Sciaenidae: L III E4A

Johnius dussumieri (Cuvier, 1830).

Small kob

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
815-890	1	190-230	clear	narrow	stern	35% of NL	24

Egg: The dense, yellow pigment all over the embryo and oil globule, is very like kob (LIIIA8), and LIIIE3. Black pigment is light and “stringy”, mostly dorsal on the embryo.  Incubation was not reliably measured, since the eggs were transported by road for several hours, when temperature was not controlled. An estimate would be 25-30 hours.

Larva: The 1-day larva (B) also has a strong resemblance to kob, except for the presence of a line of stellate black pigment spots in the dorsal finfold (B1; black arrows). B: 1 day (24°C).

This egg has not been seen off Park Rynie; neither was it collected in the Durban Harbour mouth. And although I did not record any sciaenid eggs in St Lucia estuary in 1994 (Connell, 1996), a subsequent sample collected at Charters Creek on 5 September 1995, yielded 27 eggs, shown above (A), which I tentatively assigned to J. dussumieri. More recently, on 27 October 2005, a surface plankton net hauled at the mouth (closed), yielded another 3 eggs of this species. The mouth had been closed since June 2002 (Cyrus et al 2004), and since that time the only sciaenid that had been recorded in the lake,was J. dussumieri. The extensive survey of Cyrus et al (2004) in December 2004, yielded 233 J. dussumieri in the size range of 70-290mm SL, strong evidence that the species was spawning in the system at the time, and the larvae were surviving. A gravid female was collected in a gillnet in the Narrows in December 2005 (Caroline Fox, pers. comm.), and our sampling during October 2005, yielded a juvenile of 123mm SL, in the Narrows. In view of all this evidence, this egg can confidently be assigned to J. dussumieri.