by Greg French
Gum beetles are revered by some anglers and hated by others. Occasionally the fishing gods get things right and there is just the right smattering of these beetles to provoke action.Greg French looks at the good and difficult times that gum beetle hatches bring.
Gum beetles stimulate spectacular summertime rises, especially on the Central Plateau where, along with mayflies, they provide for definitive summertime dry-fly fishing. So let's learn a little more about them and have a guess at what this coming summer will bring.
In Tasmania there are more than thirty species of gum beetles (Chrysomelids) but one species, Chrysophtharta bimaculata is predominant and it is this beast that you are most likely to find in the stomachs of trout. These beetles over-winter in cracks of dead wood and under bark and are not commonly seen until spring, when warm sunny days cause them to become active. They eat gum leaves, favouring the tender new growth of ash species (gum tip, stringy bark and swamp gum). The majority of eggs are usually laid in two peaks - late November/early December, and late January/early February - though this is subject to seasonal factors such as warmth, wind and rain. The larvae are even more voracious feeders than adult beetles, and under exceptional circumstances, they can strip whole trees of almost every leaf.
In places which are sheltered and of relatively low altitude (like Dee Lagoon at about 650 m), beetles can often be seen flying about and falling onto the water by early November. In higher, more exposed habitats (such as Great Lake at almost 1050 m), significant falls might not occur until Christmas time, but all this varies according to prevailing conditions. Last year was a massive beetle year. According to the botanists I have contacted, all that defoliation you have probably noticed on the Plateau (especially around Great Lake, along the Marlborough Highway and in the southern half of the Western Lakes) has been caused by beetles. The weather can become pretty harsh in the highlands and normally the majority of beetles would die during winter. However, last year was so mild that survival has been high. Since warm conditions have continued throughout spring, the beetle falls have been remarkably early and big.
There were memorable dry-fly days at Lake Skinner (altitude almost 1000 m) in October! I also heard of superb dry-fly fishing at Lake Echo at the same time. Generally the beetle population increases in late summer, presumably because it is augmented by young beetles from the early egg-laying session. The indicators are that this coming summer will be hot and dry, so I would not be surprised if we witness one of the biggest beetle events in living memory. This may be a very bad thing for those stressed-out trees in the highlands. If they are defoliated again, it is probable many will not cope. It may even be that whole forests are destroyed.
Predictions for this season
As for this year's trout fishing, huge numbers of beetles are a mixed blessing. When there are very few beetles about, trout do not stay on the surface long enough to provide good sport. But if there are too many they gorge themselves and stop rising. (I have seen falls so big that huge rafts many beetles thick and tens of metres long have formed in the wind lanes and along exposed shores.) Ideal conditions occur when there is just a fair sprinkling of beetles about, and then the trout will feed much as they do during a good dun hatch, chomping down one beetle after another. So, this summer, the best beetle fishing will likely be during marginal conditions: early in the morning and when things are a little cold.
I have noticed that the trout are sometimes forced to be selective. Once on the Dee there was so much wattle blossom on the water that the trout simply would not take a yellow fly. Another time in the far Western Lakes and abundance of fagus leaves caused the trout to be wary of anything brown. I usually opt for fairly good imitations along the lines of Sloane's plastic gum beetle, though during these two events a Red Tag proved far more effective. Bruce Gibson from Burnie ties a very good beetle and these are widely available. Often though the fishing is just plain tough. I've seen good falls when the trout have taken naturals with gusto, mopping up every one in sight, but have refused absolutely every fly in my box. And that, of course, is what makes fishing for beetle feeders so damned addictive.