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by Theunis Piersma
It has been an infinite privilege to contribute to ecological research on the intertidal flats within the Bijagós Archipélago; higher nonetheless, to expertise a tropical tidal world the place individuals have made livings for lengthy occasions while leaving the ecosystems that they relied on just about intact. In the research now revealed in Wildlife Biology, we got down to confirm our impression that the ecological results of shellfish harvesting, particularly the results on the co-consuming migratory shorebirds, are small or absent (Coelho et al. 2024). The story revolves round two bivalve species, each with the capability to develop to lengths of a number of centimeters. The primary is a razor clam referred to as Tagelus adansonii and domestically referred to as ‘lingron’, the second is the West African bloody cockle Senilia senilis, domestically referred to as ‘combé’. On mudflats near the villages each bivalve species are harvested by hand by ladies and youngsters. Because the thick-shelled cockles reside nearer to the floor than the thin-shelled razor clams, the harvesting of lingron will probably be a tougher job. As a result of the 2 shellfish species play half in ceremonies that preserve societal group, their position for people is larger than ‘simply’ being essential meals gadgets.
Utilizing questionnaires, we systematically interviewed native shellfish harvesters and questioned them on their evaluation of shares, on inventory renewal and on harvest expectations. The island-specific variations between native administration regimes then enabled us to point out that on mudflats with formal safety, the situation of the shellfish shares had been thought of higher than in areas with conventional administration based mostly on cultural beliefs. There is no such thing as a proof for direct competitors between shorebirds and people, because the Bijagós harvesters chosen the bigger particular person shellfish, the birds choosing the smaller ones. Oblique impacts brought on by sediment disturbance or depletion had been both very small or absent. Shellfishing was highest in December, with sturdy declines in direction of northern spring. This might have decreased any type of disturbance in the course of the interval when shorebirds have to double their consumption charges to gasoline up earlier than their lengthy northward flights to the (principally) tundra breeding areas.
The proof that the handbook harvesting of the 2 shellfish species on intertidal flats within the Bijagós Archipélago is certainly a benign human exercise stands in stark distinction to what I’ve skilled at residence, within the Wadden Sea (truly utilized by precisely the identical migratory shorebirds), and in comparable temperate intertidal methods in Asia (Piersma et al. 2001, Kraan et al. 2007, Compton et al. 2016, Peng et al. 2021). Right here, invasive types of fishery, for instance the usage of mechanical harvesting strategies (or dredging; within the Wadden Sea) along with the seeding of mudflats by the commercially most worthwhile shellfish varieties (together with the usage of pesticides to regulate undesirable invertebrate predators; in coastal China) have affected intertidal meals webs to nice extents, most frequently with strongly detrimental impacts on the migratory shorebirds.
The cultural look after lingron and combé and for the mudflats that the bivalves reside in, makes the Bijagós individuals an inspiration for the remainder of the world.
Overlooking the mudflats within the northwest of Bubaque island, Bijagós, with some giant baoban timber marking the shoreline.
An early morning scne on the fringe of the mudflats within the east of Bubaque Island.
First creator Ana Coelho wanting right into a gully within the mangroves that mark the transition between open mud- and sandflats and the upper land of the Bijagós islands in lots of locations.
References:
Coelho, A.P., Ramos, C., Regala de Barros, A., Piersma, T. & Alves, J.A. (2024) Human–wildlife interactions on the tidal flats of the Bijagós Archipelago: does shellfishing have an effect on migratory shorebirds? Wildlife Biology 2024, e01134. https://doi/10.1002/wlb3.01134
Compton, T.J., Bodnar, W., Koolhaas, A., Dekinga, A., Holthuijsen, S., ten Horn, J., McSweeney, N., van Gils, J.A. & Piersma, T. (2016) Burrowing conduct of a deposit feeding bivalve predicts change in intertidal ecosystem change. Frontiers in Ecology and Evolution 4, 19. doi: 10.3389/fevo.2016.00019.
Kraan, C., Piersma, T., Dekinga, A., Koolhaas, A. & van der Meer, J. (2007) Dredging for edible cockles (Cerastoderma edule) on intertidal flats: short-term penalties of fisher patch-choice selections for goal and non-target benthic fauna. ICES Journal of Marine Science, 64, 1735-1742.
Peng, H.-B., Chan, Y.-C., Compton, T.J., Cheng, X.-F., Melville, D.S, Zhang, S.-D., Zhang, Z., Lei, G., Ma, Z. & Piersma, T. (2021) Mollusc aquaculture homogenizes intertidal soft-sediment communities alongside the 18,400 km lengthy shoreline of China. Range and Distributions 27, 1553–1567.
Piersma, T., Koolhaas, A., Dekinga, A., Beukema, J.J., Dekker, R., & Essink, Ok. (2001). Lengthy-term oblique results of mechanical cockle-dredging on intertidal bivalve shares within the Wadden Sea. Journal of Utilized Ecology, 38, 976-990.
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