Thermal responses and climate change implications of spring and autumn spawning Patagonian squid (Doryteuthis gahi) embryos

Ocean warming affects ectotherm physiological and phenological processes, potentially creating mismatches between early life stages and their prey. Seasonal spawning cohorts are thought to provide flexibility in responding to environmental variability, but if there is seasonal adaptation between these cohorts, then they may respond to ocean warming differently, affecting species resilience and potentially impacting the wider food web. We tested the response to warming of egg masses and paralarvae from two spawning cohorts (autumn and spring) of the Patagonian squid (Doryteuthis gahi). Treated egg masses were exposed to a strict warming regime while control eggs were exposed to air temperature-driven temperature changes. Egg mass respiration estimates demonstrated that higher temperatures resulted in higher respiration rates (metabolic processes), although no additional influence of the rate and magnitude of warming was detected. There were differences in paralarvae size and weight, with the treated autumn cohort containing smaller and lighter paralarvae, which could affect larval duration, especially if early hatching times and smaller hatchlings cause mismatches with their prey or increased predation. This suggests that temperature could influence survival and recruitment success. Greater understanding is required of how temperature changes influence squid phenology (e.g., from timing of egg laying to paralarvae growth and survival) and its likely influence on biomass at adult feeding grounds, which are also important fishing grounds. Further targeted studies could improve the prediction of future impacts on marine food webs, indicating if, for example, changing the timing of fishing seasons, in response to environmental cues would be a useful climate adaptation strategy for the Falkland Islands.