Author’s ‘fish pig’ observations warn of Asian carp potential
I was watching my “fish pig” at work in the pond the other day and went into the house shaking my head over the potential threat that Asian carp, beyond the problematic and well-established common carp, pose to our Great Lakes.
My fish pig is a triploid, or sterile, white amur, also known as a grass carp. It is into its third summer in my little quarter-acre pond and has more than quadrupled in size since I dropped it in. The goal was to allow it to do what it does best – act as an aquatic Hoover by vacuuming up nuisance pond vegetation that once threatened to choke my pond to death. No more.
The grass carp in fact has done its job almost too well. I started to realize that last summer. I had virtually no rooted pond vegetation left, which left the thing to rooting up the shallows like a pig snuffling for truffles in a forest. The rooting stirred up muddy sediment and turned the water from clear to chocolate milk. In turn, that limited light penetration and further vegetation growth.
But a pond needs some vegetation for the whole thing to work in synch. Vegetation – enough but not too much – encourages aquatic insects, which feed tiny fish and more, and so on up the line to such preferred species as largemouth bass and bluegills. It all is a delicate balancing act that nature can do at will in a larger system, but which demands constant tinkering in a manmade pond like mine.
I watched the grass carp at length, slowly and doggedly finning its way along the pond’s edge, twisting its now 5-pound body this way and that, the mouth always moving. Rooting and chomping. Chomp, chomp, chomp. I almost gagged watching it suck down one of the few remaining long, stringy pond plants (I hesitate to say the “weed” word, as the term only denotes our ignorance). This fish is relentless.
Which brings me to my concern: The grass carp is present in fertile form in the Sandusky River system and in Lake Erie, though numbers appear to be small as of now. Its potential as a threat to native fisheries appears to be minimal – appears to be. But it is a first cousin to two other Asian carp – the dreaded silver and bighead carp, which so drastically have altered the Mississippi River watershed in just 40 years and which lie posed to pounce just miles from the Great Lakes in the Chicago Ship Canal network.
Now, silvers and bigheads are filter-feeders, not plant-chompers like the grass carp. But a summary paragraph about them from the neighboring Michigan DNR says it all: “Bighead and silver carp are filter feeders, straining tiny plants (phytoplankton) and animals (zooplankton) out of the water. By eating plankton, the carp compete with native filter feeding fish, such as lake whitefish, as well as the young life stages of many fish species such as walleye and yellow perch.”
These carp all are relentless, prolific, and unstoppable feeders once on the loose. If I have to, I have been advised that I can easily remove my fish pig by bowfishing. Problem solved. And I can easily restock with another small grass carp when, not if, the pond vegetation takes hold again. But we will never be able to bowfish the bigheads and silvers out of the Great Lakes if their limitless appetites are ever unleashed.