Since the 80s, The Swedish University of Agricultural Sciences (SLU), the University of Gothenburg and the Swedish Museum of Natural History have monitored fish health, population status and contaminant levels in fish along the Swedish coast. Results from four reference areas have now been released.
The reports present results from Torhamn (Southern Baltic Proper), Kvädöfjärden (Baltic Proper), Holmöarna (Bothnian Sea), and Fjällbacka (Skagerrak).
– The evironmental monitoring we conduct is part of a globally unique programme for integrated coastal fish surveillance. The aim of the programme is to track how large-scale environmental changes and contaminants affect fish health and population development, says Jens Olsson, researcher at the Department of Aquatic Resources at SLU and one of the report authors.
Catches of whitefish and roach are increasing in Holmöarna and Kvädöfjärden. In Kvädöfjärden and Torhamn, herring (Baltic herring) catches are also rising. At the same time, pike catches are declining in the same areas along the Baltic sea coast.
For the key species perch, trends differ between areas, but a common pattern is that perch grow quickly in all areas, and the individuals caught in recent years are significantly younger compared to those caught when the monitoring started. In the Skagerrak, catches of round goby are increasing, while cod and plaice are declining.
– It is encouraging that important species like whitefish and herring are increasing and that perch are growing well, but at the same time it is concerning that pike continues to decline and that roach is increasing so sharply in two of the areas. Where the older perch have gone is still a mystery, says Jens Olsson.
The health status of perch and viviparous eelpout in the Baltic Sea has improved somewhat over time, but on the west coast the health of viviparous eelpout is clearly affected, with no clear signs of improvement.
– It is of course positive to see that the previous negative trend in the health of perch and viviparous eelpout in the Baltic Sea has slowed down somewhat. At the same time, the results show that the health of both species is still affected, and in the west coast area the health of viviparous eelpout is clearly deteriorated – likely due to exposure to chemical substances, says Professor Lars Förlin at the University of Gothenburg, who has led the fish health studies.
In general, contaminant levels in fish have also decreased, but PFOS is increasing in one area, and mercury is still found at high levels in some species.
It is concerning that mercury levels are still high and that PFOS is increasing in perch in Kvädöfjärden. The mercury likely comes from existing environmental sources, while PFOS indicates new emissions. We also see clear effects of bans on several pollutants that previously occurred at high concentrations in fish, as the levels of these have decreased dramatically, says Suzanne Faxneld, curator at the Swedish Museum of Natural History and responsible for the contaminant analyses.
Together, the researchers emphasise the importance of long-term environmental monitoring
– The results show how crucial long-term environmental monitoring and funding are to understanding how the environment is affected by eutrophication, climate change and pollutants – and how nature responds to our measures. In short: without monitoring, we have no understanding, says Jens Olsson.
The national integrated coastal fish monitoring is conducted by SLU (fish stocks), the University of Gothenburg (fish health), and the Swedish Museum of Natural History (environmental toxins), and is funded by the Swedish Agency for Marine and Water Management. Raw data on fish stocks and fish health is stored in the KUL database. Results are published, among other formats, as fact sheets in SLU Aqua’s report series.
Jens Olsson, Researcher
Department of Aquatic Resources, Institute of Coastal Research, SLU
jens.olsson@slu.se, +46 10 478 41 44