Swimming ability of Redfin Perch (Perca fluviatilis)and implications for passage over barriers

The redfin perch (Perca fluviatilis) is an exotic fish introduced into Tasmania in the mid1800's. It is now well established and widespread in NSW and Victoria, as well as anumber of catchments in Tasmania (Wasson et al. 1996). The species is known from thecatchments of the South Esk and Derwent Rivers, and from a number of lower and midaltitude lakes including Lake Gordon. It is widely considered a pest species and there isactive concern regarding the potential for establishment of the species in other waters,particularly lakes of the Central Highlands and Lake Pedder. There has been a recentfocus on the potential for passage of redfin perch through McPartlans Pass Canal intoLake Pedder, and via the Ouse/Shannon River system into the smaller lakes of the CentralHighlands. The species is well known from a number of larger farm and municipal dams,and lack of quality control during government and private stocking and translocation ofrainbow trout and elvers is thought to have been responsible for some of this rangeexpansion (Davies et al. 1997).Natural and manmade barriers to fish movement within stream drainages are common,and some stop fish passage through a combination of high velocity flow and verticaldrops. Most however, are typified by a high velocity, hydraulically smooth zone throughwhich the fish cannot pass due to limitations in swimming abilities. Fish use severalswimming modes, including short bursts of high speed swimming, to negotiate highvelocity water or barriers.There are two dominant modes of fish swimming - sustained swimming and burstswimming. The point at which a fish switches from using 100% aerobic metabolism, usedduring sustained swimming (where swimming can be maintained for > 30 - 200 min), toanaerobic metabolism (resulting in fatigue) is defined as the maximum sustainableswimming speed. Anaerobic swimming, characteristic of burst swimming, can only bemaintained for brief periods, typically no more than 20 seconds. Quantification ofmaximum sustained swimming and burst swimming speeds is vital for determining theneeds of fish passage. A third swimming category, prolonged swimming, is intermittentbetween 100% aerobic swimming and anaerobic swimming, where a combination of bothtypes is employed (Beamish 1978). This latter category cannot be accurately assessed ormeasured (Beamish 1978), tends to be arbitrarily defined by the experimenter (e.g. seeMitchell 1989),and is not useful in defining swimming-determined limits to barrierpassage.This project was instigated in order to characterise the swimming performance of redfinperch and to define its ability to pass barriers at specific water velocities. Work recentlyconducted by Walker (1999), and Davies and Walker (in prep.), has quantified theswimming capabilities of four common Tasmanian freshwater fish species. Their workfocused on measuring maximum sustainable and burst swimming speeds for each speciesin flume trials. They were able to develop predictive equations from these data to relatedistance traveled by each species to water velocity for a range of fish performance. Theseequations were then successfully validated by observing fish swimming performance inthe field over a range of water velocities, using experimentally manipulated flowsthrough culverts. Duration of fish passage was then estimated for six road culverts, andrelated to culvert characteristics.It was suggested to Hydro that these techniques could be used to develop a similardatabase and predictive equations for redfin perch. These data are needed in response todesign issues and queries from Hydro in relation to construction of barriers to passage ofredfin perch within Hydro catchments. This project therefore quantifies maximumsustained and burst swimming speeds for redfin perch, develops distance vs watervelocity equations and makes recommendations in relation to the design of barriers toredfin perch movement.