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The fate of 0+ asp (Leuciscus aspius) after being stocked in a reservoir


Artificial enhancement of fish populations by stocking is widespread practice. Yet, very little is known about short-term dispersal, capture efficiency and the effect of fish size and habitat suitability. Asp (Leuciscus aspius Linnaeus, 1758) was chosen as a model species, because of its protection in the Svihov Reservoir and common stocking to increase predator fish abundance in many biomanipulated waters. 0+ fluorescent-marked asp were stocked in dam, middle and tributary sites of Svihov Reservoir and subsequently monitored weekly for three weeks intervals by boat electrofishing for two consecutive years. Despite similar numbers of asp stocked, the recapture was six-times lower in a year with low water level and high macrophyte density. All captured asp were identified as of hatchery origin. In the dam site most asp were recaptured in or close to the semi-closed bay with shallow water, where they were stocked. In the middle site asp spread from the unsuitable site of stocking in all directions and only very few individuals were recaptured. In the tributary site, asp dispersion was the most evident in 2017 in the direction towards the dam in the littoral zone opposite the bank that was the bank of stocking. In comparison the highest recapture was found at the site of stocking in 2018. The recaptured asp were of similar or larger size than the average stocked asp, which may suggest size-dependent mortality. The mortality of stocked asp may be affected by failure in foraging and antipredator behaviour. This research highlights the importance of post-release monitoring.

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Thanks are given to J. Mareš, P. Michalička, Z. Prachař, M. Říha, K. Soukalová, L. Vetešník for assistance in the field and helpful suggestions during manuscript preparation, to L. Belfield for editing the English and to Vltava River Authority for enabling the fieldwork. This study was supported from ERDF/ESF project “Biomanipulation as a tool for improving water quality of dam reservoirs (No. CZ.02.1.01/0.0/0.0/16_025/0007417)“, by NAZV projects QK1920011” Methodology of predatory fish quantification in drinking-water reservoirs to optimize the management of aquatic ecosystems” and QK1920326 “Aquaculture of rheophilous fish”.

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Correspondence to Petr Blabolil.

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All applicable international, national and institutional guidelines for the care and use of animals were followed.

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Blabolil, P., Bartoň, D., Halačka, K. et al. The fate of 0+ asp (Leuciscus aspius) after being stocked in a reservoir. Biologia 75, 989–996 (2020).

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  • Dispersion
  • Fishery management
  • Hatchery production
  • Heavily modified water body
  • Sampling