Abdullah Samat

Population growth, trophic level, and reproductive biology of two congeneric archer fishes (Toxotes chatareus, Hamilton 1822 and Toxotes jaculatrix, Pallas 1767) inhabiting Malaysian coastal waters

Population growth, trophic level, and some aspects of reproductive biology of two congeneric archer fish species, Toxotes chatareus and Toxotes jaculatrix, collected from Johor coastal waters, Malaysia, were studied. Growth pattern by length-weight relationship (W=aLb) for the sexes differed, and exhibited positive allometric growth (male, female and combined sexes of T. chatareus; female and combined sexes of T. jaculatrix) and isometric growth (male samples of T. jaculatrix only). Trophic levels of both species were analyzed based on 128 specimens. The results show that, in both species, crustaceans and insects were the most abundant prey items, and among crustaceans the red clawed crab Sesarma bidens and Formicidae family insects were the most represented taxa. The estimated mean trophic levels for T. chatareus and T. jaculatrix were 3.422±0.009 and 3.420±0.020, respectively, indicating that they are largely carnivores. Fecundity of T. chatareus ranged from 38 354 to 147 185 eggs for females with total length ranging from 14.5 to 22.5 cm and total body weight from 48.7 to 270.2 g, and T. jaculatrix 25 251 to 150 456 eggs for females with total length ranging from 12.2 to 23.0 cm and total body weight from 25.7 to 275.0 g. Differences in values of gonadosomatic and hepatosomatic indexes calculated for both species in this study may have resulted from uneven sample size ranges.

Aspects of the reproductive biology of two archer fishes Toxotes chatareus, (Hamilton 1822) and Toxotes jaculatrix (Pallas 1767)

Various aspects of the reproductive biology of two archer fishes Toxotes chatareus and Toxotes jaculatrix were studied to describe gonad development, spawning season, sex ratio, and fecundity. Spawning season was assessed using monthly changes in gonadosomatic index (GSI) and histological inspection of the gonads. Both species exhibit two modes of oocytes; a mode of small primary growth oocytes and a single mode that increases with size as oocytes sequester vitellogenin and undergo maturation, showing the synchronous oocyte development typical of total spawners. Based on GSI values and advanced stages of oocyte maturity, T. chatareus and T. jaculatrix, females appear to spawn from November to December. The average fecundity of female T. chatareus was 55 000 ± 5538 eggs, and T. jaculatrix was 50 000 ± 3440 eggs; fecundity ranged from 20 000 to 150 000 eggs for both species, with relative fecundities of 600 to 1100 eggs/g body weight, and a mean value of 800 ± 32 for T. chatareus; relative fecundity ranged from 500 to 1100 with a mean value of 700 ± 23 for T. jaculatrix. Sex ratio, defined as the proportion of males to females, was 2.2 and 2.5 in T. chatareus and T. jaculatrix, respectively. The apparent abundance of males in samples could be due to females being positioned lower in the water column and therefore being sampled less frequently. Our results indicate that in both species, spawning occurs between the months of November and December during the monsoon season, which provides the mangrove coastal waters inhabited by these species with an abundance of food resources and additional floodplain nursery habitat for larvae and juveniles.

LCA for open systems: a review of the influence of natural and anthropogenic factors on aquaculture systems

PurposeLife cycle assessment (LCA) studies in the aquaculture sector have included marine fish, freshwater fish, and shellfish species within closed (CAS), semiclosed (SCAS), and open aquaculture systems (OAS). The absence of a physical boundary separating open aquaculture systems from natural ecosystems has caused complications in determining the actual environmental conditions of individual aquaculture systems and has resulted in questionable LCA impact analysis results. This paper reviews how natural and anthropogenic factors were managed in the previous LCA studies for aquaculture systems.MethodsTen recent peer-reviewed documents on the LCA study of various aquaculture systems have been selected for content analysis. The disparities between OAS, SCAS, and CAS were outlined. Natural and anthropogenic factors were then identified and analyzed to ascertain their impact on the LCA process.Results and discussionNatural factors such as seasonal variations, biological interactions, and flooding were indicated in the OAS, SCAS, and CAS. For anthropogenic factors, industrial energy inputs and human activities were stated in SCAS and OAS. None of the anthropogenic factors were considered in CAS as these systems are isolated distinctly from natural ecosystems. LCA studies of the OAS have a few approaches: the development of the virtual boundary, a longer period of data collection, harmonization with other environmental management tools, and the need to diversify the LCA study in various regions.ConclusionsFor SCAS and OAS, the interaction between the aquaculture system and flood hazards, temporal changes, dilution effects due to the seasonal variation, disease, and local anthropogenic activities can be studied further. An LCA study of OAS will be more reliable if natural and anthropogenic factors are seen as supportive variables in determining the life cycle impact analysis.

Penyediaan serbuk lantanum strontium kobalt oksida melalui kaedah sol-gel terubahsuai

A simple low temperature synthesis route has been presented for the preparation of single perovskite phase of La0.6Sr0.4CoO3-δ (LSCO) for cathode application in intermediate temperature proton conducting solid oxide fuel cell (SOFC). A wet chemical method namely a modified sol-gel method has been applied in this work. In this method, a combined citric acid and ethylenediaminetetraacetic acid (EDTA) has been used as a chelating agent. Ethylene glycol (EG) and activated carbon (AC) have been used as surfactants in this process. The synthesized powders were characterized by X-ray diffractometer (XRD), scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) spectrometer and particle size analyzer (PSA) for phase formation, morphology and particle size analysis, respectively. XRD result revealed that a single LSCO perovskite phase for both surfactants formed at calcination temperature of 900 °C. The produced single phase powders consist of homogeneous and almost identical shape of particles as shown in SEM images. However, the powder prepared using EG has a smaller average particle size diameter as compared with the powder prepared using AC which is 149 nm and 190 nm, respectively.

Electrical and electrochemical characteristics of La0.6Sr0.4CoO3-δ cathode materials synthesized by a modified citrate-EDTA sol-gel method assisted with activated carbon for proton-conducting solid oxide fuel cell application

AbstractThe electrical conductivity and electrochemical performance of a La0.6Sr0.4CoO3-δ (LSC) cathode produced by a modified citrate-EDTA sol-gel method assisted with activated carbon are characterized for a proton-conducting solid oxide fuel cell (H+ −SOFC) application at intermediate temperature. Thermogravimetric analysis revealed that the decomposition of the unrequired intermediate compounds in the precalcined powder was completed at 800 °C. A single LSC perovskite phase was formed at a calcination temperature of 900 °C, as confirmed by X-ray diffraction analysis. The particle size, crystallite size, and BET-specific surface area of the powder are 219–221 nm, 18 nm, and 9.87 m2 g−1, respectively. The high index value of the extent of agglomeration (5.53) showed that the powder was barely agglomerated. Bulk LSC sintered at 1200 °C for 2 h showed the highest direct-current electrical conductivity (σd.c) compared to that of bulk LSC sintered at 1000 °C and 1100 °C. The value of σd.c was affected by the density and porosity of the sintered samples. The area specific resistance (ASR) of screen-printed LSC working on a proton conductor of BaCe0.54Zr0.36Y0.1O2.95 (BCZY) decreased from 5.0 Ω cm2–0.06 Ω cm2 as the temperature increased from 500 °C to 800 °C with an activation energy of 1.079 eV. Overall, in this work, the LSC material produced with the aid of activated carbon meet the requirements for the application as a cathode in an intermediate temperature H+-SOFC.