Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

How much screen time is too much for baby golden perch? (#120)

Patrick McSweeney 1 2 , Craig Boys 2 , Simon Mitrovic 1 , Matthew Balzer 1 3
  1. University of Technology Sydney, Glebe, NEW SOUTH WALES, Australia
  2. NSW Department of Primary Industries, New South Wales Fisheries, Port Stephens, New South Wales, Australia
  3. Department of Primary Industries , Department of Primary Industries and Environment, Sydney, New South Wales, Australia

Fish protection screens are increasingly being used in Australian rivers to prevent native fish from being lost at water diversions. Australian specifications for their design have been produced prescribing that approach velocity (the perpendicular flow 8 cm in front of the screen) should not exceed 0.1 m sec‑1. This specification is based on data of swimming performance of juvenile fish and it is uncertain to what degree it provides protection for larvae. The swimming performance of golden perch larvae at three developmental stages (protolarvae, postflexion and metalarvae) was observed in front of a fish protection screen in a specialised swimming flume. Approach velocity and temperature was varied, and we collected data on the likelihood of impingement and the time it took for impingement to occur. We also quantified what type of swimming behaviour fish employed to avoid impingement. Protolarvae were most susceptible to impingement with around 100% becoming impinged at 0.1 m sec‑1. While protolarvae have a relatively poor sustained swimming ability, by seeking hydraulic refuge afforded by surface roughness, they could still avoid impingement for 10-25 seconds (depending on water temperature). Ability to avoid impingement improved substantially as larvae developed, with only 40% of postflexion larvae and 0% of metalarvae being impinged at 0.1 m sec‑1. Body development of these older stages enhanced their use of burst swimming behaviour to avoid impingement. This burst behaviour was further enhanced at 25oC when compared to 20oC. The current Australian specification for fish protection screen design, which recommends approach velocity not exceed 0.1 m sec‑1, will provide protection for larval golden perch, with protection improving significantly as the larvae move beyond the protolarvae stage.