5.33; RMSE = 2.43, respectively), relative to CQR device measurements (RMSE = 6.27; RMSE = 2.66). Between-species (Chinook to Chum RMSE = 19.47; Chum to Chinook RMSE = 7.69) models were less accurate than species specific models created for Chinook and Chum Salmon, therefore single species models should be used. We field-tested the BIA model to predict Chinook Salmon %lipid and %water on a remote Southeast Alaska river. Techniques were quickly taught to field crews and predictions were similar to other pre-spawning migration estimates. Our results indicate that integration of BIA into population monitoring could be a valuable tool to assess spatial and temporal patterns of energetic status of Chinook Salmon.

Alaska↗

USGS2015

Bioelectrical impedance analysis: A new tool for assessing fish condition

Bioelectrical impedance analysis (BIA) is commonly used in human health and nutrition fields but has only recently been considered as a potential tool for assessing fish condition. Once BIA is calibrated, it estimates fat/moisture levels and energy content without the need to kill fish. Despite the promise held by BIA, published studies have been divided on whether BIA can provide accurate estimates of body composition in fish. In cases where BIA was not successful, the models lacked the range of fat levels or sample sizes we determined were needed for model success (range of dry fat levels of 29%, n = 60, yielding an R 2 of 0.8). Reduced range of fat levels requires an increased sample size to achieve that benchmark; therefore, standardization of methods is needed. Here we discuss standardized methods based on a decade of research, identify sources of error, discuss where BIA is headed, and suggest areas for future research.

Fisheries↗

USGS2005

Non-lethal estimation of body composition of Yukon River salmon

Because of the importance of Chinook salmon to commercial and subsistence fisheries on the Yukon River, further study of the factors that may affect the success of this species and our ability to manage the fisheries is warranted. Critical to these studies is the determination of the amount of lipids (fat) stored and available to the fish as its primary energy source for migration and spawning. Recent developments of Bioelectrical Impedance Analysis (BIA) promise a simple, non-lethal means of estimating proximate composition (e.g. fat, protein, water content) for field applications with fish. The goal of the project was to develop BIA models for Chinook salmon from the Yukon River watershed that would permit the non-lethal estimation of body proximate composition for use in field studies. Our results clearly demonstrated that BIA can be used to estimate proximate composition and energy density of salmon. While some minor refinements were suggested, the methodology can be used in a wide variety of field applications. For instance, application of the BIA models to predict energy levels of fish during their migration will allow evaluation of management programs, while also yielding data that can be used to evaluate energy use along the migratory path. Correlations of energy level with ongoing tagging, radio-tracking, and genetic studies also have the potential to allow managers and scientists to understand the relationship between fat content and distance to spawning location. These models have the potential for application to this species in other river systems. They also provide tools for a variety of other scientific investigation such as: 1) differences in energy stores in spawning and recruitment success; 2) effects of global warming on migratory salmonid stocks; and 3) differences in annual flow and temperature regiments upon migratory energy costs and resulting recruitment success.

Alaska, Yukon↗