A study on length-weight relationship, food and feeding habits of Indian scad, Decapterus russelli (Ruppel, 1830) along the northwest coast of India

Length and weight relationship of Decapterus russelli (Ruppell, 1830) is worked out to be W = 0.00312 L³ which indicates the isometric growth of the fish. Study on food and feeding habits revealed that the species is carnivorous, pelagic, feeding primarily on small crustaceans and small fish species, viz. Acetes indicus, ostracods, Apogon sp., Leiognathus sp., sciaenids, Netnipterus japonicas, Myctophid sp., Trichiurus sp., Therapon sp., D.russelli and occasionally on prawns. It is a selective feeder on Aeetes indicus.

Stock assessment of soldier catfish Osteogeneiosus militaris along the northwest coast of India

Value of length growth parameters L∞, K and t(sub)0 from age-length relation obtained from length-frequency analysis for the soldier catfish stock were estimated to be 47.6 cm, 0.51 per year and 0.03 year respectively. The age at recruitment (t [sub]r) was 0.58 year and the age at first capture (t[sub]c) 0.83 year. The total mortality (Z) was 0.88 including the present natural mortality (M) of 0.84 and fishing mortality (F) of 0.04. The total stock of this fish along the Northwest coast of India was assessed to be 32,413 tons and the MSY 5,426 tons which is much higher than the current catch of 863.8 tons. The potential yield (P[sub]y) of 38.7 g per recruit could be obtained at the optimum of exploitation (t[sub]y) of 2.84 years.

Assessment of Saurida tumbil (Bloch) stock in the northwest continental shelf water of India

Based on the data collected from New Ferry Wharf, Sassoon Dock and exploratory survey of MFV Saraswati on the Northwest coast of India, the growth, mortality, population and stock parameters of Saurida tumbil is reported in the present communication. The Von Bertalanffy growth function (GF) parameters for growth on length were found to be L∞=49.8 cm, K=0.96/year, t0 = -.141 year. The length at recruitment (lr) is 80 mm. (tr=.167 year) while the length at first capture (lc) for the commercial trawl fishery is 100 mm (tc=0.25 year). The annual fishing mortality coefficient (F) for 1983-85 was 0.43, the natural mortality coefficient (M) was 1.33 and the exploitation ratio (E) was 0.25. The yield per recruit (Y/R) attained the maximum of 54.99 g at F=1.091 for E=0.45 for the present tc at 0.25 year. The annual total stock (P) and standing stock (P) in the exploitation portion at the inshore grounds to a depth of about 50 m were estimated to be 12,811 tons and 6,034 tons respectively. The average annual yield of 2,635 tons at the present F=0.439 (E=0.247) was less than the maximum sustainable yield (MSY) for 3,331 tons attainable from the inshore grounds at E=0.45.

Stock dynamics of horse mackerel, megalaspis cordyla (Linnaeus) along northwest coast of India

The stock dynamics of horse mackerel, Megalaspis cordyla, along the northwest coast of India has been studied using length frequency data recorded from commercial landings and trawl catches of research-cum-training vessel M.F.V. Saraswati. The growth parameters for this species has been estimated to be L∞=54 cm and K=0.49 per annum. The natural and fishing mortality for the stock have been worked out to be 0.93 and 0.91 per annum respectively. The study indicated that the stock is fished at a safer fishing mortality level F sub(0.1), lower than F sub(msy) level.

Stock assessment and biology of Johnius glaucus (Day) off the northwest coast of India

The stock size and biology of Johnius glaucus (Day) resource off the northwest coast of India were studied for 1982-83 and 1983-84. The total length at the end of 6, 12, 18, 24 and 26 months was 121 mm, 183 mm, 237 mm, 261 mm and 264 mm respectively. The length growth parameters were: L∞=300 mm, K=0.0807 (monthly) and t(sub)0=-0.51 month. The weight growth parameters were: W∞= 317g, K=0.0762 (monthly) and t(sub)0= -0.41 month. The exploited stock mainly composed of 1/2 + and 1+ age groups. The annual Z, M and F were 2.34, 1.49 and 0.85 respectively. The l(sub)b, t(sub)b, l(sub)r, t(sub)r and selection factor K were 155 mm, 0.75 year, 65 mm, 0.25 year and 3.875 respectively. The Yw/R was optimum at the exploitation rate (E) of 0.75 and coded mesh size of 37 mm. The total stock for 1982-83 and 1983-84 was 14,624 and 26,190 tons respectively. The standing stock of 1982-83 and 1983-84 was 5,645 and 10,110 tons respectively. The MSY for 1982-83 and 1983-84 was 6,623 and 11,788 tons respectively. The F and Z were lowest in 0+ age group and highest in 1+ age group.

Evaluation of heavy metals along the Mediterranean coastal waters of the Nile Delta region, Egypt

This work focuses on four marine sites in the Mediterranean Sea around the Nile Delta, Egypt. Surface water samples were collected seasonally during 2003. The concentrations of some heavy metals in dissolved form (Fe, Mn, Zn, Cu, Ni and Pb) are evaluated. The levels of heavy metals in the coastal waters were 11.92-30.4512µglˉ¹ for Fe; 5.79-17.36 µglˉ¹ for Zn; 0.30-0.83µglˉ¹ for Cu; 0.51-2.90µglˉ¹ for Ni and 0.53-10.31µglˉ¹ for Pb. These are compared, with sites in the estuaries and outlets of the Nile Delta. Fe (19.72-60.33µglˉ¹); Mn (12.63-35.60µglˉ¹); Zn (2.67-22.00); Cu (0.56-1.67µglˉ¹); Ni (1.43-3.73µglˉ¹); Pb (1.72-59.7µglˉ¹). The results showed a remarkable decrease in the concentrations of different heavy metals with increased salinity. Comparing the present data with the minimal risk concentration reported by WQC, the distribution of heavy metals was significantly lower in coastal sea water of the Mediterranean Sea off Egypt. The study indicated also that the average contents of Ni and Pb are slightly high in the area of water exchange than those reported by WQC.

Mineralogical variations and physical properties of deep sea sediments, northwest Arabian Sea

Charles Darwin the research ship undertook an Oceanographic Cruise in 1986, CD 86/17 of the North Arabian Sea. Sediment cores were collected between 15° and 25°N. In this study sediment cores collected from deep Indus and Oman basins (CD 1715, CD 1730, CD 1738) have been analyzed for mineralogy, water content and porosity. In general, the cores are mainly composed of clay to silt sized terrigenous and biogenic constituents. Quartz, Chlorite and Illite are the common minerals of Arabian Sea sediments. Porosity determined by water content of sediments has been correlated with quartz/chlorite and quartz/illite peak ratios to show a relationship between mineral composition and physical properties.

Influence of dew on biomass and photosystem II activity of cyanobacterial crusts in the Hopq Desert, northwest China

Dew is an important water source for desert organisms in semiarid and arid regions. Both field and laboratory experiments were conducted to investigate the possible roles of dew in growth of biomass and photosynthetic activity within cyanobacterial crust. The cyanobacteria, Microcoleus vaginatus Gom. and Scytonema javanicum (Kutz.) Born et Flah., were begun with stock cultures and sequential mass cultivations, and then the field experiment was performed by inoculating the inocula onto shifting sand for forming cyanobacterial crust during late summer and autumn of 2007 in Hopq Desert, northwest China. Measurements of dew amount and Chlorophyll a content were carried out in order to evaluate the changes in crust biomass following dew. Also, we determined the activity of photosystem II(PSII) within the crust in the laboratory by simulating the desiccation/rehydration process due to dew. Results showed that the average daily dew amount as measured by the cloth-plate method (CPM) was 0.154 mm during fifty-three days and that the crust biomass fluctuated from initial inoculation of 4.3 mu g Chlorophyll a cm(-2) sand to 5.8-7.3 mu g Chlorophyll a cm(-2) crust when dew acted as the sole water source, and reached a peak value of approximately 8.2 mu g Chlorophyll a cm(-2) crust owing to rainfalls. It indicated that there was a highly significant correlation between dew amounts and crust moistures (r = 0.897 or r = 0.882, all P < 0.0001), but not a significant correlation between dew and the biomass (r = 0.246 or r = 0.257, all P > 0.05), and thus concluded that dew might only play a relatively limited role in regulating the crust biomass. Correspondingly, we found that rains significantly facilitated biomass increase of the cyanobacterial crust. Results from the simulative experiment upon rehydration showed that approximately 80% of PSII activity could be achieved within about 50 min after rehydration in the dark and at 5 degrees C, and only about 20% of the activity was light-temperature dependent. This might mean that dew was crucial for cyanobacterial crust to rapidly activate photosynthetic activity during desiccation and rehydration despite low temperatures and weak light before dawn. It also showed in this study that the cyanobacterial crusts could receive and retain more dew than sand, which depended on microclimatic characteristics and soil properties of the crusts. It may be necessary for us to fully understanding the influence of dew on regulating the growth and activity of cyanobacterial crust, and to soundly evaluate the crust's potential application in fighting desertification because of the available water due to dew. (C) 2009 Published by Elsevier Ltd.

Factors affecting leaf morphology: a case study of Ranunculus natans C. A. Mey. (Ranunculaceae) in the arid zone of northwest China

In order to examine the role of environmental factors affecting foliar morphology, we performed a case study of leaf morphological variation of Ranunculus natans found in the arid zone of northwest China. We found that foliar phenotypic variation differed significantly between populations. We described substantial positive correlations between altitude and leaf area (LA) as well as leaf perimeter (LP), and also between longitude and number of teeth, along with dissection index (DI). The pH, conductivity, and salinity of the environment caused a significant decrease in both LA and LP. Ranked in terms of their impacts on leaf morphology, the six selected factors were: altitude > pH > conductivity > salinity > longitude > latitude. We found that foliar morphological variations are functional responses to water-quantity factors (e.g., altitude and longitude at regional scales) and water-availability relation factors (e.g., pH, conductivity, and salinity at local scales), rather than to temperature-relation factors (latitude). Therefore, altitude and longitude, along with pH, conductivity, and salinity, are the main factors that significantly influence foliar morphology in the arid zone of China. We found that main factors played major roles in plant phenotypic plasticity in a complex ecosystem, although different combinations and interactions of environmental and geographical factors in each local environment may obscure the general trends in trait changes along environmental gradients.

Triplophysa waisihani, a new species of nemacheiline loach from Northwest China (Pisces: Balitoridae)

Triplophysa waisihani, a new species of nemacheiline loach, is described from the Kax River, a tributary of the Ili River drainage in Xinjiang-Uighur Autonomous Region of Northwest China. It can be assigned to the T. labiata species group characterized by having widely separated anterior and posterior nostrils and no breeding tubercles on the sides of the head. Triplophysa waisihani resembles T. labiata and T. herzensteini, but differs from both in cephalic sensory-canal pattern and the structure of the gas bladder; from T. labiata in the structure of the pelvic girdle and absence or presence of the fourth basibranchial; and from T. herzensteini in the shape of the anal fin.

Testate amoebae (Protozoa : Rhizopoda) from northwest Yunnan, China

A survey of the testate amoebae of northwest Yunnan in the Hengduan Mountains region of southwest China revealed 151 species belonging to 29 genera. Of these, three genera and 27 species were new to the testate amoebae fauna of China. The widely distributed and dominant species were Centropyxis aculeata aculeata, C aerophila aerophila, C. sylvatica, Difflugia elegans, D. globulosa, D. pristis, D. pulex, Phryganella hemisphaerica, Trinema enchelys, and T lineare. The most diverse genera were Difflugia (41 species), Centropyxis (31 species), Arcella (18 species), and Euglypha (11 species). The number of species in each sample varied greatly. It appears that species diversity of testate amoebae is related not only to macro-environments (e.g., geographic zonation) but also to microenvironments (e.g., microhabitats).