Thermal windows supporting survival of the earliest life stages of Baltic herring (Clupea harengus)

Abstract

Abstract Peck, M. A., Kanstinger, P., Holste, L., and Martin, M. 2012. Thermal windows supporting survival of the earliest life stages of Baltic herring (Clupea harengus). – ICES Journal of Marine Science, 69: 529–536. Projecting climate-driven changes in marine systems will require knowledge on how thermal windows affect the vital rates of key species. To examine the potential, direct effect of climate-driven warming on southwest Baltic herring, we quantified the survival, development, and biochemical condition of embryos (eggs and yolk-sac larvae) at ten temperatures between 2.9 and 21.7°C. Viable hatch was highest from 7 to 13°C, <20% at 2.9°C and 0% at 21.7°C. Between 5 and 19°C, increasing temperature (T) decreased the time to 50% hatch (Ht, h,): Ht = 4461.9 × T − 1.24 (r2 = 0.98, p < 0.0001). Using degree-days [°d = T (°C) × age (d)] could normalize some (but not all) thermal effects. Most hatching occurred 90–120°d post-fertilization, unfed larvae lost 0.33 µg dry mass (DM) °d−1, larvae did not survive >160°d post-hatch. RNA–DNA ratios rapidly decreased between 50 and 80°d post-hatch, whereas DNA ×DM−1 increased throughout the yolk-sac phase and likely provides a stronger indicator of irreversible starvation. The critical, “mixed feeding” stage is likely 60–100°d post-hatch. The broad thermal tolerance of herring embryos makes “direct”, negative effects of warming unlikely; however, a lack of common methods among studies makes it difficult to project how climate warming will affect embryos of different fish populations and species.