SANCOR Newsletter Issue #171: September 2002
The conservation status of groupers and wrasses in South Africa
Sean Fennessy
Oceanographic Research Institute ori@saambr.org.za
South Africa is situated quite far south (its northern border on the east coast is at about 26o50’ S), so its marine waters – at least on the east coast - can be considered subtropical/warm-temperate. The west coast is dominated by the cold Benguela current, with no groupers and wrasses occurring there. We do have some small coral reefs on the north-east coast, which, at about 27o30’S, are amongst the highest latitude coral reefs in the world. These are manifested as an encrusting veneer of mostly soft corals on a submerged coastline, rather than the reef-building forms many of you are familiar with. Non-coral reefs to the south are mainly covered in algae, ascidians and sponges. Nevertheless, we have a considerable variety of groupers and wrasses, with the greatest diversity concentrated, as you might expect, in the coral areas. Smith and Heemstra (1986) list 58 groupers (epinephelinae) and 68 wrasses in our waters. On the non-coral reefs on the east coast and on reefs further to the south in more temperate waters, the communities of larger reef fishes are dominated by the sparids (seabreams), and South Africa has many endemics in this family.
Few surveys of fish abundance have been done on our reefs, nor do we have reasonable estimates of total reef area. The coastline of the region where most of the groupers and wrasses occur is approximately 900 km long, and the shelf is generally narrow. For the coral reefs, the commoner grouper and wrasse species, as determined by underwater visual census, are presented in Table 1.
Table 1: Commonly observed groupers and wrasses on South African coral reefs (from Chater et al. 1993, Chater et al. 1995).
Further south (at about 29o50’S), Stethojulis sp., Thalassoma lunare,T. purpureum, T. hebraicum, T. trilobatum andCoris caudimacula were the most common wrasses on shallow, inshore reefs, and the groupers are represented by Epinephelus marginatus, E. andersoni (an endemic) and E. rivulatus (Fennessy et al. 1998). Further south still, at about 31o20’S, E. marginatus, E. andersoni,E. rivulatus and Acanthistius sebastoides (another endemic) were common on shallow, inshore reefs, while wrasses were rare (Oceanographic Research Institute, unpublished data). E. andersoni, E. rivulatus, E. marginatus and E. albomarginatus (also an endemic) predominate on deeper (> 20 m) non-coral reefs, with E. flavocaeruleus, E. chabaudi andCephalopholis sonnerati being far less common (Fennessy 2000).Bodianus bilunulatus and B. perditio also occur on deeper non-coral reefs to the south, albeit rarely. E. coioides is quite commonly caught in some estuaries (Oceanographic Research Institute, unpublished data).
The east coast of South Africa, where most of the groupers and wrasses occur, is linear, with no barrier reefs or islands to protect it. The shelf is narrow too, and the powerful Agulhas current (all 3 knots of it at times) comes to within 11 km of the coast in places. So, there are no sheltered fishing areas for small artisanal boats – the artisanal/subsistence harvesting of fishes occurs mainly in the estuaries, with a limited amount from the seashore. There are numerous recreational shore anglers, but catches of groupers and wrasses from the shore are limited, mostly comprising E. andersoni and E. marginatus, and, even less commonly, T. purpureum and T. trilobatum. The most significant hook and line catches of groupers on deeper reefs are made by relatively small (< 10 m), outboard-powered, surf-launched boats – in both the recreational and commercial sectors. The open-access recreational sector is quite large (about 4 000 boats), while the commercial sector is restricted, comprising about 150 boats in the coastal region where groupers occur. Catches of groupers on boats are dominated by E. andersoni,E. rivulatus, E. marginatus and E. albomarginatus(Fennessy 2000), while B. bilunulatus and B. perditio are seldom caught,
although they are more commonly speared (Oceanographic Research Institute, unpublished data). Recreational spearfishers (approximately 3 000 of them) also commonly shoot E. andersoni and E. marginatus. There is some collecting of ornamental marine fishes by a number of recreational aquarists (about 1 000), and, of the wrasses, Labroides dimidiatus is frequently taken, with lesser quantities of T. lunare and T. hebraicum (Beckley 1994). Of the groupers and wrasses that are harvested, basic stock assessments have only been undertaken for E. andersoni, E. rivulatus, E. marginatus and E. albomarginatus (Fennessy 2000). E. marginatus and E. albomarginatus are over-exploited, with spawner biomass levels at 30% and 20% of pristine respectively; E. andersoni is optimally exploited, while E. rivulatus is relatively lightly exploited.
The regulations stipulate that all harvesting requires an annual permit. E. tukula, E. lanceolatus and Anchichoerops natalenesis, an endemic wrasse, may not be caught. For other groupers, recreational and subsistence harvesters are bound by a daily bag limit of 5 fish per person, and, for all sectors, E. andersoni, E. marginatusand E. albomarginatus have a minimum size limit of 400 mm (TL). Recreational harvesters may not sell their catch and aquarists may not use scuba to collect fish. There is a large marine protected area located on the northern coast where the corals occur, which has two no-take areas, and no demersal fishing from boats is permitted in the rest of the protected area. Recently, legislation was passed to prohibit driving on beaches, which has severely restricted access by recreational anglers to much of the coast. Compliance with these regulations is overseen by a conservation agency, and in the east coast province of KwaZulu-Natal, their activities include daily shore patrols and frequent inspections of recreational boat catches at the main launch sites. Catches on the coast of this province are therefore probably amongst the most closely monitored anywhere – at least as far as non-commercial fishing is concerned. Strangely, there is little formal monitoring of the commercial hook and line sector – skippers are required to submit regular catch returns, but these are known to be inaccurate. Despite the management regulations and the compliance efforts, stocks of many of the hook and line-caught species, include two groupers, are over-exploited. This is largely because of the excessive fishing effort, and regulations are soon to be passed which will introduce smaller bag limits for recreational fishers, and which will also reduce commercial effort substantially.
In summary, most of the groupers and wrasse species in South Africa are at the southernmost limit of their distributions, and are concentrated in the northern region of the east coast where the corals occur. Here they are safeguarded from exploitation by a marine protected area. Wrasses are in any case not exploited to any great extent and their status is probably healthy. Anecdotal evidence suggests that even the endemic A. natalensis, completely protected for many years from exploitation because it was easily shot by spearfishers, appears to be in a good state. For the groupers, the status of most of the species in South African waters is good – again because most species are restricted to the protected areas.
Those species that occur on non-coral reefs (i.e. outside the protected areas) are exposed to high fishing pressure, and two species (E. marginatus and E. albomarginatus) are under particular pressure because of slow growth, sex change and late maturity. Two of the other common species, E. andersoni and E. rivulatus, have more robust life history characteristics and have shown greater resilience to exploitation (Fennessy 2000; Fennessy and Sadovy 2002). All of these should benefit from the imminent reduction in fishing effort. Nevertheless, there is merit in considering the declaration of a marine protected area further to the south, to further assist with conservation of these species. Yet to be considered are the potential impacts of global warming and coral bleaching on the status of groupers and wrasses in our area (Celliers and Schleyer, in press). There is also no understanding of the relationship between reef species in South African waters and those in Mozambique, where regulations are far less restrictive and conservation/compliance initiatives are minimal.
References
Beckley, L.E. 1994. Capture of marine aquarium fishes in Natal and comments on mariculture potential based on early life history patterns. Oceanographic Research Institute, Unpublished Report. 105: 7 p.
Celliers, L and Schleyer, M.H. (in press). Coral bleaching on high latitude marginal reefs at Sodwana Bay, South Africa. Marine Pollution Bulletin.
Chater, S.A., Beckley, L.E., Garratt, P.A., Ballard, J.A. and R.P. van der Elst 1993. Fishes from offshore reefs in the St Lucia and Maputaland Marine Reserves, South Africa.Lammergeyer 42: 1-17.
Chater, S.A., Beckley, L.E., van der elst, R.P. and P.A. Garratt 1995a. Underwater visual census of fishes in the St Lucia marine reserve, South Africa. Lammergeyer43: 15-23.
Fennessy, S.T. Comparative life histories and stock assessments of rockcods (Family Serranidae) from the east coast of South Africa. PhD thesis, University of Natal, Durban. 166 p.
Fennessy, S.T., Lotter, P. and Chater, S.C. 1998. Fish species composition and abundance on a subtropical, artificial reef on the east coast of South Africa. South African Journal of Zoology 33(3):147-155.
Fennessy, S.T. and Sadovy, Y. 2002. Reproductive biology of a diandric protogynous hermaphrodite, the serranid Epinephelus andersoni. Marine and Freshwater Research. 53: 147-158.
Smith, M.M. and P.C. Heemstra (Eds.) 1986. Smith’s Sea Fishes. Macmillan Publishers, Johannesburg: 1047 pp.
