Bycatch, the accidental capture of non-target species in active and discarded fishing gear is the greatest threat to marine mammals worldwide, killing approximately 300,000 whales, dolphins, and seals each year. From an economic perspective, bycatch is a negative externality, defined as an unintended consequence of economic activity that is not reflected in the price of the target catch. Including the true cost of bycatch in fishing activities increases both fishing costs and the market price of seafood. In addition to the costs of reducing marine mammal bycatch requirements in fisheries, the benefits of reducing marine mammal bycatch should also be considered. Research shows that reducing lobster catches to protect North Atlantic right whales can actually increase profits and help sustain the fishery for the future. Reducing marine mammal mortality has the potential to increase revenues not only for ecotourism providers but also for many businesses that indirectly benefit from the tourism industry. Studies estimating the expenditure and value of marine mammal tourism are needed to clearly identify this value and include it in future management discussions. Marine mammals power local businesses and communities, both in educational institutions, public exhibits, and in the wild. In 2016, more than 90 million people in the United States paid an average of $22 admission to visit the Association of Zoos and Aquariums-certified facilities that house marine mammals. In just one year, about $2 billion was spent and about 15,000 full-time jobs were created. This reflects the value of being able to see and learn about U.S. marine mammals. Marine ecotourism has also emerged as a profitable industry, now generating more income than aquaculture and fishing combined. In 2012, the whale-watching industry generated approximately $2 billion in revenue and supported approximately 13,000 jobs worldwide. According to one study, more than 1.3 million people in the Southern Hemisphere spend $12 million a year on tickets to visit fin colonies and reserves. The Marine Mammal Watching Company offers daily tours along the US coast and around the world, with prices starting at US$250 a day to see humpback whales in Tonga and US$230 a day to see gray whales in Baja California, Mexico. As such, ecotourism can become an important part of the coastal economy, providing long-term employment and income sources for local communities while promoting public awareness of marine wildlife. However, observations of marine mammals can also have unintended ecological impacts on certain species and may require management measures. For example, commercial whale-watching boats in the Salish Sea are known to disrupt both the presence and noise of the endangered southern killer whale (SRKW). The SRKW changes its behavior and vocalizations in response to the presence of ships. To reduce the impact of vessels on her SRKW, the NMFS Commission recently recommended that all observations of her SRKW "on the water" be suspended until a permitting regime is in place. The committee also called on NMFS to limit the number of ships circling groups of SRKWs, the speed of the ships, and the time of the ships. The International Whaling Commission has also produced a Digital Whale Watching Handbook to ensure best practices are applied to marine mammal-watching trips around the world. Intended to be an evolving resource for managers, regulators, and industry operators, this handbook has been translated into several languages, with more to come.