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Elasmobranchs play important ecological roles but are highly threatened. Understanding their habitat use and abundance is crucial for the management and conservation of these species and their habitats. While some species are known to use estuaries as vital habitats (e.g. feeding or nursery grounds), this remains an understudied area. A multi-method approach was used to survey the Keurbooms Estuary on the south coast of South Africa, over two years, to quantify the diversity, relative abundance and habitat use of elasmobranchs in this system. The survey methods were baited remote underwater video (BRUV), boat-based visual sightings, and unmanned aerial video (UAV). Opportunistic sightings were also collected. Six elasmobranch species were observed, with significant differences in community composition between the methods. Whereas effort was skewed towards BRUV surveys, the boat and UAV surveys recorded more elasmobranchs more frequently, and opportunistic sightings recorded the highest diversity. The common eagle ray Myliobatis aquila was the most abundant elasmobranch species and the only one recorded year-round; most individuals (93%) were juveniles, suggesting the Keurbooms Estuary may be a nursery area for this Critically Endangered species. The duckbill ray Aetomylaeus bovinus and common smoothhound shark Mustelus mustelus were observed during summer, the latter forming large aggregations. Another three ray species were recorded rarely. This study highlights the benefit of using a multi-method survey approach for shallow ecosystems and reveals the Keurbooms Estuary as an important habitat for elasmobranchs. [ABSTRACT FROM AUTHOR]

Data collected from mark-recapture programmes have proven invaluable in assessing the movements and growth of numerous fishery species along the South African coastline. This short note reports on tag and recapture information on the Vulnerable endemic lesser guitarfish Acroteriobatus annulatus. This species appears to exhibit site-affinity behaviour, with an observed mean distance moved of 38.5 km (SD 121.4, range 0–726 km). The recapture of two individuals (tagged as adults; ∼100 cm total length) 6 and 12 years after tagging suggests that the maximum age for this species is likely more than double the current maximum recorded age of 7 years (estimated from vertebral ring counts). This has major implications for the management of this bycatch species (with a declining population trend), and for other guitarfish species occurring in South Africa for which the maximum age is currently unknown. [ABSTRACT FROM AUTHOR]

Ecklonia maximadominates kelp beds on the west coast of southern Africa, and is commercially and ecologically valuable. Some plants lose all their secondary blades (fronds), leaving only the gas-filled bulb and short primary blade at the top of the stipe. These ‘bald’ kelps may persist for months or longer, occupying substratum space but contributing little to productivity. We investigated natural causes of balding in five kelp beds in False Bay, South Africa, and the effect of simulated commercial frond-harvesting on loss of fronds. Densities of sporophytes with and without fronds were measured at the water surface during low tides. Generalised linear modelling analysis showed a significant relationship between balding and site (whether sheltered from or exposed to swell/wind), position in the kelp bed (shoreward or seaward) and totalE. maximadensity. We conclude that balding is caused mainly by drying of meristematic basal regions of fronds during emersion of kelp heads at low tide. After partial harvesting of fronds, kelp heads floated higher out of the water, but after 95 days frond loss was significantly higher only when fronds were cut too close to the primary blade, possibly because of damage to meristematic tissue. Nevertheless, increased emersion that results from frond-harvesting may increase desiccation and blade loss and we suggest caution in setting harvest limits for this kelp. [ABSTRACT FROM AUTHOR]