Exchange with Chris Penn -- Willard Bay catfish

[Kent]

"Hi Chris,
I remember, in the olden days, that there were huge cats in Willard Bay (comparable to the cats in the Bear River and in Utah Lake).  It seems, these days, the largest cats are ~28" long.  There are lots of cats, but I never hear of any really large ones.  Do you have any idea why they aren't growing as large these days?
Thank you,
Kent Jasperson"

Chris' reply:

"Good question, Kent. I can't say for sure, but I'm pretty confident it has to with the change in the forage base that took place after gizzard shad were introduced around the 1990s. From what I've read in old reports, it wasn't uncommon in the 70s and 80s to have some big year classes of walleye that got pretty skinny due to fluctuations in the forage fish community, which was mainly crappie, perch, bluegill, and other juvenile sport fish. The shad were introduced to provide a more abundant and consistent forage base. The shad have been a success in those regards, but they also come with some tradeoffs. One of those is that as they appear to compete with the black crappie, and likely yellow perch as well when they are in their juvenile stages, which means populations of those fish are likely not as abundant as they once were. I've come across scientific literature documenting the relationship between gizzard shad and crappie, but so far have not seen any studies on gizzard shad and yellow perch. That said, there are some scientific papers to the contrary that have conducted studies and not seen any competition between shad and crappie populations. So the science is inconclusive there and probably situation specific. The other thing having to do with the shad is that we are at the northern end of their habitable range, where many winters the young that were spawned in the spring die off during the winter due to an inability to acclimate to the cold. So long story short, when we combine the impacts of having presumably less panfish as forage, particularly the smaller 4-7" crappie and perch, as well as the fact that there are many years when the gizzard shad die off in the winter, leaving the predator fish with few things to eat during the spring time and further then having to wait for the next year class of shad to grow in the spring and summer, we have a formula for growing predator fish like the walleye, wiper and catfish fast to about 20-4 inches, but after they hit those lengths, they really need some bigger and more reliable prey to get bigger and they often don't have that in Willard. So while all those shad we see in the summer are a fantastic resource, and the fat reserves on most of our predator fish consistently look great going into fall, I'm thinking the lack of consistent mid-sized prey, especially in the spring and early summer, tends to prevent our fish from getting really big."

Chris"

[jjannie]

Interesting, thanks for sharing it

[wiperhunter2]

I also contacted Chris, asking him about all the dead cats people are seeing at Willard. He wasn't too concerned about it and his thoughts were that those dead cats died from old age. He also stated, if the numbers of dead cats increase, they would need to do some test, to find out if it's something more serious, so if any of you start seeing high numbers of dead cats, please let us know and we can pass that info on to Chris, unless you want to contact him yourself, thanks.

[TubeDude]

As I have postulated before, the predators in Willard are forced to forage on whatever is available during months when the shad are non-existent or too small for worthwhile pursuit.  Over the years I have caught wipers, walleyes and cats with all kinds of non-shad stomach contents.  As Chris pointed out, yearling perch, crappies, and bluegills are often tummy tidbits for the predators.  But even small catfish and residual log perch and spottail shiners also show up at times.  But one of the biggies...especially for cats...are crawdads.  I find them in both wipers and walleyes during lean times, but in cats year round when water levels are up and the "mudbugs" can use the flooded rocks to spawn lots of young.





In the "good ol' days"  water levels remained high up into the rocks all year...making for steady year-round concentrations of crawdads for cats.  And before shad arrived...and started slurping up all the zooplankton needed by the young of most species to grow beyond fingerling size...crappie prospered.  They had good spawning conditions all around the lake every spring...and the young had abundant zooplankton.  Today the almost yearly water drawdowns...resulting in poor spawning conditions...and the reduction of zooplankton by shad (to feed the young) results in low crappie populations.  Then factor in the heavy meat harvest each year in the marinas by the happy harvesters and there are not as many large crappie surviving to spawn.



Bottom line is that the overall ecology of the lake has forever changed with both the addition of new species (shad and wipers) and the increased demands of downstream water users to keep the water levels wildly fluctuating.  Some fishing is better.  Others not so much.