Fish stock discrimination using image analysis
Fish stocking is one of the most widespread and frequent management strategies in freshwater systems. However, the contribution of stocked fish to the population is seldom investigated, and hence the effectiveness of this strategy is virtually unknown for many populations. Understanding the contribution of stocked fish into the population is crucial because it allows the disentanglement of the confounding effects generated by stocked fish into the estimation of survival and growth rates of the population.
Figure above: Pikeperch (Sander lucioperca) individual in its natural habitat (Photo: Jiři Peterka).
Using sophisticated image analysis and machine learning techniques on the pikeperch (Sander lucioperca) otoliths (inner ear stones) we were able to identify the origin of the fish in Lipno Reservoir. Our results highlights that the detection of the natal origin of fish based on their otolith shape is promising and the application of this method can provide a low cost and effective tool for managers to assess the efficiency of the stocking regime in their systems.
Pikeperch (Sander lucioperca) sagittae otolith (inner ear bone) used to discriminate the origin of the fish in Lipno Reservoir (Czechia).
Mean shape of the sagittae otolith from stocked (top left corner) and wild (bottom left corner) pikeperch (Sander lucioperca). Differences in the otolith average shape of stocked and wild pikeperch (right side) is expressed in color heatmap scale (small difference = light yellow, high difference = dark red).
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Souza A.T., Soukalová, K., Děd, V., Šmejkal, M., Moraes, K., Říha, M., Muška, M., Frouzová, J., Kubečka, J. 2020 Otolith shape variations between artificially stocked and autochthonous pikeperch (Sander lucioperca). Fisheries Research, 231, November 2020, 105708. https://doi.org/10.1016/j.fishres.2020.105708