Large female northern pike (Esox lucius) do not connect spawning areas across a lagoon network in the southern Baltic Sea

Olga Lukyanova, Robert Arlinghaus, Félicie Dhellemmes

Large individuals may serve as keystone connectors, a role recently demonstrated in Atlantic cod (Gadus morhua). To examine whether this pattern extends to other coastal fish species, we analysed capture-mark-recapture data for 666 individuals out of 4597 tagged coastal northern pike (Esox lucius) and acoustic tracking data from 318 individuals in the southern Baltic Sea, with total lengths of the individuals ranging from 28 cm to 126 cm. Neither mark-recapture nor telemetry data revealed a relationship between individual body length and sex, distance between capture and recapture, connectivity, maximum horizontal displacement, and among-year spawning site fidelity. Instead, connectivity and movement ranges were correlated between years and repeatable, suggesting consistent inter-individual variation unrelated to body length. These findings suggest that large pike do not serve as keystone connectors, likely due to their reproductive biology as total spawners. In total spawners, spatial bet hedging might be realised through mechanisms other than the use of variable spawning sites by individuals within a season, including ecotype evolution of different spawning phenotypes and variable spawning times or locations across years.