Growth patterns of invasive Silver Carp in the Mississippi River basin

ABSTRACT Silver Carp Hypophthalmichthys molitrix are an invasive fish in the Mississippi River basin. Their rapid expansion over recent decades, coupled with extraordinary growth rates, has arguably caught many by surprise. Understanding the atypical growth rates that could be the driving force behind the Silver Carp's explosive expansion may be crucial for development of management strategies. Towards this goal, I synthetized existing data on the growth and maturity patterns of Silver Carp. I compiled 62 estimates of growth representing populations of native Silver Carp in East Asia and invasive Silver Carp in the Mississippi River basin. A remarkably rapid increase in length at earlier ages, undocumented in their ancestral range, was a defining feature of Silver Carp in the Mississippi River basin. Some of the fastest growth rates of Silver Carp were recorded in hypereutrophic floodplain lakes and at lower latitudes. Invasive Silver Carp frequently deviated from the growth patterns established by native species as evidenced by abnormally high growth coefficients (K) in relation to asymptotic length (L∞). There is evidence of genetic differentiation between native Silver Carp and those expanding in the Mississippi River basin, possibly resulting from genetic background of introductions, genetic drift, and ecological selection. There is also limited evidence of enemy release, allowing for reallocation of energy from defenses to rapid growth; though speculative, this is a plausible hypothesis that merits further research. This overview of the growth patterns of invasive Silver Carp underscores the need for novel strategies to mitigate the rapid generation time induced by the atypical growth patterns.