Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Investigating larval dispersal patterns: simulating river flows in an experimental tank. (#135)

Lorena Nogueira 1 , Amina Price 1 , Paul Humphries 2 , Lee Baumgartner 3 , Susan Lawler 1
  1. La Trobe University, Wodonga, VIC, Australia
  2. Charles Sturt University, Albury, NSW, Australia
  3. Institute for Land Water and Society - Charles Sturt University, Albury, NSW, Australia

The dispersal of young fish from spawning sites to nursery habitats is an essential component of the life cycle of many freshwater fish species.  Despite this, we have a poor understanding of the processes and patterns of larval fish dispersal. Larval phases of freshwater fish are generally characterized by poorly developed swimming and sensorial abilities, and for some time, it has been assumed that the larvae of many species disperse passively. However, there is growing evidence showing that dispersal for most species is active for at least part of the early life stages. In addition, the behaviour of young fish while swimming can influence the trajectory, travel speed and destination of dispersing individuals. This study aims to improve the understanding of larval dispersal in three Australian freshwater fish species, by investigating swimming behaviour of fish larvae (swimming activity, orientation towards the current vector and direction of movement), under a range of different experimental conditions. A racetrack flume, with a gradient of flow velocities, was used to simulate different flow conditions that are present in Australian rivers, hereafter classified as i) fast; ii) moderate; iii) slow, and iv) weir pool scenarios. Here, we will present initial results of the swimming behaviour of two consecutive developmental stages of golden perch (Macquaria ambigua). Preliminary results showed that during downstream movements, 76.1% of fish larvae were oriented upstream and performed active swimming movements. During the weir pool scenario, larvae actively selected low-flow zones and remained there during the entire experiment in 100% of trials. These data may significantly contribute to optimize weir operations to maximize flow that is required to maintain larval dispersal.