Data from: Predator-prey role reversal may impair the recovery of declining pike populations

Many fish populations have experienced declines in recent decades due to
anthropogenic disturbances, such as overfishing and habitat exploitation.
Despite management actions many populations show a limited capacity to
recover. This may be attributed to reversal of predatory‐prey roles, yet
empirical evidence to that effect remains scarce. Here we combine field
and laboratory studies to investigate the interaction between pike (Esox
lucius), a large keystone top predatory fish, and the small‐bodied
mesopredatory threespine stickleback (Gasterosteus aculeatus) in the
Baltic Sea where pike populations have declined. Our data suggest that
stickleback predation on pike larvae depletes a large proportion of the
recruitment and influences the size distribution through size‐selective
predation, which is corroborated by a gape‐limitation experiment and diet
analysis of wild captured sticklebacks. The effects of stickleback
predation are present across several populations and years, and our data
suggests that early arrival of sticklebacks has stronger effects on
juvenile pike survival. Finally, we use data on pike gape‐limitation and
the size distribution of sticklebacks to illustrate the process of role
reversal. These findings suggest that mesopredator behaviour can reduce
recruitment of a top predator species and impair the capacity of
populations to recover. This emphasizes predator‐prey role reversal as an
important ecological and evolutionary driver that influences the outcome
of restoration and management actions.