I find it very hard to believe I haven’t written about salmon yet. I grew up on the Pacific coast of BC, so learning about salmon and eating salmon were a huge part of my childhood. Yet somehow it’s taken me until post 429 to write about these amazing fish. Maybe I’ve avoided writing about them because thinking about salmon makes me so hungry. I could really go for some sushi right now…
Salmon belong to the family Salmonidae, which is comprised of 66 species, and includes trout, whitefish, char, and what we think of as true salmon. Commercially important salmon belong to two genera, Salmo (Atlantic salmon) and Oncorhynchus (Pacific salmon). There is only one species of Atlantic salmon, which is found on both sides of the north Atlantic Ocean and its tributaries. Pacific salmon, of which there are six species, have a more varied range, but are also found on both the western and eastern sides of the north Pacific. Some populations of Atlantic and Pacific salmon are landlocked, meaning they live their entire lives in freshwater and do not migrate.
Salmon range in size, depending on the species. The smallest of the commercially important species is the pink salmon, which measures an average of 50 cm and reaches maximums of 76 cm. Atlantic salmon are the largest salmon, reaching maximum lengths of 150 cm. The largest of the Pacific salmon are Chinook salmon, which also can get up to 150 cm in length, but have a lower average length than Atlantic salmon.
Salmon are famous for their life cycle, and the arduous journeys they make both as young salmon and then as mature, reproductive adults. It all starts with eggs being laid in freshwater, usually in high mountain streams. Here the eggs are relatively safe from predators and can hatch into fry, which then develop into parr (don’t worry, their won’t be a quiz at the end of this post). Parr are easily identified by camouflaging stripes that help keep them safe as they develop into smolt, a process that takes six months to three years.
Smolts are bright silver, and undergo physical changes which allow salmon to survive in salt water. At this time the salmon migrate to the ocean, though the smolts spend some time in brackish water to acclimatize themselves with the ocean water. Once the fish are in the open ocean, they develop into adults, spending between one and four years in the ocean.
As the fish get ready to spawn, they undergo more changes. Some species develop humps, canine-like teeth, or curved jaws. All species change colour, from silver-blue to a darker colour. In sockeye salmon this colour change is extremely pronounced, as they turn bright red.
While they are experiencing these changes, the salmon have to travel. The journey upstream is a long and difficult one for most salmon. Salmon can travel over 1,400 km, climbing 2,100 m, against the current, and often over rapids. Most salmon return to the exact stream in which they spawned, and are able to navigate home thanks to their memories of certain smells.
The distance and height aren’t the only thing that make spawning salmon’s journey difficult. Lots of animals capitalize on the salmon run, feasting on the frantically migrating fish. Grizzly bears in particular are well-known for feeding in streams while salmon spawn. While this is bad for the fish, it’s actually good for the forest. Salmon bring in nutrients from the ocean, and when the bears catch the salmon and leave their decaying carcasses on the forest floor, the nutrients can enter the forest ecosystem. Nature is truly wonderful, isn’t it?
Female salmon use their tails to make small depressions in the streambeds where they lay their eggs. Up to 5,000 eggs can be laid in a single depression (known as a redd, for some reason). Male salmon then approach the redd and deposit their sperm on top of it, after which the female covers it with gravel. This process is repeated, as many as seven times. Once salmon have spawned, they are called kelts, just to keep things as confusing as possible. Almost all adult salmon die after spawning. Only 2 to 4% of a Atlantic female salmon survive to respawn; in all Pacific species they pass away within days or weeks of spawning. The life of a salmon is a hard one.
In terms of wild salmon populations, they are doing well in some areas and not in others. Atlantic salmon have been in decline in recent years, and some populations of Pacific salmon are declining. Much of what effects wild salmon survivability occurs in the freshwater streams in which they hatch and grow; siltation, temperature increases, oxygen decreases and loss of vegetative cover are all caused by humans and negatively effect growing salmon. Farmed salmon have also become increasingly available, but I’m not going to get into the debate about farmed vs wild salmon. I’ll just end with this: salmon are delicious, but I really hope we don’t eat them to extinction, because they are super cool fish.
Cover image by NASA Goddard Photo and Video, CC BY 2.0, via Wikimedia Commons