Document ID: chunk:federal_register_of_legislation:F2019L00106:body:0:p41
Version: federal_register_of_legislation:F2019L00106
Segment Type: other
Provision Reference: 
Character Range: 109201–112056

about the ability for native fish and trout to coexist (Butcher 1967; Cadwallader 1977; Rhodes 1999) and the impacts of 'incessant' trout stocking in the Murray-Darling Basin and that little information on the composition of native fauna was available before the first trout introductions were made (Cadwallader 1978). Rhodes (1999) in recollecting discussions with older men in the northeast of Victoria during his time as a fisheries officer, noted the correlation between the increasing presence of trout following stocking efforts, and the decline of 'white eye' in the catches of recreational fishers in the upper Murray region, especially around the 1930s. In analysing the disappearance of Macquarie perch in Lake Eildon, Cadwallader & Rogan (1977) drew attention to the stocking of more than 750 000 rainbow trout and more than 250 000 brown trout were liberated into the lake between 1958–1967, and predation and competition with introduced fish species (including redfin, goldfish (Carassius auratus) and tench) was considered as one the of three factors (the other two factors were considered to be large harvests during spawning time and habitat change) in the species disappearance.
There is an increasing awareness of the risk that trout may pose to Macquarie perch recovery and brown trout is considered by the New South Wales Fisheries Scientific Committee as a contributing factor in the decline of Macquarie perch (NSW FSC 2008). While Ebner et al. (2007) report no evidence of trout predation on juvenile Macquarie perch in the "upstream" parts of Cotter Reservoir (as opposed to Cotter River itself), they importantly note that juvenile Macquarie perch were absent from the survey area. Gilligan (2005) correlates the decline of Macquarie perch in the early-1980s in the upper Murrumbidgee River with the first year of a series of very large releases of rainbow trout in the area starting in 1980. High numbers of brown and rainbow trout have been observed around spawning aggregations of Macquarie perch in the Mitta Mitta River and were likely preying on larval and juvenile stages (Tonkin et al., 2009).
The incidence and severity of trout predation on Macquarie perch has only been assessed through visual examination of trout stomach contents. This is unlikely to detect egg or larval predation on Macquarie perch, and such life stages are highly disgestible and are likely only to be visually identifiable for several hours after ingestion (MacDonald et al., 2014). While documented occurrences of predation on Macquarie perch are scarce, there have been almost no studies commissioned in Australia into the physical examination or DNA-assays of trout gut contents in the few remaining locations where Macquarie perch still co-occur. Research commenced into this approach (MacDonald et al., 2014) but ceased as a result of a lack