Rapid ecosystem change after the cod collapse in Newfoundland & Labrador

Abstract

The cod collapse of Newfoundland and Labrador in the early 1990s was predicated by collapses of the key forage fish species in the region, capelin, and the wider groundfish community. After these collapses, rapid changes in ecosystem structure and function have been observed. From the early 2000s to mid 2010s, invertebrates dominated ecosystem biomass and the snow crab fishery became important to the region. During the late 2010s, invertebrates declined as groundfish stocks increased, although not to pre collapse levels. We developed two ecosystem models representing 1) the Grand Banks and 2) the Newfoundland and Labrador Shelf ecosystem structure and function for 2018-2020. We compared these models with existing ecosystem models that represent the combined Grand Banks and Newfoundland and Labrador Shelf ecosystem for the pre collapse (1985-1987) and invertebrate dominated (2013-2015) periods. Variability in primary productivity, species biomass, and catch reveal that the two model regions are distinct in ecosystem structure and function. Primary and secondary production has increased in the most recent period, however capelin biomass – an important factor for cod recovery – has remained low. Harp seals play a strong top-down ecosystem role and may be contributing to impaired cod recovery. Since the decline in capelin abundance, Arctic cod became an important alternative prey on the Newfoundland and Labrador Shelf region compared to reliance on sand lance and squid on the Grand Banks. Capelin has not shown signs of recovery in either region. Overall, the ecosystem structure in 2018-2020 in both regions is closer to the pre-collapse state than it was in 2013-2015, and the rapid change indicates that the system is highly dynamic.