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)