MORPHOLOGICAL CHANGES AMONG JUVENILES AND ADULTS OF SOME MARINE FISHES OF WEST BENGAL

During the course of the systematic studies on the marine fishes of our country it has been observed that juveniles of some marine fishes differ morphologically with their adults. Some morphological characters that are taken into consideration for identification develop with the maturity of the fishes; some characters present in the young stages diminish and shape of some morphological characters change with the growth of the fishes. Further, the colour pattern and the teeth pattern of many fishes change remarkably with the maturity of the fishes. As a result identification of the juveniles of fishes is problematical. An attempt has, therefore, been undertaken to record the characteristics of the juveniles of some marine fishes of West Bengal.

During the course of the systematic studies on the marine fishes of our country it has been observed that juveniles of some marine fishes differ morphologically with their adults.Some morphological characters that are taken into consideration for identification develop with the maturity of the fishes; some characters present in the young stages diminish and shape of some morphological characters change with the growth of the fishes.Further, the colour pattern and the teeth pattern of many fishes change remarkably with the maturity of the fishes.As a result identification of the juveniles of fishes is problematical.An attempt has, therefore, been undertaken to record the characteristics of the juveniles of some marine fishes of West Bengal.Diagnostic features: Body snake-like and cylindrical in shape.Mouth slightly oblique, extending beyond orbit.Teeth small, conical, present in both jaws and vomer, teeth on lower jaw divided by a longitudinal groove.Dorsal fin origin midway between gill opening and anal-fin base.Pectoral fins well developed.Body yellowish to olive or brown, mottled with dark brown, lighter below.

SYSTEMATIC LIST OF JUVENILES OF SOME MARINE FISHES OF WEST BENGAL
Distribution : India, Pakistan, Sri Lanka and Myanmar.

Characteristics of juveniles :
The colour pattern of the species changes with growth.Body of the juvenile specimens not mottled (changes in colour and in sizes of the eye, mouth and snout with the growth of the fish).Juveniles are found in the seas and estuaries but its adult forms are inhabitants of the freshwaters.Diagnostic features : Body snake like, cylindrical, compressed only along extreme tail tip.Eyes relatively small.Anterior nostril tubular, posterior nostrils along lower edge of lip.Teeth on jaws and vomer granular to molarifonn.Dorsal fin originating about a pectoral fin length behind tips of pectoral fins; pelvic fins absent.Lateral line inconspicuous.

Characteristics of juveniles :
The teeth pattern of this species changes with the growth.Teeth on jaws in the juveniles sharper and more pointed.Common English Name: Spotted catfish.
Diagnostic features : Dorsal profile of head as a steep slope to first dorsal fin base.Three pairs of barbels around mouth, maxillary pair slightly shorter, not extending up to pectoral fin base.Teeth on palate granular or molariform, in a single large, fully elliptical or semi oval patch on each side.First dorsal fin ray often produced into a long filament.
Distribution: India, Pakistan, Sri Lanka to Indo-Australian Archipelago, but not the Philippines and Australia.

Characteristics of the juveniles:
The size of the maxillary barbels differs between its juveniles and adult forms.Maxillary barbels comparatively larger, extending up to pectoral fin base in the juveniles.The teeth pattern also differs between its juveniles and adults.Size of teeth patch small and far behind the jaws, the granular teeth few and sparse.

Arius thalassinus,
Diagnostic features: Dorsal profile of head sharply rising from occiput to first dorsal fin base.Head shields weakly granulated and rugose, a prominent preorbital conical protuberance tapering as a wide 'V' posteriorly.Teeth in jaws villifonn, teeth on palate fine, in 3 patches on either side, forming a triangle, posterior patch longest, patches usually fused.Dorsal and pectoral fins each with a strong spine.
Distribution: Widespread in the Indo-West Pacific region.

Characteristics of juveniles:
The teeth pattern of this species differs between its juveniles and adult forms.Teeth patches in the juveniles separate.Talwar and Kacker,Commercial Sea Fish. India : 326,fig. 134 (Species description and distribution).
Diagnostic features : Body elongate, rounded in cross section.Upper and lower jaws greatly elongated and studded with sharp teeth.Dorsal fin with 22 or 23 soft rays.Anal fin with 18 to 21 soft rays.Caudal fin forked.A small black lateral keel on caudal peduncle.Body dark bluish green above, silvery below.A dark blue stripe along sides.
Distribution : A worldwide species in tropical and warm temperate seas.

Characteristics of juveniles:
The teeth pattern of this species differs between its juveniles and adult forms.Teeth directed anteriorly in juveniles.An elevated black lobe in the posterior part of the dorsal fin present in the juveniles.Common English name: Slender sucker fish.
Diagnostic features: Body elongate, its depth 8 to 14 times in standard length.Jaws broad, the lower projecting beyond upper.First dorsal fin replaced by a transverse laminated, oval cephalic disc (sucking disc) with 16 to 28 laminae; second dorsal long without spines.Anal fin with 29 to 41 rays.Pectoral fins short.Caudal fin almost truncate, middle rays elongated and filamentous in adult.Body with dark longitudinal band on sides bordered with white.
Distribution : Worldwide in tropical and temperate seas.

Characteristics of juveniles:
The colour pattern differs between its juveniles and adult forms.Upper and lower margins of fins white.The shape of the caudal fin also changes between its juveniles and adult forms.In juveniles the shape of the caudal fin is lanceolate.

Characteristics of juveniles:
The shape of the dorsal and anal fins differs between its juveniles and adult forms.Anterior soft rays of dorsal and anal fin extremely long and filamentous in juveniles.Body with 5 to 7 dark transverse bands.
Remarks : Adults are usually solitary and frequently found in shallow coastal waters up to 100 m. depth.Juveniles are usually pelagic and drifting.Common English Name : Indian threadfish.

Alectis indicus (Ruppell)
Diagnostic features: Body deep and strongly compressed.Profile of nape and head somewhat angular.Suborbital depth broad.Dorsal fin with 18 to 20 soft rays and anal fin with 15 to 17 soft rays.Body mostly silvery with a dusky green tinge dorsally.

Characteristics of juveniles:
The shape of the dorsal and anal fins differs between its juveniles and adult forms.Anterior soft rays of dorsal and anal fin extremely long and filamentous and the shape of pelvic fins are elongate and falcate in juveniles.Body of juveniles with dark bars and also on elongate parts of dorsal, anal and pelvic fins with dusky pits.
Remarks: Adults are in large shoals but juveniles are solitary and often enter estuaries.Common English Name: Cleftbelly trevally.
Diagnostic features : Body strongly compressed, more of less ovate.Abdomen with a deep median groove, accommodating pelvic fins, anus and anal fin spines.Pelvic fins considerably long, tips of appressed fin extending almost to anal fin origin.Caudal fin forked.Head and body bluish-green above, silvery below.Membranes of pelvic fins black with the rays white basally.
Distribution : Widespread in the Indo-Pacific.

Characteristics of juveniles :
The colour pattern of this species differs between its juveniles and adult forms.Body of juveniles with prominent dark bands and opercular spot.
Diagnostic features: Body compressed, oblong.Lips noticeably papillose; upper jaw strongly protractile; no teeth in jaws.Caudal fin deeply forked.Breast completely scaled.Black bands fade with growth and replaced by a few black patches or spots on sides.Body colour becomes yellowgreen dorsally, pale yellow below.

Characteristics of juveniles;
The teeth pattern of this species differs between its juveniles and adult forms.Lower jaw of juveniles with feeble teeth.The colour pattern also differs with its adult forms.Body colour of the juveniles silvery to yellow with 7 to 11 black bands, usually alternately broad and narrow.
Common English Name : Black pomfret.
Diagnostic features : Body diamond-shaped, fairly deep and compressed.Dorsal and anal fins long and with spines.Pectoral fins long and falcate.Pelvic fins absent in adult specimens.Caudal fin forked.Scales on lateral line scute-like on caudal peduncle.Body uniformly silvery grey to bluish brown.

Characteristics of juveniles:
The position of pelvic of this species differs with its juveniles and adult forms.Pelvic fins distinctly anterior to a vertical line through pectoral fin base in juveniles.Juveniles with dark vertical bars and long black jugular pelvic fins as well as dorsal and anal fins black.
Diagnostic features: Body oblong to elliptical, strongly compressed, with a pointed snout and a slight depression over eyes.Upper lip joined to snout at midline by a bridge of skin except crossed by a shallow groove in juveniles.Adult specimens with teeth in inner row equal in size to those in outer row.No scutes; scales on midbody below lateral line partially embedded and lanceolate.No caudal peduncle grooves.Adult specimens with a double series of 6 to 8 dusky roundish blotches above and below lateral line.
Distribution : Widespread in the tropical Indo West Pacific.

Characteristics of juveniles:
The teeth pattern of this species differs between its juveniles and adult forms.In juveniles lower jaw with 2 rows of teeth separated by a shallow groove.Dusky rounded blotches on body absent in juveniles.Common English Name: Barred queenfish.
Diagnostic features : Body strongly compressed and elongate, with a concave profile and a pointed snout.Upper jaw extends slightly beyond posterior margin of orbit.Teeth in upper jaw in a single row and in two rows in lower jaw.Body without scutes.Scales on midbody below lateral line partly embedded and lanceolate.Head and body greenish-grey dorsally, grey to silvery below.Sides of adult 4 to 8 vertically elongate plumbeous blotches, most of which intersect lateral line.
Distribution: Widely distributed throughout the Indo-Australian Archipelago and the Bay of Bengal in the Indian Ocean.

Characteristics of juveniles:
The teeth pattern of this species differs between its juveniles and adult forms.The anterior teeth in upper jaw enlarged and canine-like in the juveniles.Vertical blotches on sides of the juveniles either absent or indistinct.
Diagnostic features : Body subovate and compressed, profile of snout broadly rounded.Both jaws with bands of small villiform teeth, absent in adults above 200 mm standard length.Tongue toothless.Dorsal fin dark, lobe of fin dusky orange.Anal fin dusky to dirty orange, lobe with a brownish anterior margin.
Distribution : Widespread in the tropical Indo-West Pacific.
Characteristics of juveniles : The teeth pattern of this species differs between its juvenile and adult forms.Juveniles with 2 or 3 slender teeth present on tongue.Body of juveniles silvery with pale fins, except lobes of median fins brownish to dirty orange.

Uraspis helvolus,
Characteristic~ of juveniles ;' The teeth pattern of this species differs between its juvenile and adult forms, Teeth in 1 01 3 rows only in the juveniles.The colour pattern also changes with the growth of this specie&, Dark bats' on juveniles extend onto second dorsal and anal fins.
Diagnostic features: Body elongate, compressed and very deep.Head profile becomes vertical with development of a bony crest, especially in male adult specimens Dorsal fin extending from above eyes almost to caudal fin.Anal fin concave, extending from vent almost to caudal fin.
Caudal fin deeply forked.Back brilliant metallic blue-green, flanks silvery with golden sheen, and a row of dark spots or golden blotches running beside dorsal fin.Pectoral and pelvic fins pale.
Caudal fin silvery, with a golden sheen.
Distribution: Tropical and subtropical seas of the world.

Characteristics of juveniles:
The shape of this species differs between its juveniles and adult forms.Body of the juveniles slender, elongate with head profile slightly convex.Tips of the caudal fin lobes white and pelvic fins black.Common English Name: Short nose pony fish.
Diagnostic features : Body oval and compressed.Dorsal and ventral profiles equally convex, dorsal profile showing a distinct notch at the commencement of the nuchal crest.Head and breast scaleless.Abdomen silvery.Back with dark, wavy vertical lines extending down to about lateral line.A brown blotch on nape.A prominent eye-sized, rather diffuse, golden yellow patch on abdomen.Spinous part of dorsal fin golden at mid-height, the distal half grey.
Distribution : Seas of India, Sri Lanka, through the East Indies, to China and the J>hilippines.

Characteristics of juveniles:
The colour pattern of this species between its juveniles and adult forms.The distal half of spinous dorsal fin black in the juveniles.

Leiognathus equulus,
Diagnostic features : Body moderately deep, with head profiles straight or slightly convex.Interopercular knob absent.Second and thrid anal spines strong and about same length.Caudal fin very slightly concave.Scales fairly large; scales on head beginning above middle of eyes; soft dorsal and anal fins with a scaly sheath; longitudinal scales rows above lateral line parallel to it and those below lateral line horizontal.Body silvery green or bronze-red, with a distinct dark spot on each scale.A large dark blotch usually presents above lateral line at junction of spinous and soft dorsal fins.
Characteristics of the juveniles : The colour pattern of this species differs between its juvenile and adult forms.In juveniles the dark spot above lateral line at the junction of spinous and soft dorsal fins usually surrounded by a silvery ring, which disappear, with the growth of the fish.

Otolithes ruber,
Diagnostic features: Body slender, depth 4 to 5 times in standard length.Mouth large, tenninal, the lower jaw slightly projecting.Teeth in two rows in upper jaw with 1 or 2 pairs of strong canine teeth at front, a pair of canine teeth at tip of lower jaw.Anal fin with 2 spines and 7 soft rays, the second spine short and weak.Caudal fin rhomboid.Swimbaldder with 32 to 36 pairs of arborescent appendages, none extending into the head.Body silvery, with no dinstinctive markings.
Distribution : East coast of Africa, throughout the Indian Ocean and the Indo-Australian Archipelago.
Characteristics of the juveniles: The shape of the caudal fin changes with the growth of this fish.In juveniles the caudal fin is pointed but in adults it is rhomboid in shape.

Ephippus orbis,
Diagnostic features: Body deep, almost circular, strongly compressed, and not angular at dorsal and anal fin origin.Mouth small, terminal, and not protractile.Teeth in bands, setiform, none on palate.Dorsal fin with one inconspicuous forwardly pointing spine.Gill cover with scale almost to its ventral edge.Body silvery, with 4 or 5 vertical black bars on body from dorsal fins almost to abdomen.
Characteristics of the juveniles : The colour pattern changes with growth.In juveniles two darks bar, one through eye and another one on nape present, disappear in adults.

Scatophagus argus,
Diagnostic features : Body quadrangular, strongly compressed.Forehead steep.Mouth small, with brush-like teeth.Dorsal fin with 11 spines, the membranes deeply incised between spines; middle of dorsal fin with a deep notch.Body greenish to silvery with numerous dark spots mainly restricted to upper part of sides; no bars on body.
Distribution: India, Sri Lanka, through the East Indies to China, Taiwan, the Philippines and Queensland.

Characteristics of the juveniles:
The colour pattern changes with the growth of this fish.In juveniles bars present on the body which disappear in adults.Distribution: Red Sea, Pakistan, India, Sri Lanka, Bangladesh, through the East Indies to China and Marianas.
Characteristics of the juveniles : The position of the first dorsal fin changes from juveniles to adults.In juveniles it is in midway between snout tip and caudal fin base but in adult form dorsal fin inserted nearer to snout tip than base of caudal fin.The colour pattern also changes with growth.In juveniles the longitudinal bands are absent but these bands are often present in adults.Common English Name : Pickhandle barracuda.Common English Name: Narrow-barred Spanish mackerel.

Family
Diagnostic features : Body elongate, rather strongly compressed.Upper jaw extending to hind border of eye or slightly beyond.Gillrakers 0 to 2 on upper limb and 1 to 8 on lower limb of first gill arch.Lateral line abruptly bent downward below end of second dorsal fin.
Diagnostic features : Body elongate and more or less rounded.Head large, with a long, pointed snout.Mouth large, maxilla almost extends to front border of eye.Lower jaw projecting.No gillrakers on first arch.Upper and lower gill arch platelets rough, but without distinct spines.First dorsal fin inserted slightly behind pelvic fin origin.Body with small scales.Body blue black or brown above, sides silvery.A dark pattern of serpentine bars reaching a little below lateral line.Distribution : Indo-West Pacific.Characteristics of juveniles : The colour pattern change with the growth of this species.In juveniles bars on sides of this species is very distinct but in adults these bars are rather indistinct.Family SCOMBRIDAE 30.Scomberomorus commerson (Lacepede) 1800.Scomber commerson Lacepede, Hist.Nat.Poiss, 2 : 598, and pI.20( 1) (based on MS drawing by Commerson) (type-locality: Mauritius).