I asked GROK 4 AI if the imposition of menhaden catch limits caused the northward expansion of the menhaden population and this was the response:
Yes, the 2012 imposition of coastwide catch limits (the first Total Allowable Catch or TAC, implemented in 2013 via ASMFC Amendment 2) influenced the northward expansion—or more precisely, the recovery and increased abundance of Atlantic menhaden (Brevoortia tyrannus) in the northern parts of their historic range.
Menhaden naturally migrate northward in spring/summer, with larger, older adults traveling farthest (to New England, the Gulf of Maine, and sometimes Nova Scotia/Canada). Their overall range has always extended from Florida to Nova Scotia, but abundance and geographic distribution have fluctuated. In the 1960s, heavy fishing caused a geographic contraction: northern reduction factories (e.g., north of Chesapeake Bay) closed due to scarcity, and menhaden largely disappeared from areas like Maine for periods. Similar dips occurred in the mid-1990s.
The 2012 ASMFC action responded to a stock assessment showing overfishing. It set a coastwide quota (initially cutting harvest ~20–25%, later adjusted), ending unrestricted fishing and shifting to science-based limits. This reduced fishing mortality, allowed more fish to survive longer, and boosted spawning stock biomass and overall abundance. Key effects tied directly to northward expansion/recovery include:
- More older/larger fish reaching northern waters: Older menhaden migrate farthest north. Lower harvest lets fish live longer and reach places like Massachusetts waters in greater numbers. A Massachusetts Division of Marine Fisheries biologist (and ASMFC Menhaden Technical Committee member) stated: “By limiting harvest, the plan permits menhaden to live longer, thereby increasing their presence in Massachusetts’s waters.”
- Regain of historic northern range: Post-2012/2013 TAC, menhaden reappeared in stronger numbers from New Jersey to Maine (including Martha’s Vineyard schools, rocky Maine coastlines). Bait landings rose in northern areas due to higher availability. Experts attribute this recovery explicitly to management: “Menhaden have begun to regain their historic northern range. And where they’re reappearing, predators are following.” Management shifted “from no coastwide limit to science-based management and a significant recovery.”
- Recent observations align with quota timing: Increased sightings and schools in northern coastal waters (e.g., thick surface schools off NJ/NY) and resurgence after a ~2009–2010s decline coincide with the TAC era. ASMFC notes bait fishery growth in the north post-TAC.
Other factors may contribute—such as climate-driven warming (potentially shifting distributions or affecting recruitment) or natural cyclical patterns in recruitment tied to ocean conditions—but sources directly credit reduced fishing pressure from the 2012 limits as a major driver enabling the rebound and northward abundance increase. Without the quota, overfishing would likely have continued suppressing northern presence, as seen in prior decades.
Later ASMFC updates (e.g., Amendment 3 ecological reference points) further refined management to protect menhaden’s forage role, sustaining these benefits. Recent assessments and proceedings also reference observed range expansion (stable southern indices with northern increases), consistent with management effects.
In short, the catch limits helped reverse prior contraction by boosting population resilience and allowing the natural migratory behavior of older fish to repopulate northern waters more effectively.