Batch Fecundity and Batch Number in River Herring

Innovative methods for analysis of reproduction may inform efforts to conserve species of concern. We present data on oocyte development, batch size and batch number of anadromous river herring (Alewives [ALE; Alosa aestivalis] and Blueback Herring [BBH; A. pseudoharengus]) in Connecticut, USA. At our collection site for ALE, we could distinguish females arriving at spawning habitat (uprunners) from females leaving (downrunners), but we could not tell uprunners from downrunners in our collections of BBH females. We performed whole-mount procedures on subsamples of ovaries for image analysis of oocyte size and gravimetric analysis of fecundity. We also performed both whole-mount and histological analysis on other ovaries, to compare gravimetric and stereological estimates of oocyte batch size and to precisely characterize oocyte developmental stages. ALE uprunners had advanced oocytes at the ultimate stage of vitellogenesis, and additional less-developed batches. Postovulatory follicles were absent in uprunners but were prevalent in downrunners. ALE females spawned a mean of three batches in a season and batch fecundity decreased after the first spawning. BBH had comparable patterns of oocyte development. Our analyses, which indicate that oocyte maturation continues during the breeding season, yield more accurate and precise values of annual reproductive output for these species.