Vertical and horizontal movement patterns of scyphozoan jellyfish in a fjord-like estuary

Despite their important functional role in marine ecosystems, we lack much information about jellyfish, including basic research on their swimming behavior. Here we used acoustic telemetry to obtain detailed behavioral data on 2 scyphozoans, lion’s mane jellyfishCyanea capillataand fried-egg jellyfishPhacellophora camtschatica, in Hood Canal, Puget Sound, Washington, USA. Individual variation was high in both the short-term (hours) and long-term (days) data, although several patterns of behavior emerged. Lion’s mane jellyfish performed diel vertical migrations over the longer time period, but their depth did not vary with tidal stage. Additionally, horizontal swimming speeds varied with diel period and tidal stage for both lion’s mane and fried-egg jellyfish. Lion’s mane jellyfish swam faster during the night than day, whereas fried-egg jellyfish swam faster during the day. Both species had the highest swimming rates during flood tides. Jellyfish clearly exhibited active swimming behaviors and were not passively planktonic. Net and cumulative distances traveled suggest that Hood Canal may be a sink for jellyfish, potentially exacerbating effects of population blooms on the ecosystem. Our findings provide mixed support for previous studies reporting diel vertical migrations in other jelly fish species, and provide evidence that jellyfish are capable of more advanced swimming behaviors than often thought.