Effect of Water Quality on Hatching Success of Blueback Herring Eggs in the Chowan River Basin, North Carolina

River herring (alewife [Alosa pseudoharengus] and blueback herring [A. aestivalis]) within the Albemarle Sound basin in North Carolina once supported large commercial fisheries that have declined dramatically since the 1970s. Overfishing, poor water quality, and habitat loss have been suggested as causes of this decline. The objective of this study was to examine the effect of water quality on the hatching success of blueback herring eggs in the Chowan River, a major tributary to Albemarle Sound. We combined eggs and milt obtained from running-ripe fish and placed incubators containing fertilized eggs at 11 sites throughout the basin. Mean hatch rates at field sites ranged from 26% to 89%, compared to a mean of 92% for control trials carried out using distilled water. An analysis of covariance indicated that hatch rates were significantly related to the dissolved oxygen level and were lower at sites on smaller tributaries when compared to sites on the mainstem of the Chowan River. Of the water quality parameters for which published standards exist, dissolved oxygen was the only one not within documented levels for normal development of blueback herring eggs. Given the relatively high hatch rates at most sites, we conclude that mortality of blueback herring eggs due to poor water quality is unlikely to account for the declines in abundance that have been observed.

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