J. Natn.Sci.Foundation Sri 2005 33(4): 225-232

FEATURE ARTICLE

GENERAL FEATURES AND POTENTIAL OF PALK , AND ITS ENVIRONS

S. SIVALINGAM* 18, Pamankade Lane, 6.

Abstract: The issue of possible social and environmental serving in the former Department of Fisheries, impacts of the shipping canal proposed for the and Colombo (now Ministry of Fisheries and Aquatic Palk Strait area is a much debated topic. Therefore it is Resources) and also recently when consultation necessary to explore the general features of the said area to assess such impacts when formulating the development and assignments were done in these areas. Other management programmes relevant to the area. This paper available data have also been brought together discussed the general features of the area, its environmental and a comprehensive picture of the general and ecological condition and the fisheries potential in detail features and fisheries potential of the areas so as to give some insight to the reader on this important under study is presented below. topic. This article is based on the data collected from earlier field visits and other published information relevant to the subject. GENERAL FEATURES

INTRODUCTION Palk Bay and Palk Strait together (also called Sethusamudram), consist of an area of about Considerable interest has been created in the 17,000km2. This is an almost enclosed shallow water Palk Bay, Palk Strait and its environs recently as body that separates from the a result of the Indian project to construct a mainland and opens on the east into the shipping canal to connect BOB ( Figure 1 ). This opening is 65 km wide (GOM) and Bay of (BOB). To assess from Pt. Callimere to Pt. Pedro with an average possible impacts of this project, a detailed depth of 9.35 m. The lowest point is 13 m deep. knowledge of these areas and their fisheries Outside the opening, the continental shelf slopes potential is essential. This information is also equally down to the continental shelf edge, 200 m deep. important in formulating development and The opening on its western side into the GOM management programmes to exploit its fisheries is narrower and shallower, interrupted by a resources. Valuable information on the general larger Island and other minor sand conditions and fisheries activities in these areas bars referred to as Adam's Bridge between were collected during field assignments while and western tip of

Figure 1: The location of Pedro Bank, Palk Strait, Palk Bay and Banks in relation to Sri Lanka and India.

' Consultant: Fisheries, and Environment 226 S. Sivalingam

(Figure 2). Compared to the eastern opening, Just outside the mouth of the Strait in the the average depth is less than 1 m except at east is the Pedro Bank which is that part of the narrow Pamban Pass which is 7 m deep. the continental shelf lying to the Northeast(NE) To the south east of this western opening are and East(E) of Pt. Pedro (Figure 1) and is the Pearl Banks. Both these openings restrict contiguous with the continental shelf along the entry and mixing of fresh oceanic waters the eastern of India1. It is broadest NE with that of the Bay and Strait. and East of Pt. Pedro and narrows rapidly down to Mullaithivu. Pearl Banks on the other The deepest area of the Bay and Strait is hand is on the west coast south of Mannar only 16 m with gradually sloping sides and is Island and is the broadest part of the generally flat over a major part. The narrow continental shelf around the Island. But unlike Pedro Channel (Figure 3) starts at the the Pedro Bank a large portion ofthe Pearl northwestern tip of the Jaffna Peninsula, Banks is less than 20 m deep. There is a follows close to the coastline of the Peninsula of mostly dead and fossilized and ends beyond Elephant Pass. Like the Adam's limestone rock about 10 km from the shoreline Bridge, there is an elevated bank near theb extending from off Silavathrai up to Vankalai eastern end of the Strait in a line from in the north. (KKS) on the Peninsula to Pt. Calimere (Figure 3). The bed profile on this The is part of the Palk Bay- line is very irregular with occasional, peaks Palk Strait complex and it opens into the and valleys. The highest point on this bank northeastern part of the Bay by three narrow comes to within 3 m of the sea level. Like the and one wide opening. Its total area is about Adam's Bridge, this ridge too would retard 450 km2 and is long and narrow extending from free flow or exchange of water between the Elephant Pass in the southeast to Kayts in Strait and BOB. the northwest. Details of the topography and substratum are given by Sachithananthan and

Figure 2: Profile of the sea bed from Pamban Pass to Mannar (Adam's Bridge) (Based on Admiralty chart No. 68a soundings).

Figure 3: Profile of the sea bed from Pt. Calimere to Kankesanthurai. (Based on admiralty chart No. 68a soundings). Features and fisheries potential ofpalk bay and its envi?

Perera.2 According to their findings the entire distances into the sea, in some places extending lagoon is shallow being less than 3 m deep. to about 50 m from the shoreline. This is quite prominent from Pt. Pedro to the west, past SALINITY Keerimalai. Hardly any live coral is present in any of these locations. Westwards from The Bay, Strait and the Lagoon being west of Keerimalai and around the islands it surrounded by dry zone land mass except for is sandy or sand mixed with mud or with the two openings into the BOB and GOM, isolated rocky patches. The rocks around the have conditions quite different from that of jetties and causeways are not natural for that BOB and GOM which are oceanic in nature. area but brought from inland and placed there The few rivers flowing into them during the to prevent erosion. The situation is the same, NE causes fluctuation in the salinity it is sandy or sand mixed with mud along most of these waters. Year round salinity values for parts of the west coast of the mainland up to the Bay and Strait area are not available but Mannar Island. Its northern sector is very for the month of March 1963 the salinity shallow with dense vegetation. The northern values determined by previous studies indicate and southern shores of Mannar Island are that salinity value change from a high of 32.8 sandy permitting seine operations. ppt near the opening of the Strait into BOB to Similarly on the east coast of the Peninsula a low of 30.8 ppt near Adam's Bridge and to from Pt. Pedro downwards past Elephant even a lower value of 29.4 ppt in the Pass the shoreline is sandy with no rock or southwest corner of the Bay. There is no coral where beach seine operations are popular. indication of a definite pattern in the distribution of salinity. According to previous Admiralty Marine Chart ( U.K. Hydrographic investigations4 at Myliddy on the northern Office ) indicates that both the Bay and Strait shores of the Jaffna Peninsula (southern are characterized by the absence of hard bottom shores of the Strait ) salinity was 28.39 ppt in areas. It is mostly sand and mud, mud and December and at the Kayts Channel opening shells or mud only. Berg from his investigations into the Bay it was 13.04 ppt in December, but of the bottom conditions in the north and east in the BOB off Pt. Calimere according to coast of Sri Lanka confirms that a large portion Sheyto et aL5 the salinity was 28 ppt in of the Bay area below the 2 fathom (6 m) December 1991, at the height of the Northeast contour is soft including organic material and Monsoon. If there is any water movement clay. In the case of the Jaffna lagoon, while from the BOB through the Strait and Bay into the shoreline is sandy like the Bay area, the GOM during this monsoon, the salinity at the bottom is mostly mud.2 Most of the shallow Kayts channel would be expected to be higher. areas are full of vegetation. On the Pedro Bank on the other hand, the bottom is generally Within the Jaffna Lagoon on the other hard and flat sloping down to the continental hand, the salinity values ranges from a low of edge. Spots have also been found with rocks.6 10.3 ppt in December at some locations as Long lining trials indicated that bottom result of the Northeast monsoon rains to a conditions vary considerably within short high of 45.49 ppt in June due to the long dry distances.l On the Pearl Banks unlike in the spell. Jaffna lagoon, being a small Bay and Strait, there are many areas of hard with more rainfall runoff water coming in, ground called "paar" made up of mostly shows a higher range of fluctuation. Lithothamnian coral, small stones, shells etc. on which the pearl oysters attach themselves BOTTOM CONDITIONS and mature. Between these patches it is mostly sand mixed with shells and pieces of dead The northern shoreline of Jaffna Peninsula is coral. Between the shoreline and the reef it is characterized by the presence of fossilized sand mixed with mud and most areas with limestone rocks from the shore to various dense vegetation. The continental edge of the shelf is very rocky.6 228 S. Siualingam

TIDES AND CURRENTS in the Bay area confirm that they do not encounter any rapid current movement in the Tidal pattern within the Bay and Strait can be 3ay other than tidal movement. However, worked out from data given in the Admiralty according to the boatmen operating ferries Tide Tab1es.I It indicates that the high tide among the islands southwest of the Peninsula, sets in from Pt. Pedro and moves westwards there are fast flowing local tidal current and then southwards to reach the areas in the movements set up within a restricted area southern end of the Bay. Jaffna Lagoon, opening where the Islands are located but not in the into the Bay, is also influenced by the tides in open areas. This is due to the Islands being the Bay. Unlike in the case of the close together with narrow channels separating currents where the water flows in a particular them which interferes with the normal tidal direction continuously depending on the season, pattern in the open area of the Bay causing in the case of tides, the water mass moves rapid tidal flows in the narrow channels. back and forth without flowing through continuously. However there is bound to be Another prominent feature that confirms some mixing during the tidal movement absence of current flows within the Bay and Strait specially at the two entrances, more in the is the chlorophyll distribution. With the help of east than in the west. data obtained from the onboard Indian Remote Sensing Series Polar Satellite (IRS-P4), studies8 Regarding ocean currents in the Bay and have shown that the chlorophyll concentration Strait, no detailed information is available due during November and May (Northeast monsoon) to lack of proper investigations. However, from in the Bay and Strait varies from a low of other investigations available, it is possible to infer 3.62 mg/m3 in December to a high of 7.0 mg/ that there is no rapid oceanic current movement m3 in January. In the Gulf of Mannar the in either direction within the Palk Bay / Palk chlorophyll concentration is much lower with Strait area. Studies on the hydrography and a low of 0.4 mg/m3 in March to a high of only circulation in the western during 0.9 mg/ m3 in January. The colour prints December 19616, peak of the NE monsoon, obtained from IRS-P4 shows the chlorophyll indicate that the Coastal Current distributed more or less evenly in the Bay and (EICC) during the NE monsoon flows southwards Strait except for a small patch just south of the along the entire eastern coast of India. Though islands off the Peninsula. There is no indication the investigations were limited up to Pt. of a flushing out of the chlorophyll into the Calimere, it can be assumed that the current Gulf of Mannar. If there is any southerly current cannot just stop at that point but will continue flow from BOB through the Strait and Bay into southwards parallel to the Sri Lankan eastern the GOM during the Northeast Monsoon there continental shelf edge like off Pt. Calimere, will be no accumulation of chlorophyll in the unless there are other forces obstructing or Bay and Strait and the chlorophyll concentration deviating its southerly movement. The study in the Bay and GOM will be fairly close. also indicates that the core of the EICC flows southwards at speeds of more than 120 cm / s FISH POPULATIONS about 130 km from the shores off Pt. Calimere. That means that the core of the current is Hydrography, water depth and bottom conditions about 120 km away from the eastern mouth of are important factors that determine the type of Palk Strait. The southerly current movement fish population that inhabits any area. The reduces speed as we proceed from the core shallow nature of the Bay mostly with mud, area towards the shore and there is no water with no hard or rocky conditions and with movement about 35 km from the shoreline off limited water exchange with the oceanic waters Pt. Calimere. Under these circumstances with no resulting in stagnant conditions, do not attract water movement nearer the shore, westward popular high grade demersal varieties (sea current movement entering the Strait towards bottom dwellers) like Lethrinids {breams, Palk Bay cannot be expected. Fishermen operating meevatiya group (S), villai meen (T)} Lutianids Features and fisheries potential ofpalk bay and its envi~

(snappers, rathu gal malu group (S), seu-uillai the size composition is essential to formulate (T)) Epinephelids (reef cods, laveya group (S), management programmes. kalauai group (T)}, Elasmobranchids { sharks, skates, rays, mora group (S), sura group (T)) Along the eastern coastline of the Bay, north etc. which prefer hard bottom, deeper waters of Mannar, where there is abundant vegetation, and stable salinity conditions like Wadge and small scale operations are carried out Pedro Banks.lz9 Initial trawling trials in the for mixed inshore varieties using mainly gill Bayloindicated the presence of large quantities nets. Unlike in the open areas, Leiognathids of Leiognathids (silver bellies, karalla (S), karal are less in areas with vegetation. These areas (T)]. Subsequent trawling trials resulted in as with vegetation are also home for the much as 1000 lbs (450 kg) per hour of trawling,ll Holothurians ( beche-de-mer ) and chanks which mostly Leiognathids which are of very little are collected by diving. Along the northern shores commercial value and used mainly for fish of Mannar Island, the coastal waters are to meal. However, the muddy nature of the some extent influenced by oceanic waters across bottom favours prawns. According to previous the Adam's Bridge. The sandy nature of its investigation^'^ prawns are not uniformly entire coastline permits beach seine operations distributed in the Bay but are restricted to and inshore varieties like Engraulids (sprats, certain areas composed of very soft green mud. ha1 massa group (S), nehtali (T)), Clupeids They are also found in certain other locations (sardines, salaya (S), salai(T)}, Carangids specially around the Islands. Around (trevallies,parawa group (S), parai (T)] etc. are Kachchaithivu only two species are listed.12 caught. Appreciable quantities of juvenile Prawns have also been found along the three Leiognathids which are caught, being of no fathom (6 m) contour north of Mannar Island commercial value are discarded on the . up to Rameshwaram resulting in an average Along the southern shores of the Mannar Island, catch of 20 kg per hour1' when a larger 45 foot the waters being oceanic, Leiognathids are (13.63 m) boat was used for this survey. Due to rare and popular varieties like Clupeids, security restrictions the smaller coastal crafts Carangids, pelagic species ( surface dwellers ) based around the Bay area have not been like Sphyraenids , jelawa (S), seela exploiting the resources of the Bay, specially (T)], Scomboromorids (seer, thora group (S), the prawns, for a long time. arakula (T)) etc. are caught in the beach seines. Off the western coast of the Island in the shallow waters off , the catches of The abundance of Leiognathids in the Bay traditional crafts and mechanized 3.5 t boats area should be taken notice of. Though it is averaged 3.75 kg per hour of which 50-60% not popular for edible purposes, considering its were prawns.13 Off Chilaw for log rafts abundance and easy access to the resource (kattumaram ) the catch was only 3.47 kg per and the waters being shallow, its exploitation day of which only 24% were prawns.14 Based for manufacture of requires early on the results of the large trawlerll and the fact attention. Fish meal is a major ingredient for that it is well known that there has been the manufacture of prawn feed, large quantities considerable poaching by foreign traditional of which are imported by prawn farmers regularly. crafts, which confirms that the potential of the Since feed cost is almost 50% of the prawn prawn resource is considerable, the catch rates production cost, local manufacture of the feed by the smaller crafts based around the Bay area will reduce the foreign exchange component of may prove to be as good or even better than the production costs. According to the fishermen, that of the west coast if security restrictions are Indian crafts do fish for Leiognathids for the lifted. Unfortunately, no size data on the prawn manufacture of fish meal in . species caught in this area is available and it is difficult to know whether they are adults or In the western parts of the Strait there is juveniles. The price factor would depend on the very little fishing activity due to lack of exploitable size of the prawns caught. Also information on fish stock.Trawling trials off Kankesanthurai generally collected by diving mainly around the yielded catches of only 0.1 kg of prawns and islands. Although the lagoon fishery supports a Ill kg of fish per hour.ll In the eastern end of large fishing community, the income per the Strait which is closer to the opening into fisherman is more at a subsistence level. BOB, fishing activity is more productive and fishermen from the western parts like Mathagal Pedro Bank with a wide continental shelf sail to areas closer to the mouth of the Strait or is the best area for the exploitationof demersal just outside for their fishing operations. varieties around the Island. The fish population is somewhat similar to that of Wadge Bank1 The Jaffna lagoon has a higher salinity and and made up of adult sizes of the popular is shallower than the Bay and Strait. The bottom varieties like Lethrinids, Lutianids, Epinephelids, is muddy in a greater part of the lagoon. The Elasmobranchs and similar demersal varieties. presence of dense vegetation serves not only The juveniles of these varieties are not present as a sanctuary for the early juvenile stages of on the Bank. They are found in lagoons and some of the popular commercially important shallower areas. Earlier surveys and commercial varieties, but also providesfeed for some of the fishing operations on this Bank are well common lagoon varieties like Siganids { rabbit documented.' Subsequently there were irregular fish, orava (S), ora (T))and the lagoon supports a commercial trawling operations by the Ceylon reasonably good fishery. It is essentially a mixed Fisheries Corporation. At present there is no population made up of mostly juveniles of the commercial fishery activity on this bank by deep water demersal varieties like Lethrinids, crafts based in Sri Lanka. It is understood that Lutianids, Epinephelids and some of the common there is some poaching by foreign vessels. lagoon varieties like Siganids Hemirhamphids During the 2002 visit to Pt. Pedro, it was {half beaks, moralla (S), mural (T)), Chanos observed, that due to security reasons high chanos { milk fish, vaihka (S), pal meen '(TI) powered crafts based in the Peninsula were juvenile Sphyraenids Mugillids (grey mullet, not permitted and the fishermen were not godeya(S), maaalai(T)), cuttlefish etc. Jaffna allowed to go up to the Pedro Bank proper for lagoon is also well known for prawns and their fishing activities. However, large meshed crabs. De Bruinll lists six species of prawns bottom set nets, bottom long lining and hand while Puvanendran15 has recorded only five lining was popular with smaller crafts based different species of prawns in the 1agoon.The along the northern shores of the Peninsula largest total length recorded for any prawn species and operating just outside the opening of the is 13.3 cm. Comparison to the sizes caught off Strait into the BOB. Inspite of security limitations, Chilaw in the shallow waters of the sea where the fishermen have considerable success operating the smallest size is larger than the above sizes14 these gears and catch mainly Elasmobranchs confirms that the Jaffna lagoon catches are all (sharks, rays and skates ). Only limited quantities juveniles. The larger sizes probably migrate into of the good quality demersal varieties like the Bay as they mature or are largely exploited Lethrinids, Lutianids, Epinephelids etc, which within the lagoon before they mature. But is the main stay of the Bank, were being caught. unfortunately, no size data for the prawn catches Those operating around Pt Pedro seem to from the Bay are available. While all these are bring in the best returns. Once they have for local consumption, the high valued access to Pedro Bank proper, their returns holothurians, an exportable commodity which should be even better. is a delicacy in the , is quite common in thelagoon and around the Islands, specially in Taking into consideration the results of areas with vegetation. Due to its export demand, previous commercial operations, surveys and it is feared that it is being over exploited. recornmendation~~~~~~~~~~~and results from current However due to security reasons, the area of operations in that area, the present gears operation is restricted thus providing a (bottom set nets, bottom long lining and hand sanctuary for its survival within the security lining) appear to be the best choice for the zones. Chanks, another export commodity, is exploitation of the Pedro Bank demersal stock. Features and fisheries potential ofpalk bay and its environs 231

This requires more larger crafts than at present Scomberomorids, Sphyraenids etc. swim around which can reach the Banks and are capable of over large areas but are not known to travel in using the existing harbours in Pt. Pedro and a migratory pattern like the . On the instead of the large trawlers other hand the demersal varieties in their adult that were operated earlier which require deep stage are essentially resident in character and water harbours. These crafts will provide more stay on the same bank. They are found year- employment and require low capital input. round in the same area. They favour 20 - 40 m depths and the and shallow The Pearl Banks are famous for its pearl nature of the Bay and Strait discourage any .oysters and natural than for fish species. movement of these demersal varieties in either This is because a major portion of the Bank is direction across the Strait and Bay. In the case less than 20 m deep and is favoured by the of the Pedro Bank, there is ample area north pearl oysters. The popular adult demersal of the Pedro Bank proper along the East varieties like those that occur on the Pedro India coastline and southwards up to and Wadge Banks prefer depths from 20 to 40 m. Mullaithivu to prevent over crowding and On the Pearl Banks beyond the 20 m contour, there is no reason for these demersal varieties the shelf drops steeply and the belt between the to move across the Strait and Bay, an area not 20 m contour and the continental edge is narrow. favoured by them. For the Leiognathids, the During the 1955 Pearl Banks survey 20,an favoured environment appears to be that of the exploratory trawl haul indicated that the width Bay. They grow and multiply within the Bay as of the shelf between 20 and 200 m depth was indicated by the appreciable quantities of their very narrow and steep and very rocky but juveniles which are caught in beach seines adult demersal varieties were present. The operated on the nothern shores of Mannar rocky nature was also confirmed by a later Island. They are present in small numbers survey.l9 The pearl oyster beds are mostly outside the Bay as indicted by catch landings found between the depth of 8 and 20 m. The and not as a major item indicating that the shallow areas close to shore has considerable open oceanic environment is not favoured by amount of vegetation and though the shoreline them. There is no indication of any migration is sandy, it is not possible to operate large by this group. The Carangids are made up of beach seines because of the vegetation and many species and a detailed list for the Wadge scattered coral heads and rocks. The presence Bank (more than 15 species)with their fluctuation of pearl oysters on the Pearl Bank is not characteristics have been presented by regular with many blank years between Sivalingamz3 but no detailed data is available successful commercial operations. History of for the area concerned. It has however been the earlier Pearl Bank surveys and commercial observed that they form an important component operations are detailed by Si~alingam.~~~~~of the catch landings from both Pedro1 and Wadge Banks 23,beach seines and inshore gill There is no indication of lobsters which are net catches. Carangids as a group are considered a very valuable export product, being a major as grade one and hence their importance. product in these areas as shown by past surveys.22 The details of the general features presented above would help in assessing possible impacts The main stay of the Palk Bay, Palk Strait, of the proposed shipping canal to connect the Pedro Bank and Pearl Banks are the demersal Gulf of Mannar and the Bay of Bengal. The Palk varieties. However pelagic varieties, generally Bay, Palk strait and its environs with varying found in the surface layers like ~cokberomorids ecological and environmental conditions are (seer - thora (S), arakulla (T)) Sphyraenids inhabited by hfferent varieties of fish and prawns ( barracuda - jeela (S), seela (T)) which are which at present are not fully exploited due to classified as grade 1and higher priced, are found security reasons. They should be exploited on in the above areas but not in abundance like a rational basis to get the full benefits. the demersal varieties. Most pelagic varieties like S. Sivalingam

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