Global review of jellyfish monitoring programs to design fit-for-purpose approaches

Jellyfish provide essential ecosystem services and some are commercially valuable but, when abundant, they can negatively impact human health and enterprise. Long-term monitoring of jellyfish populations is needed to better understand their population dynamics and potentially mitigate their impacts. We reviewed jellyfish monitoring programs worldwide to 1) identify how, where, and which types of jellyfish are monitored, the spatial scales and durations of the programs, and the types of data collected, and 2) develop a guide for designing fit-for-purpose jellyfish monitoring programs. The 95 programs identified focused primarily on Scyphozoa and Hydrozoa taxa and were categorised as plankton surveys, fisheries surveys, citizen science, Ships of Opportunity, beach stranding surveys, dock counts, and sting records. There was a geographic bias towards monitoring jellyfish in Europe, the United States, Asia, and Australia, and citizen science programs were heavily concentrated in the Mediterranean Sea. The spatial scales of the programs encompassed point source (e.g. dock counts) to 300,000 km² and 82 % of programs had monitored jellyfish for >10 years. Most programs (76 %) collected quantitative data. To design fit-for-purpose jellyfish monitoring programs, researchers and managers need to balance the requirement to collect data at spatial and temporal scales appropriate for addressing their research questions, with the logistical constraints associated with managing and paying for the program in the long-term.