trout predation on blackfish CIRCLEDSKaminskas

A Not-So-Magic Moment

A Not-So-Magic Moment

 

By Simon Kaminskas, 27 May 2014.

 

In early May I caught a ~40 cm alien Rainbow trout (Oncorhynchus mykiss) in the Cotter River between Bendora Dam and Cotter Dam (in the Australian Capital Territory). I cleaned it and inspected its stomach contents … and discovered this trout had killed a 5 cm SL native Two-spined blackfish (Gadopsis bispinosus) earlier that day. Being in a gloomy section of river late in the day, I scrambled up a nearby scree slope to catch the late afternoon sun and illuminate this sad scene for a photo.

I have had the privilege of seeing Two-spined blackfish in the wild and in aquaria, and they are beautiful, charismatic little native fish with a lot of personality. I was deeply saddened to see one of these beautiful native fish ending its days in the gullet of a tawdry, extremely over-rated and unnecessary feral import … and promptly wondered how often this happens, unrecorded.

It’s not the first time. Over the years, I have recovered about seven Two-spined blackfish (~5 cm to 11.5 cm SL) and several juvenile Macquarie perch (~5 cm SL) from the gullets of Rainbow trout in the Cotter River system. Most of these observations (but not all) were made in the mid to late 1990s when I fished the Cotter River very frequently. It’s worth noting that I (foolishly) released most of my trout back then — had I kept them all, imagine how many more instances of trout predation I may have found! I also never happened to have a camera on me.

I am strongly critical of the impacts of alien trout — and in some cases, ongoing irresponsible stockings of alien trout — on upland native fish as well as other upland fauna such as the Spotted tree frog (Litoria spenceri), the Giant alpine stonefly (Thaumatoperla alpina) and spiny crayfish species of the genus Euastacus. I am of the considered opinion that the impacts of alien trout in Australia have been vastly underestimated. Historical evidence (e.g. Trueman, 2007, 2011), circumstantial and biological evidence (Cadwallader, 1996; Lintermans, 2000; Gilligan, 2005) are very substantial and very thought-provoking. But it is the parallels with terrestrial Australian wildlife — which have indisputably been devastated by alien terrestrial predators (e.g. Woinarski et al., 2014) — that really highlight the inherent absurdity of the all-too-often repeated claim that alien trout species, and decades of irresponsible saturation stockings of alien trout species, have had little or no impact on upland native fish and upland native fauna (e.g. NSW Fisheries, 2003; see also Halverson, 2011). And certainly alien trout impacts in Australia have been almost wholly unstudied. Ironically, with less and less upland native fish populations (particularly Murray-Darling Macquarie perch) surviving, opportunities for such studies become ever fewer.

I now carry a camera every time I go trout fishing, to photographically record examples of alien trout predation on native fish. This is my first photographic record.

References

Cadwallader PL (1996). ‘Overview of the Impacts of Introduced Salmonids on Australian Native Fauna’. Australian Nature Conservation Agency, Canberra. Available online at: http://www.environment.gov.au/resource/overview-impacts-introduced-salmonids-australian-native-fauna

Halverson A (2011). ‘Chasing Rainbows’. Conservation Magazine, 22 November 2011. Available online at:http://conservationmagazine.org/2011/11/chasing-rainbows/

Gilligan DM (2005). ‘Fish communities of the Murrumbidgee catchment: Status and trends.’ NSW Department of Primary Industries – Fisheries Final Report Series No. 75. Available online at: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0007/136933/Output-545.pdf

Lintermans M (2000). Recolonization by the mountain galaxias Galaxias olidus of a montane stream after the eradication of rainbow trout Oncorhynchus mykiss. Marine and Freshwater Research 51: 799–804. http://dx.doi.org/10.1071/MF00019

NSW Fisheries (2003). Freshwater Fish Stocking in NSW. Environmental Impact Statement. Available online at: http://www.dpi.nsw.gov.au/fisheries/recreational/info/stocking/ffs-eis

Trueman, W.T. (2007). ‘Some Recollections of Native Fish in the Murray-Darling system with special reference to the Trout Cod Maccullochella macquariensis’. Native Fish Australia (Victoria) Incorporated, Doncaster, Victoria.

Trueman WT (2011). ‘True Tales of the Trout Cod: River Histories of the Murray-Darling Basin’. MDBA Publication No. 215/11. Murray-Darling Basin Authority, Canberra. Available online at: http://truetales.com.au/

Woinarski J, Burbidge A and Harrison P (2014). ‘The Action Plan for Australian Mammals 2012’. CSIRO Publishing.

 

About Me

Simon Kaminskas with trout (Tumbie)

My burning passion is the Maccullochella cod species, but I have a penchant for percichthyids, and native fish generally. I managed to never become a fish ecologist, despite strenuous effort and study. Instead, I wander the Commonwealth environment department like a displaced percichthyid and contribute to good policy outcomes, big and small, for native fish. I am a passionate fisherman, strictly catch-and-release with native fish, and love keeping native fish in aquaria too. Curious facts: I had a (tiny) meteorite burn up a few metres above my head one fine night; my favourite meal is the hearty French dish cassoulet.