In Morocco, diverse saline ecosystems support both industrial salt production and the growth of Dunaliella salina, a halophilic unicellular green microalga in class Chlorophyceae, and well-known for its applications in aquaculture, cosmetics, food and pharmaceuticals owing to its significant carotenoid-producing potential. This study compares the growth and carotenoid production of six strains (DUN1–DUN6) isolated from salt ponds in southern and central Morocco to identify high-performing local strains. Among these, strains DUN3, DUN4 and DUN5 exhibited exceptional carotenoid accumulation (maximum of ∼18 mg l–1). Notably, strain DUN5 shows promise for industrial applications, combining high carotenoid yield with a cell density of 2 × 105 cells ml–1. These findings highlight the potential of D. salina as a sustainable source of beta-carotene. This research advances the sustainable valorisation of Morocco’s saline resources and promotes economic opportunities through the industrial exploitation of this valuable microalga.

Rising global concern regarding the conservation and management of shark species makes it essential to identify key ecological species to guide conservation efforts, especially species with more restricted distributions such as endemic species. The southern African endemic spotted gully shark Triakis megalopterus is currently listed as Least Concern on the IUCN Red List of Threatened Species. Though not commercially exploited, increased catches of this species by recreational fishers and high misidentification with other species of Triakidae in commercial fisheries are bringing uncertainty regarding the future of the population. Although T. megalopterus is known for localised behaviour, the extent of its site fidelity and fine-scale movements remain largely unknown. Using passive acoustic telemetry, this study assessed the species’ residency, site fidelity and movement patterns along the Western Cape coast of South Africa. Overall, the data revealed low detections, suggesting that individuals are using coastal areas not currently covered by receivers. Tagged T. megalopterus exhibited seasonal detection patterns within their zone of tagging, with increased detections during winter months. A high number of the detections occurred after the estimated parturition period; thus, the existing receiver array might not cover potential nursery areas for the species. The results also show that some individuals do undertake long-distance movements to other zones of the coastline, possibly driven by the need to locate reliable food sources. Finally, the species did not significantly use marine protected areas (MPAs), highlighting the importance of better receiver coverage and the need to expand existing MPAs.

The concept of ‘other effective area-based conservation measures’ (OECMs) and its technical guidance provide opportunities for recognising a broader range of area-based management measures that contribute to biodiversity conservation outside of protected areas. However, progress towards the recognition of OECMs for the marine environment is less advanced than for terrestrial processes. In response, South Africa developed a systematic approach to establish coherence on the OECM concept in the marine, coastal and estuarine context through rapid trial assessments of 14 management measures against six simplified OECM criteria. The objectives included identifying measures with the greatest potential as OECMs, identifying information gaps and highlighting issues that are unique to the marine context, framed within the OECM definition and assessment criteria. Among the assessed measures, only two (both restricted areas for fishing) were considered unsuitable overall owing to being short-term measures, and in one case because of its single-species focus and weak contribution to broader biodiversity outcomes. Other measures varied in their suitability, with ‘biosphere reserve marine buffer zone’ and ‘closed fishing areas adjacent to African penguin colonies’ being among the existing measures that show the most potential, aligning with five and four of the six simplified criteria for OECMs, respectively. There is substantial work needed to advance marine OECMs in South Africa and to negotiate complexities brought about by the overlapping nature of jurisdictions, management measures, rights and stakeholder interests in the marine realm, and the need for equitable and effective marine governance and management. The approach and recommendations from this exercise may be useful to other countries undertaking similar efforts.

Skipjack tuna Katsuwonus pelamis and kawakawa Euthynnus affinis are economically important tuna species targeted by artisanal fishers in the western Indian Ocean. Both species are currently considered sustainably fished despite substantial catches. Even so, ongoing management is crucial to maintain healthy populations. A comprehensive understanding of the size structure and reproductive biology of these tuna species across a broad spatial scale is essential for accurate stock assessments. This study investigated spatial and gear-based seasonal variations in the size structure of landed catches and describes the reproductive traits of the two species, including spawning season, size at maturity and sex ratio. Data were collected from the artisanal fishery in Kenya, Tanzania and Mozambique, and the recreational fishery in South Africa. The results revealed seasonal variations in size structure for both species, potentially influenced by fishing methods and local environmental conditions. The landings were biased towards male fish for both species, with sex ratios of 58% and 53% males for skipjack and kawakawa, respectively. Size at maturity (L 50) was estimated at 42.0 cm fork length (FL) for skipjack females and 47.0 cm FL for males, and kawakawa at 44.0 cm FL for females and 45.3 cm FL for males. At all study sites, spawning occurred year-round, with peak spawning activity from October to March, which coincides with the northeast monsoon. The findings provide updated information on the reproductive demographics of skipjack and kawakawa, which is crucial for assessing stock status and implementing sustainable fishery management practices in the region.

The pulmonate limpets Siphonaria concinna and S. serrata co-exist intertidally on many South African rocky shores. The two species are similar morphologically and in terms of their intertidal habitat and distribution; both lay gelatinous egg masses on the shore, but have different reproductive strategies. Siphonaria concinna has planktotrophic development involving high fecundity and small eggs. Field observations over 2 years showed that the majority of spawning occurs during summer. A discrete recruitment event follows an estimated planktonic period of 2 months. Siphonaria serrata has direct development with large eggs and lower fecundity. Spawning is seasonal, although egg masses can be found throughout the year. Newly hatched juveniles can only be detected after ∼2 months of growth. A single juvenile cohort follows ∼4 months after spawning. A comparison of the life-history traits of the two species revealed that S. concinna reproduces at a smaller size and juveniles grow faster but have a higher mortality rate than S. serrata juveniles. Adult growth rates for S. concinna are slower and likewise show higher mortality; maximum adult size is smaller and the lifespan is estimated to be shorter than that of S. serrata. Accordingly, the life history of S. serrata is characterised by reproduction at a larger size, and juveniles that grow slower and have a lower mortality rate than S. concinna juveniles. Adults grow to a larger size, suffer lower mortality and probably live longer. These life-history attributes correspond to the classic r- and K-selected traits.

Bait fishing for the common sandprawn Kraussillichirus kraussi in Durban Harbour, on the east coast of South Africa, has a history going back to the early 20th century and has been influenced by port development and political changes over time. Recent controversy has centred on the fishers’ rights to port access and on the interactions between two sectors that harvest sandprawns for bait. The two sectors are a recreational bait fishery and an unlicensed subsistence (or small-scale) fishery that sells its catches to anglers for an income, in contravention of fisheries regulations. To determine the spatiotemporal extent of the fisheries and the impacts of bait fishing on the sandprawn resource, data on the fishing effort, catch and size composition were collected monthly at the sandbank sites Centre Bank and Wilson’s Wharf in Durban Harbour. A generalised linear modelling framework was used to analyse fishing effort and sandprawn size composition. Small-scale fishers dominated the bait fishery (83%), and fishing effort peaked at low tides and on public holidays and weekends, when the market demand for sandprawns as bait was higher. Fishing effort differed significantly between sandbanks and was dynamic, shifting to Centre Bank when sandprawn abundance at Wilson’s Wharf decreased. Small-scale fishers mainly retained large sandprawns, and did not adhere to daily catch limits, such as those regulating the recreational bait fishery. The results are interpreted from a socio-ecological systems perspective, and within the context of accommodating otherwise excluded small-scale fisheries within South African fisheries legislation.

The Critically Endangered seventy-four seabream Polysteganus undulosus, a slow-growing sparid that forms spawning aggregations off South Africa, faced heavy exploitation from 1910 until a fishery moratorium was put in place in 1998. Utilising temporal samples from 1962/1963 (mid-collapse) and 2005/2006 (post-collapse), we assessed genetic diversity at six microsatellite loci. Amplification success for archived samples was low (43%), necessitating a rarefaction approach, revealing a 40% decrease in allelic diversity. Significant genetic differences between recent and archived samples confirmed the impact of overfishing. Simulation studies indicated that missing genotypes did not affect these tests, validating the genetic differences. Using a coalescent-based approach, a 10-fold decrease in effective population size (Ne) was estimated over this 43-year period (Ne = 43.88 to 4.76). Simulations provided corrected Ne of 36.86, accounting for missing genotypes that were responsible for inflated values. Assuming 25% of pristine levels in the 1960s, pristine Ne values ranged from 147 to 176 in 1910, suggesting a 96.8–98.3% genetic decline over 88 years of exploitation. This study emphasises severe genetic consequences of overfishing on P. undulosus diversity and effective population size. The results provide vital genetic baseline data for recovery assessment and conservation efforts, as well as an analytical framework to evaluate the stock decline using partial genotyping data gathered from degraded archived samples.

A commercial fishery for the Cape rock oyster Striostrea margaritacea along the north coast of KwaZulu-Natal, South Africa (western Indian Ocean), follows a 4-year rotational cycle, with each harvest year followed by 3 fallow years across four harvest zones. We analysed reported harvesting effort and catch information, and fishery-independent oyster size composition data collected over 18 years (Feb 2003-Feb 2020), to investigate the sustainability of rotational harvesting. Total harvesting effort and catches declined over the study period, but on average, the number of oysters collected per outing increased. Fewer outings in recent years were attributed to incomplete reporting and a progressive loss of access to harvest sites. Generalised linear mixed models were used to estimate trends in oyster mean size in relation to fishing method (divers and intertidal collectors), harvest zone, 4-year rotational cycles, and months spent in a zone. Oyster mean size increased from north to south along the coast. Oysters caught by divers on newly exploited deeper reefs were initially larger than those caught by intertidal collectors. Mean oyster size decreased monthly during 1-year harvest periods but recovered to pre-harvest size over 3 fallow years. The results confirmed that the current rotational harvest strategy is well-suited to oyster biology and is sustainable at the present level of effort. Improved reporting on harvesting effort and catch are required to verify longer-term spatiotemporal trends in this fishery. More effective stakeholder communication is needed to resolve potential user conflict

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.

Small pelagic fish species contribute substantially to the food security and livelihoods of local communities in developing countries. In West Africa, and particularly in Benin, small pelagic fisheries attract many migrant fishers who are key actors in the sector. This study assessed the characteristics and sociocultural impacts of the small pelagic fishery in Benin using qualitative approaches, including focus group discussions (n = 9), in-depth interviews (n = 35), a literature review, direct observations and secondary data. The findings showed that indigenous fishers from Benin and foreign fishers from Ghana are the two major groups of migrant fishers involved in small pelagic fishing in Benin. These fishers mostly use three categories of fishing gear: gillnets, seine nets, and hooks and lines. Over the period 2014–2018 the annual catch fluctuated between 1 123 and 2 040 tonnes, with the peak catch recorded in 2018, with a commercial value of €3 030 587. Apart from migrant fishers, fishmongers constitute another important pillar of the value chain. Conflicts among migrant fishers in the sector in Benin are related to landing fees and fishing gears. We discuss the urgent need to give attention to the sector through quantitative research and law enforcement to ensure its sustainability.