Another RARE can of worms - Argentinian Big Head Dorado

[FlatFishLeo]

Subscribed, I have a Wild Caught one from Uruguay that ABarloti brought me, it's about 7-8" now. I'll try to get pics?

FYI: he's my official Festae Fry Runt Eater!

Sent from my iPhone using MonsterAquariaNetwork app

 

[Chicxulub]

What'cha guys think about mine? Normal ones that are imported or different?


When I first got it:

(awesome picture)

Now:

(awesome picture)

(awesome picture)

(awesome picture)

(awesome picture)

DB ~ Just a tip for taking pictures of these always moving powerhouses. Put a high flow power head up against the front glass so the current runs parallel with it. They will swim into the current and hover right there up against the front glass. Works like a charm.

VERY nice Dorado, Peanut.

How big is he now?

I think yours is the normally imported variant. When comparing yours to the Argentine that DB bought from Wes, it strikes me that their heads are different. To borrow an arowana term, it seems like the profile of the Argentinian's head is more of a bullet head, while the normal imports have more of a spoon-head-ish profile relative to the Argentine fish..

I'm gonna see what I can find as far as literature on these fish soon. Unless I'm busy with actual work, I'm probably gonna research this at work tomorrow night. LOL

 

[djaalix]

Lol! +1 for the impossibility to take pics of Dorado's ..... damn things never stop swimming! Hahaha, although I do agree if you catch them in a strong current they will just hang there, for a second or 2 at least!

Sent from my DROID RAZR using MonsterAquariaNetwork App

 

[dogofwar]

Here's the one that I caught on the Rio Uruguay (big river separating Argentina and Uruguay).

I guess the ones on the Argentina half of the river have bigger, less-bullet-shaped heads, right?

The dude fishing behind us was clearly Argentinian...

Matt

 

[FlatFishLeo]

I'll remember to pack my Borat Thong next year Matt!


Sent from my iPhone using MonsterAquariaNetwork app

 

[DB junkie]

A lot easier to get pics of the bigger ones then it is the lil guy.

*Note- the pair in the pics remained in this condition for a whopping 36 hours.... They had to be split up again.

I'll see if I can get the exact river the Argies came from......

Maybe they are all the same....... Wouldn't be the first time I've been wrong, definitely won't be the last..... But after raising several, I'm still sticking with the new lil guy's different.

 

[DB junkie]

Here's the one that I caught on the Rio Uruguay (big river separating Argentina and Uruguay).

I guess the ones on the Argentina half of the river have bigger, less-bullet-shaped heads, right?

The dude fishing behind us was clearly Argentinian...

Matt

View attachment 897291View attachment 897292View attachment 897293

So do you think these "big headed Argentinians" are just the same old Dorado? Can you elaborate?

How big is that one in the pics? 14-15"?

 

[Chicxulub]

So do you think these "big headed Argentinians" are just the same old Dorado? Can you elaborate?

How big is that one in the pics? 14-15"?

I know this isn't directed at me, but this is one hypothesis I'm exploring.

An explanation to this could be the trophic level of the Dorados in either ecosystem. In the Argentine waters, a Dorado may be an apex predator that is at the highest trophic level in its environment. This race of Dorados would be adapted to a macropredatory lifestyle that would include eating other large fish. This would require a bigger head to support bigger jaws. This would also allow the fish to grow larger as they're not being supressed by any other predator.

It is possible that the small headed Brazilian fish are, while the same species, a different race that is occupying a mesopredator spot in the ecosystem. This would be an organism that occupies the second or third trophic tier and is prey for a different apex predator. What it could be supressing the Dorado in the Amazon basin I don't know off hand; filamentosum, armatus, jau, aimara, pick a predator lol

You can find artificially created examples of this effect in America in lakes in the northern states. In many places SMB have been artificially introduced to lakes for the purpose of fishing. The SMB, who are more proficient predators, out compete the native lake trout as the apex predator which suppresses the lake trout. The trout go from a primarily piscivorous diet to one that includes largely invertebrate forage and some smaller fish. Smaller trout also become a key prey item for the bass. Because of this competition, the trout don't get as large and they're not as aggressive and predatory. Once the SMB are removed, the trout once again manage to occupy the top trophic spot and grow huge.

The same principle is possible with the Dorados.

I've had a long, rough couple of days. I'm off to bed. lol

 

[Peanut_Power]

Chicx ~ Hes about 8", maybe. I just moved him over to the 300gal last week, so I imagine some more crazy growth soon.

Another thought on the dorados, I'm not familiar with the environment where each are coming from. If the ones from Brazil are largely farm raised, wouldn't that mean that they are raised in large ponds or sections of slow moving water that are netted off? Where as the ones from Argentina are wild, living in faster flowing, perhaps even turbulent waters?

I've noticed, in my own experiences, fish that are raised in tanks with high turbidity and current are more robust, thicker bodied than those that are raised in tanks with little to no current. So perhaps the Argentinian ones are more robust due to the actual environment they are living in, as well as the points that Chicxs hit on about being the apex predator.

 

[DB junkie]

Where did yours come from Peanut???

Maybe just a locale thing? Look at Black Diamonds vs Leos. Same fish, different river, ones 3 fold the price, and 3 times as nice. People still to this day argue about the "traits" needed for a Leo to be considered BD, but when you see them both the differences are plain as day. In all reality it's the river they come from -Sao Felix that makes them what they are.