Environmental conditions can influence biological characteristics, such as phenology and body size, with important consequences for organismal fitness. Examining these fitness consequences under natural conditions through genetic pedigree reconstruction offers a lens into potential population responses to changing environments. Over 3 years (2013–2015), we introduced adult alewife (Alosa pseudoharengus), anadromous, iteroparous clupeids, into one Massachusetts (USA) lake to complete the first detailed examination of this species’ mating system and assess relationships among body size, reproductive timing, and seasonal reproductive success. We reconstructed pedigrees using 15 microsatellites and genotypes from all possible parents and samples of naturally produced offspring within 4 months of hatching. In each of the 3 study years, spawning adults had multiple mates and spawned multiple times. Larger females that arrived and were translocated earlier had higher reproductive success. Declining body size and altered migration timing, through an influence on reproductive success, can influence population vital rates and productivity over time.

We are sharing the microsatellite data for our river herring adult and juvenile samples collected between 2013 and 2015. The microsatellite data were used to complete parentage analyses of fish stocked in a spawning pond in Eastern Massachusetts. These data are simply the microsatellites markers. We later estimated reproductive success using parentage assignments based on pedigree analyses with CERVUS version 3.0 (Marshall et al. 1998; Kalinowski et al. 2007). 

These data may include missing values where microsatellites were undetectable or the sample was contaminated.