Aquatic invasive species pose a significant ecological and economic threat in the Great Lakes basin. Early detection of invaders is desirable so as to allow for timely and rapid management response, raising the question of how early detection can be consistently and efficiently accomplished. To that end, we have been conducting intensive sampling of benthic macroinvertebrates and fish in the Duluth-Superior harbor/St. Louis River embayment on Lake Superior.

Results/Conclusions

This water body is subject to heavy propagule pressure from international shipping and recreational fishing, and our sampling detected a variety of both "old" and "new" invaders (e.g., common carp, rainbow smelt, tubenose goby, zebra mussel, New Zealand mud snail). Our deliberately oversampled data set provides the basis with which to evaluate sampling strategies (gear types, spatio-temporal distribution, use of ancillary environmental predictors, etc.). Analyses confirm that early detection of invaders is inherently an inefficient process, with increasing amounts of effort required to detect the next new or rare species. Detection probability depends not only on species abundance, but also on spatial distribution and vulnerability to sampling gear. Species acquisition curves, species ordinations, and species traits metrics differed substantially among the types of fish and invertebrate sampling gear used, and the gears catching the largest numbers of individuals were not necessarily the ones that most rapidly detected invasive species. Use of ancillary information on introduction pathways and ambient habitat helped to identify strategies for most efficiently detecting invasive species. This abstract does not necessarily reflect EPA policy.