Reproductive biology

Mating strategies, courtship, spawning, and postspawning investment by parents is variable within this group. Freshwater grunters migrate upstream or into the shallows of lakes to spawn, usually during summer months (wet season), although occasionally between autumn and late winter (dry season). Migrations are usually triggered by changes in water temperature, rising water levels in response to seasonal rains, or both. Spawning takes place during daylight or night, may be in groups, and results in the release of eggs that fall onto the substrate. Eggs hatch within 36 hours, and the larvae develop relatively rapidly and disperse soon after. Marine species spawn in the sea and the juveniles migrate into fresh or brackish water.

The diversity of this group dictates that the reproductive biology of these fishes is variable. Age of maturity will vary both between species and within species. An example of variation within species is the nightfish Bostockia porosa. Males of this species mature after their first year, but females are not mature until their second year. Generally, freshwater perci-chthyids spawn during the spring and summer months, and fishes often migrate upstream or downstream to spawning sites. Many of these traditional sites have been obstructed by dams or other barriers to migration, and this has resulted in corresponding declines in population sizes of various species. Reproductive effort may be considerable in these fishes. Members of the genus Coreoperca have male parental care of eggs and larvae. The trout cod (Maccullochella macquariensis) spawns demersal eggs that are large and adhesive onto hard surfaces such as rocks. Parental care is practiced by males of this and other species in this genus. In rivers, care extends until flooding occurs; flooding makes food items, such as insect larvae, available to the postlarval fishes. In the golden perch (Macquaria ambigua), eggs are floating and no care is practiced. Others of this genus scatter eggs that are either pelagic or that sink into interstices within the substrate, and are not cared for. The reproductive biology of other freshwater species is not that well known. Among marine species, members of the genus Howella likely breed in aggregations and scatter pelagic eggs into the water column. Lateolabrax spp. spawn during winter and scatter eggs on deeper rocky reefs of coastal waters. Juveniles may migrate upriver after recruiting from the ocean. The black-fishes mature in two to three years and practice pair spawning during summer months. Females enter a male's nest and lay eggs, usually one batch that varies in number from 20-500, depending upon the species and her size, and these and the subsequent larvae are guarded by the male until they disperse. Pygmy perches are mature in about one year. Depending upon the species, spawning begins late in the austral winter (dry season) and continues through early summer (wet season). Males are territorial, assume bright colors, defend nest sites, and attract females to spawn. Females spawn multiple small batches of eggs every few days during a period that can last for several weeks. The eggs are spawned upon aquatic algae or the substrate within a male's territory. The eggs hatch within two to four days. Most adults of at least one species, Nannatherina bal-stoni, die after spawning. The reproductive biology of the Per-cilidae is not well known. Presumably, spawning also occurs sometime between the austral spring and summer. Eggs are likely demersal and may be guarded by the male.

Kuhlias in freshwater are catadromous, which means that they migrate downstream to spawn in estuaries or the open ocean. Marine species also spawn in the ocean. Tropical species may spawn all year long but seasonal peaks may occur. Spawning behavior is not well known. The spawning mode is pelagic, with spawning in groups. The eggs and larvae are pelagic; larvae of freshwater species migrate into freshwater streams and rivers.

Marine and brackish water centropomids form spawning aggregations in estuaries or reef passes. Lates spp. are catadro-mous and spawn in groups or pairs (not always within groups) in estuaries and nearshore waters. Females are generally larger than males, and two or more males have been observed courting much larger females. Eggs and larvae are pelagic. The reproductive behavior of African lake species of this genus is not well known, but courtship and spawning in groups or pairs, usually after migration to a specific site, with the release of pelagic eggs, is likely. Both Hypoterus macropterus and Psammoperca waigiensis probably migrate to estuaries or inshore waters to spawn pelagic eggs.

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