EAST TAWAS – The following is the second of a two-part story on a virtual workshop which was held recently, regarding Saginaw Bay/Lake Huron. Data pertaining to the walleye population was featured last week, and this story will focus on the research surrounding yellow perch (YP).

The Department of Natural Resources (DNR) Fisheries Division reported on the dwindling YP population in Saginaw Bay, during one of the 2022 Lake Huron Regional Fisheries Workshops. Among the presenters who spoke about this area, which ties into Tawas Bay, was Dave Fielder.

One method of data collection which has been utilized by the department, for more than 50 years, is trawling. Fielder showed a graph comparing the mean catch per unit effort (CPUE) for age zero YP, those being the fingerlings/young of the year (YoY), and the age 1 (yearlings) and older YP.

From 1970 to the present, the graph depicts the average catch per 10-minute tow from the trawling events, of these two different size/age categories of YP. In each year, one bar represents the YoY. Another bar is for the larger, yearling and older YP, which are the ones that are of interest to both the recreational and commercial fisheries, Fielder noted. “And for a long time, we had both.”

But there was a notable decline in all ages of YP, from about 1992 through 2002, and he said that this was likely heavily affected through the initial colonization of the bay by invasive zebra mussels.

There was a dramatic shift in 2003, though, stemming from food web changes in Lake Huron. As Fielder also noted during his talk on walleye, the greatest impact was the virtual disappearance of alewives, which are a predator and competitor on walleye fry. Therefore, in their absence, walleye reproduce much better.

“And just like with walleye, we see that the amount of yellow perch reproduction exploded,” he said, when highlighting the numbers from 2003. In fact, the catch per 10-minute tow ranges from 0-1,000 on the graph, and the YoY at this time were off the charts – literally – with a value of 2,451.

Every year since, researchers have continued to see a lot of natural reproduction. Although YP are reproducing just fine, there aren’t many age 1 and older perch, which means they’re not surviving.

Based on the trawling events, which occur annually in September, Fielder said there are a lot of young YP in the fall as age zeroes, “then we go back and look for them next year as age ones, and there’s not very many there.”

Without that, he advised, “we’re in a period of considerable decline of yellow perch abundance.”

Fielder said that the best explanation is the walleye diet. The DNR’s annual gillnet survey is another information source for Saginaw Bay and, as part of this, walleye stomachs are examined to see what they’re eating. Data from 1989 on, shows that for a long time, this went back and forth between gizzard shad and alewives.

“Well, when the alewives disappeared, the diet shifted over to young yellow perch. And so now, walleye are feeding heavily on that,” he said. They’re still feeding some on gizzard shad, as well as a bit of rainbow smelt, a couple shiner species and others, but YP is now a major component of their diet. “So there’s that mortality bottleneck between the age zeroes and the age ones.”

Fielder pointed out that it’s not just walleye, as the DNR sees this in just about all of the predators that they look at. But walleye are probably the dominant apex predator in the fish community, and chances are that they’re having the biggest overall impact.

“So in some ways, perch have now become more of a forage fish, sadly, in Saginaw Bay,” he said. Thus, something is still broken there. The alewives likely used to create a predation buffer which protected perch. Prior to that, a buffer was provided by cisco.

Trying to reestablish a native planktivore which would give that same predation buffer for YP is one reason why the DNR fisheries team, plus several other agencies, are so interested in restoring cisco – formerly named lake herring – to Saginaw Bay and Lake Huron.

For example, U.S. Fish and Wildlife Service (USFWS) Biologist Kevin McDonnell gave an update on the restoration efforts, at the 2021 workshop. As reported, he said that cisco began to decline between the 1940s and 1970s, for reasons including the competition/predation of alewife and rainbow smelt, overfishing, water quality issues and habitat loss.

As of this time last year, McDonnell noted that cisco are concentrated into the northern part of the lake’s main basin, and that there is no known population in the main basin or Saginaw Bay. So the USFWS and its reintroduction project partners first began collecting fish and gametes from the northern Lake Huron cisco populations in 2017. Upon being reared at a hatchery, the fish are stocked into the lake. This began in 2018, and has included stocking of cisco near Tawas City/East Tawas.

The intent has been to stock at least one million fingerlings annually, for a minimum of 10 years.

As McDonnell and others have mentioned, cisco were historically an important commercial fishery. The belief is that they can provide an important component for commercial and recreational fisheries in the future, as well. Moreover, they would contribute to the prey base in Lake Huron.

Like Fielder, McDonnell said that cisco may provide a buffer for YP. They vary from other pelagic prey fish and occupy a slightly different niche. “And that niche is more in line with the historic fish community. So we’re hoping that we’re able to fill that niche once again,” he said at the time.

As for the consequences of YP now essentially becoming a forage fish, Fielder shared that both the recreational harvest and angler CPUE in the bay, year-round, has dropped to very low levels from what existed as recently as the ‘80s and early ‘90s. Some of the more current harvests are virtually at zero, compared to past years.

“It would not be an exaggeration to say our yellow perch recreational fishery has collapsed in Saginaw Bay,” he continued. “Now that’s not to say there aren’t some times and places where we have some good perch fishing.” But on the whole, according to DNR creel surveys, it is down significantly. “And we know that the bay is capable of producing a much better yellow perch fishery than that. So this is a major source of concern for us, still.”

Backing this up, is data associated with a state-licensed trap net fishery that operates mainly in the inner bay for YP. The round pounds of yield, or harvest, in the commercial fishery has also taken a drastic dip. For example, it was at about 120,000 pounds in 1995. In 2021, it was less than 20,000 pounds.

So the commercial and recreational fishery are each trending the same way and suffering from the same problem, Fielder said.

He showed an image representing the total annual mortality rate for age 1 and older YP. It excluded the high mortality between the age zeroes and age ones he discussed earlier, which can be as much as 95-99 percent in some years. Highlighted on this slide, then, was the mortality rate of those few YP which do survive.

“And it’s pretty steady,” Fielder said. It’s right around 58-60 percent, which normally wouldn’t be a problem for a YP population. But if there’s a lack of recruitment coming in, then it’s an issue.

The real problem, though, is the initial bottleneck between the age zero and age 1 fish. If there’s a silver lining, it’s that the YP which do reach age 1 and older are growing very fast compared to the state average, he said. And while there isn’t enough of them, at least they’re fairly large. This is just added confirmation, however, that the population is subsisting well below carrying capacity.

Workshop participants could pose questions to the presenters, and one attendee asked if Fielder was concerned with the number of YP spawning in Saginaw Bay.

“I’m concerned about the mortality,” he answered. Right now, there appears to be enough that are surviving to become mature and spawn, to where they’re still achieving strong year classes. “So no, right now I don’t think we’re limited by the amount of broodstock, if that’s the question.”

He said the question was logical, considering how small the YP population is becoming. “But even at those small levels, I think there’s a lot of spawners out there that we’re still getting good reproduction. So it’s really a mortality problem, not a reproduction problem, for perch.”

Another individual asked if the low recruitment of YP to age 2 can be related to food web issues.

Randy Claramunt, DNR Fisheries Management, said it can certainly be attributed to the high walleye population and the fact that surveys document a lot of age zero YP, but it drops off quickly.

So predation is playing a role but he also thinks that these are somewhat related in terms of the growth of young fish, their habitat and their ability to avoid predators, all of which are contributing.

Fielder agreed, adding that he thinks the question was trying to get at the food web changes that played out in the early 2000s, with the disappearance of alewives. “That was a big driver.”

There’s somewhat of a debate as to why this transpired. Was it the result of invasive mussels disrupting the food web, or because so many predators consumed alewives? Fielder says it’s probably some of each that caused them to largely vanish from Lake Huron.

He noted that it had great benefits for the reproductive success of native species, including perch, walleye and lake trout. But there was a major downside, too, with consequences for the popular pacific salmon and chinook fisheries.

He reiterated that alewives were a buffer for predation and protected young YP, since walleye and other predators were instead eating the abundant alewives.

“But remember, alewives were an invasive species,” Fielder said, noting that they arrived in the 1950s. Prior to that, cisco likely spawned heavily in Saginaw Bay, and their offspring used it as a nursery ground for maybe the first summer. This probably created a lot of forage, which also provided the buffer for YP.

There used to be a huge population of both walleye and YP in the bay, he said. “You can have both. There should be no reason we can’t.” But researchers are discovering that there’s an important linkage between the main basin – the source of such pelagic planktivores as alewives and cisco – and Saginaw Bay. “And that linkage appears to be broken.”

So while walleye recovery targets have been met and there are many good things occurring in the bay, problems remain and some of the historical linkages aren’t there.

“That’s the whole idea behind this cisco restoration project, is to try to jump start that,” Fielder went on. It will be a long-term solution, if it even works, in the attempts to benefit YP.

This is why agencies like the DNR have been trying to do something in the more near-term, such as through the liberalized walleye harvest regulations which were reported on in last week’s story.

“Frankly, it hasn’t worked out the way we tried,” Fielder said.

He remarked that it was a bold move and he thinks they deserve a lot of credit for trying these things. Researchers have also learned plenty, but the walleye population is really governing itself and they haven’t yet solved that problem, as it pertains to YP. “There’s no easy answer when it comes to perch.”

Southern Lake Huron Unit Manager Jeff Jolley, DNR Fisheries Division, also spoke during the workshop and shared that the department has been involved in a new management plan for the Saginaw Bay walleye and YP fishery.

He said that the walleye have gone from a crashed and depressed population, to recovery. This was aided by some serendipitous natural events, as well as bolstered by stocking, and the population eventually became extremely abundant and completely self-sustaining.

The DNR has been revisiting what they want out of the population and, as part of this, Jolley has teamed with a workgroup of citizens to formulate a vision for what they want to see with the fishery also. It entails such elements as a high-quality, sustainable/resilient fishery; incorporating both science-based decisions and angler values; investing in habitat improvements; and maintaining the diversity of species, seasonality, accessibility and anglers.

Another element is to improve the YP fishery, with a focus on harvest opportunity and prey base.

People understand that it’s complicated, Jolley said, but they are disappointed with the YP situation. They want it to improve because they remember the value it brought to anglers and the bay, when there was a great YP fishery.

The vision elements will be boiled down into goals for both walleye and YP. The exact wording is still being refined, but for the former, the general goal is to support a self-sustaining walleye population that balances high-quality and diverse angling and harvest opportunities, protection of reproducing fish and appropriate utilization of the prey base. The goal for YP is to support a population which provides harvest opportunities for anglers, in addition to a prey base for walleye.

The citizens’ hopes for the walleye fishery was likened by Jolley to the balance that researchers are trying to get with the population of walleye, versus perch, versus the other prey species.

As for some upcoming changes, he said that the walleye fishery in Saginaw River is currently closed from March 16 until the last Saturday in April, but this will not be the case next year. “So, from the Center Street bridge in Saginaw, downstream to the bay, year-round in 2023, the walleye fishery will be open.” The same regulations will be in place as those that apply to the bay, which is a daily possession limit of eight fish and a minimum size of 13 inches.

Jolley said that people of course have to abide by the waters that they’re fishing in since, upstream of the bridge, there will still be a closed season for walleye harvest. “But there are some other species that are legally harvestable at that time, so there are currently gear restrictions in place that will remain in those waters; but when we open the Saginaw River stretch for walleye harvest, we will remove those gear restrictions, as well.”

According to Jolley, there’s an abundant walleye population here, with plenty of fish in the river for those six weeks and lots of chances to catch them. “And we really thought that this could provide more opportunity.”

He said that the department is hoping this move will be very successful, and added that DNR creel clerks will be monitoring the fishery during this time.

As it relates to YP, walleye aren’t the only source of mortality. Along with having already reduced bag limits for YP from 50 to 25 in the state and liberalizing walleye harvest regulations, Claramunt says that the DNR is also implementing cormorant control at the level to which they are allowed under a new permit system, as well as doing what they can to address other YP predators.

He advised that managers can only do so much in terms of fishing regulations and the like, after which, it’s really up to Mother Nature to determine the future of YP.

Several different Lake Huron Regional Fisheries Workshops were held this spring and the annual events are put on by Michigan Sea Grant and Michigan State University-Extension, in partnership with the DNR Fisheries Division, USGS Great Lakes Science Center, USFWS and local fishery organizations.

For the Saginaw Bay session, the USFWS also discussed lake sturgeon restoration efforts, and a water quality status update was shared by the Michigan Department of Environment, Great Lakes and Energy. To view either of these segments or the workshop in its entirety, Michigan Sea Grant has posted a video recording, at https://youtu.be/qTKGOHJJJPk.

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