Estimating Long-term Trends in Populations of Two Ecosystem Engineering Burrowing Shrimps in Pacific Northwest (USA) Estuaries.

Temporal variation in the density and distribution of the burrowing shrimps, Neotrypaea californiensis and Upogebia pugettensis, were compared in two estuaries along the West coast of the United States (USA) where they are recognized as important ecosystem engineers. Since these shrimp construct deep burrows in the sediment, we quantified the relationship between burrow openings and shrimp density (1.5 and 1.7 burrow openings per shrimp for N. californiensis and U. pugettensis respectively) to permit population abundance estimates to be made over broad landscape scales. Neotrypaea californiensis populations estimated from burrow counts collected using a gridded survey design across representative tide flats declined by 25% between 2008-2010 in Yaquina Bay, Oregon and by 67% in Willapa Bay, Washington from 2006-2011, but increased again in Willapa Bay by 2014. Upogebia pugettensis had mostly disappeared from Willapa Bay by 2006 and declines were observed in Yaquina Bay, but the magnitude and long-term trajectory of U. pugettensis in this estuary was less clear. These species population fluctuations mirrored those observed in density collected at discrete sampling locations over the same period, equate to large changes in secondary production, and have likely resulted in substantial changes to estuarine habitat and food webs.

First evaluation of resistance to both a California OsHV-1 variant and a French OsHV-1 microvariant in Pacific oysters.

BACKGROUND: Variants of the Ostreid herpesvirus 1 (OsHV-1) cause high losses of Pacific oysters globally, including in Tomales Bay, California, USA. A suite of new variants, the OsHV-1 microvariants (µvars), cause very high mortalities of Pacific oysters in major oyster-growing regions outside of the United States. There are currently no known Pacific oysters in the United States that are resistant to OsHV-1 as resistance has yet to be evaluated in these oysters. As part of an effort to begin genetic selection for resistance to OsHV-1, 71 families from the Molluscan Broodstock Program, a US West Coast Pacific oyster breeding program, were screened for survival after exposure to OsHV-1 in Tomales Bay. They were also tested in a quarantine laboratory in France where they were exposed to a French OsHV-1 microvariant using a plate assay, with survival recorded from three to seven days post-infection. RESULTS: Significant heritability for survival were found for all time points in the plate assay and in the survival phenotype from a single mortality count in Tomales Bay. Genetic correlations between survival against the French OsHV-1 µvar in the plate assay and the Tomales Bay variant in the field trait were weak or non-significant. CONCLUSIONS: Future breeding efforts will seek to validate the potential of genetic improvement for survival to OsHV-1 through selection using the Molluscan Broodstock Program oysters. The lack of a strong correlation in survival between OsHV-1 variants under this study's exposure conditions may require independent selection pressure for survival to each variant in order to make simultaneous genetic gains in resistance.