Clupeidae: F II A1

Sardinops sagax (Jenyns, 1842)

Sardine

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
1320-1610	1	145-170	segmented	Wide	stern	82% of NL	52

Egg description: The egg (A) is instantly recognisable by size , the wide PVS and the small oil globule.  In the reflected light of my microscope, these eggs usually have a red sheen to the chorion (A). Incubation is about 40 hours (21°C).

Larval description: The newly hatched larva has unpigmented eyes and an unformed mouth. Pigmentation is virtually absent. At three days black pigment has consolidated over the gut, the biggest blotch being at the anus, with just a couple of spots post-anus (C). Plate D (preflexion) approximates Brownell’s figure 3, with conspicuous blotches of pigment at the anus and tail, while Plate E (postflexion) approximates his Figure 4.  B: 1 day, C: 3 days, D: 13 days, E: 26 days (21°C).

Rearing was only attempted on one occasion and several larvae were taken to postflexion (E). Two hatched larvae have been sequenced, and match 5 locally collected adults (BOLD).

Linked samples	Offshore	Inshore
Eggs	87172	66497
Hits	101	130

Numerically this was the most common egg in the Park Rynie samples (Introductory Notes, Section 7, Table 3). The unusual shape of the annual spawning graph (blue graph), compared with for example Etrumeus teres (DIIA1), which displays a more normal spawning pattern, is caused by the sudden appearance of sardine shoals off Park Rynie, as they move up the KZN coastline in winter. They are spawning as they pass through; hence the sudden appearance of large numbers of eggs in the plankton. They continue moving north-east into the Durban area before dispersing across the shelf to feed, and continue spawning as long as they remain in good condition. While studying ichthyoplankton off Richards Bay, from 1981 to 2003, sardine eggs were frequently seen in my samples from August to October.

The spring warming of KZN shelf waters, along with possible fish condition loss due to warm water and food constraints, may cause spawning to taper off. High numbers of eggs have, however, been collected in October and November, and as late as the middle of December (blue graph). This probably indicates shoals moving back south, driven out of KZN by the warming coastal water (Connell 1997; 2001, 2010). The egg was seen twice in the DHM samples, both during periods of hectic inshore sardine activity in the Durban area. From about the year 2000, there has been a significant reduction (Connell 2010) in egg numbers (white graph), adding markedly to the overall trend of reduced spawning, possibly due to poor rainfall over the past 8 years (See also Introductory Notes, Section 6: Rainfall and Spawning Intensity, and notes on DIIA1 and LIIA7).The Park Rynie linked samples had 57% of these eggs offshore, suggesting that they are spawning inshore of the spawning aggregations of kob and geelbek ( See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples).