Condition index

About: Condition index is a research topic. Over the lifetime, 429 publications have been published within this topic receiving 14186 citations.

Estimating fitness : a comparison of body condition indices

Abstract: Behavioral ecologists might often benefit by the ability to directly measure an animal's body condition as an estimate of foraging success, and ultimately fitness. Here we compare the reliability and effectiveness of three indices of body condition that have been heavily used in the morphometrics literature. We examined the ratio index (body mass/body size), the slope-adjusted ratio index (based on regression slopes generated from a reference population), and the residual index (the residuals of a regression of body mass on body size). We present the results of tests performed in the field and laboratory on two ecologically and evolutionarily divergent spider species : the vagrant wolf spider Pardosa milvina (Araneae, Lycosidae), and the colonial orb-weaver Metepeira incrassata (Araneae, Araneidae). The ratio index correlated with body size, which weakened the strength of conclusions that could be drawn. The slope-adjusted ratio index requires an independent and large data set with which to generate the expected values, and was likewise sensitive to body size. The residual index, with appropriate transformations to achieve homoscedasticity, was the most reliable index because it did not vary with body size, and we recommend its general use in behavioral studies that require a condition estimate.

The selection of suitable indices for the measurement and analysis of fish condition

Abstract: A survey of the studies published in two leading fisheries journals revealed that the analysis and measurement of condition, based on length-weight data, has been performed using a wide variety of indices and statistical procedures. Eight forms of index were identified which can be categorized into those which measure the condition of individual fish, i.e. condition factors‘, and those which measure the condition of subpopulations as a whole, i.e. regressions of log, 10 weight on log, 10 length and the parameters of such regressions. Analysis of a test data set indicated that both the form of index and properties of the data set size can dictate the patterns of condition observed. The various indices were reviewed in terms of appropriateness, simplicity and statistical correctness. It was concluded that an index should be selected only after a detailed examination of both the underlying assumptions of the index and the properties of the data set.

Morphometric indices of body condition in birds: a review

Abstract: Morphometric estimates of body condition are widely used by ornithologists, but which estimates work best is a matter of debate. We review morphometric approaches (body mass, ratio and residual condition indices, predictive regression models, fat scoring, and abdominal profiles) for estimating body condition (defined as fat mass) in birds. We describe the strengths and weaknesses of each approach. Across diverse indices and species (~200 estimates total), the mean r 2 relating condition indices to mass of body fat was 0.55, and 64% of the r 2 values were greater than 0.50. But despite their generally good performance, condition indices sometimes perform poorly (i.e., r 2 is low). The data indicate that: (1) no single index was clearly best, (2) on average body mass alone, fat scores, and predictive multiple regression equations explained slightly more than 50% of the variation in fat content, (3) on average, ratio and residual indices explained slightly less than 50% of the variation in fat content, and (4) body mass alone, a variable that can be easily and reliably measured, is as good or nearly as good an indicator of fat content as any other condition index. We recommend that: (1) morphometric indicators of condition be empirically validated, (2) researchers publish their body composition data in sufficient detail that they can be used in future analyses exploring the relative merits of different condition indices, and (3) multiple regression directly on measured traits be used instead of condition indices whenever the condition index is not empirically validated.

A Quantitative Health Assessment Index for Rapid Evaluation of Fish Condition in the Field

Abstract: The health assessment index (HAI) is an extension and refinement of a previously published field necropsy system. The HAI is a quantitative index that allows statistical comparisons offish health among data sets. Index variables are assigned numerical values based on the degree of severity or damage incurred by an organ or tissue from environmental stressors. This approach has been used to evaluate the general health status offish populations in a wide range of reservoir types in the Tennessee River basin (North Carolina, Tennessee, Alabama, Kentucky), in Hartwell Reservoir (Georgia, South Carolina) that is contaminated by polychlorinated biphenyls, and in the Pigeon River (Tennessee, North Carolina) that receives effluents from a bleached kraft mill. The ability of the HAI to accurately characterize the health offish in these systems was evaluated by comparing this index to other types of fish health measures (contaminant, bioindicator, and reproductive analysis) made at the same time as the HAI...