Temporal Patterns of Migration and Spawning of River Herring in Coastal Massachusetts

Abstract

Migrations of springtime Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are monitored in many rivers along the Atlantic coast to estimate population sizes. While these estimates give an indication of annual differences in the number of returning adults, links to the subsequent timing and duration of spawning and freshwater juvenile productivity remain equivocal. In this study, we captured juvenile river herring at night in 20 coastal Massachusetts lakes using a purse seine and extracted otoliths to derive daily fish ages and back-calculate spawn dates. Estimates of spawning dates were compared with fishway counts of migrating adults to assess differences in migration timing and the timing and duration of spawning. We observed a distinct delay between the beginning of the adult migration run and the start of spawning, ranging from 7 to 28 d across the 20 lakes. Spawning continued 13–48 d after adults stopped migrating into freshwater, further demonstrating a pronounced delay in spawning following migration. Across the study sites the duration of spawning (43–76 d) was longer but not related to the duration of migration (29–66 d). The extended spawning period is consistent with recent studies suggesting that Alewives are indeterminate spawners. The long duration in freshwater provides the opportunity for top-down (i.e., predation on zooplankton) and bottom-up (i.e., food for avian, fish, and other predators) effects, with implications for freshwater food webs and nutrient cycling. General patterns of spawn timing and duration can be incorporated into population models and used to estimate temporal changes in productivity associated with variable timing and density of spawning river herring in lakes.

Received January 13, 2017; accepted June 7, 2017Published online September 12, 2017

ACKNOWLEDGMENTS

We thank Steven Mattocks, Vasili Luzanau, and Meghna Marjadi for their help with field sampling. Lauren Maslon, Ariana Andrewes, Tooba Gilani, Emily Jacoboski, Jair Cruikshank, Ashley Hoffman, Campbell Morgan, and Nicole Leaper assisted with otolith extraction and aging. Jason Carmignani provided help with RStudio. Brad Chase (MDMF) provided technical advice regarding site selection, and David Post provided details regarding the purse seine design. This research was supported through funding from the University of Massachusetts Amherst, Massachusetts Division of Marine Fisheries, and National Fish and Wildlife Foundation. The experimental protocol was approved by the University of Massachusetts Institutional Animal Care and Use Committee (IACUC number 2013-0047). Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.