From small bycatch to main commercial species: Explosion of stocks of rock cod Patagonotothen ramsayi (Regan) in the Southwest Atlantic

The Patagonian Shelf ecosystem is considered to be a wasp-waist ecosystem controlled by medium-sized planktivores Patagonian squid Doryteuthis gahi, rock cod Patagonotothen ramsayi, and southern blue whiting Micromesistius australis. After the collapse of southern blue whiting stocks in 2004–2007, its role was overtaken by rock cod, which exhibited a 20–30 fold increase in catches and CPUEs. P. ramsayi is an important food source for all predatory fish; representing about half of the food consumption in hakes, toothfish, kingclip, and some skates. Its importance increases with increasing size of predator with rock cod gradually substituting a similar-sized squid. The explosion of rock cod abundance coincided with an increase of seasonal immigrants preying on this species (hakes and kingclip) that may have changed their migratory timing and patterns for better use of this food resource.