Data from: Tracking two invasions for the cost of one: Opportunistically tracking the range expansion of non-native Palaemon macrodactylus in the Salish Sea through participatory science

While conducting early detection monitoring for invasive European green
crab (Carcinus maenas), Washington Sea Grant Crab Team discovered a
non-native shrimp Palaemon macrodactylus, hitherto unreported along
Washington's portion of the Salish Sea. By examining prior data, and
tracking this species closely over subsequent years, we were able to
consistently monitor the spread and increase of this species across the
region. The program and dataset enabled a highly quality-controlled and
verified record of this species. Originating near the Canadian border, P.
macrodactylus has spread southward into the main basins of Puget Sound and
has been observed in Hood Canal as well. At sites where this shrimp has
been consistently documented, the relative abundance over time has
increased, indicating that the invasion has become established but not yet
reached equilibrium. Similar to studies in other regions of the globe
where it is found, we observed that P. macrodactylus favors estuarine
habitats and demonstrates seasonal migration within creek systems. The
Salish Sea population is within demographic values published for other
invasions, but females achieve a smaller maximum size, and reproductive
maturity at a smaller size than those reported from the native range. This
might suggest the potential for an altered life history strategy favored
by an introduction to a novel evolutionary context. Given the rate of
spread over the last decade and the density of suitable habitat, we
anticipate that P. macrodactylus will continue to expand its range within
the Salish Sea. No ecological impacts of this species have been documented
elsewhere. Nevertheless, this approach demonstrates the benefit of
participatory science monitoring in tracking cryptic or otherwise
unnoticed species invasions.