Jump to content

johng

Members
  • Posts

    10
  • Joined

  • Last visited

johng's Achievements

Junior Member

Junior Member (1/3)

0

Reputation

  1. I am lucky enough to spend a bit of time each year in South Island. It is not uncommon to see big eels when trout fishing in rivers of all sizes, even quite small streams. If one comes close by while you are wading it can give you a fright. They are huge, and not timid. A friend was cleaning a trout of about three pounds and a big eel gently took it away from him. I've never seen anybody fish for them. I'm not certain, but I think they might be protected. The biggest of all are said to be in the big hydo lakes, under the turbines. Apparently they just sit there chomping up chopped up trout and salmon. Reputed to get to 100ish lbs there. However, someone said earlier in this thread "I can catch brownies anywhere". Not like NZ browns you can't! This is sight fishing for big, wild, difficult, fish, and angling doesn't get much better.
  2. johng

    pressure

    Steve, I think scientific evidence is needed to prove H1.0 rather than the other way round. There is no obvious means by which fish can sense AP and, it seems, no published scientific findings that support the hypothesis. You might just as well ask me to prove that they are not picking up the shipping forecast on long wave Regards John
  3. johng

    pressure

    Steve W, I'm sure that fish can detect small changes in TOTAL pressure (of which atmosperic pressure is a tiny part), but as with your diver they use this information to monitor and regulate the depth at which they swim. They can't use the SAME information for weather forecasting. Over a long period of time on several of these message boards I have noticed that the proposition that they can detect changes in atmospheric pressure has become the received wisdom. I feel as though I have stumbled into a meeting of the flat earth society Regards John
  4. johng

    pressure

    Budgie, I have enjoyed this thread, it is certainly making me think! Sight is the most likely sense that would work. In an earlier message I mentioned the 'Red sky at night' old wives tale, and I have found the following explanation: 'The origin of the saying is unknown, although a form of it appears in the bible (Matthew 16:2-3). It has some basis in science and is a fairly good predictor of-though no guarantee-of weather at the mid latitudes in the Northern Hemisphere, where storm systems generally follow the jet stream from west to east. A red sky in the morning indicates a sun rising in clear eastern skies casting its rays on storm clouds approaching from the west. At night the clear sight of the red setting sun would tell a sailor that no storms are to the west' Fish have the observation skills and the long evolutionary timescale to make use of visual clues in the earths atmosphere. I am sure that there are many clues since changes in weather are preceded by visual changes. Regards John
  5. johng

    pressure

    It's interesting that nobody can show us one of the scientific studies mentioned by the two Steves that support the notion that fish can detect changes in atmospheric pressure. Surely such an unlikely result would be widely published? The Cartesian diver works very well with big changes in atmospheric pressure, but if you want to know how it works in the real world, try it again without a top on the bottle. It's a shame that the thread is changing direction into a general discussion on whether fish can detect or predict changes in weather (I certainly accept that they can ) It would be good to nail the pressure question and then we could figure out a more plausible explanation
  6. johng

    pressure

    Just to take this thread a little further, it is worth having a look at the following site: http://www.sengpielaudio.com/calculatorPressure.htm I'm not very technical, but... The total pressure exerted on the fish will be the sum of the water pressure above it and the air pressure above it An atmosphere represents about 30 feet of water pressure and a millibar represents about 30 feet of air pressure The conversion ratio between them is 0.0009869 or about one thousandth. I think. So...If a fish has a sort of altimeter to measure changes in pressure and it moves up in the water column by one foot (a small change) that will be equivalent to the air pressure changing by (1 x 1000/30)=33 millibars (a massive change) I suggest that it is only plausible to argue that fish can detect changes in air pressure if you assume that they are completely immobile for a long time, and that the water level does not change at all.
  7. johng

    pressure

    Hi Budgie, Birds are very good at detecting changes in air pressure. You only have to watch a buzzard centering into the best lift in a thermal to see that. They have simple but very sensitive and well understood mechanisms for being able to do that. You therefore might possibly be able to persuade me that were a bird to sit motionless for long enough it might be able to dedect a change in barometric pressure. But probably not. When the barometric (air) pressure changes there is no way that this can be detected by a moving creature immersed in water. I am as certain as you that fish are aware of changes in the weather and may indeed be able to anticipate changes, but another explanation is needed. For example seafarers and farmers have always been able to foretell changes in weather based on the 'look' of the sky. Red skies and so on. I believe that, during their evolution, fish could well have learnt some rules based on what they can see that enable them to provide some form of forecast. Regards John
  8. johng

    pressure

    Fish cannot deduct changes in barometric pressure. If a fish moves and inch up or down in the water column that is equivalent to a massive change in barometric pressure. They are of course sensitive to other changes in the weather such as temperature, cloud cover, rain and visibility
  9. I had a great day catching perch on floatfished lobworm from a small stream. About ten altogether with a couple of twos and one three (pb). However I was lost several of the bigger fish close to the net, when they fell off the hook. I was using barbed Drennan super specialist #6, and wondered if they are sharp enough or fine enough. Any recommendations? Thanks
  10. johng

    Vitalin

    Lee, Just wondered what your think was on putting the vitalin thro' a food processor for barbel.? I find it works pretty well just soaked whole Cheers Jon {2008 Editor's Note: to view Vitalin for sale, please click here}
×
×
  • Create New...

Important Information

We and our partners use cookies on our website to give you the most relevant experience by remembering your preferences, repeat visits and to show you personalised advertisements. By clicking “I Agree”, you consent to the use of ALL the cookies. However, you may visit Cookie Settings to provide a controlled consent.