First recorded bloom of Navicula Bory in a mangrove habitat of Karachi

Discolouration of sands and other marine substrata caused by benthic diatoms have been reported by Aleem (1950) Eaton and Moss (1975), Sullivan (1980), Maple (1983), Navarro (1983) and Wah and Wee (1988). However, this is for the first time such a phenomenon is being reported from a mangrove habitat of Karachi. It was caused by a pennate diatom Navicula cancellata Donkin.

The marked reduction of the Indus river flow downstream from the Kotry barrage: can the mangrove ecosystems of Pakistan survive in the resulting hypersaline environment?

This report deals with the application of knowledge of mangrove ecosystems from around the world to the understanding of the present status of mangroves ecosystems in Pakistan.

Chemical constituents of the fruit and hypocotyl of mangrove, Ceriops tagal

The fruit and hypocotyl of Ceriops tagal were analysed for their organic and inorganic constituents. They showed almost similar characteristics in major metabolites and high molecular weight elements. Both the samples had high concentration of the carbohydrates and crude fibre and very low in fat and protein. The ash was rich in NA, K and Ca. Some essential free amino acids and sugars were also present. Calorific values were found fairly high. There is a strong possibility of using fruit and hypocotyl of C. tagal as a source for supplementing animal feed.

Salt-tolerance in mangrove soil bacteria

A total of sixteen bacterial species were isolated from mangrove soils of Karachi, Pakistan. Twelve of the isolates were gram positive while four were gram negative. All sixteen species showed resistance to high concentration of streptomycin, however, resistance to chloramphenicol and tetracycline was variable. The isolates tolerated up to 110‰ salinity and accumulated sodium form the media.

Studies of microbial abundances in mangrove habitat along the Karachi coast

Three species of bacteria, 8 species of fungi and 3 species of VAM-fungi were isolated from the soil substrata supporting Avicennia marina which comprises the majority of mangrove vegetation along the Karachi coast. The species abundances for fungi and bacteria were greater at one site (Sandspit) supporting healthy mangrove growth with soil pH 7.8, EC 16.2mmhos/cm², TSS 2.57% and available phosphorus 0.008% than at the other site (Korangi creek) with stunted growth of mangrove where the soil samples showed pH 7.9, EC 18.8mmhos/cm², TSS 1.45% and available phosphorus 0.001%. Symbiotic association by vasicular-arbuscular mycorrhizal (VAM) fungi in the roots of mangrove plants was also observed on a small scale at Korangi creek where the substratum was undergoing microbial degradation.

Larval development of a mangrove crab (Perisesarma bidens De Haan) (Crustacea: Brachyura: Sesarminae)

Larval development of Perisesarma bidens (De Haan) was investigated in laboratory conditions. Morphology of all larval stages and 1st crab stage was described and illustrated in detail, and compared with other species of sesarmid crabs. The zoeae morphological features of P. bidens are almost similar to other species of Sesarma in lacking a pair of lateral spines on carapace.

Effects of animal and plant protein diets on growth of Indian major carp (Labeo rohita Ham.) fingerlings

An experiment was conducted with Labeo rohita fingerlings in an indoor static fish rearing water system of glass made aquaria. Five experimental diets A, B, C, D and E were formulated containing 33% dietary protein level in five treatments each having two replicates containing 12 fingerlings of mean total initial weight of 13.00±0.2g. Sixty days of feeding trial in this experiment showed that fish fed on diet 'A' containing fish meal and diet 'E' containing mixed plant sources protein had significantly highest and lowest growth respectively. However, no significant difference of growth was found in fish fed on diets C and D containing meat and bone meal, and mix of animal protein source diets respectively. The result showed that the apparent protein digestibility (APD) of diets 'A' and 'E' had significantly best and least values respectively. Food conversion ratio (FCR) and protein efficiency ratio (PER) ranged between 1.37 to 2.17 and 1.38 to 2.18 respectively. On the basis of observed FCR and PER diets 'A' and 'E' produced significantly highest and lowest growth respectively.

The Sundarbans fishers coping in an overly stressed mangrove estuary

The fishing community of the Sundarbans are the human group most at home in the mud-slush-water-forest environment of this famous mangrove estuary. Their skills, knowledge, and technique have developed in response to a challenging environment. Yet, of the countless studies on the various aspects of this eco-region, there are exceedingly few that have studied the Sundarbans fisher in his/her ecological, historical and demographic context—as a key stakeholder in an environment under considerable stress. The present study seeks to reduce this lacuna a little. Its object is not merely to examine and analyse, but also to identify means, both tradition-based and innovative, which might contribute to protect the environment, improve economic conditions, and usher in people-based governance of resources.

Some problems and issues of sustainable management of mangrove ecosystems of Tamil Nadu, India

Mangrove, a tidal wetland, is a good example of complex land and water system whose resource attributes is neither fully understood from an ecological perspective nor valued comprehensively in economic terms. With increased ecological and social perception of the functions of wetlands, the utility and relative values will increase. The perception, however, varies from society to society. It must be recognized that mangrove forests differ greatly in local conditions and in their ability to produce a wide variety of economic products. What may be highly productive strategy for one country may have little meaning to its neighbor. Therefore, it becomes essential that from among diversity of potential uses of the mangrove environment, specific uses will have to be decided, and management plan developed on site, or area specific basis. It is therefore necessary to arrive at a balance between the views of the ecologists and economists on the management of mangroves. Biological conservation should encompass resource management in the sense that integrity of the biological and physical attributes of the resource base should be sustained and man-induced management practices should not alter an ecosystem to the extent that biological production is eliminated. Sustained yield management for food, fiber and fuel would serve to sustain local fisheries while generating new economic enterprises. This requires the recognition of mangrove environment as a resource with economic value, and managed according to local conditions and national priorities.

Effects of salinity and temperature on the larval development of a sesarmid crab Neosarmatium trispinosum Davie (Crustacea: Brachyura: Sesarmidae) from mangrove swamp in Okinawa Island, Japan

The larval development of the semiterrestrial sesarmid mangrove crab Neosarmarium trispinosum was studied under laboratory conditions at salinities 0-35%o and constant temperatures of 20-30°C. The larval development consists of five zoeal stages and a megalopa. Larvae survived to the first crab stage at salinities between 15 and 35%o with different percentages. At 0, 5 and 10%o, the larvae died within 12-18 hours without moulting to subsequent stages. The highest survival rate was recorded at 20-25%o and 25-30°C with shortest development duration to the first crab stage ranging from 24-28 days. At the highest salinity (35%o), survival rate was gradually decreased with increasing development duration. There were significant differences (Pmangrove swamp at the megalopa stage, where they spend the rest of their lives.

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.

Larval development of a semi terrestrial mangrove sesarmine crab Chasmagnathus convexus (Crustacea: Decapoda: Brachyura: Grapsidae) reared in laboratory

Four zoeal stages and one megalopal stage were identified in laboratory reared semiterrestrial mangrove sesarmine crab Chasmagnathus convexus. At an average salinity and temperature of 20±1% and 19.2±0.2°C, the megalopa was attained 24 days after hatching. Morphologically, the first zoae of C. convexz1s is very similar to those of other species of the genus Chasmagnathus as well as species of the genus Helice, in that view all share the following characteristics: lateral spine on the carapace, three pairs of setae on the posterior margin of the telson furca, one plus five setae on the endopod of the maxillule, and two plus two setae on the endopod of the maxilla. The differences between the first zoea and megalopa of and those of its congeners are discussed.

Population structure of the grapsid crab, Helice tridens latimera (PARISI) in the Taiho mangrove, Okinawa, Japan

Grapsid crab Helice tridens latimera inhabiting mangroves, seashores as well as muddy and rocky areas. Ovigerous females were observed from December to May. Juveniles appeared in July and from December to April. In the laboratory they reached 9.50 mm in carapace width 4 months after hatching. It is likely that spawning of this crab occurs throughout the year.

Design of refrigerated sea water plant for preservation of fish

To study the feasibility of employing refrigerated sea water on board fishing vessels for the preservation of fish, a pilot model has been designed, the details of which are presented in this paper.