Stock collapse and its effect on species interactions: Cod and herring in the Norwegian‐Barents Seas system as an example

Abstract

At the stock level, the Norwegian Spring Spawning (NSS) herring (Clupea harengus) is a text book example of overexploitation of marine fish populations with a positive outcome. Due to overexploitation, the NSS herring stock collapsed in the 1960s from a biomass of more than 14 million tonnes in 1956 to less than 0.1 million tonnes in 1972 (Toresen & Østvedt, 2000), but is now counted as one of the largest herring stocks in the world (Engelhard & Heino, 2004). At the species level, the Atlantic cod (Gadus morhua) is a prime example for the overexploitation of marine fish populations (Sguotti et al., 2019), with the Northern cod collapse in the early 1990s being a major

Empirical evidence of nonlinearity in bottom up effect in a marine predator–prey system

“…In particular, we find empirical evidence for nonlinear change in species interaction ( table 2 ) directly linked to prey abundance change. Non-additive population dynamics has been previously described for many species, notably for cod due to this species data availability [ 11 , 34 ] but seldom addressing interaction with another species [ 12 , 13 ].…”

“…However, our model does not take into account the spatial overlap of the two species that affects their interaction [ 42 ] neither the effect of the potential interaction with other species of the system (e.g. haddock Melanogrammus aeglefinus [ 12 ], herring [ 13 ], Polar cod Boreogadus saida [ 43 ]). These lacking processes are however partially taken into account by the process error in the model formulation [ 15 ] (see electronic supplementary material, figure S5).…”

“…threshold) on population dynamics in terrestrial [4,5] and marine [6][7][8][9][10] systems alike resulting in different population equilibrium and dynamics [4]. Marine systems are prone to nonlinear transitions under climate warming [1] and overfishing [11] that may also lead to altered population dynamics [12,13]. A prime example of such nonlinear transition is the Atlantic cod [10,11,14].…”

“…Both species are known to interact in the BS and affect each other's population [18]. Indeed, predation by NEA cod on BS capelin is thought to have delayed the capelin stock's recovery after its collapses [13]. In addition, BS capelin is considered to be the main food for NEA cod [19,20] and low capelin stock was blamed for the very low cod catches at the end of 1980s [21].…”

Fishy windows to an Arctic city: Urban (in)visibilities of global fisheries in Tromsø

“…In general, fish stocks in the Barents Sea have been referred to as some of the best-managed stocks in the world. The Northeast Arctic cod stock is often compared with the fatal stock collapse of the Northwest Atlantic cod in the early 1990s, which was considered a failure of sufficient regulation and management (Harris, 1998;Durant, Aarvold, & Langangen, 2021). In northern Norway, a particular characteristic of the framing of sustainable fisheries is the decades-long bilateral cooperation with Russia (and the former Soviet Union).…”