"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"
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"