This is an academic book about the accumulated scientific knowledge on the large Amazon catfishes. The book ranges from highly technical notes of how populations are surveyed to a list of all the different species in the region and their characteristics.
The very interesting fact is the migratory patterns of the different species along different rivers. The general pattern is to reproduce in headwaters, then they travel to the estuary region where they grow and then migrate back to headwaters to feed, grow more (ever larger, 200 pounds or more) and finally reproduce. The study reflects part of the concern over large hydroelectric dams that could interrupt this cycle.
I recommend this book for anyone interested in the finer aspects of Amazon conservation. Though academic, it is readable for the novice as well.