Do Salmon Return to the Steam Where They Were Born to Spawn?
edavidoff: First, I don’t think it’s possible to put some sort of a tag on a baby salmon because they are so small. Second, because of the high mortality rate you’d have to mark hundreds of them to have a chance that some will survive to breeding size. Third, you’d have to find the marked salmon among the hundreds that come to spawn in the stream. And fourth, you’d have to be able to prove that none of the marked salmon went to a different stream. You’re wrong about the impossibility of tagging and tracking salmon. The Atlantic Salmon Federation, an NGO, does this yearly, and has for about a decade. Here’s a study regarding the rate of return to natal streams of salmon after the Exxon-Valdez oil spill; it samples 288,492 fish. It clearly isn’t a problem sampling large numbers of fish at at time. All sources seem to indicate that it is indeed true that salmon return to th
See also thermal marking on otoliths. Related metafilter thread here. 100% of hatchery salmon can be marked using thermal marking. Hatchery salmon are often penned and released at a variety of streams in Southeast Alaska. As pointed out up-thread, not EVERY returning salmon comes back to exactly the same stream, but the proportion is pretty high. Different species of salmon also have different “fidelities” to their natal streams. I believe king and silver salmon return in higher proportion to the exact stream where they hatched, pink and chum salmon less so, but I can’t find a citation for that right now. It’s something that we talked about in the hatchery lab that I used to work in, tho.
I’m interested that you posted this question absolutely sure that there’s some weird salmon-myth conspiracy going on among scientists, that scientists get a kick out of perpetuating false, undocumented, or unproven ideas (myths!) among the general public, and that people tag salmon only in ways that fit with your pre-existing notions.
This paper, “Recent Advances in Biotelemetory Technology on Salmon Homing Migration” by Hiroshi Ueda, is helpful on the finer points of how salmon tracking is done: Three biotelemetry instruments (ultrasonic transmitter,electromyographic radiotrasmitter, and micro-datalogger) havebeen applied to investigate homing migration of anadromous chumsalmon (Oncorhynchus keta) from the Bering Sea to Japan as wellas lacustrine sockeye salmon (O. nerka) and masu salmon (O.masou) in Lake Toya, Japan. Since each instruments has greatadvantages and/or minor disadvantages, we are developing an automatic salmon-tracking robot boat… That’s right, an automatic salmon-tracking robot boat.
There are plenty of salmon who only pinpoint the area. They crowd the mouth of Gold Creek every summer, a stream that hasn’t hosted a salmon population in years due to the swift artificial stream bed. Alaska’s department of Fish and Game employs a small army of people every summer to track salmon populations both coming and going from fresh water.
