Captive breeding techniques are usually difficult to implement for highly mobile species such as migratory birds like cranes and fishes like Hilsa.
Conservation biologists define endangered species as one that is likely to become extinct in the near future and is designated as endangered on the IUCN Red List.[8] Conservation seeks to eliminate threats from human activities such as habitat loss and fragmentation, hunting, fishing, pollution, predation, disease, and parasitism.[9]