Distribution of Fin-fish Eggs and Larvae from Point Calimere and Muthupettai, South East Coast of India

The distribution of finfish eggs and larvae often area will help in a great deal in capture management and also useful in locating shoals of fish and their breeding grounds of ecosystem [1]. Though many works are available on the abundance of fish eggs and larvae in Indian water [2-5], this type of work has not been probed in Point Calimere and Muthupettai, which is said to have great larval resources, hence the present study has been carried out to find out the distribution of fin fish eggs and larvae Point Calimere and Muthupettai.


Introduction
The distribution of finfish eggs and larvae often area will help in a great deal in capture management and also useful in locating shoals of fish and their breeding grounds of ecosystem [1]. Though many works are available on the abundance of fish eggs and larvae in Indian water [2][3][4][5], this type of work has not been probed in Point Calimere and Muthupettai, which is said to have great larval resources, hence the present study has been carried out to find out the distribution of fin fish eggs and larvae Point Calimere and Muthupettai.

Sampling procedure
The samples were collected fortnightly intervals during the period of September 2006 to August 2007. The samples is with the help of plankton net made in Number of 20 bolting silk with a mesh size of 0.076 mm measuring one half meters in length and 405 mm wide at the mouth from two stations at Point Calimere and Muthupettai mangroves area, monthly samples of Ichthyoplankton were also made employing the same net from station 1 and 2.
The collected samples were preserved in 10% formalin and brought to the laboratory and the fish eggs and larvae were picked out from the whole sample and again preserved in 5% neutralized formalin for detailed method of [2,6]. Samples from all the stations were preserved onboard in 5% buffered formalin-seawater and sorted in the laboratory [7]. Fin fish eggs and larvae were sorted out from this sample and their abundance was expressed as Number of eggs/100 m³. For the identification of eggs and larvae of fin fishes are the earlier investigations made by [8][9][10][11][12][13][14][15][16]. A suite of statistical analyze were carried out using statistical packages SPSS Version 11.5.

Species diversity
To express the species diversity of the stations the Shannon-Wiener species diversity index was used. The formula is; n i=i N Y yi N = ∑

Shannon-Wiener diversity (H')
To assess the species diversity, the following formula of [17] was used.
This can also be written as

Simpson index (D')
Species richness was calculated by [18] formula. The eggs are completely spherical, colorless and transparent. The perivitelline space is very narrow and measured 1.26 mm in diameter. The segmented yolk contains 15 to 18 oil globules. In the present eggs are found 19 oil globules of uneven size, aggregated at the center of the yolk the diameter of yolk is 1.225 mm and that of the oil globules ranged from about 0.05 mm to 0.08 mm (Figure 1). Eggs are mostly found in pelagic, spherical, colorless and transparent. Diameter of the egg ranges between 1.36 mm and 1.41 mm. Yolk is spherical, coarsely vacuolated, colorless and transparent. The diameter of the yolk ranges from 0.10 to 0.92 mm. The yolk and embryo occupy half of the egg capsule, leaving a wide perivitelline space. Single, golden yellow colored oil globule is present on the yolk mass. Oil globule size was ranges from 0.09 to 0.13 mm. Egg envelop is smooth and the embryonic pigmentation is absent. The embryo is well developed with head, trunk and caudal region but the caudal region is free from the yolk. The eyes, auditory vesicle and the myotimes are clearly visible. For present investigation, eggs were collected during July to September-2006, January, February, April, June and September-2007. The egg was spherical in shape and translucent with a diameter 0.6 mm, yolk highly vacuolated and yellowish in colour and the diameter around 0.46 mm, with an yellowish oil globule of 0.22 mm in diameter perivitelline space is wide, thus confirm the identity of egg as belonging to Sardinella gibbosa. Myotomes also visible through the transparency of body, few pigment spots are dispersed on head. The eggs are pelagic, transparent oval shaped and measured about 1.34 mm in length and 0.56 mm in breadth. The perivitelline space is very narrow. The yolk exhibits very clear segmentation. The oil globules is single, pale yellow, 0.07 mm in diameter and situated at the posterior most part of the yolk. A vacuole-like structure is seen just above the oil globule. The developing embryo is found to have 14 body somites and is free from any sort of pigmentation. The eggs are spherical with a diameter 1.10 mm. The yolk is clear and segmented without oil globule. In the earliest stage obtained, the blastoderm has already begun to spread over the surface of the yolk and is in from of a cap over it. The perivitelline space is narrow. The size and shape of the eggs and other characters like coarsely segmented yolk, absence of pigmentation and oil globule show that the eggs described here are those of Thryssa sp. The color of the egg is pale white, spherical in shape with bold hexangonal markings or the egg membrane. The diameter of the egg is 1.12 mm. The yolk is rough in nature. There are 29 ridges on the egg membrane and the space between two ridges is 0.10-0.28 mm. A total of 21 oil globules are countable of which, 3-6 are comparatively larger. Their average diameter is 0.09 mm. The previtelline space is narrow. A few melanophores are present in the head region of the developing embryo and few stellate are also present in the chromatophores on the yolk. The eggs are totally spherical with a diameter ranging from 0.80 mm-0.086 mm. The yolk is unsegmented with a single oil globule (0.15 to 0.18 mm). In the earliest stage obtained presently, the embryo is somewhat advanced in development with the tail section being free from the yolk mass. The eyes and aural vesicles are well developed. The embryo performs. Occasional are jerking movements inside the egg membrane. Three small bands of chromatophores are present in the body. Several small pigments are sparsely distributed all over the yolk. Eggs are mostly pelagic, spherical, colorless and translucent. Eggs diameter ranges between 1.62 to 1.9 mm (egg is easily recognized by their large size). Yolk mass is spherical, segmented, colorless and transparent, the yolk diameter range between 1.28 mm. 7 to 20 small sized oil globules are distributed irregularly in the yolk mass. Perivitelline width is tapered. Envelop not smooth. But it has on top of its surface a network of fine folds, which give a honeycomb like appearance; the network is much better, too fine, the meshes barely having a diameter of 0.01 mm. Unpigmented in nature. Eggs are pelagic, spherical, colorless and transparent: the diameter of the eggs ranging between 0.62 to 0.72 mm. Yolk is spherical, clear, and unsegmented. Single spherical shaped oil globule is present on the yolk mass, measuring 0.14 to 0.15 mm in diameter. Perivitelline width is narrow. A few brownish black pigment spots are present on the dorsal side of the body including had region, of the embryo, and such pigmentation is present on the oil globule also. Body is compressed in this specimen. The first dorsal fin has 4 spines. The second dorsal with first spine is with 8 rays, anal fin with 3 spines and 8 rays and pectoral with 12 rays. Caudal fin shows the emarginated shape of adult; with 13-branched rays. Dorsal-lateral part of the body densely is pigmented with few pigment spots appearing on the opercula region. The post larva transforms into juvenile by the formation of adipose eyelids, scales, branchiostegals and long, sylinder gill-rackers. The total length of specimens different from 20.00 mm-28.0 mm and body extended and round mouth oblique and wide blunt or pointed. Origin of anal fin below the adipose dorsal. Body is translucent with a characteristic pigment pattern. Post larvae of Sardinella sp. can readily be recognized by either side of the alimentary cannel an unpaired one at the posterior end of anal fin. This is the detailed character of the post larvae Sardinella sp. This fades away during the transformation into juvenile. In the post larvae collected presently, the ventral fins have not yet appeared. Rays is a dorsal, anal and pectoral fin is not separate. Teeth and scales are useful for the detection of the adult.

Seasonal distribution of fin fish eggs and larvae
The present study revealed that over all abundance of eggs and larvae was more in post monsoon (January to March) and summer (April to June), followed by pre-monsoon (July to September) and monsoon (October to December).

Summer:
The summer abundance of eggs and larvae, their total number for the one year period being 133/100 m 3

Discussion
Examination of seasonal settlement and recruitment can be noted to identify the most seasonable time to conducts censes of recruitment so as to draw annual predications. On the biodiversity front also the eggs and larvae attain and lot of importance. The results of present study revealed that 9 Families of eggs and larvae, 18 species of eggs and 8 species of larvae were recorded in Point Calimere and 24 species of eggs and 12 species of larvae in Muthupettai. The Ichthyoplankton distribution indicated spawning activity of coastal fish species that inhabit these areas. Coastal regions adjacent to estuaries providing favorable conditions for the development of fish species that sheltered these areas as nursery and protection for their eggs and larvae.
In many studies have been reported the independence between the spatial and temporal distribution of fish larvae and zooplankton. [20] Stated that the most common problem associated to plankton studies was the use of adequate mesh size to sample fish larvae and their prey. In general, larvae smaller than 10 mm preyed on plankton organisms is smaller than 200 µm. However, mesh sizes used to collect Ichthyoplankton generally exceed 200 µm. The weakening of Ekman transport in the coastal regions associated to the closed geotropic circulation pattern of the Bight prevents fish eggs and larvae to be adverted offshore [21].
The response to environmental variables has however been shown to be species specific [22], the spatial distribution of fish larvae was greatly influenced by hydrobiology [23], salinity and turbidity are important factors associated with larval fish abundance [24,25]. Meteorological and oceanographic conditions influence the feeding of organisms and currents can transport eggs and larvae by [26]. Definite relation in the It was evidenced by positive significant correlation r=0.344; r=0.926; r=0.982; r=0.916 between abundance of larvae and physical parameters and negative significant correlation value r=-0.048 and r=-0.115 between the larvae and total suspended solid and turbidity. Similar report has been reported in Arasalar estuary, Karaikal [27]. Present study also stated that summer the larvae were observed in high. It may be due to the spawning of the fishes during this season. It is evidenced by [28]. During the monsoon the larvae diversity was low, due to the low salinity, when the ecosystem dominated by rain fed freshwater influx draining from land irrigation enhanced and rivers, which shows with diversity. The similar report has been noted by [29].
In the present study, a total of 22 species of eggs and 15 species of larvae were recorded from both stations. Of which, larvae of Thryssa dussumieri, Lisa dussumier, Mugil cephalus, Hemiramphus far, Hilsa kelee, Caranx sp and Gerras oblogus were observed from only in Point Calimere. Distributions of fish eggs and larvae have low at station-1 than at station-2. It may be due the depth of water turbidity and total suspended solids. Summer the larvae were observed in high. Other studies found similar results in other areas: most coastal species know to breed at the Arrabida marine park during the spring and summer period [30][31][32].
A total 2018/100 m 3 eggs and 729/100 m 3 larvae belonging to 9 families were identified. A similar observation has also been other study area reported that a total of 32140 /100 m 3 eggs and 6582 /100 m 3 larvae were collected from plankton samples and 69 species belonging to 27 families were identified by [33], in related to this topic another work, a total of 35 555/100 m 3 larvae, representing 28 families and 63 taxa were collected samples in estuary at North Brazil by [31,34] described a similar type of works around 1254/100 m 3 eggs and 2840/100 m 3 larvae and fry of 17 fish species were also identified in White sea.
Rita Borges et al. [33] reported that the most abundant developmental stages of clupeoidae were 24.63% of the total catch. Other studies found similar results the most abundant group in Clupeoidae around 70.4% were recorded by Beligin, Yesim [34]. Regarding the distribution abundance of fish eggs and larvae the research area, the Clupeoidae constituted the dominant groups. Present investigation also revealed that Opichthidae, Carangidae, Channidae, Mugilidae and Sarranidae in the study area, and Mugil cephalus, Opichthidae sp and Scomberomorus sp were also recorded. The similar report recorded by Barletta and Emmanul [33,35]. Here it can conclude that, fish farming industry is an important source of seafood with to increase the fish production mainly on coastal regions. Generally, the fish farming is a major problem of seed resources. Hatchery and standard technology for the mass scale production of oceanic finfish seed from the natural environment is one of the important sources at present. The mangrove area of this sampling station is an important of fish production and rich in resources. It is suitable places of vertebrates by providing a breeding site and by giving protection. In that region, directly or indirectly are having point sources as waste substance though a small stream and non-point sources as runoff, which is mainly affects the quality of water and the availability of eggs and larvae diversity and developmental growth. An unaffected area is abundance of eggs and larvae to support the diversity of fishes. Should be avoid some of the pollute activities and need for species conservation and protection of the environment.