Southern garfish (Hyporhamphus melanochir) occurs across southern Australia including WA, SA, Victoria and Tasmania.  In WA, it is a popular commercial and recreational fishery species.  The main commercial fishery for this species in WA is in Cockburn Sound, a marine embayment in the Perth area. Approximately half of the recreational catch is also taken in Cockburn Sound.

Catch rate trends suggest a gradual decline in the abundance of garfish in Cockburn Sound over the past 2 decades, with a pronounced decline since 2011 following a marine ‘heatwave’ event in the region.   Recent fishery sampling indicates a truncated age structure (mostly aged <2 y) and a relatively high rate of total mortality (Z = 1.6) acting on this population, substantially higher than the previous estimate (Z = 0.98 estimated in 1998).  The rate of mortality and the current age composition of this population are similar to that observed in garfish stocks in SA, which have been assessed as ‘over-exploited’. Interestingly, the impact of high mortality in Cockburn Sound appears to be partly compensated for by an unusually low age-at-maturity of approximately 6 months.  This is about 1 year lower than the age at which maturity is attained by this species in SA.  It is unclear whether the low age-at-maturity in Cockburn Sound is fishing-induced or environmentally driven.