Lake Constance #GAP2exchange: A team of scientists, fishers, and policy managers from GAP2′s Lake Vättern case study in Sweden traveled to Lake Constance to see what can come out of mutual knowledge-sharing for lake fisheries.
Each evening the exchange team undertook a ‘reflection hour’ – providing us with a wealth of insight into how these two fisheries function. Read on for all the details…
Lake Vättern reflections
We ended each day with a “reflection hour” where participants discussed what they had
encountered during that day. Each person had to list their most memorable experience of the day. Here are the four main themes that were selected for more intense discussions:
- What is a fisherman?
- How to deal with invasive species?
- Management of a lake governed by so many states/nations? Which are the conflicts? Which are the pitfalls?
- The view on nature and restoration of habitat.
Other topics that were raised (listed in order of time spent discussing them)
- Most stocking in Lake Vättern was terminated in 1979 but was criticized and scaled down already in 1944. In Lake Constance throughout the 60’s and 70’s, stocking was used to mitigate the negative effects of eutrophication on fish reproduction. The program has been in place since then and comprises six different fish species. Over 100 million young whitefish are released annually in Lake Constance, an impressive figure. We spent a lot of time discussing this management system. One thing we missed (even though we asked for it) was an assessment of the success of the stocking and an assessment of long-term consequences for the stocks. Later P. Hirsch gave us a paper (by R. Eckmann, 2012) about this latter issue was the assessment from some years ago.
- The collaboration among countries and states! Three countries, two German states, two Swiss kantons and one Austrian state seem to be able to collaborate in the management of the lake. The system has some (actually many!!) similarities with the EU’s CFP (Common Fishery Policy). An expert group (equivalent to ICES!) gives advice to politicians from all the countries that make the decisions. Stakeholders have a hard time influencing these decisions (well, thats our interpretation…). One potential problem when running this form of management is that one of the countries (Switzerland) is not a member state in the EU.
- No answer to questions about toxins and dioxins in fish. How come? Later we found out that they had some minor measurements conducted and apparently levels of dioxins and PCB’s are below the EU threshold for human consumption.
- Very nice and detailed statistics on fisheries catches (both commercial and recreational), they put it together by using local fishing clubs and associations. And it’s mandatory for all fishermen to report their catch!
- 85% of the Meichle family’s income comes from selling directly to restaurants and wine-testing events etc.. 10% comes from selling fish in their local store (people pick fish from the freezer/fridge and leave cash in a can) and 5% from selling to grocery stores. This strategy gives them a good price for their fish compared to fishermen only selling to fish auctions or distributors.
- The fisheries are managed mainly through controlling the time of fishing and the mesh size used. Fishermen are only allowed to fish in the spawning season if they help culture stations to get stocking material. They are allowed to keep the fish after carefully collecting the eggs.
- Impressive fish and environmental monitoring programs, up to ten times more intensive than in Lake Vättern!
- The fishing pressure is much higher than in Lake Vättern. There could be a risk of overexploitation when the lake becomes oligotrophic but this also seems to be partly compensated due to better growth and recruitment and weaker competitive interactions among species due to fishing.
- So many introduced species and they don’t seem to take it that seriously?
- All fishermen must pay a license that finances stocking and monitoring. Around 6-8.00 euros for commercial fishermen and around 100 euros for recreational fishermen (this is an annual fee). The money goes to stocking, habitat restoration, fisheries control and monitoring.
- The culture stations we visited appeared to be in very nice shape. Our main impression was that they were clean and organised. Some of the participants had prior experience from working in fish culture stations and they were very impressed by the state of these facilities.
- What about the rivers? They are working on the restoration of the habitat but to what extent? In Lake Vättern restoration of river habitat is one of the main management efforts with very high priority!
- We agreed that they are doing a great job of combining fisheries, tourism and culture.
- The number of commercial fishermen on the Upper See (the big basin) is decreasing but not so much in the minor basin (Unter See). There are 112 people in Upper See at the moment, with 12.674 individual recreational fishermen/fishing licenses (they knew the exact number!). The fisheries expert group want the number of commercial fishermen to be lowered down to around 60-80 fishermen, partly by using some kind of retirement fund. So far this has not been agreed upon by the politicians in the IBKF. The mean age of commercial fishermen is relatively high (similar to Lake Vättern), many are over 50 years old.
- They used to have at least four “species” of whitefish. One of them was deep-spawning (Kilch) but this variety seems to have become extinct due to the low oxygen levels occurring throughout the eutrophicated period. This is very interesting given that we have this very peculiar form also in Lake Vättern. Nowadays they mainly fish on the two pelagic varieties (Blaufelchen and Gangfisch).
- Recreational fishermen need to have a fishing license that they get after taking a course in fishing. Nice system!
- They are ambitious…and really make an effort! Fisherman Zeth Rylander emphasizes German/Swiss/Austrian thoroughness!
- The studies on the foraging effects of over-wintering birds were very interesting (in some areas over 90 % of the mussel populations are depleted in winter). Similarly, Lake Vättern is rarely covered by ice, even though most surrounding lakes and coastal waters are. Thus we could have the same phenomenon with significant foraging of birds (and not only during nesting periods). Fishermen argue that cormorant predation of fish in spring and autumn should be particularly and better investigated.
- Oligotrophication is a phenomenon that we also have in Lake Vättern – it will inevitably lead to lower productivity. How will this influence the fishery in the long run?
- Commercial fishermen have three years education through a certain fishing school. This is something we could perhaps learn from?
- They have non-native crayfish, and soon probably signal crayfish all over the lake. But they have a very little crayfish eating culture and crayfish are thus not explored commercially. Apparently they used to have a similar culture of crayfish eating as in Sweden but it disappeared in the early 1900s.
- The amplitude in water level was 2 m (maximum). How is this managed and how does it influence the fish and crayfish?
- Perhaps some presentations were too advanced to suit all our participants but some of these problems could be addressed during our reflection hours.
- There is, similar to Lake Vättern, a small population of grayling. They are apparently close to extinction. First due to cormorant predation and then from the extreme summer temperatures in 2003. Some graylings were “saved” and put temporally in cold water ponds and were later released back into the lake.
- Nowadays, all of Lake Constance is considered as public water. All the fishermen can fish everywhere in the lake independent of which country they are from, except for the shallow parts that are exclusive to that countries fishermen (up to 25 m depth). In the 19th century however monks owned part of the water exclusively and the city of Konstanz owned other parts.
- Another similarity to Lake Vättern is the Arctic charr population. It is stocked and the catches have increased considerably these last years (they are now 16 tonnes in total).
- The recreational fisheries are smaller than the commercial fisheries in relation to their landings (50 compared to 465 tonnes). In Lake Vättern it’s the opposite for many species.
- Scientists are obliged to sell their catch! This fact explained some peculiar equipment in their labs (salt, pepper, herbs, fish filleting machines etc).
- Common carp was reproducing in the lake on an irregular basis. Last year’s warm summers had been very beneficial for the species (and for catfish). This felt a bit strange to us, in our areas common carp normally have problems to establish in larger lakes, particularly since they are sensitive to predation during their juvenile phases. But perhaps due to a combination of climate change and low predation rate they can sustain themselves in Lake Constance?
Follow this exciting exchange trip on:
In Swedish on www.slu.se