The Murray-Darling Basin is the natural habitat of the Murray Cod, a native Australian freshwater fish - HSC - SSCE Biology - Question 21 - 2004 - Paper 1

Increased water salinity poses significant challenges for the survival of the Murray Cod due to its physiological adaptations and water balance mechanisms.

First, the Murray Cod is a freshwater species adapted to low salinity environments. When salinity levels in their habitat increase, the osmotic balance within the fish becomes disrupted. The cod relies on gills and kidneys to regulate its internal salt concentrations, maintaining homeostasis. Higher salinity levels can lead to dehydration, as water from the fish's body is drawn out into the surrounding water, causing cellular stress and potential physiological harm.

Furthermore, increased salinity can negatively affect the prey availability for the Murray Cod. Many freshwater organisms are unable to survive in higher salinity environments, leading to a decline in food sources. This reduction in prey not only threatens the nutrition of the cod but also affects its reproductive success, as the health and survival of offspring are directly related to their access to suitable food.

In summary, the implications of increased water salinity in the Murray-Darling Basin can threaten the survival of the Murray Cod by disrupting their physiological balance and diminishing their food sources, ultimately impacting their population dynamics.