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 Related Pages

	Fish Information Table (39KB)
	Fish Measurements (19KB)

Collection Methods

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Taxonomic Identification
Taxonomic identification is made by an ichthyologist who is familiar with the taxonomy of fish species commonly found in the study unit. Of those fish that can be identified, measurements of length and weight are taken and external anomalies determined. Those fish which cannot be identified are preserved for later identification.

Length Measurements
Length measurements are determined with a measuring board consisting of a metric scale on a wooden or plastic base. Fish are measured with the body positioned on its right side, the head facing the observer's left, and the mouth closed. Total length as well as standard length are measured to the nearest millimeter. Total length is the distance from the mouth to the extreme tip of the caudal or tail fin. This measurement is the conventional body-length measure of fish for fisheries agencies. Standard length is the length from the mouth to the posterior end of the fleshy caudal peduncle. This length is important to taxonomic studies because it is unaffected by caudal fin anomalies.

Length measurements are recorded for at least 30 individuals of a species collected from the sampling reach. These specimens are randomly selected to obtain a representation of the variety of lengths.

Weight Measurements
Weight measurements are obtained by placing the fish into a small plastic container set on a portable electronic balance. Weight is recorded to the nearest gram. For individuals of a species weighing less than 1 g, an average weight of at least 30 individuals is determined.

External Anomalies All fish are examined for the presence of external anomalies. External anomalies are defined as the presence of externally visible skin or subcutaneous disorders, or parasites. The presence of these anomalies may indicate environmental stresses, intermittent stresses, behavioral stresses, or chemically contaminated substrates. External anomalies include deformities, eroded fins, lesions, tumors, diseases, and parasites.