Plenty of Fish in the Sea?

Posted by Stephen Hall on 3 February 2012
Fishing boats trawl the open ocean

Fishing trawler in the open ocean. Photo credit Jon Anderson

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.

School of anchovies and sardines

School of anchovies and sardines. Photo credit Nugun

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).

Floating cages in the Philippines

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

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.

  • Michel Mcpharlane

    Precisely what I was looking for, regards for putting up.

  • Julian Cribb, author, The Coming Famine (UCP 2010)

    The issue which is not raised in your article, Stephen is that, by the 2060s, world demand for food will double, and world demand for seafood is likely to grow at even faster rates, for several reasons. So is there an extra 100 million tonnes of catchable fish in the sea to accomodate this increase in demand?
    Current growth in aquaculture, while spectacular, appears to be barely keeping pace with the decline in the wild harvest – which FAO says peaked in 2004. Also aquaculture is constrained by suitable sites, water quality, disease issues and feed sources. So what is the big picture answer? While appreciating your wish to be cautiously optimistic (and as a scientist that is perfectly right and understandable), please share with us the basis for your optimism in subsequent podcasts.

    • Stephen Hall

      You are absolutely right Julian. The global demand for fish will increase substantially, driven by a combination of population growth, and increasing wealth and urbanization. And while I’m cautiously optimistic that we can improve fisheries management to secure and perhaps increase to a moderate degree their contribution to global fish supply, the plain truth is that, no matter how well we manage them, they will be unable fully meet our growing need.

      And aquaculture? Well, so far, farmed fish production has in fact more than compensated for declines in wild catches. Per capita supply from the wild that is eaten directly by humans fell from around 11kg per person per year in 1995 to around 9kg in 2009. During the same period the amount supplied by aquaculture rose from 4kg to 8kg. In consequence total per capita fish supply has risen by about 2kg. Will aquaculture be able to grow sufficiently in future to maintain or increase per capita supply? That’s a big question that I promise to address in future posts. Regards Steve

  • Dr. Azad, I.S.

    Dear Stephen,
    I was attracted by the FB link and your article title,,, Infact I had also my own doubts as to how reliable is the data that comes from diverse environemnts, different countires, geographical location with even more highly varibale system of data collection. In many places, I read the data from xyz country is not reliable…!!!. I appreciate the thinking that went inot your analysis but I am disappointed (may be you have lots of information not given here to support your views) that I didnt find the analaysis of the data obatined over years and I was particularly interested to know the present status of fishery or stocks which probably were shown fast declining a decade ago… etc. I and all those interested in the Aquatic environemnt and the sustainability of life in the ocean would be happy to read those inretesting aspects if you have any.
    None the less very thought provoking article. Thanks for sharing.

    • Steve Hall

      Thank you for your comments Dr Azad. Several of the references in the list provided contain the sort of analyses I think you are looking for. Regards Steve


    dear sir,
    it is true that decline in fish stock is going on.some species is going to be stake holder should sit together for stringent law.
    Assistant Fisheries Officer (Marine),Puri,Odisha(India)