First record of gray rockcod Lepidonotothen squamifrons larvae in the Amundsen Sea, Antarctic: implication for a new spawning ground and early life characteristics

The gray rockcod Lepidonotothen squamifrons is widespread throughout the Antarctic region; however, little is known about its early life information. Highly abundant gray rockcod larvae were collected in the Amundsen Sea polynyas during a zooplankton survey conducted in March 2022. This is the first record of gray rockcod larvae in high abundance found at high latitudes in the Southern Ocean. The otolith microstructure analysis provided more insight into the early life characteristics of gray rockcod. A total of 41 individuals with a standard length of 9.6–15.3 mm were estimated to be 6–11 days. Multiple primordia were recorded in the otolith for the first time. The Gompertz model was well fitted to the age–length data, indicating a mean daily growth rate of 0.66 mm day −1 (SE = 0.35). Larval hatching occurred at a size of 4.08 mm (SE = 3.85) and was concentrated over a short period in early March. Compared to the populations observed at lower latitudes, the gray rockcod in the Amundsen Sea polynyas showed later hatch times, smaller hatch sizes, and faster growth rates. Therefore, we speculate that Amundsen Sea polynyas are potential spawning grounds for gray rockcod. The spatial differences in early life characteristics revealed herein could contribute to our understanding of the life history strategy and adaptation of the gray rockcod.