New Menhaden Stock Assessment Highlights, Yet Again, the Need for Ecosystem Goals
By Ken Hinman
“We have all been here before.” – David Crosby, Déjà Vu
The just-published 2015 Atlantic menhaden stock assessment says the species is not overfished and overfishing is not occurring. Okay, we’ve heard that before. But what does it mean, really?
Well, some in the menhaden industry would have you believe it means there are plenty of fish out there; that there’s no need for catch limits now, including those put in place two years ago, and never has been. But anyone who believes that just doesn’t get it. Never has, probably never will.
The concern of anglers and environmentalists about the status of menhaden has always been about its vital role as a prey species for predators up and down the east coast. So it’s important to understand that this latest evaluation of the menhaden stock addresses only its ability to sustain harvest and avoid depletion[i], not its capacity to provide adequate forage for other species in the ecosystem. In this way it’s no different than every other assessment performed by the Atlantic States Marine Fisheries Commission since 1999, when an expert review panel recommended future assessments use a reference point “responsive to menhaden as a forage species…which maximizes population abundance.”[ii] Unfortunately, that change in the way we judge the status of Atlantic menhaden is still on the ASMFC’s “to-do” list 15 years later.
Good News, Bad News
There is some good news in the new status report, which suggests that reduced fishing pressure is having positive effects on growth in the menhaden population. The assessment reveals an increase among fish in the oldest age classes, with more large adults than in previous estimates, an increase that coincides with lower fishing mortality rates over the past decade.
We would expect this trend to continue with the conservation measures implemented in 2013.
But the assessment also confirms that abundance of menhaden – that is, total numbers of fish – remains near historic lows. It is overall abundance that is most relevant to menhaden’s ecological role, not adult biomass, since many predators, striped bass and osprey for instance, depend on large numbers of small, juvenile menhaden. Because of poor recruitment, especially in Chesapeake Bay nursery grounds, the total numbers of menhaden actually declined since the last benchmark assessment in 2010.
Stay the Course and Set Ecosystem Goals Now
The bottom line is this: Without ecosystem goals, the new menhaden single-species stock assessment leaves key questions unanswered and the industry arguing against conservation measures already on the books, measures adopted to increase menhaden abundance and availability as forage.[iii]
In our view, the 2015 assessment argues not for changing course, but for moving ahead more quickly with development of ecological reference points for Atlantic menhaden.
Here’s what the ASMFC Menhaden Management Board should do:
- Keep the existing catch limits in place. It would be folly to reverse course at the first sign of improvement, especially given lingering concerns about low abundance and recruitment. On the contrary, now is the time to hold the line and focus our full attention on long-term ecosystem goals. Making this even more imperative is the commission’s recent action to rebuild striped bass, whose health and numbers are strongly linked to availability of its preferred prey, menhaden.
- Begin an addendum to institute interim ERPs. The 2015 assessment review panel agreed with previous panels that “development of Ecological Reference Points should be a priority for Atlantic menhaden management” and agreed with the Atlantic Menhaden Technical Committee that the Menhaden Management Board needs to provide more explicit ecosystem goals and objectives in order to determine which ERPs should be adopted. The approaches for developing ERPs identified by the TC range from using highly complex and data-intensive multi-species models and empirical analyses to the use of ad hoc reference points based on well-known trophic principles as recommended by recent forage fish studies.[iv]
- The TC advises that these “forage services” reference points (i.e., F=o.75M, F=M, B75% and B40%) “could be adopted at any time using the most recent peer reviewed Atlantic menhaden model”[v] (emphasis added). The 2015 peer review panel, while favoring a multispecies approach to modeling the dynamics among menhaden and its predators, suggests this work could be done “in parallel to simpler approaches that may provide interim solutions until the multi-species model is ready.”[vi] (emphasis added)
A Simpler, Interim Approach to Protecting the Ecological Role of Menhaden
As the peer review panel’s report states, a broader ecosystems approach to conserving Atlantic menhaden demands recognition of the trade-offs associated with managing menhaden to serve directed fisheries vs. maintaining adequate forage to serve ecosystem needs (as well as the needs of other fisheries that target predator species).
Indeed, considering both sides of the equation is paramount in making sound policy decisions. But the fact is, these trade-offs are already occurring under our current regime, and until the ASMFC adopts ecosystem goals for menhaden and begins using them to inform and guide its management decisions, we are ignoring one side of the equation – that is, the impact on predators, on other fisheries and on the ecosystem.
Even if it were possible to create an accurate mathematical model of a complex marine ecosystem for fishery management purposes, and that is highly questionable,[vii] the demands on fishery managers, let alone their scientific advisors tasked with creating and feeding such a model (no pun intended), would be unbearable. It would require making innumerable decisions throughout the system about desirable targets and thresholds for interconnected species, monitoring them simultaneously, assessing cause-and-effect, and taking multiple complementary actions through numerous individual fishery management plans governed by separate management bodies.
It is a black hole from which we would likely never emerge.
The sensible thing to do is take interim action now to adopt ecological reference points based on sound trophic principles, such as those suggested in Section 2.4.1 of Appendix E of the 2015 stock assessment report. If a more empirical method should become viable sometime in the future, make the change then. But continuing to mark time with menhaden is not an option.
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[i] SEDAR. 2015. SEDAR 40 – Atlantic Menhaden Stock Assessment Report. SEDAR, North Charleston, SC. January 2015. p. 7.
[ii] ASMFC 1999. Stock Assessment Report No. 99-01 (Supplement) of the Atlantic States Marine Fisheries Commission. Atlantic Menhaden Stock Assessment Report for Peer Review. February 1999. p. X.
[iii] ASMFC 2012/2013. ASMFC Approves Atlantic Menhaden Amendment 2. Fisheries Focus. Vol. 22, Issue 8. December 2012/January 2013.
[iv] The examples of “forage services” reference points offered by the TC were in fact first recommended to the TC and Menhaden Management Board by Wild Oceans in June 2009, in a paper entitled Ecological Reference Points for Atlantic Menhaden, and were based on a review of the literature up until that time. Since then, a number of forage fish studies have affirmed a consensus around these recommendations, including Smith, Anthony D.M., et al. 2011. Impacts of Fishing Low-Trophic Level Species on Marine Ecosystems. Science. 1209395. 21 July 2011; and Pikitch, E., Boersma, P.D., Boyd, I.L., Conover, D.O., Cury, P., Essington, T., Heppell, S.S., Houde, E.D., Mangel, M., Pauly, D., Plagányi, É., Sainsbury, K., and Steneck, R.S. 2012. Little Fish, Big Impact: Managing a Crucial Link in Ocean Food Webs. Lenfest Ocean Program. Washington, DC. 108 pp.
[v] SEDAR. 2015. Appendix E. p. 30.
[vi] SEDAR 2015. Section III: Review Workshop Report. p. 23.
[vii] Pilkey 2007. Useless Arithmetic: Why Environmental Scientists Can’t Predict the Future. Orrin H. Pilkey and Linda Pilkey-Jarvis. 256 pages, Columbia University Press, New York, 2007.