RV Investigator Voyage IN2019_V03 Diversity and abundance of mesopelagic fishes along 110°E, south-east Indian Ocean for the 2nd Indian Ocean Expedition (IIOE-2).

Samples were obtained from the RV Investigator from 14 May - June 5, 2019 as part of the 2nd Indian Ocean Expedition (IIOE-2). A total of 20 stations (90 nautical miles apart) from 39.5 deg south to 11.5 deg S along the 110 ?E meridian was sampled during both day and night. The samples were obtained by means of hauls using a EZ multi-net with a 1 m2 mouth area and eight operating nets (500 µm mesh). It was sent down to 500 m depth and oblique hauls discriminating the following depth strata of the water column were taken as the net was retrieved: 500-400, 400-300, 300-200, 200-150, 150-100, 100-50, 50 - 5 m. Each stratum was sampled for about 10 min and the volume of water filtered was obtained via use of an electronically recording flowmeter (mean volume: 486.5 m3). In summary, 273 discrete stratum hauls, covering the upper 500 m of the water column, were made along the 110 deg E transect in the Indian Ocean. After sorting and identification of fish specimens on board, samples were preserved in 10% buffered formalin with borax for later inspection in the laboratory.