Start with high-confidence fish & amphibian biology books, then narrow by subgenre or adjacent topics.
Eels
James Prosek
What a Fish Knows
Jonathan Balcombe
Peterson Field Guide to Freshwater Fishes, Second Edition
Lawrence M. Page, Brooks M. Burr
A Field Guide to Coastal Fishes
Valerie A. Kells, Kent Carpenter
A Field Guide to Tropical Reef Fishes of the Indo-pacific
Gerald R. Allen, Roger Swainston
Venomous River
Eli Greenbaum
Valerie A. Kells, Luiz A. Rocha
Alligators
Kent A. Vliet, Wayne Lynch
Shark Biology and Conservation
Daniel C. Abel, R. Dean Grubbs
Ancient Sea Reptiles
Darren Naish
The Shark Handbook: Third Edition
Greg Skomal, Gregory Skomal
Amphibian Species in Environmental Risk Assessment Strategies
Marcelo L Larramendy, Guillermo Eli Liwszyc
