With gizzard shad now at the top of the list of concerns for Roosevelt Lake, fisheries chief Chris Cantrell emphasized that Arizona Game and Fish is dedicated to sustaining and enhancing that besieged bass water.
“The lake has gone through some changes in the past five years,” he said. “We’ve had a lot of confounding issues, including Largemouth Bass Virus, golden alga, and now gizzard shad. And we have to deal with drawdowns during the post-spawn for power and water.”
During that time, bass catch rates have risen, but weights have declined. Additionally, crappie catch rates during gill-net sampling have plunged 100 percent, with weights down as well.
And maybe not so coincidentally, gizzard shad, which showed up without explanation in 2007, made up nearly 28 percent of the catch during electrofishing surveys in 2011. Most disturbingly, they quickly grew from bite-size for bass to more than 8 inches in length, with the bulk of sampled fish 13 inches or more.
As a consequence, the shad are no longer vulnerable, and thus are a negative for the Salt River reservoir.
“The effects of gizzard shad in Roosevelt Lake, though not fully understood, are now becoming evident,” Cantrell said.
“Gizzard shad are documented as having an impact on sportfisheries back east through competition with other forage and game species at the larval stage and in reduction as a food resource for largemouth bass as they soon outgrow largemouth bass mouth gapes.”
The big question now is whether the shad are reproducing.
“Maybe this is just a size class moving through the system,” the fisheries chief said. “But we assume they are (reproducing). This year, we’ve been hearing about a huge population of threadfin shad. There could be gizzard shad in there too.”
While some anglers would like to see aggressive gill-netting to reduce the gizzard shad population, Cantrell said that probably is not a practical option. “We don’t think that would be effective,” he said. “And it would have to be long-term, and we don’t have the resources for that. We will euthanize the shad that we catch (during sampling), but that’s just a drop in the bucket.”
So for now at least, the agency will continue to analyze the gizzard shad’s impact, both at Roosevelt and downstream in Apache, where they’ve now been documented as well.
But that’s not to say it won’t work to improve sport fishing in Roosevelt and other waters.
“We’re looking at habitat,” the fisheries chief said. “We’ve wanted to put in habitat anyway, and research shows less drastic declines with more habitat. We’ve dedicated a position to full-time habitat work, with Roosevelt up front.”
Additionally, Arizona is asking Texas Parks and Wildlife to assist in examining bass genetics in 10 state waters stocked with Florida-strain bass during the 1970s and early 1980s.
“We were getting big bass from that into the 90s,” Cantrell said. “We want to see if the genetics are still viable. If not, we’re going to work with local partners to purchase and stock more Florida bass.”
(This article appeared originally in B.A.S.S. Times.)