Just back from a great meeting with the Fisheries Victoria team running this project (part funded by recreational fishing licence revenue), along with researchers and members of the Wild Trout Reference Group. The latest developments include:
– the researchers finishing this season’s surveys of the 12 priority rivers and logging the results, and
– the first download of information from the Delatite River ‘listening posts,’ recording hourly water temperature and movement of acoustically-tagged wild brown trout. (See https://flystream.com/2015/04/04/wild-trout-program-update/)
Electrofishers at work. (Pic. J Lieschke)
The researchers are careful to point out that the data from both projects hasn’t been fully analysed yet, and in any case this is only year one of a three year study. However, there are already fascinating glimpses of what’s been discovered.
On the Delatite, the listening posts are showing that stream temperatures can fluctuate up to nine degrees within a 24 hour period on hotter days, while on the 12 priority rivers, researchers are noticing some interesting patterns. For example, there continues to be a trend (first observed in survey work pre-dating the Wild Trout Program) for trout numbers to be highest in the upper reaches of surveyed streams.
Releasing surveyed trout after being weighed and measured. Knowing length & weight allows trout condition to be assessed. (Pic. J Lieschke)
However, when it comes to trout size, the biggest fish are appearing in the mid-reaches of the streams. On this point, researcher Jason Lieschke commented that his team could often predict in advance that certain survey sites were more likely to produce a biggun’. Stream sections with very good instream cover like boulders, snags and undercuts were often candidates to hold a large trout or two. Trophy hunters note!
A big one goes back after having its details recorded. (Pic. J Lieschke)
Incidentally, priority river survey sites (usually 100 to 250 metres long) are selected based on a connection to historic surveys, with most of these having previous random selection. In other words, the researchers can’t consciously or unconsciously ‘choose’ a site to survey, so bias is avoided.
The specific results so far are too numerous to list here and now, but a few snapshots will be of interest.
– A 120 metre stretch of the Big (Mitta) River (near the Omeo Highway between Anglers Rest and Glen Valley) surveyed this March produced 47 wild brown trout from 6 grams to 2.1 kg!
– A 200 metre stretch of the upper Howqua River produced 48 wild browns and 95 wild rainbows.
– A 180 metre stretch of the upper Goulburn River produced 56 wild browns and 91 wild rainbows. Most of the rainbows were young-of-the-year, indicating very good natural recruitment in 2014. (Incidentally, these numbers would extrapolate out to over 800 trout/km or in USA lingo, 1300 trout per mile!)
– A 200 metre stretch of the Ovens River at Harrietville was surveyed soon after the fires in 2013, with few fish recorded. It was re surveyed in March this year and researchers found 39 wild rainbows and 10 wild browns with the wild browns ranging from 157 to 502 grams. Pretty good natural recovery!
A nice stretch of the Howqua just after being surveyed. (Pic. J Lieschke)
Meanwhile, Fisheries are organising an event for anglers this November where the Wild Trout Program findings to date will be presented in detail, along with some early analysis. Event details will be announced soon.
(PS: Just chatted to one of the Fisheries staff who was at the meeting – he and Jason headed out for a fish on the Goulburn near Thornton afterwards; apparently a great evening rise to Kossie duns and they landed 4 trout, including a cracking brown.)
