Multiple spawning run contingents and population consequences in migratory striped bass Morone saxatilis

Abstract

Multiple spawning run contingents within the same population can experience varying demographic fates that stabilize populations through the portfolio effect. Multiple spawning run contingents (aka run timing groups) 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 river reach was associated with separate contingents. Time series of individual spawning phenologies were examined via nonparametric dynamic time warping and revealed two dominant time series centroids, each associated with a separate spawning reach. The lower spawning reach contingent occurred earlier than the higher reach contingent in 2017 but not in 2018. The majority (89%) of returning adults in 2018 showed the same contingent behaviors exhibited in 2017. Spawning contingents may have been cued differently by temperatures, where warming lagged 1-week at the higher reach in comparison to the lower reach. The two contingents 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 into nearby shelf waters likely caused the early lower reach contingent to experience substantially higher mortality than the later upper reach contingent. Anecdotal evidence suggests that higher fishing effort is exerted on the early-departing individuals as they first enter shelf fisheries. Thus, as in salmon, multiple spawning units can lead to differential demographic outcomes, potentially stabilizing overall population dynamics.

Primed and cued: long-term acoustic telemetry links interannual and seasonal variations in freshwater flows to the spawning migrations of Common Snook in the Florida Everglades

“…Further, we found that fish size positively correlated with migration probability. This relationship to size has been previously reported for Snook, and for other migratory species including Barramundi in Australia and Striped Bass in Chesapeake Bay [ 58 , 59 , 100 , 105 ]. Both drydown duration, which affects access to freshwater prey resources, and fish size can indicate available energy resources, suggesting that energy status may serves as key factor in the decision to migrate each year.…”

“…The presence of distinct spawning groups has been observed in other migratory fishes. Secor et al [ 100 ] reported staggered migration timing for Striped Bass ( Morone saxatilis ) in the Hudson River, USA. Further, Koster et al [ 15 ] found differences in migration timing for Australian Grayling.…”

Can Identifying Discrete Behavioral Groups With Individual-Based Acoustic Telemetry Advance the Understanding of Fish Distribution Patterns?

“…Striped bass are a popular commercial and recreational fish in coastal areas and have been historically imperiled and at times overfished (Richards and Rago, 1998;Shepherd et al, 2018). Coastal striped bass are composed of separate spawning populations (Wirgin et al, 2020) that have different distributions and movement patterns (e.g., Rulifson and Dadswell, 1995;Secor et al, 2020). These stock-specific movement patterns can vary across locations, seasons, and years (e.g., Waldman et al, 1990;Kneebone et al, 2014).…”

Intraspecific variation in migration timing of green sturgeon in the Sacramento River system

“…However, Chinook salmon also exhibit variation in migration timing of smolts and adults (Fisher, 1994; Singer et al, 2020; Yoshiyama et al, 2000). Striped bass ( Morone saxatilis ) in the Hudson River Estuary migrate different distances to spawning sites and maintain these site preferences across years (Secor et al, 2020), effectively dispersing reproductive effort across multiple sections of the river. Effective management of wild populations requires understanding diversity in migratory tactics, but intraspecific variation in movement may be hard to describe while monitoring wild fishes with traditional sampling techniques, such as setlines and trapping.…”