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The importance of mucus produced by jellyfish species remains as understudied as their feeding behavior. Here, we study medusae under captivity, ascertain the role of mucus, and describe its feeding behavior. Between February and March 2019, live adult cannonball jellyfish, Stomolophus sp. 2, were collected in Las Guásimas Bay (Gulf of California, Mexico) and were offered fish eggs, mollusk "D" larvae, or Artemia nauplii in 4-day trials. Descriptions of feeding structures were provided for S. sp. 2. Digitata adhere food and scapulets fragment them, which, driven by water flow, pass via transport channels to the esophagus and the gastrovascular chamber where food is digested. Due to stress by handling, medusae produced mucus and water, lost feeding structures, and decreased in size. Based on our observations and a thorough literature review, we conclude that the production of mucus in S. sp. 2 plays several roles, facilitating capture and packing of prey, acting as a defense mechanism, and facilitating sexual reproduction; the latter improves the likelihood of a population persisting in the long run, because fertilized oocytes in mucus transform to planulae, settle, and transform into asexually reproducing polyps. Polyps live longer than the other life stages and are more resistant to adverse environmental conditions than the medusoid sexual stage. [ABSTRACT FROM AUTHOR]

The trajectory of the cannonball jellyfish (Stomolophus sp. 2) fishery in the central portion of Mexico's Gulf of California is an all too familiar one, consisting of exploration, rapid development, and, as of now, subsequent collapse. As all of the product is exported to markets overseas, buyers have little incentive to conserve local stocks, with jellyfish now exhibiting a global-scale sequential exploitation experienced by many other marine resources. While historical data gaps are often used as excuses for overexploitation after the fact, the emergence of this modern fishery was accompanied by relatively broad research interest; however, recommendations based on sound science were not followed. The resultant paucity of policy goals, regulation, cooperation, compliance, and enforcement has resulted in the mismanagement of a potentially lucrative fishery for future generations. There are always myriad challenges when attempting to manage a nascent fishery with high uncertainty, particularly in a developing country, and this case further highlights the importance of taking a precautionary approach to emerging resource extraction. Multiple prior experiences with similar outcomes should behoove regulators and managers to exhibit extra caution, and yet, sustainability and forethought still appear to be secondary to short-term profits and employment support. Nonetheless, it is perhaps not too late for cannonball jellyfish fisheries in the Gulf of California, and there are opportunities to implement management strategies that promote collaboration, research, and sustainability. This fishery requires a new management regime that embraces adaptive co-management in order to provide benefits to locals, both now and in the future. • Jellyfish are targeted for food exports in Mexico's Gulf of California. • Catches for one of the targeted species have declined, possibly due to overfishing. • Management challenges are complex due to natural and social factors. • Future strategies should include stakeholder collaboration and adaptive co-management. [ABSTRACT FROM AUTHOR]