Zoetis Inc., the world’s largest manufacturer of animal drugs and vaccines, is entering the fish sector with the $765 million acquisition of Norway-based Pharmaq. The purchase of the aquaculture drug maker from the investment firm Permira is expected to close by Nov. 10. “Pharmaq strengthens our core livestock business by providing market leadership in aquatic health and a strong late-stage pipeline,” said Juan Ramón Alaix, CEO of Florham Park, N.J.-based Zoetis. Pharmaq’s product line includes the vaccine Alpha Ject and the parasiticide Alpha Max. The Zoetis aquatic medicine footprint has been tiny. The company offers only the livestock antibiotic Terramycin/LA for use in fish outside the United States, a company spokeswoman said. Pharmaq, a leader in farmed fish vaccines, had sales of $80 million in 2014, or less than 2 percent of Zoetis’ $4.8 billion in revenue. Zoetis employs 10,000 people, compared with Pharmaq’s 200. Pharmaq will enjoy a high level of independence, said Alejandro Bernal, Zoetis’ executive vice president of strategy, commercial and business development. “To ensure its continued success, the Pharmaq business will run largely as a stand-alone operation within Zoetis and maintain its focus on critical customer needs and R&D milestones,” Bernal said. Joining Zoetis will help Pharmaq grow, CEO Morten Nordstad said. “With Zoetis’ global footprint, we can deliver greater value to more customers around the world and accelerate our geographic expansion plans,” Nordstad said. The aquaculture health products market was valued at $400 million in 2014, according to Zoetis.