Effect of incubation temperature on eggs and larvae of lumpfish (Cyclopterus lumpus)

Two batches of lumpfish eggs were incubated at three temperature regimes; 1-Ambient seawater 4-6 °C (cold), 2-Ambient seawater for 10 days followed by a gradual increase to 10 °C (gradient), 3-Constant 10 °C seawater (warm). The eggs incubated in cold water had the highest egg mortality (38.5% ± 15.7) and lowest hatching success (46.1% ± 7.2), while the gradient group regime showed highest hatching success (74.9% ± 4.2). Larvae from the gradient regime showed the most synchronized hatching as hatching started at 280 dd (35 days post fertilization (DPF)) and reached the hatching peak the same day with almost 80% of all larvae hatching. Hatching started at 279 dd (28 DPF) in the warm regime, reached a hatching peak (50% of total hatching) at 3 days post hatch (DPH), and ended at 9 DPH. In the cold temperature group hatcing started at 285 dd (63 DPF) and the hatching peak was reached at 3 DPH. Hatching lasted until 13 DPH. Hatched larvae from the cold regime were longest (6.11 mm) and heaviest (5.55 mg), followed by larvae from the gradient (5.71 mm, 4.88 mg) and warm (5.33 mm, 4.37 mg) regimes respectively. Newly hatched larvae from the warm group had the highest occurrence (34.7%) of body deformities compared to 8.9 and 7.6% in the gradient and cold water groups. Studies of organ and tissue histomorphology of hatched and two weeks old larvae did not reveal obvious developmental differences between the groups at these timepoints.