Bioaccumulation of heavy metals in the tissues of Schizothorax plagiostomus at River Swat

Snow trout (Schizothorax plagiostomus) is an economically important freshwater fish, mostly found in northern areas of water reservoirs of Pakistan. The current study was conducted in River Swat to analyze the bioaccumulation of heavy metals (Pb, Cr, Ni, and Zn) in tissues of Schizothorax plagiostomus. Tissues were extracted and dissolved in perchloric acid (HClO4) and nitric acid (HNO3) along with hotplate. The heavy metals, zinc (Zn), lead (Pb), chromium (Cr), and Nickel (Ni) were determined using Perkin Elmer 2380 atomic absorption spectrophotometer. Results shows great variation in the content of the metal related to tissue type and sampling sites. A high concentration of bioaccumulation was reported at Charbagh, whereas lowest at Odigram: Charbagh>Landakai>Odigram. In the same way, Cr was the most accumulated heavy metal followed by lead, nickel, and Zinc:

Spatial assemblage and interference competition of introduced Brown Trout (Salmo trutta) in a Himalayan river network: Implications for native fish conservation

Often regarded as a potential threat to the native fish fauna worldwide, the Brown Trout (Salmo trutta), has successfully established its population in the majority of the Himalayan rivers post its introduction dating back to the eighteenth century. Over the years, the species has gained infamy as a sport fish and is considered a profitable source of income to the locals ensuing a heightened propagule pressure due to lack of appropriate management actions. No comprehensive study has been conducted to date in order to understand the mechanism by which the Brown Trout poses threat to the native fish populations. Through the present study, we could assess its competition with the native Snow Trout (Schizothorax richardsonii) to understand the spatial assemblage of both the species across space in Tirthan, a pristine high-altitude river of the western Himalaya. River Tirthan is one of the major tributaries of River Beas traversing for most of its stretch within the protected boundaries of the Great Himalayan National Park Conservation Area. A total of 108 sampling points were chosen from confluence to origin of rivers/streams, ranging from 989 to 3677msl. A total of 28 explanatory variables were recorded at each point. Overall, the Brown Trout adults were found to be greater in relative abundance (66.1%) than the Snow Trout adults (33.9%). The fingerlings of Snow Trout on the other hand, were distinctively high in relative abundance (61.9%) than those of the invasive Brown Trout (38.1%). Non-native trout showed higher abundance in the higher stream orders i.e. in the main streams while natives mostly restricted themselves to the lower order streams. Redundancy analysis (RDA) for species and environmental covariates resulted in 40.75% of constrained variance with higher eigen values for Redundancy analysis1 and Redundancy analysis2. Ward’s minimum variance clustering of Hellinger transformed data revealed sites agglomerating into six reasonable distinct subgroups with respect to species abundances. Immature individuals of non-native and native trout used similar habitat conditions, but they differed in using habitats at adult stage. Our results show a competitive dominance of Brown Trout in terms of higher abundance and maximum space utilization that highlight an urgent action for preventing its introductions to new areas. We recommend a national policy of ‘The Indian Invasive Species Act’ and management level interventions to control overstocking in the areas of established population.

Ontogenic Development Of Gills In Pre To Post-Flexion Stages Larvae Of Himalayan Snow Trout Schizothorax Plagiostomus (Heckel)

The ontogenic development of gills, including gill arch, gill filaments, and gill rakers in pre to postflexion stages larvae of Himalayan Snow Trout Schizothorax plagiostomus were studied with the objectives that this study could serve as a base for further studies about the early embryonic development and organogenesis in various fish species inhabiting hill stream environments. To obtain the pre to post-flexion stages larvae, an artificial breeding experiment was conducted during September- October on the bank of snow-fed river Alaknanda by stripping method. Further, the development of the gill apparatus was studied histologically, using light microscopy. Hatchling takes place 124-130 hours after fertilization at the incubation temperature of 19-200C. On second dph (day post-hatching), gill arches, gill filaments, and branchiostegal membrane began to differentiate. By the third dph, blood channels were observed in gill filaments as well as in pseudobranch. Formation of secondary lamellae, branchial arteries, elongation of the gill cover, cartilaginous rod formation in the gill arch, and the branchiostegal membrane was discernible by fourth-fifth dph. Pillar cells and afferent and efferent arteries with RBCs in primary and secondary lamellae were observed on the seventh dph. Around the onset of exclusive exogenous feeding (twelfth dph), gill rakers and a group of pillar cells with blood channels were recognizable. Well-organized and functional gill structures with increased number and size of secondary gill lamellae were present among the fifteenth-seventeenth dph larvae. The general pattern of structural and functional development of both the natural site and laboratory-reared larvae was similar, except a large amount of mucous and clustered epithelial cells among the laboratory-reared larvae, which may be due to the physiological as well as environmental stress posed by the adverse physicochemical conditions.