Korean Journal of Fisheries and Aquatic Sciences (한국수산과학회지)

The Korean Society of Fisheries and Aquatic Science (한국수산과학회)
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Changes in the Specific Gravity of Pacific Cod Gadus macrocephalus, During the Early Life Stages

대구(Gadus macrocephalus)의 초기 발생시기의 비중변화

  • Lee, Hwa Hyun (Institute of Geomatics, Pukyong National University)
  • 이화현 (부경대학교 지오메틱연구소)
  • Received : 2018.06.04
  • Accepted : 2018.06.22
  • Published : 2018.06.30
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Abstract

The Pacific cod Gadus macrocepahlus, lays demersal eggs and the hatching larvae rise toward the surface layer of the ocean to feed. The change in the specific gravity of eggs and larvae was investigated to examine their vertical distribution and movement in the water column. The specific gravities of fertilized eggs and various size classes of larvae were measured using a density gradient apparatus. In total, the instantaneous specific gravity of 146 eggs and 225 larvae were measured. To prevent any disturbance in the gradient water column due to larval movement, 0.004% MS222 was used for anesthesia. Due to their high specific gravity, eggs spawned were deposited over the sea-bed of the spawning ground. The specific gravity of hatching larvae decreased abruptly. However, Pacific cod larvae still had a comparatively high specific gravity at hatching ($1.03655{\pm}0.00146g/cm3$, n=4, mean SL=3.62 mm) and their specific gravities tended to decrease as they grew. The specific gravity stabilized 6 days after hatching ($1.02590{\pm}0.00212g/cm3$, n=15, mean SL=4.67 mm) and the cod larvae were eventually able to float in the water column.

Keywords

References

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