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HOW MANY FISH IN A PEN?

Fish Mortalities, Temperature, and Toxic Algae

PHOTO CREDIT- Cermaq Canada

When a natural disaster or calamity hits a fish farm the cries of doom get fairly shrill, and sometimes it requires a moment to step back and think and read. Farm site mortalities spilled into the news from both coasts of Canada as recently as late summer and fall of 2019, and the morts were in the thousands. In 2017 a rogue wave took out an ocean pen in Washington State bringing the wrath of state regulators.

Opponents of ocean-based net-pen fish farming decry the practice of rearing fish in Canada. Prime Minister Justin Trudeau made it a political issue before the recent Canadian election. He was promising to make the industry raise fish on land, which has yet to prove sustainable and which presents a jeremiad of prohibitive possibilities.

The opponents to ocean-based net-pen fish farming argue no other agriculture industry leads to such devastation in the wake of their rearing practices, so much death, so much waste, maybe even suffering. The complainants are conveniently ignoring the present 40 percent reduction of hog population in China now spreading to other countries in a highly contagious swine-specific pathogen. Or what about the Boomer Age disappearance of cows from the UK due to an outbreak of Mad Cow Disease, something which does indeed crossover with lethal consequences to human beings?

For as long as I've been talking to fish farmers on the west coast of B.C. (since 1995), the issue of red tides, aka Harmful Algae Blooms (HABs) or the possibility of changes in water temperature have been a concern for farm managers on job sites. They have to watch for it all the time. These HABs vary in size and season, they are unpredictable, and they are dangerous to fish and fowl and even larger animals.

Cermaq saw outbreaks of algae inundate three farms on the west coast of Vancouver Island. The company provides an update of conditions at these three Cermaq farm sites later in this article and on their website, but first I talked to Ian Roberts, of Mowi Scotland who spent a couple decades running farm sites on Canada's west coast for Mowi (then Marine Harvest Canada).

"Hearing of the fish losses this summer has been very upsetting, as I know first-hand how disappointing it is to lose just one fish after putting years of effort in to caring for it," says Roberts. "But the reality is: growing fish in their natural environment is still the best way to raise a fish, but the sea can and does present serious challenges to farm-raised fish. They are unable to escape from areas and depths affected by changing water temperatures, low oxygen and harmful algae blooms," says Roberts.

He notes that farmers do try to mitigate for poor water conditions, specifically events of temperature change, "by forcing air into the water at depth and bringing cooler water to the surface to bring comfort to the fish. Over the years, the sector has suffered from mass mortality events, but they have become rarer and rarer as farmers have invented ways to mitigate some of the threat. But it can be impossible to mitigate against something like ‘the blob’ that amasses out at sea before coming ashore – sometimes it’s just too intense for a fish to handle and for a farmer to mitigate."

[Roberts refers to a persistent warm water mass in the North Pacific Ocean in recent years, beginning in 2015. On Oct 9, 2019 the New Scientist published an article 'Return of warm water 'blob' in the Pacific threatens marine life' stating, "The reappearance of a vast ‘blob’ of abnormally warm water in the Pacific, around seven times the size of Alaska, has raised the prospect of serious impacts on marine ecosystems and the weather."]

Presently a private study associated with Dr Richard Beamish has been launched into the behavior of salmon in the North Pacific in winter. Scientists from six Pacific Rim nations have put an academic focus on climate changes affecting the behavior of salmon in winter habitat of the Gulf of Alaska, and already they have observed salmon shoals feeding where the water is cooler at greater than usual depths. A consortium of scientists have reports pending this year from their first excursion and planning is underway for a second winter pelagic excursion involving more vessels and scientists in February 2020.

"As for the East Coast," says Roberts, "there have been super-chill events in the past that have killed fish. This latest event," a Northern Harvest (Mowi-owned) farm site in Newfoundland, "was high water temperatures and associated lowered oxygen levels (oxygen is less abundant in warmer water)."

"It was a temperature anomaly we encountered with the rise of water temperature and the effect was devastating to the fish," says Jason Card, Mowi East spokesman. "The Mowi site is under suspension by the province of Newfoundland until modifications to the net-pens are made to add 20 metres of depth." (A CBC report said,  "Unusually warm water over an 11- to 13-day period led to low oxygen levels that caused a mass die-off of farmed Atlantic salmon on Newfoundland's south coast, says the province's chief aquaculture veterinarian.")

The Newfoundland provincial government introduced site regulations to enhance the possibility of fish surviving adverse temperature events in the future, and Mowi won't be operating the site until the pens are in compliance. "The fish were not able to escape to areas less affected (which is what a wild fish would do)," says Roberts. "That said, I’ve witnessed wild black cod floating to the surface during extreme algae blooms that covered the whole depth of the ocean near Bella Bella, British Columbia – even they were unable to escape."

"As for recent event off the west coast of Vancouver Island farmers are unfortunately very familiar with the Chaetocerous species of algae. It always seemed to show up in spring and autumn. It doesn’t arrive with the obvious colour of a bloom (red, orange, yellow etc) but instead the water can look very clear. Chaetocerous actually clings to things, and when they cling to the gill of a fish it can cause severe trauma. And to make matters worse, a fish’s response to damaged gills is to send mucous to the affected areas, for repair. But mucous on the gills actually prevents oxygen was penetrating the gills, which then essentially suffocates the fish."

Roberts has been meeting the challenges of growing fish on the oceans for a couple of decades. "Now, of course some people will call for ‘land-based closed containment’ as a solution. But in reality, the same issues are present in a closed system, with only minutes to solve the issue in a controlled environment. If the chemical structure of the water is off (high levels of ammonia for example) then you can kill thousands of fish in minutes. If the oxygen supply breaks down, then you have minutes, at best. You may have better control of the water parameters, but you also increased the risk significantly."

Water temperature changes are being observed at the same time as the pursuit of understanding toxic red tide (algae) blooms never ends. "Deadly Algae Are Creeping Northward: In a warming ocean, Alexandrium algae are shredding marine food webs—and disrupting beloved Alaska traditions," Miranda Weiss writes in the Atlantic on Oct.29, 2019  https://www.theatlantic.com/science/archive/2019/10/plague-toxic-algae-making-shellfish-deadly/600406/

Weiss describes an event in 2015, "Murres are tenacious hunters, diving up to 600 feet underwater to catch fish. But these birds had starved to death, researchers concluded, likely because the so-called Warm Blob, a pool of water in the North Pacific that was strikingly warmer than normal, had made it impossible for them to find enough food. No one could say why."

There are people in Alaska studying the algae and the changing conditions of the water temperature, "So I ended up traveling to the remote Popof Island, in far western Alaska, with a scientist named Bruce Wright. Wright feels certain that he knows why the murres died. He blames a type of microscopic algae that floats in every ocean on Earth."

Weiss has done her journalistic due diligence researching the problem of toxic algae or "“red tides” — which scientists refer to collectively as harmful algal blooms, or HABs — a bloom which occurs when algae that produce natural poisons grow explosively, impacting human or ecosystem health.

"Many different species of algae cause HABs, and they can last for weeks or longer, decimating fisheries, closing swimming beaches, and making it hard for coastal residents to breathe. In the sea and in lakes, they have killed fish, birds, turtles, whales, manatees, and even dogs. During the summer of 2018, after HABs left millions of pounds of dead fish and other sea life piled up in Florida’s coastal towns, Governor Rick Scott declared a state of emergency."

Weiss notes that on a global scale, "HABs are exploding. In recent years, toxic blooms have started to occur in places where they’ve never happened before, and during more months of the year. The expansion of HABs is linked to rising sea temperatures, but pollution, the dumping of ballast water from ships, and the transplantation of shellfish stocks may also play a role."

She writes about the consequences of different red tides proliferating globally, "Members of the Alexandrium genus produce one of the most powerful neurotoxins on Earth, a chemical called saxitoxin that is so noxious a single sand-sized grain can kill eight people. The poison blocks sodium-ion channels in the brain, quickly paralyzing the respiratory system of its victim.

"The most notorious impact of HABs is paralytic shellfish poisoning, or PSP, a disease that can kill a healthy adult with just one tainted mussel. It’s the algae that cause PSP — called Alexandrium — that preoccupy Wright," she says, "Fifty years ago, few places in the world were affected by Alexandrium. Today, a global map of PSP outbreaks looks like a case of measles."

This algae has been floating around looking for something to grab since the dinosaurs, and this particular species presently lurking in Alaska is estimated to have emerged 77 million years ago. She says it was first identified in Egypt. Weiss, who lives in Alaska, says the first historical reports of HABs in Alaska occur in 1799 when a large number of Indigenous hunters died eating infected clams.

The scientist consulted by author Weiss stands apart in his opinion that HABs are proliferating on a world-wide scale. He believes they are the cause all kinds of unreported ills as well. Science is proving to have growing knowledge of climate change that will be altering the survival prospects across the spectrum of ocean science.

There are plenty of HABs to go around with or without climate change, and ocean currents occur in unusual variations, like the El Nino on the west coast, and the Caribbean heat flowing up the north west Atlantic coast.

Cermaq Canada's mortality event happened due to levels of harmful algae - Chaetoceros convolutus and Chaetoceros concavicornis. The company is able to report continuing decreases of algae in both Herbert Inlet and Ross Pass, for Cermaq is engaged closely monitoring HABs after outbreaks descending on three farm sites this fall.

On Nov.26, 2019, in Tofino, B.C., Cermaq put out a news release that said although still detectable, the algae are not at levels that cause mortalities. “We first detected Chaetoceros convolutus and Chaetoceros concavicornis during routine water sampling on November 6th. These particular algae, even at low concentrations, can cause severe damage to the gills of our fish. The algae persisted at fairly high numbers until November 18, when we finally saw the concentration drop off,” says David Kiemele, Managing Director, Cermaq Canada.

“There has been quite a bit of misinformation around this event and we can’t emphasize enough, this was an unfortunate – but naturally occurring – elevated algae event. These mortalities are directly linked to the harmful algae becoming embedded in, and inflicting serious damage to the gills of our fish, which unfortunately, can be fatal. The mortalities are not related to any disease event as being shared on some social media sites.”

To support the overall welfare of fish at the farm sites, Cermaq says they delayed the start of mortality collecting and transporting to reduce stress on the surviving fish. Any activity on the farm system early on, would have created additional and unnecessary stress and potentially, additional mortalities.

“The delay in mortality collection did result in the breakdown of the muscle tissue of the earlier fish mortalities. When this occurs, you can see the protein breaking down and coming up as a surface sheen. This happened predominantly at our Binns Island site, which experienced the largest number of mortalities,” added Kiemele. “We have now collected and transported the mortalities away from the farms. They were collected using standard biosecurity procedures and have been taken to land to be used for rendering or fertilizer.”

At the time of the event, the Clayoquot Sound region had been experiencing substantial rainfall, resulting in a reddish-brown run-off into the inlets where Cermaq farms are located. There was also naturally occurring sea foam being seen in the Sound. "When large amounts of algae begins to decay and wash up on shore, the surf churns the organic matter up, resulting in the foam commonly seen along shorelines. It is not harmful and has been seen in the past in other areas along the west coast."

The last of the mortalities associated with the harmful algae have been collected and were removed from site on Nov. 22, 2019. Cermaq continues to provide updates to the Ahousaht First Nation, in whose territory these farms are operated, as well as through social media. https://www.cermaq.com