An experimental examination of temperature interactions in the match–mismatch hypothesis for Pacific cod larvae

The match–mismatch hypothesis (MMH) predicts that marine fish larvae will have their highest rate of growth and survival when they overlap with their prey. However, Pacific cod ( Gadus macrocephalus ) and other gadids continue to thrive in the Bering Sea despite delayed prey production resulting from warming and loss of sea ice. In this study, we examined how temperature mediates growth and survival of Pacific cod larvae under varying match–mismatch conditions. Cod larvae were reared at two temperatures (3 °C and 8 °C) and exposed to one of five different food treatments over a 6-week period: (i) high food (HF) (match); (ii) low food (LF); (iii) HF then LF (HF–LF); and (iv) LF then HF (LF–HF) (2–4 mismatch); and (v) no food (NF) (complete mismatch). Results showed that cold environments allow Pacific cod larvae to bridge gaps in prey availability (i.e., timing and magnitude), but negatively impact survival over longer periods. Under warmer conditions, mismatches in prey significantly impacted growth and survival. However, both yolk reserves and compensatory growth mechanisms reduced the severity of mismatches occurring in the first 3 weeks of development. Our results demonstrate a clear need to incorporate the direct effects of temperature on fish larvae in food limitation models.