A recent discussion about Asian carp as a food source has generated some concerns about the level of contamination in their fillets, and thus, whether or not they are safe to eat. Several Indiana agencies cooperate to evaluate the risks of fish consumption to the public; the agencies include the Indiana Department of Natural Resources (INDNR), Indiana Department of Environmental Management (IDEM), Indiana State Department of Health (ISDH) and Purdue University. Most of the fish assessed for contaminants are those that are regularly caught by anglers. Numerous catfish, bass, sunfish and sucker species are commonly included in tissue surveys (see links below for more info). Indiana then divides people into two risk groups: 1) men (over 15 years) and women beyond childbearing age (typically 45 years or older) and 2) women pregnant or capable of becoming pregnant and children under 15. The second group is considered the sensitive group, and allowable contaminant levels (that is, the amount of fish that is safe to consume) are set significantly lower.
It is important to recognize that there are differences in allowable contaminants among population groups mentioned above, and it is equally important to recognize that the same fish species can have different amounts of contaminants in different water bodies. Asian carp are a riverine species that frequently travel long distances, and as such, they are exposed to varying levels of contaminants. Indiana and many other states try to minimize the effects of variation in individual fish fillet by combining tissue from multiple individual fish and analyzing it as a composite. Sampling the tissue as a composite reduces the risk of a heavily contaminated fish or a fish with little contamination, giving a false impression of the risk. By combining the fillets, Indiana also saves money by not analyzing large amounts of single fillets. Indiana does divide the fish into a couple of size classes for each composite because contamination increases significantly as fish size increases. They have yet to begin testing Asian carp fillets, at least partially because of their difficulty to capture using traditional fish survey techniques.
Although most states have not started regularly testing Asian carp, there has been some published research evaluating Asian carp fillets and comparing their contaminants to other species caught in the same location. Not surprisingly, the results of the research found that Asian carp have different concentrations of contaminants depending on where they are found, and they have different levels than other species of fish including common carp. Common carp have a completely different diet than Asian carp, so it is not surprising that contamination levels are different. Like most other fish, the most common problems associated with Asian carp are Mercury and PCBs. However, where the research was conducted in Illinois and Missouri, the recommended restriction on consumption was typically one meal per week for the most sensitive groups. Most studies have demonstrated that larger fish tend to have higher concentrations in their tissues than smaller fish found in the same environments. This relates to the way Mercury and PCBs bioaccumulate in tissues – the longer a fish is around, the more contaminants per gram we would expect them to contain. This is not to say that Asian carp in Indiana is safe for that level of consumption or that it even contains the same amount of contaminants as in other states. It still needs to be evaluated by the state, but studies cited below have shown that for the most part, Asian carp are likely no riskier to consume than most of the fish species that Indiana currently evaluates.
Fish Consumption Advisory
Indiana State Department of Health
Angling Indiana/Consumption Advisory by County
Asian Carp Solutions: Take Them to Market
Illinois-Indiana Sea Grant (IISG) Newsroom
No Bones AboutIt: New Video Lays Out Easy Steps For Filleting Tasty Asian Carp
Illinois-Indiana Sea Grant (IISG) Newsroom
Levengood, J.M., D.J. Soucek, G.G. Sass, A. Dickinson, and J.M. Epifanio. In press. Elements of Concern in Fillets of Bighead and Silver Carp From the Illinois River, Illinois. Chemosphere 2013.
Rogowski, D.L., D.J. Soucek, J.M. Levengood, S.R. Johnson, J.H. Chick, J.M. Dettmers, M.A. Pegg, and J.M. Epifanio. 2009. Contaminant Concentrations in Asian Carps, Invasive Species in the Mississippi and Illinois Rivers. Environmental Monitoring and Assessment