Lower Murray-Darling Catchment Action Plan: Fish Community Monitoring Report Card for 2008/09.
Gilligan D (2009) Lower Murray-Darling Catchment Action Plan: Fish Community Monitoring Report Card for 2008/09. Industry & Investment NSW – Fisheries Research Report Series No. 24. ISSN 1837-2120. 62pp.
|Lower Murray-Darling Catchment Action Plan: Fish Community Monitoring Report Card for 2008/09.
The Lower-Murray Darling Catchment Action Plan (CAP) identifies Riverine Health as a Catchment Target: “An identifiable nett improvement in riverine health across the Lower Murray Darling Catchment by 2015”. This annual report presents the freshwater fish data collected in 2009 and compares them with benchmark data collected in 2004 and monitoring data from 2006 and 2007, and assesses progress towards the CAP fish community targets.
At a catchment level, all the fish species collected in 2004, 2006 and 2007 were also collected in 2009, and no new fish species were recorded. Nine native species formerly resident in the Lower Murray Darling CMA area remain undetected since at least 2004.
The CAP target of a 55% improvement in the native: alien species ratio was not met in any catchment management zone in 2009. In fact, there was a significant decline in the native: alien species ratio in all individual catchment management zones apart from the Darling River. Since 2004, alien species have been expanding in distribution within the CMA area while the distribution of native fish has not changed. The species richness ratio has declined from 4 native species per alien species in 2004 to 2.7 in 2009.
The CAP target of a 25% improvement in the native: alien abundance ratio was exceeded in both the upper Murray River management zone and floodplain wetlands in 2009, but not across the catchment overall or within the Lakes & Reservoirs, Darling River or lower Murray River management zones. Although the median native : alien abundance ratios in the upper Murray River zone and floodplain wetlands exceed the CAP targets, the changes are not yet statistically significant improvements above the CAP target level, although they are obviously trends in a positive direction. However, the overall trend across the catchment area as a whole is a decline in the ratio of native: alien fish between 2004 and 2009 resulting from a decline in the abundance of native fish while the abundance of alien fish has remained stable.
The CAP target of a 25% improvement in the native: alien biomass ratio was not met in any catchment management zone in 2009. In fact, there has been a significant decline in the native: alien biomass ratio across the catchment area between 2004 and 2009. The total biomass of both native and alien fishes has declined since 2004, and the decreasing native: alien biomass ratio was driven by a 42% decrease in the biomass of native fish since 2004, while the total biomass of alien fishes declined by only 12%. The biomass ratio has declined from 792 grams of native fish to every 1 kg of alien fish in 2004 to 347 grams of native fish in 2009.
As at 2009, only two of 30 sites (7%) exceeded the CAP targets for all three ‘nativeness’ ratios. Nativeness was improving at a further five sites (17%), was stable at one site (3%), but had declined at thirteen sites (43%) and deteriorated substantially at nine sites (30%). Therefore, conditions are getting worse at around three quarters of the sites monitored.
Management actions implemented up until June 2009, and/or the extent of the works involved, have not been sufficient to result in acceptable progress towards the three Lower Murray Darling CMA CAP targets for fish community ‘nativeness’. At the current, rate of change, the Lower Murray Darling CMA will not meet its riverine health catchment management targets by 2015. Recovery actions for threatened species, ‘fish-appropriate’ wetland watering activities, utilising environmental water allocations to initiate recruitment of riverine fishes, investigating and remediating the lack of golden perch recruitment in the CMA area and implementing carp control activities are recommended as strategies to make progress towards achieving CAP targets by 2015.