198: SILLAGINIDAE (SILLAGOS)
Taken in sandy areas by net and on small hooks. Swims in
schools; sometimes skips along the surface when disturbed.
Family No. 199: SCIAENIDAE
by P.C. Heemstra
Kobs
Kobs
Body oblong to slightly elongate, somewhat compressed.
Dorsal fin margin deeply notched before last spine; anterior
part with 9-11 slender spines; rear part with 1 spine and
23-31 soft-rays. Anal fin with 2 spines and 6-9 soft-rays.
Pectoral fin rays 16-22; ventral fins 1,5. Caudal fin truncate,
rounded or rhomboid; branched rays 15. Scales cycloid or
ctenoid, covering head and extending onto soft dorsal, anal
and caudal fins. Lateral line extends to end of caudal fin.
Maxilla mostly concealed when mouth is closed. Two
nostrils on each side of snout. Opercle with 2 flat points
posteriorly. Jaws with rows of small, sharp, conical teeth;
canines present in some species; no teeth on vomer,
palatines or tongue. Branchiostegals 6 or 7; gill membranes
separate, free from isthmus; gills 4, a slit behind the last.
Gasbladder well developed, carrot-shaped, hammershaped, or anchor-shaped, and with various diverticula.
Vertebrae 23-30.
These fishes are also called "croakers" or "drums" because they are able to produce a variety of sounds by means
of muscles attached to the gasbladder. Sciaenids are common in warm coastal waters and estuaries of the world.
Some species attain a large size and are of considerable
economic importance. Many genera and well over 100
species are recognised in this family; we have 9 species in
our waters. Trewavas (1977) has revised the species of the
Indo-West Pacific region. lohnius soldado (Lacepede),
SFSA No. 551, and lohnius belangerii (Cuvier), SFSA No.
549, were reported from Natal by Fowler (1925 and 1935),
but these records were probably based on misidentifications, as neither species occurs in our area.
KEY TO GENERA
la C emarginate (upper and lower rays distinctly longer
than middle ones); no pores on chin; A II,8-9 ............ Atractoscion
Ib C truncate, rounded or sinuous (upper and lower rays not
longer than middle rays); A II ,6-8 ......................................... 2
2a 1 or 2 very large canines at front of both jaws; no pores
or barbel on chin ..................................................... Otolithes
2b No single pair of very prominent canines in jaws; chin pores
present ........................................................................... 3
3a Chin with a short thick barbel, with a pore at its tip;
broad band of villi form teeth on lower jaw; no
gasbladder appendages ............................................. Umbrina
3b Chin barbel absent, or if present, with a pore at front of its base .. 4
616
4a Mouth terminal, oblique; body depth subequal to head length,
3.2-3.6 in SL; 6 distinct pores on chin; gasbladder carrotshaped, without cephalic appendages .................................... 5
4b Mouth subterminal, horizontal; chin pores in a "false
five" pattern (with a median U-shaped groove or dimple
containing 2 tiny hidden pores); gasbladder hammershaped, with first appendage of each side reaching
the head where a lateral branch extends to the lateral
face of the pectoral arch at the junction of cleithrum
and supracleithrum (visible under operculum)
(See 1. dussumieri, p. 618.) ......................................... lohnius
5a P length 27-30% SL and about ~ distance from V
origins to A ......................................................... Atrobucca
5b P 19-22% SL, 0.5-0.7 of distance from V to A origins. Argyrosomus
Genus Argyrosomus Pylaie, 1835
Body depth 25-30% SL. Vertebrae 11 + 14. Gasbladder
carrot-shaped, with 25-35 paired appendages. Trewavas
(1977) erected a separate genus for A. thorpei, but Smith's
(1977) decision to include A. thorpei in Argyrosomus is followed here. Six species; 2 in our area.
KEY TO SPECIES
la Skin at upper end of P base scaly; C truncate;
fins yellow in life .................................................... A. thorpei
Ib Skin at upper end of P base not scaly; C rounded
or sinuate; fins grey or brown in life .................. A. hololepidotus
Kob
199.1 Argyrosomus hololepidotus
(Lacepede, 1801)
PLATE 71
Kob
Labrus hololepidotus Lacepede, 1801: 518, PI. 21, Fig. 2 ("grand Ocean
equatorial"; based on figure from manuscript of Commerson, who,
according to Cuvier, obtained the specimen from Madagascar). lohnius
hololepidotus: Smith, SFSA No. 552*; Smith & Smith, 1966: 43*.
Argyrosomus hololepidotus: Smith, 1977: 566*; Trewavas, 1977: 327*;
van der Elst, 1981: 261 *.
D X+I,26-29; A 11,7; P 17; LL 48-54; developed GR (3-5)+(9-11);
25-35 pairs of gasbladder appendages. Depth 2.9-4.0, head 3.0-3.6 in SL;
eye 5-6, interorbital 4-6 in head. P & V subequal, about 1.5 in head. About
18 enlarged teeth on each side of upper jaw. Longest GR shorter than
longest gill filament. A. regius Asso, 1801 of the northeast Atlantic and
Mediterranean, has only 7 or 8 lower limb GR and 36-42 pairs of gasbladder appendages.
Body silvery; fins grey or brown; black blotch at upper
end of P base more or less distinct. Attains 70 kg and a
length of 2 m. West coast of Africa (south of equator) to
the Cape and along our coast to at least Maputo. Also
reported from Madagascar, Mauritius, India and Australia.
The kob is one of our most important food-fishes; it is
common down to 100 m and frequently enters estuaries;
Taken in sandy areas by net and on small hooks. Swims in
schools; sometimes skips along the surface when disturbed.
Family No. 199: SCIAENIDAE
by P.C. Heemstra
Kobs
Kobs
Body oblong to slightly elongate, somewhat compressed.
Dorsal fin margin deeply notched before last spine; anterior
part with 9-11 slender spines; rear part with 1 spine and
23-31 soft-rays. Anal fin with 2 spines and 6-9 soft-rays.
Pectoral fin rays 16-22; ventral fins 1,5. Caudal fin truncate,
rounded or rhomboid; branched rays 15. Scales cycloid or
ctenoid, covering head and extending onto soft dorsal, anal
and caudal fins. Lateral line extends to end of caudal fin.
Maxilla mostly concealed when mouth is closed. Two
nostrils on each side of snout. Opercle with 2 flat points
posteriorly. Jaws with rows of small, sharp, conical teeth;
canines present in some species; no teeth on vomer,
palatines or tongue. Branchiostegals 6 or 7; gill membranes
separate, free from isthmus; gills 4, a slit behind the last.
Gasbladder well developed, carrot-shaped, hammershaped, or anchor-shaped, and with various diverticula.
Vertebrae 23-30.
These fishes are also called "croakers" or "drums" because they are able to produce a variety of sounds by means
of muscles attached to the gasbladder. Sciaenids are common in warm coastal waters and estuaries of the world.
Some species attain a large size and are of considerable
economic importance. Many genera and well over 100
species are recognised in this family; we have 9 species in
our waters. Trewavas (1977) has revised the species of the
Indo-West Pacific region. lohnius soldado (Lacepede),
SFSA No. 551, and lohnius belangerii (Cuvier), SFSA No.
549, were reported from Natal by Fowler (1925 and 1935),
but these records were probably based on misidentifications, as neither species occurs in our area.
KEY TO GENERA
la C emarginate (upper and lower rays distinctly longer
than middle ones); no pores on chin; A II,8-9 ............ Atractoscion
Ib C truncate, rounded or sinuous (upper and lower rays not
longer than middle rays); A II ,6-8 ......................................... 2
2a 1 or 2 very large canines at front of both jaws; no pores
or barbel on chin ..................................................... Otolithes
2b No single pair of very prominent canines in jaws; chin pores
present ........................................................................... 3
3a Chin with a short thick barbel, with a pore at its tip;
broad band of villi form teeth on lower jaw; no
gasbladder appendages ............................................. Umbrina
3b Chin barbel absent, or if present, with a pore at front of its base .. 4
616
4a Mouth terminal, oblique; body depth subequal to head length,
3.2-3.6 in SL; 6 distinct pores on chin; gasbladder carrotshaped, without cephalic appendages .................................... 5
4b Mouth subterminal, horizontal; chin pores in a "false
five" pattern (with a median U-shaped groove or dimple
containing 2 tiny hidden pores); gasbladder hammershaped, with first appendage of each side reaching
the head where a lateral branch extends to the lateral
face of the pectoral arch at the junction of cleithrum
and supracleithrum (visible under operculum)
(See 1. dussumieri, p. 618.) ......................................... lohnius
5a P length 27-30% SL and about ~ distance from V
origins to A ......................................................... Atrobucca
5b P 19-22% SL, 0.5-0.7 of distance from V to A origins. Argyrosomus
Genus Argyrosomus Pylaie, 1835
Body depth 25-30% SL. Vertebrae 11 + 14. Gasbladder
carrot-shaped, with 25-35 paired appendages. Trewavas
(1977) erected a separate genus for A. thorpei, but Smith's
(1977) decision to include A. thorpei in Argyrosomus is followed here. Six species; 2 in our area.
KEY TO SPECIES
la Skin at upper end of P base scaly; C truncate;
fins yellow in life .................................................... A. thorpei
Ib Skin at upper end of P base not scaly; C rounded
or sinuate; fins grey or brown in life .................. A. hololepidotus
Kob
199.1 Argyrosomus hololepidotus
(Lacepede, 1801)
PLATE 71
Kob
Labrus hololepidotus Lacepede, 1801: 518, PI. 21, Fig. 2 ("grand Ocean
equatorial"; based on figure from manuscript of Commerson, who,
according to Cuvier, obtained the specimen from Madagascar). lohnius
hololepidotus: Smith, SFSA No. 552*; Smith & Smith, 1966: 43*.
Argyrosomus hololepidotus: Smith, 1977: 566*; Trewavas, 1977: 327*;
van der Elst, 1981: 261 *.
D X+I,26-29; A 11,7; P 17; LL 48-54; developed GR (3-5)+(9-11);
25-35 pairs of gasbladder appendages. Depth 2.9-4.0, head 3.0-3.6 in SL;
eye 5-6, interorbital 4-6 in head. P & V subequal, about 1.5 in head. About
18 enlarged teeth on each side of upper jaw. Longest GR shorter than
longest gill filament. A. regius Asso, 1801 of the northeast Atlantic and
Mediterranean, has only 7 or 8 lower limb GR and 36-42 pairs of gasbladder appendages.
Body silvery; fins grey or brown; black blotch at upper
end of P base more or less distinct. Attains 70 kg and a
length of 2 m. West coast of Africa (south of equator) to
the Cape and along our coast to at least Maputo. Also
reported from Madagascar, Mauritius, India and Australia.
The kob is one of our most important food-fishes; it is
common down to 100 m and frequently enters estuaries;