SUDRISTY CHAKMA
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh
Exotic fishes, Farming condition, Mymensingh area
Mymensingh district
Animal Health and Management
Selection of the study area: The present study was conducted in two farms of Mymensingh region such as Daponia fish Farm, Chander Haat, Daponia, (Md. Mokhlesur Rahman was the owner of the farm) and Bangladesh Catfish Ltd, Labonkotta, Habirbari, Seed store, Bhaluka, Mymensingh. Duration of the study: The study was carried out for a period of four months from November, 2012 to February, 2013 and sampling was carried out from each farm fortnightly. Experimental fish: Two exotic fishes such as Thai koi (Anabas testudineus) and Thai pangas (Pangasianodon hypophthalmus) were selected for the study. At least four fishes of each species from each farm were collected during every sampling. Estimation of water quality parameters: During each sampling point, water quality parameters such as water temperature (°C), pH, dissolved oxygen (mg/l) and ammonia (mg/l) were measured. Water temperature was measured by using a Celsius thermometer. Dissolved oxygen and pH were measured directly by using a digital oxygen meter and pH meter respectively. Clinical observation: During the experimental period, clinical changes were recorded. From each farm, fishes were examined by necked eyes to observe the external signs and color changes, injury, lesions in fin and muscle, appendage damage and other abnormalities. Collection of fish samples for histopathology: After collection the selected fishes were anaesthetized by giving strong blow over the head. Samples from various organs such as skin, muscle, gill, liver and kidney were collected by sharp scalpel and forceps. Skin and muscle were collected from place between anterior part of the dorsal fin and lateral line and by removing operculum, gill samples were collected. For liver and kidney, fishes were dissected and then portions of liver and kidney were collected. Histopathological procedure: Fixation and preservation of fish sample For histopathological observation samples of fish from various organs such as skin, muscle, gill, liver and kidney were collected by sharp scalpel and forceps. For liver and kidney, fish were dissected and portion of liver and kidney were collected and preserved in 10% neutral buffered formalin. Skin and muscle were collected from the place between anterior part of dorsal fin and lateral line. The amount of fixatives was 10 times to bulk of tissue fixed. After at least 8 hours of fixation, the samples were trimmed in order to obtain a size of 1 cm3 Dehydration, clearing, infiltration, embedding, trimming and sectioning The preserved samples were taken out and placed separately in a perforated plastic holder, which was covered by perforated steel plates. Labeling was made with dark pencil (2B) in perforated plastic holder. The samples were then arranged in a steel rack and dehydrated, cleared and infiltrated in an automatic tissue processor (SHANDON, CITADEL 1000). Alcoholic series if higher concentrations, xylene and paraffin wax were used in the processor maintaining at various time schedule. The samples were then embedded with melted wax, steel mold and perforated plastic holder. Proper care was taken for the orientation of skin and muscle samples in the steel molds during embedding. After embedding the paraffin blocks were placed on a table to be solidified. The blocks were then placed in a refrigerator (deep freeze) foe half an hour and then the steel molds were separated from the paraffin blocks. Trimming was done from side and surface of the blocks by the scalpel and a microtome machine (Leica JUNG RM 2035). Before sectioning blocks having hard tissue e.g. skin and muscle were decalcified by dissolving the surface of the blocks in decalcifier for an hour and then washed repeatedly. The blocks were then kept in the deep freeze for 30 minutes. Sections were taken from the blocks at a thickness of 5 micrometers by using the microtome. The ribbon with sections was placed on a water bath (Electrotharmal, MOUNTING BATH) at a temperature of 400C. Suitable sections were selected and separated from the ribbon, which were finally picked up over glass slides. The glass slides were then labeled by a diamond marker and kept on hot plate (photox-dishwarmer 2) at 400C for 8 hours to fix the sections properly with the slides. The sections were then stained with haematoxylin and eosin stains proceeding through various chemicals of different concentrations and time schedule. After staining the sections were mounted with Canada balsam and covered by cover slips. The prepared sections were left over a clean platform to hold the cover slips permanently and then examined under a compound microscope (Olympus). Photomicrograph of the stained sections was obtained by using a photomicroscope (OLYMPUS, Model CHS, Japan). The observed clinical and pathological signs were compared species wise, monthwise and farmwise.
MS Thesis, Roll No. 12 Fish Aqua JJ 16M, Registration No. 39553 Session: 2012-2013, Department of Aquaculture, Bangladesh Agricultural University, Mymensingh
Thesis