DMF presents eDNA pilot showing winter flounder presence across Cape embayments; agencies flag data gaps and request more monitoring

The Massachusetts Division of Marine Fisheries (DMF) told summit attendees it has found winter flounder environmental DNA (eDNA) in multiple Cape Cod embayments and is expanding sampling and paired net surveys to better inform time‑of‑year (TOY) restrictions tied to spawning windows.

"We actually found winter flounder eDNA in all the embayments that we sampled," DMF presenter Dan McKernan said, reporting results from a multi‑year pilot that included twelve months of sampling in 2021–22 and follow‑up years with paired fyke‑net surveys.

DMF described the pilot as a step to address a major data gap that complicates dredging windows. The agency said it began a 2021–22 pilot with the Gloucester Marine Genomics Institute (GMGI), sampling six embayments for a year to detect winter flounder DNA. In subsequent winters DMF paired eDNA sampling with fyke‑net catch data in Buzzards Bay/Falmouth embayments; this past winter DMF expanded sampling to the North Side of the Cape and again collected fyke‑net and beam‑trawl data where possible.

DMF said eDNA detections aligned with fyke‑net catches: when DMF recorded higher eDNA signals the fyke nets catch rates were higher as well, and DMF reported catches of winter flounder in spawning condition in multiple embayments during the sampling program. The agency characterized the method as a promising, lower‑effort way to detect the presence and seasonal timing of spawning activity across many embayments, while noting that eDNA interpretation still requires paired conventional surveys to refine quantitative thresholds.

DMF officials said funding is a constraint: they reported more collected samples than they currently have funding to process and said additional laboratory analyses and sustained monitoring would be needed to turn eDNA into a routine decision tool for TOY waivers. The agency expects its ongoing work to inform future, site‑specific waiver decisions and to support adaptive management and monitoring as potential ways to allow additional dredging days where local data justify that approach.

Local officials at the summit pressed for clarity because TOY restrictions affect dredge scheduling and local economies; Chatham officials noted ongoing delays linked to recent red knot mapping and related consultations that are affecting that town’s permit timing.