By Mary Ellen Klukow
Sauger and saugeye are two of the most heavily exploited fish in the Mississippi River’s tributaries. The many dams on these tributaries and on the Mississippi itself concentrate fish in their tailwaters, making overfishing an inevitability rather than a possibility.
Because of this, many populations of sauger and saugeye experience growth overfishing, which occurs when fish are being harvested before the maximum growth potential of the population can be reached, meaning that these populations are dominated by young, small fish.
Researchers from the University of Southern Illinois have looked into whether or not stricter harvest regulations have an effect on the exploited sauger and saugeye populations in the Mississippi and its tributaries. The scientists chose the Kaskaskia River and the Ohio River, both direct tributaries of the Mississippi, as their study sites, because both experience heavy angling pressure but have very different harvest regulations.
The Kaskaskia River currently has a 14-inch minimum length limit as well as a daily limit of six walleyes, sauger, or saugeye. The Ohio River, however, has no minimum length limit and a daily limit of 10 walleyes, sauger, or saugeye.
Using historical data from fisheries surveys, the scientists were able to determine a relationship between the regulations and sauger/saugeye population dynamics. In the Ohio, only 2% of all the surveyed fish measured over 15.8 inches, and the vast majority were no older than two years. In fact, studies from 1998-02 found absolutely no fish older than age 4. Sauger and saugeye populations from the Kaskaskia, however, exhibited a much larger size structure where fish older than 3 years were much more common.
This data alone doesn’t mean that overfishing is the problem; there was still the possibility that the sauger and saugeye were simply struggling to survive in the Mississippi River drainage.
To answer this question, the researchers looked at each population’s recruitment, or the number of fish surviving to enter the fishery. In both rivers, there were promising numbers of age-class 0 and age-class 1 individuals (fish younger than two years), implying that there was high and steady recruitment.
Futhermore, the individuals sampled were consistently in good condition and exhibiting high growth rates.
The study also noted that across all pools in both rivers, the 2012 year-class of fish was far and away the biggest and best established. The scientists believe the reason for this is that water levels fluctuated very little in 2012. Upon further investigation, they found that year-classes with poor catch rates almost always hatched during years with highly variable water levels.
The scientists concluded that the opportunity for a strong Ohio River sauger/saugeye fishery is there, but that angling pressure was truncating the population size structure. Individual fish in the Ohio were simply being removed from the population before they could reach a decent size.
Judging by the populations within the Kaskaskia, a reduced daily limit or a minimum length restriction – or a combination of the two – could significantly improve the Ohio’s populations.
It is possible that in the near future, legislation will be recommended to enact stricter harvest regulations for sauger and saugeye in the Ohio River and other Mississippi tributaries. Breaking down the logic behind these kinds of fisheries-management decisions can help us as anglers determine which option we want to support: lots of tiny fish now or lots of big fish later.