Diet of Flatheads in the Susquehanna

[Dave_W]

We have had discussion on the impact of flatheads in the Susky off and on over the years.

A new study out of PSU sheds light on what they're eating. It was common knowledge that young FHs eat a lot of rusty crayfish (I think Mike pointed this out years ago) and this study verified this with strong evidence. Behind rusty crayfish - and a bit more concerning to me - is the large amount of marginated madtoms (my beloved "stonecats" that I like to imitate) being consumed. There's a growing sense that marginated madtoms numbers are in decline and FH predation will only make this worse. I suppose it isn't a surprise since madtoms are nocturnal and about the same size as crayfish.

Adult FHs ate fishes of just about every variety, although, curiously, redbreast sunfish were not on the list. . .

Flathead Study

 

[caddisflyer]

Is it illegal to throw them on the bank?

 

[Kgregor12]

Is it illegal to throw them on the bank?

You would think they would be under the same rules as invasive snake head, invasive Rusty crawdads, invasive silver carp where you can have em dead on your person, just not alive.

Now throwing them on the bank could constitute wonton waste. However, for snakehead I feel like no WCO is going to fault you for beheading one and leaving it. A knowledgeable chef might though!!

Flatties sell ALOT of licenses for the fish commission so from an invasive species standpoint unclear if they are treating it like a snakehead or more like a brown trout considering the economics.

 

[jifigz]

I find the lack of redbreast in their diet to be very surprising! After all, people who fish for them a lot use redbreasts and bluegill for bait. I am not sure I fully believe the lack of redbreast in their diet, but I sure hope so because I love the redbreast sunfish.

My cousin's husband likes to fish for them, and he has caught some real hogs on the good ol' stonecat (margined madtom.) He caught a fish over 30 lbs on a stonecat near Newton Hamilton.

I think taking crawdads and using them for bait for young flatheads sounds like a good game plan. I would creel those young flatties and fry em up!

 

[poopdeck]

Is anybody surprised by the findings? Only the flathead/snakehead aficionados will read the study and say, “see, it doesn’t say there’s a harmful effect.” Here was the most interesting statement in the study:

“Not surprisingly, the researchers said, with increasing flathead catfish size comes a proclivity to feed on larger prey. In general, flatheads over 24 inches long primarily consumed fish species, and fish below 24 inches generally fed on a mix of invertebrates and fish species.”

Wait till those Susky flathead get to Schuylkill and Delaware river size. Wait until the snakehead population increases as well and you will have a front row seat to what some believe is nature balancing itself out.

 

[Kgregor12]

Is anybody surprised by the findings? Only the flathead/snakehead aficionados will read the study and say, “see, it doesn’t say there’s a harmful effect.” Here was the most interesting statement in the study:

“Not surprisingly, the researchers said, with increasing flathead catfish size comes a proclivity to feed on larger prey. In general, flatheads over 24 inches long primarily consumed fish species, and fish below 24 inches generally fed on a mix of invertebrates and fish species.”

Wait till those Susky flathead get to Schuylkill and Delaware river size. Wait until the snakehead population increases as well and you will have a front row seat to what some believe is nature balancing itself out.

You are so right! There is going to be a “Flathead Truth” video just like that “snakehead truth” video that guy in MD made claiming their all harmless.

What most anglers don’t understand is aquatic invasions have different stages and can play out over much longer than the evolutionarily insignificant length of one human life let alone 10-20 years fishing a river RIGHT after an introduction. Not to mention impacts will change with changing hydrology and temperature trends.

Another point is no one has looked at effect on amphibians with snakeheads and what is everyone chucking for them fly/lure wise??? Lol

 

[Fredrick]

There is a video series on blue cats, its game over when they start taking hold.

 

[Kgregor12]

View attachment 1641238737

There is a video series on blue cats, its game over when they start taking hold.

Great example of a sport fish everyone thought declared harmless for decades before MD governor declared a state of emergency over attempting to get federal funds to mitigate the unthinkable damage they ultimately caused. Basically when anglers declare an introduced species harmless because they like catching them its time to get your 🍿 out.

 

[troutbert]

Apparently blue catfish are common enough now to support a commercial fishery in the Chesapeake Bay.

Wild-Caught Chesapeake Blue Catfish | Marylands Best

marylandsbest.maryland.gov

 

[jifigz]

Is anybody surprised by the findings? Only the flathead/snakehead aficionados will read the study and say, “see, it doesn’t say there’s a harmful effect.” Here was the most interesting statement in the study:

“Not surprisingly, the researchers said, with increasing flathead catfish size comes a proclivity to feed on larger prey. In general, flatheads over 24 inches long primarily consumed fish species, and fish below 24 inches generally fed on a mix of invertebrates and fish species.”

Wait till those Susky flathead get to Schuylkill and Delaware river size. Wait until the snakehead population increases as well and you will have a front row seat to what some believe is nature balancing itself out.

Ummmm. They already are to the size of Schuylkill and Delaware fish, and most people are speculating that the new state record flathead will be from the Susquehanna, which shouldn't come as a surprise as the Susky system seems to overall be more productive than the Delaware and Schuylkill systems, but maybe I am wrong that assessment.

 

[Kgregor12]

Apparently blue catfish are common enough now to support a commercial fishery in the Chesapeake Bay.

Wild-Caught Chesapeake Blue Catfish | Marylands Best

marylandsbest.maryland.gov

Yea no shortage of blue cats but the problem has been permits to process the blue cats for sale but a second was just issued recently. Hopefully snakeheads see some movement on that front as well. I think right now snakeheads just going to prisons to eat despite large public interest in their flesh.

 

[bringthepain]

Apparently blue catfish are common enough now to support a commercial fishery in the Chesapeake Bay.

Wild-Caught Chesapeake Blue Catfish | Marylands Best

marylandsbest.maryland.gov

I wonder if the blue cats are negatively effecting the striped bass population there

 

[Kgregor12]

I wonder if the blue cats are negatively effecting the striped bass population there

Yea, from predation on juvenile stripers and competing for food with them such as crabs, mollusks, and aquatic worms are all things I have read as to why they can be harmful.

 

[poopdeck]

Ummmm. They already are to the size of Schuylkill and Delaware fish, and most people are speculating that the new state record flathead will be from the Susquehanna, which shouldn't come as a surprise as the Susky system seems to overall be more productive than the Delaware and Schuylkill systems, but maybe I am wrong that assessment.

Oh crap I see the state record at 66 lbs was caught on the Susky. Oh well, too late. Just waiting for the snakeheads to catch up I guess.

 

[jifigz]

Oh crap I see the state record at 66 lbs was caught on the Susky. Oh well, too late. Just waiting for the snakeheads to catch up I guess.

It wouldn't surprise me if the Susky produces a fish in the 80-90 lb range very soon. It's funny that in their native Allegheny they often don't grow a whole lot bigger than 30-40 lbs.

 

[Kgregor12]

It wouldn't surprise me if the Susky produces a fish in the 80-90 lb range very soon. It's funny that in their native Allegheny they often don't grow a whole lot bigger than 30-40 lbs.

There is a good reason for that actually. Its called “growth plasticity.” When you drop an invasive species in a new environment none of the native species that evolved there ever got a chance to genetically adapt to it. So this means no evolved chemical warning cues, avoidance strategies or defense mechanisms against the invader thus there is a much higher success rate when that invasive species forages. Many invasive species grow largest outside their native range for this reason.

 

[jifigz]

There is a good reason for that actually. Its called “growth plasticity.” When you drop an invasive species in a new environment none of the native species that evolved there ever got a chance to genetically adapt to it. So this means no evolved chemical warning cues, avoidance strategies or defense mechanisms against the invader thus there is a much higher success rate when that invasive species forages. Many invasive species grow largest outside their native range for this reason.

I'm aware that invasives often thrive and new ecosystems and even outshine their growth, numbers, and potential that they inhabited in their native ecosystem. How much do the fish populations and other stuff vary from the Allegheny to the Susky, though? I'm aware redbreast aren't native to the Allegheny and Pike and smallmouth are, but how different are the current rivers' makeup of species. Since we have so many invasives all over the place, just like us having the non-native rock bass and smallmouth all through the Susky drainage, what critters are they feeding on in the Susky that they aren't in the Allegheny?

 

[greywolf]

Ummmm. They already are to the size of Schuylkill and Delaware fish, and most people are speculating that the new state record flathead will be from the Susquehanna, which shouldn't come as a surprise as the Susky system seems to overall be more productive than the Delaware and Schuylkill systems, but maybe I am wrong that assessment.

They are catching 40 - 50 lb flathead pretty consistently on the lower Susquehanna. I think the state record came from here also.

 

[Kgregor12]

I'm aware that invasives often thrive and new ecosystems and even outshine their growth, numbers, and potential that they inhabited in their native ecosystem. How much do the fish populations and other stuff vary from the Allegheny to the Susky, though? I'm aware redbreast aren't native to the Allegheny and Pike and smallmouth are, but how different are the current rivers' makeup of species. Since we have so many invasives all over the place, just like us having the non-native rock bass and smallmouth all through the Susky drainage, what critters are they feeding on in the Susky that they aren't in the Allegheny?

I'm aware that invasives often thrive and new ecosystems and even outshine their growth, numbers, and potential that they inhabited in their native ecosystem. How much do the fish populations and other stuff vary from the Allegheny to the Susky, though? I'm aware redbreast aren't native to the Allegheny and Pike and smallmouth are, but how different are the current rivers' makeup of species. Since we have so many invasives all over the place, just like us having the non-native rock bass and smallmouth all through the Susky drainage, what critters are they feeding on in the Susky that they aren't in the Allegheny?

sometimes as an angler I think I am guilty of forgetting the relative proportion of non-sport fish components of the aquatic ecosystem. The study indicated the native stone cats were one of the main prey items so it would make sense if they did not evolve with invasive flatheads it would make sense they might be more vulnerable than the allegheny introduced transplants you mentioned. Same may go for native fall fish, white suckers, northern hog suckers, log perch ect. This is why growth plasticity can peak because when the native forage get unsustainably burned though eventually the food source diminishes as you lose density or presence of native species. Then you get blue cats in the James river, 75% of the biomass all 20 inches long. Flatheads likely will experience the same phenomena at some point if they are burning through stone cat’s unsustainably. Then the question is what else depends on stone cats for anything from food, symbiosis, or taking partial forage pressure off another species.

We all imitate stonecats for nonnative smallmouth so for stone cats you can see the nonnative fish introductions start to compound from a predator standpoint. Question is for me who else depends on these stone cats and what happens to the food web if we lose em.

 

[Nymph-wristed]

Interesting study.

I am sure climate change is getting an assist, but folks tip toe around it so as not to offend.

All the bass and stonecats and walleye and flatheads (and all the "less important" aquatic life) in one deep hole together riding out historic low flows sounds like a great petri dish to explore a worst case scenario.