- ichthyofauna
- ichthyology
- ichthyoplankton
- identify
- illicium
- imbricate
- immature
- imprint
- inbreeding
- incisiform teeth
- incisor
- incubation
- induction
- inferior
- inferoposterior
- infra-
- infracaudal
- infraspecific
- ingested
- insectivorous
- inshore waters
- integument
- inter-
- interbranchial
- interbreed
- interdorsal
- interhaemal
- internasal
- interocular
- interoperculum
- interorbital
- interpelvic
- interradial membrane
- interspace
- interspecific
- intersperse
- interstitial
- intertidal
- intestine
- intraspecific
- intromittant organ
- inversion
- invertebrate
- iridiscent
- iris
- irradiation
- ISH
- isinglass
- ISNB
- iso-
- isohaline
- Isopoda
- isopropanol
- isotherm
- isthmus
- ISTPM
- iteroparous