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www.ecologyalaska.com 

Trivia Question of the Week

We learned last week that Pacific salmon can grow to very large sizes when they spawn, but how do they know where to spawn?

If Pacific salmon spend most of their lives in the open ocean, how do they find their natal streams (the streams in which they were born) when they return to freshwater to spawn?

Hint #1: Planetarium studies have indicated that some species of bird rely on celestial navigation, orienting themselves based on the location of specific starts in the night sky. But since salmon can't see the stars, this isn't a tactic they can utilize.

Hint #2: Birds and salmon do have a navigation technique in common, though. It's the same way many animal species, from bats to sea turtles, find their way.

Hint #3: Scientists believe that salmon use not one, but two navigational aids to return from the ocean to their natal streams.

Hint #4: The technique for traversing ocean currents to find their way to freshwater is thought to be different from the method salmon rely on in the streams themselves.

Hint #5: You may think Fido is good at sniffing things out, but he can't compare to a Pacific salmon.

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Photo credit: Natalie Fobes

The two primary navigational aids salmon rely on are magnetism and scent. When salmon are in the open ocean, scientists believe they travel primarily by orienting themselves with the earth's magnetic field, much like many migrating species, like sea turtles, birds, and bats. Once they reach freshwater, however, scent plays the dominant role in guiding salmon travel. Young salmon migrating out to sea, known as smolts (pictured above), imprint different scents from their environment as they travel downstream. This allows them to create a memory bank of scents, which they later can use as a scent-map of sorts to guide their return to their birthplace as adults.

Public talk tonight (1/17) at the Santa Cruz Natural History Museum

If you're in the area, just a heads up that Rachel and I will be giving a public lecture tonight to the Santa Cruz Bird Club in the Natural History Museum. All are welcome to attend and the talk starts at 7:30PM!

Eagle Update

The past couple weeks have seen few changes in the places our GPS tagged eagles have been traveling. The females are still seemingly content to stay on the Chilkat, while the males are still southward in and around Prince Rupert.

The adult female, 3E, and the immature female, 4P, are both right around the area we initially caught them:

3E

4P

The mature male, 3C, is still moving around a bit, bouncing eastward, then westward again, then a bit to the southeast, though he is still near Prince Rupert. You can see pretty clearly on this image how he has been following waterways closely as he travels.

3C

The immature male, 2Z, has now been in Prince Rupert for more than a month. This may be where he stays until spring. It seems 2Z is spending time feeding at a landfill near the city. Since he is a younger bird, he may not be able to compete with other eagles for better food sources (e.g. fish), or perhaps his hunting skills aren't quite up to scratch. Whatever the reason, doesn't appear to be following the salmon, but rather, the dump truck.

2Z

In the upper right hand corner of the photo above, you can see a little portion of 3C's track, where the two birds were near one another for a short time.

Trivia Question of the Week

This week's trivia question is a little fishy:

How big are Pacific salmon when they spawn?

Hint #1: Trick question, right? There are five species of Pacific salmon that spawn on the west coast of Canada and the US: King, Sockeye, Chum, Pink, and Coho. Different salmon species are different sizes. Kings, for example, typically range from 10-50 lbs (4.5 - 23 kg), whereas Pinks average only 5 lbs (2.3 kg).

Hint #2: Not only are different species different sizes, but older fish are typically (but not always) larger than younger fish.

Hint #3: To make things even trickier, not all salmon are the same age when they spawn. Sockeye can be anywhere from two to six years old when they return from the ocean to freshwater streams for spawning.

Hint #4: With all these variables, perhaps a better question would be, "How large do the largest, oldest Pacific salmon become before spawning?"

Hint #5: King salmon are called "kings" for a reason.

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The largest King salmon on record was a caught by a commercial fishing operation near British Columbia in the late 1970's. This monster weighed in around 126 lbs (57 kg)! Several King carcasses weighing 100 lbs or more have been found on spawning grounds. The fish pictured above was located by biologists of the California Department of Fish and Game during a salmon survey on Battle Creek. Measuring in a 4.5 ft (1.4 m) long and around 85 lbs (38.5 kg), this King was one for the record books in California.