Population trend
Trend
Preliminary results of fish surveys done during 2012/2013 and 2013/2014 at the 21 largest and most important dams in the Free State, indicate that this species might be using dams as refugia (Barkhuizen 2015), possibly due to a decline in available preferred habitat (rivers/streams with clear and clean water with gravel/sand bottom). It may also be due to the degradation of river systems due to severe water pollution and siltation of spawning areas due to major erosion in catchments of dams and rivers. These surveys revealed established subpopulations only at five dams with complete absence of fry within the 0–100 mm size class at all dams. The majority of Largemouth Yellowfish that were caught in the dams were adult and mature fish (400 to 600 mm size class).
During the Provincial River Health Programme conducted in 2012, where fish sampling was done at 54 predetermined sites within the Orange and Vaal River systems and within a number of the major tributaries, Largemouth Yellowfish was only sampled at one site in the Caledon River (Avenant 2012, Dlomo and O’Brien 2012). Although most sites did not include major stems of the rivers, it can be expected that at least fry and juveniles would have been caught at the sampling sites. Although further research and surveys need to be done, preliminary results indicate an overall decline and a lack of successful spawning events for this species.
The drought of 2015/2016 has led to most of the tributaries of the Orange-Senqu and Vaal River systems drying up with no natural flow remaining. Some deep pools did hold water, but these areas were targeted by subsistence fishermen harvesting all fish species. It can be assumed that Largemouth Yellowfish subpopulations in rivers and streams have severely been impacted by the recent and current (2016) drought period and that no recruitment has taken place. Thus, recent data indicate that although the species might be widespread, it does not occur in large numbers where it is found. In general it can be assumed that the species’ population has decreased significantly in the past few years.
