What major environmental concern was raised in 2005?

The major environmental concern raised in 2005 regarding the native fish population crash is significant because it highlighted the dire state of aquatic ecosystems in California, particularly those reliant on the Sacramento-San Joaquin River Delta. In that year, alarming reports indicated that several fish species, including the Delta Smelt, were experiencing drastic declines, prompting urgent discussions about their conservation and the broader implications for California's water management policies.

This concern brought attention to the intertwined relationship between water supply practices and the health of local ecosystems. It underscored the critical need to balance water extraction for agricultural and urban use with the sustainability of fish populations, some of which are endemic to the Delta. The situation led to various regulatory discussions and initiatives aimed at protecting these fish, which serve as crucial indicators of environmental health.

Other options, while related to California water issues, did not specifically encapsulate the overarching crisis concerning native fish populations as it was perceived in 2005. For instance, levee failure vulnerability and groundwater loss, while pressing issues, did not become significantly highlighted until later, and Delta Smelt protection rules emerged largely as a response to the concerns about fish population crashes. Thus, the focus on native fish in 2005 captures the urgent environmental realities and drives for policy reform