Plenty of Fish in the Sea?

Stephen Hall -

Investment in sustainable aquaculture essential, floating cages in the Philippines. Photo credit Wilfredo Yap

How many of us have been told at some point in our lives “don’t worry…there’s plenty more fish in the sea”?

This old proverb might comfort us for disappointment in love, but taken in its most literal sense, few people seem to believe it.

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Scan the popular literature and it is easy to find articles with headings such as “imminent declines in fish stocks”, “collapse in world fisheries”, “current fisheries unsustainable”. Many of these articles are based on research findings and conclusions that support this view.

But how true is this picture? Is the scientific community aligned in its pessimism? Or is there a credible body of researchers who draw from the available data more optimistic conclusions about the current state of the oceans and the direction in which it’s heading?

To answer this question, let’s start with the official statistics from the FAO. Providing the most authoritative assessments of the status of world fisheries, the FAO collates information on about 445 fish stocks every two years. Using regional experts and data submitted by member countries these assessments account for about 80% of FAO estimated global catch.

Using these data, the proportion of stocks that are deemed over-exploited or beyond provides a useful indicator of world fisheries status. The most recent FAO estimate is that in 2008 32% of stocks were either over-exploited, depleted, or recovering but still at low levels (1). This is hardly a promising picture, but for most people I suspect 32% falls short of the tragic level of depletion one might imagine from popular news stories.

But does everyone agree with the FAO estimate? Well at first sight the answer would seem to be “pretty much”; most of the recent published analyses arrive at a figure of around 30% (2-4). Dig a little deeper though and this apparent consistency is complicated by two factors.

First, definitions of over-exploitation differ. FAO, for example, define a stock as over-exploited when stock biomass falls below what fisheries scientists estimate is needed for Maximum Sustainable Yield (MSY) – the long-term surplus fish production that we can take as catch. Other studies (3, 4) define over-exploited as less than half of the biomass that produces MSY – a more conservative figure. Still more uncertainty arises because some estimates are derived from approaches (e.g.2) that cannot be readily compared with others.

Second, data for some places are absent or shaky. In many developing countries and in particular, South, South East and East Asia, which are significant sea fishing regions, the data to assess stock status have either not been collected or have yet to be adequately analyzed and included in global syntheses. We have little feel for how these stocks compare with the rest; anecdotal reports imply that many are over-exploited, but that is a long way from formal analysis.

So, plenty of fish in the sea? Well, notwithstanding the uncertainties, it seems that a figure of about one third of the world’s stocks below levels needed for maintaining sustainable fish catches is about right. We need to do something about these. Add to this the other 50% or so of stocks that are fully- exploited and it is clear that we are operating at or near the limits of what the ocean can provide.

And fishing at these levels inevitably means that fish numbers are lower than they used to be. If we want to take fish from the sea at about the maximum sustainable level – the goal that most societies seem to accept – for most species, the biomass of fish we need to leave in the sea to breed and provide next years catch is between 30 and 40% of the amount that would be present if there were no fishing.

On the other hand, it is also important to realize that, even when authorities class a fish population as over-fished, or even collapsed, it doesn’t mean there is a risk of wiping the population out. The Norwegian coastal cod fishery remains closed because it is deemed collapsed, yet the stock is still estimated to comprise tens of millions of individual fish (4).

But it’s all very well talking about our current situation. The much deeper question is where are we heading, given what we believe is the current status of fisheries and the imperative to meet the worlds growing need and demand for fish? If we keep going as we are will all the fish be gone by 2048 as was claimed in 2006 (5) or are we getting our act together and improving matters (3, 6)? Here there is considerable disagreement (7, 8).

The fracture line of opinion seems to turn on whether researchers base their conclusions on analyses using reported fish catches (7) or whether they believe using such data are misleading and that only data from proper fish stock assessments and surveys will do (4, 8). Using catch data researchers conclude that over-exploitation is increasing. Using assessment and survey data it looks like the proportion of over-exploited or collapsed stocks has stayed about the same over the past 40 years (4).

Yet, while this issue remains a topic of hot debate, the plain truth is that for all practical purposes it doesn’t matter whether fish stocks are, in the aggregate, declining or not. The global fishery might not be the terminally ill patient many imagine, but that doesn’t mean it doesn’t need treatment for a chronic condition. That treatment will require governments and international development agencies to increase investments to secure its future. Failure to do so and maintain productive, long-term sustainable fisheries will have profound economic and food security consequences that even the fastest growing aquaculture industry cannot compensate for (9, 10).

Unfortunately, there are no magic recipes for making those investments. It will require a continuing case by case focus on a broad range of fisheries management tools like catch and effort limitation and time and area closures. But it also requires renewed investment in reforms of fisheries governance in many places; reforms founded upon effective stakeholder dialogue about the goals of each fishery and that devolve responsibility for management and decision making to levels where incentives for fisheries to meet these broader societal objectives are highest. Solving the problems for many small scale fisheries will also require a focus outside of the fishing sector to improve more fundamental welfare capabilities and opportunities that currently confound reform efforts (11).

Perhaps surprisingly, I confess to a cautious optimism for the future. We have success stories that show that maintaining healthy viable fisheries is possible (12) and that conditions are improving in some regions (13). And new stakeholder fora, like the upcoming Economist’s World Ocean Summit in Singapore, are talking about solutions. These are encouraging signs; we must continue to build upon them to sustain world fisheries and their contribution to the millions who depend on them.


1.   FAO (2010) The state of world fisheries and aquaculture 2010 (FAO, Rome, Italy).
2.   Sea Around Us Project (2012) Stock Status in the Global Ocean.

3.   Worm B, Hilborn R, Baum JK, Branch TA, Collie JS, Costello C, Fogarty MJ, Fulton EA, Hutchings JA, Jennings S (2009) Rebuilding global fisheries. Science 325:578-585.

4.   Branch TA, Jensen OP, D. R, Ye Y, Hilborn R (2011) Contrasting global trends in marine fishery status obtained from catches and from stock assessments. Conservation Biology

5.   Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, Halpern BS, Jackson JBC, Lotze HK, Micheli F, Palumbi SR et al. (2006) Impacts of Biodiversity Loss on Ocean Ecosystem Services. Science 314:787–790.

6.   Karieva P Why Do We Keep Hearing Global Fisheries Are Collapsing? Cool Green Science.

7.   Pauly D, Froese R (2012) Comments on FAO’s State of Fisheries and Aquaculture, or ‚ SOFIA 2010. Marine Policy 36:746–752.

8.   Hilborn R (2007) Moving to sustainability by learning from successful fisheries. AMBIO: A Journal of the Human Environment 36:296–303.

9.   Dyck AJ, Sumaila UR (2010) Economic impact of ocean fish populations in the global fishery. Journal of Bioeconomics 1–17.

10.  Allison EH (2011) Aquaculture, fisheries, poverty and food security. WorldFish Working Paper 2011-65:60pp.

11.  Allison EH, Ratner BD, Åsgård B, Willmann R, Pomeroy R, Kurien J (2011) Rights‚ based fisheries governance: from fishing rights to human rights. Fish and Fisheries 13:14–29.

12.  Cunningham S, Bostock T (2006) Successful fisheries management: issues, case studies and perspectives Eburon Publishers, Delft

13.  Murawski S, Methot R, Tromble G (2007) Biodiversity loss in the ocean: how bad is it? Science 316:1281.

Stephen Hall

Stephen Hall

Stephen Hall is the Director General at WorldFish, an international research organization headquartered in Malaysia focused on reducing poverty and hunger in developing countries through fisheries and aquaculture. His previous leadership roles include CEO of the Australian Institute of Marine Science (AIMS) and Professor of Marine Biology at Flinders University, Australia. Stephen has served on several international advisory panels and, in 2010, was a member of a global team overseeing the reform of the Consultative Group for International Agricultural Research (CGIAR). Recognized as a leading scientist in his field, he has contributed more than 80 scientific publications on fisheries ecology and environmental issues as well as a highly cited book on the environmental effects of fishing. In 2004, Stephen was awarded a Pew Fellowship in Marine Conservation and he continues to investigate and write on the roles and potential of fisheries and aquaculture for supporting international development objectives. In 2005, he was awarded the Australian Public Service Medal for leadership of AIMS. Stephen holds a Ph.D. in Marine Ecology from St. Andrews University and a B.S. in Marine Biology and Biochemistry from University of Wales, Bangor.

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