Taxonomic, morphometric and limnological assessment of the commercially important ichthyofauna of Sakhakot Stream, Malakand, Pakistan

The present study was conducted for the taxonomic, morphometric and limnological assessment of the commercially important ichthyofauna of Sakhakot Stream, Malakand, Pakistan. The study area was divided into three sites along the water course namely Dargai Stream, Sakhakot Stream and Shergarh Stream. Fish samples were collected randomly during January to August 2017 with the help of fish gears. A taxonomic key was designed for the collected fish specimens. Ten fish species were identified belonging to 3 orders and 4 families. Family Cyprinidae was the dominant family with seven representative species while families Siluridae, Nemacheilidae and Mastacembelidae were represented by one species each. Lower mean total length and standard length was recorded in Puntius conchonius (Hamilton, 1822) as 9.2 ± 0.6 cm and 7.3 ± 0.6 cm respectively, while highest mean total length and standard length was recorded in Mastacembelus armatus (Lacepede, 1800) as 28.1 ± 1.7 cm and 15.9 ± 2.4 cm respectively. Mean pH of the water ranged from 6.1 at Shergarh Stream in August to 8.7 at Sakhakot Stream in January. Average temperature range was recorded from 10.9 °C in January at Dargai Stream to 18.7 °C in August at Shergarh Stream. No statistically significant difference was found for temperature (p = 0.96) and pH (p = 0.14) in the three water streams. The present study will provide a baseline for the rearing and enhancement of wild stock of the commercially important ichthyofauna in the field of aquaculture and fisheries.

Telomere-to-telomere assembly of a fish Y chromosome reveals the origin of a young sex chromosome pair

Background The origin of sex chromosomes requires the establishment of recombination suppression between the proto-sex chromosomes. In many fish species, the sex chromosome pair is homomorphic with a recent origin, providing species for studying how and why recombination suppression evolved in the initial stages of sex chromosome differentiation, but this requires accurate sequence assembly of the X and Y (or Z and W) chromosomes, which may be difficult if they are recently diverged. Results Here we produce a haplotype-resolved genome assembly of zig-zag eel (Mastacembelus armatus), an aquaculture fish, at the chromosomal scale. The diploid assembly is nearly gap-free, and in most chromosomes, we resolve the centromeric and subtelomeric heterochromatic sequences. In particular, the Y chromosome, including its highly repetitive short arm, has zero gaps. Using resequencing data, we identify a ~7 Mb fully sex-linked region (SLR), spanning the sex chromosome centromere and almost entirely embedded in the pericentromeric heterochromatin. The SLRs on the X and Y chromosomes are almost identical in sequence and gene content, but both are repetitive and heterochromatic, consistent with zero or low recombination. We further identify an HMG-domain containing gene HMGN6 in the SLR as a candidate sex-determining gene that is expressed at the onset of testis development. Conclusions Our study supports the idea that preexisting regions of low recombination, such as pericentromeric regions, can give rise to SLR in the absence of structural variations between the proto-sex chromosomes.

KEANEKARAGAMAN IKAN DI SUNGAI SULUP KECAMATAN RIMBO PENGADANG KABUPATEN LEBONG PROVINSI BENGKULU

This study aims to determine the diversity of fish species in Sulup River, Rimbo Pengadang District, Lebong Regency, Bengkulu. The Research was conducted from in April-May 2020. The method used in this study is a direct survey method. The sampling method used is purposive sampling by dividing the research station into 3 stations based on river conditions. The types of fish found in the Sulup River Rimbo Pangadang District Lebong Regency Bengkulu Province were found as many as 4 orders, 4 families with 8 species namely species Mystus singaringan, Angullia marmorata, Osteochilus vittatus, Hampala macrolepidota, Barbonymus gonionotus, Schismatorhynchos heterorhynchos, Rasbora argyrotaenia and Mastacembelus armatus. The ecological conditions in the Sulup river have a temperature of 230C, a depth of 1.5 m, 45 cm river clarity, water pH 7, flow velocity 0.66 m/sec. Sulup River has a diversity index of 0.840, so the diversity index is low.

Pericentromeric heterochromatin impacts genome compartmentalization and sex chromosome evolution in a fish

Compartmentalization is one of the principles of chromosome 3D organization and has been suggested to be driven by the attraction of heterochromatin. The extent to which the pericentromeric heterochromatin (PCH) impacts chromosome compartmentalization is yet unclear. Here we produced a chromosome-level and fully phased diploid genome of an aquaculture fish, zig-zag eel (Mastacembelus armatus), and identified the centromeric and pericentromeric regions in the majority of chromosomes of both haploid genomes. The PCH is on average 4.2 Mb long, covering 17.7% of the chromosomes, and is the major target of histone 3 lysine 9 trimethylation (H3K9me3). In nearly half of the chromosomes, the PCH drives the chromosomes into two or three megascale chromatin domains with the PCH being a single one. We further demonstrate that PCH has a major impact in submetacentric, metacentric and small telocentric chromosomes in which the PCH drives the distribution of active and inactive compartments along the chromosomes. Additionally, we identified the young and homomorphic XY sex chromosomes that are submetacentric with the entire short-arm heterochromatinized. Interestingly, the sex-determining region seems to arise within the PCH that has been in place prior to the X-Y divergence and recombination suppression. Together, we demonstrate that the PCH can cover a considerably large portion of the chromosomes, and when it does so, it drives chromosome compartmentalization; and we propose a new model for the origin and evolution of homomorphic sex chromosomes in fish.

Length-weight relationships of three freshwater eel species from the floodplain ecosystems of northeastern Bangladesh

This study reports the Length-weight relationships (LWRs) of three freshwater eel species from the northeastern wetlands of Bangladesh. A total of 2684 specimens of Mastacembelus armatus, Macrognathus aculeatus and Macrongathus pancalus were sampled between in the months of June and December 2019 using different nets and eel traps at every 4 days working schedule per month. The calculated a values of the LWRs ranged from 0.008 to 0.020; b values ranged from 2.35 to 2.70, and r2 from 0.907 to 0.944. The lowest values of regression coefficient found for M. aculeatus and the highest for M. pancalus. All the regression parameters for LWRs found highly significant (p ˂ 0.001). These results will provide baseline information for sustainable management and conservation of the fisheries resources in the northeastern floodplain region of Bangladesh.

Age and growth analysis of the fish Mastacembelus armatus (Lacepede) from River Nayar, Garhwal Himalaya, Uttarakhand

The ability to age fish accurately is essential in understanding the dynamics of fish population. Age and growth determination in Mastacembelus armatus was assessed by the scale method which was verified by the length-frequency distribution method. The scales were small, elongated and the focus was shifted slightly uppish from the centre. The fish length and scale radius relationship was found linear (Scale radius = 6.974 + 0.452 Fish length; r = 0.9746) and authenticated the age analysis. Back calculation method was used to find out the size of fish at annulus formation, which confirmed four age rings in M. armatus at the size of 14.07±0.92, 26.05±4.99, 37.96± 2.59 and 48.48±6.06 cm respectively. First two age rings were observed in the fish length group 30-40 cm, the third ring was observed in 40-50 cm and the fourth ring in 50-60 cm length group. The finding was dully validated by length-frequency distribution method. The growth annual increment (h) of M. armatus shows that the length increment was 14.07, 13.32, 11.91 and 10.52 cm during 1st, 2nd, 3rd and 4th year respectively. It shows that the fish grows continuously during its entire life period. The average growth (? h) was observed as 12.12 cm. annually. The assessment of age and growth rate of fish is a prerequisite to generate the information on recruitment, longevity and fluctuations in fishery caused by various year classes which is an important tool for rational exploitation of fish stock.

Study of cestode infection in relation to the sex of the host fish, Mastacembelus armatus

The present communication deals with the study of cestode infection in a popular freshwater fish, Mastacembelus armatus in relation to the male and female sex of the host. In this study the author calculated the maximum prevalence, mean intensity and relative density in the males of host fish.

Study on the Present Status of Endangered Fishes and Productivity of Teesta River Closest to Barrage Region

This study was conducted to monitor the present condition of endangered fishes and productivity of Teesta river closest to Teesta barrage situated in the Lalmonirhat district of Bangladesh. Water and sediment samples were collected twice in a month during the study period from six different (3 upstream and 3 downstream) sites with three replications for each. Required information about threatened fishes was collected from the sampling region associated fishermen and fish markets. The study disclosed over 50 threatened fish species in Teesta river including several threatened fishes namely Bagarius bagarius, Sisor rabdophorus etc. The commonly available endangered fishes were Macrognathus aculiatus, Mastacembelus armatus, Barilius tileo, Raiamas bola, Botia dario, B. lohachata etc. which are rarely available in nationwide. Planktonic flora and fauna determination revealed that comparatively higher density of plankton (n >11500 per liter) as well as more number of planktonic flora (>21 nos.) and fauna (>9 nos.) were monitored in the early monsoon and monsoon season (April-September) and comparatively lower planktonic density (n<10000 per liter) and less number were found in premonsoon season (January-February). The investigation of benthic fauna showed that the riverine ecosystem near to barrage contained 16 species of macro-benthos from different groups. Lastly, it can be noticed that it is very essential to take all effective necessary actions to provide good productivity and conserve the ichthyo diversity of Teesta river that will help to conserve the commonly available endangered and critically endangered fishes of Teesta river. Res. Agric., Livest. Fish.7(3): 577-589, December 2020