Steel Blue Lampreys – Geotria australis – for trout in estuaries around Dunedin
By Monty Wright
For those anglers who do not fish during the winter months in the estuaries, they will know little of the small creature which at present is making its way to the sea to complete its life cycle. These are the young steel blue lampreys.
The majority of anglers identify with the adults which come in from the sea heading up all of our rivers to lay their eggs and start a new life cycle. The eggs, after hatching into small fish, which then live in the mud along the edges of our rivers and streams, are called “ammocoetes.” They have no eyes, only a feeding mouth, and are coloured dark brown to grey.
After several years it is time for them to go to the next part of the cycle and prepare to move back to the sea to grow to adults. These juveniles, at this stage, are called “macrophthalmia” and a colour change takes place.
At this stage of their lives, they change to an iridescent silver blue and their eyes appear for the first time. They then start to move on downstream into the estuaries heading for the sea. Of course at this time they are very vulnerable to the trout living within those estuaries.
The small fish range in size from 80 – 120mm and generally migrate in ones and twos, not in shoals as small fish species tend to do. Photograph of Lamprey Geotria australis by Stephen Moore at teara.govt.nz – Encyclopedia of New Zealand.
I first became aware of them passing through the estuaries at this time back in the late seventies while fishing the Railway Bridge hole at Otokai on the Taieri River mid-afternoon on a turning tide. I had caught a fish, a brown trout, which had four of these steel blue lamprey in its stomach. At least once a year an angler brings some of these small steel blue lampreys into our Fish and Game office for identification as they have found them in exactly the same place and wonder what they are.
Steel Blue Lamprey Imitations
The first imitations I used were a thin cut of rabbit skin with the fur left on and tied on a long shanked hook. These appeared quite grey but successfully caught the trout. More recently when in Centrefire Sports shop I observed some dyed blue hackle feathers. Instantly I related the colour to the steel blue of the lamprey. I purchased a packet and headed home to tie some new innovations.
On a long shanked hook, I first tied in, with clear thread, some crystal flash for the tail. I used about three strands which were kept long. Leaving the clear tying thread at the end, I tied on a pearl body using Christmas decoration which I have since replaced with pearl ribbon. This is available on a reel from most fly tying shops. The slender body was built with this pearl and tied off at the head with the normal tying silk.
Then in Matuka style, I tied one blue feather on the back, winding the clear thread through to the head. Before tying off I put two strands of crystal flash on each side of the feather. These run the full length of a feather. I then tied off and cemented the heat with clear cement.
On returning from some work on the Maniototo during September, I noticed that the water level was about right in the Waikouaiti Estuary. I decided to try my new creation and also my luck. After 20 minutes I thought that I was going to be unsuccessful but then I caught my first fish, a nice trout of about 2kg.
On inspecting the stomach contents there was two blue lamprey inside, along with three or four pieces of worm and some shrimps. Ten more minutes of fishing and I hooked my second trout and on inspecting the stomach of this fish I found it had one lamprey in it, along with a multitude of other bits and pieces. I then headed home quite satisfied.
I am unsure whether the small lamprey moves through the estuary all year. But it appears that there is a build up through the months of June and August. Maybe this is when I fish estuaries more and find them in the stomachs of some of the trout I take home.
I generally fish my lamprey limitations in tandem, with one tied onto the shank of the other, on whatever line is necessary for the area that I am fishing. For instance, in the Waikouaiti River I use a sink tip, but in the Shag River, because it is clearer water, I generally use a floating line. If I’m fishing deep holes on the Clutha or Taieri Rivers I will use a high-density super sink line. I have had the best success on the turning tide or when the tide is going out, but again this is a generalisation as that is the time that I normally fish these waters.
I cast the lures out into the middle of the stream and let them swing back in against the bank. Most fish are taken against the bank on which I am walking down. Then I do a slow retrieve for about two metres of line, lift, cast out, then take three paces, and then carry out the same procedure again. You have to be alert as when the trout take them it is more like a sucking action and a slight tug as if you have snagged a piece of weed. I always just lift the tip of the rod in case the trout has taken the lure. It appears they just sip them in and don’t hit them violently like some other species that you find in estuaries.
If you have put your fly rod away for the winter you are missing out on a lot of excellent fishing. Although the weather is colder and the visits shorter there is always some way to tempt the trout. Why not have a try fishing steel blue lampreys.