Crayfish turning blue. - General Discussion - NANFA Forum (2024)

Fleendar the Magnificent

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• NANFA Guest

• Ohio

These are the specie called the Rusty Crayfish or Orconectes Rustica and they've always been that olive drab with rusty reddish brown on them. However, a pair out of the 5 in my tank have started turning a dark blue with green hue to them and I've had one in another tank turning pink. Has anyone had wild crayfish turn blue/blue-green on them before? I have shown the blue one and one that has remained the color it was in the wild. Both photos were taken on the same day and in the same tank. As for the food they eat, it's blood worms, Mysis shrimp and once in awhile, minnow fry and they seem to be doing well with it as I've had all 5 crays molt twice since October 1st.

Anyideas on what might causethese color changes?

Matt DeLaVega

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• Forum Staff

• Ohio

In some streams, the bluish coloration is the norm. I think it is just a natural variation.

The member formerly known as Skipjack

Fleendar the Magnificent

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• NANFA Guest

• Ohio

Could be, however, all of the crays I caught were all that common olive-drab color and after several molts, started turning color. I did some other looking around and people have speculated that this can be caused by anything from water Ph and a harmless virusto food they eat and water hardness. Hard to say, but they're getting prettier.

lilyea

• 
• NANFA Member

• Peace River Watershed, Central Florida, USA

In addition to several environmental factors, another possibilities is if it is a cross with a O. propinquus.

Matt DeLaVega

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• Forum Staff

• Ohio

Size? Literally every one over 2 inches in Todd's fork is that color.

The member formerly known as Skipjack

Fleendar the Magnificent

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• NANFA Guest

• Ohio

One's under 2", more like 1.5" and the other one is closer to 3". The biggest one I have is still dark olive-drab and rusty brown, and that's after he's molted twice now.

centrarchid

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• NANFA Guest

Diet. When diet low in carotenoids (forms of vitamin A), the crayfish loose the ability to develop reds and yellows in the exoskeleton. The exoskeleton then takes on a bluish cast. A complication can involve loss of appendages during molting process. You can correct by feed green plant materials or diets formulated to have lots of beta-carotene. Feeding with brine shrimp can also get red color back.

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Matt DeLaVega

• 
• Forum Staff

• Ohio

Diet. When diet low in carotenoids (forms of vitamin A), the crayfish loose the ability to develop reds and yellows in the exoskeleton. The exoskeleton then takes on a bluish cast. A complication can involve loss of appendages during molting process. You can correct by feed green plant materials or diets formulated to have lots of beta-carotene. Feeding with brine shrimp can also get red color back.

What might cause this in wild rusticus, living in a fairly large stream? It would seem that diet should be well rounded and varied. I suppose it is possible that they are not getting enough carotenoids, but I would be surprised.

The member formerly known as Skipjack

centrarchid

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• NANFA Guest

What might cause this in wild rusticus, living in a fairly large stream? It would seem that diet should be well rounded and varied. I suppose it is possible that they are not getting enough carotenoids, but I would be surprised.

They could be overgrazing the plant biomass. High crayfish density can certainly do it during the summer months when trees block instream photosynthesis at same time crayfish grazing pressure is highest. Some plants may not be good sources of carotenoids.

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Fleendar the Magnificent

• 
• NANFA Guest

• Ohio

The Olentangy river is filled with these buggers. When we wade, most steps dislodge a crayfish. The population of rustiesis quite high in this river.

That said, does the low carotenoid intake have other negative effects on them and their health? I DID notice that my female who has once again molted(twice in 3 months) is missing her big claws. She had lost them before and was regrowing them up to a decent size and now they're left on the exoskeleton and she's without again.

lilyea

• 
• NANFA Member

• Peace River Watershed, Central Florida, USA

If it is a diet issue then you may want to try feeding Hikari Crab Cuisine pellets. Good luck!

Fleendar the Magnificent

• 
• NANFA Guest

• Ohio

@Lilyea

Thank you. Will check out these other foods. I've heard that you can even feed them spinach and other greens as well. I work in a store that sells produce. I can probably get some of the greens that they throw away.

lilyea

• 
• NANFA Member

• Peace River Watershed, Central Florida, USA

@Lilyea

Thank you. Will check out these other foods. I've heard that you can even feed them spinach and other greens as well. I work in a store that sells produce. I can probably get some of the greens that they throw away.

I agree that my crayfish have been known to each blanched vegetables (the blanching helps soften them and make them sink without losing the benefits of fresh vegetables) and, similarly, algae wafers designed for plecos. My understanding is that in the wild crayfish are targeting the microorganisms in the grass and end up eating the grass so I am suggesting that, while beneficial, increasing the intake of greens won't cover all of their dietary needs. Other pet food companies sell aquatic invertebrate food, however I choose the Hikari products because they differentiate between shrimp (Shrimp cuisine) and crayfish/crabs (Crab Cuisine). I suggest that you try the blanched greens, just don't stop there. I look forward to hearing if the change in diet affects the health and appearance of the crayfish!

Fleendar the Magnificent

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• NANFA Guest

• Ohio

Thank you for the info. I'll get going on this and see what changes occur. The crays have been molting like mad over the past month. In the past 3 months the two in my other tank have molted twice each. So they're not lacking in food, but probably not getting all of the needed nutrients.

centrarchid

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• NANFA Guest

When nutrient profile is off, what I often see is frequent loss of appendages during molting and chelae that are oddly shaped. That is in addition to color changes that can also occur.

My favorite feed in confinement for crayfishes is algae wafers like used for algae eating aquarium fishes plus a little shrimp pellets.

Find ways for people not already interested in natives to value them.

Fleendar the Magnificent

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• NANFA Guest

• Ohio

Thank you. I'll look into the wafers and get some greens for them.

Fleendar the Magnificent

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• NANFA Guest

• Ohio

I got them the algae wafers and they immediately started ripping them apart. We'll give it a few months and see what happens now that they're getting greens and beta carotene.

LepomisAuritus

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• NANFA Guest

• SE PA

They could be overgrazing the plant biomass. High crayfish density can certainly do it during the summer months when trees block instream photosynthesis at same time crayfish grazing pressure is highest. Some plants may not be good sources of carotenoids.

Once or twice I have seen blue rusty crayfish in the summer when the population is high. Seems to make sense.

Fleendar the Magnificent

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• NANFA Guest

• Ohio

Never have seen them blue in the river, but this river's mostly open water to the sun. Biomass might be much better in the river where we're at.