Outdoor Happenings (May, 2017)
By Mike Reiter
In early April, I attended the “Wisconsin Lakes Partnership Convention” in Stevens Point. There were a number of interesting seminars on the agenda and one that I found very informative was on “Asian Carp in Wisconsin” presented by Bob Wakeman, who is an aquatic invasive species coordinator with the Wisconsin DNR.
There has been a lot of press coverage on invasive carp the last few years and Bob’s presentation provided much detail into how they got here, what impact they have on the environment and what we can do to prevent their introduction into our lakes and streams.
When we say “Asian Carp” we are actually referring to a group of four distinct species of carp that have been introduced into the United States. They are the “Silver Carp”, the “Black Carp”, the “Big Head Carp” and the “Grass Carp”.
“Silver Carp”, are the jumping carp so often depicted on TV. They were brought to the US in 1973 to control algae in ponds because of their filter feeding capabilities and as a potential food fish. They will form large schools and when disturbed can jump up to 10 feet in the air and will reach a length of 3 feet.
“Black Carp”, can reach 5 feet in length and weigh up to 150 pounds. They were brought into the US in 1980 to control pond snails and mussels but escaped in the 1990’s. While they are not yet been identified in Wisconsin, they could make it up this way soon.
“Big Head Carp” were imported in 1974 to control pond algae and improve water quality. Being a filter feeder, they also consume zooplankton and will compete with many of our native fish species.
“Grass Carp” were introduced in 1963 for controlling weeds in fish ponds and in golf course water traps. These carp are very fertile and fast growing. They will grow to 2-3 feet long and weight upwards of 30 pounds. They will eat 3 times their body weight each day and will excrete half of that as undigested waste. Because of this, water quality suffers!
The presence of Asian carp is also being monitored by a technique called e-DNA. The “e” stands for environmental and the procedure for detection looks for trace DNA in water samples. In the absence of living fish, their possible presence can be detected by a process right out of the CSI handbook. The methodology of e-DNA is being improved upon and promises to be a welcome additional tool in the biologist’s toolbox to help to better understand the presence and movement of these fish.
Locally, to date, Silver and Big Head carp have been found in the general area where the St Croix River enters the Mississippi River. While a breeding population of fish are not now present, only time will tell if these fish will find a “fin hold” in this area and become the problem they have been shown to be further downstream!
All of these carp species are considered invasive species and there are strict rules that make it illegal to transport or possess these live fish. There are many guidelines in place to prevent the spread of these fish but, unless these rules are observed to the “letter of the law”,bad things can and will happen. Keep a watchful eye open and stay tuned!