The global importance of mesopelagic fish is increasingly recognised, but they remain relatively poorly studied. This is particularly true in the Southern Ocean, where mesopelagic fishes are both key predators and prey, but where the remote environment makes sampling challenging. Despite this, multiple national Antarctic research programs have undertaken regional sampling of mesopelagic fish over several decades. However, data are dispersed, and sampling methodologies often differ precluding comparisons and limiting synthetic analyses. Here, (...)

The global importance of mesopelagic fish is increasingly recognised, but they remain relatively poorly studied. This is particularly true in the Southern Ocean, where mesopelagic fishes are both key predators and prey, but where the remote environment makes sampling challenging. Despite this, multiple national Antarctic research programs have undertaken regional sampling of mesopelagic fish over several decades. However, data are dispersed, and sampling methodologies often differ precluding comparisons and limiting synthetic analyses. Here, we have collated and standardized existing survey data of mesopelagic fishes into a circumpolar dataset called Myctobase. To date, Myctobase holds 17,491 occurrence and 11,190 abundance records from 4780 net hauls from 72 different research cruises. Data include trait-based information of individuals including standard length, weight and life-stage. Data span across 37 years from 1991 to 2019. Detailed metadata has also been provided for each sampling event including the date, time, position (latitude, longitude, and depth), sampling protocol, net type, net mesh size, tow speed, volume filtered and haul type (routine, target, random). 

The dataset is comprised of three comma-separated files. The first file (event.csv) describes the survey methodology. The second file (groupOccurrence.csv) contains the catch data linked to the survey methodology by an event ID. The final file (individualOccurrence.csv) contains measurements of individuals. Each row contains the event and occurrence ID, which links each measurement to the first and second file. See associated metadata record for definitions and units for each variable in 'definitions.xlsx'.

The final dataset was subject to quality control and validation processes. Entries with ambiguous or incomplete records were identified with a '0' in the column labelled 'validation' (event.csv) and a description of the missing data can be found in the proceeding column labelled 'validationDescription'.

The taxonomic name for each individual was verified against the World Register of Marine Species (http://www.marinespecies.org/).