Early developmental stages of two Secutor species (Family: Leiognathidae) collected from the Bak-khali river estuary of the Bay of Bengal, Bangladesh

Early developmental stages of two Secutor species, Secutor insidiator (Bloch) (11.9-36.0 mm standard length, SL) and Secutor ruconius (Hamilton-Buchanan) (14.0-33.0 mm SL) collected by ichthyoplankton net from the Bak-khali river estuary of the Bay of Bengal, Cox's Bazar, Bangladesh are described and illustrated. All of the fins with supporting spines and rays were present in the smallest collected sizes of both species. With growth of the specimens, significant changes in melanophore patterns were found. S. insidiator is similar to S. ruconius in having upward protracting mouth parts and body colouration, but can be distinguished easily by its more elongate body shape (body depth 38-47% of SL compared with 46-52% of SL in Secutor ruconius). Both the species occurred round the year from August 1998 to July 1999. The surface water temperature and salinity during the study period varied from 22.0-32) C and 10-37 ppt respectively.

Distribution of mercury in a tropical estuary (India) situated near a chloro-alkali plant

The distribution of mercury in water, sediment and some biological samples of the Rushikulya estuary, east coast of India were assessed during Jan-Dec. 1989. Both the dissolved plus acid leachable mercury contents in water and the sediment mercury discerned conspicuous spatial and seasonal fluctuations. Adsorption on to the suspended particulates was found to be the most likely mechanism for removal of mercury from the water column. Exchange of mercury from sediments to water was observed at high salinities (20-30x10-3). The residual mercury contents in the biological samples revealed that bio-accumulation by bottom-dwelling organisms are higher than the pelagic components.

Growth and reproductive performance of locally isolated brackish water rotifer (Brachionus plicatilis) feeding different micro algae

Population growth and reproductive capacity of brackishwater rotifer, Brachionus plicatilis, were evaluated, for a period of 8 days in a temperature controlled ( =25°C) microalgallaborarory, under three different algal feeding regimens. The algal species that were tested are: (i) Chlorella sp. (T1), Tetraselmis chui (T2), Nannochloropsis oculata (T 3). The feeding density of each algal species was maintained similar as of 4.5xW6 ceHs mi. The rotifer fed on T. chui showed the highest (p<0.05) population growth (131.5 ind./ml), compared to that fed on Chlorella sp (45.67 ind./ml) and N oculata (43.44 ind./ml). The abundance of egg bearing rotifers was also higher (35.77%) with T. chuithan with Chlorella sp (27.76%) and N oculara (24.60%). The results of the present study indicate that T. chui could be the most suitable algal food for the stock culture of locally isolated rotifer B. plicatilis.

Notes on the fish resources of the Bahuda estuary, Orissa, India

Estuaries form an important site for the zoologist as these are the places known to be very rich in food and nutrients and so, become nesting-cum-breeding grounds for many species and also, own good species diversity. Bahuda estuary of Orissa is located at the inter-state border of Orissa and Andhra Pradesh. Explored for many invertebrates, this estuary was not properly investigated for its rich fish fauna. Various surveys at Bahuda estuary revealed that it is an important site of study for the faunal diversity of fishes in the east coast. Forty-eight species belonging to 33 genera under eight orders and 22 families were examined referring standard literature· and methods. Most of the groups of fishes encountered are of commercial importance.

Emigration dynamics of three species of penaeid prawn from backwaters and tidal ponds of Cochin, India

Emigration of three species of penaeid prawn from backwaters and tidal ponds were studied. Considerable diel, tidal, lunar and seasonal fluctuations were observed in emigration process, which was almost nocturnal. Rate of emigration and composition of emigrants varied with time of migration. Large pulses of emigration always coincided with spring tides with major peak during new moon. Seasonal variation was observed with peak emigration of Penaeus indicus during monsoon months and that of Metapenaeus dobsoni and Metapenaeus monoceros during pre-monsoon. Rate of emigration was relatively large from shallow tidal ponds. It correlated directly with the prevailing environmental conditions and juvenile density. Instantaneous rate of emigration was also large in seasonal ponds. The basic stimulus for emigration is the urge for sexual maturation. Coupled with it ecological changes in the habitat have been causing various patterns in migration.

Phytoplankton diversity and primary production in Poonthura estuary, south Kerala

Seasonal variations in the phytoplankton density, diversity, gross production and related physicochemical parameters of Poonthura estuary have been followed for a period of one year. The polluted nature of the water body favored a higher density of phytoplankters, which exhibited a positive correlation with gross production. The influence of various physicochemical parameters, phytoplankton density and species diversity on gross production is discussed.

Estimation of micro-flora associated with different stages of Macrobrachium rosenbergii (de Man)

The bacterial flora occurring in muscle, haemolymph, hepatopancreas and gill of brood, juveniles, water, eggs, larvae and rearing water were estimated by selective plate count technique for Entrobacteriaceae, Streptococaceae and Vibrionaceae members. The total viable bacterial count was estimated by total plate count technique on nutrient agar. The total viable counts of bacteria were lowest in water from 6.10x10² CFU/mL) and highest in egg (6.06x10super(8) CFU/g). In brood the total counts were varying from 1.62x10² CFU/g in muscle to 2.20x10super(5) CFU/g in gills. In juveniles, the total plate counts were varying from 2.8x10super(4) CFU/g in muscles to 3.67x10 super(8) CFU/g in hepatopancreas. Selective plate counts show that Enterobacteriaceae members dominate in egg and gills of brood and hepatopancreas of juveniles. Vibrios were found to be dominant in water and larvae of rearing tank. Haemolymph of brood was sterile and did not contain any bacteria while muscle of juvenile was having very low count of total viable bacteria.

Observation on the lunar and tidal influence on gill netting in the Bay of Bengal

The effect of lunar and tidal influence on the landing of pelagic fish with drift gill nets has been studied for the first time from Bay of Bengal along the Orissa coast. The catchability of the gear was highest during the first quarter and lowest in the fourth quarter of the moon. The variation in catch rates during the four different quarters was not statistically significant. Contrary to the earlier belief, landing with gill net was not poor during the moonlit nights. The extensive use of bluish grey nylon twine matching with seawater in place of indigenous hemp or cotton twine, has largely eliminated the visibility of gear during the brighter phase of the moon. The rate of exploitation was found to be significantly higher during the nights of neap tide, compared to those of spring tide. A plausible explanation for this phenomenon has been offered.

The characteristics of distribution and change of the seawater temperature and salinity of Cai river estuary and Northern Part of Nha Trang bay in the dry and rainy season

In this paper, some results of analyzing the hydrographic characteristics of the seawater temperature and salinity are presented. The received results showed that: in dry season, the influence of the Cai river water has is limited in Cai river estuary with the approximate transferable distance from the river mouth to the open sea of about 1 km. The isohaline 32%o could be defined as the separate boundary of the Cai river water; In rainy season, due to the river water discharges are high, the influence of Cai river water could be transferred to the open sea and island areas. The immerge of the Cai river water in the open sea areas in rainy season has changed the vertical structure of salinity and temperature in the northern part of Nhatrang bay. In both seasons, the Cai river water have influenced in the surface water layers 0 - 2m and the water layers deeper than 2m are influenced by the sea waters with the salinity of higher than 32%o.

Preliminary observations on the lunar and tidal influences on the catches of seer by gill nets

The paper deals with the lunar and tidal influences on the catches of seer by gill nets. The landings during full moon and new moon nights, during low and high tides and during different quarters of the lunar month for three fishing seasons are discussed.

Biology of fouling in Neendakara port, a tropical estuary in the south west coast of India

Species composition and some aspects of the biology of the fouling community in Neendakara port (southwest coast of India) has been examined for a period of one year. Fouling organisms were collected with a system of glass panels exposed for varying durations and during different months in the port. One species of sponge, nine species of coelenterates, thirteen species of polyzoans, four species of mud-tube dwelling polychaetes, four species of serpulids, one species each of mud-tube forming amphipod and tanaid, two species of oysters, six species of mussels and not less than eight species of tunicates were the macro fouler which settled over the panels. Monthly and seasonal settlement of the different species has been recorded. Fouling has been a continuous process occurring throughout the year in Neendakara port with slightly fluctuating biomass and considerably varying species composition. Alternate species dominance of marine and brackish water forms has been an important feature of fouling in the area. Number of species of the sedentary fouling animals represented on test panels has been high during the highly saline pre-monsoon period and low during the monsoon period.

A programme to carry out analysis of variance: two-way classification on Micro 2200

A brief description is given of a program to carry out analysis of variance two-way classification on MICRO 2200, for use in fishery data processing.

Observations on the ingression and distribution of larval prawns in the Nethravati-Gurupur estuary, Mangalore

The spatial and temporal distributions of larval prawns of penaeids and non-penaeids in the estuarine waters of Mangalore were studied. Larvae appear to be passively brought in by the incoming flood tides to the estuary, enjoy a wider distribution throughout the estuarine complex with abundance towards the mouth. The distribution of larval prawns was more in Nethravati than in the Gurupur stretch. The influence of temperature, hydrogen-ion-concentration, salinity and dissolved oxygen on the distribution of larvae in the estuaries is discussed. Inference on spawning seasons of commercially important prawns in the neighbouring waters has been arrived at based on their larval abundance.

Ingression, abundance and settlement dynamics of Penaeid chrimp postlarvae in backwaters and adjacent tidal ponds in Cochin, India

Dynamics of penaeid postlarval ingression and settlement in the backwaters of Cochin were studied. Postlarval recruits were constituted by Metapenaeus dobsoni (70.8-78.4%), Penaeus indicus (17.5-24.6%), M. monoceros (3.8-4.6%) and P. monodon (0.3-0.4%). Their composition varied with location and season. Postlarval abundance and ingression were influenced by diel, tidal, lunar and seasonal factors. Ingression is mainly nocturnal in all species with nearly 84% of the activity during night hours. Abundance and ingression peaked up during high tides at night with major peaks coinciding with spring tides of full and new moon. It also followed a generalized seasonal pattern with two well-defined peaks for all species. It was pre-monsoon followed by post-monsoon for P. indicus and M. monoceros and post-monsoon followed by pre-monsoon for M. dobsoni. Sizes of the recruits were relatively small during pre-monsoon and post-monsoon and large during monsoon.

Diversity, abundance distribution and secondary production of intertidal and subtidal benthic macrofauna of Bushehr Province with emphasis on annelida groups

The present investigation was undertaken to establish a reference situation for future use, to identify temporal and spatial composition of macrofauna and estimate some ecological indices in the sub tidal waters along the Bushehr coastal waters in Persian Gulf. Six transects were selected including Genaveh, Farakeh, Shif, Bandargah, Rostami and Asalouyeh, at each transect 3 station were sampled in depths of zero, 5 and 10 metres. Sampling was seasonally carried out by a VAN VEEN grab 0.0225 m2, during summer 2008 until spring 2009. Samples were wet sieved immediately using 0.5 mm mesh size sieves and sediment retained in the sieve was preserved in 4% buffered formalin solution. Macrofauna specimen were separated from the sediments using decantation and elutriation methods, enumerated and identified up to the Genus level. Environmental factors such as temperature. pH, and salinity were recorded in field using sensitive probs and refractometer (for salinity) and also sediment samples were taken for TOM and grain size analysis in all the stations. 5611 specimens belonging to 66 genera were collected during the present study. Polychaetes were dominant both in terms of genus number (31) and relative abundance (74 % of total macrofaunal abundance). The other dominant groups were Artheropoda, (16.1%), Molusca (2.8%), Echinodermata (1.29%) and others including Nematoda, Nemertina, Echiura and Turbellaria (5.8%). Thirty one Genera belong of 27 families of polychaeta, one genus and family of Subphylum Chlicerata,19 genera belong to 14 families of Crustacea, 8 genera belong to 6 families of Molusca, were indentified in the studied region. 1 family (Polygordidae) and 3 genera (Flabeligera, Pilargis and Polygordius) of Polychaeta, 1 family (Nymphonidae) and genus (Nymphon) of Chelicerata, 1 Family (Nematoplanidae) and genus (Nematoplana) of Turbellaria, were identified for the first time in Persian Gulf area. The result indicated that macrofauna organism have strong relationship with the grain size characteristics of the sediments they inhabit. The most surface deposit feeder specimens such as Prionospio and Cossura were found in zero meters depth of Genaveh, Farakeh, Bandargah, Rostami and Asalouyeh stations with sandy substratum, however the most burrowing deposit feeder and scavenger specimens such as Capitella and Petaloproctus were collected in 5 and 10 meter depths of stations with silty–clay substratum. The annual mean abundance, Shanon- weiner diversity and evenness of macrofauna were estimated1152.73 N/ m² , 2.72 and 0.792 respectively .The annual average biomass and secondary production were computed 1.797 gDW m² and 3.594 gDW m² y-1 .The average of water temperature, salinity, pH and oxygen concentration were recorded between 16.37-36.05 °C, 38-42 g/l, 7.89-8.76 and 4.23-8.23 mg/l, respectively during this study in 6 studied region. Among of investigated stations Asalouyeh adjacent of effluent canal of Gas and petrochemical industry sewage and Farakeh regions adjacent the Helleh estuary had the lowets and the highest community indices. The average of diversity and density in 5 meters depth stations with moderate of sand, silt and clay were slightly more than 2 other depths stations, it seems that 5 meters stations are made a transition habitats between 2 sandy and clay habitats, that can be used by 2 groups of surface and borrowing deposit feeders. Based on the data provided in this survey, the temperature variation, sediment texture, TOM, type habitat and manmade factors of Gas and petrochemical industries have had the most effect on the macrofauna community structure in the studied region during sampling periods.