Serranidae: K III A4

Serranus knysnaensis Gilchrist, 1904.

African seabass

Egg diameter in µm	Number of oil globules	Diameter of oil globule in µm	Yolk texture	Perivitelline space	Position of oil globule at hatch	Gut length   at eye- pigment stage	Myomeres
860-960	1	145	clear	fairly narrow	bow	54% of NL	24

Egg: The small size of the oil globule distinguishes these eggs in a sample, except from KIIIB1. A day later, yellow dots form in 9 pairs, nose to tail down the embryo, getting less discrete near the tail (A & B). A couple of yellow spots adorn the clear oil globule. No black pigment is seen at this stage. Incubation is about 35 hours. These eggs are often seen in blastula stage, suggesting early morning spawning.

Larva: The yellow pigment along the body, quickly moves out to the edge of the expanding finfold (C), and the outer finfold edge is rough, almost serrate (D1, arrowed). The 4 day larva develops conspicuous black pigment over the gut, and form rust-coloured patches within the yellow pigment at and above the anus, and midtail (E). B: NH, C: 1 day, D: 3 days, E: 5 days (23°C).

The early larva tends to curl its body when disturbed in the hatching bowl. All attempts to rear it were unsuccessful. Nine larvae hatched from this egg have been sequenced, and they match four adult Serranus knysnaensis collected off Park Rynie, but show a distinct difference from two adult specimens collected on the Tugela Banks, and a similar difference to sequences of 5 adult Serranus novemcinctus from Walters Shoal (BOLD). This egg is easily confused with Zanchus (LIIIA8), but Serranus has a smaller oil globule, usually in the bow of the yolk-sac larva (B & C).

The egg was common off Park Rynie from mid-winter to early summer (blue graph). In the DHM samples, the egg was mostly seen in October (green graph). At Park Rynie, the egg has shown a steady presence, but a slight decrease in the past few years (white graph). In the Park Rynie linked samples, the eggs were marginally more common offshore (55%), indicating another species that is spawning on the shelf, mostly inside the 30m contour. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples	Offshore	Inshore
Eggs	332	267
Hits	126	99