MARINE INVERTEBRATES OF DIGHA COAST AND SOME RECOMENDATIONS ON THEIR CONSERVATION

The ftrst study on marine fauna of Digha coast is known from the work of Bharati Goswami during 1975-87 (Bharati Goswami, 1992). Other workers, viz., Bairagi, Bhadra, Mukhopadhyaya, Misra, Reddy (1995); Subba Rao et. al., (1992, 1995); Talukdar et. al., (1996); Ramakrishna and Sarkar (1998); Sastry (1995, 1998) and Mitra et. al., (2002) also reported some marine invertebrates under different faunal groups from Hughly-Matla estuary, including Digha. But uptil recently there is no comprehensive updated list of marine invertebrates from Digha coast and adjoining areas. With the establishment of Marine Aquarium and Research Centre, Digha in the year 1990, opportunity was launched for undertaking an extensive exploration and studying seasonal changes that have been taken place on the coastal biodiversity in this area. Accordingly, the authors of the present work, started collecting the detailed faunal infonnation from Digha and adjoining coastal areas [Fig. 2 and 3].


INTRODUCTION
The ftrst study on marine fauna of Digha coast is known from the work of Bharati Goswami during 1975-87 (Bharati Goswami, 1992).Other workers, viz., Bairagi, Bhadra, Mukhopadhyaya, Misra, Reddy (1995); Subba Rao et.al., (1992,1995); Talukdar et. al., (1996); Ramakrishna and Sarkar (1998); Sastry (1995,1998) and Mitra et. al., (2002) also reported some marine invertebrates under different faunal groups from Hughly-Matla estuary, including Digha.But uptil recently there is no comprehensive updated list of marine invertebrates from Digha coast and adjoining areas.With the establishment of Marine Aquarium and Research Centre, Digha in the year 1990, opportunity was launched for undertaking an extensive exploration and studying seasonal changes that have been taken place on the coastal biodiversity in this area.Accordingly, the authors of the present work, started collecting the detailed faunal infonnation from Digha and adjoining coastal areas [Fig. 2 and 3].
During the study, it has transpired that exploitation of coastal resources has very abruptly increased in recent years.Several new fishing gears are employed, a number of new marine organisms are recognized as commercial fish and non fish resources.Also, the number of trawlers has increased to a large extent.
The present paper based on the observations from 1990 to 2000 (including the current records upto January, 2002), is an uptodate database for the available species of marine invertebrates from this area.

MATERIALS AND METHODS
Digha is situated at 21 0 36' 30" N latitude and 87 0 32' E longitude and has a potential coast line of about 12 km. of its own (Udipore to Digha mohona), of which the western part (Udipore to Digha hospital ghat) is considered to be the accretion zone, whereas the eastern part (Sea Hawk ghat to Shankarpur) is considered as eroded zone.
The observation and collection of specimens for this work were made as follows : 1. Considering the diurnal catch pattern, daily collections were made from the fishing gears and also from discarded bycatch, cast off on beach [Fig.4 and 5].
2. Spot collection of specimens and collection ofnecessory informations were made on weekly and fortnightly basis.
These collecting localities cover the total shore length of about 40 km.The till date collection of different animal species available from the Digha beach and adjoining areas are charted in the form of a checklist (Table 1).Seasonal occurance of some of the species is listed in Table 2

SUMMARY OF OBSERVATIONS
In this study a total of 331 species under 207 genera, 137 families, 44 orders, 4 subclasses, 18 classes and 9 phyla have been counted.
Beside these, one species of mole crab (Albunia sp.?), a burrowing decapod; one species of nudibranch and one species of bryozoa (Membranipora sp.?) are also collected by authors, but failed to identify properly during this study.
It is also observed that, Amalda ampla" is also being increasingly threatened in Digha coast due to uncontrolled collection of live specimen by local women for some ornamental purposes.
The present record of Cadulus clavatum and Stellaster equestris are based only upon the previous record (Goswami,1992; Subba Rao, et al., 1992 and Sastry, 1998 respectively).No live specimen, neither a single shell have not been found.
Since Digha beach became familier, large number of visitors came for pleasure trip and also for zoological excurssions.Very often they continued their works while collecting a large number of specimens.Simulteniously, they also collected a number of species which are now rare due to destruction of their habitat and over exploitation.
With this, the recent development of aquaculture has introduced a new economic group along with fishermen and their daily activities destroy a good numbers of invertebrates (including their •egg capsules) and also the fish spawn at the time of collecting the post larva of tiger shrimp (Penaeus monodon) [Fig.3, 4 and 5].
In view of faunal richness which is now threatened by exploitation of marine fishery resources, tourism without ecofriendly awareness and overall socio-economic development, this coastal zone demands more protective measures.

RECOMMENDATIONS REGARDING CONSERVATION OF BIODIVERSITY
t.A programme for the awareness of fishermen, tourists, collectors of zoological samples has to be undertaken, as the fishermen and also the over-enthusiastic tourists destroy the living organism (with or without their knowledge).
2. Restrictions must be imposed on fishing activities except permicible seasons, and also on the mesh size of fishing nets.
3. Dragging on intertidal areas is to be banned or restricted and selective sorting and releasing of bycatch organisms in the sea before their death must be made compulssory.
4. Overexploitation by repeatedly collecting the same organisms (especially the various species of live Sea anemone, Sea pen, Hermit crab, Red crab, Horse-shoe crab, bivalve and Sea star) year after year from beach by the study team from various educational institutions for display in their museum should be restricted.
General tourists as well as excurssion team often collect a lot of specimen in the frrst flush of enthusiasm but it is observed that most of those are finally dumped on the beach where the animals are allowed to die and rot.This has also to be banned.
In this context an alternative way might be taken as taking a number of photographs of the organisms from various angles without disturbing them and to collect only very few examples of each species, particularly of rare and poorly populated species. 5. Comprehensive assesment (chemical, biological and environmental) of bycatch organisms in the light of fishery exploitation and bio-medical studies may be invited.

3.
Collections were made from individuals cruises of fishing vessels of Shankarpur and Digha mohana.4. Collections were also made from bag net or Bagda net (triangular net made for collection of post larva of Penaeus monodon), [Fig.3]. 5. Collection of rare specimens from fishermen and stray collections from auction yard of Digha mohona and Shankarpur fishing harbour were made.6.Across and vertical survey of shore in different tide times for collections of shore animals of different habitat and niche was also undertaken.

Table 1 .
. A checklist of invertebrate fauna of Digha coast and adjoining areas.(* Reported for first time).