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Tightlines - Spawning season - Rudolph Venter

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Spawning season - by Rudolph Venter

Now is a very special time of the year for most fish in the Vaal River system, namely spawning season. In this article I will focus on the Vaal River smallmouth yellowfish (Labeobarbus aeneus), its spawning behaviour and the role we play in this important process. The future of our yellowfish populations depends on how well we look after them and their offspring.

Smallmouth yellowfish become active participants in spawning once they reach a length of 30 cm (from the head to the fork of the tail) or at approximately seven years of age. This goes to show that we need to take care of the smaller fish just as much as the bigger ones.

Bruce Rainbird with a beautiful female smallmouth yellowfish of 3,2 kg. Notice the butter-yellow colour.

Heath Barnard with a male smallmouth yellowfish. Notice the slender and darker body.

The male fish is normally much smaller than the female. The male is covered in sensory papillae, making it feel rough to the touch, especially on the head. Their colour is darker and more copper on the body and olive on the back. The female in turn is butter-yellow and much wider in body width with a very distinctive, almost “bony”-looking anal fin.

Gerhard Geyser with a female 3,3 kg smallmouth yellowfish. Notice the unique anal fin.

Smallmouth yellowfish move into the shallow rapids and riffles as soon as the water reaches an estimated 17-19 °C more or less around the beginning of October. Another trigger is the rain that fills the water with nitrates and dissolved oxygen, lifting the water levels and thus inducing spawning.

A typical area were fish will spawn.

The spawning fish move into the shallow water, as low as 30 cm, deep were you can see shoals of fish with their bodies and tails out of the water. They will only spook if you are on top of them.

A yellowfish in shallow water.

The male fish surrounds a single female and fertilises the eggs as soon as the female has laid the eggs in spawning beds of gravel. As the eggs have a double layer they can withstand the rough, rocky environment and survive to hatch into small fry. The baby fish or so-called fry have silver bellies and olive-green backs with black spots. They form little shoals and find desired water where they feed on small insects and plankton. Their strength lies in their numbers; should they drift off from these little shoals, they become vulnerable to predators such as other fish or birds. A few different species will spawn at the same time in the riffles and one may see mudfish and yellowfish in the same spot.

RESPONSIBLE CHOICE

We need to act responsibly to protect and preserve the fish when they are spawning by knowing where the spawning beds are, respecting those areas, and by neither disturbing the fish nor the habitat. The fish are at their most vulnerable when they spawn and some of the bigger fish take the risk of coming to shallow water to reproduce. If we interfere with this occurrence we are in actual fact having an impact on fish stock levels and breeding fish seven years from now. This puts enormous responsibility on us as fly fishermen and anglers in general – we need to look after and respect our rivers and fish for future generations.

A few factors are impacting the fish population and health of our rivers and fish species in general:

WATER QUALITY

Water quality is determined by several factors, such as municipal sewerage systems, the mining industry and farmers’ fertilisers washing into rivers. This creates massive algae bloom that reduces dissolved oxygen and suffocates the entire ecological system; insects, plants and fish alike. Hartbeespoort Dam is a good example of this occurrence. This is probably the biggest threat to our fish species currently. Chemicals are also dumped into rivers, which is lethal to fish as this harms the gills as well as the mucous layer that protects the skin and scales.

WATER LEVELS

Water levels can have a drastic effect on fish levels. This is caused by low rain levels in summer, and is worsened by the agriculture sector that pumps water from rivers for farming purposes. Humans also regulate the flow of some rivers, and if done incorrectly, it can have a serious effect on the fish. The fish need good water levels in order to migrate and to find sufficient spawning beds and feeding areas. If gravel beds run dry it can cause insects to diminish, thus affecting the fish. Like most animals, fish will only bear young if there is sufficient food. Lots of food translates to lots of babies. No food available, very few babies. I think you get my point.

ILLEGAL NETTING

Illegal netting is a serious problem in our country, not only on the Vaal River but on all our waters in general. There are many groups of people coming together in their private capacity and taking out the nets and destroying them. This is great and we salute them for their efforts.

The unfortunate situation befalls itself in the river, especially were the yellowfish go into the rapids to spawn. The fish are caught at their most vulnerable stage in all sorts of nets and cages by the local population and then sold for a profit. This infuriates landowners as all the water cannot be monitored all the time.

If any of us come upon illegal nets we need to take them out and either burn or discard them. Once removed from the water, do not leave nets lying on the banks as birds and other land animals can become entangled in them and sustain injuries or die.

The next step is to notify the South African Police Service about the location of such netting. We should not pull up shoulders on this issue; we should actively participate in taking out nets and destroying them. As anglers we will never be free from the responsibility of reporting and destroying nets because we see more water and go to areas nobody else visits. We are therefore the only eyes and ears of the water system. If we do not report and destroy nets, it will definitely go unnoticed. I therefore humbly plead with you to actively do something about illegal netting.

INVASIVE SPECIES

Invasive species have their part to play in the diminishing number of specifically largemouth yellowfish, and secondly the smallmouth yellowfish in the river. We have seen the effect of the grass carp in the rivers of the Northern Cape, destroying the aquatic vegetation. Black bass also feed heavily on the fry of the yellowfish. Carp feed on the eggs of the yellowfish and also on the same food as the yellowfish. I do not think we can even determine the effect of invasive species on our indigenous species. By choosing not to release invasive species into virgin waters we can keep our systems pure and healthy.

CULLING FISH

South African law does permit one to keep a certain number of fish per species. This prevents overkill of fish and protects that species as determined by the scientists. I know that we as fly fishermen endorse catch and release, and that is great. Keeping fish it you are not going to use it, is a real waste. It is much better to take a photo of your catch and release it to be caught by future generations.

IMPACT OF FISHERMEN

The biggest factor is wading through spawning beds. This is detrimental to spawning yellows, their spawning ability for the occurring season and the eggs that are already in the beds. If we wade through the spawning beds, we not only spook the fish but also destroy the eggs and small fry that had hatched. By disturbing and scattering the breeding fish we stop them from laying and fertilising the eggs successfully, thus losing thousands of potential yellowfish so desperately needed for the future.

The second impact is the handling of fish. When catching a fish you should always wet your hands before handling it. This will prevent you from damaging the mucous layer that protects the fish against parasites that can attack its skin and scales.

The fish should also not be kept out of the water for longer than 30 seconds. Longer periods can harm the gills of the yellowfish. Once you have caught a yellowfish, keep it in the net in the water while getting your camera ready. Take a photo and let the fish go. Never put your fingers in the gills!

BASIC STEPS

There are a few basic steps we can take to help prevent disturbing the spawning beds of the yellowfish:

  • Do not wade/walk through spawning beds or habitat as this can disturb the spawning fish or lead to crushing and destroying the eggs. Stay in water deeper than your knees.
  • Do not target the fish in these spawning beds with flies, do not cast at them.
  • If you do catch a yellowfish, wet your hands before handling it and revive it properly before release by keeping its head in an upstream position until it is positively revived.
  • Use barbless hooks.

If we respect the fish while they are spawning, we can ensure a healthy population for the future. The choice is yours …