Peritoneal Pigmentation in Purebred and Hybrid River Herring

Abstract

River herring (Alewives Alosa pseudoharengus and Blueback Herring A. aestivalis [bluebacks]) are congeneric, anadromous clupeid fishes that hybridize in areas of sympatry. Peritoneal pigmentation is the most diagnostic characteristic used to distinguish the species, but pigmentation has not been examined in hybrids. We developed a molecular-based assay to distinguish purebred river herring species from F₁ hybrids and compared the peritoneal pigmentation among captive-raised purebred and hybrid individuals. Both wild-caught Alewife and blueback females tank-spawned with conspecific and congeneric males, but Alewives required exogenous hormone administration. Larvae of both species and hybrids were raised for ∼290 d posthatch, and peritoneal pigmentation was quantified. A nuclear gene (rag2) restriction fragment length polymorphism assay was used for species and hybrid identification. The peritoneal pigmentation was significantly darker in hatchery-spawned bluebacks than in Alewives, and hybrids exhibited consistent, intermediate expression. Adult individuals collected from the wild, however, exhibited darker (Alewives) or more variable (bluebacks) peritoneal coloration than their respective, captive-reared juveniles. These results indicated that peritoneal pigmentation alone is insufficient for diagnostic river herring species identification and should be coupled with genetic assays.

Received February 8, 2015; accepted March 30, 2015

ACKNOWLEDGMENTS

Partial funding was provided by New Hampshire SeaGrant and the New Hampshire Agricultural Experiment Station. This is Scientific Contribution 2607. This work was supported by the U.S. Department of Agriculture, National Institute of Food and Agriculture Hatch Project NH00566. The authors thank Michael Bailey and Kevin Sullivan for logistical help during all phases of these experiments. The authors also thank Peter Goode and Olivia Foy for conducting the RFLP assays and Aurora Burgess, Catherine Caruso, Calvin Diessner, Kristin Duclos, Linas Kenter, and Amber Litterer for fish husbandry and sampling assistance.