Rivers are among the most anthropogenically affected ecosystems in the world by irrigation, transportation, channelizing, and hydropower. Habitat restorations have become a popular method to restore the heterogeneity and complexity of rivers aiming for improvement of biodiversity. In this master thesis, I studied the effects of restoration in a regulated and channelized river in the middle of Sweden. Differences in fish abundance and diversity together with hatching success and survival rate from egg to smolt of Seatrout (Salmo trutta) and Atlantic salmon (Salmo salar) were tested between restored and unrestored reaches. In addition, differences in abundance, biomass, diversity, and composition of benthic species between restored and unrestored areas were studied. The study design consisted of three restored and three unrestored locations where artificial spawning grounds (redds) were placed, electrofishing was conducted, and an inventory of abundance, biomass and diversity metrics of benthic fauna was performed. Whitlock-Vibert boxes were used in the artificial redds and were used to calculate hatching success. The inventory of benthic fauna consisted of kick-sampling and sampling of stones followed by identification and measuring of length in the lab. The findings in this study suggest that the survival of salmonids is not limited by the hatching success but that the lack of migration possibilities and the low survival rate from egg to smolt makes it unlikely with a successful reintroduction of Atlantic salmon and seatrout in Dalälven. Furthermore, one could argue that the habitat restorations have not increased the diversity of benthic fauna. However, it is possible that there is an ongoing shift in the benthic fauna towards a more diverse community in the restored areas and it is possible it will be more visible in a few years which supports maintaining long-term monitoring. Lastly, this study enlightens consequences with anthropogenically affected rivers and leaves opportunities for further studies.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-502002 |
| Date | January 2023 |
| Creators | Svärd, Ville |
| Publisher | Uppsala universitet, Institutionen för biologisk grundutbildning |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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