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Below The Surface

Sunday, October 23, 2011

Time to Go Against the Flow?

Recently, economic woes around much of the world have blossomed into the Occupy Wall Street movement, making the evening news each night. People are taking actions, challenging others to join them and go against of flow of life as usual. At ECHO, one of our Atlantic Salmon is doing its own version of getting attention. Has economic unrest trickled down to our unpaid animal ambassadors?
video

One of our Atlantic salmon looks like it's doing a headstand while its tank-mates are swimming along in the usual way. What is going on & why?

As I had written in a previous post, animals will do seemingly odd things in captivity, and it is often helpful to be aware of the environmental cues available to the animal where it lives. Although no one can truly know what is going through an animal's mind at any given time, we can tap into our knowledge of the biology and ecology of an animal to develop a hypothesis (educated guess) about what is going on.

I know from both the video and seeing these animals live that the salmon doing the headstand is the largest salmon in the tank. I also have observed that there is a steady current that flows from the bottom to the top of the tank; this is where he or she does its thing. Look closely at the algae growing on the log:

video

I've never seen our friend exhibit this behavior in other parts of the tank where there is no current. Does this behavior make any sense in the context of what wild fish do?

The life of an Atlantic salmon in the wild starts in spring when a fertilized egg hatches from a nest created in autumn by an adult female in a gravel bed in a fast-flowing part of a river. After hatching it spends time in the safety of the gravel bed, living off of a yolk sac attached to its belly. Once this energy supply is gone, it moves up into the water column and spend 2-3 years as a river dweller, eating aquatic insects. By its third birthday, the young salmon move downstream into the ocean or large lake and switch their diet to small fish. As it grows and reaches maturity, the salmon will make spawning runs, traveling up the river of its birth in late October or November. Unlike the salmon species of the Pacific Northwest which die after spawning just once, Atlantic salmon spawn multiple times throughout their adult life, so long as they have the energy to do it.

What strikes me most about the Atlantic salmon's life-cycle is the undercurrent (pun intended) of flowing water throughout. They are powerful swimmers that seek the current of flowing rivers when their body size, energy reserves, and environmental cues indicate that all systems are go for spawning. At ECHO, the temperature cues for our fish do not exist; the Atlantic salmon and lake trout tank is a fairly constant 55 to 59° F. The length of the day from our lighting is constant for these fish as well. So, the environmental cues that they might use to know that it is autumn are absent. However the flow of water in our tank from bottom to top is there and our fish are well fed. These conditions may have allowed our largest Atlantic salmon to become reproductively mature and the flow may be the only available cue to which she can respond. She swims vertically on a quest for spawning grounds. That is my hypothesis. Over time, more observations may change my mind and the hypothesis might change. If my hypothesis is correct, I will expect to see more of our fish exhibit this behavior as they get larger.

Want to see wild Atlantic salmon from Lake Champlain? As I write this, our local population of land-locked Atlantic salmon are making their way up rivers for spawning. If you visit the salmon lift (run by the U.S. Fish and Wildlife Service and Vermont Department of Fish and Wildlife), you may have a chance to see these creatures during their spawning run. The lift is located above Salmon Hole on the Winooski River, beside the Burlington-Winooski bridge. You can also watch a story about this from WPTZ's Conservation Correspondent, and ECHO's Conservation Education Specialist, Bridget Butler by clicking here.

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