Sunday, March 8, 2009

Jumping Jack Flash

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When I was paddling the other night I noticed there were more fish jumping than usual. The line from an old Stones record came into my head



Jumping Jack Flash ~ It's a gas, gas, gas !



But why do fish jump?


One reason fish jump is to chase insects skimming across the surface of the water. Perhaps at sunset when the sun is low on the horizon the insects are more easily seen and attract the fish.


But we often hear fish jumping at night. What we hear is the thwack of the belly flop they make when re entering the water. What do they see at night?


Another reason fish jump is to escape predators. These jumps usually occur in groups of fish not individuals and the fish retain an upright posture and re-enter the water cleanly. Rule that theory out... Ours are noisy, inelegant jumpers.




Photo - permission to use kindly given by Robert Harrington




A new theory that explains why these fish in our river, which are mullet, jump proposes that they jump to fill the pharyngobranchial organ, an area at the back of the throat, with air. The trapped air allows them to remain active in water of low oxygen concentration for about five minutes. Mullet often feed in bottom sediments which have low oxygen concentration and the number of jumps is correlated with the level of oxygen in the water. So, as Mick said, it could be all about gas...


Whatever the reason is for this phenomena, the sight of jumping fish is one of those things that makes you stop for a moment ... and wonder ... and be filled with awe... ~ and that is a good thing ...



Jumping jack flash, its a gas
Jumping jack flash, its a gas
Jumping jack flash, its a gas
Jumping jack flash, its a gas
Jumping jack flash


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13 comments:

  1. It was something we had wondered about. The kids have asked me on occasion - now I know! Thanks.x

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  2. Hi Natalie - it sounds quite plausible to me...

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  3. lovely post again Delwyn and thanks for the info ..now I don't have to wonder why they jump

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  4. Mona, Its good to learn new theories...they are evolutionary

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  5. Me, again. I forgot to tell you how much I enjoyed your comments on Janet Frame! My interest in her poetry came from seeing Campion's film on her life, about 10 years ago, or so.

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  6. Thanks for visiting my blog. Now, I have the opportunity to enter another world of poetry and art and numerable reasons for fish-flight. I want to add another reason, for the fish that return up rivers to spawn: they must jump over shallow areas or even dry areas to remain in the water, to remain swimming toward the end.

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  7. Obviously salmon jump just to get up stream to spawn. I had always thought that another reason for fish to jump is to dislodge parasites. Sometimes when I watch birds in the sky - especially awallows - I have the impression that they simply enjoy flying. Maybe fish enjoy jumping and showing off to their buddies below. Hey nice one Fishface!

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  8. Willow, Good morning from the future....Yes I saw the film too...

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  9. Lakeviewer: welcome to you. The fish in my river are mullet and the theory applies to them in particular, but perhaps to other murky low oxygen bottom feeders too...Thanks for your comments...

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  10. Hello YP, Yes I read about the parasites too...I was watching huge flocks of seagulls when I was paddling at the river mouth a couple of nights ago. The flock broke into 3 parts and performed an amazing aerial ballet, would reform then break away again creating waving patterns that covered the sky. I was mesmerized... And as you say it looked like flying for the sheer joy of it...

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  11. Delwyn your picture is fantastic. I love the colours and the use of the circles.

    xoxo

    Renee

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  12. Renee - thanks for those comments I am no artist but I always say "i can cut and paste and dab a bit of paint around" and I love playing

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