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Changing tides for fisheries: how adaptation can help keep seas bountiful in an uncertain future


As fish are starting to adapt to their changing habitats, what is the impact on the industry?

Melanie Brown has been fishing for sockeye salmon in Alaska’s Bristol Bay for the last 40 years. The world’s biggest run of wild sockeye salmon is here, with catches in the last year came in at around 60 million fish. But last year, during Alaska’s hottest summer on record, Melanie and fellow fishermen saw heat-exhausted salmon flowing lifeless downstream without spawning. “In three years or so, we will know how much impact that heat wave had on that generation of sockeye,” Brown says. 
 “The warmer temperatures last summer caused the salmon to wait and pool outside the river district where I fish to wait for cooler temperatures,” says Brown about the situation in Alaska. “When they couldn’t wait any longer, they surged into the river on the rising tide in the deep river channel where the water is cooler. When this happens, people with set net sites like me have fewer opportunities to catch salmon that would normally hug the shoreline,” Brown explains.

Across the world, fishermen and scientists are seeing fish stocks reacting to changes in their habitats, with climate change increasingly mentioned as a factor shaping new realities underwater. Knowing how much climate change is responsible for these realities remains challenging, but the discourse on adaptation is on the rise.

Heat and acidification: changing waters impacting fish stocks

Scientists are confirming that fish populations in the north-east Atlantic are moving to higher latitudes. Warming waters push the fish that depend on a certain temperature range to search for colder waters. Fishermen on the UK’s southern coasts have a hard time catching cod, which spawns best only in waters between 0 to 6° C. “There has definitely been a change in species in the North Sea,” says Elizabeth Bourke, policy officer for the UK’s National Federation of Fishermen’s Organisations (NFFO).

While cod’s territory has contracted, species like anchovies, horse mackerel, and sole, have shifted north into the warmer waters of the North Sea, the Baltic and west Scotland, research from ClimeFish, European Union project, shows. Over the last 30 years, 19 Atlantic commercial species have undergone some distribution shifts in European waters, according to ClimeFish.

“Heatwaves have particularly affected tropical regions, with fish migrating to the north of the Atlantic and the Pacific,” Dr. Nieuwenhuis, the Marine Stewardship Council (MSC) director for Northern Europe explains. “Predictions say these regions could see their seafood catches decline by up to 40 percent by 2050.”

Source: Copernicus Climate Change Service / Plymouth Marine Laboratory.

“You need to understand essential environmental variables that regulate fish basic physiology, such as temperature, pH, and salinity, as well as how much food they have available, in order to understand how wild fish populations respond to climate change, thus, how their life-cycles and growth are affected,” says Dr. Ana Queiros, Senior Scientist at the Plymouth Marine Laboratory. “There is a clear movement north and into deeper areas of cold water species […] away from areas where fishing activity is concentrated, as we enter the next three decades,” says Dr. Ana Queiros, who is working with the Copernicus Climate Change Service (C3S) on providing climate data for fisheries’ management.

Traditional northern species struggle to adapt

“It’s recognised that large-size species that mature slowly, produce fewer eggs, and prefer a certain type of habitat tend to be more sensitive to climate change,” says Dr. Martin Lindegren, senior researcher at the Technical University of Denmark. “So, if we were to generalise, many of the larger commercially important species are more vulnerable compared to small, opportunistic species that are more adaptive, such as sardines, anchovies, or sprat.”

Fishermen in the UK are seeing some species shrinking. “Fish mature later in colder waters,” Dr. Elizabeth Bourke, policy officer for the UK’s National Federation of Fishermen’s Organisations (NFFO) says. “Quite often they seem to mature about half a year to a year earlier, depending on the species. This increases pressure on the stock,” Bourke adds. The same trend is observed in Alaska. Alaskan fishermen are also catching smaller salmon. Lifelong local fisherman Eugene Anderson agrees: “in the past 7 years, the average weight of a sockeye has gone from 3.5 kg to as low as 2.3 kg. This has been matching the rise in sea surface temperature in the Gulf of Alaska.”

Warming has been good news for other species. Bluefish and other exotic species have found new habitats in the north-western Mediterranean and in the Atlantic Ocean. British fishermen hardly find sole on the southern coasts, but seabass has come in, says Bourke. Warmer water species like common sole, boarfish, and john dory are becoming more prominent in catch and could become more important resources to Europe, according to Dr. Queiros.

Helping fisheries by monitoring fish stocks changes

“Informing fisheries’ adaptation is about understanding whether fishing activity levels needs to be adjusted in certain areas to allow populations under climate pressures to remain viable,” says Dr. Queiros, as well as “indicating where fish may redistribute to so support more fishing in those areas.”

Source: Copernicus Marine Environment Monitoring Service

Providing climate data to fisheries’ managers, authorities and small fishermen is becoming central to adaptation efforts, as well as for avoiding overexploiting stocks. The Copernicus Climate Change Service (C3S) has been working with the Plymouth Marine Laboratory to identify what data do governments and the fishing industry need; they have developed a set of detailed climate impact indicators for fish stocks, to suggest how species’ growth, life-cycle, distribution and productivity might change in the future. Overlapping the data with fish habitat requirements and migration patterns can help predict how stocks will behave under future climate change.

“Many of the adaptation measures would be or can be very similar to current measures to make fisheries more sustainable, such as planning protected areas using climate change projections,” says Dr. Jose Antonio Fernandez, senior researcher in sustainable fisheries management at AZTI. “These approaches require data, and the more data, the better.” Dr. Fernandez is exploring ways to reduce fuel consumption in fisheries, as part of the H2020 SUSTUNABLE project, starting this month. “But the project also has a novel approach to use fishing vessels as oceanographic data-gathering platforms.”

Fishing communities are already helping. Researchers from ISPRA, Italy, gathered local knowledge from Mediterranean fishermen on how species were moving across the basin – to find new data, but also to strengthen communities’ capacity to adapt. Spain’s CEPESCA, is embedding climate data into fishery assessment models to reduce uncertainty around species’ distribution. In Norway, the Vake/Catch application will use satellite data from Copernicus and catch statistics to help fisheries optimise quotas, as well as link sea temperatures to fish abundance and moving patterns.

Adaptation to migrating stocks has come in many forms. As cod stocks shifted in the North Sea, some of the UK’s inshore fleet switched to shellfish. “The offshore fleet was able to follow the stocks further.” Small fishermen don’t have as many options, having to combine fishing with other less-profitable activities, such as tourism”, says Bourke. But not relying on a single stock or source of income is seen as key for reducing vulnerability within the fishing industry, according to

Allowed to fish: what and where?

Many in the industry warn that if fish are on the move, permits that confine fishermen to catch a species over an area that might no longer host that species might become an obstacle to adaptation. Fisheries taking into account shifts in productivity and species’ habitats could be more profitable in the future, and also mitigate climate change effects, researchers from the University of Santa Barbara, California, show. Giving fishermen a portfolio of options will make them more resilient against losses if one stock is underperforming.

Dr. Nieuwenhuis, the Marine Stewardship Council (MSC) director for Northern Europe explains: “To remain sustainable, quotas need to follow scientific advice, moving with the fish stocks. Nations, including those in Europe, have struggled to agree on sustainable quotas for mackerel, herring, and blue whiting as these species move further north.” Having flexible and fair quota allocations between countries, adapted to climate-driven fish migrations could be part of the answer, according to Dr. Martin Lindegren, senior researcher at the Technical University of Denmark. “That would allow fishermen to take advantage of catching opportunities and markets.” More real-time climate information could also support adaptation. “It’s important to have data on shorter term changes that may have dramatic and immediate consequences. There is a need for access to rapid, direct early-warning systems providing forecasts on, for example, heat waves, harmful algae blooms or rapid spread of hypoxia – i.e. low-oxygen conditions.”