304 K. Metcalfe et al.
the density and fidelity is probably largely driven by the ex- tensive use of macroalgal dominated rocky reefs, a geological extension of Point Indienne into Loango Bay (Giresse et al., 1980;Malounguila-Nganga et al., 2017), and so should forma key component of any proposed marine protected area. Although most of the tagged individuals remained with-
in thewaters of the Republic of the Congo, satellite telemetry data provided the first documented evidence of linkages between discrete foraging grounds in Central and Southern Africa, with one individual migrating south 505.9 km from Loango Bay, Republic of the Congo, toMussulo Bay, Angola, a 152km2 area that during 1983–1985 was documented to con- tain extensive coral, algal and seagrass flats (Carr & Carr, 1991). Given that green turtles are important indicators of habitat presence and condition (Scott et al., 2012;Hays et al., 2018) these findings suggest that this area, c. 30 years after its only documented survey, still contains re- sources to host green turtles. Few data are available on the abundance of green turtles in Mussulo Bay, but boat-based surveys and interviews conducted by Carr & Carr (1991) re- vealed that although juvenile, subadult and adult green tur- tles were present year-round (although there was seasonal variation in numbers), nesting was rare. Given these insights and the small sample size of our study it is important to in- terpret these findings cautiously. There are, however, three possible explanations for this movement. Firstly, given the small size of the individual tracked (individual I: CCL 74 cm; Table 1) relative to nesting adult females in the Gulf of Guinea (CCL: 98.3 ± SD 6.1 cm; Tomás et al., 2010) and the fact that Loango Bay predominantly comprises macro- algae, this behaviour could represent an ontogenetic shift from juvenile to adult foraging grounds as Mussulo Bay is dominated by seagrass and so may be more suited to the dietary or energy requirements of larger animals. Sec- ondly, given the departure date coincides with the end of the nesting season (September–April; Godgenger et al., 2009) this behaviour could be evidence of post-nesting migration to adult foraging habitat in Angola, a behaviour typically observed in green turtles, with individuals often having high fidelity to specific foraging locations between breeding seasons (Broderick et al., 2007; Garnier et al., 2012). Thirdly, this individual may have been tagged follow- ing migration from neritic developmental habitats else- where in the Gulf of Guinea, such as Corisco Bay, Gabon (given its proximity, c. 750 km), whilst on route to adult foraging habitat in Angola. Genetic analyses could help by providing detailed information of stock and natal origin (Bowen & Karl, 2007) that could disentangle the connec- tions that exist among this and other green turtle rookeries and foraging grounds along the Atlantic coast of Africa (Rees et al., 2016; Patrício et al., 2017, and references therein). Despitemarine turtles having been legally protected in the
Republic of theCongo since 2011 (Order No. 6075 establishing the animal species fully and partially protected by Law No.
48/83 21/04/1983), the complex nature of themarine environ- ment, and overlapping claims for space aswell as political and economic provisions (Metcalfe et al., 2018), mean that it is extremely unlikely that the Congolese government will be able to fully protect the entire range overwhichmarine turtles in our study were located. Nonetheless, significant efforts are being made by the Congolese government to implement a protected area in Loango Bay (Our Ocean, 2016), with a stakeholder led planning process underway (Congo Marine, 2018). If successful this would complement existing efforts to increase protection of marine turtle nesting beaches, inter- nesting areas and foraging grounds in other range states along the Central African coast (e.g. Gabon; Dawson et al., 2017; Pikesley et al., 2018). Our findings will thus ensure there is increased awareness regarding the location of core areas and critical foraging habitats that should be protected from deleterious activities such as fisheries and coastal de- velopment. This is of particular concern given the high incidence of marine turtle bycatch in artisanal fisheries in Loango Bay (Girard et al., 2014). Finally, despite the small sample size of this study, our findings have also provided the first documented evidence of linkages between Loango Bay and other poorly studied foraging grounds in the region, exemplifying the need for further tracking, tagging and gen- etic studies, and comprehensive strategies that span national and international jurisdictions, if conservation efforts tar- geted at marine turtles in this region are to be effective.
Acknowledgements Rénatura Congo are supported by funding from the Marine Turtle Conservation Fund (U.S. Fish & Wildlife Service, U.S. Department of the Interior). This study and data acquisi- tion were supported by funding from the European Union, Total E&P Congo andMPD/
Xstrata.KMand BJGwere supported by funding from The Waterloo Foundation and the Darwin Initiative (Projects 20-009/ 23-011/26-014), the latter through funding from the Department for Environment, Food and Rural Affairs in the UK. PDD was supported by a NERC Science Innovation Placement (NE/R007039/1).We thank two anonymous reviewers for constructive comments.
Author contributions Coordination, facilitation of fieldwork, de- ployment of satellite transmitters: NB, GB, AG, J-GM; data analysis: SKP, PDD, KM, BJG; data interpretation, writing: all authors.
Conflicts of interest None.
Ethical standards This research abided by the Oryx guidelines on ethical standards, and had approval from the University of Exeter Ethics committee, with appropriate permissions to conduct scientif- ic research and disseminate findings provided by the Ministry of Scientific Research and Technological Innovation in the Republic of the Congo (Permits: No. 023/MRSIT/DGRST/DMAST and No. 167/ MRSIT/IRF/DS).
References
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Oryx, 2020, 54(3), 299–306 © 2020 Fauna & Flora International doi:10.1017/S0030605319000309
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