Total relative abundance of fish and species richness at 95 sites in small rivers varied significantly with physicochemical factors. Species richness was negatively and positively related with pH and dissolved oxygen, respectively. Relative abundance varied inversely with discharge and ambient ammonia and, directly with depth, substratum, ambient oxygen and alkalinity. Fish were represented by 62 species, the most common being Rasbora paviei, Puntius binotatus and Channa gachua. Canonical correspondence analysis related species and their relative abundances with eight environmental variables into four groups. The most species-rich group was associated with approximately average values for the significant variables. The group with the fewest species was associated with high oxygen and low ammonia and alkalinity. The other two groups had similar numbers of species, one being associated with high ammonia and alkalinity and low oxygen. Species in the other group were found at locations where rivers were relatively wide with comparatively high oxygen and low ammonia concentrations.

Abstract. Biocomposites sheets were prepared by compression molding from mixtures of corn starch plasticized by glycerol as matrix and cellulose fibers, extracted from used office paper, as reinforcement filler with contents ranging from 0 to 8% wt/wt of fibers to matrix. Properties of composites were determined by mechanical tensile test, differential scanning calorimetry, thermogravimetric analysis, water absorption measurement, and scanning electron microscopy. The results showed that higher fibers content raised the tensile strength and elastic modulus up to 109% and 112%, respectively, when compared to the non-reinforced thermoplastic starch (TPS). The addition of the fibers improved the thermal resistance and decreased the water absorption up to 63.6%. Scanning electron microscopy illustrated a good adhesion between matrix and fibers.

The catfish family Siluridae contains 107 described species distributed in Asia, but with some distributed in Europe. In this study, karyotypes and other chromosomal characteristics of 15 species from eight genera were examined using conventional and molecular cytogenetic protocols. Our results showed the diploid number (2n) to be highly divergent among species, ranging from 2n = 40 to 92, with the modal frequency comprising 56 to 64 chromosomes. Accordingly, the ratio of uni- and bi-armed chromosomes is also highly variable, thus suggesting extensive chromosomal rearrangements. Only one chromosome pair bearing major rDNA sites occurs in most species, except for Wallago micropogon, Ompok siluroides, and Kryptoterus giminus with two; and Silurichthys phaiosoma with five such pairs. In contrast, chromosomes bearing 5S rDNA sites range from one to as high as nine pairs among the species. Comparative genomic hybridization (CGH) experiments evidenced large genomic divergence, even between congeneric species. As a whole, we conclude that karyotype features and chromosomal diversity of the silurid catfishes are unusually extensive, but parallel some other catfish lineages and primary freshwater fish groups, thus making silurids an important model for investigating the evolutionary dynamics of fish chromosomes.

Carbon and nitrogen stable-isotope ratios were compared of fin and muscle tissue from 15 fish species collected from seven headwater rivers in eastern and western Thailand. In addition, two-source stable-isotope mixing models were used to derive estimates of each fish's reliance on allochthonous and autochthonous energy based on fin and muscle tissues. Across the dataset, fish fin was enriched in C relative to muscle by c. 1·5‰. Variation in δ N between tissues was below statistically significant levels. Estimates of autochthonous resource use calculated from fin tissue were on average 15% greater than those calculated from muscle. Linear mixed-effects models indicated that inter-tissue variation in estimates of resource use was predominantly related to inter-tissue variation in δ C. Fish fin is a credible and desirable alternative to tissues such as muscle or liver which require destructive sampling of fishes. Care must be taken, however, when estimating resource use or interpreting previous estimates of resource use derived from different tissues.