1a. Ventral keel long, extending anterior to pelvic fins from anus to isthmus; body coloration silver or blue-silver.
silver carp
Hypophthalmichthys molitrix

1b. Ventral keel short, extending from anus to between bases of pelvic fins; body coloration silver or blue-silver with scattered, irregularly shaped dark blotches.
bighead carp
Hypophthalmichthys nobilis