Scale circuli patterns differentiate between hatchery-reared and wild Rutilus rutilus during evaluation of fish...

Area of Science:

• Ichthyology
• Aquaculture
• Ecology

Background:

• Distinguishing between hatchery-reared and wild fish is crucial for fisheries management and stocking assessments.
• Scale circuli patterns offer a potential morphological marker for fish origin.
• Roach (Rutilus rutilus) are a common freshwater fish species often subject to stocking programs.

Purpose of the Study:

• To develop and validate a discriminant function for classifying roach based on their rearing environment using scale circuli patterns.
• To apply this function to evaluate the success of riverine stocking by identifying the origin of recaptured fish.

Main Methods:

• Analysis of scale circuli patterns from known hatchery-reared and wild roach to build a discriminant function.
• Application of the developed discriminant function to classify the origin of roach captured during a riverine stocking evaluation.

Main Results:

• The discriminant function achieved accurate classification of roach into hatchery-reared or wild categories based on scale circuli.
• During the riverine stocking evaluation, 10% of captured fish were classified as hatchery-reared at 8 months post-stocking.
• At 18 months post-stocking, 7% of captured fish were identified as hatchery-reared.

Conclusions:

• Scale circuli patterns provide a reliable method for differentiating hatchery-reared from wild roach.
• The discriminant function is a valuable tool for assessing the contribution of stocked fish in riverine environments.
• The study demonstrates the utility of scale analysis in fisheries management and stocking program evaluations.