The arrivals: zebra mussels in the river, and carp at the gate

1988–2023, the invasive record · Run B #224

The arrivals are named on the state's own lists, and the feared one has not arrived: Zebra mussel. Dreissena polymorpha, first found in North America in Lake Erie in 1986 and in all the Great Lakes by 1990, stands on the Indiana DNR's official Zebra Mussel Waters list — updated 12 January 2026 — for the St. Joseph River in St. Joseph County (and in Elkhart and Allen counties along the same river system): the river at this township's frontage is a listed zebra-mussel water. The mechanism is documented for this basin specifically — Notre Dame researchers (Bobeldyk, Bossenbroeck, Evans-White, Lodge and Lamberti, 2005) sampled zebra mussel populations in coupled lake-stream systems of the St. Joseph River basin in 2000 and 2003 and found the spread running downstream from invaded lakes, adult densities declining with distance below lake outflows, a source-sink pattern rather than a marching front. Indiana's Mussel Rule (312 IAC 9-9-3) makes the zebra mussel, the quagga mussel and the Asiatic clam prohibited species — illegal to import, possess or release. No zebra-mussel record specific to Baugo Creek stands in the sources reached, and none is printed: the listing is the river's, at the township's frontage. Carp at the gate. The gate is the river's mouth stair — the Berrien Springs dam reach and the lower river between Lake Michigan and Berrien Springs, the first barrier water an invader from the lake must pass. The record there is an eDNA story, told whole: of 220 water samples collected by the U.S. Fish & Wildlife Service in June 2023 from the lower St. Joseph River, one, taken near Marina Island at the river's mouth, carried silver carp eDNA; a 220-sample resampling on 6 September 2023 found no bighead or silver carp eDNA at all, and the Michigan DNR's aquatic invasive species coordinator concluded it is "unlikely that live silver carp are present in the St. Joseph River," with monthly electrofishing and netting over two summers capturing grass carp for removal but no silver carp. The agencies' own caution stands in the record: a positive eDNA sample does not necessarily indicate a live fish. The verdict at the gate, as of the 2023 record: bighead and silver carp are not known to be in the Great Lakes basin, and no established carp population stands in this river — one molecule's alarm, a clean resample, and a watched gate.

Sources: Indiana DNR, Indiana Zebra Mussel Waters list, updated 12 January 2026 (St. Joseph River listed for St. Joseph, Elkhart and Allen counties); Indiana DNR aquatic invasive species record (Mussel Rule, 312 IAC 9-9-3; zebra, quagga, Asiatic clam prohibited); USGS Nonindigenous Aquatic Species profile, Dreissena polymorpha (Lake Erie 1986; all Great Lakes by 1990; Indiana first observed 1988); Bobeldyk et al., "Secondary spread of zebra mussels in coupled lake-stream systems," Écoscience 12(3), 2005 (St. Joseph River basin sampling 2000/2003; source-sink model). Carp: Michigan DNR / U.S. Fish & Wildlife Service eDNA record as reported September–October 2023 (one silver carp eDNA positive of 220 June samples near Marina Island; 220-sample resample of 6 Sept. 2023 all negative; Lucas Nathan, Michigan DNR, quoted; grass carp removals; no silver carp observed or captured). No Baugo Creek zebra-mussel record was reached, and none is claimed.