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JELLYFISH

In general, the usual suspects on the roster of invasives have yet to feature in the Flow Country as a material consideration, perhaps because of our formidable land barriers.But what is possible is well illustrated by an article in the Wall Street Journal of January 14, 2015. From Alaska to California, wave after wave of live biological debris has arrived from Japan on the planks, buoys and general wreckage that ended up in the sea after the tsunami of 2011. These incomers have the potential to “extinguish native species, destroy fisheries and permanently alter ecosystems.” About eighty totally new and unwelcome species have been identified so far – and killed.

Well represented, inevitably, are various species of jellyfish. If the climate behaves as most scientists predict, there is a probability that warming oceans will make jellyfish blooms a common and dangerous occurrence. Impossible in Scotland? Not so. In the autumn of 2014 large numbers of pelagia noctiluca jellyfish slipped through the nets into the salmon cages at Loch Maddy in North Uist. Around 300,000 salmon were killed. ‘Our thoughts are with David MacIver and his team in Loch Maddy,’ said David’s boss, who clearly has experience as a bereavement specialist.

On February 6, 2014 the online journal FishnewsEU reported that a Norwegian company, Marine Harvest, had halted harvesting salmon in Ireland. It was stated that “severe storms affected feeding and the ability to treat for sea lice and Amoebic Gill Disease. Pancreas Disease severely affected two sites …. while high occurrences of jellyfish were reported across all regions, resulting in elevated mortality .… record sea water temperatures of 21 degrees were a factor in the proliferation of parasites and disease and may be connected to the increase in algae blooms and jellyfish.”

Jellyfish polyps grow to maturity while stuck to almost any underwater marine structure. Aquaculture cages are a particular favourite. Then they go out into the world and breed. Tens of thousands of eggs per day is the norm from one jellyfish. “Every day. For months. Hermaphroditism. Cloning. External fertilisation. Self-fertilisation. Courtship and copulation. Fission. Fusion. Cannibalism. You name it, jellyfish do it.” (Gershwin: Stung! On Jellyfish Blooms and the Future of the Ocean, 2013.)

The problem (which has turned the Black Sea into a dead zone) has arisen because of over-fishing. Competitors for the same food stocks such as sardines and anchovies have been fished out while pests that were once eaten by larger fish have grown too numerous for their predators to keep in check. Opportunists such as jellyfish have taken full advantage. It is both ironic and mirthful that a lump of glutinous matter lacking backbone, brain and eyes should now be able to lord it in many of our seas. As with many other undesirable species, the means of introduction into fresh territory is often via the discharge of ballast water by ocean-going vessels upon harbouring.

© 2018 FCRT / ALASDAIR OGILVIE

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