This report describes the ecological effects of fishing closures (no-take areas) in Swedish marine and coastal waters. In 2005 the Swedish Board of Fisheries (now the Swedish Agency for Marine and Water Management) was commissioned by the government to establish a number of areas where all fishing was prohibited and to evaluate the effects of these closures. Five such no-take areas were established in 2009-2011. The effects on fish populations, and in some cases also on other components of the ecosystem, were monitored until 2015. This report gives a summary of biological effects of these no-take areas, focusing on fish populations and ecosystems.
When these five new fishing closures had been established in 2011, the total area of no-take areas in Swedish marine and coastal waters amounted to 1 200 km2. This corresponds to less than 1 % of the Swedish sea area, but two thirds of the total areal extent of no-take areas in Europe. Hence, the monitoring and evaluation of the Swedish areas makes an important contribution also to the general knowledge base regarding no-take areas for European fisheries management.
The geographical areas and target species of the evaluation were:
• European whitefish in the Bothnian Sea
• Pikeperch, pike and perch in the Stockholm archipelago, central Baltic Sea
• Cod in the Kattegat
• European lobster and predatory fish in the Gothenburg archipelago, Skagerrak
• Cod, turbot and plaice in the Swedish fjords of Skagerrak
More detailed results for each of the study areas are given in supplementary reports, whereas overall results are synthesized here. Abundance and body size of target species increased in most of the no-take areas, as compared to nearby reference areas where fishing was continued. The results show that the earlier fishing pressure in the no-take areas had been large enough to influence both fish abundance and size structure. The responses in abundance and body size were seen both for populations that had been targeted primarily by commercial fisheries, such as cod in Kattegat, and for coastal species where recreational fisheries dominated the catches, for example whitefish in the Bothnian Sea, pikeperch in Stockholm archipelago and European lobster in the Gothenburg archipelago. Despite the relatively short evaluation period of 5 years, substantial positive effects on the populations were evident in four of the five no-take areas, illustrating the utility of no-take areas for strengthening vulnerable fish populations. In one area, Havstensfjorden in Skagerrak, no positive effects have so far been seen in the target species cod, plaice and turbot. This is most probably explained by previous recruitment overfishing on local populations, leading to slow recovery.
In addition to the studies on target fish populations, effects on fish communities and benthic fauna were studied in some of the areas, showing changes also in these ecosystem components. These observations were likely due to a combination of direct effects of excluding fisheries on target and bycatch species, and indirect effects of the increase in large predatory fish and European lobster leading to increased predation on prey species. Thus, the studies suggest that no-take areas may contribute to re-establishment of ecosystem functions by increasing the abundances of large predators. Such changes in food web function may also counterbalance other processes, such as the increased production of fast-growing algae in eutrophicated areas, through trophic cascades. Another effect of no-take areas is the cessation of bottom trawling leading to improved conditions for benthic fauna sensitive to physical disturbance.
In most cases, the introduction of the no-take areas has likely decreased the total fishing effort rather than displacing it to adjacent areas. In the Kattegat no-take area, however, the purpose was explicitly to displace an unselective coastal mixed bottom-trawl fishery targeting Norway lobster and flatfish to areas where the bycatches of mature cod were smaller. The mixed fishery has continued in the buffer zones and the open areas of Kattegat, and total catches of Norway lobster and flatfish have been maintained but with substantially less bycatches of adult cod than before the introduction of the measures.
The report also reviews the general scientific knowledge base on no-take areas, including also experiences from previously studied no-take areas in Swedish waters. The effects observed in these other Swedish no-take areas are consistent with the ones reported here, showing increases in population sizes and size structures, and an increase in the reproduction potential. The results also generally agree with international studies in terms of the effects no-take areas on target species for fisheries. The Swedish examples generally lack specific empirical studies on ecosystem effects of the closures. However, knowledge on the effects of large predatory fish on ecosystem functioning, including their role in trophic cascades, is available from other research projects in Sweden.
As the population density and body size of fish and lobsters increase, the reproduction potential also increases, which may generate positive effects also outside the closed areas through spillover. The magnitude of such spillover effects, through export of eggs and larvae and migration of adult fish, are however not easily estimated. Apart from spillover effects, there are also other potential benefits from no-take areas. By keeping a part of the fish populations protected from fishing, the risk for stock collapse due to otherwise inadequate management decreases, whereby the no-take areas may act as an insurance policy. No-take areas may also counteract genetic impoverishment due to selective fishing on large, fast-growing individuals, and may hence mitigate a decrease in fish productivity due to genetic effects, and may support biological variation and resilience against environmental change. In the present evaluation, the net effects were quantified for the Kattegat no-take area, showing a positive effect on the cod population in the Kattegat management area as a whole, while catches of other commercial species had not decreased. In a longer-term perspective, the recovery will likely provide increased opportunities for a cod fishery, as a substantial part of the population is found outside of the no-take area after the spawning period.
No-take areas can, if they are adequately designed, give rise to positive population effects and may be a useful complement to other fisheries management instruments. In many cases, the desired results can potentially also be achieved by a combination of other measures, such as gear or catch restrictions in space and time. The experiences from the current evaluation show that no-take areas can be an important tool for fisheries management especially for mixed fisheries and local coastal fish populations, as well as in cases where there is a need to counteract adverse ecosystem effects of fishing. Marine protected areas where the protection of both fish and their habitats is combined may be an important instrument for ecosystem-based management. In this context, no-take areas are also needed as reference for marine environmental management, as well as for understanding of the effects of fishing on fish populations and ecosystems in relation to other pressures.