Something has been biting my fish.

[Mike in Vermont]

Hey all:

I stocked my lower pond with trout the end of April. 100 3-9 inch rainbow and 20 3-5 inch Brown. The brown trout have been doing great. They eat mostly natural food. Hardly any pellets. I have seen them clear the water over 4 feet. My rainbow trout haven't been eating what I would consider normally, since I got them. In the beginning, many turned bright in color, and acted like they were spawning. The fish were offered food every day. A few weeks ago, it seemed like they were eating better. That stopped 3 days ago.
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Yesterday, I saw several rainbow with bite marks, on top of their back. Al least 25 fish, maybe all. Some have grown considerably, Over 12 inches. Nice, fat fish. Others, were a little slim. So far 2 have gone belly up. I have seen 3 brown trout. None of them had any marks. I have found zero sign of any animal, such as a mink, entering the water. Also, it's kinda the wrong time of year to be having problems with mink or otter. Although, it appears these fish were hit from the top. This isn't the work of an Osprey. They put a hole in the fish every time. I haven't spotted any turtles. No fish in my upper pond have been affected. Could the brown trout be doing this? I did notice one dart into the shallow water, behind a bitten fish. For a second, he looked like he on a trail. They are very aggressive. Also, it looks like these marks were from multiple bites. Here's some disturbing pics.
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[Dave 54]

HI @mike in Vermount not being a trout person I couldnt answer your question so I decided to read up about them .
This is what I came up with :-

http://troutster.com/trout-species/brown-trout/

So it appears that yes they are cannibalistic ..... however what you should try doing about this...... my suggestion perhaps feed them more in the way of high protien trout food and see if this will stop it or not .
However trout arent my fortie so its up to you which way you go with this , perhaps a little more your recearch my friend

Dave

 

[Mike in Vermont]

Thanks for the link, Dave. That was a good read. The brown trout are about 5 to 8 inches now. One wouldn't think a fish this size could do this to a larger fish. I keep a pretty close eye on the ponds. Been home and outside most of the time, the last few weeks. I haven't seen anything enter or leave the pond, though. I was on guard before 6:00 AM this morning. Took a good walk through the woods, too. I didn't find one track of any critter that could do this. I do have a live trap set, with a can of sardines for bait. I have to wonder if one brown took a nip at a rainbow, and that lead to other bites, creating a trend. IMO, the rainbow trout haven't acted normal from the beginning. Yesterday, they acted like they were on the run all day.

 

[Meyer Jordan]

The problem is not your brown trout. Any signs of attack from these fish would first appear as damaged tail fins on the prey fish. Since the bite marks are all on the top of the fish a four-legged predator seems more likely.
Most predators begin foraging at dusk and, depending on availability of prey, will continue until dawn.

 

[Dave 54]

The problem is not your brown trout. Any signs of attack from these fish would first appear as damaged tail fins on the prey fish. Since the bite marks are all on the top of the fish a four-legged predator seems more likely.
Most predators begin foraging at dusk and, depending on availability of prey, will continue until dawn.

Are you thinking perhaps a racoons as the main offender ?

Dave

 

[Meyer Jordan]

Are you thinking perhaps a racoons as the main offender ?

Dave

Not particularly. There are several different hungry furry four-legged critters in Vermont. Hopefully Mike in Vermont will be able to identify the culprit.

 

[Dave 54]

Not particularly. There are several different hungry furry four-legged critters in Vermont. Hopefully Mike in Vermont will be able to identify the culprit.

Mike have you got motion sensors ? .....its time to get them out again

Dave

 

[Mike in Vermont]

Here's my list of possible culprits.
.
Mink
Otter
Raccoon
beaver

Non furry culprits
.
Snapping turtle
Osprey
.
I pulled out another trout. Walking over, I thought it's too big for anything I stocked. It was a Brook Trout nearly 16 inches. In 2011 or 2012, my mom caught 75 6-7 inch trout out of my upper pond with a fish pole, and put them in the lower pond. I thought they all got eaten. I haven't seen a fish jump in that pond in 3 years, prior to stocking. I couldn't spot the lethal blow but, they are much more fragile than the other trout species.
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A night attack is making the most sense. Do all of these furry animals prey at night?

 

[Mike in Vermont]

Mike have you got motion sensors ? .....its time to get them out again

Dave

Unfortunately, I don't. The live trap is set. Any suggestions on bait, other than canned sardines?

 

[Dave 54]

Unfortunately, I don't. The live trap is set. Any suggestions on bait, other than canned sardines?

Sounds good to me

Dave

 

[Mike in Vermont]

The trap was closed this morning. No critter, though. It ate a sardine and drank the juice. I could see bite marks in another sardine. Surely he will never stick his head in there again. I hope the noise and possible impact of the door hitting him will detour further visits. I have removed 5 dead fish so far.

 

[addy1]

I would reset it, slightly different spot, cover up the trap except the entrance. put a nice fat sardine at the far end, and a few pieces near the entry. I do that to catch ground hogs. Unless it is to big for the trap and it can't close you might just catch again.

 

[Meyer Jordan]

If you are in a rural area, there is a real possibility of more than one specie of predatory creature roaming around at night. The one that visited the trap may or may not be the same that is attacking your fish.

 

[Mike in Vermont]

I reset the trap. The trail of sardines and camo idea sounds good. I am thinking of installing bright lighting, for the nighttime hours. I can put it on the upper bank, so it will light up the whole pond. At minimum, it would give the fish a chance to see the animals shadow, before it attacks. I suppose I could trim around the pond again, too.

 

[MitchM]

Time to get a trailcam, Mike!