Observations of the habitats and biodiversity of the submarine canyons at Sodwana Bay

The discovery of coelacanths, Latimeria chalumnae, in Jesser Canyon off Sodwana Bay in northern KwaZulu-Natal in 2000 triggered renewed interest in the deep subtidal habitats associated with submarine canyons. Information stemming from three recreational Trimix diving expeditions in Wright and Jesser canyons between April 1998 and June 2001 revealed distinct and diverse invertebrate and fish communities in the canyons of the Greater St Lucia Wetland Park (GSLWP). In total, 69 invertebrate taxa were collected from Wright Canyon, including at least 15 new records for South Africa plus 11 potential new species and 16 range or depth extensions. Divers documented the first five coelacanth specimens and obtained information on fish distribution and abundance. Five different habitat types were recognized supporting distinct biological communities; the sandy plains outside of the canyons, scattered rock outcrops within the sandy plains, the canyon margin, canyon walls and caves and overhangs. The canyon margin is the richest habitat and supports dense communities of invertebrate suspension feeders, as well as a diverse and abundant fish fauna. Dominant canyon invertebrates included sponges, black corals, gorgonians, alcyonarian soft corals and stylasterine lace corals. These invertebrates support a diverse epifauna including basket- and brittlestars, winged oysters and other molluscs. The canyons within the GSLWP protect large populations of commercially important linefish species including the sparids, Chrysoblephus puniceus, C. anglicus, Polysteganus praeorbitalis and P. caeruleopunctatus, as well as several species of serranids and lutjanids. Additional biological sampling and standardized quantitative sampling within the canyons and deep reefs is required to develop a better understanding of their biological communities and the factors that shape them

Observations of the habitats and biodiversity oft he submarine canyons at Sodwana Bay

The discovery of coelacanths, Latimeria chalumnae, in Jesser Canyon off Sodwana Bay in northern KwaZulu-Natal in 2000 triggered renewed interest in the deep subtidal habitats associated with submarine canyons. Information stemming from three recreational Trimix diving expeditions in Wright and Jesser canyons between April 1998 and June 2001 revealed distinct and diverse invertebrate and fish communities in the canyons of the Greater St Lucia Wetland Park (GSLWP). In total, 69 invertebrate taxa were collected from Wright Canyon, including at least 15 new records for South Africa plus 11 potential new species and 16 range or depth extensions. Divers documented the first five coelacanth specimens and obtained information on fish distribution and abundance. Five different habitat types were recognized supporting distinct biological communities; the sandy plains outside of the canyons, scattered rock outcrops within the sandy plains, the canyon margin, canyon walls and caves and overhangs. The canyon margin is the richest habitat and supports dense communities of invertebrate suspension feeders, as well as a diverse and abundant fish fauna. Dominant canyon invertebrates included sponges, black corals, gorgonians, alcyonarian soft corals and stylasterine lace corals. These invertebrates support a diverse epifauna including basket- and brittlestars, winged oysters and other molluscs. The canyons within the GSLWP protect large populations of commercially importan

Notes on a remotely operated vehicle survey to describe reef ichthyofauna and habitats – Agulhas Bank, South Africa

Background: Despite their ecological and economic importance, reef habitats on the central Agulhas Bank, off the southern tip of Africa, remain poorly studied. The ichthyofauna of these habitats cannot be surveyed using trawl gear. Objective: Preliminary assessment of the use of a remotely operated vehicle (ROV) to investigate the ichthyofauna associated with deep reef habitats on the central Agulhas Bank. Method: Underwater visual surveys were carried out during ROV dives (maximum duration 60 minutes; area covered approximately 800 m2; maximum dive depth 100 m). Results & discussion: The number of detected fish species (36) compares well with that reported from fishing surveys and commercial fisher data. Most (68%) fishes appeared to be undisturbed by the ROV. Species saturation was reached after a maximum of 135 minutes survey time, but species numbers increased and saturation times shortened (34 minutes minimum) with the introduction of bait. Conclusion:  ROV surveys may represent a non-extractive alternative to assess demersal ichthyofaunal diversity in relation to habitat structure and benthic cover on temperate reefs around South Africa

Depth and habitat determine assemblage structure of South Africa’s warm-temperate reef fish

Depth and habitat are important predictors of fish assemblage structure, yet current no-take marine protected area (MPA) networks are generally limited to providing refuge for fish species that inhabit shallow waters and may exclude deep habitats essential to exploited populations. To ensure MPA efficacy at the design, uptake and management levels, baseline data on fish populations associated with deep nearshore reefs are needed. This study employed baited remote underwater stereo-video systems to investigate fish habitat associations at shallow (11–25 m) and deep (45–75 m) reef sites in the Tsitsikamma National Park MPA, South Africa. The compositions of fish assemblages at shallow and deep reef sites were significantly different. Specifically, rare species, juveniles and low trophic level species dominated the shallow reef, while deep reef assemblages were characterised by large, sexually mature and predatory fish. The body size of abundant species was also correlated with depth, with larger individuals being more abundant on deeper reefs. Habitat types were identified according to a habitat classification system established in a previous study, which resulted in four broad depth separated habitat types (defined by macrobenthos and environmental variables). Canonical analysis of principle coordinates (CAP) indicated that habitat type was a good categorical predictor of the observed fish assemblages. The CAP analysis determined that 86 % of the samples were correctly assigned to the habitat type from which they were collected, indicating that specific fish assemblages were associated with distinct habitat types. This study highlights the importance of protecting both shallow and deep reefs, not only to ensure the conservation of particular fish assemblages, but also to provide protection for all stages of the life cycle of fish species

A systematic conservation plan identifying critical areas for improved chondrichthyan protection in South Africa

The International Union for Conservation of Nature (IUCN) estimates that over a third of all chondrichthyan species (sharks, rays and chimaeras) are threatened with extinction, primarily by overfishing (as target or bycatch species). Owing to the wide-ranging distributions of many chondrichthyans, they are often overlooked in marine protected area (MPA) design. South Africa is a biodiversity hotspot for chondrichthyan species diversity, and to improve the conservation status of these species in the country's continental exclusive economic zone (EEZ), we collaborated widely to collate existing occurrence data. Ensemble models were developed for 87 species' distributions, which informed a systematic conservation planning analysis for 64 threatened and endemic species. We assessed the current representation of these species in South Africa's MPA network and identified priority areas for protection, avoiding fishing pressure where possible. Results show that many MPAs are well placed to protect chondrichthyans, especially along the east coast (KwaZulu-Natal province). Unfortunately, permissive fishing regulations within many MPA zones reduces their effectiveness at protecting chondrichthyans. Improved regulations designed to protect chondrichthyans within all MPAs should be considered a high priority. Priority areas for increased spatial protection were identified along the west coast continental shelf, the Agulhas Bank off the south coast, and south coast embayments. We found that supplementing the current MPA network by an additional 5 % of the EEZ would be sufficient to protect >30 % of the range of all 64 species, provided there is adequate enforcement. As South Africa prepares to expand its MPA estate to meet international targets, these findings can ensure that chondrichthyans are well represented. •We collaborated widely to collate occurrence data on 164 chondrichthyan species in South Africa.•Distribution models were developed for 87 chondrichthyan species.•Priority areas for protection were identified using systematic conservation planning.•Priority areas included the shelf offshore of the west and south coast.•South Africa's MPA regulations require better management to protect chondrichthyans