Water boatmen dangerous to fry?

I saw a water boatmen in the container pond that I am raising blackbanded sunfish fry. Tried to catch him, but he disappeared. Should I be concerned? Will it eat the fry?
Thanks

I think you are better off without them. They can latch onto smaller fish and likely end up hurting them. Whether this is done deliberately to "attack" the fish or not I'm not sure about.

Cheers
Peter

I use them as natural aireators.

A water boatman eats mostly algae and should not be generally a problem for your fry. Other members of the true bugs are preditory though. Backswimmers are about the same size and can be harmful.

Sorry for the syntax and grammer lapses. Only second cup of tea.

I am not sure how to distinguish a boatman from a backswimmer. I googled them both and my search gave me a variety of aquatic insects. How can I tell them apart?

try bugguide.net

Boatmen are brown, swim right-side up, and rarely float at the surface. Backswimmers swim upside down, are white or pale gray on the back, and spend most of their time floating just under the surface (waiting for bugs to fall or land on the surface). Backswimmers have a sharp beak and painful venom! Boatmen have neither.

try bugguide.net

Boatmen are brown, swim right-side up, and rarely float at the surface. Backswimmers swim upside down, are white or pale gray on the back, and spend most of their time floating just under the surface (waiting for bugs to fall or land on the surface). Backswimmers have a sharp beak and painful venom! Boatmen have neither.

Backswimmers are known for giving a painful bite, but if you're gentle and scoop them out of the water you'd be safe. I used to get them in the pool all the time and scooped them out with my hands before I read about their bite.

As for water boatmen, the bug is harmless. But actual reckless boaters on the water can be a nuisance when swimming, fishing, or sampling.

Water boatman, as a type of insect, can mean:

In the USA, Corixidae: these are mostly plant-eating insects but also eat small animals such as tadpoles. They inhabit ponds and slow moving streams, where they swim right-way-up near the bottom.
In Britain, it can also mean the Notonectidae (called backswimmers in the USA): these swim upside-down on the surface and are predators. They swim with two long legs that look like oars.

Source: http://en.wikipedia....i/Water_boatman

Either way it sounds like not good news for your fry. If it were my container, I'd remove them.
If the fry are easier to catch, net them out first. Then you won't have to worry about making a great disturbance as you hunt down the boatman.

Edited by EricaWieser, 04 August 2011 - 12:58 PM.

I hate to say it, but this is a good example why Wikipedia and similar websites really are not good sources. If you click on the link for Corixidae, you will find that the majority are not predatory. The problem with sites like this is that information can be twisted around easily and mis-referenced. In this case, the majority non-predatory Corixidae get turned into organisms that "are mostly plant-eating insects but also eat small animals such as tadpoles". This makes it sound like all of the species in Corixidae are predatory at times.

I hate to say it, but this is a good example why Wikipedia and similar websites really are not good sources. If you click on the link for Corixidae, you will find that the majority are not predatory.

Ah, *facepalm*, you're right! I clicked on the link for Corixidae as you said and yes, it says,

Corixidae are unusual among the aquatic Hemiptera in that they are mostly non-predatory, feeding on aquatic plants and algae instead of insects and vertebrates. They use their straw-like mouthparts to inject saliva into plants. The saliva digests the plant material, letting the insect suck the liquified food back through its mouthparts and into its digestive tract. A few species of Corixidae are predatory, but the majority are herbivorous.

http://en.wikipedia.org/wiki/Corixidae

I'm going to log in and change the disambiguation page.

Edited by EricaWieser, 04 August 2011 - 02:15 PM.

I'm going to log in and change the disambiguation page.

Done!

In the USA, Corixidae: the majority of species are herbivorous, but some species may eat small animals such as tadpoles. They inhabit ponds and slow moving streams, where they swim right-way-up near the bottom.

http://en.wikipedia.org/wiki/Water_boatman

Edited by EricaWieser, 04 August 2011 - 02:17 PM.

Very nice of you to fix it so that people don't get confused, but it also sort of illustrates my point. A person who does not have a background in the material changed the information presented. That's what makes it not a good source. A better source would be to go look up water boatmen in an aquatic biology/ecology, limnology, ID, or other similar book. Or just wait until someone on the forum with a background in aquatic insects can comment.

(Erica - I'm not picking on you. Only on the references. It's too easy for people to take what is written on the internet as correct fact. This happens more and more, and this case was just a good example of why we should all be more careful).

Nativeplanter, I agree with your observation on general internet sources. They are rarely completely wrong, but are also rarely complete. My response also used the term generally, which is not the best way to do things, either.

I was speaking from experience, but also double-checked my thoughts with Merritt and Cummins' Introduction to Aquatic Insects of North America.

The problem with aquatic true bugs, which includes corixids, is that they include several species that are bad for small fish (or unwary fingers and toes!). I should have withheld my opinion without a firm ID.

And so, in general... I should wait until I finish my second cup of tea before I jump into the fray.

Not to worry, Jim. Your response was fine (at least to me). It was based on personal knowledge of the subject and a well-respected tome on aquatic insects. Your advice was probably right on. Most likely the insects observed are nothing to worry about.

I'm not suggesting that we put sources for everything in our posts. I'm just suggesting we be careful about citing information from sources for which we can not be sure of accuracy and/or completeness.

I use the word "generally" a lot as well. It's rare that something doesn't have an exception somewhere. It's when we think we know the absolute answer when we get into trouble.

Nativeplanter, I agree with your observation on general internet sources. They are rarely completely wrong, but are also rarely complete. My response also used the term generally, which is not the best way to do things, either.

I was speaking from experience, but also double-checked my thoughts with Merritt and Cummins' Introduction to Aquatic Insects of North America.

The problem with aquatic true bugs, which includes corixids, is that they include several species that are bad for small fish (or unwary fingers and toes!). I should have withheld my opinion without a firm ID.

And so, in general... I should wait until I finish my second cup of tea before I jump into the fray.

Yeah, I also found waterboatmen listed as backswimmers and also the reverse. Plenty of mis information on the net.
I am quite confident these are backswimmers as their legs are on top of the body. They have bright red eyes too. Hopefully I can find that sucker again as the pond is heavily planted.
Thanks all for the info.

Yeah, I also found waterboatmen listed as backswimmers and also the reverse. Plenty of mis information on the net.
I am quite confident these are backswimmers as their legs are on top of the body. They have bright red eyes too. Hopefully I can find that sucker again as the pond is heavily planted.
Thanks all for the info.

Mangement tool alternative to dip netting is dispersal of small amount of oil (I like to use vegetable oil) on water surface. It will interfere with air exchange of insects, especially aquatic bugs, that break skin of water to get fresh air. Modest aeration can keep oil around perimeter leaving middle open. Water boatmen / backswimmers will not avoid oil which will kill them fairly quickly. Oil will also take out the more predatory beetle larvae.

Mangement tool alternative to dip netting is dispersal of small amount of oil (I like to use vegetable oil) on water surface. It will interfere with air exchange of insects, especially aquatic bugs, that break skin of water to get fresh air. Modest aeration can keep oil around perimeter leaving middle open. Water boatmen / backswimmers will not avoid oil which will kill them fairly quickly. Oil will also take out the more predatory beetle larvae.

Ah, good to know. I got him with the net, so hopefully there are no more.

Good call, centrarchid. I forgot about that trick - good for most insects that need to get to the surface to breath.

I wouldn't worry too much. I have caught them eating a fry or two in my pond (which i used to raise neotropical cichlids in the summertime in NE), but the predation rate was negligible. Good chance the particular fry were unhealthy anyway.