Working Group on American Eel (WGAMEEL; outputs from 2024 meeting)

The Working Group on American Eel (WGAMEEL) wrapped up its 2022–2024 term with a virtual series of three meetings that tackled five Terms of Reference (ToRs). The agenda spanned data synthesis, spatial modeling readiness, Indigenous Knowledge Systems, and a practical roadmap for stock assessment and management. Here’s what fisheries managers, data scientists, and policy leaders need to know.

Data audit: landings, abundance, and habitat information

Under its first two ToRs, WGAMEEL catalogued and evaluated available data on American eel landings, abundance indices, and habitat, and documented assessment methods used in Canada and the United States. A Canada-wide trajectory was estimated using 12 fishery-independent datasets. The headline result: the longer the time series, the more negative the trend. When analyses were restricted to post-2000 data, negative trends were fewer and generally not distinguishable from zero—pointing to the bulk of declines occurring before 2000 rather than continuing uniformly into recent decades.

This finding carries practical weight for assessment design: short modern datasets may understate legacy declines, while long archives better capture the historical drop. Both perspectives are necessary to understand status and recovery trajectories.

Mapping eels across three worlds

American eels traverse freshwater, estuarine, and marine environments, and robust spatial modeling has to reflect that breadth. Recent years have seen a surge in online aquatic databases—especially for freshwater systems—while estuarine and marine datasets remain more unevenly documented. WGAMEEL compiled abiotic time series relevant to eels (for example, environmental conditions that drive distribution and survival), providing a foundational layer for habitat-informed analysis.

The limiting factor isn’t just environmental context; it’s biology on the map. High-quality, georeferenced biological observations—occurrence, abundance, and time-stamped trends—are still too sparse to support comprehensive spatial models across the species’ range. Addressing that gap will require coordinated monitoring, standardized metadata, and open, interoperable data infrastructure.

Indigenous Knowledge Systems: place-based insight

For its third ToR, WGAMEEL surveyed First Nations representatives across four Canadian provinces. Respondents affirmed the cultural significance of eels within their communities and emphasized that Indigenous knowledge is inherently place-based and contextual. This includes granular understanding of local threats—information that can be pivotal for site-specific management measures and for interpreting scientific indicators through a community lens. Integrating these knowledge systems can improve problem framing, prioritize protections where they matter most, and enhance trust in management decisions.

Assessment pathways: what can be used now, and what’s next

WGAMEEL assessed a spectrum of approaches applicable to American eel (and in some cases European eel), weighing data demands against the urgency of advice. Two options stand out for near-term use due to minimal data needs:

• Index-based methods: Management guidance derived from standardized abundance indices, suitable when detailed life-history or catch data are limited.
• Catch-only methods: Approaches that infer stock status from catch history, useful for data-poor contexts or as an interim signal.

More ambitious but higher-value approaches will take longer to implement because they require richer data and calibration:

• Spatial or habitat models that integrate environmental drivers and georeferenced biological observations across freshwater, estuarine, and marine domains.
• Management Strategy Evaluation (MSE), which stress-tests candidate rules and reference points against uncertainty before adopting them.
• Spawner-per-recruit (SPR) analyses, potentially paired with meta-population models to reflect connectivity and life-cycle complexity across regions.

Together, this progression offers a pragmatic bridge: adopt low-data methods now to inform management, while investing in the data systems needed to enable spatially explicit and strategy-tested decisions in the future.

Why it matters

American eel management sits at the intersection of data science, conservation, and cultural stewardship. WGAMEEL’s outputs underscore three imperatives: respect historical baselines when interpreting modern trends, build geospatially rich biological datasets to unlock next-generation modeling, and bring Indigenous, local, and scientific knowledge into a shared evidence base. This layered approach improves both the precision and the legitimacy of management advice.

Key takeaways

• Most observed declines likely predate 2000; shorter post-2000 datasets alone can miss that signal.
• Freshwater data coverage has improved; estuarine and marine data remain patchier and need attention.
• The biggest bottleneck for spatial modeling is a lack of high-quality, georeferenced biological observations.
• Indigenous Knowledge Systems provide vital, location-specific insights on threats and use.
• Index-based and catch-only methods can inform near-term management; spatial/habitat models, MSE, and SPR (potentially with meta-population models) are the medium-term horizon once data mature.