Silver Kob

(Argyrosomus inodorus)

Cape kabeljou, Silver kabeljou

Species is currently under revision for inshore trawl component

1. What is it?

Silver kob (Argyrosomus inodorus) are resilient, fast growing, endemic fish found on shallow inshore sandy bottoms (juveniles) and moderate to low reefs around 20-120m (adults). Kob are easy targets for commercial and recreational linefishers. A stock assessment published in 2013 revealed that stock levels are very low (around 21% of pre-fishing levels). Silver kob are currently considered as over-exploited and overfished.

2. How was it caught or farmed?


Silver kob are caught using the traditional rod-and-reel method of the linefish sector. Linefishing is a relatively selective fishing method which targets a large number of species many of which are reef-associated but also includes a few pelagic species. When targeting pelagic linefish species, the linefishery is not likely to cause significant damage to overfished, vulnerable or ETP species, which are nearly all reef-associated. The reverse is true when targeting for reef-associated linefish species like silver kob. The fishery has few discards and there are very few “non-target” species landed in the sector.

Inshore demersal trawl

Silver kobs are are caught as bycatch in inshore trawl fishery for hake (MSC certified) and sole using trawl nets. In the inshore zone, trawl nets are dragged along the sea bed at depths in the area from the coast to the 110 m isobath or to 20 nautical miles from the coast, whichever is the greater distance. Demersal trawling is known to damage the seabed; the extent and impact of this damage remains unknown. This methodology is not selective, however, and a number of other benthic species are often caught in the nets as well. Seabird bycatch was highlighted as an issue and the subsequent introduction of tori lines (lines covered in coloured streamers making attachment lines more visible to birds) has led to a decrease in bird mortalities.

3. Where is it from?


Silver kob are captured within the inshore zone from the northern Namibia to southern Transkei. Management for the sector is considered partly effective. In South Africa, this sector is principally managed through a total allowable effort (TAE) limitation and there are additional restrictions to protect overfished species such as bag (5pp/pd–for anglers west of Cape Agulhas and 1pp/pd – for anglers east of Cape Agulhas) and minimum size limits (> 50 cm) for recreational fishers. There is some concern over the impact of the small-scale fishery rights allocation beyond the recommended TAE, the continuously growing recreational sector and increases in illegal night fishing using gill nets in estuary mouths.

Inshore demersal trawl

Silver kobs are caught between Cape Agulhas and the Great Kei River at depth shallower that 110m. Management is considered to be partly effective. Management is mainly directed at the target species hake (MSC certified) and sole in the form of Total Allowable Catch (TAC) and permit limitations. Some ecosystem-based management measures have been implemented, such as the use of tori lines to minimize seabird interactions and limited fishing areas. There is a fishery conservation project (FCP) presently underway seeking to test a co-management approach that would bring under management 10 non-target species in the sector. Additional ecological concerns are little information on impacts to sensitive shark, skates and ray populations as well as impacts to the seabed. Efforts are underway to improve the scientific observer coverage at sea for this sector to better understand ecosystem impacts.