Quizzes & Puzzles5 mins ago
Salmon
Is salmon classified as "seafood"? I think so, but someone said that's wrong, because salmon is farmed in rivers.
Answers
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For more on marking an answer as the "Best Answer", please visit our FAQ.Salmon you buy can come from three different places:
- Wild fish caught at sea
- Wild fish caught in a river
- Farmed fish kept in a net enclosure in the sea
Trout are farmed similarly, but in ponds. Neither in rivers.
Tinned salmon is of various Pacific salmon species usually caught at sea. Atlantic salmon is a single species, but can be from any of the three sources, but usually the last. Wild Atlantic salmon are under severe pressure from overfishing and pollution.
Wild trout, char and salmon are amongst the most delicious fish there are. However, in my opinion farmed trout and salmon are often not worth having -- bland, tasteless and usually not fresh -- I'd rather have plaice.
The other problem with farmed fish is the enormous impact on the environment. Firstly they are fed on fish-based pellets, which are made from indiscriminately caught sea fish. It takes ten times the amount of feed-fish to produce the farmed fish, so this is very wasteful. Secondly the pesticides, waste feed and droppings destroy the seabed around the sea-farm or pollute the river downstream. Thirdly escaped fish interbreed with wild fish, wiping out highly adapted local varieties -- so pollution is genetic as well as chemical.
Much the same goes for farmed shrimps and prawns -- except they are grown in farms created by destroying mangrove swamps.
Buy fish from sustainable wild sources instead!
Neesy -
There are quite a few other fish which do as salmon do (live in sea, breed in freshwater). For example, sea-trout (sewin), char, sturgeon, shad, sea lamprey. They are called anadromous species. Most (including salmon) spawn in the river they hatched in, even if meanwhile they've been across the Atlantic and back.
A few fish live in freshwater and breed in the sea (catadromous) -- the eel is the main one of these, and also some flounders.
Rather more kinds live and breed in the sea, but sometimes go up rivers a little way -- sea-bass, mullet, pipefish etc.
Very few fish can switch casually from freshwater to seawater and back -- they must take a while over it while their kidneys adapt. This is because seawater is saltier than their blood, but freshwater is much less salty than their blood. As seawater passes through their gills, the water is "sucked" out of the blood (by osmosis), but if it's freshwater the water is sucked into the blood instead.
The kidneys therefore have the opposite job to do in seawater and freshwater -- keep water in or get rid of lots of it. Sea-fish drink lots of water, produce small amounts of concentrated urine, and excrete excess salt from special glands in the gills -- freshwater fish don't need to drink anything much, and produce lots of dilute urine all the time.