PARENT SESSION
Novel Approaches in Environmental Assessments Poster Session.
Thursday, November 16, 2000
8:00 AM to 12:00 PM
CC West/Center Exhibit Hall
(PHA067) Truss analysis: a novel methodology for the identification of fish condition.
Fitzgerald, Dean G.1, Nanson, Jeff W.1, Adams, S. Marshall2, 1 2
ABSTRACT- Traditional techniques for quantifying fish condition rely on approaches that are simple, cheap, and time-efficient but these do not always accurately reflect fish condition or provide for repeated measures over time. Truss analysis, an approach traditionally applied by taxonomists to discriminate physically-similar fishes, can also be used to quantify the effects of environmental stressors on fish condition and morphology. A "truss" is a line connecting two morphological landmarks (e.g., insertion points of fins) that can be linked in a network of polygons to quantify the longitudinal, vertical, and oblique dimensions of the body. The methodology is predicated on the conservation of skeletal structure and unique body ratios in fishes. Complete characterization of form involves computer-aided image analysis and comparisons completed among members of the same species used to identify changes in body condition or shape associated with genetic or phenotypic aspects of the life history. This approach can be extended to evaluate the effects of environmental stressors such as contaminants on morphology. To illustrate the usefulness of truss analysis, we quantified the morphology of yellow perch (Perca flavescens), a common fusiform-shaped fish, raised in the lab under different rations and field-collected individuals using traditional descriptors of condition and a 10-point truss network interpreted using standard principal component analysis. Truss analysis was also used to describe two other fishes with differing morphology: the laterally-compressed redbreast sunfish (Lepomis auritus) collected from habitats with high metal loadings and the dorsally-ventrally compressed razorback sucker (Xyrauchen texanus) collected from habitats with high selenium loadings. Validation of new environmental bioassessment approaches requires comparison with established methods in field and lab settings. Our findings suggest that the potential exist to use truss analysis as an alternative method for the quantification of fish condition and morphology in lab or field situations.
Key words: truss analysis, body condition, fish, assessment