Pond Boss Forums INTRO Questions & Observations Fish turning really dark after being caught

This may sound odd to those of you that haven't observed it but for some reason when I catch fish in the northeastern part of the country they turn really dark on the stringer, in the fish basket, the cooler or when they expire. I've seen fish turn a little dark after they laid on the ice here but nothing like up there.

Here's a pic of some Maine fish that turned really dark after being caught. I got this off of an ice fishing website. The locals apparently are used to it and acted indifferent or that I was crazy when I asked them about it.




Anyone experience this? Could water chemistry or PH be a factor? The PH's tend to lean toward the acidic in the northeast with some exceptions. Alkalinity is usually pretty low also, at least in the lakes I fish up there on vacation.

Thoughts?

I don't know Cecil, but when we catch a smallie now and then out of the kickapoo creek behind the house, they get real dark bars on their sides. Same thing?. I've always wondered about that too. On another note, I was in the Navy on a small destroyer (440 foot Adams Class) and when we were doing drug ops down off Central America going real slow (3-4 kts) we used to hook into Mahi-Mahi now and then they would come out of the water all blue and yellow then the colors would fade soon as they died. Turned all gray.

Hey Cecil,

I have noticed similar dark coloring when icing down 'Kings' caught from Lake Michigan, could it be a Salmon thing?

I've noticed the opposite effect when transporting fish. Dark, beautiful fish are bleached and pale when arriving at the destination. I attribute this to general stress of transport (despite cool water and plenty of oxgen) and to the water becoming turbid from vehicle vibrations and movement.

Cecil, does the dark coloring happen just when ice fishing? Maybe it has something to do with temperature and the fish freezing?

No guys I'm not talking about the markings on a smallie intensifing (they do that when they are agitated or stressed, or fish fading or the discoloration from laying on ice. I'm talking about the entire fish becoming really dark almost pitch black.

I've seen it in bluegills and pumpkinseeds in New England too. So it's not limited to salmonids.

No not just when icefishing although I have no doubt temps can be a factor. I fish in New England in June.

Could it be they darken when exposed to the cooler temps to absorb more sunlight for warmth?

Davasta, lightening is more likely a result of light colored surroundings, ie a cooler. Turbid water fish are also usually very pale---at least mine are.

I am thinking extremely clear water and a lack of O2 turns them dark.

From prior threads.

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=103943&fpart=1

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=85635&fpart=1

A fascinating subject and probably more than anyone wanted to know about fish color including changes. As I read the description I could picture the changes occurring just as I have seen it many times.

http://www.wetwebmedia.com/AqSciSubWebIndex/coloration.htm

http://www.clarku.edu/departments/biology/biol201/2002/CSantos/Colored%20Chromatophores.htm

Long before aquariums we’ve known that fishes change color in response to their background, and that they change color during exercise and courtship. These changes in appearance are under the control of pigment containing cells called "chromatophores".

Some examples of this loss of dark color are ... sunfishes (Lepomis) that can quickly blanch from dark to light or come back again given fright or excited states.

Chromatophore changes can be divided into two categories, morphological and physiological. Morphological changes are usually evoked by maintaining an organism in a given setting, on a specific background for a number of days.
Physiological color changes involve alteration of pigment granules causing dispersion or aggregation consequent to various stimuli, e.g. light, temperature, chasing.

The control of aggregating and dispersing of pigment granules is caused by changes in the chromatophores ionic charge. A change of charge within the cell causes a change in color. There are two ways to change the ionic equilibrium within chromatophores, hormonal and neural. Both "paths" are often employed, one working more gradually, the other more immediately. For example, the time required to change from light to dark varies immensely.

There is good evidence that melanophore control by advanced bony fishes is principally actuated by the autonomic nervous system.

There are two principal chemicals that are produced and release by neurons (neurohormones) that affect color.
Epinephrine (Adrenalin): A nerve-activated hormone that’s released by an organism when it is excited or scared, causing pigments to contract and the animal to blanch, lose color.

Acetylcholine: A chemical that is active in muscle tissue, movement, almost always causing melanin to disperse, darkening the organism.

Morphological color changes are due to amounts of pigment present in the chromatophores of an organism. Morphological changes occur very slowly, generally over the course of a month or more, and are usually permanent.

Types of chromatophore are characterized by the color they carry. Erythrophores contain reddish pigments found in carotenoids and pteridines. Melanophores contain black and brown pigments called melanin. Xanthophores produce yellow pigments in the form of carotenoids. Fish are capable of producing some pigments, but others must be supplied in the diet. For example, they cannot produce carotenoids naturally. They accumulate carotenoids from their diet and transfer them into pigment cells to produce red, yellow, and orange colors. The intensity of the pigment is reliant on the quantity and types of carotenoids supplied in their food. The carotenoid pigment found in most marine invertebrates is astaxanthin. Another pigment that is derived from a food source is phycocyanin. This pigment is blue and is readily found in blue-green algae. Additionally, the ability of fish to store pigments they have acquired from their diet will greatly affect their appearance.

Various hues are made possible by the combinations of different layers of chromatophores. Cells carrying more than one pigment are called compound chromatophores. Most fish that appear to have green coloration on their scales actually have a layer with yellow pigment and another layer on top that scatters light and reflects a blue color. There are other types of chromatophores that do not retain pigments .

Note that there are two types of pigments true or based on color and reflective. Also note that not all chromatophores contain the actual pigment color that they appear. That is, that some work on different principles other than selective absorption/reflection. The iridophores contain quanine crystals that reflect different wavelengths of light, which give them an apparent color though no true pigment is present. Further, there are two types of iridophores or reflecting pigment cells, ones with decidedly larger and smaller quanine crystals. The larger crystals can change their orientation to reflect different colors of light. Cells with the smaller crystals can aggregate or disperse their pigments thereby controlling the intensity of color.

Because iridophores are typically light in color, the effect of dispersion and contraction is opposite that of melanophores. When quanine crystals are aggregated, the cell appears darker. The plate-like crystals give off iridescence as seen on the top and flanks of many fishes (e.g. Silver Dollars, Metynnis, Mylossoma, Anchovies, Engraulis).

Green, gold, red, blue and many other colors can be reflected selectively by iridophores. The iridescent blues of Neon Tetras (Paracheirodon innesi) are a result of quanine crystals for instance, and not blue pigmentation.

Fishes also utilize combinations of pigment cell types, with iridophores and melanophores mixed.

Much more in the links.

Thanks Eric.

Eric strikes again!

yes, chromatophores, thats what i was going to say

backing up eric's awesome post.....on my OTHER forum is a smart phD kinda guy, fisheries biologist (drstressor). he posted the following info about fish coloration when asked about a particular fish:

"The changes observed in salmonid coloration are due to the action of hormones on special skin cells called chromatophores. There are several types of chromatophores that contain different pigments. Both the size and distribution of chromatophores are controlled by the pituitary gland, which regulates hormone production. Fish coloration responds to the intensity, wavelength, and pattern of direct and reflected light in their immediate environment. Also, sex hormones hormones control both sexual dimorphism and seasonal color variations.

Some fish can control their color through their central nervous system and change their color pattern over the course of a few seconds. Salmonids can't do this. It takes days or weeks for them to change color in response to light, depth, temperature, stress, and sexual maturation.

Here is a good article on fish color changes:

http://www.wetwebmedia.com/AqSciSubWebIndex/coloration.htm
"
same article eric posted.