The Knysna Estuary is a popular fishing spot for many subsistence and recreational fishermen who also collect bait from within the estuary. These bait are mostly mudprawns, but more and more people are now also collecting polychaete worms. Polychaetes come in many different shapes and sizes. Some have very simple body-forms like their close relatives the earthworms, but many are more elaborate, with antennae and tentacles on their heads, legs called parapodia, and frilly gills on their backs. Many are very small, so small that they can live in the spaces between sand grains. But those used as bait are bigger; the smaller species may be about 6cm long, but some can be nearly a metre long. Fishermen have many different names for their favourite worms, such as the pudding worm (so called because they are rolled into a ball or ‘pudding’ when put onto the hook), the moonshine worm, the wonderworm, the mussel worm and the coral worm. Unfortunately, there appears to be little consensus among fishermen and scientists as to which worm goes by which name.
Over the last 20 years the estuary and surrounding area has undergone extensive change which may have increased the pressure on the baiting resource within the estuary. These include the development of the Thesen Island luxury housing estate and the nearly doubling of the invertebrate reserve (i.e., the no baiting zone). To make matters worse, recent eutrophication events have led to extensive blooms of Ulva which may affect the chemistry of the sediment and consequently animals such as bait species which live in the sediment. Although a wonderworm by any other name would still be as tasty (to the fish, that is), it is important that we know which worms are utilised most frequently to help manage the resources more effectively. This is particularly important in the Knysna Estuary where breeding worms and prawns in the reserve populate the area from which bait can be collected.
A survey-based study investigating the baiting practices of fishermen within the estuary is currently being conducted by Stellenbosch University (a student, Alheit du Toit, under the supervision of Carol Simon), members of the Knysna Basin Project (Frances and Peter Smith and Louw Claassens) and SANParks (Kyle Smith). Data collected so far suggest that the most popular worms collected are the blood- and moonshine worms. The moonshine worms may be one of two species of Diopatra (also called case worms because of the tubes that they build; these may extend like chimneys decorated with bits of shell above the sand), both of which are either alien or (more probably) had been misidentified and are actually indigenous worms.
The aims of this study are therefore to:-
- Identify the many different worms used as bait and to develop some consensus around their common names. This study will be conducted at various fishing sites in the Western Cape, including Knysna and Sedgefield.
- Clarify the identification of the Diopatra species in the Knysna Estuary.
We hope that you would be eager to donate some of your worms to us when we are out hunting.