Olfactory cueing responses in the early stages of a marine estuarine-dependent fish species in South Africa

Abstract

Many marine fish species depend on estuaries as nurseries for their vulnerable life stages. Consequently, successful recruitment into estuaries by the larvae and juveniles of marine estuarine-dependant fish such as Rhabdosargus holubi (Sparidae) is vital to completing their lifecycles and thus maintaining populations. This species is known to be attracted to the water of riverine and estuarine origin, potentially via olfaction of chemical cues. However, the specific cues and cueing mechanisms involved in these recruitment responses have yet to be fully elucidated for many species utilising estuaries as nursery areas. In this study, choice chamber flume experiments were used to test the chemical attraction of fish to water from different sources to understand further the mechanisms and cues involved. Rhabdosargus holubi juveniles were attracted to the water of riverine and estuarine origin, as the larvae were previously shown to do. These fish were also attracted to exudates from seagrass that occur naturally in their preferred estuarine habitats. The results of the study highlight both the importance of conserving vegetated habitats and managing adequate freshwater flow into estuaries, as well as the need for more research on fish cueing into nursery areas.