Using fatty acids and stable isotope analyses to elucidate ontogenetic variations in diet of painted notothen Lepidonotothen larseni during winter at the South Georgia shelf, Antarctic

Fish belonging to the Nototheniidae family are considered to be the most significant members of the Notothenioids family and are essential to the Antarctic marine ecology. However, the trophic dynamics of some unexploited species, including semi-pelagic painted notothen Lepidonotothen larseni, remains unknown. This study used fatty acids (FAs) and stable isotope indicators to examine the shift in diet from early juvenile to adult stages at South Georgia throughout winter in order to improve our understanding of the dietary diversity and trophic niche of L. larseni. Thirty different types of fatty acids were found in the muscular tissues of early juveniles (4.10–4.85 cm) and adults (8.7–14.9 cm), yet there was a notable variation in the composition of FAs between the two groups. FAs including C22:6n3, C22:2n6, C16:1n7, and C20:5n3 were found in high amounts in both early juveniles and adults. Both the δ¹⁵N and δ¹³C values of adults were significantly higher than those of early juveniles, suggesting an ontogenetic shift in L. larseni's diet and trophic niche separation between the two stages of development. Significant separation in marker FAs was also observed between early juveniles and adults. Early juvenile L. larseni primarily fed on pelagic algae or copepods, whereas adults predominantly fed on Antarctic krill (Euphausia superba) on the seafloor and in the water column.