Sustainable Seafood, Chapter 3. What is Sustainability?
When choosing seafood, one of the criteria we should consider is sustainability. As informed consumers, we want to support those fisheries that are sustainable, and to avoid buying fish produced by non-sustainable activities. But what does it mean to be sustainable? And how can we know if a fishery is sustainable?
What is Meant by Sustainability?
The first question we have to ask is what do we want to be Sustainable? A fishery? A species of fish? A population? An ecosystem? An economy? Can we maximize multiple goals? Ideally, we’d like to achieve all of those, but we need to be more specific. Different people have tried to define sustainability in reference to natural resources. Some of these definitions are [with my comments in brackets]:
As much harvest as possible over the long term [By whom? Does this include predators?]
“..management such that future generations may profit from these resources in the same manner we profit today.” [but not more? or less?] (Ehrhardt, 2005)
“.. a trajectory with certain bounds, rather than certain states...” (Fuentes, 1993)
The problem with all of these is that they are primarily concerned with what humans can extract from a given resource. A better description was supplied by Charles Fowler (1999). He defined sustainability as
“The persistence and endurance of systems along with that of their component elements, processes and interrelationships”
Charles Fowler was a marine mammal scientist with the NOAA Alaska Fisheries Science Center in Seattle, who undertook the task of trying to define sustainability. He used a systems approach, in which the goal is to sustain an entire system. In this context, a fishery is a system comprised of fish, their environment, their predators, their prey, as well as the humans who catch them. It is not enough simply to sustain a population of one species (say, Alaska Pollock). We also have to sustain their prey (smaller fish), their predators (about 20 species including sea lions), and the environment they live in. That can’t be done simply by counting the fish that are caught.
Fowler defined nine tenets of sustainability. I won’t try to explain them all, but two are critical. These are #3) All components of a system must stay within their respective normal ranges of variation, and #9) Management must involve humans and their role as components of the system. This means we need to know about the limits of natural fluctuations in the system, and we need to act as if we are part of it, rather than acting outside of it.
As one example, Fowler (1999) summarized the biomass of a group of four North Atlantic fish consumed by 16 species of predators, including mammals, fish, and birds. When expressed as the log10 of biomass consumed, the number or proportion of predators consuming a specific amount looks like a normal distribution. Some predators consumed more, some less, but on average, any single predator consumed about 6% (1/16th) of the total predation removal. In contrast, humans caught more than the greatest predator (spiny dogfish, which consumed almost 50%), or equal to about 70% of all predation. That is clearly not sustainable because it violates both Tenet #3 and #9. In order to act sustainably, we would need to behave similarly to other actors within the system, and not consume more than our share (about 6%).
The National Oceanic and Atmospheric Administration (NOAA) has incorporated sustainability into science-based fishery management plans. By law, U.S. seafood must be caught according to fishery management plans that:
Consider social and economic outcomes for fishing communities.
Prevent overfishing.
Rebuild depleted stocks.
Minimize bycatch and interactions with protected species.
Identify and conserve essential fish habitat.
Specific goals of NOAA to achieve sustainability are:
Avoid overfishing
Reduce Climate impacts and carbon footprints
Improve traceability through the supply chain
Limit bycatch and discards
Limit use of wild fish as feed
Control disease and pollution
Preserve habitats
Protect Human rights – safe conditions
Stop/prevent Illegal, unreported, and unregulated (IUU) fishing
Employ science-based management and enforcement
What Seafood is Sustainable?
As consumers, how should we know if our seafood is sustainable? Fortunately, there are a number of organizations that are doing that work for us.
Seafood Watch (SFW) was launched in 1999 by the Monterey Bay Aquarium, as an outgrowth of one of their most popular exhibits. Their website provides detailed information on the sustainability of most types of seafood.
SFW Defines sustainability as practices that minimize harmful environmental impacts, assure good and fair working conditions, and support livelihoods and economic benefits throughout the entire supply chain. Their analysis of various seafoods is divided into sections based on the location of the catch and the type of gear used. Most fisheries around the world are covered, including geographic and species subunits. Their conclusions are based on multiple Criteria, including impacts of the fishery on the target species, the ecosystem, the habitat, and the management capacity. Each aspect of the fishery is scored on a scale from 1 to 5 (low to high), and an average score is given. The fishery is then labeled as Best Choice, Certified, Good Alternative or Avoid.
I find the SFW website to be extremely user-friendly, transparent, and easy to navigate. Their investigations are conducted independently and are not requested by individuals or organizations associated with the source fishery. As such, I believe they provide the best advice about sustainability of the seafoods we eat.
Another source of sustainability information is the Marine Stewardship Council (MSC), which is based in England. The MSC operates a Fisheries Certification Program using three standards. These are:
Sustainability of the stock. Is the stock healthy, and is there enough biological information to understand its population dynamics?
Ecosystem impacts. What is the impact of fishing on the target species or its ecosystem. Is there a problem with bycatch or discards?
Effective management. Is the fishery managed in a way that includes fisher participation, eliminates bycatch, and reduces Illegal, Unregulated, or Unreported (IUU) fishing?
Fisheries that meet all three criteria may be awarded a certified MSC Blue Fish label. Look for this next time you shop for seafood. Funding for the MSC comes from charitable donations, and from a licensing fee paid by producers and retailers who choose to display the blue fish label on MSC certified seafoods. Unlike SFW, the MSC does not make its own evaluations, but relies on third-party experts to provide. Instead of a numerical rating, the MSC produces a certification which provides “assurance that the seafood product is verified to be sustainable/responsible, is harvested legally, and is traceable back to a sustainable source”.
The MSC has defined five different seafood certification levels:
Certified: Valid MSC Certificate.
In Assessment: Undergoing assessment
Suspended: Certification invalid
Withdrawn: Application withdrawn by requester
Not certified: Did not meet standards
Unlike the SFW, the MSC produces reports about a fishery only on request by participants in the fishery or production process. As such, only selected fisheries are investigated, and the list is not as comprehensive as that of SFW. Nonetheless, each report includes extensive review by subject experts. As a test, I downloaded and read the review on Dungeness Crab, which was 119 pages long. It referenced all four publications on that species that I published from my PhD Dissertation, so I’m satisfied that it was a thorough vetting. There are situations, though where conclusions of the SFW and MSC do not match and may conflict with each other. Personally, I find the website less user-friendly than that of SFW, and somewhat difficult to navigate. But I recommend using both of them and making your own decision.
The MSC only evaluates seafood from wild capture fisheries. Seafood produced by aquaculture is evaluated by the Aquaculture Stewardship Council (ASC). They operate much like the MSC, in terms of funding and certification, and certified seafood products can display their aqua-colored fish logo.
So, next time you decide to go shopping for seafood, spend some time perusing the SFW, MSC, or ASC websites, and learning about the items you are interested in buying. Then, in the store, look for the blue fish with the MSC Logo, or the aqua fish logo of ASC. By using these tools, you can be assured that the seafood you purchase meets the highest standards of sustainability, traceability, and accountability.
BOFFFFs and Balance
Before we leave the topic of sustainability, I wish to introduce two more concepts. The first is that of BOFFFFs, a.k.a. Big Old Fat Fecund Female Fish. In most populations of fish (and other seafoods), the largest, oldest females are the most productive part of the population. They are the most important for reproduction because they produce a disproportionately larger proportion of total eggs, although they are the least productive in terms of annual biomass additions. Unfortunately, most fisheries were developed on the premise of trying to catch the largest fish, which are, inevitably, BOFFFFs. This was based on the idea that we should not catch juveniles or small fish, but should allow them to grow as much as possible and contribute to population reproduction before being captured.
If fish egg production was proportional to body mass, we would expect that a single 2-kg fish would produce as much reproductive products as two 1-kg fish. Or that fifteen 2-kg fish (total 30 kg) would produce as much as one 30-kg fish. Here are talking about the total mass of eggs produced rather than the numbers, because egg size also varies with fish size. This would be true if reproductive output scaled isometrically with mass, i.e. was equal to some proportion (fraction) of body mass raised to the power of 1. However, a recent study by Barneche et al. (2018) demonstrated that this is not the case. For many fish, egg production scales hyperallometrically. That is, egg biomass equals some proportion of body mass raised to the power 1.33. This means that the reproductive output of one 10-kg female fish equals the output of 21 1-kg fish. Or that one 30-kg fish produces the equivalent of 37 2-kg fish.
It seems to make sense then, that we should not target the BOFFFFs nor remove those fish from the population. Rather, we should catch smaller fish, that do not have such a big impact on reproduction. Most fisheries are managed using minimum size limits (MSL) to prevent catching the smallest fish. If we want to avoid catching both the smallest and largest, we might need to employ a slot limit. This includes both a minimum and a maximum size limit. In fact, some fisheries are managed this way, such as striped bass (Morone saxatilis).
The other concept I wish to introduce is that of balanced harvest. Currently, most fisheries are managed using selective harvest. That is, we select a specific subset of the fish that we want to harvest. This is often done using 3-S or 6-S management. The former implies that we set restrictions on the Species, Sex, and Size for harvesting; adding Season, Stock, and Space (geographic subunits) brings it to 6-S. This results in harvesting a narrow selection of fish, usually the largest, fastest growing, and most valuable for reproduction. And it may have unforeseen impacts; by removing those fish from the gene pool, we are forcing natural selection to favore fish that have reduced size, reproduction, production, and growth rates. And we eliminate diversity of genetic traits from the population.
The alternative to this is to apply Balanced Harvest, as described by Zhou et al. (2010). Think of this as a way to improve, or diversify, the catch. If we are investing our retirement funds, we would not want them all invested in one stock, but would want to diversify them across a wide spectrum of stocks, using a mutual fund or some other instrument. With Balanced Harvest, we aim to diversify selection of fish across a wider variety of S’s, whether this is size, season, space, or whatever. If we caught fish of many different sizes, it would help maintain genetic diversity in size and growth rates, eliminate bycatch, and mimic natural predation.
This concept was proven in a landmark study by Conover and Munch (2002). They raised silversides (small anchovy-like fish) in tanks, then selectively removed 90% of the fish in three ways: a) the Largest fish were Harvested (Large Harvest = LH), b) the smallest fish (SH), or c) randomly harvested (RH) fish. The survivors in each tank reproduced each year, and were also harvested the same way. By the third generation, the average size of fish in the large-harvest tank was significantly smaller, those in the small-harvest tank were larger, and those in the random-harvest tank did not change size. Clearly, selective harvest of fish had an evolutionary impact on those fish within a short time period.
The four studies I have cited were required reading for students in my Fisheries Management classes. These concepts of sustainability, BOFFFFs, Balanced Harvest, and the evolutionary impacts of harvesting are understood by many scientists but are only slowly being incorporated into fisheries management. If we want to have truly sustainable fisheries, we need to ensure that management agencies consider them. But as consumers, we can have a more direct impact by choosing seafood that is managed sustainably using these concepts.
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Sources for this Post:
Diego R. Barneche et al. 2018. Fish reproductive-energy output increases disproportionately with body size. Science 360: 642-645. DOI:10.1126/science.aao6868
D. O. Conover, & S. B. Munch. 2002. Sustaining Fisheries Yields Over Evolutionary Time Scales. Science 297(5578):94-96. DOI:10.1126/science.1074085
C. W. Fowler, Management of multi-species fisheries: from overfishing to sustainability, ICES Journal of Marine Science, 56(6):927-932. https://doi.org/10.1006/jmsc.1999.0535
Zhou, S., and coauthors. 2010. Ecosystem-based fisheries management requires a change to the selective fishing philosophy. PNAS (Proceedings of the National Academy of Science) 107(21):9485-9489. https://doi.org/10.1073/pnas.0912771107
