"This page may contain spoilers for some episodes in the series"
List of Named pets in the anime.
In the manga Renge catches Salt again (supposedly the same crab) in the winter and puts it in an aquarium in her house.
In the manga, Pechi appears to be much smaller, maybe even a different breed.
Flatty-San (ひらたいらさん Hirataira-San?) is the name Renge gave to a bunch of triops shrimp that the girls collected from a river. She keeps them in an aquarium in the school and is the sole caretaker for them. She also keeps an observation journal on them.
Hand to Mouth (その日暮らし Sonohigurashi?) is a cicada that Natsumi lures out of its hole by pouring water into it. Renge calls it "Hand to Mouth"(it's a rather hard word to translate, essentially it means "a carefree existence/living life day-by-day")
Hikarimono Boss (光りもの親方 Hikarimono oyakata?) is a huge common carp that Natsumi catches when the girls go fishing. They bring the carp to Natsumi's and put it in a pond. Later Renge decides to name it "Hikarimono Boss". In a later episode, the carp is referenced, so it is safe to assume that it still lives in the pond at Natsumi's house.