Leerfish Lichia amia inhabit estuaries as juveniles before moving between estuaries and the marine environment as sub-adults and adults. While adults remain mostly in the marine environment, philopatry has been observed, with individuals returning to areas previously used, including estuaries. The extent to which adults use estuaries, however, is underexplored. As such, this study aimed to investigate this species’ spatio-temporal use of the Breede Estuary in the Western Cape Province of South Africa, using a long-term acoustic telemetry dataset (from 2016–2019) for 8 sub-adult and 2 adult L. amia (690–890 mm fork length). On average, the tagged fish spent 16.6% of their days monitored in the estuary, predominantly in the lower reaches, and were also recorded along stretches of the coastline. Although the presence of L. amia was largely unaffected by month of the year, the highest monthly residency index (0.33) was recorded in May. Tagged fish were recorded entering the estuary on average at 14:29 (±01:46) and exiting on average at 09:33 (±00:54) the next day. Though L. amia appear to use estuaries less as they age, this habitat remains important even for adults, particularly before their spawning migration, emphasising the importance of maintaining the health of estuarine ecosystems for the species’ protection.

The white musselcracker Sparodon durbanensis (family Sparidae) is a highly prized shore angling and spearfishing species. This study investigated its movement behaviour along the southeastern seaboard of South Africa, using tag-recapture data. A total of 3 378 S. durbanensis were tagged between 1984 and 2023 as part of the Oceanographic Research Institute’s Cooperative Fish Tagging Project. Fish were tagged throughout their distribution range, although peaks in tagging effort occurred in the De Hoop and Tsitsikamma marine protected areas. Of the fish tagged, 99 individuals (2.9%) were recaptured. Two thirds (66.7%) of all recaptures were made within 5 km of their release site, whereas the remaining 33.3% showed ranging movements of between 5 and 843 km. Juveniles were highly resident, whereas adults showed a greater tendency to move farther, which increased significantly with increasing time at liberty. Adults moved significantly more in a northeasterly direction, and there was a tendency for fish to move northeastward in winter and southwestward in summer, suggesting the possibility of a northeastward seasonal spawning migration. There was some evidence of seasonality in the catches, with the greatest numbers of S. durbanensis being caught between September and December during the spawning season. However, there was no clear evidence that the catches varied spatially with season. We recommend that further research be undertaken on the spatio-temporal patterns of juvenile recruitment and dispersal, as well as the movement behaviour of adults, by using acoustic telemetry to determine whether spawning migrations take place and where prime spawning areas are located. Improving our understanding of the spatio-temporal patterns of this species’ spawning migration and aggregations will help improve conservation measures for this endemic seabream.

The Benguela Upwelling System, with its high variability and productivity, is challenging to monitor owing to limited in situ ocean observations. Researchers therefore often use ocean reanalysis products to simulate oceanographic conditions. We evaluated the performance of the GLORYS and BRAN reanalyses against in situ hydrographic data obtained from four research cruises in 2019 and from multi-year moored observations. The models reproduced cross-shelf temperature and salinity distributions reasonably well (r = 0.66–0.98, p < 0.001) for most stations. At the time of the cruises, GLORYS was 3–6 °C higher and had salinities 0.2–0.4 higher than in situ data in summer, but temperatures of 1–2 °C and salinities of 0.1–0.3 lower in winter. BRAN consistently underestimated temperature by 2–5 °C and salinity by 0.2–0.7. Both models performed better at depth than in the upper layers of the water column, reproducing temperature better than salinity. At longer time-scales, both models simulated current magnitude better than temperature (r = 0.77–0.79, p < 0.001). Model performance varied with latitude, with stronger correlations in the south than in the north, particularly for salinity. Our results suggest that these reanalyses need improved representation of regional ocean–atmosphere interactions and bathymetry. Thus, caution is required when using the model outputs for monitoring and operational studies.

The octopus fishery for Octopus cyanea in Seychelles plays an important role in local cuisine, culture and tourism, yet it is unmanaged unlike other octopus fisheries in the western Indian Ocean region. We conducted a rapid assessment of the octopus fishery value chain using a questionnaire survey of different actors (total of 75 respondents) across the inner islands of Mahé, Praslin and La Digue, to improve our understanding of the socio-economic importance of this fishery and to identify interventions supporting its development and management. The findings revealed a value chain distinct from others in the WIO region, with a domestic market orientation, and greater degrees of functional upgrading and vertical integration. Total annual catches were estimated at around 190 tonnes, over six-times higher than officially reported, with a total landed value of about USD 2.26 million. Key challenges include inadequate governance, inequitable value distribution, infrastructure gaps, vulnerability to external shocks, and broader social issues such as substance abuse among participants. The stakeholders support licencing, seasonal closures, minimum size limits, direct-marketing interventions and targeted infrastructure investments. This study underscores the need for context-specific management interventions that integrate economic, ecological and social information, with broader implications for the sustainable development and management of small-scale octopus fisheries in the region.

Numerous small pelagic fish species are of great economic importance and link the lower and upper levels of the marine food web. The round sardinella Sardinella aurita and flat sardinella S. maderensis coexist along their distribution range in the southeastern Atlantic Ocean, where we hypothesise that they compete for similar prey. Thus, this study aimed to compare the trophic ecology of these species off the southern coast of Angola during the austral summer and winter, by determining their diet composition and overlap, feeding strategies, trophic positions, and evaluating the correlation between their feeding intensity and remote-derived chlorophyll a concentration (Chl-a) and sea surface temperature. The results demonstarte that both species are generalists and ingest a wide range of protistoplankton and metazooplankton taxa of distinct sizes. Both sardinellas show high flexibility and adaptability to prey availability, using both filter-feeding and particulate-feeding modes. The diets were dominated by diatoms and calanoid copepods in terms of relative abundances and frequencies of occurrence, respectively, in the stomach contents. Tintinnid ciliates, fish eggs, decapod larvae, euphausiids, cladocerans and cnidarians had high wet weight contributions. The diets overlapped by 64% overall, indicating moderate competition for food, with S. maderensis exhibiting a lower trophic position than S. aurita (2.98 versus 3.49). The feeding intensity of S. maderensis was positively correlated with Chl-a, and moderately negatively correlated with SST, suggesting that species is more influenced by environmental variables owing to its lower trophic position. Trophic interactions between the two species appear to be mediated by prey sizes and availability. These findings demonstate the value of satellite-derived data as proxies to estimate the feeding intensity of these species, which will be useful to formulate regional ecological models or to predict the stock trends of S. maderensis in particular.

Predation on sea turtle nests is a natural occurrence at nesting beaches worldwide, with various animals consuming the eggs and hatchlings as part of the ecosystem. Cousine Island in the Seychelles Archipelago is an important nesting site for the Critically Endangered hawksbill turtle Eretmochelys imbricata in the western Indian Ocean; however, certain beach areas may experience losses of eggs and hatchlings of 90–100%. This study aimed to determine whether seasonal beach transformation or changes in the population density of ghost crabs (Ocypode spp.) affect the rate of predation on hawksbill turtle nests along Cousine’s singular beach, and, if so, to what extent. We found that the highly dynamic beach directly affects crab density across the length of the beach, with a significant negative relationship between beach width and crab density. Although the densities and levels of activity and predation of ghost crabs vary along the beach, crab density did not appear to influence the rate of their predation on hawksbill turtle nests on the island. Our results have allowed us to identify sites along Cousine’s beach with lower levels of ghost crab activity and predation on hawksbill turtle nests, which will enable conservationists to relocate nests to safer sites, thereby providing a valuable tool to minimise nest losses and improve sea turtle recruitment.

This study is the first in a coastal West African country to evaluate the histopathology, condition index and stress-on-stress response time of caged brown mussels Perna perna for use in pollution monitoring of coastal ecosystems. Perna perna collected from an unpolluted area on the coast of Senegal were divided and transplanted to a polluted site or maintained at the reference site for an exposure–depuration experiment. After 4 weeks of exposure, the mussels deployed at the polluted site (Port of Dakar) were then transferred to the cleaner reference site (Pointe des Almadies) for depuration. Mussels exposed to the polluted waters of the seaport had bioaccumulated polycyclic aromatic hydrocarbons (PAHs) as well as lead, copper and selenium; furthermore, changes were observed in their digestive gland histology, and their stress-on-stress response measured as median survival time (LT50) had decreased. By the end of the 4-week depuration period at the reference site the mussels showed signs of recovery, specifically in terms of their digestive tubule architecture and tolerance to air exposure. The results demonstrate that caged P. perna could be used as bioindicators for monitoring coastal environmental pollution in West Africa.

The western Gulf of Guinea is characterised by seasonal upwellings and hosts a large diversity of marine species. Although the assemblages of bottom fishes and benthic organisms are periodically assessed, there has been little research investigating these in tandem. We investigated the shelf bottom assemblages along Côte d’Ivoire and Ghana using data from a 2019 scientific research survey. Standardised species abundances were significantly associated with various environmental bottom conditions recorded on nearby CTD stations. We then used a clustering framework for identifying main assemblages, and compared them with site ordinations fitted with environmental parameters through detrended correspondence analysis. Three groups were determined, structured primarily by depth and distance to shore along an easting gradient, highlighting faunal discontinuities related to different hydrographical conditions and bottom types. These were a shallow coastal assemblage, a deeper sub-thermocline assemblage, and an intermediate assemblage of soft and rocky environments. The steep slope along Côte d’Ivoire was associated with a clear separation between the shallow coastal and deeper assemblages. Species diversity increased longitudinally to the east, commensurate with the broadening and gentler slope of the shelf along Ghana, which was associated with habitats that are more heterogenous. Further study is needed to understand the variability and sensitivity of these ecosystems in relation to upwelling seasonality and environmental conditions, especially as the region experiences intense unmonitored fisheries and warming-induced changes in water stratification.

This study investigated the spatial and temporal distribution of shallow-water hake Merluccius capensis off the south coast of South Africa, using 1 807 females collected by bottom trawling during industry and research surveys between 2014 and 2016. Mean body size increased significantly with bottom depth (p < 0.05), although the relationship was weak (r 2 = 0.22). The vertical adjustment of the position in the water column between the immature and regressing stages of maturity appeared minor; however, hake in the regenerating stage were found significantly deeper, typically at ∼225 m compared with at 160–200 m for the other maturity stages. Because M. capensis is a serial spawner, females tended to move upwards by ∼25 m to release egg batches, doing so in April–May and in September, as evidenced by a higher incidence of actively spawning females. A latitudinal distribution pattern was also apparent as females generally moved northwards before spawning (to 35.4°–35.3° S), followed by spawning (centred at 34.9° S), and subsequently returning southwards (to 35.2°–35.4° S). These latitudinal movements were coupled with longitudinal relocations eastwards during pre-spawning (21.7°–21.8° E) and farther eastwards when spawning (22.8° E), and then returning to the west after spawning (21.2° E). Thus, the various phases of the spawning cycle of this species are characterised by specific spatio-temporal dynamics.