Sparidae: L III B1

Polysteganus undulosus (Regan, 1908)

Seventy-four

 

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

960

1

190

clear

narrow

stern

42% of NL*

25

*eyes unpigmented in this case.

Egg: On 27 October 1991, an angler friend contacted me to say he had caught a ripe-running female of Warner Beach and had placed some eggs in a bucket of seawater. A while later a male was caught and a drop of milt was added to the bucket. Both fish were released, but positively identified as P. undulosus. By the time I received the bucket of seawater, it only contained one hatched larva. Unhatched eggs measured 940µm, with and oil globule of 220µm.

Larva: The early larva was photographed, two days post fertilization, but failed to survive any longer. B: 2 days post-fertilization. The 4-day larva (C), is the first egg-hatched larva confirmed by DNA barcoding. It was collected 28 June 2014.

The seventy-four is one of the species of sparids, indigenous to the south-western Indian Ocean, which migrate north, from the Agulhas Bank, into KZN waters in early winter, where they form spawning aggregations in 60-75m water depth.In the 1950’s and 1960’s, commercial line-fishermen, operating from 20-25m fishing boats of about 75 tonnes, learned to meet the fish off the eastern Cape coast, and to follow the shoals up the coast, along the 60-75 metre depth contours (F.C. (Billy) Clarke pers. comm.). Initially, fish were reproductively inactive, east of Bird Island on the east edge of Algoa Bay (February to April; 34 00 S, 026 45E), but as the shoals moved eastward, gonads developed, until they reached the Park Rynie area, when gonads were large, and ripe running (August to October). Clarke reports that they caught reproductively active fish from Park Rynie in the south-west, to Cape Durnford 28 58S, 032 10E) in the north-east, but also occasionally among the steenbras (Petrus rupestris) off Brazen Head, much further south (32 00S, 029 20E). They also recognised a nursery area in shallower water in the Kei Mouth-Morgans Bay area of the eastern Cape (32 43S, 028 30E), in 30-45 metres, where fish of about 2kg were common. While these notes are anecdotal, they are consistent with known distribution of adults and juveniles. Juvenile seventy-four are virtually unknown in KZN waters, indicating that larvae move south to nursery areas along the eastern Cape coast. Tagging of adult fish has not yet demonstrated movement of adult fish south, after spawning in KZN waters, but local fishing in a variety of water depths has failed to demonstrate a significant presence in KZN waters in summer. At the time of writing, researchers are reporting a modest recovery of this species, after its virtual annihilation, as a commercially exploitable species, up to the 1980s, and its protection from angling, since1998 (Mann, 2007).

Curiously, despite having barcoded about 380 sparid larvae hatched from eggs collected off Park Rynie, only 1 has matched the barcodes of 7 adult Polysteganus undulosus in BOLD.