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Hi. I apologise if this is under the wrong category.

I was researching on red-eyed tree frogs one day and came across a hint to see more of them. It said use red lights to see your frog because they cannot see the red wave lengths and such. I got thinking, I can never see my bumble-bee cat nor my zamora cat because they are nocturnal. If I switched to red lights, will the catfsihc ome out during the day so i can see them?

Yes, catfish eyes are insensitive to red light, just like many other (all?) fish. However, I wouldn't recommend switching from normal wavelength light bulbs to red light during the day, as this could throw your fishes' night and day cycle off (they would feel like it was dark 24/7). What you can do is put a red light over the tank the goes on at night. This will allow you to observe your fish going about their natural nocturnal ways, and they will be none the wiser that you are watching.

Rusty

Hi,

Can fish see red lights? The very same question hit my mind some time ago.
Im no expert on this, so if im wrong somewhere someone please correct me.

If I switched to red lights, will the catfish come out during the day so i can see them?

I don't know if they will come out during day his way, but they will most likely be able to see it. ;)

In short:
What colors fishes are able to see differs greatly between species and seems to correlate most time with the environment the species comes from.
Some fish and especially some freshwater fish like cyprinids and (all?) catfish seem to be able to detect red light with their photopic visual system (see "long story") just as good as you and me, if not even better. Nicol even quotes "the glass catfish" as a species that has one kind of cone that absorbs at ~600nm (which is red light) max.

Long story (visual pigments of fish):

Mainly from Nicol, "The Eyes of Fishes", Oxford Science Publications, 1989

Scotopic system (rods, low light visual system):

Fishes have two different types of visual pigments in their rods: Rhodopsin and Porphyropsin. Both have similar wavelengths absorption maxima. Rhodopsin at ~500nm, Porphyropsin at ~523nm.
If you provide low monochromatic light at ~600nm (which should be red),the Absorbance of Rhodopsin has dropped to ~0, the Absorbance of Porphyrhopsin is at ~30%. So the fish should see little-nothing. Interestingly this seems to depend on the origin of the fish. Teleosts have both kinds of visual pigments, but there is a difference in the amount of each pigment:
"In a large sample of freshwater fishes, rod rhodopsin occur about as commonly as porphyrins, but there is a distinct differende in the distribution of the two pigments between freshwater teleosts of tropical and temperate zones. Either pigment is present to an equal extend in troical freshwater species, whereas porphyropsin is more common in temperate zone species. The higher occurence of porphyropsins among the latter group of fishes could be related to the presence of more light of long wavelengths in high latitudes" (From Nicol)
So at a wavelength >~630nm the absorbance of both visual (rod) pigments has dropped to zero.

Photopic system (cones, color vision):

Again from Nicol:
"Examination of many teleosts has shown that the umber and spectrum location of the visual pigments and the combination of visual pigments found in the double cones vary greatly from species to species, and are apparently related to the photic environment of the fish. The glass catfish has one kind of cone that absorbs long wavelengths. Many fishes ore dichromatic, have little sensitivity to long wavelengths, and possess blue- and green-sensitive cones for example the weever fish"..."The eel Anguilla has two kinds of cones that are respectively blue and yellow sensitive; the perch has blue-sensitive single cones, green-sensitive single cones, and identical double cones; the walley has green-sensitive single cones, and red-sensitive identical twin cones"..."Cyprinid fishes are tri- or tetrachromatic (for cones); for example the ugui miniature single cones are ultraviolet sensitive, small singles are violet sensitive, medium singles are green sensitive, short doubles are green sensitive, and long doubles are red sensitive"
Later on Nicol writes: "Fish from fresh water, more transparent to red light, have cones more red sensitive than fish from blue-green coastal waters"

Greetings,

Achim

well, it just took me too long to write my previous post ;)

Yes, catfish eyes are insensitive to red light

Not that i doubt you Rusty, but do you have any citation for that? Because like posted above, from what i read till now they seem to be able to detect red light.

Achim

I could very well be wrong This "fact" may just be an urban legend of sorts, but I have heard it repeated as fact on several occasions.

This paper may shed some light (pardon the pun) on the situation:
Peter C. Gehrke, Influence of light intensity and wavelength on phototactic behaviour of larval silver perch Bidyanus bidyanus and golden perch Macquaria ambigua and the effectiveness of light traps, Journal of Fish Biology, Volume 44, Issue 5, May 1994, Pages 741-751.

The abstract:

The author wrote:Larval golden perch, Macquaria ambigua, and silver perch, Bidyanus bidyanus, were exposed to light gradients in wavebands centred on 400, 496, 601 and 695 nm at nominal quantum irradiance values of 0·1, 1·0 and 10mol m-2 s-1. Silver perch larvae displayed stronger phototactic behaviour than golden perch, and both species were most responsive to light in the 601 nm waveband. The intensity of phototactic responses in both species was greater at higher irradiance levels. Enhanced responsiveness to longer wavelengths reflects possible adaptations to life in turbid habitats where the underwater light field is dominated by yellow/orange wavebands.

At night, traps fitted with 12 h yellow lightsticks attracted more golden perch larvae than traps with blue, green, orange, red or no lightstick. The efficacy of yellow lightsticks may be due to yellow/orange wavebands not being attenuated under water as rapidly as blue or red wavebands. Yellow lightsticks also emit a greater intensity of light over a longer time than other colours tested, which may have increased the effectiveness of yellow traps. Light traps were ineffective during the day.

This argument makes sense, but it just maybe that fish have decreased sensitivity to color in general. I remember reading a paper on this theory recently. I will try and dig up the citation.

Rusty

Found it:

Andrea Krauss and Christa Neumeyer, Wavelength dependence of the optomotor response in zebrafish (Danio rerio), Vision Research, Volume 43, Issue 11, May 2003, Pages 1275-1284.

The abstract wrote:The action spectrum of motion detection in zebrafish (Danio rerio) was measured using the optomotor response in the light adapted state. The function has a single maximum at 550â??600 nm, and is similar to the spectral sensitivity function of the L-cone type in the mid and long wavelength range. At shorter wavelengths the values of three of the five fish tested are lower. As in goldfish [Vis. Res. 36 (1996) 4025], the result indicates a dominance of the L-cone type with an inhibitory influence of M- or S-cones. Experiments with a red/green striped cylinder showed that the optomotor response was at minimum whenever the L-cone type was not modulated by the moving pattern. This demonstrates that motion vision in zebrafish is "color blind", using mainly one of the four cone types probably involved in color vision.

This deals with cyprinids, which are closer to catfish than perch

Rusty

I find that a light on a dimmer switch turned just barely on works well.

i have tried several types of red lights with my catfish and they have clearly noticed and fled from all but the lights/flashlights that used red leds as a light source.

Lol. thanx guys, but uh, what does insensitive mean? And yes or no, can south american catfish (bulmble bee cat and zamora cat) see red lights. If so I will get red lights to turn on at night. Thank you.

This probably doesn't help much but our spilo piranha is very shy so we use a red light over the tank and he acts like he's none the wiser.

Actually that does help a bit because I know Pirhanas don't like bright lights. Well I got the red lights anyways and will use them at night. Thank you for all of the very fast replies!

Well I went and bought two incandescent (I think Hagen) Red Show lights bulbs for the tank. I sat there for about 1 1/2 with all the lights off, at night, but the red lights on in the one tank. For some reason every fish still acted the same. None of my nocturnal fish came out (except my pleco wjo roamed around once). Even when I put food in for the bottom feeders, the other fish (I have 2 silver dollars, a female fancy guppy and a marbled hatchet) saw and responded, and ate the food. For a test I turned off the lgihts completly for 5 minutes. When I turned the red lights back on, both of my catfish were out, but immediately raced back into their hiding places. So it seems they somehow still can see red light. I don't get it! Although I fish did seem much more relaxed than usual. But anyways I just wanted to tell everybody this. I don't know if I got the wrong lights or what but it didn't seem to work. I'll try it again tonight.

2 things come to mind.

1. The two bulbs are just too bright. If its bright enough, I'd assume just about anything could see it. Try and work with one, or put them on the otherside of the room. Dimmer is still better.

2. This goes along with BK's post. Incandecent red lights, are not (apparently) a very pure red light, and still contain a bit of everything. The LEDs should be a much "purer" red, and less likely to arouse suspicion of the fish.


Since all your fish are acting the same way (ie its not only a very photophobic doradid doing this), I think your lights are just too bright!

In my experience (and yes, I've tried it) catfish and many other tropical fish can and do see in red light.

Short answer, NO it doesn't work.

Well, the theoretical question would be: Can catfishes see red light? or, How sensitive are catfishes to red light? Since this could vary for different fishes.

But the practical question is: Does (dim) red light bother nocturnal catfishes? Many people seem to have had success with using dim red light for night viewing. Maybe they can see it just fine, but it doesn't bother them as much. Maybe red light is easier for us to see by when the light is dim. There could be another answer besides "they don't see red light"...

I agree with everybody. I thinkt he lights are indeed way too bright. What is LED light? I only know them by little tiny lights that are in game boys n such. Lol. But yes, it seemed all fish responded to the red light but yet seemed much more comfortable when ti was on. I just need a good way of viewing my catfish because I don't even no for sure if my Zamora cat is eating yet! He is very new, maybe 4 days old or so. I will try to dim the lights. But it got me thinking again. What about black lights?

Black light is full of UV, I would be worried about damaging the fish, esp the eyes.

Yea, I understad where your coming from. Well thank you for all of the replies. I will post something if I find a good way to see nocturnal catfish. Thanx again!