Fishermen question use of lime to kill tunicates

Some mussel growers on P.E.I. are using lime to control tunicates, an invasive pest, but other fishermen are concerned about the effect that will have on the environment.

The tunicate problem is particularly bad in the eastern part of the Island, where it's become common for fishermen to find their mussel socks covered with hundreds of slimy tunicates. The tunicates rob the mussels of nutrients, slowing their growth, and make harvesting the shellfish difficult.

Some of fishermen are using hydrated lime to try to kill the tunicates, either dipping the socks in the lime or spraying them with it.

"I've had comments given to me by some of our members who are concerned," Ed Frenette, executive director of the P.E.I. Fishermen's Association.

"They're just wondering about the quantities of lime going in, what it does to the water column, how it effects salinity, for example, or how it may affect lobster larvae. However, we have no scientific data."

Scientists with the provincial and federal fisheries departments are trying to put that data together.

"We're doing several things, but one of the most important things is looking at lime itself and what it breaks down to, and how quickly it does that," said Neil McNair, P.E.I.'s manager of aquaculture.

"So we're following the pH of the lime in the lime trough, then if a little bit of lime goes back in the water, we're watching the pH of that, and so far we've seen that pH drop almost as quickly as the equipment can measure it back to the normal pH of water, which is about 8.2 here."

McNair says he expects preliminary results from the study before the end of the year.