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Safe Alternative to Aquatic Herbicides Sterile grass carp have been safely used to replace toxic aquatic herbicides in 38 states since 1985. Millions of certified fish have been stocked in public and private waters. There is no reproduction in any watershed that requires sterile fish. This has safely prevented the use of millions of pounds of toxic aquatic herbicides. Grass carp biology Grass carp are big river fish and cannot spawn in lakes or small rivers for reasons I will try to explain. Grass carp need the stimulus of flowing water to produce mature eggs. Without that stimulus only immature eggs are produced. Only mature eggs can be released and fertilized. Grass carp can only reproduce in major rivers with 36 to 100 miles of uninterrupted flow. Simultaneously fast flowing and rapidly rising waters are necessary to trigger spawning. Increasing turbidity may also be necessary. The eggs are heavier than water and need fast current to keep them suspended as they float down river. If the eggs reach the slow water of a reservoir, a wide spot in the river or an eddy they sink to the bottom and die. The eggs must hatch near a suitable nursery area. Fertile grass carp were found in the St. Croix River in 1982 and have not spawned. Even as big as the St. Croix River is it is still probably too small or too short to provide the uninterrupted major flows necessary for this fish to spawn. It’s likely that there are few if any areas suitable for grass carp spawning in Minnesota. Sterile grass carp The procedure to produce sterile grass carp is quite interesting. The farmer injects each fish with multiple injections of artificial hormones. This is necessary to get the fish to produce mature eggs. The eggs and sperm are stripped by hand and mixed together. The fertilized eggs are then pressurized to 8,000 psi. The fertilized egg produces an extra set of chromosomes (called second polar body) that is normally expelled. The extreme pressure prevents the expulsion. This produces a fish with 3 sets of chromosomes instead of the normal 2 sets. Certification procedure Certified (sterile) grass carp have been safely used to control aquatic vegetation since 1985. The pressure process is not 100% effective so the farmer collects a blood sample from each fish. The blood sample is tested using a medical device called a Coulter Counter. Only fish that test positively as triploid are considered sterile and all other fish are considered fertile. The fertile fish are removed and sold in states that use fertile fish. The farmer notifies the United States Fish and Wildlife Service (USFWS). A USFWS agent comes to the farm and watches the fish tested a second time. The USFWS then certifies the fish as triploid. The USFWS notifies the receiving state of the destination of each fish. If the shipment is delayed more than 4 working days the fish have to be blood tested and certified again. Fertile grass carp smuggling I have told the MN DNR Fisheries that I believe fertile grass carp are being smuggled into our state. While sterile grass carp are highly regulated, fertile grass carp are virtually unregulated in some states. Before sterile grass carp were approved in California officials found 1,500 fertile grass carp in private ponds. Neighboring Wisconsin also found smuggled fertile fish in numerous private ponds. Minnesota has also found smuggled grass carp. It is a simple matter to smuggle fish in the back of the family wagon or possibly even have them shipped to your door. Billions of fish are shipped in bags with oxygen every year. I asked the Fisheries Director what the response would be if some smuggled fertile grass carp escaped into public water and the public found out that unregulated smuggling fertile fish might have been avoided by making it more convenient (and possibly cheaper) to use sterile fish than smuggle fertile fish. He refused to reply despite my repeated requests for an answer. Finally his assistant replied. He said that they preferred to rely on giving the DNR Enforcement Division the impossible task of preventing smuggling. That wipes the hands of the Fisheries Division clean of any responsibility. Avoiding responsibility seems to be the number one goal. Of the thirty-eight states that allow the use of grass carp only twenty-eight require them to be sterile. The remaining 10 states allow the use of fertile fish. Most of the 10 states that use fertile grass carp are in the Mississippi River basin. The DNR’s of many of those 10 states continue to stock fertile grass carp into public waters. Grass carp are reproducing in the Mississippi River basin because that is where fertile grass carp are stocked. Sterile fish or herbicides? Millions of sterile grass carp have been stocked in both public and private waters in 38 states since 1985. There has been no reproduction in any watershed that requires grass carp to be sterile. The top three states in duck stamp sales allow the use of sterile grass carp. The release of exotic species even into private ponds is always serious but the sterile grass carp certification program has a long track record of safety. It has safely replaced the use of millions of pounds of toxic aquatic herbicides. If aquatic herbicides are not used they cannot get into the fish we eat or our groundwater. |