Fisheries controversy Flashcards
Just 100 cod left in the north sea
Fake news and misleading
“None of the catches recorded at North Sea ports around Europe [in 2011] showed any fish aged 13 or over. Analysis of that data suggests there are fewer than 100 such fish in the whole North Sea.”
–Chris Darby, Cefas
But…
North Sea fish begin to mature from about 1, most mature at 3-4, and are all mature by age 6
Fewer than 60 cod aged >13y have been recorded in the North Sea over the last 30y
Saying “Only 100 adult cod…” is like saying “Only 12,000 adults in the UK” based on the number of people >100y
In reality…
The Cefas report found 21 million adult cod
Estimates of total numbers (including immature cod) in the North Sea are ~0.5Bn
“‘Just 100 cod left in the North Sea’?… Wrong by about half a billion, then… perhaps a new record for the most inaccurate headline ever covered by More or Less”
–BBC More or Less, http://www.bbc.co.uk/news/magazine-19755695
Lessons 1
Simplifying and exaggerating conservation messages is tempting
But parroting nonsense loses credibility with important stakeholders
Politics may be ‘post truth’; nature is not
“For a successful technology (conservation strategy), reality must take precedence over public relations, for Nature cannot be fooled”
–Richard Feynman
What proportion of the world’s fish stocks are overfished?
“More than 85 percent of the world’s fisheries have been pushed to or beyond their biological limits and are in need of strict management plans to restore them.”
–WWF, http://www.worldwildlife.org/threats/overfishing
“using scientific data the estimated proportion of stocks to be overexploited is about 30%”
CFOOD
“Of all the stocks assessed in 2013, 58.1 percent were fully fished and 10.5 percent underfished… the number of stocks fished at unsustainable levels [was] 31.4 percent in 2013”
–FAO The State of World Fisheries and Aquaculture 2016, http://www.fao.org/3/a-i5555e.pdf
Lessons 2
Conservation feels like an uphill struggle Attention-grabbing headlines are tempting Misleading with numbers loses respect Can result in conflicts
But might it be effective? Could this justify the approach?
“In unfished areas we can expect
ecosystems to be in some sort of balance, often with relatively high abundances of predatory fish. Initially, fisheries may target the larger, predatory, and often higher-priced species. Gradually the fishing pressure will make the larger species more scarce, and fishing will move towards the smaller species.”
–Christensen (1996) Managing fisheries involving predator and prey species. Rev Fish Biol Fisheries 6: 417-442
Mean Trophic Level (MTL) of global fisheries landings “appear to have declined in recent decades at a rate of about 0.1 per decade”.
Pauly D et al. (1998) Fishing down marine food webs. Science 279:860-863
Fishing Down the Foodweb
Stands to reason, doesn’t it?
We eat the big, tasty, valuable fish first Big fish are high trophic level
All we’re left with is low trophic level forage fish, jellies, etc.
“…if we don’t manage this resource, we will be left with a diet of jellyfish and plankton stew”
–Pauly & Watson (2003) Scientific American, July 2003: 43-47
“The affect heuristic is an instance of substitution, in which the answer to an easy question (How do I feel about it?) serves as an answer to a much harder question (What do I think about it?).”
–Daniel Kahneman, Thinking, Fast and Slow
“The moment one has offered an original explanation for a phenomenon which seems satisfactory, that moment affection for their intellectual child springs into existence… The mind lingers with pleasure upon the facts that fall happily into the embrace of the theory, and feels a natural coldness toward those that seem refractory…
The search for facts, the observation of phenomena and their interpretation, are all dominated by affection for the favored theory until it appears to its author or its advocate to have been overwhelmingly established. The theory then rapidly rises to the ruling position.”
–Chamberlin, TC (1965) The method of multiple working hypotheses (reprinted from 1890) Science 148: 754-759
Publishing bias. Not finding an effect means you’re less likely to be published.
Studies use methods which exclude key species and some areas and some years to fit their bias.
Counter Evidence
Price and Trophic Level are not correlated
Sethi SA, Branch TA, Watson R (2010) Fishery development patterns are driven by profit but not trophic level. PNAS 107:12163-12167
Fishing Through: serial addition of low trophic level species while catches of top predators remain high
21/48 ecosystems
Essington TE et al. (2006) Fishing through marine food webs. PNAS 103:3171-3175
Observed: catches increasing at all TLs
‘Fishing Down the Food Web’ is an appealing idea, but probably not a general phenomenon
“The overarching explanation is fishing for profits: high value, easy to access species will be targeted and depleted first”
–Trevor A. Branch
Conclusions
Social media encourage simple soundbites, agreeable for our brains
But conservation and ecology is complicated
These tensions lead to conflict
Action
Think critically
Recognise your biases and challenge them
Recognise the power and limitations of data
Action
Support those trying to separate truth from lies:
More generally, FullFact https://fullfact.org
In fisheries, Sustainable Fisheries UW http://sustainablefisheries-uw.org
More entertaining, BBC More or Less, http://www.bbc.co.uk/programmes/b006qshd
