Lobsters and crabs as potential vectors for tunicate dispersal in the southern Gulf of St. Lawrence, Canada

Renée Bernier

doi:10.3391/ai.2009.4.1.11

Abstract

Following anecdotal reports of tunicates on the carapaces of rock crab (Cancer irroratus) and American lobster (Homarus americanus), we evaluated the role of these species and northern lady crab Ovalipes ocellatus as natural vectors for the spread of invasive tunicates in the southern Gulf of St. Lawrence. Several hundred adult specimens of crabs and lobster from two tunicateinfested estuaries and Northumberland Strait were examined for epibionts. Small patches of Botrylloides violaceus were found on rock crabs examined from Savage Harbour and a small colony of Botryllus schlosseri was found on one lobster from St. Peters Bay. Lobster and lady crab collected in Northumberland Strait had no attached colonial tunicates but small sea grapes (Molgula sp.) were found attached on the underside of 5.5% of the rock crab and on 2.5% of lobster collected in Northumberland Strait in August 2006. Lobster and rock crab clearly represent a vector for the spread of invasive tunicates regionally and wherever living crustaceans are shipped globally.

Highlights

Since about 1998, the viability of the bivalve aquaculture industry in eastern Canada, and in Prince Edward Island (PEI, Figure 1), has been challenged by the colonization and spread of several non-indigenous tunicate species: the clubbed tunicate (Styela clava Herdman, 1882), first detected in 1997; the golden star tunicate (Botryllus schlosseri (Pallas, 1766)) in 2001; the violet tunicate (Botrylloides violaceus (Oka, 1927)) in 2002; and the vase tunicate (Ciona intestinalis (Linnaeus, 1767)) in 2004 (Locke et al 2007, Ramsay et al 2008)
Lobster and rock crab were expected to occur in all three study areas, but northern lady crab were expected to be found only in Northumberland Strait (Voutier and Hanson 2008)
The most common rock crab epibionts were green, red and brown algae, which were found on 58% and 64% of rock crab examined from St

Summary

Introduction

Since about 1998, the viability of the bivalve aquaculture industry in eastern Canada, and in Prince Edward Island (PEI, Figure 1), has been challenged by the colonization and spread of several non-indigenous tunicate species: the clubbed tunicate (Styela clava Herdman, 1882), first detected in 1997; the golden star tunicate (Botryllus schlosseri (Pallas, 1766)) in 2001; the violet tunicate (Botrylloides violaceus (Oka, 1927)) in 2002; and the vase tunicate (Ciona intestinalis (Linnaeus, 1767)) in 2004 (Locke et al 2007, Ramsay et al 2008). The rapid spread of these non-indigenous tunicates along the PEI coast has prompted several investigations into the vectors facilitating their dispersal. Lobster and rock crab were expected to occur in all three study areas, but northern lady crab were expected to be found only in Northumberland Strait (Voutier and Hanson 2008)

Methods

Results

Conclusion