. Catching Cod, or Not… Fisheries Management and the Anthropocene

Posted by on April 3, 2018
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The people of Newfoundland are a patient lot, but their patience has been further tested this month.  And that test provides me a teaching moment:  Our negative impacts on the world can be halted, but we assume too often that when they are halted, the world will recover, promptly and smoothly, to its former condition.  That is seldom the case.

Cod fishing has been the lifeblood for Newfoundland ever since Europeans began using drying racks on its shores to prepare the fish for shipment home.  Photo © JL Rotman/Corbis.

The good people of Newfoundland, when they are not busy starring in musicals about their well-recognized generosity, mostly wait patiently for the fishing to improve.  They’ve been waiting since 1992.  That’s a long time, and the wait is far from over.  The Department of Fisheries and Oceans has just released a report showing that the northern stock of Atlantic cod, Gadus morhua, listed as Vulnerable on IUCN’s Red List, has declined in numbers for the second year in a row, and remains within what DFO refers to as the critical zone – a population that is so reduced that any fishing mortality at all should be avoided.

The northern stock is the population of cod that occupies the waters off the southern third of the Labrador coast and the eastern coast of Newfoundland, extending out beyond Canada’s 200 nautical mile limit, and encompassing all of the Grand Banks.  This is an immense area that used to provide annual catches in the order of 200,000 to 400,000 tonnes of cod (nearly 800,000 tonnes in 1968 and 1969) until the stock collapsed in the early 1990s and commercial fishing was suspended in 1992.

Annual fishery landings of northern cod, 1958 to 2017 (left) and 1995 to 2017 (right).  2J, 3K, and 3L are the northern, central and southern sectors (NAFO Divisions) of the western North Atlantic occupied by this population of cod (they stretch from the central Labrador coast south to the southern boundary of the Grand Banks).  It is clear from the right-hand graph that the catch has been substantially larger in 2016 and 2017 than in recent years (although still far below the catches prior to stock collapse in 1992).  Graph © Fisheries and Oceans Canada.

DFO analyses reveal that both natural mortality rate, and mortality rate due to fishing have increased.  Natural mortality (the proportion of fish dying during the year from causes other than fishing) nearly doubled from 0.39 in 2016 to 0.74 in 2017.  That is equivalent to a change from 70% of animals alive at 1/1/2016 surviving through 31/12/2016 to just 48% of animals alive at 1/1/2017 surviving through 31/12/2017.  Fishing mortality (the proportion of fish dying due to fishing) increased from 0.014 in 2015, to 0.021 in 2016 and 0.025 in 2017.  Likely reasons for the increase in natural mortality include a falling abundance of capelin and shrimp, major food sources for cod, and temperature changes due to climate change.  (Temperature changes can directly impact the fish by altering metabolic requirements for food, and can affect them indirectly through impacts on food species.)  The increases in fishing mortality are evident in data on fish landings – these increased from 10,000 tonnes in 2016 to 13,000 tonnes in 2017, but would likely have had only a minor impact on the population compared to that of the change in natural mortality.

DFO reports that spawning stock biomass (the estimated abundance, as biomass, of spawning-age individuals) has declined from 423 kilotonnes in 2017 to 315 kilotonnes in 2018.  That is a substantial drop, and DFO expects the stock numbers to decline further in 2019, based on the lack of spawning-age individuals.  A plot of the estimated number of two-year-old fish since 1983 shows the sorry state of this population since the early 1990s.  Looks like those Newfoundlanders will be waiting a few decades more.

Graph showing decline in status of northern cod (as number of two year old fish) from 1983 to 2017.  The pronounced crash in 1989-1992 and the slow ‘recovery’ since are both clear.
Graph
© DFO Canada.

The Atlantic cod is a moderate size fish.  It can reach two meters in length, although it is now seldom seen larger than 90 cm in length.  It reaches breeding age between 5 to 7 years old at a size of about 35-50 cm length along the northern Newfoundland and Labrador coasts, but matures at the same size, at 2 to 3 years of age further south.  When they spawn, newly mature females produce 300-500,000 eggs, but a female can produce several million eggs once >75 cm in length.  The eggs are pelagic and hatch into pelagic larvae.  After two and a half months, larvae settle to the bottom and commence a juvenile life in which they are relatively sedentary in waters 10 to 150 m deep where they make use of sponges and seaweed that provide cover.  After 1 to 4 years of juvenile life they become more active and wide-ranging mid-water predators.

The Atlantic cod is not just a convenient fishery species.  It sustained the most important fishery in the Atlantic Ocean from the late 15th century until 1992 – 500 years.  That fishery began with ships journeying across from Europe for a season of fishing (or until the hold was full of fish in brine).  The fishery switched to making use of the islands and coastline of Newfoundland, as places for summer camps where fish were dried before being packed in salt for shipment back to Europe (less weight per tonne of edible product).  The colonization of Newfoundland, the Maritimes, and New England states followed; a direct consequence of the cod fishery.  This was a fishery which became a major part of a trade cycle that also moved West Indian sugar and African slaves.  The economic value of the cod fishery is hard to overestimate.  But it collapsed in 1992, and 25 years later it seems very unlikely to recover any time soon.

Why Did It Happen?

So, why did the cod stock collapse?  The first thing to recognize is that this is not an isolated occurrence.  Fisheries collapse all the time.  Well-managed fisheries (like the cod fishery) and poorly managed fisheries collapse.  Collapses can be gradual or sudden and can be devastating to the communities that depend upon them – just talk to Newfoundlanders about cod.  The collapse of the northern cod fishery is a part of a wide-spread, multi-species collapse affecting most trawl fisheries off the eastern coast of Canada and the north-eastern USA in recent decades.

It is widely thought that fisheries for long-lived, slow-growing, larger species (such as cod) are more prone to collapse.  These, the argument goes, have less capacity to rapidly recover numbers if overfished because it takes so long from hatching to reproductive maturity that the fishery is seriously depleted before anyone is aware of the problem.  However, recent studies by Malin Pinsky of Rutgers University have confirmed that short-lived, fast-growing, and smaller species are also prone to collapse.  In fact, in his first paper on this topic published in 2011 as he was completing PhD studies at Stanford University, Pinsky examined data on a globally distributed list of nearly 600 fishery stocks for which landings data or formal population assessment data existed.  Of these, about a quarter had collapsed at some point in their fishing history.  He looked at a number of species attributes: longevity, age at maturity, size, growth rate, trophic level, fecundity, egg size.  For none of these was there a significant trend in likelihood of collapse.  The only factor that did show a significant trend was fishing mortality – the proportion of the population each year that succumbs to fishing.

One interesting difference existed between the stocks for which formal assessment data were available and the stocks for which only landings data were available.  For the landings data set, there was a slight (though statistically nonsignificant) trend towards collapses being more likely in longer lived, later maturing or slower growing species.  When assessment data are available, that indicates a stock is being managed using fishery science procedures, but many fish stocks are not managed this way and those less scientifically managed stocks predominate in the landings data set (information on numbers caught each year, and perhaps on fishing effort as well).  More scientifically rigorous management should mean that catch rate is set so that fishing mortality is closely related to the capacity of that species to replenish the fish taken, and this should lessen the risk of collapse.  Less effectively managed stocks are likely to exceed appropriate levels of fishing pressure more frequently if they are slow-growing or late-maturing than if they are faster growing or earlier maturing stocks.

In a follow-up paper published in 2015, Pinsky, and his colleague, David Byler of Princeton University, reached a surprising conclusion.  They evaluated the 150+ fishery stocks worldwide for which long-term assessment data were available, using newer analytical methods that could also incorporate climate variability, along with fishery and population data.  They were able to confirm, contrary to expectations, that species with what they call ‘fast’ life cycles (shorter lived, faster growing, earlier reproducing) were more likely than others to collapse under excessive fishing pressure.  This is likely due to the greater impact on such species of changes in climate or other environmental variables – short-lived, rapidly reproducing species are more likely to track environmental change more completely than species which buffer fluctuations in environmental condition more effectively and show a dampened population response to good times or bad.  Paradoxically, good management is more effective on the ‘slow’ species than on ‘fast’ ones.  Their analysis also showed that chronic (i.e. prolonged) overfishing leads to depletion of a fishery, while higher levels of overfishing (i.e. fishing at levels well above sustainable ones) lead to collapse in the first place.

We Set Fisheries Up for Collapse

So why DID the northern cod stock crash, and why is it remaining depressed a quarter century later?  This was a ‘well-managed’ fishery, in the sense that DFO had relatively good information about the structure of the population gained through regular stock assessment and was issuing advice based on those assessments.  What stock assessments cannot evaluate, however, is the likelihood of environmental changes that may affect the capacity of the population to replenish itself (such as by altering food regimes or affecting the survivorship of larval stages, for example).  Further, there is always some slippage between fishery management advice and fishery regulations introduced and enforced.  The cod fishery was being intensively fished during the late 1980s – at, or even in slight excess of that which would be sustainable.  Changes in water temperature altered availability of food for larval and/or juvenile cod.  The cod were failing to replenish themselves, but fishing pressure remained high.  Recommendations to reduce the allowable catch were not followed at first because of the effect that would have on the industry.  Only when the pressure to do something became high enough to force a politically difficult decision, the fishing moratorium was put in place (forcing an abrupt loss of livelihood for the fishing community), but it was already too late to avoid the marked collapse.  Landings fell from 219,000 tonnes in 1990, to 154,000 tonnes in 1991 and 52,000 tonnes in 1992.  In 1995, three years after the moratorium went into effect, fewer than 1000 tonnes were landed.

Since 1992, there has been ongoing pressure from the fishing community to open up the fishery again.  Catches have been allowed to creep up, and 13,000 tonnes were landed in 2017.  While the continual, low-level fishing pressure is likely having an insignificant effect on the stock, it is still having an effect that diminishes the ability of the stock to build up numbers.  In addition, the environment in which the cod reside has continued to change; some other species have become more common and use food that otherwise would be available for cod, or prey upon cod themselves, and prey species may be less available for other environmental reasons as well.

The story of the northern cod fishery is typical of collapses.  Pinsky and Byler refer to ‘the dynamics of coupled social-ecological systems’ by which they mean the societal features that delay responses to a decline in a fishery stock.  These features include the unavoidable delays in collection of scientific data on the stock, analyses of those data and development of fishery recommendations, and eventual adjustments to fishing pressure.  When a stock is already being fished at a rate which is on the borderline of being unsustainable (and most fisheries reach this level of exploitation quite quickly), continuation of that level of fishing pressure when the population declines exacerbates the decline and can quickly lead to substantial damage to the stock.  In other words, we set fisheries up to collapse the moment we manage for maximum sustainable yield – taking the maximum amount of fish that should be sustainable given the status of that population.  And pressure by the fishing industry nearly always ensures we manage for maximum sustainable yield.  We set them up to fail, because our management systems are incapable of responding quickly enough to signs that the population has declined.  We also forget that it is normal for populations to fluctuate in size – there are good years and bad years, after all.  But when you are managing for maximum sustainable yield, it is very important to know that the population has fallen because of factors unrelated to fishing.  That is the time when catch should be reduced to compensate, yet we frequently take a different approach – well, let’s keep a watch on things, but continue fishing at the previously agreed rate.

Optimistic Views of Global Trends

The Fisheries and Agriculture Organization of the United Nations (FAO) reports every second year on the status of fisheries and aquaculture globally; the next report will be out within the next few months.  In these reports, FAO classifies global fisheries as overfished, fully fished and underfished (implying that fish species exist only for the purpose of being caught by humans!).  Over the years, despite FAO’s tendency to always take an optimistic view, the number of underfished stocks has diminished, the number of fully fished stocks has remained more or less the same, and the number of overfished stocks has grown.  The 2016 report showed about 30% of fishery stocks were now overfished, while only 10% remained underfished.

Trend in the status of globally important marine fishery stocks from 1974 to 2013 as reported by FAO.  Figure 13 in State of World Fisheries and Agriculture, 2016 © Food and Agriculture Organization of the United Nations.

Despite this long-standing trend, and flat fishery yields since the late 1980s, FAO projects a 1% increase in total capture fishery yield by 2025, due in part to the recovery of a number of overfished (=collapsed) stocks, spurred in part by the UN’s new Sustainable Development Goals (SDGs) and their specific targets which might help improve management of fisheries.  I fear this is a vain hope, but perhaps we will all rise miraculously to the UN challenge and end hunger and poverty, while conserving marine resources (the three SDGs singled out by FAO as likely to lead to stock recoveries).

In the past, fisheries that collapsed did oftentimes recover.  The important step that needed to be taken was to suspend fishing for long enough to permit the recovery to take place.  On the face of it, this is a reasonable expectation:  if we fish a population, we are increasing the mortality rate of that population, meaning that individuals live shorter lives and perhaps reproduce on fewer occasions.  If a population suffers an increase in mortality rate, with no increase in rate of production of young (or perhaps a reduction in this as well) that population will become smaller until a new balance between production and mortality is reached.  Therefore, if we stop fishing, we lower the mortality rate again, which should lead to another equilibration between production and mortality and a consequent increase in the population.  This is the way water level in a bathtub can be set by adjusting the inflow and outflow.  It is more or less the way things used to work for fisheries, although our success at stopping fishing was often less than needed, and the depleted population dwindled further, lingered at low levels, or took many years to slowly recover.

In a 2010 review, NOAA fisheries scientist, Steven Murawski, evaluated 25 well-managed commercial fisheries stocks that had collapsed to ascertain patterns of recovery.  He reported that all but one “exhibited signs of recovery”, but in several instances recovery was incomplete even after a decade or more of careful management.  One of his take-home messages was “Rebuilding the majority of stocks classified worldwide as ‘overfished’ will take a more effective, consistent, and politically supported stock-recovery paradigm, if society is eventually to meet its articulated sustainability goals for global fisheries”.  That’s a very polite way of saying we have to work much harder than we usually do to cut fishing pressure and keep it cut for a sufficient time for recovery to occur.  Newfoundland fishermen, whose patience has been tested, must understand that the testing will last a good bit longer.

Now Things May Be Different

Sadly, however, the present and future may not be like the past, and Murawski’s optimism may now be misplaced.  The example of the northern cod stock seems to show this.  A 2017 article in Nature Communications, by Gregory Britten and colleagues at Dalhousie University, points out that fishery management practice has presumed that the playing field was level, but it now appears to be strongly tilted.

Well, actually, they did not even mention playing fields!  What they did say is that fisheries management (and other types of environmental management) has always proceeded on the assumption that while environmental conditions often vary, they vary around a stationary ‘average’ condition.  Thus, the assumption goes, there are good years and bad years for fish production or survivorship and growth, but these average out over time; there are no long-term trends in environmental condition.  Britten and colleagues suggest that while it may have been appropriate through most of the 20th century, we can no longer assume this essential long-term stationarity in environmental conditions.  They suggest that there is now growing evidence that the environment is changing directionally, in many ways, and these changes have consequences for the production of fish; these changes must be taken account of when determining allowable catch for future years.  The most obvious of these long-term changes relate to climate, but here it gets complicated, because global warming does not translate simply into a uniform warming of the oceans, and warming does not translate simply into enhanced, or diminished, production in any particular fishery.  Much of their article concerns a method for making best estimates of future production for use in setting allowable catch.

  When Miami Beach is under water, it doesn’t really matter if climate change is our fault or not (but it is). Image © Joe Darrow/Florida Trends.

While I think of it, I’ve heard this argument for stationarity of environmental conditions more times than I care to remember from climate skeptics of various stripes.  Its usually offered immediately before the arguments based on sunspot cycles, or wobbles in Earth’s axis.  And it gets followed in turn by the claim, “Well, anyway, if the climate is changing its nothing to do with human actions” – as if that matters a damn when glaciers are melting at alarming rates and the world’s major cities are getting wetter and wetter every high tide.  But I digress…..

Britten and colleagues evaluated 276 well-managed global fishery stocks, and showed that 68% of them exhibited biologically significant non-stationarity in productivity.  They illustrated one consequence of managing such a population as if its intrinsic productivity was constant, using the Gulf of St. Lawrence cod stock and the eastern Atlantic stock of bluefin tuna as examples.

The cod stock (much like the northern cod stock off eastern Newfoundland) went through a series of good years (strong intrinsic production) in the 70’s and early 80’s, but then moved into a series of bad years from the mid 80’s to the present.  Managing them as if their productivity was stationary meant that there were fish available to catch that were likely not taken in the good years, but in the bad years the allowable catch was consistently set too high.  This stock collapsed along with the northern cod as revealed by the record of actual catch (as + symbols).

Two examples of consequences of managing assuming stationarity in intrinsic production are the Gulf of St. Lawrence stock of cod (a, c) and the eastern Atlantic bluefin tuna (b, d).  For both (a, b), the surplus production estimated (an index of the amount of fish available to harvest) using conventional methods is shown as a solid black line, and that estimated including non-stationarity as a dotted black line.  The calculated sustainable yields (c, d) are shown as the horizontal black line (conventional) and the irregular dotted line (non-stationary).  Differences between the two methods are shown as gray and pink shading – gray indicating an underestimate of production of sustainable catch using conventional procedures, and pink indicating an overestimate of these.
Image is Figure 2 in Britten’s article.

The bluefin tuna experienced an alternating series of several good followed by several bad years over the time period.  Each cycle lasted a decade or more.  This depressed fishery undoubtedly benefited during the period from 1985 to 2002, when allowable catch using conventional management methods underestimated the real potential catch.  The situation since 2002, however, suggests allowable catch needs to be substantially reduced because the conventional approach is seriously overestimating the numbers of fish available to catch.  Whether this cycling pattern of good production followed by poor production will continue into the future is unknown, but assuming that the stock has stationary intrinsic production capacity is clearly not warranted.

We No Longer Live in our Grandfather’s World

The tendency to expect fish populations to have stationary rates of production, growth, and (non-fishery) mortality, is just one aspect of our too-human expectation that the world is a dependable place.  It is a logical development of us having spent the last 11,500 years in the Holocene, a period remarkable for its stationarity once the melting back of the Pleistocene ice sheets had been accomplished.  After all, our entire development of agriculture and advanced civilization has taken place at a time when ‘severe’ climate fluctuations were as much as 0.5oC in extent.  (A 2013 analysis in Nature Geoscience has shown that the Medieval Warm Period, ~1000 to 1300 AD, was a time when parts of Europe were perhaps 0.5oC warmer than in the subsequent Little Ice Age, ~1400 to 1900 AD, but globally, temperatures declined perhaps 0.4oC over 2000 years before the warming of the 20th Century.  A new analysis in Nature this February has confirmed the long-term fluctuation in global temperature of only about 1oC during the last 10,000 years until the mid-20th Century warming commenced.)

That dependable Holocene world ended during the 20th Century.  Now we live on a planet that is changing in many ways, mostly driven by our activities.  Temperature is warming rapidly.  Rainfall patterns are changing dramatically.  Storms are becoming more violent.  Glaciers are melting and sea level is rising inexorably.  Oceans are acidifying and losing dissolved oxygen.  These changes have ramifying impacts on our environment, on the natural resource such as fish which we try to manage, and on our agriculture.  They also change the impacts of pest species, of disease pathogens, and the intricate relationships among species that govern ecosystem function and ecosystem resilience.

The global environmental crisis is complex, daunting and growing, but it is possible to dissect it and deal with each part step by step.  Failing to do so is a recipe for human disaster.
Image
© F. Pharand-Deschênes /Globaïa

By coincidence, while I was writing this commentary, a friend lent me a short book published by the Calgary Institute for the Humanities in 1988.  By Lydia Dotto, a Canadian science journalist and photographer now at Fleming College, Thinking the Unthinkable is a 73-page summary of a three-day conference held in 1987 at the University of Calgary.  The conference, Civilization and Rapid Climate Change, brought together 45 scientists, social scientists and humanists to discuss the threat to human life posed by overpopulation, nuclear war and rapid climate change.  While the organizers mostly had nuclear winter in mind when they decided to look at climate change, the discussion in the book reveals about an even split between concern for the environmental consequences of nuclear war, and concern for the environmental impacts of anthropogenic climate change.  Back in 1987, people were starting to think about climate change, something that would become important in “the next century”.  I found the book prescient in its ability to anticipate what was happening to our planet, strange in its clear preoccupation with nuclear conflict – a conflict that has faded mostly from view until very recently – and very chilling in two things.  These are its clear-sighted discussion of the severity of the risks we face, and its explicit link of overpopulation to the environmental changes that are coming.

The world has been talking about climate change and the environmental crisis for so long now that we have become immune to the severity of the events we are considering.  Dotto is quite clear about the likelihood of our civilization surviving the kinds of environmental changes that are on track for happening over the next half century or so – it is trivial to nil.  She is also quite clear about the importance of overpopulation, not simply population growth, and overconsumption, both of which have continued to get worse in the 30 years that have passed.  These are at the root of the environmental problems we now face, and we are not going to solve these environmental problems without also dealing with the population problems.

I feel sorry for those Newfoundland fishermen, waiting patiently for the cod to return.  Only now are they, and the managers, and the rest of us becoming aware of the fact that the northern cod stock may never recover to the levels it was at in the 1980s or earlier.  The changing environment, and the actions of other species in response during the absence of the cod, may mean that the possibility of rich cod stocks, truly overflowing abundance of a majestic fish, is something that can never be attained again.  Or then again, perhaps they will recover, and we simply have to wait patiently for far longer than we ever imagined that we would.  But I am also sorry for all of us, because we seem so slow to learn the lessons that the natural world is putting up in front of us, lessons that should be easy to learn, if only we’d pause, and think, and absorb.  We cannot continue behaving the way we do, and expect that the natural world, ever forgiving, will let us make error after error, will tolerate our overconsumption and our trashing pollution.  The planet has a certain capacity to absorb the slights we throw; we have been exceeding that capacity for some time now, and do not seem to be mending our ways nearly fast enough.  Unless we change dramatically and soon, our future will be dire indeed, and cod stocks will be the least of our worries.

Gadus morhua, the Atlantic cod, photographed at Atlanterhavsparken, Ålesund, Norway.
Image
© H-P Fjeld.

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