Stock structure analysis of Labeo rohita (Hamilton, 1822) across the Ganga basin (India) using a truss network system

In this study the intraspecific variation of wild Labeo rohita was investigated on the basis of morphometric characters using the truss network system constructed from the fish body. Altogether 435 fish samples were collected from six drainages of the Ganga basin in India. Data were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. The first principal component (PC1) explained 47.88% of the total variation, while PC2 and PC3 explained 17.22 and 8.33%, respectively. The step‐wise discriminant function analysis retained three variables that significantly discriminated the populations. Using these variables, 62.3% of the original groups were classified into their correct samples and 53.1% of the cross‐validated groups omitting one procedure were classified into their correct samples. Misclassification was higher for samples from the River Gomti (28.6%). Of the total of 31 transformed truss measurements, 30 exhibited significant differences among populations. These findings indicate the presence of six different stocks of L. rohita in the Ganga basin.     

Emergence of toxic cyanobacterial species in the Ganga River,India, due to excessive nutrient loading

Despite of several efforts by the Government of India, pollution in National River Ganga is rising. The aim of the present study is to investigate the pollution in Ganga River in relation to appearance of toxic cyanobacterial strains. Jajmau area of Kanpur city is the industrial hub of Uttar Pradesh and is the main source of adding unwanted discharge into Ganga River. Water samples were randomly collected from the most polluted stretch of Ganga River (Kanpur, Uttar Pradesh, India). Samples were also collected from other major water of Uttar Pradesh to compare their water chemistry with Ganga River. Physico-chemical parameters of water bodies were estimated periodically for three years 2013–2015. Pearson product-mean correlation showed strong correlation between water parameters of sampling sites. Regression analysis showed seasonal variation in water parameters of Ganga River. Cyanobacteria prevalence in Ganga River was highest in May while lowest in August month. Fourteen cultivable cyanobacteria were isolated from Ganga River. Two new isolates, Oscillatoria sp. RBD01 and Leptolyngbya sp. RBD05 were found to be toxic and showed the presence of algal toxin (microcystin). Phylogenetic relatedness of toxic cyanobacterial isolates with their close homologues was established using 16S rRNA sequence analysis. Microcystin content in water samples (extracellular release) and in cyanobacterial isolates (intracellular content) was estimated by enzyme linked immunosorbent assay. Ganga River was found to be positive for microcystin with concentration ≥2 ppb which is above the permissible limit of WHO. Toxic cyanobacteria Oscillatoria sp. RBD01 and Leptolyngbya sp. RBD05 showed the presence of 23 and 17 ppb of microcystin in cells. Growth of the toxic cyanobacteria Oscillatoria sp. RBD01 showed very strong correlation with phosphate (0.834) and nitrate (0.761) content of water. Toxic Oscillatoria sp. RBD01 growing in moderate combination of nitrate (16x) and phosphate (4x) showed optimum growth and protein content. Periodic assessment of water quality and monitoring of toxic cyanobacteria would be helpful in identification and regulation of toxins which are responsible for destroying its sanctity and making it unsafe for human consumption.     

Detection of morphometric differentiation between isolated up- and downstream populations of Siah Mahi (<Emphasis Type="Italic">Capoeta capoeta gracilis</Emphasis>) (Pisces: Cyprinidae) in the Tajan River (Iran)

It has been postulated that the building of the Shahid-Rajaei dam on the Tajan River around 1995 has lead to the morphological divergence of Siah Mahi Capotes capoeta gracilis (Pisces) of up- and downstream populations due to the isolation. A 13-landmark morphometric truss network system was used to investigate the hypothesis. Univariate analysis of variance showed significant differences between the means of the two groups for 45 standardized morphometric measurements out of 78 characters studied. In linear discriminant function analysis (DFA), the overall assignment of individuals into their original groups was 87.6%. The proportion of individuals correctly classified into their original groups was 90.3% for upstream and 83.7% for downstream population. The principal component analysis (PCA) scatter plot of individual component scores between PC1 and PC2 showed 121 fish specimens grouped into two areas but with a relativity high degree of overlap between two populations. Clustering analysis based on Euclidean square distances among groups of centroids using an UPGMA resulted into two main clusters indicating two populations of C. c. gracilis. The present study indicated the presence of two morphologically different populations of C. c. gracilis in the Tajan River across the Shahid-Rajaei dam, probably due to their limited downstream dispersal and the elimination of upstream migration altogether, due the construction of the dam.     

Response of splenic melanomacrophage centers of Oreochromis niloticus (Linnaeus, 1758) to inflammatory stimuli by BCG and foreign bodies

The study objective was to make histological, histochemical and morphometric evaluations on the splenic Melanomacrophage centers (MMCs) of tilapias, Oreochromis niloticus (Linnaeus, 1758), that were subjected to chronic inflammation stimuli by implantation (IMP) of a glass coverslip in the subcutaneous tissue and through inoculation of the bacillus Calmette‐Guerin (BCG). Randomly distributed in four groups were 150 tilapias: IMP (n = 45); IMP+BCG (n = 45); BCG (n = 45); and control (n = 15). Nine fish per treatment and three control fish were sampled on days 3, 7, 14, 21 and 33. The results demonstrated that increased numbers and areas of these structures were related to the type of stimulus, and that these were greater for the specific response. The principal pigment component identified was hemosiderin. Results suggest that the intensity of the MMC response in O. niloticus depended on the type of inflammatory stimulus used, and that it was greater in fish inoculated with BCG, which induced a granulomatous inflammation when compared to the foreign body inflammatory response induced by the glass coverslips.     

Morphological and Genetic variations in the natural populations of Carinotetraodon travancoricus

Carinotetraodon travancoricus or Malabar puffer fish is an endemic species described from rivers originating from the Western Ghats in South India. This species is captured extensively as an aquarium fish and is having substantial demand in global markets. However, being prone to overfishing and impacts of anthropogenic alterations in its habitats, IUCN has categorized it as a threatened/vulnerable species. Since, knowledge on variability of wild populations could help in their conservation and management, morphometric and genotypic analyses were carried out in natural populations of C. travancoricus inhabiting two geographically separated rivers Pamba and Chalakkudy. Mean values of eleven length parameters measured in 456 males and 439 females inhabiting these rivers revealed significant difference (ANOVA, F = 10.2 p < .001) between sexes and between females inhabiting two rivers. Principal component analysis revealed two factors in males and three factors in females, explained variance of 83.62% and 89.94% in respective sexes. Results of both PCA and discriminant function analysis indicated perceptibly high degree of separation between individuals inhabiting the two rivers. A total of 25 COI sequences were generated from C. travancoricus collected from rivers Pamba (n = 14) and Chalakkudy (n = 11). Sequence alignment revealed considerable base substitutions between samples from both rivers, indicating possibility of population differences. AMOVA analysis also provided significant Fst value (0.622; p-value .00) in support of population difference between individuals of both rivers. Interpopulation genetic distance reached upto 2.50%, high enough to confirm genetic diversity among individuals, revealing perceptible population events within this species. The present results indicated high degree of population difference between C. travancoricus inhabiting geographically separated rivers Pamba and Chalakkudy as evidenced from both morphometric and genotypic analyses.     

Relationship of fish and macroinvertebrate communities in the mid-Atlantic uplands: Implications for integrated assessments

Indices developed for stream bioassessment are typically based on either fish or macroinvertebrate assemblages. These indices consist of metrics which subsume attributes of various species into aggregate measures reflecting community-level ecological responses to disturbance. However, little is known about the relationship between fish and macroinvertebrate metrics, or about how ecological health assessments are affected by assemblage-specific responses to disturbance. We used principal component analysis (PCA) and regression analysis of existing fish (n = 371) and macroinvertebrate (n = 442) stream bioassessment data from a multi-source dataset to determine broad scale, within-assemblage metric patterns, and to examine the intercorrelation of fish and macroinvertebrate metrics (n = 246) and their response to watershed area and land use/land cover gradients. Fish and macroinvertebrate metrics expressed as principal components (PCs) accounted for 72.4 and 85.4% of dataset variance, respectively, with PC-metric patterns reflecting aspects of stream impairment including water and habitat quality. Model components predicting fish metric response differed among fish PCs, with watershed area and macroinvertebrate metric response strongly correlated with the first fish PC, and remaining fish PC models consisting of watershed area, land use, and macroinvertebrate PCs. Correlation between fish and macroinvertebrate PCs, and models relating fish and macroinvertebrate PCs generally explained less variation (13–27%) than metric response models of fish (25–34%) and macroinvertebrates (8–38%) to watershed area and land use/land cover variables. Best-response models integrating fish and macroinvertebrate PCs, watershed area, and land use/land cover variables accounted for the greatest variation in fish PCs (32–50%) across sites. Because fish and macroinvertebrate metrics provide different information on ecological condition, integrated use of information from multiple groups may be appropriate when developing monitoring programs.     

Loss of genetic diversity in farmed populations of Colossoma macropomum estimated by microsatellites

The genetic variability of four Colossoma macropomum broodstocks, three from fish farms in different regions and one from the natural environment in Brazil, was analyzed using microsatellite markers. The wild progeny (n = 30) were caught in the Solimões–Amazonas River, at the varzea lakes; this location is used to mature the fish from larvae to juveniles. The three fish farms were selected according to the age of their lineages and broodstock availability: DNOCS (n = 21) is located in the Ceará State, representing the oldest lineage of cultivated tambaqui in Brazil; Balbina (n = 30) is located in the Amazonas State, representing the youngest stocks of tambaqui farmed in Brazil (approximately 15 years); and UFRPE (n = 30) is located in the Pernambuco State and is considered to be a mixed stock formed from the DNOCS and Balbina lineages. The analysis of 13 microsatellite loci indicated the occurrence of a variability reduction in the farmed populations; the UFRPE stock was the population with the highest diversity level. Low values of molecular coancestry were found in these populations. Additionally, significant differences in the R_ST values among the populations were detected, as was the occurrence of genetic structure. The genetic loss found in these populations may have been influenced by the founder effect. Because no breeding programs were during the entire production period and no pedigree records were kept for these broodstocks, we suggest that a wild population might be used as an important genetic resource to increase the genetic diversity of renewal stock lineages.     

Effect of age,size and digestive tract development on weaning effectiveness in crucian carp,Carassius carassius (Linnaeus, 1758)

The study aim was to determine the optimum age, wet body weight (WBW) and total length (TL) of the crucian carp, Carassius carassius (L.), to ensure the effectiveness of weaning directly without a gradual transfer from live food to a compound feed. Moreover, the state of development of the digestive tract was analyzed histologically based on the height of enterocytes. Experimental rearing was conducted between days 5 and 45 post hatch (DPH). Initial WBW of fish was 2.2 ± 0.6 (n = 30) mg and TL 6.1 ± 0.1 (n = 30) mm. Rearing was carried out at 27 ± 0.5°C, with fish divided into six groups: one control (C) fed with Artemia sp. nauplii, and five groups initially fed with Artemia sp. but later replaced by a compound feed. Weaning with the compound diet started at 15, 20, 25, 30 and 35 DPH in groups labeled F15, F20, F25, F30, F35, respectively. Larvae were fed three times per day (08.00 h, 13.00 h, 18.00 h) in equal portions (4% of larvae biomass per day, converted to the dry matter of the feed). Daily biomass growth was adopted as 15%. Each group was triplicated (n = 50 individuals per replicate). Highest values of TL 42.1 ± 0.7 (n = 30) mm and WBW 905.3 ± 50.3 (n = 30) mg were recorded in the control group at 45 DPH; lowest survival rate of 45 DPH was in group F15 (90.7 ± 1.2%, n = 30). The highest value of the enterocyte epithelial length was observed in individuals within groups F30, 34.8 ± 1.2 μm (n = 30) and F35, 35.4 ± 3.6 μm (n = 30), respectively, 30 and 35 DPH; highest percentage of deformations on the final day of the experiment was in group F15 (100 ± 0.0%, n = 30). The results indicate that an effective direct transfer from live food to prepared diets (with no gradual transfer) cannot be performed with crucian carp larvae before 30 DPH at 27°C, when the fish have reached TL = 31.1 ± 0.4 mm (n = 30) and WBW = 436.9 ± 13.7 mg (n = 30).     

Seroprevalence of COVID-19 in Riyadh city during the early increase of COVID-19 infections in Saudi Arabia,June 2020

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) emerged in December 2019 and caused a global pandemic of the Coronavirus Disease 2019 (COVID-19). More than 170 million cases have been reported worldwide with mortality rate of 1–3%. The detection of SARS-CoV-2 by molecular testing is limited to acute infections, therefore serological studies provide a better estimation of the virus spread in a population. This study aims to evaluate the seroprevalence of SARS-CoV-2 in the major city of Riyadh, Saudi Arabia during the sharp increase of the pandemic, in June 2020. Serum samples from non-COVID patients (n = 432), patients visiting hospitals for other complications and confirmed negative for COVID-19, and healthy blood donors (n = 350) were collected and evaluated using an in-house enzyme-linked immunosorbent assay (ELISA). The overall percentage of positive samples was 7.80% in the combined two populations (n = 782). The seroprevalence was lower in the blood donors (6%) than non-COVID-19 patients (9.25%), p = 0.0004. This seroprevalence rate is higher than the documented cases, indicating asymptomatic or mild unreported COVID-19 infections in these two populations. This warrants further national sero-surveys and highlights the importance of real-time serological surveillance during pandemics.     

Stock structure delineation using variation in otolith chemistry of snakehead,Channa punctata (Bloch, 1793), from three Indian rivers

Otolith chemistry was used to study the stock structure of Channa punctata collected from the River Ganga and its tributaries, the rivers Yamuna and Gomti. Whole sagittal otoliths were subjected to acid digestion to analyse the trace elements (Ca, Na, Mg, Sr, Mn, Ba, Fe and K) using ICP‐AES. Data were subjected to appropriate statistical treatments, such as univariate anova , ancova , manova and DFA in order to delineate the fish stock(s) accurately. Mean concentrations of Ca, Mg, Sr, Mn, Ba, Fe and K in the otoliths of the fish from selected sites of the different rivers were significantly (P < 0.001) different from each other, while the mean Na concentrations were comparable (P > 0.05). In classification statistics, 96% of individuals were correctly classified to their original groups. The scatter plot of DF‐I vs DF‐II depicted the presence of different stocks in the River Ganga and its selected tributaries. Variations in the microchemistry of the otoliths showed the presence of four C. punctata stocks in the three selected rivers.     

Morphometric differentiation of Pseudocalanus minutus populations in the Barents Sea

Dvoretsky VG. and Dvoretsky AG. 2011. Morphometric differentiation of Pseudocalanus minutus populations in the Barents Sea. —Acta Zoologica (Stockholm) 00 : 1–12. We investigated spatial variations in the morphometric characteristics (total length of body, lengths of cephalothorax, abdomen and antennules, and their relative proportions) of Pseudocalanus minutus, an abundant copepod species across the Barents Sea in August–September 2007. Females were found to have higher values for the measured parameters than males. The average absolute morphometric characters of both sexes increased from the south to the north. In most cases, parameters were similar in the southern, central, and eastern regions delineated by cluster analyses of oceanographic variables. The morphometric characteristics were strongly correlated with environmental variables in both males and females. Multiple regression analysis showed that temperature together with salinity explained 72–85% (in females) and 38–91% (in males) of the total variations in the log₁₀‐transformed morphometric parameters. According to principal component analysis and discriminant function analysis, two distinct groups could be separated in the Barents Sea. The first group included the copepods from the northern region; the other included populations from the southern, central, and eastern regions. The observed morphological variation can be interpreted as geographical variation connected with hydrological variability.     

Fine‐scale population structure of Collichtys lucidus populations inferred from microsatellite markers

The spinyhead croaker Collichthys lucidus (Richardson) is a small sciaenid species distributed along the inshore waters of northwestern Pacific Ocean, and now has been listed as Key Protected Commercial Sources of Aquatic Animals and Plants in China. To delineate stock boundaries and inform conservation policy for its management, samples were collected from eight locations across the Chinese coastal waters and analyzed at nine microsatellite loci. C. lucidus populations showed low genetic diversity (expected heterozygosity = 0.445–0.542; observed heterozygosity = 0.392–0.539; Polymorphism Information Content = 0.268–0.684). Strong genetic fdifferentiation (F_st = 0.065–0.510, all significant after Bonferroni correction) among all populations and high levels of self‐recruitment (89.2%–91.5%) were observed, which suggested limited genetic exchange for this species. Clustering results of discriminant analysis of principal components and STRUCTURE found strong support for obvious genetic clusters (populations FZ, XM and SZ vs. populations SH, YRE, ZS, WZ and ND). The results of the present study not only supported the phylogeographic pattern of north‐south differentiation, but also suggested that C. lucidus populations may be predominantly sustained by self‐replenishment rather than by recruitment from distant populations.     

Fish composition and abundance in the wetlands of Cross River, Nigeria

Environmental parameters and ichthyofauna were investigated over a 2 years period in three regions along the 200 km length of Cross River. The objective of the study was to quantify the relative importance of local environmental conditions prevailing within sampling sites and the composition and abundance of the principal fish species in the upper, middle and lower reaches of the river. Vegetation cover, size of river, flow velocity, water level, temperature, transparency, and food availability explained the observed seasonal and spatial changes in fish abundance. Forty-six species and 28 genera of fish belonging to 16 families were recorded among the 14,466 fish caught. Three fish families (Cichlidae, Bagridae, and Clariidae) yielded highest number (41.3%) of species while Denticeptidae, Protopteridae, and Osteoglossidae had the least. Oreochromis niloticus, Chrysichthys nigrodigitatus, and Clarias anguillaris numerically dominated (46.4%) catch composition. Species richness was higher for the river stretch in forest area than in savanna, and it was correlated significantly with width of the reach, water transparency, depth, and flow velocity (P < 0.001) of the river. Wet season samples were more diverse (>0.6) and had higher richness (>9.7) than those for dry season. Wet season and forest regions were therefore critical in maintaining fish stock of Cross River.     

Blood plasma resonance Raman spectroscopy combined with multivariate analysis for esophageal cancer detection

We herein report a novel, reliable and inexpensive method for detecting esophageal cancer using blood plasma resonance Raman spectroscopy combined with multivariate analysis methods. The blood plasma samples were divided into late stage cancer group (n = 164), early stage cancer group (n = 35) and normal group (n = 135) based on clinical pathological diagnosis. Using a specially designed quartz capillary tube as sample holder, we obtained higher quality resonance Raman spectra of blood plasma than existing method. The study demonstrated that the carotenoids levels in blood plasma were reduced in esophageal cancer patients. The area under the receiver operating characteristic curve (and 95% confidence interval) calculated by wavenumber selection and principal component analysis combined with linear discriminant analysis (PC-LDA) algorithm were 0.894 (0.858-0.929), 0.901 (0.841-0.960) and 0.871 (0.799-0.942) for differentiating late cancer from normal, late cancer from early cancer, and early cancer from normal respectively. The contribution from the two carotenoids wavenumber regions of 1155 and 1515 cm⁻¹ were more than 84.2%. The results show that the plasma carotenoids could be a potential biomarker for screening esophageal cancer using resonance Raman spectroscopy combined with wavenumber selection and PC-LDA algorithms.      

Morphometric differentiation between two juvenile tuna species [Thunnus thynnus (Linnaeus, 1758) and Euthynnus alletteratus (Rafinesque, 1810)] from the Eastern Mediterranean Sea

The main objective of this study was to analyse the differences in morphometric characteristics among specimens of Atlantic juvenile bluefin tuna Thunnus thynnus [12.2–46.5 cm fork length (FL)] and juvenile little tuna Euthynnus alletteratus (14.1–26.4 cm FL). A total of 353 bluefin tuna (young of the year) and 288 little tuna (young of the year) were collected from the commercial hand line fisheries in the eastern Mediterranean Sea between July and October of 2011–2013 with three round‐bent hook sizes (numbers 10, 12 and 14; Mustad 2315S). By using univariate and multivariate analysis, 11 morphometric characters were investigated. anova revealed highly significant differences (P < 0.001) for all morphometric parameters among the two species. The principal component analysis showed that the difference between the species resulted mainly from preanal length (LA), caudal fin hight (CC), snout length (SnL), eye diameter (ED) and postorbital length (PO). The stepwise discriminant analysis revealed that juveniles of the two tuna species were correctly classified, with a percentage of 99.2%. Length of pectoral fin (LP) was the strongest predictor in the discriminant functions.     

Saddleback syndrome in yellowfin bream [Acanthopagrus australis (Günther, 1859)] in Moreton Bay,Australia: its form,occurrence, association with other abnormalities and cause

The aim of this study was to determine if saddleback syndrome (SBS) in a wild population of yellowfin bream (Acanthopagrus australis) was the result of a developmental defect or caused by physical injury. Information was collected in 2012 on the incidence of SBS and other abnormalities in this species in Moreton Bay, Australia. Abnormalities in adult fish (>250 mm Total Length, TL) with SBS (n = 47) were compared with those without SBS (n = 30). A sample of juvenile fish (n = 404) was checked for the presence of SBS. The results show that scale loss, scale pattern misalignment, lateral line fracture and pectoral fin abnormality were closely associated with SBS. SBS was uncommon (<2%) in juveniles <70 mm TL, but common (>12%) in the larger juveniles (70–215 mm TL). These results, together with the findings that scale loss associated with SBS in adult fish occurred in the range 80–245 mm back‐calculated TL, indicate that SBS and the related abnormalities in yellowfin bream are a result of physical injuries to larger juveniles (>70 mm TL). The reduction in the incidence of SBS from approximately 12% in the larger juveniles to 5% in adults is evidence of mortality associated with SBS.     

Combining geometric morphometrics and genetic analysis to identify species of Opisthonema Gill, 1861 in the eastern Mexican Pacific

Studies focusing on the specific identification of the taxonomic cast within the genus Opisthonema are scarce and contradictory, in spite of this species commercial importance and of the potential ecological impact that fisheries may have on the pelagic ecosystem. In this study, the specific composition of thread herrings Opisthonema (O. bulleri, O. medirastre, and O. libertate) in the southeastern region of the Gulf of California was identified using meristic characters, morphometric data, and mtDNA sequences. In this paper we supported the hypothesis that the commercial catch comprises three evolutionary entities with meristic and morphometric differences. The results were based on the number of ceratobranchial gill rakers, the presence of spicules on the gill rakers, the form of insertion of the gill rakers base onto the ceratobranchial segment, the geometric morphometrics of body shape, and the genetic distances from a fragment of Cytochrome Oxidase Subunit I gene (COI) of mtDNA. Specimens of Pacific thread herring were obtained from landings of the small pelagic fleet at Mazatlan, Sinaloa during 2011–2012. Taxonomic categories were assigned to 1060 individuals according to the measurement of meristic characters. A total of 228 thread herrings O. bulleri, (n = 76), O. medirastre (n = 76), and O. libertate (n = 76) were used in the morphometric analysis, and 25 specimens (O. bulleri n = 8, O. medirastre n = 7, and O. libertate n = 10) were used for genetic comparisons. The morphometric results showed differences among the three groups that had been previously identified using meristic characters, giving support to the existence of three discrete morphotypes. The percentage of sequence divergence of the COI gene supports the existence of three clades. Genetic distances were considerably lower within each clade than between clades. The results of this study provide sufficient evidence for the existence of three Pacific thread herring species in the southern Gulf of California.     

Length–weight relationships for Eutropiichthys murius (Hamilton, 1822), Coilia reynaldi Valenciennes, 1848 and Johnius gangeticus Talwar, 1991 from lower stretch of the River Ganga,India

Length‐weight relationships (LWRs) for three fish species from the River Ganga (India) is presented. Sampling was conducted from the lower stretch of the River Ganga (Patna: 25°36′51.66″N & 85°12′7.02″E to Freserganj: 21°35′40.58″N & 88°15′28.92″E) during April, June and September and December of 2017. Specimens were caught using gill nets (18 nos.; mesh 18–32 mm), and bag nets (3 nos.; mesh 14–22 mm). The values a and b from LWRs ‐were found to be 0.007 and 2.977 for Eutropiichthys murius; 0.003 and 3.001 for Coilia reynaldi; 0.009 and 3.010 for Johnius gangeticus.     

Length–weight relationship and condition factor of the Characidae matrinxã, Brycon falcatus (Müller & Troschel, 1844), in the Teles Pires River,southern Amazon

The aim of this study was to verify whether the in situ supply of soybean as a fish attractant bears any influence on the length–weight relationship and condition factor of the omnivorous fish species, Brycon falcatus. In addition, estimated was the length–weight relationship, standard and total length, condition factor, and size of B. falcatus in the spawning period in the Teles Pires River Basin. In the experimental design, rivers of the Teles Pires Basin containing soybean attractant (Verde River, Celeste River, Teles Pires River and the Tapaiuna River) were mapped. Fish were also collected from the Cristalino River, which contained no soybean attractant (treatment control). Samples were collected from August 2012 to July 2013. Length–weight relationship of B. falcatus in the Teles Pires River Basin can be obtained by the expression: Wt = 0.0091*SL^3.376, r² = .97, n = 102, and length‐length relationship: TL = 1.128*SL + 3.978, r² = .96. The condition factor of all specimens collected in the Teles Pires Basin was k = 1.055. Size at capable phase (L50) of spawning was estimated at 23 cm standard length. Results showed no significant difference in the length–weight relationship or condition factor of B. falcatus collected from rivers with or without soybean attractant. Concluded is that the in situ supply of soybean as a fish attractant does not interfere with the wellbeing of B. Falcatus in the Teles Pires River Basin.     

Morphological variations among four riverine populations (Bangladesh) of endangered catfish Rita rita (Hamilton, 1822)

The morphological variation of the endangered catfish Rita rita was studied based on meristic, length–weight relationship (LWR), traditional (TRA) and truss (TRU) distance based morphometric analysis of 200 juveniles collected from the Old Brahmaputra, Jamuna, Meghna and Kangsa rivers. Data were subjected to Kruskal–Wallis test for meristic counts, t test for LWR, univariate ANOVA, multivariate discriminant function analysis and canonical analysis (CA) both for TRA and TRU morphometric characters to discriminate the populations. Kruskal–Wallis test denoted that only one (caudal fin rays) out of six meristic counts was significantly (p < .05) variable among the stocks. One sample t test clarified that all parameters of LWR were significantly (p < .05) differentiated in all stocks. Univariate ANOVA revealed significant (p < .001, p < .01, and p < .05) differences among the four stocks in 14 of 15 standardized TRA traits and 17 of 25 TRU distances, respectively. The first discriminant function (DF1) explained 59.4% and 68.0% of total variance, while 30.6% and 23.1% by DF2, 10.0% and 8.9% by DF3 for TRA and TRU features, respectively among the stocks. CA showed a clear separation of the stocks both for TRA and TRU measurements. The overall random assignment of individuals into their original groups was high as 78.5% for TRA and 78.0% for TRU characters, respectively, indicating that all the four stocks are highly divergent from each other. The results exposed existence of four distinct phenotypic stocks of R. rita in the tested rivers.