Smallmouth Yellowfish

Every Angler wants to go out there and Catch his/Her PB. We all strive to catch more, Better, Bigger and faster. If you honestly believe that under normal circumstances Anglers cannot wipe a species out then you need to go look at the History Books. The Large mouth and small mouth YELLOW fish were just about wiped out. Controlled measures were put in place with hefty fines to any angler who was caught with a Yellow in his Net. This was more than 20 years ago and only now are we seeing Yellows again on a regular basis. It is still illegal to catch and keep them.

The Yellow Fish is very slow growing specie. Much slower and a lot more sensitive to environmental changes than other HARDY species. The yellow fish stresses very quickly and it is a well documented fact that Yellow fish Die if not put back in the water very quickly after being caught. Time frame under 3 minutes. Even when put into a keep net the Yellow fish dies. It must be allowed to swim freely.

Status

The smallmouth yellowfish is listed as “Not Threatened”, as it is still widespread across the Orange-Vaal River system and is in abundance in most suitable habitats.  However, recent fish kills in the middle Vaal river and some tributaries are a cause for concern, as they have the potential to cause substantial damage to valuable recreational fisheries. 

Threats

Water pollution in the form of effluent from municipal sewerage plants, agriculture and mine water return flows perhaps pose the most serious threat to yellowfish in the middle to lower Vaal river and several of its tributaries.  Whereas most of the ingredients of the effluent are not directly toxic to fish, the enriched water facilitates algal blooms that reduce dissolved oxygen concentration to lethal levels.  (see NCYWG ongoing research report).
Additionally, bacteria that break down organic waste produce by products such as ammonia and nitrites.  At elevated levels these nitrogenous wastes are highly toxic to fish and even sub lethal concentrations can seriously damage their gills.
Over abstraction of water from tributaries during the dry Winter months result in stretches of river being laid dry, killing fish and their food.  In stream dams such as the Vaal and Gariep dams are barriers to fish migration and also regulate river flow, modifying food driven flows for much of the year.
Illegal netting takes place all over both river systems, usually near informal settlements.  However some land owners or entrepreneurs trying to make extra money from selling fish, are also implicated.  Law enforcement operations in which the South African Police Service is actively involved are under way.
Several alien fish species are now common in parts of the Orange and Vaal rivers.  The predatory largemouth bass flourish in several dams on tributaries of the Vaal and in the Barrage below the Vaal dam.  Carp are widespread and common in the system and compete with smallmouth yellowfish for food as well as eating yellowfish eggs at spawning time.  The recent explosion of grass carp in dams of the middle Vaal river is seen as a potentially serious threat as this prolific species grows to more than 20kg and is an obvious competitor for food.
Some of the above information was gotten off the website www.yellowfish.co.za if you want to read more about them in detail please click the website link.

Grass Carp

In the last 5 years or so we have seen a dramatic increase in Grass Carp in the Vaal water system. Further […]

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