For nearly three-quarters of a century potholes played a pivotal role in waterfowl management. In dry years, when the number of breeding potholes across the northern prairies declined alarmingly, season lengths and bag limits were reduced to protect our breeding stocks. In wet years authorities allowed long seasons and high bag limits.

An exception occurred during the years 1980-84 when biologists conducted the Stabilized Regulation Study. Many concerned waterfowlers protested the continuation of high bag limits and long season during years of low to average water, but they were ignored. The liberal duck seasons were justified in the name of “science.” When the study ended the mallard population had fallen to a record low.

Waterfowl managers today apparently have forgotten, or choose to forget, the pothole-based management policy of the past. This is the only interpretation that can explain the silence that greeted Adaptive Harvest Management’s revised regulatory protocol initiated in 1997, the year authorities first allowed the longest seasons and highest bag limits in nearly half a century.

This is especially troubling because the productivity of the prairies has declined alarmingly since 1990 (See The New Pothole Truth, March 6, 2003). The prairies no longer produce an explosion of young ducks during wet years. This calls into question the underlying biological rationale for varying season lengths and bag limits.

But declining juvenile productivity is only part of the problem. Another issue is how Adaptive Harvest adjusted to this change.

We begin by examining mallard juvenile productivity as measured by age-ratios, the number of juveniles per adult in the hunter’s bag in the Mississippi and Central Flyways. We break these down by North American water conditions into averages for the years 1974-96 and 1997-2001. Low water is defined as 2 million to less than 4 million potholes. Average water is 4 million to less than 6 million potholes, and high water is more than 6 million potholes. The long-term average is 5 million potholes. All data is from the U.S. Fish and Wildlife Service.

JUVENILE PRODUCTIVITY

As you can see, the number of juveniles per adult has declined significantly since 1997 during low and high water years, remaining steady during years of average water. The overall average under all pothole conditions suggests 11 percent fewer juveniles accompanied adults during the fall migrations from 1997-2001.

How has Adaptive Harvest reacted to these increasingly thin migrations? The following table shows the average annual mallard kill per pothole for the same time periods and water conditions. The kill per pothole is determined by dividing the Mississippi and Central Flyway harvest by the number of North American potholes. (The two flyways account for most of the kill of ducks raised on the northern prairies.)

KILL PER POTHOLE

As you can see, the number of mallards killed per pothole has increased significantly under all prairie water conditions. The overall average is 36 percent.

Thus, while pothole productivity declines, the kill per pothole increases.

Importantly, the goal of waterfowl management is to maintain an average population of 8.8 million breeding mallards. To achieve this goal, Adaptive Harvest each year sets the regulations (liberal, moderate, restrictive, very restrictive and closed) based on the number of Canadian potholes and North American mallard breeding population.

The number of Canadian potholes has ranged from a high of 6.4 million to a low of 1.4 million. The long-term average is 3.4 million.

Currently, if the number of potholes totals only 1 million (29 percent below the record low count and 71 percent below the long-term average, thus insuring minimal juvenile production)) and the mallard breeding population is 8.5 million (4 percent below the population goal), Adaptive Harvest calls for a liberal regulatory package to maximize the kill.

Under these conditions, would a rational person expect the population to increase the following spring? Could we expect the number of breeding mallards the following year to reach the aforementioned population goal?

These analyses reveal why Adaptive Harvest is fatally flawed. It diminishes the critical importance of potholes. It suggests we can produce less and kill more -- and continue to maintain an abundance of ducks.

Isn’t it time to junk Adaptive Harvest?