Friday, May 26, 2006


(And maybe some good news on species extinction)

Well, it's stacks on the mill over at Larvatus Prodeo, now that some idiot has let slip to Dr Jennifer Marohasy that yours truly had doen a bit of a hatchet job on her recent post on salinity in the Murray River. So much for the spell of ennui I was planning for the rest of this week and most of the next - I may have to go with the schadenfreude option instead. Fine by me, as long as I'm not the one providing the schadenfreude.

Moving right along, in a spirit of something approaching fair-mindedness, I recently downloaded Dr Marohasy's IPA backgrounder Myth & the Murray: Measuring the real state of the river environment (PDF) from the IPA site. So far I've only had time to skim the report, but this section piqued my interest:

The Cooperative Research Centre (CRCFE) survey Fish and Rivers in Stress: The NSW Rivers Survey is generally considered the most comprehensive survey of fish in the Murray–Darling Basin. The survey does not provide any data from which trends with respect to improvement or deterioration in fish numbers can be determined. However, the survey undertaken in the mid-1990s does claim to give an indication of the abundance of fish in the Murray River relative to other rivers.

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.’ [Dr Marohasy's emphasis]

A good scientist is usually wary of an absence of data. An absence of data (namely, catching no fish) could be an indication that, for example, they got their sampling method (that is, their fishing technique) wrong, rather than that there were no fish.

I have no major disagreement with that last paragraph - I remember applying much the same principle in my own science education, years ago. If, for example, you wanted to check whether a stream was contaminated with E coli, you'd go out, collect water samples at various locations, take them back to the lab and then put yourself through the tedious business of mixing measured amounts of stream water with nutrient medium, incubate the mixture for a known period (corresponding to a calculable number of bacterial reproductive cycles), serially dilute the resultant cloudy broth then pour measured amounts onto agar plates. Once you got that done, you got to the fun bit - using the dinky colony counter machine to mark all the bacterial colonies on your agar plate, while the counter mechanism clicked over every time you pressed the special marker pen on the base of the plate.

The trouble was, if your agar plates were clean, you'd miss out on the fun bit with the colony counter. To make matters worse, you would have to conclude, on the basis of the available data, that the stream was totally uncontaminated by any bacteria, let alone E coli. Apparently, though, good scientists don't take this approach when it comes to the question of whether a river is contaminated by a particular species of fish. Finding no fish in the river, despite your best efforts to do so, is not enough evidence to infer that the river is most likely fish free. Well, you live and learn.

I suppose the same principle applies to potential bird contamination of wind-farm sites - well, it does according to Ian Campbell. All up, this has to be good news when it comes to species we used to think were extinct - for example, the continental USA is widely believed, on the available data, to be completely uncontaminated by Passenger Pigeons and the island of Mauritius, on the same grounds, is considered free of Dodo contamination. But clearly, we've got it wrong. Any day now, these lost species might turn up, like one of those two dollar coins that starts making an almighty ruckus when it falls out of one of your pockets in the clothes dryer. And for all we know, there might well be a few piles of unicorn manure somewhere that have been mistaken for the horse variety. no good scientist could rule ou the possiblity out on the grounds that everyone "knows" that unicorns aren't real.

Nah - I think I might take the ennui option anyhow. Too many pieces in the "to-be-completed" queue - like the next episode of that damned serial. And I owe myself at least a few hours of relaxing to great symphonies with rushed openings, missing repeated sections and sub-standard maestoso passages.


Shaun said...

Nice one Gummo. Thanks Dr Marohasy I can go back to my cryptozoology research. The reason I have not yet found a Yowie is that I am using the wrong sampling method.

Helen said...

Gummo, since i used that anti-terrorist gel I bought on the internets, there have been no terrorists sighted around chez Balcony. I rest my case.

Anonymous said...

That's by far the least of Marohasy's sins in this section. See her play fast and loose with quotations


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