Which is a good algorithm to recognize flora, fauna.
I am looking for what kind of pattern should i go for Ocean fauna such as given in this image.
I tried with crop image of one of them and trained it till stage 20 opencv cascade classifier but no luck.
You're going to need a LOT more than one example. Try cropping out each one from that image and training with that whole set, along with flips, mirrors, and rotations. That might, might, get you close. Although the fact that there's only one lighting condition will hurt. So really, you need about a dozen images like that in different lighting and with negative examples too. Good Luck, it's not an easy problem.