What is a sustainable fishery?

It seems that nobody has the answer.  At least not an answer that is widely supported by environmentalists, fisheries managers, fisheries scientists, third party certifiers and the fishing industry.

A clear, succinct and widely adopted definition of a sustainable fishery would provide a benchmark against which individual fisheries could be compared.  It would cut down on the wiggle room jargon of “conditionally sustainable”, “on the road to being sustainable” and “more sustainable than it was”.  Simply put, a fishery would be deemed currently either “sustainable” or “not sustainable” based on a few carefully chosen and measurable conditions.

Currently MSC requires 23 criteria to be addressed under three principles in order to determine whether or not a fishery is sustainable.  Each of these criteria has one or more sub-criteria, each with an associated performance indicator that has to be scored and added together to determine a pass or fail.   It is a complex system which allows depleted fisheries, data poor fisheries and fisheries with collateral environmental damage to be certified conditionally sustainable provided a plan is proposed to ameliorate these flaws.  This leaves the public confused and environmental groups shaking their heads.  

Unfortunately scientific experts do not agree on a definition of a sustainable fishery. 

In the “Comments” section of the Washing Post related to the article “Some question whether sustainable seafood delivers on its promise” (by Juliet Eilperin, Published: April 22 2012),  Ray Hilborn of the University of Washington draws the distinction between sustainability as a state of a stock, and sustainability as a process. He believes that “sustainability is clearly the result of a process, stocks can be overfished, by anyone's definition, and still be sustainable if the management system responds to changes in abundance and reduces fishing pressure allowing stocks to rebuild”.

The notion, that a fishery on a stock in a depleted state can be considered “sustainable” provided there is a management process in place to reduce fishing pressure and allow the stock to rebuild in the future, is highly controversial.

In contrast, many would argue that a sustainable fishery is one in which overfishing is not taking place and the stock is not overfished at the present time.  In other words the “process” should have already led to the stock being rebuilt before the fishery on that stock can be termed “sustainable”.

Translated into fisheries science jargon, a sustainable fishery is one in which fishing mortality is on average below Fmsy (no overfishing) and spawning biomass is on average above Bmsy (not overfished) at the present time. 

Here Fmsy is the fishing mortality that gives maximum sustainable yield on average and Bmsy is the average spawning stock biomass that results from fishing at Fmsy.  

Secondary but important considerations include a societally acceptable low level of collateral  damage through ecosystem alteration, bycatch impacts and habitat destruction.  

Is sustainable seafood really sustainable?

A recently published paper in the journal Marine Policy by German scientists Rainer Froese and Alexander Proelss has attracted the attention of the Washington Post and other media. 

The paper takes issue with sustainability certifications of marine fisheries by the Marine Stewardship Council and the Friends of the Sea.

 

They examined the most recent estimates of current biomass, (B) biomass at maximum sustainable yield (Bmsy), current fishing mortality (F) and fishing mortality at MSY (Fmsy) from national or international fisheries bodies and published papers for 71 MSC certified stocks for which they could find such information.

 

For 11% of these stocks the information was insufficient to make a judgement about stock status or exploitation levels.  31% of the stocks with sufficient information were overfished and were currently subject to overfishing.

 

They define “overfished” as those stocks where B is less than Bmsy and "overfishing" as taking place when F exceeds Fmsy.  They allow some latitude in that if the ratio B/Bmsy is  greater than 0.9 or F/Fmsy is less than1.1 it is not included in the percentage total of overfished and overfishing.

National fisheries agencies and international fisheries organizations tend to be somewhat coy regarding their specific definition of sustainability with respect to marine fisheries.
  

The US, under the Magnuson–Stevens Act, is an exception in this regard although the criteria may vary somewhat on a stock by stock basis.  Commonly the US definition of “overfishing” is the same as that adopted by Froese and Proelss (F>Fmsy) but the US tends to be more tolerant with regard to the definition of overfished, commonly requiring the stock to  be above 50% of Bmsy or 50% of maximum spawner potential (spawner per recruit).

Under Principle 1 of their standard, MSC ideally requires that fisheries are managed so that they fluctuate around Bmsy or higher although stocks can still be certified under this criterion if they are above 50%Bmsy.  Of course there are many MSC loopholes around this that allow fisheries to be certified even where there are no reliable estimates of where the stock is relative to these levels.  Fmsy does not factor directly into the MSC certification standard, so that it is feasible that fisheries in which overfishing is taking place, such that the stock will be depleted over time, can still be certified as sustainable.

While Froese and Proelss may raise the bar a little too high, stocks that are consistently below Bmsy or are being fished consistently above Fmsy should not be given sustainable fishery labels.  Also, data poor fisheries cannot be assumed to be sustainably managed based on vague and subjective notions.  The fact that overfished stocks subject to overfishing, as well as data-poor stocks, are being certified as “sustainable” brings into question current standards.

National fishery agencies and international organizations would serve us well by developing clear globally accepted and simply applied standards for what constitutes a sustainable fishery. Fisheries that are shown to meet such standards through scientific peer review of assessment of stock status would not be in need of further sustainability accreditation.