Assessing the recovery of commercial fish on the Faroe Bank using Environmental DNA

This project aims to address sustainable fisheries and associated stock management decisions on the Faroe Bank with regards to the variable recovery rates of Haddock and Saithe. The Faroe Bank(FB) is a bathymetric feature SW of the Faroe Islands with a minimum depth of 100m. It is home to what is believed to be a uniquely self-sustained and local cod stock characterised by its own population dynamics, lack of interaction with surrounding cod stocks and individual growth rates that are extremely rapid and amongst the highest of any cod in the North Atlantic. As such it is a potentially valuable commodity for the Faroese fishing economy. The Faroe Bank also hosts other commercially
important demersal fish species, including haddock and saithe. Faroe Bank cod represents a distinct biological management unit with respect to stock assessment due to its characteristic stock dynamics. In contrast the haddock and siathe found on the Faroe Bank are believed to be mix more extensively with nonbank populations such that they are not regarded as a disntinct biological management unit. This has important implications for managing the bank as a mixed demersal fishery if different commercial stocks show variable rates of decline and recovery. Ongoing demersal survey work on the Faroe Bank have shown a serious decline in cod stocks, which appeared to crash around 2005/2006, leading to the closure of the bank to major fishing gears in Janunary
2009. Similiarly, the catch per unit effort for both haddock and saithe exhibited a serious decline during the same period (Figure 1; Appendix 1). Despite the decision to close the bank to commercial fishing activity, the populations of cod, haddock and saithe have remained very low in the period 2009-2015. However, in the last three years (2015-2018), haddock populations appear to be exhibiting signs of a remarkable recovery, with catch per unit efforts increasing to 1200 kg / hr in 2018, matching the peak observed almost 15 years earlier. During the last year saithe populations also appear to have increased above background
levels, although it is too early to diagnose if this is the start of a recovery pattern or an anomalous year. In contrast, populations of cod do not appear to be showing these signs of recovery. Over the last few years it has recently emerged that environmental DNA may serve as a complimentary tool to understand patterns in the spatial and temporal distribution of fish biomass. It is increasingly recognised by ICES, the EU, and several national monitoring programes as an important method for studying mixed fisheries and their corredsponding management policies.