Seamounts, plateaus and governance issues in the southwestern Indian Ocean, with emphasis on fisheries management and marine conservation, using the Walters Shoal as a case study for implementing a protection framework

Marsac, Francis; Galletti, Florence; Ternon, Jean-François; Romanov, Evgeny V.; Demarcq, Hervé; Corbari, Laure; Bouchet, Philippe; Roest, W. R.; Jorry, Stéphan; Olu, Karine; Loncke, Lies; Roberts, Michael J.; Ménard, Frédéric

doi:10.1016/j.dsr2.2019.104715

Cited by 19 publications

(12 citation statements)

References 42 publications

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“…Such observations could have implications for management, as ghost sharks have been shown to aggregate near highly productive areas also associated with high levels of fishing (e.g. Finucci et al., 2018; Marsac et al, 2020), and limited movement may increase susceptibility to fishing mortality.…”

Section: Resultsmentioning

confidence: 99%

“…The second region, the Southwest Indian Ocean, included four species [ Chimaera buccanigella , Chimaera didierae , Chimaera willwatchi , and Robin's Ghostshark ( Hydrolagus erithacus Chimaeridae)] where, since the 1970s, relatively recent fisheries rapidly developed on the high seas for commercially important deepwater stocks such as Orange Roughy ( Hoplostethus atlanticus , Trachichthyidae), Alfonsino ( Beryx spp.) and D. eleginoides (Bensch et al., 2009; Marsac et al, 2020). Deepwater sharks have been both targeted and taken incidentally in a number of gear types including demersal trawl, midwater trawl, demersal longline and demersal gillnet (Marsac et al, 2020; Georgeson et al, 2019), but there are no data available for ghost sharks from this region.…”

Section: Resultsmentioning

confidence: 99%

“…and D. eleginoides (Bensch et al., 2009; Marsac et al, 2020). Deepwater sharks have been both targeted and taken incidentally in a number of gear types including demersal trawl, midwater trawl, demersal longline and demersal gillnet (Marsac et al, 2020; Georgeson et al, 2019), but there are no data available for ghost sharks from this region. It is not known if fishing activities are driving population reductions.…”

Section: Resultsmentioning

confidence: 99%

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Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks

et al. 2020

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Ghost sharks (subclass Holocephali) remain a largely data‐poor group of cartilaginous fishes. The general paucity of attention may partially be related to identification and unresolved taxonomic issues, occurrence in the deep oceans, and their low value and interest in fisheries (which some notable exceptions). Here, we synthesize and assess the extinction risk of all known extant ghost sharks (52 species) by applying the IUCN Red List of Threatened Species Categories and Criteria. Ghost sharks have a low proportion of threatened (8%) and Near Threatened (8%) species, with most species (69%) assessed as Least Concern. The group still exhibits some data deficiency (15%), and biological information is lacking for most species. Endemism is high, with 37% of species known from only one location or one country. Species richness was highest in the Northeast Atlantic, off the northwest coast of Africa (Morocco to Mauritania), the East China Sea, New Zealand and off the northwest coast of South America (Ecuador and Peru). Ghost sharks are predominately taken as by‐catch, but some targeted fishing and/or retention for the liver oil trade occurs. Species‐specific reporting, monitoring and management are required to assess population trends, and further investigation is needed on trade and use, particularly for higher risk species including the sicklefin chimaeras (genus Neoharriotta) and the American Elephantfish (Callorhynchus callorhynchus, Callorhinidae).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks

et al. 2020

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“…Seamounts are often seen as key habitats for marine life, even more so in oligotrophic waters where they are considered as hotspots for life and biodiversity (Genin and Boehlert, 1985;Dower et al, 1992;Rogers, 1994;Mouriño et al, 2001). In addition, many are located in Areas Beyond National Jurisdiction (ABNJ) where there is little regulation, leaving them targeted by industrial fisheries (Marsac et al, 2020) and sometimes resulting in the total collapse of the fishery (Koslow, 1997;Clark, 2001;Pitcher et al, 2010).…”

Section: Contextmentioning

confidence: 99%

Observation of a mesoscale eddy dipole on the northern Madagascar Ridge: Consequences for the circulation and hydrography in the vicinity of a seamount

Vianello

Herbette

Ternon

et al. 2020

Deep Sea Research Part II: Topical Studies in Oceanography

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Based on satellite and in situ data, the dynamic characteristics and vertical structure of a surface intensified mesoscale dipole recently expelled from the South East Madagascar Current (SEMC) is described for the first time. The dipole was surveyed 250 nautical miles south of Madagascar between 14 and 23 November 2016, during west-east and south-north transects carried out over the northern Madagascar Ridge. The dipole consisted of two counter-rotating vortices of similar size (100 km) and intensity (0.7 f), and an intense southwestward jet (150 cm s-1) in the frontal region between the two eddies. The cyclonic eddy was lying on the western side of the anticyclonic eddy. With azimuthal velocities reaching 100 cm s-1 at the surface and decreasing slowly with depth (40 cm s-1 at -600 m), this MAD-Ridge dipole was defined as a highly non-linear (Ro∼0.7) isolated eddy-type structure (cβ ∼ 11 cm s -1 and U/cβ ∼ 0.7) capable of trapping and advecting water masses over large distances. The enhanced concentration of chlorophyll-a found in the cyclone relative to the anticyclone could be tracked back to the spin-up phase of the two eddies and attributed to eddy-pumping. The eddy cores were located above the pycnocline (1026.4 kg m-3), within the upper 600 m, and consisted of varieties of Subtropical Underwater (STUW) found within the SEMC. The STUW found in the anticyclone was more saline and oxygenated than in the cyclone, highlighting mixing with the inshore shelf waters from the southeastern coastal upwelling cell off Madagascar. Observations suggest that the dipole interacted strongly with the chaotic bathymetry of the region, characterized by a group of five seamounts lying between -240 m and -1200 m. The bathymetry blocked its westward advection, trapping it in the vicinity of the seamount for more than 4 weeks, so enhancing the role of the eddy-induced velocities in stirring the surrounding water masses. Squeezed between the southern Madagascan shelf and the northern flank of the anticyclone, two filament-like dynamic features with very different water-mass properties could be observed on the southnorth transect: i) one filament highly concentrated in chlorophyll-a demonstrating the capacity of the eddy to export shelf water offshore; ii) intrusions of a more southern-type of STUW generally found south of the South Indian Counter Current (SICC) recirculating on the external flanks of the anticyclone. Although the observed circulation and hydrography were largely constrained by the presence of the mesoscale eddy Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.dipole, unmistakable fine-scale dynamics were also observed in the vicinity of the MAD-Ridge seamount, superimposed onto the mesoscale eddy flow.

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“…Beyond the lack of fundamental scientific knowledge, there are significant additional barriers to seamount ecosystem management. There is a need for comprehensive and effective governance frameworks for marine biodiversity in the high seas (Marsac et al, 2019). The limited frameworks to support these complex ecosystems is also challenged with the difficulty of managing human activities in the high seas, including monitoring, control and surveillance (De Santo, 2018).…”

Section: Introductionmentioning

confidence: 99%

Tourist Preferences for Seamount Conservation in the Galapagos Marine Reserve

Ison

Marti-Puig

et al. 2021

Front. Mar. Sci.

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Seamounts provide oases of hard substrate in the deep sea that are frequently associated with locally enhanced biological productivity and diversity. There is now increasing recognition of their ecological and socio-economic importance. However, management strategies for these habitats are constrained not only by limited ecological understanding but by the general public’s understanding of the pressures facing these ecosystems. This study adds to the growing literature on willingness to pay for conservation of deep-sea ecosystems and species by undertaking a stated preference survey to assess tourist’s awareness of seamounts and their preferences for protection within the Galapagos Marine Reserve. Visitors’ perceptions of seamount biodiversity must be studied because tourists are key drivers of the Galapagos economy and account for 41% of the Marine Reserve budget. Our survey captured the attitudes, perceptions and willingness to pay of tourists for an increase in the entrance fee to the Galapagos Marine Reserve. Results showed tourists were willing to pay on average US$48.93 in addition to existing entrance fees. The results of this study support the willingness to develop a multiuse management plan for the Galapagos Marine Reserve, balancing conservation, local communities livelihoods and sustainable tourism. Our results evidence a willingness to support and fund conservation, which is of critical importance to both the Galapagos National Park and local non-governmental organizations heavily reliant for their work on entrance fees and donations respectively. Overall, the conclusion from this study is that, despite limited knowledge, visitors of the Galapagos Islands attach positive and significant values to the conservation of seamount biodiversity.

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Seamounts, plateaus and governance issues in the southwestern Indian Ocean, with emphasis on fisheries management and marine conservation, using the Walters Shoal as a case study for implementing a protection framework

Cited by 19 publications

References 42 publications

Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks

Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks

Observation of a mesoscale eddy dipole on the northern Madagascar Ridge: Consequences for the circulation and hydrography in the vicinity of a seamount

Tourist Preferences for Seamount Conservation in the Galapagos Marine Reserve

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