Heliconia Amazon River Lodge (Ricardo Palma 242, tel. 065/23-1959, www.amazonriverexpeditions.com [1], three days/two nights US$180 pp) is owned by the same group that operates the Acosta and Victoria Regia Hotels in Iquitos.
Heliconia, 80 kilometers downriver from Iquitos [2], is a good midrange resort with a comfortable lodge, rooms with private bath, and well-guided tours. Trips can be arranged and leave the same day.
Heliconia offers excellent river sportfishing programs that start from four days/three nights, at US$545 for 2–4 people, but can be extended as many days as you want. You are required to bring your fishing equipment, or else you can rent it for US$100 per person.
One of the most valued river fish to catch is the tucunaré or peacock bass, but other catches include pacaya (giant wolf fish), silver arowana, and pike cichlid, among others.
Links:
[1] http://www.amazonriverexpeditions.com
[2] http://www.moon.com/destinations/peru/the-amazon/iquitos