Data from: Multiple spawning run behavior and population consequences in migratory striped bass Morone saxatilis

Multiple spawning runs cause different contingents within the same
population to experience varying demographic fates that can stabilize
populations through the portfolio effect. Multiple spawning runs are
reported here for the first time for striped bass, an economically
important coastal species, which is well known for plastic estuarine and
shelf migration behaviors. Adult Hudson River Estuary striped bass (n=66)
were tagged and tracked with acoustic transmitters from two known spawning
reaches separated by 90 km. Biotelemetry recaptures for two years
demonstrated that each reach was associated with separate spawning runs.
Time series of spawning run trajectories were examined via nonparametric
dynamic time warping and revealed two dominant time series centroids, each
associated with the two spawning reaches. In 2017, the lower reach run
occurred earlier than the higher reach run, but difference in timing was
not observed in 2018. The majority (84%) of returning adults in 2018
showed the same run behaviors exhibited in 2017. The two spawning run may
have been cued differently by temperatures, where warming lagged 1-week at
the higher reach in comparison to the lower reach. The two spawning runs
exhibited similar Atlantic shelf migration patterns with strong summer
fidelity to Massachusetts Bay and winter migrations to the southern US
Mid-Atlantic Bight. Still, in 2017, differing times of departure from
spawning reaches into nearby shelf waters likely caused the early spawning
run to experience substantially higher mortality than the later run.
Anecdotal evidence suggests that higher fishing effort is exerted on the
early-spawning run as it first enters shelf fisheries. Thus, as in salmon,
multiple spawning runs by striped bass can lead to differential
demographic outcomes, contributing to overall population dynamics.