Using New Technologies for the Control of Filter-Feeding Aquatic Invasive Species Like Asian Carps

Asian carp, especially the filter-feeding silver Hypophthalmichthys molitrix and bighead carp H. nobilis, threaten ecosystems. Presently, resource managers are limited to rotenone or antimycin-A to control these aquatic invaders.  Unfortunately, these piscicides impact both Asian carps and non-target ecologically important species.  Developing a management chemical that is more “carp-specific”, or a method to more specifically deliver current chemicals, is highly desirable.  A targeted delivery system which exploits the planktivorous feeding habits of Asian carp and differences in their digestive enzymes from those of native planktivores has the potential for greater selectivity than current piscicide applications. We are evaluating whether Asian carp 1) will consume the particle, 2) consumes specific particle sizes or 3) possess different levels of specific digestive enzymes. In a filtration study using particles incorporated with astaxanthin, we found that both silver carp and bighead carp consumed particles from 50 µm to 150 µm, a size not consumed by paddlefish (Polyodon spathula). As predicted from literature, silver carp seemed to prefer particles around 70 µm. From intestinal scrapings of feral planktivorous fishes, Asian carps have higher levels of digestive phosphatases in their fore-guts than gizzard shad (Dorosoma cepedianum) and bigmouth buffalo (Ictiobus cyprinellus).  Sampling in March of 2011 indicated that silver carp were actively eating and had full intestinal tracts whereas the intestinal tracts of native planktivores were devoid of food.  These preliminary studies suggest that the use of targeted delivery systems show promise to deliver “piscicidal” particles to Asian carps and other filter feeding aquatic invasive organisms.