Impact of fresh water acidification on the growth, vertebral column formation and blood parameters of Mahseer (Tor tambroiders, Bleeker 1854)

Abstract

Raising carbon dioxide (CO2) levels in the atmosphere get absorbed into both sea and freshwater as a result, the water bodies become more acidic over time. Increased CO2 in water bodies is also causing a wide range of well-documented problems for marine and freshwater organisms including fish. These studies were conducted to determine the effect of CO2 on the growth performance, skeletal structure, and blood parameters (hematological and biochemical) of mahseer (Tor tambroides) and were examined under control laboratory conditions. juvenile T. tambroides (5.00 ± 0.01 cm length and 2.40 ± 0.01 g weight) were subjected to a different concentration of CO2 (400, 600, 800, and 1000 parts per million (ppm) in triplicates with 12 fish per replication. At the end of 84-day experimental period, the growth index including body weight gain (BWG), relative growth rate (RGR), daily growth rate (DGR), and specific growth rate (SGR) were calculated. Results showed that the highest mean growth performance was observed in 400 ppm (BWG: 3.75±2.65 g, DGR: 3.34±0.88% day -1 , RGR: 40.86±1.19%, SGR: 1.22±0.06% day -1) and lowest was observed in 1000 ppm (BWG: 2.93±2.33 g, DGR: 2.65±0.78% day -1 , RGR: 20.59±1.50%, SGR:0.97±0.25 day -1). This study showed that BWG, SGR, DGR, RGR, FCR, FCE, and the survival rate of juvenile T. tambroides was adversely affected due to high CO2 levels (1000 ppm). However, this had a favorable effect on FC due to the higher energy demand and maintenance of T. tambroides which requires additional food. In addition, the vertebral column also shows an increase in the incidence of anomalies when the CO2 level increases and shows several types of defects in the vertebral bones such as lordosis, bifurcated spines, vertebral compression, and crooked spines. Furthermore, the results denote that both hematological and biochemical parameters were in favorable conditions at lower CO2 than at higher concentrations of CO2. The increment of white blood cells and cortisol at higher CO2 concentrations where white blood cell (400 ppm:16.30×10 9L < 600 ppm:69.67×10 9L < 800 ppm: 83.40×10 9L < 1 000 ppm: 95.50×10 9L) while cortisol (400 ppm:0.5 UG/DL < 600 ppm: 2.5UG/DL < 800 ppm: 6.3 UG/DL < 1 000 ppm: 8.6 UG/DL) also shows that as the CO2 concentration rose from 400 to 1000 ppm, the fish showed indirect signs of stress. The growth performance, skeletal structure, and blood parameters of mahseer juveniles were significantly affected when exposed to a high concentration of CO2 (1000 ppm). The results obtained in this research will give an understanding of how big the effect of freshwater acidification on the growth performance, skeletal structure, and blood parameters of mahseer juveniles which will indirectly help fisheries biologists and resource managers for sustainable management.