Behavioural avoidance of acidified water by juveniles of four commercial fish and prawn species with migratory life stages

Abstract

Impacts on aquatic ecosystems resulting from acute exposure to acid sulfate soil dis- charge are well documented. However, less is known about the long-term impacts of chronic acid sulfate discharge. Such discharge may create barriers to movement, potentially affecting migration of fish and invertebrate species, including commercial species. Avoidance of such discharges by adults may affect spawning migrations, while similar behaviour by juveniles may affect migration to nurs- ery habitats. As a result, the capacity of fish to access important habitats beyond the discharge point may be reduced with potential consequences for stock size. This study examined the possible exis- tence of acid sulfate avoidance behaviour in juveniles of 3 commercial fish species and 1 commercial prawn species. Schools of 10 individuals were given a simultaneous choice between 2 different water qualities in paired channels of a laboratory stream, i.e. preference-avoidance situation. All species avoided acidified water, indicating that chronic acid sulfate discharge has the potential to affect migration of these species in the field. The pH levels avoided in these experiments were well within the magnitude exhibited by natural systems. Thus, chronic acid sulfate discharge in the field could have a detrimental impact on commercial and recreational fisheries.