Climate change: Scottish shellfish threatened

North Sea Oyster

Scottish shellfish are at risk from an invasion of tiny Japanese sea creatures known as schizoporella japonica.

The orange-red sea creatures are thought to be spreading with the help of climate change.

Schizoporella japonica was first recorded in European waters in 2010, but is now found in at a quarter of Scottish ports. It has been found in fewer than one in 10 harbours in England and Wales.

A research paper on the creatures by Edinburgh University marine researcher Dr Jennifer Loxton said: “In Scotland s. japonica displays a more continuous distribution as it has successfully established populations in marinas on both the east and west coasts and in both Orkney and Shetland.”

The creatures are a threat to Scotland’s aquaculture industry – in particular mussels and oysters – because it can decrease their value by growing on their shells. In some cases they can even smother mussels.

Ms Loxton told BBC Scotland’s Landward programme the spread was likely to have been enabled by climate change.

As sea ice recedes in warmer seas, more shipping trade routes are being used, and with them cold-resistant species such as s. japonica can spread, she said.

“For most of us, not really much of a problem at all, it’s just an irritant that you’ve got to scrape it off your boat, but the one thing that we are worried about is with aquaculture, in particular mussels and oysters because it can decrease the value by growing on their shells,” she said.

Scottish Shellfish Risk

Even in small numbers they can reduce the price farmers can get for shellfish while larger colonies can impact shellfish weight and survival.

The orange growths that can been seen on hard surfaces are made up of thousands of individual animals that build a collective skeleton colony.

It is understood the tiny invertebrate animals are likely to be “hitchhiking” their way around the UK by encrusting ship hulls or on marine industry infrastructure such as floating components of marine energy equipment and aquaculture nets.

“It has such a really wide temperature tolerance,” Dr Loxton said. “Where it lives in Japan, the water freezes over in the winter, then gets really, really warm in the summer. So this one can take pretty much anything that’s thrown at it.

“We think it’s come from the boats which have come through the northern waters across from Canada.

“It’s also, we think, moving around with some of the industry that we do here in Scotland, so fish farms, but also renewable energy industry, so we’ve been finding it on wave and tidal turbines.”

Researchers have been working with councils in highly affected areas such as Orkney to minimise the risk of invasion and safeguard marine habitats.

This article was originally published as Climate change: Scottish shellfish threatened by Japanese invaders at The Herald on 11/04/19.

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