Movement and habitat use of striped marlin Kajikia audax in the Western Indian Ocean

Striped marlin Kajikia audax are globally Near Threatened and their stock in the Indian
Ocean was last assessed as “overfished and subject to overfishing”. Significant gaps in
our understanding of their ecology remain, hampering the efforts of fisheries managers
to ensure stock sustainability. There is a particular lack of fisheries-independent data.
Here we present the results from the first large-scale satellite tracking study of
K. audax in the Indian Ocean. We tagged 49 K. audax with pop-up archival satellitelinked
tags off the Kenyan coast from 2015 to 2019. Individuals were highly mobile,
covering horizontal distances of up to 9187 km over periods ranging up to 183 days,
with a mean daily distance of
48 km. Long-distance movements were recorded to
the east and north of East Africa, with the most distant tracks extending north to the
Arabian Sea and east to near the Maldives. None of the K. audax swam south of East
Africa. Kernel utilization distributions of fish locations demonstrated their shifting seasonal
activity hotspots. Over the sport-fishing season (and tagging period) in Kenya,
from December to March, K. audax typically stayed off the East African coast. After
March, the activity hotspot shifted north to a region close to the Horn of Africa and
Socotra Island. Remotely sensed sea surface temperature and chlorophyll-a maps indicated
that this seasonal movement could be driven by a shift in prey availability. Our
results show the high mobility of K. audax in the Western Indian Ocean, and that individuals
seasonally range between two major fishing areas.