Reproductive biology

Although studies on reproductive biology of these fishes are far from complete, there is considerable information, which characterizes some families in detail. Overall, they are either gonochorists or sequential hermaphrodites. Gonocho-ristic fishes begin life either as females or males and remain that way their entire lives. Examples include goatfishes, archerfishes, galjoens, sea chubs, jutjaws, sicklefishes, monos, butterflyfishes, the oldwife, boarfishes and armorheads, leaf-fishes, knifejaws, and morwongs. Sequential hermaphrodites change sex. Most Percoidei with this life strategy appear to be protogynous hermaphrodites, in that they begin as females but may change sex and become males. The control of sex change may be social or as a consequence of maturation, and despite detailed research on some groups (i.e., angelfishes and hawkfishes), much remains to be learned about the circumstances that trigger sex change. The status of kelpfishes, sea-carps, and trumpeters is uncertain.

Spawning may occur in monogamous pairs, as sequential pairs within a haremic mating group or spawning aggregation, or promiscuously. Most of these fishes appear to spawn pelagically, the eggs are fertilized in the water column during pair spawning, and there is no parental care. Sneaking (partial fertilization of a pair's eggs by a second male that sneaks up on a rising pair) and group spawning are also possible. Pelagic spawning has been verified for the goatfishes (paired and group spawning), archerfishes, sea chubs, monos (in part), butterflyfishes, angelfishes, the oldwife, hawkfishes, morwongs, and trumpeters. Pelagic spawning is presumed in the galjoens, jutjaws, sicklefishes, boarfishes and armor-heads, knifejaws, kelpfishes, and seacarps. Demersal spawning, in which eggs are scattered on the bottom, placed in nests or bubble nests (a specialized behavior of some leaf-fishes), brooded in holes or caves, or attached to plants, shells, rocks, or some form of structure, may involve parental care to some degree or not at all. Parental care is pronounced, especially in freshwater fishes such as the leaffishes, but is largely absent or minimal in marine fishes. Leaffishes spawn demersally, or in bubble nests, and some monos also have demersal eggs.

There is considerable variability in the temporal patterns of spawning of these fishes. They may spawn only seasonally in relation to latitude and water temperature but not exclu-

Juvenile Leaffish
An Amazon leaffish (Monocirrhus polyacanthus) eating a smaller fish. (Photo by Animals Animals ©M. Gibbs, OSF. Reproduced by permission.)
Angel Fish Life Cycle

The life cycle of a reef fish, the blue angelfish (Holacanthus bermudensis). 1. A pair spirals toward the surface, where eggs are released; 2. Pelagic fertilized egg with single oil droplet; 3. Newly hatched larva, 0.06 in (1.58 mm); 4. 0.10 in (2.5 mm) larva; 5. 0.17 in (4.2 mm) larva; 6. 0.5 in (13 mm) post-larva; 7. Juvenile; 8. Adult. (Illustration by Jacqueline Mahannah)

The life cycle of a reef fish, the blue angelfish (Holacanthus bermudensis). 1. A pair spirals toward the surface, where eggs are released; 2. Pelagic fertilized egg with single oil droplet; 3. Newly hatched larva, 0.06 in (1.58 mm); 4. 0.10 in (2.5 mm) larva; 5. 0.17 in (4.2 mm) larva; 6. 0.5 in (13 mm) post-larva; 7. Juvenile; 8. Adult. (Illustration by Jacqueline Mahannah)

sively. For example, fishes of some families might spawn seasonally over a short period of time once or twice a year regardless of latitude. Others, such as the hawkfishes, may spawn daily at lower latitudes, but seasonally at higher latitudes. Those fishes that produce pelagic eggs and larvae have the potential for relatively long-distance dispersal in marine systems. Demersally spawned eggs usually also hatch to become pelagic larvae, but these may not disperse as far. Of course, there are plenty of exceptions to the rule in both cases.

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Responses

  • eleanor robinson
    How fish reproduce and parental care?
    4 years ago

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