Exploring Golden Dorado Habitats: Conservation Research in Argentina's Paraná River and Iberá Wetlands

By: Dr. Andy J. Danylchuk

 

As we left Buenos Aires and began flying north, it quickly became apparent that my pre- trip exploration via Google Earth was deceptive. The caravan banked a bit west as we climbed, almost bisecting the province of Entre Rios on our way to Corrientes. The grand watershed of this region is vast and intricate. Crossing Entre Rios, I could see the Parana River to the west, the Uruguay River to the east, and an expansive delta in between. The meandering rivers, ribbons of side channels, and small to large lagoons made it clear that the watershed of this region is indicate and dynamic.

My goal for this trip was to survey a range of habitats and meet with stakeholders, anglers, guides, other scientists, and government officials to plan out a new research project focused on the movement patterns of Golden Dorado. Currently, collaborators and I at the University of Massachusetts Amherst have a multi-year study underway using genetics and genomics to understand how populations of Golden Dorado are connected (or isolated) across the landscape. We are grateful for funding from the International Game Fish Association for this project, as well as the vast network of anglers, fishing guides, and other scientists for helping to collect fin clips that made this project possible, especially during the pandemic when international travel came to a dead stop. Preliminary data suggests that something interesting is happening in the Parana River and adjacent habitats, and it allows us to develop hypotheses that we can test with a suite of different tools and techniques. Not all tools and techniques are useful for tracking the movements of fish, and tagging for the sake of tagging without a sound plan creates false expectations and can spend precious research dollars unnecessarily.

As the plane began to descend, we got closer and closer to the Middle Parana. The province of Corrientes has the Middle Parana to the west, Upper or Alto Parana to the north, and Uruguay River to the east, with the Ibera Wetlands in between. The Iberá Wetlands alone cover an area of over 850,000 ha and are one of the three primary locations on my two-week exploration to check out golden dorado habitat. Again, all the time I spent on Google Earth and other resources didn’t prepare me for how vast this area is and how Golden Dorado inhabits such a wide range of habitats. Fortunately, I did have some amazing pre-trip guidance from my hosts and collaborators from SET Fly Fishing to at least prepare me for the gear I’d need to battle golden dorado across a range of sizes and habitats. A quick visit to T&T HQ in Greenfield, MA (not far from home) helped build my quiver, including an 8 wt Zone, 9 wt Sextant, and 350-grain Exocett SS.

The first stop on the trip was Itati Lodge, which sits on a section of the Alto Parana that is at points over a mile wide. Depending on rainfall in Brazil and discharge from the dams upstream, there can be huge sand banks to wade, deep-cut shorelines with woody structures, and deep pools rimmed by shallow rocks and big back eddies. The amount of fishable water is immense, and the golden dorado in this region can be big, really big….like over 30 lbs. With the river being relatively low during my visit, we spent a good amount of time intercepting smaller fish in the 5-8 lb range that were hunting sabalo – an abundant forage fish, much like bunker. It was exciting and super informative when it came to mapping out ideas related to the research project and what may or may not be possible, given the scale and scope of this section of the river. Although we didn’t intercept any larger fish during this stop, the current plan was, thankfully, to return to Itati to try again for the last few days of the trip.

Next stop was the Iberá Wetlands – a crazy huge tapestry of narrow channels, wider connections, large lagoons with floating islands, boot-sucking mud, sandy ribbons, tall grasses, and a diverse array of emergent, submerged, and floating plants, all supporting an amazingly diverse community of birds, caiman, capybara, pampas deer, a rainbow of different colored dragonflies, flying and swimming beetles, and of course fish, including piranha and golden dorado. Some parts of this region have been re-wilded, including the reintroduction of jaguars. Searching for golden dorado here was amazing and made up of short to mid-range tactical casts, floating lines, and mouse patterns, and large poppers. It reminded me of a cross between fishing for redfish in the Louisiana Delta and Northern Pike that cruise reed beds in the home waters of my formative years back in Ontario. The difference was when golden dorado struck, and I was reminded where I was. The golden dorado here range in size but are mostly in the 4-8 lb range, although larger fish do lurk in the bigger lagoons. It was hard to leave this location, but there was more to explore.

Next stop was the Isoro Wetlands that sit to the east of the Middle Parana south of the town of Goya. As the road to the lodge turned, I caught a glimpse of the boats on the end of a channel just as a gaucho rode by on his horse. After the first day on the water, it soon became easy to see how the conditions of these wetlands are influenced by the upstream rains that fall (or not) in Brazil along the Parana, as well as north along the Paraguay River that flows into the Parana just north of the city of Corrientes. These wetlands were also very intricate and golden dorado were chasing sabalo along what seemed to be every bank and every turn. Typically, this is a place of numbers not size, unless fishing closer to the main stem of the Middle Parana. The 8 wt Zone was a blast in this environment, and with the crease flies and streamers used to temp the golden dorado to react and destroy.

The last few days of the visit were to give the big waters of the Alto Parana another go and hopefully getting into a beast of a golden dorado. The days prior and even while there were rainy, overcast, and cooler – conditions that the seasoned guides of the Itati Lodge indicate make the golden dorado more active and begin moving more. The scientist in me noted this as a testable hypothesis for the upcoming research, while the angler in me got all giddy inside. On the very last day the wind blew and rain sprinkled, and our very first stop was a set of rocks in sight of the town of Itati. This is where the 350 grain Exocett SS and sinking lines were necessary, as was steady nerves – nerves I apparently didn’t have as I blew a hook set on something that wanted to pull the rod out of my hand. The rest of the day we got into a good number of 3-5 lb golden dorado – a size that the guides told me have been increasing in abundance on this stretch of the river over the past few years. Honestly, this was all nice, but my blown chance early that day was plaguing me. I tried not to let it since I’m generally more about the experience than a trophy, but I really needed to see a larger golden dorado up close. As the daylight faded, our guide Juan cruised past the docks and headed downstream for one last chance at the rocks and one last chance for me on this trip. Maybe it was all the yerba mate and fernet and coke I’d been consuming over the past few weeks, but I felt more in tune with the river than ever. I know this sounds hokey, but there was a weird sense of calm in me when Juan was deploying the trolling motor and getting me into position to cast. The 350 grain Exocett SS was wonderful to cast and to use to manipulate the swing of the fly as it approached the pressure wave ahead of the rocks. My casts were dialed – I’m generally an impatient angler and don’t pause long enough on my back casts, but not this time. Then it happened. A massive tug and then I watched the line rip through the water ahead of several big air leaps. The golden dorado at the end of the line wasn’t a monster, but certainly much bigger than anything else anyone with me had caught over the past few weeks. I then heard Juan say, “enjoy the fight”. We landed the fish on a sandy beach nearby and I was able to keep the fish wet while admiring it – something all fish deserve after they let us battle them. 


My search for a relatively big bar of gold was over and the collective experiences from this trip allowed me to work with my local collaborators to develop our research ideas further – research that will be used to inform conservation and management of golden dorado. One impressive move by the Corrientes government was to ban treble hooks and that all single hooks need to be barbless, and to make golden Dorado catch-and- release only. Still, the rivers are big, wetlands vast, and there is some evidence that golden dorado move among some of the provinces. With that, more science-based evidence is needed to better understand the movement patterns of golden dorado and whether more universal management is needed to conserve such an economically and ecologically important species in the Neotropics of South America.

Photos by: Zento Slinger

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