Squaretail Kob

(Argyrosomus thorpei)

Source: http://sacoast.uwc.ac.za/education/resources/fishyfacts/squaretailkob.htm

Squaretail kob have an elongated body and a silvery coloration with a slightly blueish sheen on the upper flanks and dorsal surface. Squaretail kob reach a maximum size of 1200mm.

Distribution

This fish has been recorded from Mozambique to the Eastern Cape but, along the KwaZulu-Natal (KZN) coast, are found primarily from Salt Rock to Richards Bay (Tugela Banks). Adults congregate in large shoals around deep reefs and pinnacles, while juveniles are found in the shallower water on soft substrata. They seldom venture near the shore or into estuaries.

Feeding

Squaretail kob are mainly predators of small, bottom dwelling fish but will feed opportunistically on other organisms such as prawns and squid. The young feed on crustaceans.

Reproduction

Sexual maturity is reached at about 350mm total length. Spawning occurs during winter and spring (August to October).

Growth

They reach maximum size of about 13kg and a maximum age of more than 10 years. The age at maturity is about 3 years.

Fishery

Both commercial and recreational skiboats as well as prawn trawlers operating on the Tugela Banks catch squaretail kob in significant quantities. The estimated annual catch of squaretail kob was 8 tonnes - (trawlers), 95 tonnes - (commercial skiboats) and 3 tonnes - (recreational skiboats) during the years 1989 to 1992. Most fish caught by the skiboat fishery measure between 300mm and 600mm total length. Squaretail kob became increasingly important to the line fishery on the KZN north coast as other target linefish species depleted. Catches of squaretail kob have decreased considerably since 1993 and only 8 tonnes were reported in 1996.

Management

• Categorised as an exploitable species

• Minimum size of 350mm (50% maturity)

• Bag limit of 5 per person per day for recreational and subsistence anglers

• Unrestricted bag limit for commercial fishermen.

Based on a study conducted by Oceanographic Research Institute in 1994 on the impact of trawling on the squaretail kob, an agreement (which is now a permit condition) was made by the trawling industry not to trawl on shallow areas (<40m) of the Tugela Banks during the months of January and February when most juveniles were caught.