By Aleksei Morozov

Some humans say I look like salmon, but we’re not related, even though my scientific name, Salminus brasiliensis, translates from Latin as “Brazilian salmon”. Unlike my namesake, I prefer the warm waters, and am one of the top predators in South America’s tropical rivers, which is why they sometimes call me the “river tiger”. My English name is what they call a tautology: in Spanish, “dorado” means “golden”, so there’s not much sense in adding an adjective with the same meaning. But I guess people just wanted to make me sound different from the saltwater dolphinfish (mahi-mahi). I am golden dorado.

Not Only Golden: Golden Dorado’s Appearance 

Once you’ve seen me, even only in a photo or a video, you will always know me – not in the least by my shimmering scales that can mesmerize any onlooker. Some of us are bright golden, while others may be rather yellowish, platinum, or even orange, but invariably good-looking. My body is robust, with muscles thoroughly trained, to deal with the strong currents of the rivers I inhabit. Its elongated shape, in the eyes of many Europeans, resembles that of a salmon.

Most of us, when mature, weigh between 3 to 10 kilograms, but exceptional specimens can reach lengths of up to 1.3 meters and tip the scales at 34 kilograms. Or should I say “speci-women”? As with many fish species, our females tend to grow significantly larger than male golden dorados. And if you open the mouth in my large head, the powerful jaws lined with sharp teeth will leave no doubt of my predatory feeding habits. 

Find Me Where Conquistadores Looked for Gold: Habitat and Distribution

I am native to the warm freshwater systems of southern Brazil, Paraguay, Uruguay, Bolivia, and northern Argentina. My preferred habitat are the expansive river basins such as the Paraná, Paraguay, Uruguay, and Mamoré. These rivers are characterized by their dynamic currents, and I am well adapted to living in these diverse, fast-flowing underwater terrains. In the rivers, look for me around rocks, sunken logs, and other structures that create significant turbulence that confuses my prey and make it easier for me to strike and grab it. 

A Sudden Burst of Speed: Golden Dorado’s Feeding Behavior

I am the apex predator, which means even as small fry we feel on insects and other smaller fish. As we mature, we graduate to piscivorous diet, catching and eating even bigger prey fish. Our favorite is the streaked prochilod (Prochilodus lineatus), a schooling fish that also undertakes migratory journeys. But if a chance to diversify our diet with a rodent, lizard, or bird presents itself, we’re not going to miss it. 

We are very active predators; even if we’re often hanging around structures, we aren’t simply waiting in ambush for the prey. “Lurking” is perhaps the most accurate word. Once we detect the prey within striking range, we don’t lose a split second – a sudden burst of speed, and as often as not our formidable teeth sunk into the unfortunate’s body. With our agility, which enables us to perform not only acrobatic tricks under water but also spectacular aerial displays, our prey doesn’t really have a chance. 

A Long Journey up the River: Reproductive Cycle

Our reproductive habits are another area where we bear some similarity with the salmon. Each year, we embark on a spectacular upstream migration, which spans for up to 700 miles (1000 km.) to reach our spawning grounds, typically located in the upper reaches of river systems. Spawning occurs between late October and January, and is triggered by specific river conditions and elevated temperatures. 

We do not form monogamous pairs during spawning, as some other species might. A female golden dorados is followed by several males. The female then releases her eggs into the current, where they are externally fertilized by the attending males. This strategy increases genetic diversity and enhances the survival prospects of the offspring. And, unlike some salmon species, we survive the spawning. 

A golden dorado hatches within a day after the eggs have been laid, and the egg yolk will last for only another day. Then we start hunting plankton, and anything else that can fit in our mouth. As juveniles, not yet 30 centimeters long, we display aggressive mimicry, passing ourselves for species like Brycon hilarii. That helps us both to avoid predators and we stalk and stealthily approach smaller prey.

We reach maturity at about 2 years, and can live up to 15. By the way, you can estimate the age of a fish you caught from the size of the scales and the growth rings on them. Just mind that some scales may be regenerated later in life, so for age determination look for the biggest and most regular looking scales. 

How to Catch a Golden Dorado

Archaeological evidence is scarce, but the Pre-Columbian societies surely couldn’t miss such a valuable food resource as our species. It’s in the XX century, however, that fishing after me has become not only a commercial activity, but a recreational affair, and became something of a cult status. Each year thousands of tourists come to my habitat range, mostly in Argentina, to try and land one of my kind. This is a challenge, though. 

Fishing from the shore is possible, especially in the upper Paraná, but in the Mesopotamia region and near Buenos Aires you will probably need a boat to reach the sweet golden dorado spots. We feed all through the days, and don’t mind warm water – in fact, often the warmer it is, the better we bite. Fishing usually peaks in the mid-day, and the activity often drops as day draws to an end – except for that golden hour just after the sunset when the river suddenly bursts out in life.

Spinning or Fly-Fishing? 

There is an ethical dilemma that stands for any British, European, or North American angling aficionado: We golden dorados resemble salmon so much that it seems the only way a self-respecting angler can try at us is on the fly. We would take the fly, though we do not usually feed on insects as adults. So, when you do, it’s not out of hunger, but out of territory protection behavior. Don’t try to have your fly imitate any food. Think big, bright-colored flies, with eyes and long tails, that provoke aggression.

In many locations and in many cases, spinning may be a more efficient strategy to land a trophy golden dorado. Large oversized crankers are the first choice of most guides, but a variety of lures will work well, including poppers. Medium to fast intermittent retrieve seems to work best. Whether you be spinning or fly fishing, cast around structures where we lurk. To identify these structures, local knowledge is essential, which is why it’s best to book a guided fishing trip if you want to land one of our kind. 

If you’re desperate and unsuccessful, baitcasting with live bait, usually one of the local eel species, will usually do the trick. Whatever way you choose, steel leaders are essential to deal with our big, sharp teeth. 

After the Bite 

Our mouths are hard, so you will have to set the hook quickly and firmly as soon as we take the lure or fly. Then all hell breaks loose. We use all our strength – and we are very strong! – to get off the hook, and will use every dirty trick in the book to do so. Our tour de force is the acrobatic leap into the air – a burst of silver and golden sparkles that leaves many an angler gaping their mouth in awe. If the hook hasn’t been set properly, that’s where the lure or fly leaves our mouth and we disappear into the murky waters of the Paraná, Uruguay or Pilcomayo. If it doesn’t, we’ll head for cover. All in all, an angler will be on for a few minutes of uninterrupted fight, and will need to keep the line tight if he or she is to get to land their golden reward. 

Mind Conservation

Even though our distribution range covers a lot of territory, in some locations we face significant threats. Commercial overfishing is a big part of the problem, but not the biggest challenge. Habitat degradation is especially harmful. When people build dams, they obstruct our migratory routes, that we need to reach our spawning grounds. It’s essential that dams be equipped with fishing ladders, although we are often reluctant to use them. This has led to population declines in certain regions. In response, countries like Paraguay have implemented fishing bans to allow stocks to recover. Additionally, conservation initiatives promoting catch-and-release practices and habitat restoration are gaining momentum.

Planning a Trip

Gold has ever had an irresistible allure on humans, and my golden scales are no exception. In Argentina, the annual “Festival de la Pesca del Dorado” celebrates our species, fish, drawing anglers from around the world to participate in sport fishing competitions. Our reputation for fierce fighting and acrobatic displays makes us a coveted catch, contributing to local economies through eco-tourism and reinforcing the cultural bond between communities and their aquatic heritage.

Many anglers believe us to be one of the best game fish in the world. One of the reasons for this is that we readily take the bait – it’s landing us that is the problem. Bite, loss, bite, loss – fishing for us is usually never ending action and excitement, a succession of successes and disappointments that leaves no angler’s heart cold.

Argentina is the most popular destination for golden dorado fishing. Guided trips are available even in Buenos Aires, the capital, but for better action you should go north, to Entre Ríos or Corrientes provinces. There is a strong recreational fishing industry there, with comfortable lodges that offer both gourmet cuisine and experienced guides who know the river like the back of their hand. 

Other countries within our distribution range, like southern Brazil or Bolivia also offer good fishing, and they say most record golden dorado catches recently come from Uruguay. Going after us may not be the cheapest trip of your life – guided days start from $400 and a 3-4 day stay at a lodge will cost you $2,500-$3,000. But hey, gold has never been cheap!   

Main image credit: Frontera Wingshooting

Next in “Life History of a Fish”

Life History of a Fish: Northern Red Snapper

By Scotty Kyle

I am one of the largest snappers and make up over half the biomass of snapper caught commercially and for sport. Humans admire me for my fighting spirit, cunning nature, and – unfortunately for me – delicious flesh, which many say is among the best-tasting fish in the ocean. I am well known to to experienced sport anglers around the Gulf of Mexico and the southern parts of the U.S. East Coast. Biologists know me as Lutjanus campechanus, and among anglers, depending on their region and background, I am known as huachinango, mero, or, more commonly, as northern red snapper. CONTINUE READING