Abstract

The asp is on the 1996 IUCN:s Red List of Threatened Animals. In the Swedish Red List it is ranked as vulnerable. This species should be preserved in Europe as proposed in the Council of European Union Habitat Directive and Bern Convention on European Wildlife and Habitats. The asp is a relict from the Baltic Sea ancylus stadium. It originates from Southeast Europe. In Sweden it occurs from the lower Dalälven and south to mainly the large lakes Hjälmaren, Mälaren and Vänern and their inflows. The asp is a large cyprinid and as adult it is a predator. This study is a part of the Swedish National Board of Fisheries project to get an overview about the asp spawning places in Sweden. The purpose of this study is to document available knowledge about asp reproduction and potential spawning grounds in the large Swedish lakes, Hjälmaren and Mälaren, investigate a few selected potential spawning grounds and produce more knowledge about spawning grounds in these lakes. To be able to compare spawning grounds in streams and lakes, a pilot study was carried out in Oxundaån, running water that has its outflow into Mälaren just northwest of Stockholm. Review of literature, interviews with professional fishermen and mapping of selected potential spawning grounds was performed. The investigated grounds in the lakes were, in the fishermen’s childhood, well known as asp fishing areas during the spawning period. Fishermen tell that they get asp as an unwanted catch near the investigated grounds. In the end of the 1960´s brood asp were caught near the little island Fagerön. For most fishermen asp is an unwanted catch without commercial value and is often released back into the lake. This study has however not proven that asps still are spawning on the investigated grounds. The ground substratums of the investigated potential spawning grounds are dominated by sand interspersed with gravel and some stone. The soil types are ice river stratum (frequently boulder ridge) and moraine. The ground substratum had no aquatic plants with the exception of algae. The water was relatively clear without colour. The potential spawning grounds were found in straits, near small islands, visible stones and on spits just past the point where they enter the water. Experience shows that these spawning grounds are exposed to wind and currents. Information from fishermen is of high value in searching for possible spawning grounds. Soil type maps, nautical charts and topographical maps are god complements to finding spawning grounds

Published in

Publisher: Vattenbruksinstitutionen, SLU

SLU Authors

• Lundqvist, Hans

  • Department of Aquaculture, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use
Fish and Aquacultural Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/2847