Unexpected fish and squid in the central Arctic deep scattering layer.

Area of Science:

• Marine Biology
• Arctic Oceanography
• Fisheries Science

Background:

• Retreating Arctic ice cover prompts interest in potential fisheries.
• The Central Arctic Ocean (CAO) ecosystem remains largely unexplored regarding fish stocks.

Purpose of the Study:

• To investigate the existence of harvestable fish stocks in the CAO.
• To document the composition and characteristics of deep scattering layers (DSLs) in the region.

Main Methods:

• A 3170-kilometer transect was conducted across the Eurasian Basin of the CAO.
• A deep scattering layer (DSL) was documented in the Atlantic water layer (100-500m depth).
• Zooplankton, small fish, Atlantic cod, lanternfish, armhook squid, and ice cod were identified within the DSL.

Main Results:

• An extensive DSL containing zooplankton and small fish was observed.
• Diel vertical migration was absent in the DSL for most of the year due to lack of light variation.
• Low abundances of Atlantic cod, originating from Norwegian spawning grounds, were found, having resided in Arctic waters for up to 6 years.

Conclusions:

• The observed fish abundance is significantly below commercially sustainable levels.
• Low ecosystem productivity in the CAO is expected to limit future fish stock development.
• The potential for substantial Arctic fisheries remains limited despite changing ice conditions.