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Video killed the cod mystery

By Ebb and Scott Hardie

The first presentation that Gav Butler gave on the use of underwater video at an Australian Society for Fish Biology annual conference was a cracker. It was the single most exhilarating freshwater talk I (Ebb) have experienced at an ASFB session (having attended about 15 of the past 20 such events). At the society congress in Darwin this year, Scott Hardie mentioned to me that he was equally impressed by that same talk several years ago, and these are some of our recollections…

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The above water business of a shore-mounted camera system used to perve on Eastern freshwater cod (Photo courtesy of Dr Gavin Butler).

What I (Scott) remember was that this Butler fella experienced some technical difficulty in getting the damn thing to play (as was the norm rather than the exception with any talk relying on playing a segment of video in those days). Because of this, I thought it was a brave thing to have a crack at while the spotlight was shining brightly. Turned out to be well worth the effort though. I’m pretty sure it was in my neck of the woods in Hobart in 2006 (any thoughts Ebb?). A few things stood out to me about this presentation. Firstly, I was envious of his ability to get footage of reproduction in action, having worked on fish in highly turbid water for several years, where getting this type of information was simply impossible! Secondly, there was a huge WOW factor associated with the footage – it had obvious appeal to fishos who were seeking to understand what the hell goes on when fish breed, but maybe even more importantly this type of info could be used as an invaluable communication tool for stakeholders and general punters. It certainly opened my eyes to what could be done with underwater video… if a picture is worth a thousand words, this was a machine gun!

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The wiley Gav Butler

Above all else, what we both recall was that it was inspirational, with the camera rolling and some stellar footage. The cavernous rock grottos covered in pearls, and a big cod aggressively guarding its nest against a persistent eel. The radio-tracking era was well underway by that stage, and larval sampling in the Murray-Darling Basin was off to a start. However, what was unfolding before our eyes in that talk was the beginning of another trick for the trade, a new way of doing freshwater fish ecology: filming fish behaviour in the field. And for all that we knew of the Maccullochella, here was the first evidence that freshwater cod guard not only their eggs but also the early post-hatch phase larvae. To be having a beer in Darwin and come to the conclusion independently of the same magic moment, well we think that’s just Jim Dandy.

Further reading:

Butler, G. L., and Rowland, S. J. (2009). Using underwater cameras to describe the reproductive behaviour of the endangered eastern freshwater cod Maccullochella ikei. Ecology Freshwater Fish 18, 337–349.