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Match-mismatch dynamics in the Norwegian-Barents Sea system

Sofia A. Ferreira*, Leif C. Stige, Anna B. Neuheimer, Bjarte Bogstad, Natalia Yaragina, Irina Prokopchuk, Joël M. Durant

*Corresponding author:

ABSTRACT: One key process affecting variation in the recruitment of fish into fisheries is the spatio-temporal overlap between prey and predator (match-mismatch hypothesis, MMH). The Northeast Arctic cod Gadus morhua and its dominant prey, the copepod Calanus finmarchicus, have long been studied in the Norwegian-Barents Sea system. However, the mechanistic explanation of how cod survival is affected by MMH dynamics remains unclear. Most MMH studies focus on either the time synchrony or the spatial overlap between trophic levels. Here, we use G. morhua larvae and C. finmarchicus data collected in the Norwegian-Barents Sea via ichthyoplankton surveys from 1959 through 1992. To assess the effect of the predator-prey relationship on the predator recruitment to the fisheries at age 3 (as a measure of survival), we develop a metric of predator-prey overlap by using spatio-temporal statistical models. We then compare its interannual variability with the predator abundance at recruitment to assess how MMH dynamics explain the survival of cod during the early life stages. We find that the amount of overlap between cod larvae (length of 11–15 mm) and their prey explains 29% of cod recruitment variability. Positive correlations between predator-prey overlap and subsequent recruitment are also found for predators of 6–10 and 16–20 mm, but not for 21+ mm. This improved predator-prey overlap metric is thus (1) useful to better understand how predator-prey dynamics at early life stages of fish impact the survival of later stages; and (2) a valuable tool for assessing the state of an ecosystem.