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Annual spawning migration of anadromous pike (Esox lucius L.) in streams entering the Baltic Sea
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Fish migration group)
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Fish migration group)ORCID iD: 0000-0003-0344-1939
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Fish migration group)
Danish Institute for Fisheries Research, Department of Inland Fisheries, Vejlsøvej 39,8600 Silkeborg, Denmark.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The movement of pike (n = 3415) was investigated in four streams entering the Baltic Sea in the Kalmar Sound

region, Sweden. Migration patterns were monitored during spawning in three of the streams and during the

whole year in the forth stream using passive integrated transponders and outer tags. The study was conducted

yearly between 2006 and 2010. Mature pike returned (22 – 45%) to the same streams year after year and some

fish returned to the same regions of the streams. No incidence of fish visiting another stream than the one

where they were marked was recorded and no fish missed the spawning season to return the next year. These

results indicated that the reason for fish not returning was due to mortality. The proportions of returning fish

indicated homing and the spawning ground fidelity (stream) was high. Return rates were influenced by size

of fish, sex and stream identity. We also investigated if sex, size or individual behaviour influenced timing of

arrival, departure or duration of stay in freshwater. Diurnal activity was examined in one year in each stream

suggesting activity peaks in the morning and evening. The results show that pike in the Baltic Sea are anadromous

and that the migration behavior is likely to create barriers for gene flow. The separation in populations

by spawning are similar to salmonid species and the management of pike in the Baltic Sea must consider this

process in strategies and plans of fishing.

National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:lnu:diva-13853OAI: oai:DiVA.org:lnu-13853DiVA: diva2:435947
Available from: 2011-08-22 Created: 2011-08-22 Last updated: 2016-11-09Bibliographically approved
In thesis
1. Anadromous Pike in the Baltic Sea
Open this publication in new window or tab >>Anadromous Pike in the Baltic Sea
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The pike (Esox lucius) is a major predator and top-down regulator in the Baltic Sea where it exists in two sympatric forms. One spawn in streams and rivers and the other one spawn in the sea. During the last decades, the habitats for both of these forms have developed in a negative way. In some freshwater systems, up to 90 % of the water areas have disappeared, mainly through drainage and straightening of watercourses for agricultural purposes. In the sea, reproduction habitats decrease due to construction of harbours and human activities that create disturbances. The perhaps largest single factor negatively affecting recruitment of pike in the sea is the eutrophication. Bottoms are overgrown with filamentous algae and shallow bays are covered with dense Phragmites belts decreasing the habitats suitable for spawning. Further on, a predator on egg and fish larvae, the three-spined stickleback (Gasterosteus aculeatus) has increased in abundance. It is difficult to restore and enhance pike production in the sea and probably the only economically viable alternative is to make restorations in freshwater. However, there is a limited knowledge about the freshwater spawning pike in the Baltic Sea. Thus in this thesis I, together with my coauthors, set out with an aim to increase the knowledge base regarding anadromous pike behaviour.

We found that pike of natal freshwater origin were common in the Baltic Sea. Through Sr:Ca studies in otoliths, about 45 % of the pike were interpreted to be of freshwater origin. The majority of the pike had emigrated out of freshwater at a length below 6 cm. These results indicate that freshwater recruitment is successful, contrasting the vast areas available for spawning in the sea. This creates incitements that restoration measures in these watercourses could have a significant effect on the pike population in the Baltic Sea.

Further, in four streams running out in the Baltic Sea, more than three thousand pike were marked to study spawning migration. About 30-40 % returned to the same river the subsequent year. Most of the pike used the lower parts of the stream for spawning. The homing of pike to a watercourse indicate that freshwater pike in the Baltic Sea consist of specific populations and this is crucial information when taking decisions on fish restoration measures.

Three wetlands adjacent to streams were restored for pike production. The most successful restoration involved minimal digging, with flooded grasslands providing optimal conditions for spawning. The first spawning season after restoration increased the pike production hundredfold.

In conclusion, the anadromous pike are numerous in the Baltic Sea. To compensate for the decline in pike populations in the sea, “pike-factories” created along the coastline are probably the most justifiable option.

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press, 2011. 110 p.
Series
Linnaeus University Dissertations, 61/2011
National Category
Ecology
Research subject
Natural Science
Identifiers
urn:nbn:se:lnu:diva-13856 (URN)978-91-86491-99-4 (ISBN)
Public defence
2011-09-16, Fullriggaren, Barlastgatan 11, Kalmar, 09:30 (Swedish)
Opponent
Supervisors
Available from: 2011-09-28 Created: 2011-08-22 Last updated: 2016-11-09Bibliographically approved

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