Castable thermometers?

robtherake · Jan 26, 2014

It was mentioned that the best way to find the position of underground springs - possible winter hotspots - was to observe which areas froze last in cold weather.

I guess the only way to do that under more normal conditions, apart from observing for signs from fish, is by thermometer. I remember reading something written by one of the old-time greats - maybe Walker, talking about the perch at Arlesey - mentioning the use of a caged thermometer to map temperature variations.

It should even be possible - in conjunction with a hefty float - to check the difference at various depths, although I'm now straying from the point a little.

What I'd like to know is if anyone on here has used one, how accurate they are and whether there's a particular type or brand to look for which is more reliable than any other.

tiinker · Jan 26, 2014

I have several thermometers Ruben Heaton do a good shielded one they also do a depth gauge . I think it would be a very time consuming job to do what you are saying wind direction and the strength of the wind ie. under tow effecting the water layers and thermocline . If the lake is not to deep and you can get permission to get in it wearing a proper life jacket you can often find the warm areas with your feet and legs. Good luck.

keora · Jan 26, 2014

I use a cheap glass thermometer mounted in a plastic frame. I bought it from a pet shop or a supermarket. I put it in the landing net and immerse the net in the margins.

To cast the thermometer, you could wrap some lead strip around the frame, drill a hole in the frame and attach a split ring and a swivel to it. Then clip it to a link swivel on the reel line.

To check temperatures at the lake bed, cast out, leave it minute, reel quickly back and take the reading.

Water temperature on a nearby river was 6 degrees C last Thursday. I'm not sure how much greater the temperature of water from a spring will be when compared to the temperature of the lake. There might be only a small difference.

I'm not sure it would be worth attaching the thermometer to a big float to find the temperature at various depths in winter. There can be a top layer of warmer water in summer on sunny days. In winter, water is less likely to stratify until temperatures fall to 4 degrees or below. At this temp, the structure of water changes, colder water is less dense and it floats to the top.

nicepix · Jan 26, 2014

The trouble with casting a thermometer into the depths is that by the time you've retrieved it the reading will have altered.

When I'm looking for new swims I use an infra red thermometer that I bought to assist in finding cannabis set ups. I got mine from a Chinese site but I notice that they are now more widely available at around £25. In fact my local Lidl had them last week.

Dependent on conditions I trust it to around 20 metres out into open water, the higher your viewing position the better. Mostly though I use it to quickly check the surface temperature of the water close in as I go round the lake to see how the wind affects the water. Also, where streams feed into rivers or lakes it lets me know what if any variances there are. Where a warmer stream enters a lake or river is usually a good place to fish in winter.

None of this is any good for open water or mid stream on large rivers though. For that you have to get afloat.

NB: An interesting alternative use for this type of thermometer (other than scaring kids away pretending its a Taser :wh ) is to locate areas of heat loss in your house.

tiinker · Jan 26, 2014

nicepix said:
The trouble with casting a thermometer into the depths is that by the time you've retrieved it the reading will have altered.

When I'm looking for new swims I use an infra red thermometer that I bought to assist in finding cannabis set ups. I got mine from a Chinese site but I notice that they are now more widely available at around £25. In fact my local Lidl had them last week.

Dependent on conditions I trust it to around 20 metres out into open water, the higher your viewing position the better. Mostly though I use it to quickly check the surface temperature of the water close in as I go round the lake to see how the wind affects the water. Also, where streams feed into rivers or lakes it lets me know what if any variances there are. Where a warmer stream enters a lake or river is usually a good place to fish in winter.

None of this is any good for open water or mid stream on large rivers though. For that you have to get afloat.

NB: An interesting alternative use for this type of thermometer (other than scaring kids away pretending its a Taser :wh ) is to locate areas of heat loss in your house.

I understood that they only give the surface temperature when I enquired about them at Maplin electrics they are doing a model for£19-99

no-one in particular · Jan 26, 2014

I imagine getting the temps from a wide range of water depths and distances would be pretty difficult for all the reasons suggested. Especially to find a hot spot in a large area. As to thermometers, I have broken quite a few so, I go for a cheap one from a pet store. They seem accurate enough for my purposes. I wrap it in a 6 inch section of large garden cane that I split in two. I place the thermometer in the two halves leaving the gauge showing and put some whipping around to hold it together. A arsely bomb attached one end and a split ring attached the other with the help of a couple of small holes drilled in the ends. I have about 20ft of sea line attached to this. I can throw this out distant enough to get a reading, I have a big loop at the end which I just hook over a bit of vegetation and leave for 15 minutes. I pull it in quickly and read it. I don't think it has time to change as it is only out of the water for a second before reading. I have not broken this one for some time and cheap enough to replace if I do. Costs about £1.50 from a pet store. If pennies are an issue; this a good alternative.

mick b · Jan 26, 2014

Years ago, sometime in the 80s there was something called a Depth'o'Gauge, which measured water depth and tempreture if you lowered/cast it in.
I seem to remember seeing something similar in a tackle shop recently, but I go into so many I cannot remember which one

mg:

I don't reckon it helped me catch any more fish tho.

What I have used a great deal is an electronic thermometer, there is a type on the market that has a probe on a 5 metre lead and these are very accurate and waterproof.

An alternative is to use wildlife.
If your water is large enough birds will roost on it at night and they will ALWAYS sit where the water is warmest, an added plus is that birds defecate while they are roosting and fish will be under the roosting area in the morning, feeding on the bird excrement (but thats another story).

Weedgrowth is often another indicator of warmer water, often growing right over a spring because of the added nutrients and water flow, didn't someone previously advise fishing ontop of dead weedbeds/roots

Eg;
I once dug out a badly silted village pond and unknown to us the spring was right in the centre with a huge mass of weed growing ontop of it, this area was left until last and when the digger removed the first bucket of weed/roots the spring burst through so fast the driver only just managed to save the machine from being totally submerged

Or you've just got to pray for a freeze over

tiinker · Jan 26, 2014

mick b said:
Years ago, sometime in the 80s there was something called a Depth'o'Gauge, which measured water depth and tempreture if you lowered/cast it in.
I seem to remember seeing something similar in a tackle shop recently, but I go into so many I cannot remember which onemg:

I don't reckon it helped me catch any more fish tho.

What I have used a great deal is an electronic thermometer, there is a type on the market that has a probe on a 5 metre lead and these are very accurate and waterproof.

An alternative is to use wildlife.
If your water is large enough birds will roost on it at night and they will ALWAYS sit where the water is warmest, an added plus is that birds defecate while they are roosting and fish will be under the roosting area in the morning, feeding on the bird excrement (but thats another story).

Weedgrowth is often another indicator of warmer water, often growing right over a spring because of the added nutrients and water flow, didn't someone previously advise fishing ontop of dead weedbeds/roots

Eg;
I once dug out a badly silted village pond and unknown to us the spring was right in the centre with a huge mass of weed growing ontop of it, this area was left until last and when the digger removed the first bucket of weed/roots the spring burst through so fast the driver only just managed to save the machine from being totally submerged

Or you've just got to pray for a freeze over

Ruben Heaton do a depth gauge they also do the thermometers you mention but you can get cheaper model in the likes of maplin. I use one for observation when fishing especially on long stints for cats with the wind pushing into my bank.

Ray Roberts · Jan 26, 2014

tiinker said:
I use an infra red thermometer that I bought to assist in finding cannabis set ups.

Why not just grow your own, like the rest of us.

Castable thermometers?

robtherake

Well-known member

tiinker

Banned

keora

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nicepix

Well-known member

tiinker

Banned

no-one in particular

Well-known member

mick b

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tiinker

Banned

Ray Roberts

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