The surubí is a large, powerful fish caught in fast-flowing rivers with structure, so the tackle has to be up to it. Concrete recommendations:

For bottom fishing / drifting with bait:

• Rod: powerful, with medium to medium-fast action and good power (roughly 30-50 lb line class), 1.80 to 2.10 m, with backbone to lift weight off the bottom.
• Reel: a solid baitcaster or a large spinning reel (size 6000-8000), with a strong, progressive drag to withstand runs.
• Line: braid of 0.40 mm and up (approx. 50-80 lb) for its strength and sensitivity; or 0.50-0.60 mm monofilament if you prefer some stretch for cushioning.
• Leader: a section of thick monofilament or fluorocarbon (0.80-1.00 mm) or even flexible wire, to resist abrasion against the hard mouth, the structure, and the bottom.
• Sinker: matched to the current (pear, olive, or bottom sinker with a flag arm), of the weight needed to hold the bait.
• Hooks: strong and good-sized, reinforced O'Shaughnessy or circle types, matched to the size of the bait and the fish.

For spinning / trolling with lures:

• Rod: powerful spinning or baitcasting rod (20-50 lb line class), with a tip action to throw large lures and backbone to fight.
• Reel: spinning 5000-8000 or a robust baitcaster, with a good drag.
• Line: braid 40-65 lb, with a thick fluorocarbon leader (0.70-0.90 mm) or wire to avoid cut-offs.

In every case, the rule is oversize rather than come up short: a surubí of over 20 kg in full current, trying to bury itself in the logs, forgives neither weak tackle nor loose knots. Always check the condition of your line, your knots, and the sharpness of your hooks before each outing.

For the Pacu you need robust gear: it is a fish of great strength that fights near structure, so it's better to be over-equipped than under-equipped. Recommended gear by method:

Bottom / mixed fishing (the most common)

• Rod: medium to medium-heavy action, 1.80 to 2.40 m, with a good reserve of power in the lower section to stop runs and pull the fish out of the logs.
• Reel: a medium-to-large spinning or baitcasting reel, with a good, progressive, reliable drag. A well-set drag is key: not so loose that it reaches the structure, nor so tight that it snaps off.
• Line: braided from 0.20 to 0.40 mm (approx. 20-50 lb) for its low stretch and sensitivity to detect the "testing" bite, or strong monofilament nylon if you prefer some stretch as a shock absorber.
• Leader: abrasion-resistant fluorocarbon of good strength (approx. 30-50 lb), essential because the Pacu has a bony mouth, powerful molars, and tends to head for branches and logs. Strong, very sharp hooks, sized to match the bait.

Fly fishing

• Gear: #7 to #9 lines depending on the expected size and the wind, with a matching rod and good reserve for the fight. A reel with a reliable disc drag.
• Leader/tippet: robust and abrasion-resistant; no fineness, because the fight is hard and there is structure nearby.

Spinning

• Medium-power gear, thin but strong braid, a fluorocarbon leader, and small lures.

General rule: the Pacu does not forgive flimsy gear. Reliable drags, anti-abrasion leaders, and sharp hooks are the difference between telling the story with a photo or telling the one about the one that got away.

Medium tackle with a steel leader. Careful unhooking: the teeth cut.

The gear must measure up to a strong fish that runs, jumps, and lives in current with structure. Specific recommendation:

Spinning (standard setup)

• Rod: spinning rod of 1.80 to 2.10 m, medium to medium-fast action and medium / medium-heavy power, with a good response for setting the hook in a hard mouth.
• Reel: a sturdy spinning reel size 3000 to 4000, with a progressive, reliable drag to hold up to the runs.
• Line: braided line of 20 to 30 lb; it gives sensitivity, low stretch for a solid hookset, and the load capacity for big fish.
• Leader: an anti-cut leader is essential because of the teeth: thin flexible steel (coated steel cable) or heavy fluorocarbon of 40-60 lb. Without it, the dorado cuts the line with a single bite.

For trophy specimens or big rivers: step up to a medium-heavy/heavy rod, a 4000-5000 reel, and 30-40 lb braid, with a steel leader.

Fly fishing

• Rod: #8 to #10, fast, to move large streamers and fight in current.
• Reel: with a good disc drag and backing capacity.
• Line: WF (weight forward) matched to the rod number; in fast water a sinking tip may be advisable.
• Tippet / leader: finish with an anti-cut section of steel or heavy fluorocarbon, just as in spinning.

Key accessories: strong, well-sharpened hooks (ideally barbless if you're going to release), long pliers to unhook without hurting yourself on the teeth, and if you practice catch and release, a knotless/rubber net and gloves to handle the fish carefully.