AQUATIC ECOSYSTEM AND FISH: A REVIEW ON ALTERATIONS OF CLIMATE CHANGE IMPACT ON LABEO ROHITA PHYSIOLOGY

Abstract

Climate change presents significant physiological challenges to Labeo rohita (rohu), a crucial freshwater fish species in South Asia, impacting regional economies and nutrition. As an exothermic animal, rohu's survival is closely linked to water temperature, with an optimal range of 25-32°C. However, rising global temperatures and altered precipitation patterns induce extreme temperature variations, triggering a cascade of adverse effects. High temperatures (32-36°C) lead to reduced weight gain, protein efficiency, and survival rates. Specifically, temperatures of 34°C can cause yolk and zygote destruction, slowing down incubation and hatching rates, while 36°C may result in total mortality of developing eggs and embryos. The Indus River delta, for instance, experiences temperature fluctuations from 9°C to 34°C, disrupting rohu's spawning, fecundity, and survival. Additionally, increased salinity levels due to seawater intrusion further exacerbate stress, with survival rates declining from 98% to 83%, 72%, and 64% with 2%, 4%, and 6% increases in salinity, respectively. These stressors impair gill function, leading to structural damage and osmoregulatory challenges, and affect erythrocyte physiology, compromising oxygen transport. Furthermore, thermal stress suppresses the expression of growth hormone (GH) and insulin-like growth factors (IGF), impacting growth and immune function. Given Rohu's substantial GDP contribution (e.g., 3.47% in Bangladesh), adaptation strategies and improved management practices are essential to mitigate these impacts and ensure the continued contribution of this species to regional food security and economies.