Bioacoustics of Kuhlia rupestris

KNOWLEDGE GAPS Regional and local connectivity The study by Feutry et al . (2012a) was a first step towards understanding the connectivity in K. rupestris , but lots of it still remains unclear. For management purposes, it would be very useful to know if population structure occurs at a finer scale than the one identified by these authors. Indeed, a better understanding of larval dispersal and recruitment scheme (external or self-recruitment) in freshwater are one of the fundamental components to provide appropriate management plans at regional and local scales. For example, in areas like Queensland and Réunion Island , where the conservation of the species is a concern, it would be interesting to know if the population mainly relies on self-recruitment or if surrounding islands also contribute to recruitment and in which proportion. The same question also applies at an even finer scale, river drainages potentially having some degree of independence from one another within the same island. The knowledge of fine scale genetic diversity is also important if breeding programs are to be used for restocking ( Hoskin et al., 2015 ). The use of thousands of genetic markers now easily available ( Davey et al., 2011 ) and close-kin analyses have the potential to fill this knowledge gap ( Planes et al ., 2009 ; Grewe et al ., 2015; Feutry et al ., 2017 ). The genetic data collected for these analyses could also be used to provide estimates of population size and biological parameters such as mortality and breeding success ( Bravington et al ., 2016 ). Reproduction, recruitment and river migrations Size at sexual maturity is an important parameter to gather as it is often used to define a legal size for fishing. Previous studies suggest regional variability exists in this species and therefore, local studies should be undertaken if this parameter is judged important to ensure population sustainability. Another clear knowledge gap for K. rupestris is the location of breeding and spawning grounds. It is suspected that K. rupestris spawn at sea or in the estuary plume, but this has never been observed. Despite some indications of the moon phase playing a role, exact timing also remains quite unclear. Gathering information on this critical part of the life cycle could help define temporary protected areas along the shoreline. This could be achieved thanks to acoustic, radio or RFID telemetry studies. Outcomes from telemetry could then inform targeted fishing/netting effort to recover actively spawning fish and possibly eggs and larvae. Telemetry could also provide information about upstream and downstream fish movements, another uncertain aspect of K. rupestris biology. This includes its ability to overcome obstacles, its behaviour during extreme events such as floods or draughts, but also water flow requirements to complete its life cycle. The importance of maintaining perennial flow at the sea/river interface has been highlighted by Marquet (ER, 2015), but if better knowledge of timing for spawning migrations or recruitment was available, it might be possible, for example, to accommodate water requirements for hydroelectric power stations while having minimal impact on the species survival. Overall, the accessibility between growth and breeding habitats is one of the key parameters for diadromous population conservation. For Kuhliidae , estuaries are key habitats both as corridors between freshwater and marine habitats and as possible spawning areas. Knowledge about factors affecting the ecological status of estuaries should be improved and monitored on an interannual basis. Another reason to study fish movements would be to test whether adults are capable of migrating from one river to another. Such capability would certainly improve survival to rapid and extreme changes in insular freshwater environments ( Feutry, 2011 ). Additional data on the timing of fish migration could also inform the management of human activities, such as fishing in estuaries. Finally, except for its duration, very little is known about the pelagic larval phase. Information on larvae behaviour in the water column could help refine larval modelling approaches such as the one used by Feutry et al. (2012a) in the Coral Sea. A better understanding of the cues leading the larvae towards estuaries would also certainly help taking management decisions.