fishy science …

The science of climate change just turned fishy. I call this ‘cods-wallop’. Warming Prompts Range Expansion of West Australian Reef Fish

The study area must have been just a few hundred metres offshore from the researchers home port. The way to study climate changes.

Choerodon rubescens is a subtropical wrasse endemic to Western Australia that is an important commercial and recreational fisheries target throughout its normal distribution, primarily along the central portion of its range. More recently, however, catch records indicate that the popular reef fish has become more common in the southern part of its range, suggestive of the possible poleward expansion or shifting of its preferred habitat.

To explore this possibility, Cure et al. (2015) assessed the size structure and habitat associations of juvenile C. rubescens during the summer and autumn of 2013 (January-May) by means of an underwater visual census conducted across available shallow water habitats towards the southern range edge of their historic distribution (32°S, 115°E). And what did they discover by so doing?

The three Australian researchers report that “high abundances of juveniles (up to 14 fish/40 m2) were found in areas where they were previously absent or in low abundance.” And based on the size structure of the populations they encountered, they say that “recruitment was estimated to occur during summer 2011-12 and 2012-13,” which “coincides with water temperatures 1 to 2°C higher than long-term averages in the region, making conditions more favorable for recruits to survive in greater numbers.” And in wrapping up their report, they say it “mirrors the well-established patterns observed on the east coast of Australia,” citing the studies of Booth et al. (2007), Figueira et al. (2009), Figueira and Booth (2010) and, last of all, Last et al. (2011).

My personal experience of this fish, the Baldchin Groper, is by catching some in the same vicinity, let me see, about 40 years ago, a few km SWest of Yanchep. That distribution of Lat/Long above is the Rottnest Trench, a patch of ocean over a thousand metres deep. 32S is just a few km South of the fish I caught, but stretching the truth to invoke climate change must be a part of receiving extra funding. “Possible Poleward Expansion”? Codswallop. The tropical Spanish Mackerel was sometimes caught 40 years ago too, another 300km further south than this, during an occasional year of above average SSTs (sea surface temperatures).

I have also seen specimens of the Southern Pink Snapper, caught offshore from tropical Broome. Is that ‘Global Cooling’?


  • codswallop
    [ ˈkädzˌwäləp ]

    NOUN BRIT. informal
    Powered by OxfordDictionaries · © Oxford University Press


About Tom Harley

Amateur ecologist and horticulturalist and CEO of Kimberley Environmental Horticulture Inc. (Tom Harley)
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