More fishing traps in Gärsken, Alingsås

During June 2015 we were contracted by Länstryelsen to conduct a maritime archaeological survey of the southern end of lake Gärdsken, Alingsås. The city council plan to establish a pipeline from the southeastern shore several hundred meters northwest to the other side.

Previously in Gärdsken……..Previously we have conducted both a survey and preliminary investigation within the southern part of Gärdsken and its connecting tributary, Forsån. In 2009 we discovered in Forsån and its mouth a total of 13 fishing traps. In 2012 we were contracted to asses the extent and composition of the fishing traps within Forsåns mouth and delta. During this investigation we even discovered a perviously unrecorded trap; the most exciting and intact of the lot so far, it is registered in FMIS as Alingsås 281.

Alingsås 281Left: The perpidicular arm. Right: One of the catchment areas. Gainsford 2013

The above fishing trap and subsequent others located at the river mouth are commonly known in Sweden as ‘Katsa (plural Katsor)’. Katsor are stationary fishing traps that are constructed of a perpendicular arm from the shore out to deeper water  and one or more catchment areas. The arm and catchment areas are constructed av thin poles interwoven with thinner branches supported by larger piles or posts. The fish once in these catchments are unable to find their way out and can be easily fished up with nets or spear.

Katsa ClaessonClaesson 1937

In 2015 Alingsås kommun have plans to establish a waterpipe through the above mentioned area northwards. The planned route passes close to the shoreline for several hundered metres or so. This we believed was a prime area to find fishing traps. During our survey we located three small boat wrecks (modern; that is after 1850) and three new areas containing previously unknown fishing structures. Thusfar it is hard to say exactly what type of structures these areas represent; but in one instance it was possible to see a row of small poles that have probably been an arm.


Fishing traps are most probably one of the most common but also most under studied categories of archaeological sites. We will see, maybe there is the possibility for further investigations of the sites.


Claesson, E. 1937. ”Slå ut en katsa”. Ålderdomligt fiske i en Sörmlandsjö. I: Fataburen. Nordiska museets och Skansens årsbok 1937. Stockholm.

Gainsford, M. 2013. Fasta fisken i Forsån och Gärdsken. Arkeologisk förundersökning av Alingsås 264, 265, 266 & 267. Alingsås socken och kommun. Bohusläns museum rapport 2013:9. Uddevalla.