Zebra mussel (Dreissena polymorpha) distribution in Apostle Islands National Lakeshore: SCUBA-based search and removal efforts: 2019–2020
Bibliographic record
Abstract
Invasive zebra mussels (Dreissena polymorpha) were first observed in situ at Apostle Islands National Lakeshore (APIS) in 2015. This report builds on 2018 SCUBA surveys and Environmental Protection Agency (EPA) veliger sampling to: 1) determine whether shoals on APIS borders act as sentinel sites to corroborate veliger drift hypotheses about invasion pathways, 2) evaluate ongoing hand-removal of zebra mussels from easily identified structures, and 3) continue efforts to assess native unionid mussel populations, particularly where zebra mussels are also present. Standard catch per unit effort survey methods by SCUBA teams were used to determine the distribution and relative abundance of zebra or quagga mussels (dreissenids) and native mussels (unionids). Zebra mussels were present at densities between 3 and 42 n/diver/hr (number of mussels per diver per hour), while native unionids were present at densities between 5 and 72 n/diver/hr. Shoal surveys (Eagle Island shoal, Sand Island shoal, York Island shoal, Bear Island shoal, Oak Island shoal, and Gull Island shoal) showed zebra mussels were more abundant on the west side of APIS and absent on the easternmost shoal (Gull Island), corroborating veliger work by the EPA that suggested drift from the Twin Ports of Duluth, Minnesota, and Superior, Wisconsin, is one pathway of invasion. Our results support the use of shallow shoals along the periphery of the park as sentinel sites gauging zebra mussel immigration and population dynamics. Zebra mussel densities in the central islands showed no obvious spatial pattern, and this survey cannot determine whether currents or human transport (or both) are invasion vectors. Given the mussels’ continued presence at heavily used mooring areas and docks where there are no zebra mussels on nearby natural features (e.g., Rocky Island dock, Stockton Island mooring areas), our findings are consistent with multiple invasion pathways (drift from the Twin Ports and anthropogenic sources at mooring areas). SCUBA search and removal of zebra mussels from docks was confirmed to be an effective method for significantly lowering the risk of zebra mussels reproducing and dispersing from these locations. We caution that this work is being done on what look like initial invasions at low densities. Repeated removal of zebra mussels by divers reduced numbers to zero at some sites after one year (South Twin docks, Stockton Island NPS docks, and the Ottawa wreck) or decreased numbers by an order of magnitude (Rocky Island docks). Dreissenid densities were more persistent on the Sevona wreck and longer-term work is required to evaluate removal versus recruitment (local and/or veliger drift). Given the size of the wreck, we have tracked detailed survey maps to guide future efforts. Zebra mussels were again observed attached to native mussels near Stockton Island and South Twin Island. Their continued presence on sensitive native species is of concern. Native unionid mussels were more widely distributed in the park than previously known, with new beds found near Oak and Basswood Islands. The work reported here will form the basis for continued efforts to determine the optimal frequency of zebra mussel removal for effective control, as well as evaluate impacts on native species.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".