November 10, 2017 — SEAFOOD NEWS — Joseph Smith is a retired marine scientist formerly with the NOAA Southeast Fisheries Science Center, Beaufort Laboratory, National Marine Fisheries Service. He was the principal investigator for the Menhaden Program with the Sustainable Fisheries Branch, where he supervised the collection of fishery-dependent data for the Atlantic and gulf menhaden purse-seine fisheries. He has written an op-ed on the debate before the Atlantic States Marine Fisheries Commission on reference points for the Menhaden stock.  Lenfest, whose 2012 book on Forage Fish sparked a huge debate, is pushing for a reference limit that would shut down fishing if the menhaden stock nears 40% of its unfished level.  Smith argues that this approach does not work for Menhaden, as there is no stock size recruitment relationship, and for that reason, no evidence that fishing based around current reference points is not fully sustainable for ecosystem functions.

His letter is below:

Since the Lenfest Forage Fish Task Force issued their publication, “Little Fish, Big Impact” in 2012, there has been an enormous focus on “forage fish” – small schooling stocks important food for larger marine predators.  Atlantic menhaden, a stock on which I worked for over thirty years as a scientist for the National Marine Fisheries Service, is now a subject of this focus.

Despite being abundant and widely distributed, the debate over menhaden centers on a looming decision by the Atlantic States Marine Fisheries Commission over how to adopt reference points that incorporate menhaden’s role in the ecosystem.  At the broadest level, this goal is impossible to argue against.

The pending question is to how best to get there.  Reference points must make biological sense to ensure a sustainable menhaden population, along with sustaining the coastal communities that the fishery supports.  Indeed, the Commission’s scientific advisors are currently working on ecological reference points, or ERPs, specific to menhaden and their ecosystem.  There should be no debate that Atlantic menhaden-specific ERPs are the most desirable.

The real issue is how to manage the stock in the interim.  Currently, menhaden are managed to sustain a high level of annual egg production.  While not typical, this works for menhaden because there is a very weak relationship between the number of spawners and population size.

Annually, the stock produces trillions of eggs, but their development into larvae and then young menhaden depends on factors such as winds, currents, water temperature, salinity, and predation.  Historically, there are instances where relatively large spawning stocks of female menhaden produced few young recruits to the population, while relatively small spawning stocks produced large numbers of young recruits.

This lack of what is known as a classic “stock-recruit relationship” is important to understanding the current debate because the “rule of thumb” which the Lenfest group developed for forage stocks is premised on it.  Lenfest devotees urge the Commission to adopt ERPs premised on maintaining 75% of an unfished population, and allowing no fishing when the stock falls to about 40% of this level.

Of course, to manage a stock for a predetermined level of abundance, there has to be some relationship between fishing effort and stock size; this also does not exist for the menhaden fishery.

More disconcerting is that the Lenfest 75%/40% approach may involve harvest cuts of up to 50,000 metric tons from current levels.  If the stock is determined to be only about 46% of unfished levels, the fishery would be very close to a shutdown.   Looking forward, if Lenfest advice is adopted and harvest levels curtailed in the near-term, what is the relevance of harvest advice which may evolve in a few years from the current menhaden-specific ERP work?  If the latter studies endorse appreciable increases in harvest, this could create a climate of regulatory “whiplash”, a situation which fisheries managers I believe should avoid.

The crux of the debate, then, is whether one believes there needs to be a reduction in menhaden catch to maintain a healthy ecosystem or whether the current, conservative management regime is working.  In my view, the system has worked well for the stock, the fishery, and ecosystem, particularly over the past decade.

The wisest alternative to “rule of thumb” management advice is maintaining the current reference points which are specific to Atlantic menhaden.   I support the current single‐species reference points until the ERPs are developed by the Commission’s scientists.  Next year in 2018, the ERP working group will hold data workshops to select and standardize data that will be used as model inputs; this includes data that pertains not only to menhaden abundance, but also the abundance of bluefish, striped bass, and other predator species.

The ERP group is comprised of state and federal scientists who have spent a significant portion of their careers working on ERPs for menhaden.  The Commission sent them down this path several years ago.  Stay the course, let them finish their work, and present their results as planned in 2019.   The menhaden population currently has a broad age structure with six or more age classes represented, the population is expanding into the northern half of its range, and recruitment in recent years is above average – the sky will not fall on the menhaden population in the interim.  Given menhaden’s current stock status, allowable catches could increase 10% with no discernable impact to the population.

In the end, the Commission should follow the advice of its scientific advisors who have indicated that the Lenfest approach is not a good fit for menhaden.  The current approach of protecting spawning potential has worked well.  There is no obvious biological or scientific reason to abandon it now.

Joseph W. Smith
Beaufort Lab, Retired

This story originally appeared on Seafoodnews.com, a subscription site. It is reprinted with permission.