Is the Collapse of Mud Shrimp (Upogebia pugettensis) Populations Along the Pacific Coast of North America Caused by Outbreaks of a Previously Unknown Bopyrid Isopod Parasite (Orthione griffenis)?

Estuaries and Coasts (2011) 34:336350 DOI 10.1007/s12237-010-9316-z

Is the Collapse of Mud Shrimp (Upogebia pugettensis) Populations Along the Pacific Coast of North America Caused by Outbreaks of a Previously Unknown Bopyrid Isopod Parasite (Orthione griffenis)?

Brett R. Dumbauld & John W. Chapman &

Mark E. Torchin & Armand M. Kuris

Received: 30 November 2009 /Revised: 4 June 2010 /Accepted: 11 June 2010 /Published online: 9 July 2010 # U.S. Government 2010

Abstract A dramatic increase in prevalence of the recently discovered bopyrid isopod parasite, Orthione griffenis, likely introduced in the 1980s from Asia to the Pacific coast of North America, coincided with the 2002 collapse of a population of its burrowing mud shrimp host, Upogebia pugettensis, in Willapa Bay, Washington that had been stable since monitoring began in 1988. An examination of whether O. griffenis infections were sufficient to cause this decline and other recently noted U. pugettensis population collapses in Pacific Coast estuaries was conducted. O. griffenis prevalence was the highest in large reproductive-sized female shrimp and caused an

estimated average 68% loss of U. pugettensis reproduction in Yaquina Bay, Oregon over a 5-year period. O. griffenis prevalence fluctuated from year to year, but trends were similar in all estuaries sampled. Uninfected shrimp transplanted back into locations from which they had disappeared acquired the parasite, suggesting that O. griffenis is extremely effective at finding its host even in estuaries with very low host density. Since both U. pugettensis and O. griffenis have pelagic larval stages, their population dynamics are also influenced by coastal nearshore oceanography and estuarine recruitment success. Coastwide lack of estuarine recruitment appears to coincide with declines in density of a co-occurring thalassinid shrimp, Neotrypaea californiensis, but cannot alone explain U. pugettensis population collapses. Although patterns observed to date could be explained by the presence of either a native or introduced parasitic castrator, assumptions of a resilient co-evolved hostparasite relationship do not apply for introduced species, so continued efforts to follow the spatial extent and consequences of the O. griffenisU. pugettensis hostparasite relationship are warranted.

Keywords Parasitic castrator . Local extinctions . Introduced species . Neotrypaea californiensis . Thalassinidea

Introduction

Upogebia pugettensis is a common species of thalassinid shrimp that inhabits intertidal mudflats in estuaries along the Pacific Northwest coast of North...