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The FLOPPED project (2019-2023) aimed to investigate the reproduction zones of five billfish species in the Indian Ocean through a comprehensive data collection initiative, including satellite tagging data and biological sampling. Within the framework of this project, 102 satellite tags were deployed around the Indian Ocean on blue marlin (Makaira nigricans; n=43), black marlin (Makaira indica; n=16), striped marlin (Tetrapturus audaxI; n=5), swordfish (Xiphias gladius; n=7), sailfish (Istiophorus platypterus; n=30) and a shortbill spearfish (Tetrapturus angustirostris,n=1). Tagging and biological sampling were originally focused on six study sites, including Reunion, Mayotte, Mauritius (Rodrigues), Seychelles, Sri Lanka and Indonesia. However, due to logistical complications resulting from the global COVID-19 pandemic, we searched for participants from a broader range of sites among our WPB colleagues to maximise the coverage and representativeness of this dataset. Tags were programmed to release from the fish (“pop”) after 3 months and up to 12 months. Four tags are still at sea. The other 96 tags have either popped and reported data (n=75) or have surpassed the programmed time with no data received (n=19). The average duration of tag deployment was about 32% of the programmed time, with a maximum deployment duration of 207 days achieved. Position estimates indicate that most individuals of all species tagged in the south-western Indian Ocean tend to swim to the north-west Indian Ocean off Somalia. Some marlin appeared to have a northeastern trajectory, and one swam directly from Reunion to the southern tip of Madagascar. Marlin and sailfish appear to inhabit the top 200 meters during the day and restrict their depth range to the upper 50-100 m at night. In contrast, swordfish in the southern Indian Ocean appear to inhabit the top 600 meters during the day, and restrict their depth range to the top 200 m at night. While we were able to obtain some data from the longline swordfish tagging experiment, the tagged fish experienced a high rate of mortality, likely due to extended time on the line.
