Marine fishes

What is happening and why does it matter?

• Northward range expansions are underway and pose unknown consequences for Arctic species and their interactions such as predation and competition.
• The ecologically important polar cod declined rapidly in the Barents Sea between 2004 and 2015, and is at a very low level, potentially due to predation from Atlantic cod, a more southern species that has expanded northwards. However, the 2016 survey showed an increase in abundance of young (one-year-old) polar cod for the first time in over a decade.
• Capelin stocks throughout the Arctic are shifting northward, but there is a strong variability: increases in recent years have been associated with warming trends, but declines have occurred in the Barents Sea and around Iceland.
• The northward expansion of capelin has led to changes in seabird diet in northern Hudson Bay. It also may affect marine mammals
• Greenland halibut have undergone declines and subsequent recoveries over the last two decades. Populations in the Barents Sea, Baffin Bay-Davis Strait are considered stable or increasing.
• There has been an overall decline in occurrence of Arctic fishes in the Barents Sea between 2004 and 2015.
• Increases in the relative abundance of warmer water species have already been documented in the Bering Sea, Barents Sea, Eastern Canadian Arctic, Greenlandic and Icelandic waters. Boreal species moving north seem to be negatively affecting the abundance of polar cod.

Why are marine fishes important?

• Pelagic and benthic fish species are important in Arctic marine ecosystems because they transfer energy to predators such as seabirds, marine mammals, and people.

What should you know about the monitoring data?

• A large number of species have been documented, but in many cases their distribution, abundance and relationships are largely unknown.
• Only a few species of commercial interest have been studied extensively. The most important of these covered by this report are capelin, polar cod and Greenland halibut.
• Indices and monitoring programs based on harvested species or that rely on fishery-related data are inherently affected by changes in stock size and exploitation rate, making them imperfect sources of information.

What are the most important drivers?

• Fishes are affected by environmental conditions such as sea ice extent and salinity, and are constrained by prey availability and predator pressure, which can be influenced by climate change.
• The main commercial marine fishes in the Arctic, Greenland halibut and capelin, do not yet seem to be adversely affected by climate change although their distributions appear to be changing. Northward advance of valuable boreal species, retreat of Arctic species and increased accessibility due to less ice cover will increase the total fishing pressure and open new areas for fishing in northern areas. Overfishing of target fish species is generally not of concern, as these fisheries are considered well managed.
• Little is known about effects on non-commercial marine fishes in the Arctic.

Where is monitoring happening?

• Monitoring is conducted on commercial fish species in the Barents Sea and the Norwegian Sea, which fall within the Atlantic Arctic Marine Area.

Advice for monitoring: marine fishes

• Conduct pan-Arctic taxonomic analyses to clarify zoogeographic patterns that are important for detecting and understanding change.
• Establish and conduct a monitoring plan that is independent of fisheries-related programs to assess changes in fish abundance and distributions. Use information from non-commercial fish species caught in groundfish surveys to provide a first step in this direction.
• Use information from TK holders for monitoring marine fishes.
• Connect monitoring initiatives across scales.
• Conduct laboratory studies to examine the possible effects of abiotic and biotic changes (e.g. temperature, salinity, acidity and diseases) on fish species
• Ensure that data on fisheries (commercial as well as artisanal) are accurate and registered in catch databases (such as the Food Agriculture Organisation of the United Nations). Information from logbooks is also relevant as it can be used to estimate the bycatch and the effects of fisheries.