Brackish-water fishery resources

Ceylon has about 300,000 acres of coastal brackish-water areas of which about 100,000 acres constitute shallow lagoons, tidal flats, mangrove swamps and saline marshes, and the rest deeper lagoons and estuaries. While the former represent a vast potential resource with regard to fish farming, the latter are the sites of important fisheries. W. H. Schuster (1951) estimated the average natural production of Ceylon’s brackish waters to be less than 20 lbs. per acre per annum. Since then estimates have been made by the author for a rich lagoon, the Negombo lagoon, a poorly productive lagoon, the Ratgama lake (Dodanduwa) and studies are in progress of some of the other lagoons. The natural production of the Ratgama lake was estimated in 1959 to be 18.5 lbs. per acre per annum while that of Negombo lagoon was estimated in 1960 to be 65 lbs. per acre per annum. It is reasonable to estimate the average production of Ceylon's brackish-waters to be 25 lbs. per acre per annum. Thus the total production is about 3,350 tons per annum. Considering the fact that the island's present total production is 90,000 tons per annum, the brackish-waters contribute 3.7% of it. Schuster (1951) further states that the natural production in the brackish-waters of other countries is around 80 lbs. per acre per annum. In order to increase our average natural production to this value it would seem necessary to consider the nature, biology and fish resources of the brackish-waters and draw some conclusions with regard to their proper exploitation.

Growth of Tilapia mossambica Peters in different salinities

Tilapia mossambica was found to grow better in saline media than in freshwater. The fish not only grew to maturity but were able to reproduce viable fry in 100% sea water.

Salt and water balance in the Mundel Lake: a strongly choked coastal lagoon

The Mundel Lake is an extremely shallow lagoon on the west coast of Sri Lanka. It is connected to the Puttalam Lagoon through 15 km long Dutch Canal. Salinity measurements and daily sea level data were obtained fortnightly from January 1993 to March 1994 and they were used to quantify the salt and water budget along with precipitation, evaporation and freshwater runoff. Extreme fluctuations of salinity and sea level are striking features of the system. Salinity of the Mundel Lake and Dutch Canal varied from 5-46.5 and 6 61 ppt respectively while the sea level ranged from -0.25 to +1.2 m. Tidal variations were not seen in the lagoon due to its long narrow canal system. Salt budget showed that the deposition of salt on the lagoon bottom during periods of decreasing water level. During increasing water level, salt is dissolved again. Flow of water through the Dutch Canal between the Puttalam Lagoon and Mundel Lake is driven by the changes in sea level. These changes are mainly due to seasonal changes of net freshwater supply and, to a lesser degree, to seasonal changes in sea surface height. As the flow rates are small due to the long and narrow canal, the residence time ranges between two months and several months in the Mundel Lake, except during season of high freshwater supply. As the water exchange is weak, the Mundel Lake becomes hyper saline with strong fluctuations in salinity. This implies a stress to all lagoon dwelling aquatic organisms and also to aquaculture practices in the area.

The potential of mixed culture of freshwater giant prawn Macrobrachium rosenbergii de Man and tiger shrimp Penaeus monodon Fab. at Khulna region, Bangladesh

The freshwater giant prawn (golda), Macrobrachium rosenbergii and tiger shrimp (bagda), Penaeus monodon were stocked together with or without fin fishes at different stocking rates in semi-saline waters at Khulna region and their growth, survival, yield and costreturn analysis were made. Survival rate of golda and bagda ranged from 23.0 to 36.8% and 8.2 to 24%, respectively. The both species were significantly affected by their own stocking density. The average final weight of golda and bagda ranged from 62.4 to 73.3 g and 32.0 to 66.4 g. The bivariate analysis of average final weight of both golda and bagda revealed that golda positively and bagda negatively influenced by the total stocking density. However, the results of the individual sizes of both golda and bagda showed an increase in the proportions of smaller animals and a decrease in the proportion of larger ones with increasing stocking rates. The harvesting weights of all animals in the experimental ghers were in marketable sizes although their prices varied with the individual size. The total production comprised of both golda and bagda ranged from 514.6 to 952.8 kg ha·1, over a culture period of 10 months. Return on investment ranged from 51.0 to 125.7%.

Pond production of Artemia in Pakistan

Currently our government and the private sectors are very much interested in the establishment of marine aquaculture. For the successful operation in aquaculture of finfishes and shellfishes, the basic requirement is the suitable diet, apart from proper environment. For the larvae, juveniles and adult stages of the culturing organisms the live Artemia is the ideal food. The aquaculturists the worldover are using live food for their culturing organisms, as the live food played an important role in the dietary management of aquaculture of finfishes and shellfishes (Sorgeloos and Kulasekarapandian, 1984), particularly during larval stages. The live nauplii of Artemia are used in aquaculture of finfishes and shellfishes due to being nutritionally balanced, non polluting, economically bearable, viable and readily acceptable to the culturing species. The adult Artemia is also used for feeding the aquarium fishes particularly so when there is a clear abundance of this resource which is cheaper and can economically compete with alternative artificial diet. By the use of Artemia the aquaculturists may obtain optimum growth and survival rate of the organisms. The life cycle of Artemia is very short, which is completed within two weeks especially during dry season in highly saline waters, the two weeks old Artemia starts producing cysts. These cysts become ready to harvest within a week.

The first antimicrobial peptide from sea amphibian

The crab-eating frog, Rana cancrivora, is one of only a handful of amphibians worldwide that tolerates saline waters. It typically inhabits brackish water of mangrove forests of Southeast Asia. A large amount of antimicrobial peptides belonging to different families have been identified from skins of amphibians inhabiting freshwater. No antimicrobial peptide from sea amphibians has been reported. In this paper, we firstly reported the antimicrobial peptide and its cDNA cloning from skin secretions of the crab-eating frog R. cancrivora. The antimicrobial peptide was named cancrin with an amino acid sequence of GSAQPYKQLHKVVNWDPYG. By BLAST search, cancrin had no significant similarity to any known peptides. The cDNA encoding cancrin was cloned from the cDNA library of the skin of R. cancrivora. The cancrin precursor is composed of 68 amino acid residues including a signal peptide, acidic spacer peptide, which are similar to other antimicrobial peptide precursors from Ranid amphibians and mature cancrin. The overall structure is similar to other amphibian antimicrobial peptide precursors although mature cancrin is different from known peptides. The current results reported a new family of amphibian antimicrobial peptide and the first antimicrobial peptide from sea amphibian. (c) 2007 Elsevier Ltd. All rights reserved.

Bacillus solisalsi sp nov., a halotolerant, alkaliphilic bacterium isolated from soil around a salt lake

A novel Gram-positive, motile, rod-shaped bacterium isolated from a saline soil in China was characterized by a polyphasic taxonomic approach. The strain, designated YC1(T), was halotolerant [tolerating up to 15 % (w/v) NaCl] and alkaliphilic (growing at

Socioeconomic assessment of shrimp farming in relation to local livelihoods in the south-west coastal Bangladesh

Nine different categories of stakeholders in shrimp farming industry ·were assessed to show the socioeconomic impact of shrimp farming in south-west Bangladesh. Among all the stakeholders the shrimp farmer's average own land was 4 ha whereas the seed collectors and faria's had lowest amount of average land, 0.1 and 0.5 ha respectively. The shrimp farming positively impacted to the livelihood of stakeholders. Income of the coastal people, sanitation, working facilities of women, employment, health condition and the literacy rate increased due to shrimp farming. On the other hand shrimp farming had negative impact on the rice production, livestock, drinking water supply, and social conflict and violence had increased due to shrimp farming. There were internal conflicts between different stakeholders; the farias conflict with the depot owners and shrimp farmers, marginal farmers' conflict with the rich shrimp farmers about leasing lands and saline water control, the rice farmers conflicts with the shrimp farmers about agricultural crop production.

Salinity and survival of Martesia striata (Linn) in Cochin harbour

The effects of salinity variations on the survival of Martesia striata from Cochin harbour are presented. It is observed that at least a few of the animals survive the low saline conditions during monsoon. Laboratory experiments showed the lethal salinity as 6‰ when animals acclimatised in 34‰ were subjected to abrupt changes in salinity. But acclimatisation to 17‰ salinity showed a downward shift in the lethal salinity to 4‰. The present observations indicate that M. striata is euryhaline arid the extent of tolerance to lower salinities depends on the degree of acclimatisation.

Studies on the occurrence and growth rates of two intertidal fouling bryozoans in the Mattancherry channel of Cochin harbour, south-west coast of India

Occurrence and growth rates of two species of intertidal fouling bryozoans namely Electra bengalensis (Stoliczka) and Electra crustulanta (Pallas) are presented in this paper. The former was a typically marine form, settling on panels only during the high saline conditions of the pre-monsoon period and were absent during the low salinity conditions of the monsoon period, while the latter appeared to be a typical brackish water form settling on panels during the low saline conditions existing during the monsoon and post-monsoon periods and were totally absent during the pre-monsoon months. Regression co-efficient of the former was higher than that of the latter suggesting more pronounced growth in Electra bengalensis. Maximum growth for this species was noticed during March, April and May (pre-monsoon) while for the other species growth was more or less similar during monsoon and post-monsoon months (June-January) showing that the species was at home in oligohaline and mesohaline waters.

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.

Selection of suitable diluents for bacteriological examination of fishery products

For raw, iced and frozen samples of fish and prawn, significant difference was observed in total plate counts done with various diluents, the significance level ranging from 5% to 0.1%. For raw fish, N-saline, seawater and quarter strength Ringers' solution gave maximum total plate counts. In the case of iced-fish, n-saline yielded highest total plate counts. For frozen samples, however, peptone water and n-saline gave good recoveries. Trials with suitable combinations of diluents showed that though some of them were as good as the control, namely n-saline, none were superior in any way.

The effect of salinity on some endocommensalic ciliates from shipworms

The ciliates, Nucleocorbula adherens, Boveria teredinidi, Trichodina balakrishnia, Thingmozoon fencheli and Nyctothereus marina, live inside the mantle cavity of the shipworms in the estuaries and backwaters of the south-west coast of India. Seasonal incidence and relative abundance of these ciliates showed that they were more abundant during the low saline than the high saline periods. Even though these ciliates can endure higher salinities through gradual acclimatization of their habitat it was found that they prefer low salinity for active growth and healthy existence.

Observations on the fish and prawn seed resources of the Gulf of Kutch and their utilization in aquaculture

The characteristics of the fish and prawn seed resources of the Gulf of Kutch are described. Results of experiments conducted in a primary low saline reservoir of a solar salt works to study their utility for aquaculture are reported. The prospective role of aquaculture in augmenting fish production along the coast is also discussed.

Effects of extremely low-frequency electromagnetic fields on morphine-induced conditioned place preferences in rats

In the present study, we examined the effects of extremely low-frequency (ELF) electromagnetic fields on morphine-induced conditioned place preferences in rats. During the conditioning phase (12 days), three groups of rats were placed in a sensory cue-defined environment paired with morphine (10 mg/kg, i.p.) following exposure to either 20 Hz (1.80 mT) or 50 Hz (2.20 mT) or sham electromagnetic fields for 60 min/day, respectively, and were placed in another sensory cue-defined environment paired with physiological saline (1 ml/kg, i.p.) without exposure to electromagnetic fields. After finishing 12 days of conditioning, preference tests for the morphine-paired place were performed during a 10-day withdrawal period. The exposure to electromagnetic fields substantially potentiated morphine-induced place preferences in rodents, suggesting that ELF electromagnetic fields can increase the propensity for morphine-induced conditioned behaviors. (C) 2005 Elsevier Ireland Ltd. All rights reserved.