Manu

Manu Esteve, postdoc from University of Toronto is studying behaviour of the Salmonidae family (this family includes trout, salmon, grayling, charr and several others). He recently published some pictures from his expedition to Slovenia, observing the spawning habits of marble trout.

Urška is back

Urška has returned from maternity leave last month. She has noticed some changes on our site and wanted an animated gif that some BTGR members already have.

And after a few minutes, the result:

An interview and a fishing story

James Prosek was interviewed by The Itinerant Angler, you can also download the interview (mp3, 41 MB). Among other things he mentioned our group and one of the more memorable field trip. He mentioned that he personally wasn't there, but Steve and Aleš often entertain us with the story.

Fishing story

In 2004 a field trip to Montenegro was organized, involving people from Austria, Slovenia and Serbia, along with local biologists and fisherman. The primary motivation for this trip was to search for the extremely rare and perhaps extinct form of softmouth trout from the Zeta River. The group was well equipped to sample trout, bringing several experienced fly-fisherman, an inflatable boat, and a 5 KW stationary electro-fishing generator, lugged all the way from Austria. The first glimpse of the Zeta generated quite a bit of excitement in this fish hungry crew. The river was surprisingly large and deep, lined with overhanging trees, and teeming with invertebrate life. While we did not necessarily expect to immediately find softmouth trout, we assumed that other trout would be plentiful. However, it quickly became painfully obvious that our experienced and well-equipped crew lacked a certain something necessary to catch Zeta River fish. The first reaction was natural – there are no fish! But each evening around sunset a local guide, Mlađen, who was observing us with some amusement the whole time, slipped away from the café veranda overlooking the Zeta - within an hour or so five or six plump freshly brown trout were slapped down before our eyes. Suspicions, confusion and frustrations were being muttered among us before the fourth evening when Mlađen offered to take Steve along and open Zeta’s door of enlightenment. Some may have thought there was a pond or hatchery around the bend that Mlađen would finally reveal, but instead he pulled one shy trout after another off the bottom of the Zeta with a Tyrolean nymph rig, sometimes from the same run where Steve had just thrown the same rig, 20 times. The rig was key, but not in anyone’s hands as it seemed that only Mlađen had some kind of Dr. Dolittle-like bond with Zeta’s trout. Nonetheless, even he could not come up with any softmouth, are real quarry.

Nearing the end of our week, the pessimism had reached its peak and some of us took a side trip to visit the famous monastery Ostrog, nestled into the high cliffs of the upper Zeta valley. According to common belief, wishes made in certain holy nooks of the monastery can come true. Maybe this is really so, because later in the day upon returning to the river we were approached by a local man who had heard of our struggles to find softmouth trout. He claimed to know where some were, in a small tributary of the Zeta, a few hundred meters from that all too cosy café on the banks of the Zeta. This was our last chance, though we were skeptical. Our skepticism increased as we gazed into the little stream’s clear waters which, like those of the Zeta, revealed no image worthy of even a mirage of a trout. But Johannes, the Carinthian baker who doubles as one of the more well-known explorers of exotic populations of Salmo, quickly donned his snorkelling attire, and made a survey more reliable than any we could have managed with fly lines or electrofishing gear. There were indeed softmouth trout in the stream!

Now we just needed to catch a few. A circus-like atmosphere soon developed, as we dragged the inflatable boat and electro-fishing gear across a meadow, attracting not only an increasing number of people, but a local television crew as well. As fate would have it, the Zeta softmouth, like the Zeta brown trout seemed immune to electricity, managing to stay on the move and just outside of the field around the anode, as if they were well trained. Our growing frustration was being intently monitored by Đoko, the guy who told us about this secret location. Afterall, he had PROMISED we would catch fish. Suddenly he couldn't stand it any more; he slipped into his wet suit, complete with mask, snorkel and fins and waded slowly into the shallow borders of an otherwise three meter deep pool. Observing his gesticulations, we slowly realized what his intention was: he wanted to dive with the anode pole in his hand and try to “harpoon” the fish with the electric field from a close distance. As the vision of this Rambo-esque plan unfolded in everyone’s minds there were varying degrees of resistance, ridicule and shock. With television cameras ready to roll, a multilingual cacophony rose around the pool as each person attempted to define their level of involvement, ranging from pure disassociation to neutral curiosity and on to legal culpability as expressed by Steve who had organized the Austrian crew and University owned electric-fishing set-up. He screamed: “No, no, no…!” But Danilo, from the University of Montenegro tried to explain to Steve that the man had indeed promised we would catch softmouth, and thus, by some rural code of honour he was determined to deliver, and there was nothing we could do to stop him. The decision was made to proceed, but with pre-determined hand signals and a hand on the off/on switch of the generator. Đoko finally got hold of the pole and quickly dove into pool. His hand went up, signaling for the juice, but he quickly emerged shaking his head in disappointment as the generator was correspondingly shut off. He dove again, gave the sign and everyone gasped at the sight of a swirl and a few bubbles – the electricity was only on for a few seconds, but Đoko emerged triumphantly with a softmouth trout in his net, igniting a cheer and celebration on the banks as if a golden-goal had just crossed the net. The act was repeated and several softmouth were landed in a similar fashion.

There were long debates on the dangers and dynamics of electric currents in water, of grounds and wet-suits and insulation. The popular outcome of this action was most likely the result of the fact that the man was indeed quite distant from both the anode and the cathode, with the electric field held out several meters in front of him at the end of a long anode.

P.S. Please note that the authors adamantly discourage anyone from repeating the actions described in this story. Fishing with electricity can be dangerous and should only be done by licensed operators, and all safety regulations should be followed, which in most countries explicitly forbids any form of diving during a sampling action.

Annual testing of marble trout from zone of hybridization

Just like last year, we performed genetic testing of fish from the zone of hybridization. This year we have received fin clips from 33 individually tagged trout from 2 locations: the River Tolminka, tributary of the River Soča and from the River Soča just below the town of Kobarid. These samples were checked for non native genetic characteristic on 5 nuclear genetic markers (each genetic marker in 2 copies, one allele inherited from each parent) and on 1 mitochondrial genetic marker (in 1 copy, inherited from the mother only). Out of 33 samples, 8 show signs of hybridization with non native trout, 1 sample (sample 20) will not be used because of low quality of DNA isolate. Eggs and sperm will be taken from 24 trout with no detectable brown trout genetic characteristics, fertilised and raised in the hatchery and released back in the zone of hybridization.

Below is a simplified table of genotypes. These genotypes are not publishable, since the initial sampling was biased, only marble trout (by general appearance) were sampled, so the actual percentage of non native alleles in sampled locations might differ from our results (6.6%).

Table of genotypes across 1 mitochondrial and 5 nuclear markers. Samples with non native (=brown trout alleles) are marked red and will not be used in restoration program. f - female, m - male, M - marble trout specific allele, B - brown trout specific allele.

Aquaculture paper

Another day, another paper. Sušnik et al. paper was published as a technical note in Aquaculture (2008, 285, 260-263), A set of nuclear DNA markers diagnostic for marble trout, Salmo marmoratus.

One of the main problem from the native range of marble trout is hybridisation with non native brown trout (Salmo trutta). It is not always easy to distinguish marble trout from brown trout (or from marble × brown trout hybrids) by appearance especially after a successful decade of repopulation project. Mitochondrial DNA and microsatellite markers have their limitations (maternal inheritance for the first, overlapping alleles for the later) so another set of nuclear markers was urgently needed. Markers from this paper were used exactly one year ago and that means that the 2008 results from hybrid zone will be available in a few days.