Salmon fishing in Scotland threatened by rising sea temperatures

Since March 2023, Scotland's waters have been gripped by an unprecedented Category 4 marine heatwave, causing mass marine mortalities.

Transcript

00:00 Since March, Scotland's waters have been gripped by an unprecedented Category 4 marine heatwave,

00:06 an unusual event which has caused mass marine mortalities.

00:10 For some of Scotland's salmon farms, the staggering 4 degree temperature increase

00:14 has led to a heightened risk of sea lice infestations.

00:18 A recent investigation uncovered alarming evidence on five farms

00:22 where fish were observed covered in the invasive sea lice.

00:27 Marine heatwaves are becoming more frequent,

00:30 which creates this optimal breeding reservoir for sea lice to rampantly reproduce.

00:35 And these are the things that eat the skin, the mucus, the blood of the salmon.

00:40 And, you know, these can expel out into the wider environment in their millions.

00:45 Sea lice, typically found in low densities in the wild, have become a growing concern.

00:50 An exacerbating factor is the increasing sea temperature.

00:54 2022 was a record-breaking year with salmon deaths doubling.

00:58 This year the outlook is even grimmer.

01:00 An alarming 8.9 million fish have been reported as dead on Scottish salmon farms in 2023 already.

01:08 And while salmon farming was once seen as a potential solution to helping wild stocks replenish,

01:13 sea lice are now making it a problem as they're spreading from the farms to wild salmon.

01:19 Salmon farming was seen as a sort of salvation.

01:22 And then, of course, the complexities become more apparent.

01:27 And right now, the numbers and size of wild salmon continue to drop. It's tragic.

01:35 The salmon industry says it prioritises the well-being of the fish

01:39 and stresses the technologies and innovations it uses against the sea lice.

01:44 But there are other threats that come from rising sea temperatures.

01:48 Jellyfish thrive in warmer waters and they can both sting the salmon and block their gills.

01:54 Across Europe and the world, rising sea temperatures in 2023 tested marine ecosystems and aquaculture.

02:02 Any sudden big rise that gets beyond what the animals are used to can cause stress to the point where they will die.

02:11 We could see mass mortality of aquaculture, whether they be fish or shellfish.

02:16 Salmon is one of the UK's top exports, but this year around a quarter of farmed salmon perished.

02:22 And whilst innovative solutions are being explored,

02:25 the global challenge of increasing sea temperatures will continue to affect both those who farm and fish

02:31 and the marine life they oversee.

02:34 (whooshing)

02:36 (whooshing)