Southern Coast Of Africa Research Articles

Rediscovering the unusual Cancellus makrothrix Stebbing, 1924 (Crustacea: Decapoda: Diogenidae) in the “Great African Seaforest”

The rare diogenid hermit crab Cancellus makrothrix Stebbing, 1924, previously known from only a few specimens collected a century ago from Algoa Bay, South Africa, has been found to be common in the kelp forest known as the “Great African Seaforest”, and rocky reefs, of False Bay, South Africa. This poorly known species, considered “aberrant” by some carcinologists, is one of 17 known in the genus Cancellus H. Milne Edwards, 1836, and the only of the genus known to occur in the coast of southern Africa. Cancelllus makrothrix lives in gastropod shells, whereas all other congenerics live in a variety of petricolous dwellings that are either excavated or worn away into cylindrical cavities. The newly collected material of C. makrothrix in South Africa, together with the study of historical museum specimens has made possible the detailed redescription and taxonomic discussion of this species presented herein, using full illustrations, photographs, and microCT scans. For future reference, the molecular CO1 genetic barcode is reported. A lectotype is selected from Stebbing’s original syntype material found to consist of two specimens: a female of which only several appendages remain, in the Natural History Museum, London, and a male, illustrated in the original description, in the Iziko South African Museum, Cape Town. Taxonomic remarks, comments on biological oddities, brief in situ and laboratory observations of live specimens, and a map summarizing the world distribution of species of Cancellus, are included.

Cryptic diversity in southern African kelp

The southern coast of Africa is one of the few places in the world where water temperatures are predicted to cool in the future. This endemism-rich coastline is home to two sister species of kelps of the genus Ecklonia maxima and Ecklonia radiata, each associated with specific thermal niches, and occuring primarily on opposite sides of the southern tip of Africa. Historical distribution records indicate that E. maxima has recently shifted its distribution ~ 70 km eastward, to sites where only E. radiata was previously reported. The contact of sister species with contrasting thermal affinities and the occurrence of mixed morphologies raised the hypothesis that hybridization might be occurring in this contact zone. Here we describe the genetic structure of the genus Ecklonia along the southern coast of Africa and investigate potential hybridization and cryptic diversity using a combination of nuclear microsatellites and mitochondrial markers. We found that both species have geographically discrete genetic clusters, consistent with expected phylogeographic breaks along this coastline. In addition, depth-isolated populations were found to harbor unique genetic diversity, including a third Ecklonia lineage. Mito-nuclear discordance and high genetic divergence in the contact zones suggest multiple hybridization events between Ecklonia species. Discordance between morphological and molecular identification suggests the potential influence of abiotic factors leading to convergent phenotypes in the contact zones. Our results highlight an example of cryptic diversity and hybridization driven by contact between two closely related keystone species with contrasting thermal affinities.

Reports of Pennellidae Burmeister, 1835 (Copepoda: Siphonostomatoida) post metamorphosed females off the coast of southern Africa

Seven species belonging to Pennellidae are reported from marine teleosts caught off southern Africa. Additionally, complete re-descriptions are provided for Propeniculus stromatei and Sarcotretes scopeli. Examination of Lernaeenicus gonostomae, deposited in the Iziko South African Museum, indicated that it has the morphological features of Sarcotretes rather than Lernaeenicus and thus should be moved to Sarcotretes i.e. S. gonostomaen. comb. for which a re-description is also provided. Reports of new host records include those of Pennella instructa from Seriola lalandi; Propeniculus stromatei from Rhabdosargus holubi and Pomadasys commersonnii; Sarcotretes scopeli from Nansenia tenera, and Sarcotretes longirostris from Centrolophus niger. New geographical records include those of P. instructa, P. stromatei, S. scopeli, S. longirostris, and L. longiventris off southern Africa. Additionally, an attempt to estimate the evolutionary relationships amongst some genera is done from partial COI sequences deposited in Genbank.

Mesozooplankton community responses to a large-scale harmful algal bloom induced by the non-indigenous dinoflagellate Lingulodinium polyedra

Our understanding of how zooplankton community composition varies in relation to harmful algal blooms remains limited, particularly in ecosystems where toxin-producing algae may have been introduced through anthropogenic activities. Harmful algal blooms (HABs) naturally occur on the coast of southern Africa, where they are predominantly associated with the cold Benguela region. In the warm-temperate waters east of Cape Agulhas, HABs occur rarely and red tides are mostly associated with the non-toxin producing dinoflagellate Noctiluca scintillans. Blooms of N. scintillans may cause water discolouration, but this is generally short-lived with limited impact on the ecosystem. However, in December 2013 the eastern Agulhas region experienced an extensive HAB, which persisted for ca. 4 months and affected >500 km of coastline, from Wilderness to East London. This unprecedented event was caused by the non-indigenous toxin-producing dinoflagellate, Lingulodinium polyedra. The impact on the coastal seas was widespread and severe, with instances of low dissolved O2 levels and fish kills being reported at the time in the broader Algoa Bay area. This study investigated the impact of the L. polyedra bloom on the mesozooplankton of Algoa Bay and reports the successive changes in zooplankton community composition and biomass observed from July 2013 to July 2014. The bloom impacted species diversity and richness, with a marked shift in dominance from a calanoid copepod dominated community to one dominated by microzooplankton (specifically cyclopoid copepods, tintinnids and cladocerans), over the period November 2013–March 2014. Calanoid copepod abundance was significantly reduced throughout Algoa Bay with the progression of the bloom, and this significantly impacted the total zooplankton biomass of the region. The results of the study suggest that harmful algal blooms have a negative impact on zooplankton communities, with notable implications for the higher trophic levels of the coastal pelagic ecosystem.

Invasion of rocky shores by a mytilid mussel reveals an abundant‐centre distribution coupled with moderate increases in densities at its absolute range limits

AbstractSemimytilus patagonicus is an invasive mussel on the coast of southern Africa and has extended its range in recent years. We asked whether its distribution and abundance are consistent with the abundant‐centre hypothesis (ACH). Marginal populations were located by monitoring 33 rocky shore sites in South Africa and southern Namibia in 2021. This revealed no changes to its distributional limits since 2020. At nine of these sites, population demography was measured to allow a comparison of their densities and size structure. Four were central populations on the west coast of South Africa (including the site where the species was first detected in 2009). Four were marginal populations in South Africa: two towards the cold range edge in the north and two towards the warm range edge to the south. The ninth population was in southern Namibia, representing a recent invasion event first detected in 2014. Across the species' South African range, the distribution of its abundance was generally consistent with the ACH, with the greatest abundance at its range centre and a gradual decrease towards the range edges. However, the ultimate marginal population at both its cold and warm range edges showed moderate upticks in abundance compared to the penultimate marginal populations. Additionally, marginal populations in South Africa typically included a greater proportion of large individuals. Recruitment intensity was greater in warm range edge populations than cold range edge populations. The size structure of the population in Namibia resembled those of central populations in South Africa. Moderate increases in densities at the absolute range limits suggest that the species is currently undergoing spread into regions associated with moderately optimal environmental conditions (ultimate range edge sites) after encountering regions associated with suboptimal environmental conditions (penultimate range edge sites).

Distinctive zonation of planktonic ostracods assemblages in the dynamic Southeastern Atlantic

Species diversity, abundance and spatial distribution of planktonic Ostracoda in the frontal waters of the South Atlantic were studied in summer 2009. Mesozooplankton materials were collected using WP-2 net in the top 300 m layer, from 32 stations located along the profile designated from the southern coast of Africa towards the Antarctic. Twenty-one species of ostracods were recorded. Ostracoda species diversity generally decreased with increasing latitude. Their total abundance showed a parabolic pattern of distribution, with lower numbers at the edges of the transect and higher numbers in the middle. We identified three distinctive areas occupied by different assemblages of Ostracoda. The first area, the Benguela Current (BENG), was inhabited mainly by subtropical ostracods. The second area - Southern Subtropical Convergence, Subantarctic Front, Subantarctic Zone and Polar Front (SSTC, SAF, SANT and PF) - was characterized by the presence of a mixture of subtropical, subantarctic, and Antarctic species. The third area, the Antarctic Zone (ANTA), was inhabited mostly by subantarctic and Antarctic ostracods. Moreover, we confirmed that the SSTC was an almost impassable hydrographical barrier for subtropical-tropical Ostracoda species. This study demonstrated the distribution of some species extending further north (e.g., Metaconchoecia australis) than previously recorded. Morphometric analysis of the most common ostracod species, Discoconchoecia elegans, showed an increasing trend in its mean individual size from the BENG zone to the ANTA zone.

Movement behaviour of catface rockcod Mycteroperca (Epinephelus) andersoni (Epinephelidae) off the eastern seaboard of southern Africa

Movement behaviour of the endemic epinephelid Mycteroperca andersoni (formerly allocated to genus Epinephelus) along the east coast of southern Africa was investigated using both conventional dart tagging and passive acoustic telemetry. Results from both methods showed that this species is likely to be a temporary resident on shallow inshore reefs; fish showed high site fidelity and occupied relatively small home ranges for periods seldom exceeding 12 months, whereafter they appeared to undertake ranging-type movements. Adults >400 mm total length were more mobile than juveniles, and the distance moved increased with both fish size and time at liberty. Adults south of Durban, South Africa, moved farther in a northerly direction than those north of Durban, confirming that spawning likely takes place north of Durban. No direct evidence of a spawning migration was found, but anecdotal reports that they form spawning aggregations suggests that migrations for this purpose are likely to occur. The current species-specific linefish regulations and the recently expanded marine protected area network along the east coast of South Africa are believed to be adequate to ensure the future sustainable use of this species. However, improved enforcement of regulations is required, and identification of spawning aggregation sites should be a research priority.

Levels of Elements in Typical Mussels from the Southern Coast of Africa (Namibia, South Africa, Mozambique): Safety Aspect

The soft tissues of mussels are often used as the main food source, especially in coastal areas. Neutron Activation Analysis was used to measure the content of 24 macro- and microelements in the soft tissues and 18 elements in the shells of selected sets of mussels of the species Mytilus galloprovincialis. The mussels were collected in 8 polluted and 4 pristine zones, which included Namibia, the west and east coasts of South Africa, and Mozambique. According to factor analysis Co, Ni, Zn, As, Se, Br, I, Sb could have anthropogenic origin. The concentrations of elements such as Cr, As, Se and partly Zn at polluted stations were above the maximum permissible levels for seafood. The concentrations of Sc, V, Cr, Mn, Co, Ni, Sb, Cs, Th, U in shells and soft tissues of the same mussels were at the close levels. Elements such as Al, Cr, Co, As (partly Zn, Se, and I) are considered to be harmful to human health at the levels of mussels consumption of 200 g/week per person and lower in such zones as Swakopmund, East London, Port Shepstone, Richards Bay, Xai-Xai according to calculated risk quotients and target hazard indices.

Maputo Special Reserve and dung beetle conservation in the heterogeneous landscape of the Maputaland Centre of Endemism

Background: Maputo Special Reserve (MSR) in Mozambique lays within the Maputaland Centre of Endemism (MCE) and protects the biota of a habitat mosaic dominated by coastal dune forest and inland sand forest patches of different sizes surrounded by natural grassland. Objectives: To determine the importance of woody versus grassland vegetation for supporting endemic east coast versus widespread savanna dung beetles in the MCE in the face of increased accessibility and exploitation of woody vegetation in southern Mozambique, especially by charcoal burners.Method: We used general linear mixed models, additive partitioning of diversity and ordination to analyse species abundance and occurrence across a mosaic of three major habitats in the MSR (grassland, sand and dune forest).Results: High compositional heterogeneity was found between habitat types and study sites so that beta diversity was mostly higher than alpha diversity. Three distinct scarabaeine dung beetle assemblages defined from ordination were largely centred on the three habitat types. Out of a total of 61 species, greater numbers were associated with grassland (38) than sand (17) and dune forest (6) although abundance was greater in both dune forest and grassland than in sand forest. Biogeographical classification indicated that >40% of the species are endemic to the east coast of southern Africa with the remainder centred in adjacent savanna. Endemic east coast species were well represented in both forest (15) and grassland (11). Savanna species were better represented in grassland (27) than forest (8). Proportions of grassland species and their abundance declined across increasing patch sizes of sand forest becoming lowest in dune forest.Conclusions: Conservation of endemic, east coast dung beetle species requires the preservation of both natural grassland and sizeable patches of forest in an undisturbed habitat mosaic. As the east coastal system is relatively small in extent with the MCE widely transformed in South Africa, the MSR is an important contributor to regional conservation of endemic species.

THE CONTRIBUTION OF THE DEFENCE ACT TO THE FIGHT AGAINST PIRACY

The recent events off the Horn of Africa have drawn attention again to the problem of piracy. Less publicized is an increase in pirate activities in West Africa. Despite centuries of repression, this criminal behaviour continues to present a serious challenge to the safety of shipping on which international trade depends. And the phenomenon is spreading worryingly close to a South African coast which witnessed it in the past. Indeed, pirates operated off the coast of Southern Africa as early as 1508, with pirate activity peaking at the end of the 17th century. Piracy may be generally defined as “unlawful depredation at sea involving the use or threat of violence possibly, but not necessarily, involving robbery”. The purpose of this paper is to examine the contribution of the Defence Act 42 of 2002 (hereinafter “the Act”) to the fight against piracy. South Africa has a duty to co-operate to the fullest possible extent in the repression of piracy on the high seas in terms of the 1982 UN Convention on the Law of the Sea (hereinafter “LOSC”) (art 100. South Africa ratified LOSC in 1997 after it had come into effect in 1994). In order to do so, South Africa is expected to exercise its legislative, executive and judicial jurisdictions.

Flatfoot in Africa, the cirripede Chthamalus in the west Indian Ocean.

Barnacles of the genus Chthamalus are commonly encountered rocky intertidal shores. The phylogeography of the different species in the Western Indian Ocean is unclear. Using morphological characteristics as well as the molecular markers mitochondrial cytochrome oxygenase subunit I (COI) and the nuclear sodium-potassium ATPase (NaKA), we identified four clades representing four species in the Western Indian Ocean and its adjacent seas. Among these species, a newly identified species, Chthamalus barilani, which was found in Madagascar, Zanzibar and Tanzania. Chthamalus from the coasts of Tanzania and Zanzibar is identified morphologically as C. malayensis, and clusters with C. malayensis from the Western Pacific and the Indo Malayan regions. C. malayensis is regarded as a group of four genetically differentiated clades representing four cryptic species. The newly identified African clade is genetically different from these clades and the pairwise distances between them justify the conclusion that it is an additional cryptic species of C. malayensis. This type of genetic analyses offers an advantage over morphological characterization and allowed us to reveal that another species, C. barnesi, which is known from the Red Sea, is also distributed in the Arabian Sea and the Persian Gulf. We could also confirm the presence of the South African species C. dentatus in the Mozambique channel. This represents the Northeastern limit of C. dentatus, which is usually distributed along the coast of southern Africa up to the Islands of Cape Verde in West Africa. Altogether, based on a combination of morphology and genetics, we distinct between four clusters of Chthamalus, and designate their distribution in the West Indian Ocean. These distinctions do not agree with the traditional four groups reported previously based merely on morphological data. Furthermore, these findings underline the importance of a combining morphological and genetics tools for constructing barnacle taxonomy.

Kunstmann III: The Oldest Known Nautical Chart Incorporating Latitudes

Among the few Portuguese charts surviving from the turn of the sixteenth century, the now lost Kunstmann III chart is the most enigmatic. Not only is it undated and unsigned but also its cartographical style differs greatly from the best-known contemporary Portuguese charts, namely those by Jorge de Aguiar and Pedro Reinel, as well as the Cantino planisphere. Although Kunstmann III has been studied by various twentieth-century authors, none has addressed in depth its distinctive features: the presence of four different handwritings, the depiction of a latitude scale for the Northern Hemisphere only, and the geometry of the African coastline. Contradicting the usually accepted dating of ‘after 1506’, we argue that the Kunstmann III chart was most probably started around 1500 and remained a living document for some years thereafter, with new places-names added by other individuals at later times. We further show, based on the assessment of its geometry and a comparison with other charts, that Kunstmann III is the oldest known chart incorporating observed latitudes of places and containing a primitive non-astronomical depiction of the southwestern and southern coasts of Africa, based on the first voyage of Vasco da Gama to India in 1497. This makes Kunstmann III a hitherto unrecognized link in the transitional period between two different cartographical models.

Biogeographic drivers of distribution and abundance in an alien ecosystem engineer: Transboundary range expansion, barriers to spread, and spatial structure

AbstractAimBiogeographic boundaries can act as either weak or strong barriers to the spread of species undergoing distributional change. Once a novel species spreads across a boundary, it can have a substantial impact on the ecosystem, for instance by competing with local species, and, over the long‐term, re‐engineer the ecosystem. Marine biogeographic regions are clearly defined on the coast of southern Africa and we tested the influence of their boundaries on the spread and spatial structure of an alien ecosystem engineer.LocationSouthern Africa.TaxonAn invasive mussel, Mytilus galloprovincialis.MethodsRecords of M. galloprovincialis were compiled into a database to determine its decadal patterns of spread across multiple bioregions. Distribution and abundance (estimated using density and semi‐quantitative abundance scale [ACFOR]) of this mussel were surveyed to determine patterns in spatial structure across bioregions. In addition, we compared the size structure of populations at the eastern margins of its range with those of larger populations nearer the range centre.ResultsInitial breaching of biogeographic boundaries was associated with rapid spread, but other boundaries encountered decades later acted as barriers to further spread. Across >2,800 km of coast, spatial autocorrelation was observed in densities (low and mid shore levels) and in ACFOR abundances. Repeating spatial patterns in densities and ACFOR abundance were detected at scales of 120–160 km and of 400–990 km. Considerable effort was required to detect populations at the absolute eastern limits of its distribution.Main conclusionDetection of spatial structures at multiple scales suggests that ecologically determined processes regulate abundance at both intra‐bioregional and inter‐bioregional scales, which may help tease apart the historic and contemporary consequences of interspecific interactions on the structure of rocky shore communities. This study demonstrates the influence of biogeography in driving temporal patterns of spread and spatial structure on the distribution and abundance of an invasive species.

Contemporary climate change hinders hybrid performance of ecologically dominant marine invertebrates.

Human activities alter patterns of biodiversity, particularly through species extinctions and range shifts. Two of these activities are human mediated transfer of species and contemporary climate change, and both allow previously isolated genotypes to come into contact and hybridize, potentially altering speciation rates. Hybrids have been shown to survive environmental conditions not tolerated by either parent, suggesting that, under some circumstances, hybrids may be able to expand their ranges and perform well under rapidly changing conditions. However, studies assessing how hybridization influences contemporary range shifts are scarce. We performed crosses on Pyura herdmani and Pyura stolonifera (Chordata, Tunicata), two closely related marine invertebrate species that are ecologically dominant and can hybridize. These sister species live in sympatry along the coasts of southern Africa, but one has a disjunct distribution that includes northern hemisphere sites. We experimentally assessed the performance of hybrid and parental crosses using different temperature regimes, including temperatures predicted under future climate change scenarios. We found that hybrids showed lower performance than parental crosses at the experimental temperatures, suggesting that hybrids are unlikely to expand their ranges to new environments. In turn, we found that the more widespread species performed better at a wide array of temperatures, indicating that this parental species may cope better with future conditions. This study illustrates how offspring fitness may provide key insights to predict range expansions and how contemporary climate change may mediate both the ability of hybrids to expand their ranges and the occurrence of speciation as a result of hybridization.

Seashell and debris ingestion by African penguins

ABSTRACTAfrican penguins (Spheniscus demersus) are pursuit-diving seabirds endemic to the coast of southern Africa. In this study, we investigate the presence of seashells and anthropogenic debris (e.g. plastic, glass, nylon) in the stomach contents of adult African penguins, as determined from sampling of live penguins through the water off-loading technique (n = 4,793) and from post-mortem examination of penguin carcases (n = 159). Seashells were present in stomach contents sampled from 106 live (2.2%) and three dead (1.9%) penguins. Seashells originated from a variety of intertidal and subtidal organisms including molluscs, barnacles and bryozoans, and the eroded condition of the shell fragments suggests that they were picked up from shell deposits on the beach or in the surf zone. Seashell ingestion appears to be more frequent in the months of peak egg laying. A subset of stomach samples from known-sex individuals revealed that seashells were only present in the stomachs of adult females. In post-mortem examination, the presence of seashells in the stomach was accompanied by anatomical evidence that egg laying was imminent or had recently occurred. Anthropogenic debris was found in one (0.6%) and eight (0.2%) stomach content samples obtained from dead and live penguins, respectively. In some cases, the ingestion of anthropogenic debris co-occurred with that of seashells, and their size and shape were similar. Our findings demonstrate that adult female African penguins occasionally ingest seashells, possibly as a calcium supplementation strategy, and raise concern that in doing so they may also accidentally ingest anthropogenic debris.

Spatial variation in meristic and morphometric characteristics of sardine Sardinops sagax around the coast of southern Africa

Spatial variability in phenotypic characteristics within a fish population may be used to infer the existence of multiple stocks, and knowledge of the population structure of exploited species is important for their sustainable management. In this study we investigated geographic variability in meristic (vertebral count) and morphometric (body shape) characteristics of sardine Sardinops sagax from three southern African regions: Namibia, the South African west coast, and the South African south coast. There were significant regional differences in vertebral counts, with Namibian fish tending to have more vertebrae than South African fish, but with no difference between sardine off the South African west and south coasts. Body shape was characterised using morphometric landmarks, and shape changes were investigated using geometric morphometrics, with influences on fish shape assessed using multivariate regressions. To remove the effects of allometry, the 22 shape variables (represented by Procrustes coordinates) were regressed against fish size (represented by centroid size). There was a significant allometric effect, which was removed by using the residuals of these regressions in further analyses. A multivariate multiple regression was applied to the 22 size-corrected shape variables and to three covariates: condition factor, stomach fullness and fat stage. The significant influence of these covariates was removed by using the residuals from this regression in a canonical variate analysis, where corrected shape variables were classified in relation to region, year and sex. The Mahalanobis distances from the canonical variate analysis differed significantly for most combinations of classifier variables, with clear separations among the three regions. Sardinops sagax off Namibia had thicker bodies and more contracted tail regions than South African fish, whereas S. sagax off the South African south coast had thinner bodies and smaller heads than those off the west coast. These results support the hypothesis of multiple sardine stocks around southern Africa.

Age and growth of narrow-barred Spanish mackerel Scomberomorus commerson in the coastal waters of southern Mozambique and KwaZulu-Natal, South Africa

The narrow-barred Spanish mackerel Scomberomorus commerson is one of the most important linefish species caught in KwaZulu-Natal and southern Mozambique waters, forming the basis of important commercial, artisanal and recreational fisheries. A total of 439 S. commerson were sampled along the east coast of southern Africa (KwaZulu-Natal, South Africa, and southern Mozambique) between April 2011 and March 2012. Retrospective length-at-age data observed from whole otoliths were used to compare and describe sex-specific growth. Growth rates obtained from otolith-derived data were compared with those estimated from 29 tag-recaptured fish. Overall, ages ranged from 0.48 to 14.6 years for females and 0.4 to 13.57 years for males. Otolith readings yielded an average percent error of 11.21%, lower than recorded in a previous study from the region. Marginal zone analysis provided strong evidence that one translucent and one opaque growth zone were laid down annually. Schnute growth-function parameters indicated significant differences in growth between sexes. Females approached their mean asymptotic length at a faster rate, and grew to a greater mean length-at-age, relative to males. Growth in both sexes was rapid, achieving 67.46 cm FL (females) and 65.4 cm FL (males) in their first year of life. Growth rates obtained from tag-recaptured S. commerson indicated slower growth for smaller/younger fish up until 70 cm FL after which growth was very similar to that observed from otolith-derived data. The results of this study provide accurate, validated life-history parameters for king mackerel that are important for the assessment of stock status in the region.

Seasonal variation in remotely-sensed phytoplankton size structure around southern Africa

The three-component model of Brewin et al. (2010) computes fractional contributions of three phytoplankton size classes (micro- (>20μm), nano- (2–20μm), picophytoplankton (<2μm)) to the overall chlorophyll a concentration (Chla). Using in situ pigment data, model coefficients were adjusted for application to the southern African marine region. The refined model was applied to seasonal and monthly climatologies of MODIS Aqua Chla around Southern Africa. Chla >1mgm−3 was limited to shelf regions along the coasts of Southern Africa and Madagascar, while values <0.1mg−3 were found over most of the open ocean between the equator and 38°S during austral summer and autumn. In winter and spring, low values (< 0.1mgm−3) were restricted to smaller regions within subtropical gyres, while values up to 0.7mgm−3 extended over a much greater area of the open ocean. Shelf regions in the northern (NB) and southern Benguela (SB), Agulhas Bank (AB), Agulhas region (AR), and Mozambique Channel (MC) all showed similar seasonal cycles of size structure. On average, microphytoplankton comprised >50% of the total Chla in these regions with little change throughout the year. The AR shelf differed, with picophytoplankton dominating in summer, and micro- and nanophytoplankton the rest of the year. In the open ocean domains of the NB, SB, and AB regions, nanophytoplankton dominated for most of the year, with picophytoplankton being more prevalent during summer and autumn. In contrast, in the AR open ocean, nanophytoplankton were dominant only during winter and early spring, whereas picophytoplankton dominated throughout the year in the MC open ocean. The refined model characterised previously unknown spatial and temporal changes in size structure in various ecosystems around Southern Africa.

The first authenticated record of Pygmy Killer Whale (Feresa attenuata Gray 1874) in Mozambique; has it been previously overlooked?

BackgroundThe cetacean fauna of the poorly-studied waters off eastern Africa is still being described. Information on the cetacean species occurring in specific range states is important for understanding their geographical distribution ranges and for implementing national and international conservation and management measures. This report presents the first authenticated record of the Pygmy killer whale in Mozambican waters and the first record on the eastern coast of southern Africa since 1970.MethodsAs a part of regular informal surveys for birds and other marine life from Maputo, Mozambique, three Pygmy killer whales were seen, approached and photographed north of Inhaca Island (25°52′54.22″S 33° 8′33.62″E), on 23 April 2017.ResultsThe animals were seen interacting on the surface for 35 min, travelling at ca. 1 km/h along the shelf edge in water 235 m deep. All three animals had been overlooked by the authors earlier in the day, misidentified as Spinner dolphins (Stenella longirostris).ConclusionThis is the first authenticated record of Pygmy killer whale in Mozambican waters and the first recent record on the eastern coast of southern Africa since 1970, emphasising the lack of knowledge of offshore marine biodiversity in Mozambique. Previous reported records of the species in Mozambique lie outside Mozambique Exclusive Economic Zones or lack evidence. The species should be included in relevant conservation planning.Available identification material focusses on the separation of this species from Melon-headed whale (Peponocephala electra) and fails to note the great similarities of this species with smaller dolphins. At-sea observers are encouraged to consider this species when identifying ‘dolphins’. Pygmy killer whales are easily overlooked.

Open-ocean foraging ecology of southern bluefin tuna Thunnus maccoyii based on stomach contents

We investigated the foraging ecology of southern bluefin tuna Thunnus maccoyii in open-ocean habitats of temperate waters in the southern hemisphere by analyzing their stomach contents. Samples were collected from longline vessels over 15 yr (n = 4649). Of the prey, 51% by weight were cephalopods and 46% were teleosts. These values differ from those in the literature for other top predators in the open oceans, for which teleosts compose the largest portion of prey. The dominance of cephalopods also differs from the pattern for juveniles in previous studies in their coastal habitat, where most of the prey are teleosts. Thus, a distinct shift of prey occurs along with the habitat shift due to ontogenetic development. By weight, important prey were omma - strephid (18%), lycoteuthid (12%), and argonautid (1%) cephalopods and nomeid (8%, mainly Cubiceps caeruleus), paralepidid (7%), bramid (6%), and alepisaurid (6%) teleosts. The prey composition was relatively consistent among tuna sizes, sea surface temperatures, and years; changes in prey composition were due largely to differences in the cephalopod prey. Cephalopods belonging to the families Lycoteuthidae and Argonautidae contributed to the prey only off the southern coast of Africa and near Tasmania, respectively. Lycoteuthids occurred at lower sea sur- face temperatures than ommastrephids off the southern coast of Africa. Small ommastrephids were dominant in smaller tuna in the southeastern Indian Ocean. Our data provide basic informa- tion that will improve our understanding of the oceanic food webs in southern temperate waters.