Most marine fish (and invertebrates) have a complex life cycle that involves a dispersing, planktonic larval stage—the time from egg hatching to juvenile development. These fish generally produce high numbers of eggs with larvae that develop in the open ocean for long periods (weeks to months).
Fish larvae are fascinating animals. They are rarely seen underwater; enormously diverse in their developmental patterns; and physiologically, morphologically, behaviorally, and ecologically different from adult fishes. At hatching, they are generally microscopic (2–4 mm) and undeveloped, living off yolk, and incapable of feeding and swimming against currents. They learn to swim, hunt, and avoid predators as they mature through various stages. Many fish larvae are odd looking and have temporary specializations to survive in the pelagic environment such as freakishly large fins, heads, or eyes, as well as intricate and/or elongated spines, body armor, and/or various pigment patterns. When larvae are close to transitioning into juveniles, they typically use the sun, currents, and reef sounds and smells to find a new home. They make their final approach at night because the reef has many larval predators.
Investigating fish larvae is important. Our understanding of adult fish biology is incomplete without good knowledge of the biology of their larvae. Many of the problems in aquaculture and fisheries management are directly related to the larval stage. Fish larvae can also help us understand our impacts on the ocean, since their survival directly affects the abundance and distribution of adult fishes. It is estimated that less than 10% of fish larvae have been described. Much less have been studied alive.
The Hawaii Larval Fish Project utilizes wild egg collection, hatchery spawning, and larval rearing techniques to study the reproductive patterns, culture requirements, and larval development of marine fish. The project’s objectives are to:
- identify spawning areas and times;
- develop culture protocols;
- show the diverse morphology, pigmentation, and natural color of live marine larvae using photography.
Juvenile fish are raised from hatchery spawned eggs and wild collected eggs. The larvae are cultured in small 10–20 gallon (37–75 L) tanks with microalgae and live foods; including rotifers, ciliates, artemia and wild and cultured copepods.
Fifty-six species from 26 families have been reared through settlement since 2011.
Fish Species Cultured for the Hawaii Larval Fish Project
Baensch, F. 2014. The Hawaii Larval Fish Project. CORAL 11 (2): 64–77. PDF available upon request.