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Research & Education
The Early Experienced Angler Catches the Trout in the Rubicon River | FN0597 |
John Douglas, Snobs Creek
April 2007
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For those in the know, the Rubicon River can provide good angling opportunities for trout.
The Rubicon River is a relatively small tributary stream of the Goulburn River, and is a popular recreational fishing destination.
However, anglers have noted that as the trout season progresses it becomes more difficult to catch a good fish!
Scientists from DPI’s research arm, Primary Industries Research Victoria (PIRVic), funded by Fisheries Victoria, undertook a two-year investigation to determine if the abundance of trout in the Rubicon River changes during the open trout season, which runs from September to June.
To do this, scientists led by DPI’s John Douglas, sealed off two sections of the river and caught all the trout present. The trout were measured and released back into the river. This survey was conducted six times over two trout seasons.
These population surveys found that while there were variations in the trout population over time, there was no overall decline in the numbers of “takeable” (i.e. trout >250 mm) during the fishing season.
The scientists then examined anglers’ catches and determined the numbers of trout caught and the numbers retained across the season.
While trout catch rates were found to vary throughout the season, there was no overall decline in catch rates. However, harvest rates of “takeable” trout did decline and the proportion of fish returned to the river increased as the season progressed.
The scientists concluded that “takeable” sized trout were usually present in the Rubicon River at all times during the open trout season, but these fish become less susceptible to angling as the season progressed.
Further analysis of anglers’ fishing practices and preferred fishing times revealed:
- a high level of catch and release in the Rubicon River fishery, with anglers returning about 50% of the brown trout they caught, and
- anglers fished the Rubicon River principally in the afternoons and early evenings.
The scientists also monitored water temperatures in the Rubicon River over the two fishing seasons, as this environmental factor has been known to change trout behaviour and catchability.
They found that as the season progressed, water temperatures in the Rubicon River increased and frequently exceeded 19°C, especially in the mid to latter part of the season.
By piecing together all this information, scientists have determined that two factors are at play in this trout fishery and essentially anglers are often trying to catch trout at the wrong time of the day.
The first factor at play is the high levels of catch and release that occur in the Rubicon River. The researchers believe that anglers may in fact be training trout to avoid them.
This theory is supported by some work done in New Zealand, where the catchability of trout in a lightly fished river decreased as angling activity increased.
The New Zealand study also found that trout living in rivers with a lot of human activity became accustomed to it. High levels of human activity are thought to modify trout behaviour, making the trout only likely to move into the open and feed when human activity is low.
The other factor that impacts trout catchability is water temperature. Trout feeding slows with increasing water temperatures and feeding stops at around 19°C. Water temperatures of 19°C or above are known to depress trout catch rates, as trout are not interested in eating.
Most anglers fishing in the Rubicon River finish their fishing session on, or just after sunset. It is very likely that anglers’ inability to catch “takeable” trout as the season progresses is because they are fishing at the times when trout are least likely to be tempted by the food (bait, lure or fly) offered by the angler. This occurs when:
- trout become “trained” to angler’s wiles,
- human activity is high, and
- water temperature is high.
Essentially, the study found anglers are fishing when Rubicon River trout are not feeding (day) and are going home when the trout begin to feed (night).
Therefore, as the trout season progresses, anglers are more likely to catch “takeable” trout when the fish are more likely to be feeding (i.e when water temperatures are cool and human activity is low). The coolest water temperatures occur in the early mornings—a time when, traditionally, Rubicon River anglers don’t usually frequent the river and human activity on the river is low.
While fishing when trout are ready to feed will increase an anglers’ chance of catching a “takeable” trout, the anglers must still use all their skills and guile to outwit the fish. In such cases, angling experience is a very important factor for fishing success.
“Thanks to the healthy stream environment, low harvest rates, and a high rate of catch-and-release; it is not the abundance of trout that changes throughout the fishing season; it is the behaviour of the trout. Anglers can be reassured that the present behaviour of those fishing the Rubicon River is supporting a sustainable fishery,” John said.
Further Information
For more information about this project, please contact Mr John Douglas at, PIRVic Snobs Creek on (03) 5770 8000.
Fisheries Research and Education Notes are available on DPI website.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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