Low-Cost Citizen Science Effectively Monitors the Rapid Expansion of a Marine Invasive Species

Abstract

Citizen science and informed citizens have become fundamental in providing the first records and accounts about the expansion of numerous non-indigenous species. However, implementing a successful citizen science campaign can be expensive and particularly difficult for aquatic species. Here, we demonstrate how a low-cost citizen science campaign and its outreach plan in social and traditional media enabled to track the expansion of the Atlantic blue crab Callinectes sapidus Rathbun, 1896 along the coast of Algarve (southern Portugal, Europe). We describe the outreach strategy and a cost-benefit analysis of the first year of the citizen science campaign. Social media platforms allowed us to reach a significant number of citizens (over 31,500 clicks in Facebook publications), while traditional media gave national visibility to the citizen science campaign and biological invasions. In only 1 year, we documented the spread of the invasive Atlantic blue crab across the entire 140 km of the Algarve coast with 166 valid observations referring to 1747 specimens, submitted by 62 citizen scientists. We spent 0 € on the citizen science campaign, but considering the time invested in the campaign the cost would have summed up to 3,751 €, while the total minimum cost for one scientist to go to the field and retrieve the equivalent information would have exceeded 11,000 €. We used free online tools of communication to obtain the records about the Atlantic blue crab, instead of a dedicated web platform or mobile app, and handled social media accounts ourselves, which saved us at least 18,815 €. The citizen science campaign revealed that the Atlantic blue crab is unequivocally established in southern Portugal and that females appear to exhibit summer migrations to coastal areas to spawn as in the native area. Overall, our low-cost citizen science campaign effectively documented the rapid spread of a marine invasive species while providing some insights into its ecology. Our strategy can be easily replicated and implemented elsewhere in the world to tackle the ever-growing problem of biological invasions while increasing the scientific literacy of local populations.

Diet of the Invasive Atlantic Blue Crab Callinectes sapidus Rathbun, 1896 (Decapoda, Portunidae) in the Guadalquivir Estuary (Spain)

“…Invasive species disrupt the functioning of ecosystems and the trophic processes in which they rank the most significant disruptors of established ecological networks (Wainright et al 2021). The invasive Atlantic blue crab Callinectes sapidus Rathbun 1896, (Decapoda, Portunidae), native to the east coast of North and South America, has rapidly dispersed along the western Euro-African area since the mid-2010s (Mancinelli et al 2021;Encarnação et al 2021;González-Ortegón et al 2022;Chairi and González-Ortegón 2022) and is known for multiple ecological impacts in areas of the Mediterranean Sea where they have been established for a long time (Mancinelli et al 2017b).…”

“…The populations established along the Mediterranean Sea have supported profitable fisheries for the last 50 years (Ayas and Ozogul 2011;Kevrekidis et al 2013). In the Gulf of Cadiz (SW Iberian Peninsula, Europe) and associated estuarine ecosystems, the Atlantic blue crab abundance increased substantially, and its distribution rapidly expanded since they were first detected in the region (Mancinelli et al 2017a, c;Morais et al 2019;González-Ortegón et al 2020;Encarnação et al 2021).…”

Free Pass Through the Pillars of Hercules? Genetic and Historical Insights Into the Recent Expansion of the Atlantic Blue Crab Callinectes sapidus to the West and the East of the Strait of Gibraltar

“…In the Mediterranean Sea, it was reported in the Aegean Sea as early as the 1930s, and in the adjacent Turkish coast in 1949 (Enzenroß et al, 1997). Since then, this species has greatly expanded its distribution along the entire Mediterranean Sea and adjacent seas, but also in the North Sea and the Atlantic coast of the Iberian Peninsula and northern Africa (Encarnação et al, 2021;Mancinelli et al, 2021;Chaouti et al, 2022;González-Ortegón and Chairi [in press)]. On the western coast of the Iberian Peninsula, the first record dates back to 1967 in the Tagus Estuary (Portugal), but only a few sporadic records were made since then in this region (Encarnação et al, 2022).…”

“…In the Gulf of Cadiz, the first published record of Atlantic blue crab dates back to 2016 (Morais et al, 2019), however, a male adult specimen was already collected in the Guadalquivir Estuary in 2002 (Rodríguez & Cuesta, unpublished data). Since 2016, the species expanded rapidly westwards along the southern coast of Portugal and has now reached the southwestern coast of Portugal (Encarnação et al, 2022;Vasconcelos et al, 2019;Encarnação et al, 2021). Meanwhile, in the Alboran Sea, the first record was made in 2017 in Nador Lagoon (Morocco, Mediterranean Sea) (Chartosia et al, 2018), and the species later expanded to the east and west (Taybi and Mabrouki, 2020).…”

“…Considering these genetic data, and the fact that adult blue crabs have a considerable ability to swim and travel up to hundred kilometers (Kara and Chaoui, 2021) or the high fecundity of females, which would allow the passive transport of a huge amount of larvae by oceanic currents between the Mediterranean Sea and the Gulf of Cadiz, it is more likely that the populations of C. sapidus in the Gulf of Cadiz and Alboran Sea result from the expansion of the species along the Mediterranean Sea -single introduction -or to a secondary introduction event within the invaded range. For example, the timeline of the first reports along the southern coast of the Iberian Peninsula were made sequentially from the east to the west, between the Ebro Delta and the Gulf of Cadiz, in just seven years (Castejón & Guerao, 2013;Morais et al, 2019;González-Ortegón et al, 2020;Encarnação et al, 2021). Additionally, the haplotype diversity is extremely low between populations -only two haplotypes are present.…”