ABSTRACT
Since 1750, the level of atmospheric carbon dioxide has been rising from 280 ppm to 385 ppm in 2010 and is predicted to increase to 560 ppm by 2050 (Table 8.1). During the last 250 years, the levels of other greenhouse gases, methane and nitrous oxide have also increased from 715 ppb to 1774 ppb and from 270 ppb to 320 ppb, respectively (IPCC, 2013). As a consequence, the global climate is gradually warming the habitats including oceans, seas, lakes, rivers and ponds inhabited by fi shes and other organisms. Global mean temperature has increased by about 0.2°C/decade over the last 30 years with most of the added energy absorbed by surface waters of oceans (up to 700 m depth), where temperature increased by about 0.6°C over the 100 years and is continuing to increase. Global spring season is advanced by 2.3 days per decade and species range is shifted by 6.1 km/decade toward the poles (Parmesan and Yohe, 2003). This undesired change in temperature of aquatic systems may have a dramatic effect on geographic distribution of fi shes (e.g., cod being replaced by sea bass, Eddy and Handy, 2012; see also Perry et al., 2005), shift in spawning season (e.g., threadfi n bream, Vivekanandan, 2013b) and change in sex ratio (e.g., Atlantic silverside, Conover and Kynard, 1981). Long term monitoring of the health and reproductive status of Perca fl uviatilis females in the Baltic Sea, Hansson et al. (2006) reported decreases in age from 6.0 years in 1988 to 4.2 years in 2000 and gonado somatic index from 6.75 to 4.5. During these years, the
authors noted not only temperature increased but also continuous supply of hydrocarbons to the Baltic Sea.
