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Food For Thought

By Ole's Hakai Pass Fishing Lodge, 🕔Fri, Apr 1st, 2016


Pacific salmon are one of the most important species off Canada’s west coast. Salmon are not only food and sport for human populations they are also a major food source for nearly all west coast mammals. Each spring an algae bloom occurs along the pacific coast that co-insides with the time the salmon make their way into the estuary waters to and get ready for their life at sea and is a major food source for the juvenile salmon at this stage of their lives.

Free floating algae, also sometimes known as phytoplankton comprise the microscopic unicellular algae and colonial and filamentous algae are the algae that occur in blooms. There are other forms of algae such as seaweeds also known as filamentous algae and macro algae that most often grow on substrate, and algae that grow as a film on rocks known as benthic, or algae that grows on plants that grow in the water known as epiphytic.

Though these algae blooms can occur any time of year but over last the last couple of years the bloom has had unusual characteristics producing areas where the bloom density is very high, especially off the waters of the US coast and a few areas on the BC coast. These were evidenced by satellite imagery from Nasa Earth observations and ocean sampling and testing during blooms and linked to the ocean circulation changes that happen when an El Nino occurs and may have been further influenced by the coinciding high pressure weather anomaly that caused the ocean’s natural circulation to shut down and the warm blob to occur in the middle of the Pacific Ocean.

In higher concentrations these heavy blooms can contain components such as Pseudo-nitzschia, a marine planktonic diatom , that can pose a health risk to those eating fish and seafood in the area because they produce a neurotoxic agent known as domoic acid. Also colloquially known as “red tide” this is different from the algae bloom that produces PSP or Paralytic shellfish poisoning which is caused by saxitoxin and affects all bivalves and molluscs, domoic acid can cause ASP or Amnesic shellfish poisoning, and accumulates in shellfish, sardines and anchovies that eat algae. When humans, cetaceans, seals and other mammals eat seafood contaminated by higher levels of domoic acid exposure to the biotoxin can affect the brain inhibiting the natural neurochemical processes and producing such symptoms as vomiting, nausea, dizziness, confusion, motor weakness, cardiac arrhythmia, short term memory loss and seizures. Severe exposure can cause death, though British Columbia has never recorded a human death due to ASP.

DFO (Department of Fisheries and Oceans) closed the affected zones to protect the human population and later lifted the closure as the bloom passed and the levels of toxicity abated. It is important to check for closures due to ASP, PSP and Dioxin contamination on the DFO web site before you fish, especially for shellfish. This did not help the marine mammals that still consumed the affected seafood and many with effects of the poisoning were found along the more affected US coastal areas. Domoic acid producing algae levels of this magnitude had never been recorded before on the west coast since the toxin was discovered and testing began in 1959. Happily the pacific currents are now returning to their normal patterns we will hopefully see the spring algae bloom levels return to normal feeding our baby salmon and other phytoplankton diners without causing biotoxic levels of Domoic acid that damage the marine mammal populations. Fisheries and Oceans has a very informative 5 minute video on ocean testing worth a view, you can follow the link above or click on the video below.

The first of the salmon have now come down river into the local estuary, not yet an inch and a half long and still sporting their stripes. They should soon be joined by others just about to embark on their ocean cycle before hopefully returning home to spawn and continue their cycle of life. Everything in nature is so interconnected that truly when a butterfly flaps his wings in the waters off Peru and Ecuador the effect is felt in the middle of the Pacific Ocean.

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