Sparidae: L III E3A

Acanthopagrus vagus (Peters, 1852)

Riverbream

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
720-770	1	190-220	clear	narrow	stern	35% of NL	24

Egg: The characteristic mustard yellow pigment colour, the pattern of 4 spots in the head,  the dense cluster post-anus and  the halo of yellow on the oil globule, make the late stage egg and newly hatched larva distinctive (A & B, although the colour of B is too yellow). Eggs hatch in about 26 hours (22°C).

Larva: The three mustard yellow patches of the 2 day larva is distinctive (C), but by 4 days this pigment has disappeared (D).  Flexion was completed by 19 days (F). B: 1 day, C: 2 days, D: 4 days, E: 15 days, F: 19 days, G&G1: 28 days (21-22⁰C).

The larva was difficult to rear, was not taken past 28 days, and these appear stunted (G & G1 above), compared to other sparids reared in this study (S. salpa , D. capensis , R. sarba , C. crenidens). Three hatched larvae have been barcoded, and match 6 locally collected adults, confirmed as A. vagus (P Heemstra, pers. comm.)  A single adult Acanthopagrus berda,collected from Durban harbour, has also been barcoded (BOLD reference).

This was the most common egg in the DHM samples (Introductory notes, Section 7, Table 2), and showed a classic winter spawning peak in July and August, although they start spawning as early as March (green graph). The egg has only been seen in low numbers in the Park Rynie samples (Note the low scale of the Park Rynie graph, as the highest number found in a coastal sample was only 4 eggs). At Park Rynie, they were only detected from 1994 onwards, but both eggs and larvae are sufficiently different to suggest they were not overlooked. Their rarity in the offshore samples, is probably influenced by the absence of major estuaries near Park Rynie, since adults of this species are confined to estuaries and Durban Harbour. The density of A. vagus eggs in the Durban Harbour samples highlights the importance of its sheltered environment for this species. Durban Harbour appears to hold the key stock on the KZN coast south of Richards Bay, emphasising the importance of maintaining the ecological function of this important system (see also Crenidens crenidens).