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  1. Article ; Online: Multi-decade catches of manta rays (Mobula alfredi, M. birostris) from South Africa reveal significant decline

    Michelle Carpenter / Denham Parker / Matthew L. Dicken / Charles L. Griffiths

    Frontiers in Marine Science, Vol

    2023  Volume 10

    Abstract: Manta rays (Mobula alfredi and M. birostris) are poorly understood in South Africa, despite their ecological importance and charismatic appeal. This study analyzed a 41-year dataset from the KwaZulu-Natal bather protection program to investigate catch ... ...

    Abstract Manta rays (Mobula alfredi and M. birostris) are poorly understood in South Africa, despite their ecological importance and charismatic appeal. This study analyzed a 41-year dataset from the KwaZulu-Natal bather protection program to investigate catch per unit effort between 1981-2021. We used Generalized Additive Models and the probability of encounter to assess annual and seasonal trends, as well as the effect of location and moon phases on catch rates. We also evaluated the size composition and demographics of caught manta rays using the same dataset. Our analysis revealed a significant decline in overall manta ray catches since the late 1990s (p<0.0001), with increased catch rates during summer, suggesting seasonal visitation to South African waters. We found that manta rays were caught at least once in all 46 netted beaches along the 350 km span of coastline, but with significantly more catches in the Central Area, between Anstey’s beach in the north and Mtwalume in the south. We also observed that moon phase had an effect on manta ray presence, with significantly more catches during spring tides at new and full moon phases. Over half of the caught individuals were juveniles, and a total of 841 individuals (52% of the total catch) belonged to the confirmed juvenile size class (1400-2500 mm disc width). We further found that a greater proportion (70%) of juveniles were caught in the southernmost sampled area, from Hibberdene in the north to Mzamba in the south. These findings highlight the importance of South African waters as a seasonal habitat for manta rays along the southern African coastline. The significant decline and spatial-temporal patterns we observed have critical implications for management and conservation efforts. Our study provides valuable baseline data for future research and underscores the need for continued monitoring and protection of these iconic marine species.
    Keywords mobulidae ; generalized additive models ; fisheries ; Southern Africa ; marine conservation ; probability of encounter ; Science ; Q ; General. Including nature conservation ; geographical distribution ; QH1-199.5
    Subject code 333
    Language English
    Publishing date 2023-03-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Determining the Appropriate Minimum Effort Levels for Use in Fisheries Dynamic Bioeconomic Models

    Sean Pascoe / Roy Aijun Deng / Trevor Hutton / Denham Parker

    Sustainability, Vol 15, Iss 24, p

    2023  Volume 16933

    Abstract: Managing fisheries to achieve ecological, economic and social sustainability is complex. The use of dynamic bioeconomic models can be and have been used to assist in determining management targets. However, optimizing profits over time can result in ... ...

    Abstract Managing fisheries to achieve ecological, economic and social sustainability is complex. The use of dynamic bioeconomic models can be and have been used to assist in determining management targets. However, optimizing profits over time can result in large reductions in fishing effort in the short term with adverse social consequences. There exist other benefits from maintaining fishing effort even in adverse conditions (e.g., maintain crew and fleet capacity). For this reason, many bioeconomic models have included some form of minimum effort, catch or short-term profit constraint. In this paper, we consider a range of approaches to assess an appropriate minimum fishing effort, including the estimation of fishery breakeven effort levels, and approaches based on historical fishing levels. These are tested using a bioeconomic model currently used for fishery management. We find that breakeven approaches tend to result in the most conservative effort levels and the highest net present value of profits. In contrast, using a proportion of the moving average of the observed fishing effort results in less conservative change in effort, while resulting in positive changes in the net present value of fishery profits. The approach also has the advantage of being dynamic, adjusting with recent fishery conditions.
    Keywords multiple objectives ; fishery management ; effort constraints ; bioeconomic modelling ; Environmental effects of industries and plants ; TD194-195 ; Renewable energy sources ; TJ807-830 ; Environmental sciences ; GE1-350
    Subject code 333
    Language English
    Publishing date 2023-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Protected and un-protected urban wetlands have similar aquatic macroinvertebrate communities

    Michelle Blanckenberg / Musa C Mlambo / Denham Parker / Samuel N Motitsoe / Cecile Reed

    PLoS ONE, Vol 15, Iss 5, p e

    A case study from the Cape Flats Sand Fynbos region of southern Africa.

    2020  Volume 0233889

    Abstract: Rapid urbanisation has led to major landscape alterations, affecting aquatic ecosystems' hydrological and biogeochemical cycles, and biodiversity. Thus, habitat alteration is considered a major driver of aquatic biodiversity loss and related aquatic ... ...

    Abstract Rapid urbanisation has led to major landscape alterations, affecting aquatic ecosystems' hydrological and biogeochemical cycles, and biodiversity. Thus, habitat alteration is considered a major driver of aquatic biodiversity loss and related aquatic ecosystem goods and services. This study aimed to investigate and compare aquatic macroinvertebrate richness, diversity and community structure between urban temporary wetlands, located within protected and un-protected areas. The latter were found within an open public space or park with no protection or conservation status, whereas the former were inaccessible to the public and had formal protected, conservation status. We hypothesised that; (1) protected urban wetlands will harbour higher aquatic macroinvertebrate biodiversity (both dry and wet) as compared to un-protected urban wetlands, and (2) that the community composition between the two urban wetlands types will be significantly different. Contrary to our hypothesis, our results revealed no major differences between protected and un-protected urban wetlands, based on the measures investigated (i.e. taxon richness, Shannon-Weiner diversity, Pielou's evenness and community composition) during the dry and wet phase. The only exception was community composition, which revealed significant differences between these urban wetland types. These results suggest that human activities (potential littering and polluting) in the un-protected urban wetlands have not yet resulted in drastic change in macroinvertebrate richness and composition, at least from the dry phase. This suggests a potential for un-protected urban wetlands suffering from minimal human impact to act as important reservoirs of biodiversity and ecosystem services.
    Keywords Medicine ; R ; Science ; Q
    Subject code 710
    Language English
    Publishing date 2020-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: ROV assessment of mesophotic fish and associated habitats across the continental shelf of the Amathole region

    Rio E. Button / Denham Parker / Vivienne Coetzee / Toufiek Samaai / Ryan M. Palmer / Kerry Sink / Sven E. Kerwath

    Scientific Reports, Vol 11, Iss 1, Pp 1-

    2021  Volume 11

    Abstract: Abstract Understanding how fish associate with habitats across marine landscapes is crucial to developing effective marine spatial planning (MSP) in an expanding and diversifying ocean economy. Globally, anthropogenic pressures impact the barely ... ...

    Abstract Abstract Understanding how fish associate with habitats across marine landscapes is crucial to developing effective marine spatial planning (MSP) in an expanding and diversifying ocean economy. Globally, anthropogenic pressures impact the barely understood temperate mesophotic ecosystems and South Africa’s remote Amathole shelf is no exception. The Kei and East London region encompass three coastal marine protected areas (MPAs), two of which were recently extended to the shelf-edge. The strong Agulhas current (exceeding 3 m/s), which runs along the narrow shelf exacerbates sampling challenges. For the first time, a remotely operated vehicle (ROV) surveyed fish and their associated habitats across the shelf. Results indicated fish assemblages differed between the two principle sampling areas, and across the shelf. The number of distinct fish assemblages was higher inshore and on the shelf-edge, relative to the mid-shelf. However, the mid-shelf had the highest species richness. Unique visuals of rare Rhinobatos ocellatus (Speckled guitarfish) and shoaling Polyprion americanus (wreckfish) were collected. Visual evidence of rhodolith beds, deep-water lace corals and critically endangered endemic seabreams were ecologically important observations. The ROV enabled in situ sampling without damaging sensitive habitats or extracting fish. This study provided information that supported the Amathole MPA expansions, which extended protection from the coast to beyond the shelf-edge and will guide their management. The data gathered provides baseline information for future benthopelagic fish and habitat monitoring in these new MPAs.
    Keywords Medicine ; R ; Science ; Q
    Subject code 333
    Language English
    Publishing date 2021-09-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Rhodolith Bed Discovered off the South African Coast

    Luther A. Adams / Gavin W. Maneveldt / Andrew Green / Natasha Karenyi / Denham Parker / Toufiek Samaai / Sven Kerwath

    Diversity, Vol 12, Iss 4, p

    2020  Volume 125

    Abstract: Rhodolith beds have not previously been recorded in South Africa. A multidisciplinary research effort used remote sampling tools to survey the historically unexplored continental shelf off the Eastern Cape coast of South Africa. A rhodolith bed, bearing ... ...

    Abstract Rhodolith beds have not previously been recorded in South Africa. A multidisciplinary research effort used remote sampling tools to survey the historically unexplored continental shelf off the Eastern Cape coast of South Africa. A rhodolith bed, bearing both living and dead non-geniculate coralline red algae, was discovered in the 30–65 m depth range off the Kei River mouth in the newly proclaimed Amathole Offshore Marine Protected Area. Some of the rhodolith forming coralline algal specimens were identified as belonging to at least three genera based on their morphology and anatomy, namely, Lithophyllum , Lithothamnion and a non-descript genus. Rhodolith mean mass and diameter were 44.85 g ± 34.22 g and 41.28 mm ± 10.67 mm (N = 13), respectively. Remotely operated vehicle (ROV) imagery revealed a suite of epibenthic red macroalgae associated with the rhodolith bed. Taxonomy, vertical structure and distribution of rhodoliths in South Africa require further investigation.
    Keywords temperate mesophotic ecosystem ; non-geniculate coralline algae ; ROV ; Biology (General) ; QH301-705.5
    Language English
    Publishing date 2020-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: The WIO Regional Benthic Imagery Workshop

    Tanya Haupt / Jamie Ceasar / Paris Stefanoudis / Charles von der Meden / Robyn Payne / Luther Adams / Darrell Anders / Anthony Bernard / Willem Coetzer / Wayne Florence / Liesl Janson / Ashley Johnson / Roxanne Juby / Alison Kock / Daniel Langenkämper / Ahmed Nadjim / Denham Parker / Toufiek Samaai / Laurenne Snyders /
    Leshia Upfold / Grant van der Heever / Lauren Williams

    Research Ideas and Outcomes, Vol 8, Iss , Pp 1-

    Lessons from past IIOE-2 expeditions

    2022  Volume 14

    Abstract: Originating from the Second International Indian Ocean Expedition (IIOE-2), the main goal of the Western Indian Ocean (WIO) Regional Benthic Imagery Workshop, was to provide information and training on the use of various underwater imagery platforms in ... ...

    Abstract Originating from the Second International Indian Ocean Expedition (IIOE-2), the main goal of the Western Indian Ocean (WIO) Regional Benthic Imagery Workshop, was to provide information and training on the use of various underwater imagery platforms in benthic research. To date, attempts made to explore the bottom of the ocean range from simple diving bells to more advanced camera systems, and the rapidly expanding field of underwater image-based research has supported marine exploration in many forms, from biodiversity surveys, spatial analyses and temporal studies, to monitoring schemes. Alongside the increasing use of underwater camera systems worldwide, there is an evident need to improve training and access to these techniques for students and researchers from institutes within the WIO. The week-long virtual event was conducted between 30 August and 3 September 2021 with 266 participants. Sessions consisted of lessons, practical demonstrations and interactive discussions which covered the steps required to conduct underwater imagery surveys, taking participants through elements of sampling design, data acquisition and processing, considerations for statistical analysis and, effective managment of data. The session recordings from the workshop are available online as a teaching aid which has the potential to reach marine researchers both regionally and globally. It is crucial that we build on this momentum by continuing to develop and strengthen the network established through this initiative for standardised benthic-image-based research within the WIO.
    Keywords Western Indian Ocean ; IIOE-2 ; Regional training wo ; Science ; Q
    Subject code 333
    Language English
    Publishing date 2022-03-01T00:00:00Z
    Publisher Pensoft Publishers
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: New possibilities for research on reef fish across the continental shelf of South Africa

    Anthony T.F. Bernard / Albrecht Götz / Denham Parker / Elodie R. Heyns / Sarah J. Halse / Nicholas A. Riddin / Martin K.S. Smith / Angus W. Paterson / Henning Winker / Laura Fullwood / Timothy J. Langlois / Euan S. Harvey

    South African Journal of Science, Vol 110, Iss 9/10, Pp 5-

    2014  Volume 5

    Keywords subtidal reef fish ; standardised monitoring ; stereo-BRUVs ; underwater video techniques ; Science ; Q ; Science (General) ; Q1-390 ; Social Sciences ; H ; Social sciences (General) ; H1-99
    Language English
    Publishing date 2014-09-01T00:00:00Z
    Publisher Academy of Science of South Africa
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article: Invasion of a South African Anguilla mossambica (Anguillidae) population by the alien gill worm Pseudodactylogyrus anguillae (Monogenea)

    Denham Parker

    Abstract: ... The parasitic gill monogenean ... Pseudodactylogyrus anguillae ... is alien to Africa. In an investigation of 227 longfin eel ... Anguilla mossambica ... and 26 mottled eel ... Anguilla marmorata ... sampled from four river systems in the Eastern ... ...

    Abstract

    The parasitic gill monogenean <em>Pseudodactylogyrus anguillae</em> is alien to Africa. In an investigation of 227 longfin eel <em>Anguilla mossambica</em> and 26 mottled eel <em>Anguilla marmorata</em> sampled from four river systems in the Eastern Cape, South Africa, this parasite was only present on the gills of <em>A. mossambica</em> sampled from the Great Fish River system. In the Great Fish River, it infected 73.2% of the sampled population at a mean intensity of 63.8 ± 34.3 parasites per fish.  High prevalence and intensity are indicative of a well established alien invasive parasitic species. Results showing the absence of <em>P. anguillae</em> from the co-occurring but less abundant <em>A. marmorata</em> indicate that this species may be less susceptible to <em>P. anguillae</em> infection.
    Language English
    Document type Article
    Database AGRIS - International Information System for the Agricultural Sciences and Technology

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