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Elston C, Murray TS, Rogers T, Parkinson MC, Mann BQ, Daly R, Filmalter JD, Cowley PD. Diamond Gymnura natalensis and duckbill Aetomylaeus bovinus rays undertake nationwide coastal migrations. J Fish Biol 2024. [PMID: 38533638 DOI: 10.1111/jfb.15728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 02/22/2024] [Accepted: 02/28/2024] [Indexed: 03/28/2024]
Abstract
Migration is a critical aspect of ocean ecosystems, and understanding this phenomenon answers ecological and management questions. Given the difficulty in tracking ocean animals across large distances, the extent to which different ray species perform long-distance movements, such as migrations, remains unknown. This study used passive acoustic telemetry to track the movements of endemic diamond Gymnura natalensis and critically endangered duckbill Aetomylaeus bovinus rays along the South African coastline using a collaborative nationwide network of coastal acoustic receivers for up to 7 years. Duckbill rays were detected significantly more frequently than diamond rays, but both species moved between the south and east coasts of South Africa (traveling up to 1167 km). Tagged individuals were detected significantly more often in their tagging locations during summer months but traveled significantly further distances during winter months. Furthermore, movement models fitted to individual duckbill rays' annual net-squared displacement identified most individual annual movements as migratory. This evidence suggests that both diamond and duckbill rays make eastward winter migrations and return to specific areas along the coastline during the summer months. The exceptions to this were diamond rays tagged on the east coast that were not found to migrate seasonally, which supports previous research that there is intraspecific variability in migrations for ray species. These findings have implications for understanding ray migration not only on a global scale but also locally for spatial management interventions and population delineation.
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Affiliation(s)
- Chantel Elston
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
| | - Taryn S Murray
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
| | - Toby Rogers
- Institute for Communities and Wildlife in Africa (iCWild), University of Cape Town, Cape Town, South Africa
- Shark Spotters, Cape Town, South Africa
| | | | - Bruce Q Mann
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
- Oceanographic Research Institute, Durban, South Africa
| | - Ryan Daly
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
- Oceanographic Research Institute, Durban, South Africa
| | - John D Filmalter
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
| | - Paul D Cowley
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
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Mann BQ, Dalton WN, Jordaan GL, Daly R. Movement patterns and growth rate of Scotsman Polysteganus praeorbitalis (Sparidae) tagged in the Pondoland Marine Protected Area, Eastern Cape, South Africa. African Zoology 2023. [DOI: 10.1080/15627020.2023.2170717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Affiliation(s)
- BQ Mann
- Oceanographic Research Institute, Durban, South Africa
| | - WN Dalton
- Oceanographic Research Institute, Durban, South Africa
| | - GL Jordaan
- Oceanographic Research Institute, Durban, South Africa
| | - R Daly
- Oceanographic Research Institute, Durban, South Africa
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Foster RM, Childs AR, Mann BQ, Potts WM. Age and growth of the Cape knifejaw Oplegnathus conwayi, an endemic South African teleost. African Zoology 2022. [DOI: 10.1080/15627020.2022.2035254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- RM Foster
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda (formerly Grahamstown), South Africa
| | - A-R Childs
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda (formerly Grahamstown), South Africa
| | - BQ Mann
- Oceanographic Research Institute, South African Association for Marine Biological Research, Durban, South Africa
| | - WM Potts
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda (formerly Grahamstown), South Africa
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Winkler AC, Butler EC, Attwood CG, Mann BQ, Potts WM. The emergence of marine recreational drone fishing: Regional trends and emerging concerns. Ambio 2022; 51:638-651. [PMID: 34145559 PMCID: PMC8800965 DOI: 10.1007/s13280-021-01578-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 02/28/2021] [Accepted: 05/16/2021] [Indexed: 06/12/2023]
Abstract
Online evidence suggests that there has been an increase in interest of using unmanned aerial vehicles or drones during land-based marine recreational fishing. In the absence of reliable monitoring programs, this study used unconventional publicly available online monitoring methodologies to estimate the growing interest, global extent, catch composition and governance of this practice. Results indicated a 357% spike in interest during 2016 primarily in New Zealand, South Africa and Australia. From an ecological perspective, many species targeted by drone fishers are vulnerable to overexploitation, while released fishes may experience heightened stress and mortality. From a social perspective, the ethics of drone fishing are being increasingly questioned by many recreational anglers and we forecast the potential for increased conflict with other beach users. In terms of governance, no resource use legislation specifically directed at recreational drone fishing was found. These findings suggest that drone fishing warrants prioritised research and management consideration.
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Affiliation(s)
- Alexander C. Winkler
- Centro de Ciências do Mar (CCMAR), University of the Algarve, Faro, Portugal
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
| | - Edward C. Butler
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
| | - Colin G. Attwood
- Biological Sciences Department, University of Cape Town, Cape Town, South Africa
| | - Bruce Q. Mann
- South African Association for Marine Biological Research, Durban, South Africa
| | - Warren M. Potts
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
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Whitfield AK, Attwood CG, Cowley PD, Lamberth SJ, Mann BQ. No-take estuarine-protected areas: The missing armour for the conservation of fishes. KOEDOE - African Protected Area Conservation and Science 2020. [DOI: 10.4102/koedoe.v62i1.1648] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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Coscia I, Chopelet J, Waples RS, Mann BQ, Mariani S. Sex change and effective population size: implications for population genetic studies in marine fish. Heredity (Edinb) 2016; 117:251-8. [PMID: 27507184 PMCID: PMC5026757 DOI: 10.1038/hdy.2016.50] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 05/18/2016] [Accepted: 05/23/2016] [Indexed: 11/09/2022] Open
Abstract
Large variance in reproductive success is the primary factor that reduces effective population size (Ne) in natural populations. In sequentially hermaphroditic (sex-changing) fish, the sex ratio is typically skewed and biased towards the 'first' sex, while reproductive success increases considerably after sex change. Therefore, sex-changing fish populations are theoretically expected to have lower Ne than gonochorists (separate sexes), assuming all other parameters are essentially equal. In this study, we estimate Ne from genetic data collected from two ecologically similar species living along the eastern coast of South Africa: one gonochoristic, the 'santer' sea bream Cheimerius nufar, and one protogynous (female-first) sex changer, the 'slinger' sea bream Chrysoblephus puniceus. For both species, no evidence of genetic structuring, nor significant variation in genetic diversity, was found in the study area. Estimates of contemporary Ne were significantly lower in the protogynous species, but the same pattern was not apparent over historical timescales. Overall, our results show that sequential hermaphroditism may affect Ne differently over varying time frames, and that demographic signatures inferred from genetic markers with different inheritance modes also need to be interpreted cautiously, in relation to sex-changing life histories.
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Affiliation(s)
- I Coscia
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven (KU Leuven), Leuven, Belgium
| | - J Chopelet
- School of Biology and Environmental Science, University College Dublin, Dublin, Ireland
| | - R S Waples
- NOAA Fisheries, Northwest Fisheries Science Center, Seattle, WA, USA
| | - B Q Mann
- Oceanographic Research Institute, Durban, South Africa
| | - S Mariani
- Ecosystems and Environment Research Centre, School of Environment and Life Sciences, The University of Salford, Greater Manchester, UK
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Dunlop SW, Mann BQ, Cowley PD, Murray TS, Maggs JQ. Movement patterns of Lichia amia (Teleostei: Carangidae): results from a long-term cooperative tagging project in South Africa. African Zoology 2015. [DOI: 10.1080/15627020.2015.1058724] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Venter JA, Mann BQ. Preliminary assessment of surf-zone and estuarine line-fish species of the Dwesa-Cwebe Marine Protected Area, Eastern Cape, South Africa. Koedoe 2012. [DOI: 10.4102/koedoe.v54i1.1059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
A preliminary assessment of surf-zone and estuarine line fish was carried out in the DwesaCwebe Marine Protected Area (MPA), on the Wild Coast, South Africa. The purpose was to provide baseline data on inshore line-fish stocks in the MPA. A total of 28 species was recorded, of which 53% have a conservation status reflecting some concern and 43% are endemic to southern Africa. This highlights the value of the MPA for protection of important line-fish species. Within the MPA, localised differences were detected in species diversity, size frequency and catch per unit effort between unexploited and illegally exploited areas. These differences were more prominent in slow growing, long-lived species. It thus appears that illegal exploitation is negatively affecting fish populations within the MPA, which counteract and potentially could eliminate the benefits of fish protection typically associated with no-take MPAs. These results highlight the need for improved law enforcement and better communication with neighbouring communities to increase awareness. It is further recommended that the current no-take status of the MPA should be maintained. In addition, baseline fisheries information was collected on certain fish species that could be used to inform future conservation management of the MPA.Conservation implications: The Dwesa-Cwebe Marine Protected Area is unique and important for the conservation of key surf zone and estuarine fish species. However there is a significant risk to the fish populations due to illegal exploitation. Key interventions should include enhanced law enforcement but, more important, the creation of alternative livelihoods and long term sustainable benefits to local communities.
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