Hunting down aliens

CAN YOU SPOT THE DIFFERENCE? Invasive tunicate colonies on settlement plates collected by a team of aquatic invasive invertebrate specialists on Haida Gwaii. Clockwise, from the top left image: Chain tunicate; Star tunicate; Star tunicate and Chain tunicate; Chain tunicate. Photo: Haida Nation/Stu Crawford, Marine Planning

Molly Clarkson —

An international team tracks the spread of tunicates in Haida Gwaii waters

Slimy and brightly coloured, these aliens – otherwise known as Chain tunicate (Botrylloides violaceus) and Star tunicate (Botryllus sclosseri) – spread across docks, boats, gear and the rocky seafloor, smothering seaweeds, barnacles, shellfish and other any other species in their path. How they came to Haida Gwaii remains a mystery but the fact remains that these aquatic aliens are here to stay.

To identify where these and other aquatic invasive invertebrate species are and to work to prevent their spread, a team of alien hunting specialists was created which includes the Haida Oceans Technical Team, the Smithsonian Environmental Research Center (SERC), Gwaii Haanas, and Fisheries and Oceans Canada. In October this team – Stuart Crawford and Lais Chaves (HOTT), Lynn Lee (Gwaii Haanas), Vanessa Hodes and Erika Anderson (Fisheries and Oceans Canada), and Linda McCann and Kristen Larson (Smithsonian Institution) – resumed the annual hunt in Haida Gwaii.*

Hunting for tunicates is different. In fact, hunting for tunicates is a relatively peaceful affair: flat ceramic squares called “settlement plates” are weighted with chunks of brick and lowered to one meter in depth in the water column. The plates are then collected a few months later and analyzed using microscopes for signs of an alien invasion.

This is the third year that the hunt has taken place. In 2014 the team put out their first sampling plates, which they collected and analyzed in the fall of 2015. This process has been repeated twice with more plates being dropped into Haida Gwaii waters every year.

This spring, HOTT and Gwaii Haanas put out ninety plates in nine locations (see map below). “We wanted to see how far the invaders had spread,” says HOTT Ecosystem-based Management Coordinator Stu Crawford, “so we looked at several new sites that have never been monitored for invasive species.”  This included sites on the Daawuuxusda/Duuguusd west coast, Ḵ’iids Gwaay/Ḵ’iis Gwaayee Langara Island, and Moresby Camp.

The results of this year’s hunt were a mixed bag. The new sites were all free of tunicates, which, in the words of Stu Crawford, “is great news.” However, Stu also had some bad news to report: “We found the invasive Star tunicate in Port Clements.  This invader has been in Masset since before 2007, but did not reach Port Clements until this year.”

The Haida Oceans Technical Team will continue to collaborate with Gwaii Haanas, DFO and the Smithsonian Institution on monitoring and outreach related to aquatic invasive species on Haida Gwaii over the coming year.

*Some opportunistic monitoring for aquatic invasive invertebrates by Fisheries and Oceans Canada also took place in Haida Gwaii in 2007, 2012 and 2013.  In 2014 DFO secured funding for a three year monitoring program. This monitoring work was done by a contractor in 2014, but for the subsequent two years monitoring has been a collective effort by DFO, Gwaii Haanas, HOTT and the Smithsonian Institute.

Meet the team (l-r): Erika Anderson (Fisheries and Oceans Canada), Stu Crawford (HOTT), Lynn Lee (Gwaii Haanas), Vanessa Hodes (Fisheries and Oceans Canada), and Linda McCann and Kristen Larson (Smithsonian Institution). Missing from photo: Lais Chaves (HOTT). Photo credit: Jacquie Lanthier.

Map of settlement plate sites. The red dots represent sites put out and collected by HOTT/Haida Fisheries staff, while the green dots represent sites where settlement plates were put out and collected by Gwaii Haanas staff. Map credit: Haida Nation/Stu Crawford, Marine Planning.