An Estimation of the Possible Migration Path of the Pacific Oyster (Crassostrea gigas) Along the Northern Coast of Patagonia

Abstract

In 1981, the Pacific oyster Crassostrea (Magallana) gigas was illegally introduced for aquaculture purposes in San Blas Bay located on the southern coast of Buenos Aires Province, Argentina. The presence and colonization of oysters north of Río Negro Province, 100 km to the southwest of San Blas Bay, was reported in 2005. There remains a controversy about whether or not the oyster was capable of migrating southwest to Río Negro Province from San Blas Bay, which motivates the present investigation. While one part of the local community supports that the Pacific oyster migrated naturally southwestwards reaching the northern coast of Río Negro in 2005, another faction denies this hypothesis. The aim of this work is to determine whether or not the planktonic larvae of this invasive species could have reached the mouth of Río Negro. We assume that the oyster can produce larvae after 2 years of being set on the bottom and the larvae can drift as zooplankton during 1 month. Longshore mean current was considered as the single forcing in natural transporting of oyster larvae along the coast. Shallow water wave parameters were computed from deep water wave parameters obtained from the Simulated WAves Nearshore (SWAN) model driven by NCEP/NCAR I global reanalysis. The migration path was computed from longshore current intensities, which were estimated using the modified experimental expression given by Longuet-Higgins. Results obtained in this paper support the possibility that the Pacific oyster larvae could have arrived at Río Negro Province, between 2002 and 2005.