How do Boat Induced Waves Affect Göta älv and the Atlantic Sturgeon?
Several vessels navigate the Göta River daily, and the wake waves from larger ships can damage, impact, or displace the benthic fauna and fish eggs in the river.
This, in turn, reduces their survival chances, as well as those of fish species such as the newly introduced Atlantic sturgeon (Acipenser oxyrinchus), which feeds on benthic invertebrates during its juvenile stage (Näslund et al., n.d.). Additionally, the waves from ships erode shallow shoreline habitats, altering fish habitats and affecting species with specific requirements for spawning and nursery areas. Lithophilic fish species are particularly sensitive to high-frequency wake waves (Zajicek & Wolter, 2019).
Boat-induced wake waves also increase the detachment of benthic invertebrates from substrates, particularly in simpler habitats with low structural complexity. Studies have also shown that the long-term effects of boat traffic waves lead to reduced biodiversity and changes in the food web (Gabel, 2012).
During the summer of 2024, 95 individuals of Atlantic sturgeon were released into the Göta River as part of the Sportfiskarna project Störens återkomst. This species had been extinct in the river for over 100 years due to overfishing, but with the approval of the County Administrative Board, juvenile individuals from the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) in Berlin were reintroduced into the river (Sportfiskarna, 2023).
However, the Atlantic sturgeon now faces additional challenges, such as limited food availability in the river, which may be influenced by the impact of ship wakes. Surveys have also noted very low populations of pike eggs in the Göta and Nordre Rivers. Only three pike eggs were found in the Göta River and 12 in the Nordre River during the 2021 survey (Sportfiskarna, 2021). This may be due to the wake waves from pilot boats destroying their spawning areas (Sportfiskarna, 2021).
This master thesis has just started and aims to carefully map and analyze the river area from Jordfallsbron to Lilla Edet. The goal is to identify locations where waves have the greatest negative impact on organisms or where the physical force of the waves is strongest. This will provide a better opportunity to protect the Atlantic sturgeon, benthic fauna, and fish eggs more sustainably, for example, through speed restrictions or wake protection measures.
Written by Erik Fransson, Master’s student with the SEG.
Erik is currently a second-year master’s student in marine biology at the Department of marine science at the University of Gothenburg. Currently, under the supervision of Johan Höjesjö and Linnéa Jägrud in the cooperation of Sportfiskarna, he is undertaking his master’s thesis, which focuses on the effects and mapping of ship-induced waves on benthic fauna and fish eggs in göta älv with a focus on the Atlantic sturgeon. The purpose of this study is to investigate the effects of ship-induced waves from larger vessels in the Göta River and how they impact the benthic fauna (primarily invertebrates), fish eggs (primarily pike eggs), and how this in turn affects fish in the Göta River, with a focus on the Atlantic sturgeon. The aim is also to identify which areas in the channel need speed restrictions or other forms of protection (for example, longitudinal barriers or other types of wave protection).