Department of Agriculture, Land Reform and Rural Development

Abstract Contributions and effects of anthropogenic activities on the underwater soundscape of the sub-Antarctic regions remain poorly studied. Over a 21-month period (April 2021 to December 2022), we recorded underwater noise levels amid two sub-Antarctic Prince Edward Islands (PEIs) within an offshore marine protected area with the aim to quantitatively investigate the sources of underwater noise and the impact of such noise on the detectability of marine mammal vocalizations. We measured underwater noise levels within the low (20–120 and 121–800 Hz), medium (801–25 000 Hz) and high (25 001–48 000 Hz) frequency bands. Wind speed was the primary predictor of low and medium frequency underwater noise levels, whereas iceberg volume was the primary predictor at the high frequency band. Probabilities of detecting vocalizations of Antarctic blue, fin, humpback, Antarctic minke and killer whales decreased with increasing noise levels. On the contrary, probabilities of detecting sei and Madagascan pygmy blue whale vocalizations increased with noise levels. Overall, these novel results indicate that geophonic noise dominates the underwater soundscape of the PEIs in the absence of intense anthropogenic activities such as marine traffic, and that the detectability of marine mammal underwater vocalizations is species-specific.

ABSTRACTUnderstanding how genomic structure links with ecological and evolutionary processes is critical for forecasting species responses to dynamic marine environments, especially in commercially exploited marine species, where fishing pressure can impact genomic integrity. Here we investigate Merluccius paradoxus, a commercially exploited demersal fish that appears to be undergoing a range expansion along the southern African coastline. Using whole‐genome sequence data of individuals from across the species' distribution (n = 37), we reveal that sex‐linked divergence, rather than geography, is the principal driver of genomic variation, challenging conventional assumptions of regional geographic population structure. Divergence was concentrated on autosomal regions (primarily large regions on Chromosomes 1 and 2), rather than known sex‐determining (SD) regions (Chromosome 9), and did not have structural variants or extended linkage disequilibrium (LD). Instead, patterns were consistent with sex‐specific directional selection acting on genes enriched for neuronal function, metabolism and muscle development, traits that are likely linked to behaviour, physiology and environmental tolerance. Males had reduced nucleotide diversity (π), low observed heterozygosity (Ho) and longer runs of homozygosity (ROH) in these regions, suggesting recent selective sweeps or a reduced effective population size (Ne). Together with spatial differences in sex distribution and genomic diversity metrics, results suggest that males and females may differ in both range dynamics and adaptive potential. As M. paradoxus continues to shift its distribution across geo‐political boundaries, sex‐biased adaptation may have important consequences for reproductive output, resilience and sustainable fisheries management under a changing climate. This study highlights the need to incorporate sex‐linked genomic variation into conservation planning, particularly in transboundary systems vulnerable to cumulative pressures of fishing and environmental change.

Abstract Localized metal loss (LML) in pressurized tubes is a primary contributor to tube failures and unplanned shutdowns in industrial boilers. Initially, these tubes may have inconspicuous anomalies introduced during manufacturing, testing, and inspection. Over time, as the vessels are deployed and exposed to harsh environmental, operating, or aging conditions, these anomalies evolve, eventually leading to their failure. In this paper, detailed investigative studies on various metal loss flaws were carried out to acquire insights on their failure behavior and mechanism, especially as they progress from very small size to lengthy size. Three investigations were carried out to identify which geometric parameters are most critical for predicting failure of the tubes and to what extent will they influence their failure. First, a range of real flaws that failed while operating under high internal pressure in a steam boiler were considered. The study compared two different modeling methods for evolving flaws to their failure geometry. The outcome shows that for most flaws, the failure evaluation is insensitive to the method of evolving the flaw to failure. Second, all the flaw geometries were modeled using the same material and operating conditions and their failure behavior studied. The findings show that failure pressure depends solely on the flaw thickness, and not on the other flaw dimensions, except for pinhole flaws. Finally, a range of flaw geometries, spanning the space from localized pinhole flaws to wide lengthy flaws, were investigated. Outcomes of these studies show that failure pressure for small flaws is sensitive to the flaw geometry. However, the failure pressure ceases to depend on the flaw length once the flaw length is greater than twice the tube diameter, and ceases to depend on the flaw width when the flaw length is greater than the tube diameter. These results suggest that gross plastic collapse is not the dominant failure mechanism for small flaws. However, for flaws with a length at least twice the tube diameter, the flaw dimension which predicts failure is the tube remaining thickness in the deepest part of the flaw. These studies establish the applicability limits of gross plastic collapse analysis for pressurized tubes experiencing metal loss and demonstrate opportunities for simplifying flaw analysis for sufficiently large flaws. Ultimately, the insights from this study will contribute toward appropriate preventive maintenance of these critical assets while in operation.

ABSTRACTUnderstanding of the spatio‐temporal occurrence of cetaceans post the whaling era is essential for protecting and improving management strategies of these marine mammals. To determine the monthly and diel acoustic occurrence of four baleen whale species relative to environmental conditions off the west coast of South Africa, we collected passive acoustic monitoring data within Child's Bank marine protected area in January and May through October 2024 at various water depths. Burst tonal calls of the southern African Bryde's whale offshore population were detected in January and May through July with the highest occurrence in January. Humpback whale songs and southern right whale gunshot sounds were detected from May through October with high occurrence in September and with smaller modes in other months. Antarctic minke whale bioduck calls were also found in June through October, showing high occurrence in August through October. Calls from an unknown source with similar characteristics to Antarctic minke whale bioduck calls were present in May, July, and August with the highest occurrence in August. Diel acoustic occurrence of Bryde's, southern right, Antarctic minke, and minke‐like whale calls indicated that these animals vocalised more during the day while humpback whales were more vocally active at night. Sea surface height and sea surface temperature, either separately or in combination, were the most important predictors of whale acoustic occurrence, highlighting the influence of environmental conditions on the distribution, habitat selection, and ecology of these whales. Overall, this study advances our understanding of the movement, occurrence, and behavioural patterns of several baleen whales relative to environmental conditions. It also provides the first description of the southern African Bryde's whale offshore population's call characteristics, which will be useful at guiding future studies to acoustically differentiate between it and the inshore population.

ABSTRACTBlackleg, caused by the fungal pathogen Leptosphaeria maculans, is a serious constraint to canola production in the Western Cape province of South Africa. Host resistance forms an essential part of integrated blackleg management and includes the deployment of major resistance genes in canola cultivars. However, the intensive use of resistance genes can result in resistance breakdown. To manage the efficacy of resistance genes, changes in avirulence gene frequencies present in pathogen populations should be monitored. This study analysed whole genome data of 264 L. maculans isolates collected between 2020 and 2022 in the Western Cape province, South Africa, to determine genotypes of alleles at 12 avirulence loci. The resistance of commercially available cultivars was also evaluated in field trials conducted at four locations from 2021 to 2023. Results revealed low frequencies of AvrLm1 (6.44%), AvrLm4 (0.38%) and AvrLm6 (36.82%), indicating pathogen adaptation to the corresponding resistance genes, Rlm1/LepR3, Rlm4 and Rlm6, extensively deployed over the last two decades. In contrast, AvrLm7, corresponding to the recently deployed Rlm7, was present in 98.86% of isolates. In support of these findings, results from the field trials showed that the presence of Rlm7 in cultivars is associated with lower blackleg disease severity. Lower severity in some cultivars lacking Rlm7 suggests the influence of minor gene resistance. As expected, high frequencies (> 90%) were observed for avirulence genes corresponding to resistance genes not deployed locally. To prolong Rlm7 efficacy and potentially restore other resistance genes, rotation of resistance genes and regular avirulence allele monitoring are recommended.

Indigenous people of South Africa have for many years relied on Indigenous Knowledge to ensure food security. For example, they can identify different types of edible wild fruits, vegetables and roots, they know when to plant which types of food, how to plant them, when and how to harvest and process the food and how to preserve the food to ensure food security. Agriculture, based on Indigenous Knowledge, ensures the production of a variety of indigenous foods. However, the knowledge on these Indigenous foods is slowly being lost. This is mainly because indigenous knowledge is tacit and kept in the minds of knowledge holders whom most of them are no more. Without its protection and promotion, the knowledge is susceptible to change or completely being lost.

Due to the rapidly increasing population around the world, food access and availability has become a paramount concern to various developmental agencies and institutions. This is because food security and vital food systems are of great importance. One of the most significant current discussions in agriculture is the use and application of indigenous agricultural practices (IAPs) which have been used by local farmers to enhance household food security. Despite their significance, most of IAPs are at risk due to urbanization, cultural assimilation, and globalization. This study applies an explorative design, with an indigenous paradigmatic lens to illustrate the significance of these practices in ensuring food security. The data was collected through semi structure interviews with local farmers of Bakgatla-ba-Kgafela and was analyzed using thematic analysis. The study finds that the documentation and preservation of IAPs is crucial for ensuring sustainable food systems and food security. It is therefore concluded that new and innovative approaches to agriculture are needed.

Plastic pollution is a significant environmental issue, with plastics comprising a large portion of municipal and industrial waste. These materials do not decompose easily, leading to severe environmental problems. A four-year project under the African Regional Cooperative Agreement for Research, Development, and Training Related to Nuclear Science and Technology (AFRA) is aligned with Sustainable Development Goal (SDG) 14, which aims to conserve and sustainably use the oceans, seas, and marine resources. The Sustainable Development Goal (SDG) 14, focused on life below water, through the target 14.1, urges nations to prevent and significantly decrease marine pollution, particularly from land-based activities, including marine litter by 2025; and through the target 14.a, to increase scientific knowledge, develop research capacity and transfer marine technology, to improve ocean health and to enhance the contribution of marine biodiversity to the development of developing countries. The regional project builds on previous International Atomic Energy Agency (IAEA) projects and national programs, aiming to enhance the capabilities of member states to monitor microplastics (0.3 – 5mm) in beach sand and surface seawater. The project involves collaboration among member states with varying levels of expertise, fostering knowledge transfer and capacity building. Key activities include project setup, harmonizing national programs with the project’s objectives, and developing training and capacity-building. Sampling and laboratory kits are standardized, and a common protocol is used by all member states to generate data. These efforts aim to create a regional network of laboratories equipped to monitor and assess plastic pollution to supply UN SDG with comparable data for 16 African countries. This regional project is part of an IAEA inter-regional project which aims to provide comparable microplastics data to UN SDG14.1.1.b, currently from 99 countries. The harmonised protocols of IAEA for microplastics (0.3 – 5mm) for UN SDG reporting and the progress made within the African region are presented here.