Tipping point realized in cod fishery

Abstract

Understanding tipping point dynamics in harvested ecosystems is of crucial importance for sustainable resource management because ignoring their existence imperils social-ecological systems that depend on them. Fisheries collapses provide the best known examples for realizing tipping points with catastrophic ecological, economic and social consequences. However, present-day fisheries management systems still largely ignore the potential of their resources to exhibit such abrupt changes towards irreversible low productive states. Using a combination of statistical changepoint analysis and stochastic cusp modelling, here we show that Western Baltic cod is beyond such a tipping point caused by unsustainable exploitation levels that failed to account for changing environmental conditions. Furthermore, climate change stabilizes a novel and likely irreversible low productivity state of this fish stock that is not adapted to a fast warming environment. We hence argue that ignorance of non-linear resource dynamics has caused the demise of an economically and culturally important social-ecological system which calls for better adaptation of fisheries systems to climate change.

Climate change or mismanagement?

“…Notably, the other commercial species in the area have very similar life history traits suggesting similar resilience against stress caused by climate change or fishing. The study concludes that severe, sustained overfishing plus inappropriate size selectivity of the main fishing gears have caused the decline in spawning stock biomass of cod and herring to levels that are known to effects of overfishing (Pörtner and Peck 2010;Bodini et al 2018;Free et al 2019;Möllmann et al 2021). Some studies (Hare et al 2016;Spencer et al, 2019) argue that climate vulnerability assessments need to be conducted as part of a future fisheries management framework.…”

Temporal and spatial changes in benthic invertebrate trophic networks along a taxonomic richness gradient

“…Most bottom trawling occurs in the Skagerrak and Bornholm Basin for demersal fish species (mostly cod Gadus morhua ; ICES, 2019 ), although there is a prawn fishery ( Pandalus borealis ) in the Skagerrak, but this species was not present in our dataset (Linders et al, 2018 ). Around 80 to 100% of the seabed is effected by bottom trawling in the Skagerrak and Bornholm Basin (HELCOM, 2018a ), despite declines in cod catch per unit effort since the peak in the 1980s (Möllmann et al, 2021 ). In addition to physical disturbance, bottom trawling can also resuspend contaminants, and large stores of persistent organic pollutants exist in the soft sediments of the Baltic Sea (Jonsson, 2000 ).…”

The ‘Cod-Multiple’: Modes of Existence of Fish, Science and People

“…As to the present state, it seems that a kind of endless and rather unsuccessful loop has developed over the recent decade that is calling for integrated action more than ever. Top-down EU fisheries management has contributed to overfishing (and stock depletion), in which fishing pressures (e.g., catch quota) have been too high and predictions have been false due to model uncertainty and environmental change [39]. This resulted in a lack in trust among fishers, politicians and scientists.…”

“…Western Baltic (WB) cod (Gadus morhua) is one of these fish (stocks) that is politically regulated, scientifically researched, commercially marketed and socially contested. Because of its depleted stock status, this fish stock is presently of special concern and debate among fishers, scientists, environmental conservationists and politicians [39]. WB cod is ecologically important as a top-predator in local food web dynamics [40] but is also an economic asset (e.g., for jobs or tourist facilities such as fish restaurants) for coastal areas in Germany [41].…”