The control of blood flow through the gill of a notothenioid fish, Pagothenia borchgrevinki, was examined by isolating a gill arch and perfusing it with saline. The effects of drugs on the afferent and efferent branchial arteries, the vessels supplying blood to the gills, was also investigated. A single gill arch was dissected from a P. borchgrevinki. Afferent (into the gill) and efferent (out of ... the gill) blood vessels were located and cannulated to allow perfusion of physiological saline through the gill. The pressure required to drive fluid through the gill was recorded, as were flow rates from the primary and secondary efferent routes. Bolus injections of vasoactive drugs were used to measure their contractile effect on gill tissue. Once isolated, blood vessels (afferent and efferent arteries) were used to examine the control of vessel diameter. Artery rings (1mm x 2mm) were cut from the vessel end close to where they were severed from the gill and mounted in a myograph. Stable tension was obtained and drugs (adrenaline, noradrenalin, isoprenaline, acetylcholine, 5-hydroxytryptamine and angiotension) were added to measure the contractive forces exerted by the blood vessels supplying the gill.