The South African Institute for Aquatic Biodiversity (SAIAB), is involved in research, education and in applications of its knowledge and research to African fish fauna, for either economic or conservation benefit.The institute originally established in 1969, was formerly named the JLB Smith Institute of Ichthyology, in honour of Professor James Leonard Brierley Smith, who named and described the living coelacanth Latimeria chalumnae. The JLB Smith Institute of Ichthyology received recognition as a national research entity, renamed as the South African Institute of Aquatic Biodiversity in 1999.Situated in Makhanda, Eastern Cape, the South African Institute for Aquatic Biodiversity (SAIAB) is an internationally recognised centre for the study of aquatic biodiversity.As a National Facility of the NRF, SAIAB serves as a major scientific resource for knowledge and understanding the biodiversity and functioning of globally significant aquatic ecosystems. With both marine and freshwater biogeographical boundaries, southern Africa is ideally placed to monitor and document climate change.From a marine perspective South Africa forms the southern apex of a major continental mass, flanked by very different marine ecosystems on the east and west coasts, and projecting towards the cold southern Ocean large marine ecosystem. SAIAB's scientific leadership and expertise in freshwater aquatic biodiversity is vital to the national interest when dealing with issues arising from exponentially increasing pressures of human population growth and development..
Marine ecosystems are characterised by complex, dynamic, and non-linear interactions that challenge traditional ecological modelling approaches. Recent advances in computational methods, particularly Graph Theory (GT), Graph Neural Networks (GNNs), and Reinforcement Learning (RL), offer promising tools for analysing, predicting, and managing these systems. This study presents the first comprehensive systematic review that jointly examines the application and integration potential of GT, GNNs, and RL in marine ecology. Following a PRISMA-guided methodology, 122 studies published between 2000 and 2026 were analysed to evaluate methodological trends, application domains, theoretical rigour, and practical relevance.The results show that GT remains the most widely used and mature approach, particularly for analysing ecological connectivity, food webs, and conservation planning. In contrast, GNNs and RL are emerging methods, with GNNs primarily applied to prediction and classification tasks (e.g., sea surface temperature forecasting and species behaviour analysis), and RL focused on adaptive decision-making in dynamic and uncertain environments, such as fisheries management and autonomous monitoring systems. Despite their individual strengths, these methods are largely applied in isolation. Key challenges identified across the literature include data sparsity, limited interpretability, weak integration of ecological knowledge, and insufficient real-world validation, particularly for RL.To address these gaps, this review introduces a formal scoring framework to assess theoretical rigour across six dimensions: ecological relevance, theoretical foundations, uncertainty quantification, scalability, stakeholder utility, and interpretability. Furthermore, the study highlights significant geographical disparities in research contributions and emphasises the need for greater inclusion of biodiversity-rich regions in the Global South. Finally, we propose the development of integrated GT–GNN–RL frameworks as a promising direction for future research, enabling the modelling of adaptive behaviours within networked ecological systems and supporting explainable, data-driven decision-making for sustainable marine conservation.
Strong biogeographic structure across the Southern Ocean has led to the recognition of multiple geographically restricted species in many coastal taxa. We examined evolutionary relationships within the Antarctic notothenioid fish genus Harpagifer using mitochondrial (COI, D-loop) and nuclear (ITS2, RHO) markers from seven nominal species distributed across southern South America, the Western Antarctic Peninsula, South Georgia, and sub-Antarctic islands of the South Indian Ocean. Genetic divergence was consistently low, with a maximum mitochondrial p-distance of 1.2
1. Understanding species interactions is central to ecology, yet they remain one of the least documented dimensions of biodiversity (the Eltonian shortfall). Most studies have focused on terrestrial vertebrates, while aquatic vertebrates and invertebrates are still poorly understood. Here, we assessed broad patterns in the published literature on interactions between fishes and macrocrustaceans in freshwater ecosystems, identifying the main interaction types, habitat, and major geographical and taxonomic gaps. 2. We conducted a systematic literature review using the Scopus database, including articles published up to December 2025, and identified 96 eligible studies conducted in freshwater environments. We classified studies according to interaction type, habitat, country and taxonomic group, and quantified research effort through number of publications. 3. The retrieved literature focused primarily on predation, followed by parasitism, competition, and commensalism, and was conducted mainly in streams, lakes and rivers, whereas wetlands were markedly underrepresented. In absolute terms, studies were concentrated in the United States, Brazil, and Canada. When publication counts were standardised by national land area, the highest values were recorded for Trinidad and Tobago, Puerto Rico, and Czechia. Most studies involved native fishes and native macrocrustaceans, although interactions between native fishes and non-native macrocrustaceans formed the second most frequent category. 4. These patterns may reflect historical, methodological, and ecological biases, including the predominance of trophic approaches, the greater practical accessibility (e.g., logistical issues) of certain habitats, and the influence of established model systems. 5. Our results highlight a pronounced Eltonian shortfall in freshwater ecosystems. Expanding research across neglected habitats, interaction types, and taxa, as well as conducting more direct field observation studies, will be essential to improve our understanding of biodiversity interaction dynamics and predictions of ecological responses to global environmental change.
In many animal species, males frequently have alternative reproductive tactics (ART) to maximise their reproductive success. These reproductive strategies or tactics are often characterised by differences in traits such as behaviour, physiology and morphology. However, there is very limited evidence for the occurrence of such tactics in Gobiidae. In this study, we investigated the population of Glossogobius callidus from artificial ponds located in the Lower Sundays River Valley, in the Eastern Cape, South Africa across three seasons (Winter, Spring and Summer). We found that the urogenital papilla can be used to sex G. callidus, without sacrificing the fish. Urogenital papilla of G. callidus was longer and wide in females and shorter in males. In addition, three morphologically distinct male morphs, which represented alternative reproductive tactics were identified (parental, intermediate and sneaker). There was a significant relationship between ART and the different male morphs of G. callidus. These three male morphs were distinguished by body coloration, with parental males displaying dark colouration, while sneaker males exhibited light colouration, and intermediate males showed characteristics between the two extremes. Males exhibiting dark coloured morphs were significantly heavier than those with light coloured morphs. There was a high abundance of dark morphs in Spring (355 individuals) and Summer (202 individuals), which corresponds to the reproductive season. In contrast, the high abundance of light morphs observed during winter (n = 142) suggests that alternative reproductive tactics or traits may be established prior to the breeding season. This study contributed to knowledge on the ART of G. callidus.
Small-scale fisheries in the Western Indian Ocean are vital to food security, livelihoods, and coastal economies, supporting over 65 million people. Yet, SSFs face mounting threats from various factors, including overexploitation, climate change, and weakly integrated governance systems. Despite growing evidence of climate impacts, critical gaps remain in understanding how these changes affect fisheries and in translating this knowledge into effective policy and practice. This policy brief highlights the urgent need to strengthen the science–policy–practice nexus, enhance cross-sector coordination, and embed climate resilience into fisheries governance to secure sustainable and equitable fisheries management outcomes for the region.
