E/40
COMMERCIAL PRAWNS OF WEST PAKISTAN

by

NASIMA M. TIRMIZI
Zoology Department
University of Karachi
Karachi, West Pakistan

Abstract

The paper is based on a study of the prawns collected from commercial catches along the West Pakistan coast. The twelve species represented belong to the three genera, Penaeus, Metapenaeus and Parapenaeopsis of the subfamily Penaeinae. Keys to the species are given, together with notes on important diagnostic features, size and colour. Juveniles showing interesting developmental stages of the thelycum and petasma are illustrated. Difficulties encountered in identifying several specimens belonging to the Penaeus indicus-orientalis complex are discussed. A brief survey of the prawn fisheries of Pakistan is included.

CREVETTES D'INTERET COMMERCIAL DU PAKISTAN OCCIDENTAL

Résumé

Le présent document se fonde sur une étude des crevettes prélevées dans des prises commerciales opérées dans les eaux côtières du Pakistan occidental. Les douze espèces représentées appartiennent aux trois genres Penaeus, Metapenaeus et Parapenaeopsis, de la sous-famille des Penaeinae. L'auteur décrit les caractéristiques de ces espèces et donne des indications sur d'importants facteurs d'identification, la dimension et la couleur. Des illustrations représentent des individus jeunes où l'on peut observer d'intéressants stades de développement du thelycum et du petasma. L'auteur expose les difficultés rencontrées dans la diagnose de plusieurs spécimens appartenant au complexe Penaeus indicus-orientalis. Le document contient également un bref exposé sur les pêcheries de crevettes du Pakistan.

CAMARONES COMERCIAL DEL PAKISTAN OCCIDENTAL

Extracto

La monografía se basa en un estudio de los camarones recogidos en capturas comerciales efectuadas a lo largo de la costa del Pakistán Occidental. Las dos especies representadas pertenecen a los tres géneros Penaeus, Metapenaeus y Parapenaeopsis de la subfamilia Penaeinae. Se dan claves de las especies, junto con notas acerca de importantes características de diagnóstico, talla y color. Se ilustran formas juveniles que muestran interesantes fases de desarrollo del lycum y el petasma. Se discuten las dificultades encontradas al identificar varias especies pertenecientes al complejo Penaeus indicus-orientalis. Se incluye un breve estudio de las pesquerías de camarón de Pakistan.

1 INTRODUCTION

Pakistan has fairly large fisheries resources, and prawns occupy the most important position in the coastal fisheries. The present paper is based on the study of prawns collected from commercial catches of West Pakistan. Twelve species (not including the doubtful Penaeus orientalis), pertaining to the three genera Penaeus, Metapenaeus and Parapenaeopsis (subfamily Penaeinae) are represented. Species of Penaeus grow to a large size and make up the main bulk of landing. According to their size the prawns are locally named as ‘jaira’ (largest, reaching 8 in (203 mm) in length) ‘kalri’ and ‘kiddi’ (smallest, 3 to 4 in (76 to 102 mm) in length).

The following abbreviations are used: cl, carapace length, measured from the postorbital border to the posterior dorsal border; tl, total length, measured from tip of the rostrum to the apex of the telson. A schematic figure of the carapace (Fig. 1) is given to explain the various technical terms used in the paper.

2 SUBFAMILY PENAEINAE

Key to West Pakistan Genera of subfamily Penaeinae

Fig. 1 Schematic figure of the carapace

2.1.1 Penaeus japonicus Bate Females rather rare, males extremely rare, in West Pakistan waters.

Diagnostic features

Carapace with 3 longitudinal grooves on dorsum, extending almost to posterior border; gastro-frontal groove broad and deep, posteriorly bifid; gastro-orbital groove also broad and deep; cervical groove narrow, reaching about mid-way to dorsum; hepatic groove narrow, curving downwards in its anterior half. Gastro-frontal, gastro-orbital, antennal, cervical and hepatic carinae well marked. Carapace armed with a large antennal and small but well defined hepatic spine. Gastro-frontal carina projects anteriorly as an acute process. Rostrum armed with 1+8–9/1 teeth (in the dorsal series, 1 denotes epigastric tooth). The carapace is illustrated in Fig. 2A. Abdomen with mid-dorsal carina extending from posterior half of 4th segment to posterior margin of last segment, ending in small sharp spine. Telson armed with 3 movable spines.

In males, petasma narrow and deeply channeled, with the disto-median lobes (dm) recurved to form a sort of hood (Fig. 2B).

Thelycum pouch-like in adult females (Fig. 2C) but of different form in young females. Specimen of cl 11.5 mm (Fig. 2D) has U-shaped plate between 5th pair of pereiopods, produced into anterior lobe (1) on each side; triangular plate between 4th pair of pereiopods has sharp spine at apex and 2 small projections on posterior border. In specimens of cl 21 mm, lobes between fifth pereiopods become more pronounced and anterior border of median part of U-shaped plate grows forwards as far as median spine of last thoracic sternite; triangular plate becomes concave shield with setose lateral margins. Specimen of cl 24 mm shows pouch-like form developing. Characteristic form of adult thelycum assumed by specimens of cl about 31 mm (Tirmizi, 1958). In large specimens, anterior border of ventral wall of thelycum grows forward and conceals dorsal walls (Fig. 2C).

Fresh specimens of P. japonicus exhibit 2 colour patterns: (i) body pale pink with bright orange and black stripes on abdomen, carapace with black markings, distal part of uropods and telson also black; (ii) body either pale pink or blue with black stripes; antennae, pereiopods and pleopods yellow; distal half of exopod of each uropod bright yellow, with distal border blue, fringed with carmine setae; telson has yellow and blue bands.

Local name: Tiger prawns

Maximum size: tl 216 mm (female)

Fig. 2 Penaeus japonicus Bate

A carapace in lateral view (scale = 10 mm);
B distal part of petasma in ventral view, from specimen of cl 37 mm (dm = distomedian lobe);
C thelycum of adult female of cl 31 mm;
D early stage in formation of thelycum (1 = lobe-like projection).

2.1.2 Penaeus semisulcatus De Haan This species is fairly well represented in West Pakistan.

Diagnostic features

Post-rostral carina sulcate, reaching almost to posterior margin of carapace; adrostral grooves extending just beyond epigastric tooth; gastro-frontal and gastro-orbital grooves shallow; hepatic and cervical grooves narrow; hepatic groove inclined downwards in its anterior half. Orbito-antennal, antennal, cervical and hepatic carinae well defined; gastro-frontal absent; antennal and hepatic spines about equally developed. Rostrum with 1+6–7/2–3 teeth. Abdomen with mid-dorsal carina extending from posterior half of 4th segment to posterior margin of last, ends in a small, sharp spine. Telson unarmed. Small exopod on 5th pereiopod (absent in P. monodon).

Petasma resembles that of P. japonicus except that it is rather open and distomedian lobes are small.

Thelycum consists of 2 lateral plates (occupying space between 5th pereiopods) and median anterior plate. Raised median margins of lateral plates approximate in midline. Median plate has median longitudinal ridge on posterior half. Anterior margin of plate somewhat arc-shaped.

Freshly preserved specimens have cream coloured body and legs with steel grey stripes, rami of pleopods grey with carmine setae, distal half of pleopods grey, fringed with carmine setae.

Maximum size: tl 230 mm (impregnated female).

2.1.3. Penaeus monodon Fabricius This species is rather rare.

Diagnostic features

P. monodon is closely related to P. semisulcatus but attains a much greater size.

Post-rostral carina with shallow groove; adrostral grooves vanishing before epigastric tooth; gastro-orbital carina small, occupying posterior 1/3 of distance between hepatic spine and orbital angle; hepatic carina almost straight. 5th pereiopod without exopod. Rostrum with 1+7/3 teeth. Disto-median processes of petasma small, lobe-like and sub-apical.

Maximum size: tl 330 mm (female).

2.1.4 (?) Penaeus orientalis Kishinouye Not very common.

Remarks

P. orientalis is so far known from Northern China, Japan, Korea and Hong Kong (Cheung, 1960). In the present collection there are several specimens, belonging to both sexes, which show all the characters of P. orientalis, including the form of the thelycum (Fig. 3B) and the appendix masculina. They also have the maxillulary palp 3-segmented, a character which separates P. orientalis from the closely related P. indicus. According to Kubo (1949:302) the 3rd pereiopods extend “… as far as antennal scale”. In my specimens the 3rd pereiopods reach to or beyond the tip of the scale, except in one specimen, a female of cl 14.5 mm, in which they are short and extend to about 2/3 of the length of the scale. The anterior part of the carapace of a male is illustrated in Fig. 3A.

Largest specimen measures 155 mm (tl)

Apart from these there are several problematical specimens of up to 177 mm (tl) in which the maxillulary palp of 1 side is 2-segmented and that of the other 3-segmented (Fig. 3C). The thelycum and appendix masculina of these specimens resemble those of P. indicus.

Fig. 3 (?) Penaeus orientalis Kishinouye

A anterior carapace, lateral (scale = 5 mm);
B thelycum (scale = 1 mm);
C right and left maxillules of a specimen showing variation in the segmentation of the palps (scale = 1 mm).

2.1.5 Penaeus indicus H. Milne Edwards This species is also rare.

Diagnostic features

Post-rostral carina not grooved (marked with a few pits); adrostral grooves reach just below epigastric tooth; gastro-frontal groove shallow; gastro-orbital broad and rather deep, cervical narrow; hepatic groove absent; adrostral, gastro-orbital, antennal and cervical carinae well marked, gastro-orbital occupying about posterior 2/3 of the distance between hepatic spine and orbital angle. Rostral crest high; rostrum armed with 1+6–8/4–5 teeth. Mid-dorsal carina of abdomen resembles that of previous species; telson unarmed. In adult males the dactylus of 3rd maxilliped is as long as the propodus.

Petasma not deeply channeled; disto-median lobes small, slightly recurved, extending beyond lateral lobes.

Thelycum consists of 2 lateral plates which form an almost circular seminal receptacle; only small anterior portion of median plate visible.

The body is cream coloured, speckled with grey.

Maximum size: tl 193 mm (female).

2.1.6 Penaeus merguiensis De Man This species outnumbers all the others in catches in the coastal waters of West Pakistan.

Diagnostic features

There is a fairly close resemblance to P. indicus.

Rostral crest high and triangular, rostrum armed with 1+6–7/3–5 teeth. Adrostral carina does not reach as far as epigastric tooth, gastro-orbital carina occupies middle ⅓ of the distance between hepatic spine and gastro-orbital angle. Dactylus of 3rd maxilliped 0.5 to 0.6 times length of propodus in adults.

Disto-median lobes of petasma acute and extend beyond apex; the seminal receptacle oval in outline.

Maximum size: tl 240 mm (female).

2.1.7 Penaeus penicillatus Alcock This species is also very common in the commercial catches.

Diagnostic features

P. penicillatus can be differentiated from the previous species by the following points.

Rostral crest convex, rostrum armed with 1+5–7/3–5 teeth; adrostral carina extends just beyond epigastric tooth, dactylus of 3rd maxilliped 1.5 to 2.7 times the length of propodus in adult specimens. Distomedian lobes of petasma small rounded and do not extend beyond apex of lateral lobes. Outline of seminal receptacle almost circular.

Maximum size: tl 210 mm (female).

2.2 Genus Metapenaeus Wood-Mason

This genus is represented by 4 species. All are fairly large, and all except M. monoceros are abundant in the catches.

Key to West Pakistan species of genus Metapenaeus

2.2.1 Metapenaeus stebbingi Nobili This species was first recorded from West Pakistan in 1962 (Tirmizi, 1962). It seems to be fairly well represented in the local catches.

Diagnostic features

Gastro-orbital carina oblique, ridge-like; antennal and cervical carinae present; gastro-orbital groove gradually widening anteriorly; cervical groove well defined both above and below hepatic spine; post-rostral carina not traceable on posterior half of carapace; rostrum armed with 1+8–9 teeth (Fig. 4). Abdomen with mid-dorsal carina extending from posterior half of 4th abdominal somite to posterior margin of 6th, ends in sharp spine; telson armed with row of spinules on each lateral border.

Each petasmal half with dorso-median style, armed ventrally, and 3 laterally directed projections.

Thelycum consists of median plate resembling inverted T, situated on last sternite (between 5th pereiopods); triangular plate on either side with apex directed posteriorly and fitting closely to hollows of T-shaped median plate.

The body is pale, speckled with grey and rust. Outer half of the exopod and distal half of the endopod of uropod are rust coloured.

Maximum size: tl 120 mm. The smallest specimen recorded by the author is only 25 mm (tl).

2.2.2 Metapenaeus brevicornis (H. Milne Edwards)

Diagnostic features

Gastro-frontal antennal and gastro-orbital carinae all faint; cervical groove well defined both above and below hepatic spine; post-rostral carina extending almost to posterior margin of carapace; rostral crest high and triangular, rostrum armed with 1+4–5 teeth, distal half or less edentate; rostrum either extending as far as distal margin of last segment of antennular peduncle, or may be short, not reaching beyond penultimate segment. Abdomen with mid-dorsal carina on middle of 3rd segment and continuous from posterior part of the 4th segment to posterior margin of last; ends bluntly or in acute process. Telson armed with 3 to 4 pairs of spines.

Fig. 4 Metapenaeus stebbingi Nobili, carapace in lateral view.
(scale = 5 mm).

Fig. 6 Parapenaeopsis stylifera (H. Milne Edwards), carapace in lateral view. (Scale = 5 mm)

Petasma with dorsally curved disto-median styles, which are not serrated, spoutlike projections directed antero-laterally.

Thelycum with median and 2 lateral plates; median plate broad, sub-quadrangular, lateral plates C-shaped.

2.2.3 Metapenaeus monoceros (Fabricius)

Diagnostic features

Carapace very similar to that of M. brevicornis; rostrum long extending as far as distal margin of last segment of antennular peduncle, armed with 1+8–9 teeth; rostral teeth extending almost to tip; lateral margin of telson armed with rows of microscopic spines.

Petasma with thick, convoluted disto-lateral processes.

Thelycum with median plate narrow, tongue-like and ventrally grooved; lateral plates C-shaped, lateral margin of each plate raised giving cup-like appearance to seminal receptacle.

Maximum size: tl 190 mm.

2.2.4 Metapenaeus affinis (H. Milne Edwards)

Diagnostic features

Differs from the previous species in the following:

Rostrum long extending beyond antennular peduncle, armed with 1+7–10 teeth; distal ⅓ unarmed. 3rd abdominal somite without mid-dorsal carina.

Petasma with crescent-shaped disto-lateral projections. Petasma of young males, showing early development stages, are illustrated in Fig. 5.

Median plate of thelycum broader and resembling an inverted Y; lateral plates small, C-shaped.

Maximum size: tl 186 mm.

2.3 Genus Parapenaeopsis Alcock

Only 2 species of this genus are netted along the West Pakistan coast. They can be separated by the following key:

Key to West Pakistan species of genus Parapenaeopsis

Fig. 5 Metapenaeus affinis (H. Milne Edwards), developmental stages of the petasma (distal, left half). cl of specimens: A, 13 mm; B, 16 mm; C, 18 mm; D, 20 mm. (Scale = 0.5 mm)

2.3.1 Parapenaeopsis stylifera (H. Milne Edwards) This species is very common in the creeks and is an important economic species.

Diagnostic features

Post-rostral carina extending almost to posterior border of the carapace, adrostral not reaching as far as epigastric tooth, gastro-frontal hardly marked, antennal carina well developed; longitudinal suture on anterior half of the carapace; antennal and hepatic spines present; rostrum long, styliform, extending far beyond antennular peduncle, armed with 1+4–7 teeth, edentate in its distal half, which is upcurved (Fig. 6). Abdomen with mid-dorsal carina on somites 4 to 6; telson armed with 4 pairs of spines.

Petasma with long, tube-like disto-median projections.

Thelycum with broad anterior plate, and posterior plate which is deeply notched on middle of anterior half.

Body light pink speckled with grey spots; tips of uropods dark. The species usually has a good taste. Along with 'normal' specimens are also found some which show no morphological differences but each abdominal segment has a conspicuous white band. These specimens have a bad taste and spoil the quality of the others.

Local name: Kiddi.

Maximum size: 120 mm (tl).

2.3.2 Parapenaeopsis sculptilis (Heller) Though represented in the commercial catches, the meat is not relished and specimens of this species are generally removed.

Diagnostic features

P. sculptilis can be separated from P. stylifera by the following:

Rostrum shorter, extending at most to just beyond antennular peduncle. Mid-dorsal carina on posterior ¾ of each of first 3 abdominal segments. Petasma with wing-like disto-median projections and spout-like lateral projections. Thelycum with median tuft of setae on posterior plate, posterior plate not notched.

General surface of body pale pink, with broad black stripes.

Maximum size: tl 170 mm.

3 A BRIEF SURVEY OF PRAWN FISHERIES IN WEST PAKISTAN

The fisheries resources of Pakistan are fairly large but, unfortunately, the extent of these resources has not yet been assessed.

The coast of West Pakistan may be divided into two distinct regions.

(a) Karachi and Sind coast: Extends from Karachi in a southeasterly direction. It is characterized by a net-work of creeks ending in Sir Creek which forms a boundary between Pakistan and India. The coast is about 200 mi (320 km) long. It is shallow and very gradually slopes outwards. The 100 fm (180 m) line is about 60 mi (about 100 km) from the coast, except at the mouth of the River Indus, where the sea becomes abruptly deep. Very few trees are present on the coast except the mangroves which thrive very well. There are a few villages and temporary habitations spring up during the fishing season, and they move according to the catch.

(b) Mekran coast: Extends from Hub River to Gwatar Bay. It is about 350 mi (570 km) long and rather steep; the 100 fm line is 25 to 30 mi (40 to 50 km) off the coast. The entire coast is dry and barren and is formed of successive depressions and folds, chains of low and steep hills of soft stone run more or less parallel to the coast-line, which is intersected by bays and small sandy plains. The coast is dotted with about 21 fishing settlements of both temporary and permanent nature.

The shrimp season in West Pakistan commences in October and continues till the end of April. The best period, however, is from November to the middle of March. It is during this period that the shrimps and prawns of best commercial value are available. Small prawns locally known as ‘bonkey’ are available in July and August.

The fishing fleet of West Pakistan consists of about 5,500 boats, including trawlers, launches, sailing boats and a few row boats. Average yearly catch on the Sind and Mekran coast is about 8,000 tons. Local consumption is very little and the prawns are exported to several countries. Frozen prawns are much in demand, and the main bulk goes to U.S.A. Dried and canned prawns are also exported.

West Pakistan, at present, has about 21 fish processing plants, but due to insufficient landing all the plants are not in operation. It is estimated that the maximum utilization is only 30 percent of the capacity.

The reason for this dearth in catches is probably due to inadequate knowledge about the prawns. The local fishermen are unaware of the breeding grounds and know very little about the migration of these shrimps.

Since prawns and shrimps play an important role in the economy of our country it is necessary to gain further knowledge about them. While measures are being taken to introduce modern methods for fishing, equal importance should be given to the preservation of stocks.

4 REFERENCES

Cheung, T.S., 1960 A key to the identification of Hong Kong Penaeid prawns with comments on points of systematic interest. Hong Kong Univ.Fish.J., 3:61–9

Kubo, I., 1949 Studies on the penaeids of Japanese and its adjacent waters. J.Tokyo Coll. Fish., 36(1):1–467

Racek, A.A., 1955 Littoral Penaeinae from New South Wales and adjacent Queensland waters. Aust.J.mar.Freshwat.Res., 6(2):209–41

Racek, A.E. and W. Dall, 1965 Littoral Penaeinae (Crustacea Decapoda) from Northern Australia, New Guinea, and adjacent waters. Verh.K.ned.Akad.Wet.(B), 56(3):1–119

Tirmizi, N.M., 1958 A study of some developmental stages of the thelycum and its relation to the spermatophores in the prawn Penaeus japonicus Bate. Proc.zool.Soc. Lond., 131(2):231–44

Tirmizi, N.M., 1962 A new record for Metapenaeus stebbingi Nobili, from Pakistan. Crustaceana, 4(2):103–6

Acknowledgments

I am grateful to Dr. Rahimullah Qureshi of the Central Fisheries Department for sending samples from commercial catches. I am also much obliged to Mr. A.R. Tarique of the Pakistan Fisheries Ltd. for helping in getting the necessary material and also for supplying information regarding prawn fisheries in Pakistan. I wish to take this opportunity to thank Miss Quddosi Bashir for assisting me in this work.