The present work expands the existing knowledge on M. mola ecology by assessing, for the first time, its abundance (and body size distribution) in the southern waters of Portugal and relating the associated temporal variations with environmental variables. There were significant seasonal differences in abundance, with peaks in spring and autumn and lower values throughout the summer. Ocean sunfish abundance was positively correlated with sea surface temperature and chlorophyll a, indicating that a combination of both temperature and productivity dictates spatial use. Complementarily, the absence of a relationship between abundance and water transparency may reveal a strategy in spatial use favouring a medium-term steady food supply over short-term improved feeding opportunities. Specimens ranged between 31.8 and 230.0 cm (total length), with 98% of all individuals measuring between 31.8 and 59.9 cm. As the vast majority of specimens analysed were immature, seasonal differences in abundance should not be related to spawning.

Mola mola is distributed from temperate to tropical oceans. The scarce reports on the occurrence of the species in the Uruguayan coast were based on incomplete morphological studies on collected specimens that could not properly discard the congeneric Mola ramsayi. This work constitutes confirmation of the occurrence of Mola mola in the coastal area of Uruguay, based on morphological characters of a specimen collected in April 2013. The fish occurred 100 m offshore in the Río de la Plata estuary (at a depth of 5 m), in an area with a water temperature between 19 and 19.5°C. Morphometric data is provided. The specimen is preserved in the Museo Nacional de Historia Natural de Montevideo (Uruguay).

The stomach contents from a killer whale stranded in north-west Ireland were examined. Siphonostomatoid copepods Cecrops latreilli and bones consistent in shape and size with those from the ocean sunfish were found. While observations of free-ranging killer whales predating on sunfish exist from the Gulf of Guinea and the South Pacific, this is the first record for the North Atlantic and the first from stomach content analysis.