Effects of irrigation pumps on riverine fish.
Baumgartner LJ, Reynoldson NK, Cameron L and Stanger JG (2009) Effects of irrigation pumps on riverine fish. Fisheries Management & Ecology, 16: 429-437.
Available online: http://dx.doi.org/10.1111/j.1365-2400.2009.00693.x
The Murray-Darling Basin is Australia’s largest catchment covering over one million square kilometres. Despite receiving little water, the Murray-Darling Basin supports at least 40% of Australia’s agricultural production, a population of over 2 million people and is one of Australia’s most important natural resources. Such a degree of development has led irrigation to be the largest user of water in the Murray-Darling Basin.
The study focused on determining the potential effects of direct extraction of fish via pumping systems. Work was undertaken, between November 2004 and April 2006, on the Namoi River between Wee Waa and Narrabri. A combination of boat electrofishing, fyke netting and larval trapping was used to determine the relative effects of high and low volume irrigation pumps on fish. Collections were undertaken during the day, and also at night, to determine if more fish were removed more frequently at different times of the day.
Over 2,300 fish were trapped in the pump outlets over the study period, with 7.5% of the total killed or injured. The maximum number of fish extracted in a single day was 232. Mortality rates were significantly higher from the high volume pump site, but only large (>200mm long) or small (50mm long) fish were killed. Medium-sized fish (50 - 200mm long) largely survived the extraction process. Electrofishing further demonstrated that few species established populations in the associated storage systems, suggesting limited survival through pump systems.
Fish that survived the extraction process had no opportunities to return to the main river system and were effectively classified as ‘lost’ from the main river population. The development of suitable mitigation measures, such as operational changes or screening, is suggested to prevent extraction. If these mitigation methods are agreed to by all stakeholders, and implemented in a logical and systematic manner, the long-term effects of irrigation pumps on fish could be greatly reduced.