Pomatomidae: F III A4

Pomatomus saltatrix (Linnaeus, 1766)

Elf or shad


Egg diameter in m

Number of oil globules

Diameter of oil globule in m

Yolk texture

Perivitelline space

Position of oil globule at hatch

Gut length at eye- pigment stage

Myomeres

840-960

1

220-265

segmented

narrow

stern

44% of NL

24

Egg: In this egg the stellate yellow (A) and black pigment spots tend to have a separate distribution, and the black pattern on a white background, is a quick check for this egg (B). The yellow pigment is ventral on the embryo, dorsal on the oil globule (usually forming a halo), and just a few spots on the yolk near the oil globule. Black pigment is lateral on the embryo, forming a border around the head and thorax (B), ventral on the oil globule, and scattered on the yolk ventrally, adjacent to the larva (B). Both egg and oil globule, have a light amber hue on a white background. Incubation time is 30-35 hours (24C).

Larva: The early larva has a distinctive yellow pigment trim to the finfolds (C, D & E), curling into the anus ventrally, where there is a prominent black blotch (D). At 4 days the eyes are pigmented and the yellow pigment has disappeared (F). While still preflexion at 10 days (G), flexion was completed by 14 days (H). At 25 days a complete fin-count was possible (I). C: 1 day, D: 2 days, E: 2 days, F: 4 days, G: 10 days, H: 14 days, I: 25 days (G & H: 23C, I: 25C).

This egg was not successfully reared past 25 days. Three hatched larvae have been sequenced, matching 6 locally collected adults (BOLD).

Shad are summer spawners off Park Rynie, from October to April (blue graph). It was one of the most common eggs, appearing 22nd in Table 3 of the Introductory Notes, but was only seen once in the DHM samples. The annual catch off Park Rynie, shows a regular presence, after an initial peak in 1987 and 1988 (white graph). In the Park Rynie linked samples, the egg showed a slight offshore majority (62%), well below the offshore majority of the two indicator species Argyrosomus japonicus (LIIIA8) and Atractoscion aequidens (LIIA6). See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples

Offshore

Inshore

Eggs

2363

1447

Hits

114

158

During extended transects, shad egg distribution at Park Rynie was as follows;

Distance offshore in km

8

6.5

5

4

2

0.5

Water depth in metres

100

75

60

50

30

15

19 November 1994

0

0

0

0

0

15

26 November 1994

NS

7

6

2

0

0

3 December 1994

NS

NS

NS

0

17

0

21 January 1995

NS

10

5

9

7

2

NS = not sampled.