Rediscovery of Philyra verrucosa Henderson, 1893 (Crustacea, Decapoda) from Karachi waters (northern Arabian Sea)

Philyra v. was established as a new species by Henderson in 1893 and later recorded by Alcock in 1896. A detailed description is presented.

A new deep-sea crab, genus Chaceon, from the Arabian Sea (Crustacea, Decapoda, Geryonidae)

The sixth nominal species of Chaceon to be recorded from the western Indian Ocean is named from a specimen collected off Somalia in 504-506 meters. Chaceon somaliensis, n. sp., resembles C. macphersoni (Manning and Holthuis, 1988) and differs from the other four species known from the area in having the dactylus of the walking legs dorsoventrally depressed. It differs from C. macphersoni in having slenderer legs, a smoother body, and a much deeper, evenly curved orbit.

Biochemical composition of zooplankton from the northern Arabian Sea

Zooplankton standing crop and proximate principals were estimated for 8 coastal and 13 oceanic stations of the northern Arabian Sea during March 1991. Biomass did not show any significant difference (p < 0.05) between coastal and oceanic waters. Protein was the principal biochemical component among proximate principals with an average value of 29.6% in coastal and 34.2% in the oceanic zone, suggesting that protein form a major metabolic reserve. Other components such as lipids and carbohydrate seem to be low in tropical zooplankton. The organic carbon and caloric density did not show significant correlation. Average caloric density was 2.5 k.cal super(-1). The average standing stock was 9.25 mg m super(-3) and 5.90 mg m super(-3) for coastal and oceanic water, respectively. Coastal region is more productive than oceanic region in terms of standing crop, as expected.

An illustrated key to the Malacostraca (Crustacea) of the northern Arabian Sea. Part 1: Introduction

The key deals with the Malacostraca from the northern Arabian Sea (22 degree 09'N to 10 degree N and 50 degree E to 76 degree E). It is compiled from the specimens available to us and those which are in the literature. An introduction to the class Malacostraca and key to the identification of subclasses, superorders and orders is given. Al the key characters are illustrated. Original references with later changes are mentioned. The key will be published in parts not necessarily in chronological order.

Portunus pulchricristatus (Gordon, 1931): an addition to crab fauna of Pakistan (northern Arabian Sea)

Portunus pulchricristatus (Gordon, 1931) is a rare species, to date we have obtained only three specimens, two males and a berried female which can be easily identified with the help of existing descriptions and illustrations. Brief account of the Pakistan material is given below. One male specimen (measuring 11.0 mm in carapace length) has been deposited in the National Museum of Natural History, Leiden (Reg.No.D.42393) the other two specimens housed in the Marine Reference Collection and Resource Centre (MRCC Cat. No.BRAC.491). The abbreviations used are cl. for carapace length and cb. for carapace breadth.

Three new records of mysids (Crustacea: Mysidacea) from the northern Arabian Sea

This paper with the systematic study of three species of mysids, collected by R/V "Dr. Fridtjof Nansen", which are new to the northern Arabian Sea. The three species described and illustrated are: Siriella affinis Hansen, Afromysis macropsis Tattersal and Acanthomysis quadrispinosa Nouvel.

Note on additional material of Neballa dahli Kazmi and Tirmizi, 1989 (Leptostraca: Crustacea) from Karachi (northern Arabian Sea)

The first leptostracans Nebalia dahli (Kazmi & Tirmizi, 1989) from the Arabian Sea in mangrove planktonic collection near Karachi were two males, the sex of the juvenile paratype could not be determined at that time. A brief description is given in this paper.

Tidal and sea level changes at Jeddah, Red Sea

Tidal and sea level changes during 1991 at a coastal station (Jeddah) in the central part of the Red Sea are investigated. Analysis shows higher sea levels in winter and lower in summer. The amplitude of change at Jeddah is above 50cm. Analysis of wind stress at Jeddah indicates an insignificant contribution of the cross-shore component, while a major part of the changes in the sea level can be accounted for by the long-shore component.

Application of a wind-driven barotropic model to simulate the seasonal circulation of the northern Arabian Sea

A two dimensional numerical barotropic model based on the depth-integrated equations is presented here. Sensitivity of the model is analyzed by using wind stresses of different months. Real wind data and actual bathymetry are used as an input to obtain the circulation patterns of the northern Arabian Sea during specific seasons. However, the model is also tested with constant depth for comparison. A number of numerical simulations are performed to study the combined effects of wind stress, bathymetry and basin geometry. Since the goal of this study is to simulate the circulation of the northern Arabian sea in accordance with the observed wind stress, therefore, wind stresses of different months like July (the peak os SW monsoon), October (the transition period from SW to NE monsoon), January (the peack of NE monsoon) and April (the transition period from NE to SW monsoon) are used to examine the circulation patterns. The results obtained are satisfactory in that they resemble known patterns.

Seasonal and spatial distribution of Chlorophyll a in the north Arabian Sea bordering Pakistan

The average integrated chlorophyll a values for a 30-m deep surface layer in the north Arabian Sea bordering Pakistan ranged from negligible amounts to as high as 0.53μg chl. a 1ˉ¹(15.9mg mˉ²) during the period January 20, 1977 to June 4, 1977. The values, in general, decreased offshore except for the westernmost part of the Makran shelf, where unexpectedly high values were recorded over deep water. Seasonal distribution showed very high values in January (northeast monsoon season) which, with a few exceptions, gradually decreased to very low values in May, and then increased in June. The January peak may be related to winter cooling of surface waters resulting in convection and the June peak to the onset of southwest monsoon season in May. Coastal water shallower than 30m showed no seasonality and were often sites of intense phytoplankton blooms.

Comparisons of open boundary conditions in a barotropic model of the northern Arabian Sea

These simulations are focused on the sensitivity of the barotropic ocean non-linear model to the various open boundary conditions (OBCs). Different OBCs from gradient to radiation condition are examined to determine the best result and help to choose the most appropriate OBCs. Since the interior points are changing with time both implicit and explicit forms are applied. The simulations showed that the interior flow is sensitive to changes in the OBCs and the results are highly dependent on the bathymetry of the area. When a constant depth (100m) is used, the circulation pattern with all OBCs is same. The best boundary conditions are Orlanski Radiation and its modified form. These boundary conditions produce identical adjustment in velocity and are determined to be satisfactory for both constant depth and actual bathymetry.

Recovery of a leucosid crab Nursia abbreviata Bell, 1855 from Arabian Sea fish

On two occasions Nursia abbreviata Bell, 1855 has been recovered from the stomachs of Batrochus grunniens (Linnaeus, 1758) caught with commercial fish. Nursia abbreviata has been previously recorded from Karachi by Alcock (1896). The present specimens afford the first subsequent record of the species from the region, and are represented by only two males recovered from fish stomachs. The only other species of the genus from Pakistan is N. Rubifera Muller, 1866 which is common in shore collections (Tirmizi and Kazmi, 1988). A brief description of the present material is given below.

An illustrated key to the Malacostraca (Crustacea) of the northern Arabian Sea. Part 2: Stomatopoda

The key deals with 40 stomatopod species belonging to 17 genera and 9 families. Each species is accompanied by illustrations of the key characters. For each species the first reporter is referenced. A schematic diagram is given explaining terminology.

On the use of different natural baits for sea-fishing in India

Rod and line, hand-line, trolling line and fish-traps are the different types of fishing gears wherein suitable fish baits are employed with a view to luring the catch. The coastal fishermen of India mostly use different types of natural fish-baits to catch fishes like Perches, Carangids, Sciaenids, Scombroids and Elasmobranchs. The reactions of the fishes caught to the different baits used are quite varied. Successful line fishing operations very much depend on the fish-baits. A detailed record of the variety of fishes caught, types of fishing and different baits used by the coastal fishermen of India has been made.

Trawling pull exerted by a trawler: a method of estimation from propeller dimensions and its comparison with sea measurements

The proper matching of the pull exerted by a trawler and the size of trawl is important for maximizing the catching efficiency. The available pull is more dependent on the propeller and its working conditions than the installed engine power. The normal practice is to directly connect net size to the installed power in the boat by formulae without reference to the prope1ler dimensions or the available trawling pull and this is not adequate to find out the optimum combination. By the method outlined in this paper, the accurate calculation of trawling pull is possible by taking into account only the propeller diameter, pitch and r. p. m. The predictions by the method are compared for trawlers with powers between 30 and 60 hp and agreement is found to be within + 5%. The power absorbed by the propeller in trawling condition can also be calculated by this method for checking whether the engine is being overloaded.