Complex sentence: Lobsters, the seals' preferred food other than fish, have been overfished and competition from other apex predators such as sharks, jacks, and barracudas, leaves little left over for developing pups.
Split into simpler sentences: Lobsters, the seals' preferred food other than fish, have been overfished. Competition from other apex predators such as sharks, jacks, and barracudas, leaves little left over for developing pups.