THE LAST CAST

When non-native species are introduced into a new area, does it always cause trouble by upsetting the “balance of nature?” Environmental activists and most resource managers are strongly opposed to “bait bucket” introductions in which anglers take it upon themselves to add new forage species and/or game species, usually top predators, to their favorite “fishing hole.” G enerally speaking; “it’s not nice to mess with Mother Nature;” however, we must remember that “change” is the most certain aspect of nature. The “balance of nature” is a human concept; an explanation and recognition of the fact that natural ecosystems stay largely unchanged over decades and even centuries. The species in each ecosystem and the relative numbers of species in the ecosystem remain in balance with other species as long as 200 – 300 years or even longer, unless disrupted by natural catastrophes or human activities. Energy and nutrients flow through balanced systems in functional and predicable patterns.

Humans have become a wild card in the game we call the “balance of nature” by changing environmental conditions, over-harvesting certain species, and adding additional species. Are the human-caused changes always harmful? Are they ever beneficial? It’s extremely difficult to predict the effects of every change; therefore, many biologists take the position of “the less you mess with Mother Nature, the better.” Some biologists have even developed mathematical models that claim natural ecosystems are as efficient as possible; therefore, any change introduced by humans will be damaging. Although I tend to prefer ecosystems that are as close to natural as possible, I recognize that change is inevitable, and I question some of the assumptions used in these “natural perfection” models.

Humans have learned to manipulate ecosystems to produce particular species that they want, including the introduction of species not native to the system. Civilizations throughout history have relied on managing and manipulating ecosystems to produce the food and raw materials needed for their societies to survive and, they hope, thrive. I, and other resource scientists and managers always hope that such manipulations will not upset the natural balance or cause the extinction of vulnerable species, species that evolved naturally in the system.

Unfortunately, the history of human attempts to improve on Mother Nature is marked with thousands of examples where changes resulted in unintended and unforeseen effects. Even when the desired results are obtained, the effort needed to maintain the new, unbalanced system is frequently far more than expected. Our entire agriculture system is based on production from non-native species; however, agriculture production requires major inputs of energy, as well as human time and effort. Simply introducing non-native plants and animals without additional energy and management efforts almost always results in chaos. This seems to be especially true in aquatic ecosystems where active management is more difficult than in terrestrial systems. Just adding something to system and walking away does not work.

Managing an ecosystem to produce a speQ A

cific desired effect requires a complex set of efforts and activities, unique to each ecosystem. Many factors are involved, and some important ones may be beyond the control of the manager. Years ago, when I was a young professor teaching environmental and resource management courses, the Dean of the Engineering College requested me to give a 3-hour evening seminar on the basic ecological principles involved in managing natural ecosystems. At that time engineers were under growing pressure to consider the effects of man-made systems and products on natural environments; however, their traditional course work focused almost entirely on simpler systems that had been designed for management by humans. After a brief introduction to the large numbers of components in a natural ecosystem and the array of variable factors interacting with those components, the young engineers would invariably ask, “Why do you biologists even try to manage systems that are so complex?” Engineers typically focus on systems and the functions within the systems that can be described in detail and controlled with near absolute accuracy and precision.

So… when an angler empties a bait bucket in his/her favorite lake, or captures and transports a favorite predator (walleye? northern pike? largemouth bass?) to a water that has always produced good smallmouth bass fishing, the odds are that the angler is screwing up a functional natural system. Western trout anglers are likely familiar with the case of Yellowstone Lake, where lake trout were introduced by those eager to pursue them in the Park’s largest lake; since then, the lake’s native Yellowstone cutthroat trout have not fared well and are now considered to be severely threatened by interactions with the lake trout.

In North America, natural ecosystems have evolved over thousands of years since the end of the last ice age. A complex balance that shows resilience to natural climate variations has developed in that stream, but the addition of an apex predator pushes the system beyond its limits. Resource managers attempt to evaluate and predict the effects of changes they are considering, especially introductions of species capable of reproducing, before making the changes. "Bait bucket fishery managers" rarely consider the multitude of factors related to their actions, and the "laws of unintended consequences" are enforced by Mother Nature.

About The Author

John Nickum, is a retired PhD. fishery biologist whose career has included positions as professor at research universities including Iowa State and Cornell University, director of the Fish and Wildlife Service’s fisheries research facility in Bozeman, MT, and science officer for the Fish and Wildlife Service’s Mountain-Prairie Region. He was inducted into the National Fish Culture Hall of Fame in 2008.

No rod has ever silenced all the variables.

No engineer has ever found a way to transfer back cast energy directly into forward accuracy.

No angler has ever erased all the doubt from his or her mind.

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