Carangidae: E III A6
Trachurus trachurus (Linnaeus, 1758), Decapterus macarellus (Cuvie,r 1833), D. macrosoma Bleeker, 1851, D. russelli (Ruppell, 1830) et.al.
Scad and maasbanker
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 |
745-890 |
1 |
205-230 |
segmented |
narrow |
bow |
60% of NL |
24 |
Egg: The embryo has 5 pairs of bright white/yellow pigment down the body, and the oil globule is clear with a couple of white/yellow pigment spots, very much like EIIIA5. The oil globule is centrally positioned between the snout and tail of the developing embryo within the egg (A), and the yolk is very conspicuously segmented. Incubation is 25-30 hours.
Larva: The NH larva has the oil globule in the bow, and the basic yellow pigment pattern shown in (B), which moves out into the finfolds over the next 1-2 days (C to F), with the variation in pattern shown in Plate C. Flexion was complete in 13 days (G). B: NH, C: 2 days, C1: 3 days, D: 4 days (not fed), E: 5 days (fed), F: 7 days (fed), G: 13 days (26°C).
Rearing proved quite easy for this egg. The precocious larvae began feeding at 3 days, and showed remarkable growth in just one day, over unfed larvae (D & E). Within 13 days they had undergone flexion, and reached a SL of 8.3mm (G).
The DNA barcode of 11 larvae hatched from these eggs, matched the sequences of 6 adult Indian scad, Decapterus russelli, collected off Park Rynie (BOLD). Another 21 larvae have matched 7 adult slender scad Decapterus macrosoma. Six larvae have matched an adult submitted as D. macarellus, while another 19 larvae have matched 2 adults also submitted as D. macarellus, indicating that one of these is a different species. Lastly, 46 larvae have matched the barcode of 5 adult Trachurus trachurus collected off Park Rynie. Clearly this code (EIIIA6) is a mix of small shoaling carangids that will require some care and patience to separate.
Linked samples |
Offshore |
Inshore |
Eggs |
29471 |
23611 |
Hits |
241 |
387 |
The egg referred to this species code (EIIIA6) was the 6th most common at Park Rynie (Table 3: Introductory Notes). They were found all year round (blue graph), but this might be due to overlapping spawning seasons of the various species. The egg was seen in the DHM samples on only two occasions, in January and February. Annual abundance in Park Rynie samples, showed an increase from 1997 to 2003, and were generally were abundant from about 1997(white graph). The Park Rynie linked samples had 56% offshore, indicating spawning mostly on the shallow shelf, in the 20-30m water depth range. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.