I’ve had an interesting discussion over at the new blog of Jennifer Marohasy, who runs the environment unit at the Institute of Public Affairs. Marohasy has criticised virtually all the main scientific groups working on the Murray-Darling Basin, and in this post, she nominates The NSW Rivers Survey by the CRC for Freshwater Ecology and NSW Fisheries. as the “worst ever”. She says
The report’s principal conclusions include that “A telling indication of the condition of rivers in the Murray region was the fact that, despite intensive fishing with the most efficient types of sampling gear for a total of 220 person-days over a two-year period in 20 randomly chosen Murray-region sites, not a single Murray cod or freshwater catfish was caught.”
Most remarkably at the same time, in the same years and regions, that the scientists were undertaking their now much-quoted survey that found no Murray cod, commercial fishermen harvested 26 tonnes of Murray cod!
Criticism of the report’s findings from a local fisherman goes something along the lines “The scientists, although having letters behind their name, spending some $2million on gear, and 2 years trying, evidently still can’t fish.”
Zing! Those egghead scientists are conclusively nailed! Well, not quite.
Going to the sentence cited by Marohasy, we find that it doesn’t end where she stops the quote. The actual sentence reads (emphasis added)
A telling indication of the condition 
of rivers in the Murray region was the fact that, despite intensive fishing with the most efficient types of sampling gear for a total of 220 person-days over a two-year period in 20 randomly chosen Murray-region sites, not a single Murray cod or freshwater catfish was caught, although more than 50 of each species were found at Darling-region sites.
It looks like the scientists can catch fish after all.
Still, you might say, it was naughty of them to imply that there were no Murray cod left in the river. Except that they didn’t. Immediately following the sentence cited by Marohasy, the report goes on
While it is well known that Murray cod do remain in some parts of the Murray region which were not sampled in the Rivers Survey, and even continue to support fisheries in some areas, the results emphasise that the populations of this keystone species are now fragmented and patchy, and their overall abundance is worryingly low. Relatively high catches of Murray cod are taken by anglers and commercial fishers targeting remnant populations in some key Murray-region habitats, but these fishery catches clearly do not reflect the true condition of the population overall.
After a bit of back and forth, Marohasy backed away from the suggestion that there were plenty of cod in the sites sampled by the study and said
One of the main reason the scientist caught no fish is that they broke some of the basic rules of samplying animal populations; the rules you used to learn in 101 Zoology including do not assumed a random distribution.
Except that as we’ve already seen, it’s not true that the scientists didn’t catch any fish. They caught other species, but no Murray cod, in the Murray sites.
If the survey had been designed specifically to look for Murray cod, Marohasy’s point would have some validity, though it’s expressed rather sloppily: to put it more precisely, the most efficient estimate in situations of this kind is obtained by stratified sampling, which usually implies focusing on sites where mean abundance is high, since mean and variance usually rise together. But this was a general survey of all species, so the sampling procedure used here was entirely sensible.
While we’re on the subject of 101-level errors, Marohasy commits a big one herself, in her IPA paper on which the post is based. Most studies have taken the collapse in the commercial catch, illustrated below (source), as evidence that cod numbers have declined.
Marohasy notes that as catches have declined so have the number of fishers (partly voluntary exit and more recently progressive closure of the fishery). She suggests a better measure would be catch per unit of fishing of effort, which rose as numbers of fishers were cut.
But a course in Fisheries Economics 101 would have told her that’s exactly what you expect in this situation. Overfished stocks show diminishing marginal returns to effort, so a reduction in the number of licenses will produce an increase in average return to effort even if stocks are still declining. Marohasy isn’t an economist of course, but she ought to have checked on a basic point like this.
The real problem, though, is the doctored quote. If you want to attack the professional competence of a scientific study, let alone call it the “worst ever”, you should make sure your quotes are accurate and complete. Marohasy owes the authors of this study a big apology.
John Quiggin 
Nice cod piece.
Jennifer Marohasy! Ha-ha!
Lol, nice one, JF!
Interesting that Ms Marohasy is criticised on economic grounds, yet, the same ‘economists’ claim to know more about evironmental management issues than a scientist!
Something ‘fishy’ here!
Graham, yes, but I don’t really find her funny. The IPA is very chummy with the liberal government and the govt is unlikely to check her claims in the way Quiggin has.
What Helen refers to (the influence of the IPA and its environmental denialism on members the Federal Liberal-National Coalition) is, I’d suggest, part of a wider phenomenon of Federal Coalition politicians holding views and being subject to influences which are well to the right of views held by their support base, and particularly to the right of views held by the youngish suburban mortgage belt voters whose support, on the basis of perceived economic self-interest, was crucial to the Coalition’s success in 2004.
The continued support of these voters will be crucial to the Coalition’s re-election prospects in 2007. If the Coalition becomes politically vulnerable in the current term, it could well be the result of people within its ranks deluding themselves that the 2004 Federal election result constituted a “great Moving Right show” by the Australian public, and that there is a groundswell of support out there for anti-environmentalism, anti-abortion moves, hawkish foreign policy, etc., and a swingeing use of the Coalition’s Senate majority on such issues. As I’ve written previously, the young mortgage belt families wrought by fear of increased mortgage repayments due to a change of government will be even more wrought by the prospect of having an extra, unplanned mouth to feed and one less income with which to feed it.
No, I don’t really find her funny, except in a black humour vein. From what I’ve heard of her views on various environmental topics, she’s a running joke as an scientist.
It is this sort of selective quoting which makes a good faith discussion impossible.
Interesting that Ms Marohasy is criticised on economic grounds, yet, the same ‘economists’ claim to know more about evironmental management issues than a scientist!
the issue isn’t environmental management so much as comprehension skills, and in particular marohasy’s lack thereof.
Elizabeth,
The River Survey was prepared by the CRC for Freshwater Ecology which is an environmental science centre not an economics centre.
The second paper was prepared by Robert E. Kearney and Melissa A. Kildea of the Applied Ecology Research Group, University of Canberra.
How do economists (Other than JQ) come into it?
Incidentally, have you ever heard of enviornmental economics?
Yes Ian, I have heard of ‘environmental economics’. Doesn’t it have the same currency as phrenology? (Scratching my head!)
Elizabeth, I think your trolling style works better defending torture in the other thread. Leave this one to the grownups.
I completely agree with Ken Miles’s comment above. What value can a debate on the evidence have, when the evidence itself – in the form of quotations – has been so wilfully and crudely distorted? First-year arts students, as recently as the mid-1980s (and, for all I know, later on also), were very firmly rapped over the knuckles by their markers for that sort of sharp practice. But now it’s apparently compatible with obtaining a doctorate.
I have to say I’ve so far been very disappointed with Jennifer’s blog so far. I was expecting some good posts on property and tradeable rights approaches to protecting the environment from a classical liberal perspective and instead we have paeans to mercantilism (i.e. protecting the jobs of loggers of State-owned forests) and attacks on people for earning 200 grand.
Dear John – I apologise for my comment about environmental economics – see above! Just being mischevious.
And about the “Leave this one to the grownups” comment – thank you. As a 50 year old, it’s nice to think that the grown ups are much older than myself – that comment made my day.
I stand by my quote and assessment. The bottomline is that the researchers caught not a single Murray Cod in those sections of the Murray-Darling where the commercial catch for the same period was 26 tonnes.
They then used their ‘no cod caught’ result to have Murray cod listed under the EPBC legislation and reinforce the perception in the metropolitian media that the Murray and its fishery is stuffed. Local fishermen were outraged.
It is of most concern to me that basic data does not exist to adequately understand Murray cod population dynamics and develop appropriate management plans – yet we are spending so much money on research into the Murray-Darling system.
Sigh.
Does anyone want to explain to Dr Marohasy why you can’t “stand by” a quote that has been treated in this way (at least, not if you want to be taken seriously as a participant in scientific or policy debate). I’ve tried and failed.
Dr Marohasy should know better.
Aspects of the report have been published in the peer-reviewed scientific literature. As a starting point, I suggest:
Gehrke and Harris (2000) Large-scale patterns in species richness and composition of termperate riverine fish communities, south-eastern Australia. Marine and Freshwater Research: 51, 165-182.
In the meantime, as a former NSW DPI Fisheries field tech., I can assure you that while the sites themselves were selected randomly, a highly rigorous, intensive and stratified sampling design was applied at each site. The researchers have not “assumed a random distribution” as Dr Marohasy suggests.
As for Ian Mott, how he can imply that the large-scale clearing of lands in the Murray system has benefitted Murray Cod through increased flows, is beyond me.
Clearing of riparian areas severely degrades Cod habiat, the dams and weirs impeed migration, while the unnatural “substantial increase in dry season flows” merely interferes with spawning cues and floodplain innundation.
Cod need good habitat and natural flows regimes. Not misrepresentation of good science. I suggest that Dr Marohasy takes some time off to go fishing.
Also, walk into any pub in western NSW and you’ll find a wall covered with photos of trophy fish – there might even be a big Cod mounted above the bar. At the bar, however, will be 3 drunk idiots claiming that the reason scientists say there’s no fish is because ‘they can’t/don’t know how to catch them’. Louis Hissink and Ian Mott, the writing’s on the wall!