First Scientific Records of the Invasive Red Swamp Crayfish, Procambarus clarkii (Girard, 1852) (Crustacea: Cambaridae) in Malta, a Threat to Fragile Freshwater Habitats

Abstract

This study reports the first records of the invasive fresh water red swamp crayfish, Procambarus clarkii in Malta, first spotted in the wild in summer 2016. In spring 2017, 26 specimens of P. clarkii were collected, sexed, measured and identified both morphologically and genetically. The distribution and density of the species along the same valley were investigated at Fiddien Valley and Chadwick Lakes. As these two locations are associated with one of the major valley systems that cross the island, the presence of this prolific, aggressive and opportunistic feeding crayfish species increases the vulnerability of native freshwater species.

Brought more than twice: the complex introduction history of the red swamp crayfish into Europe

“…The nine red swamp crayfish specimens from Kenya shared a common haplotype, while a different haplotype was common to the 10 specimens from Malta reported by Vella et al (2017). The Kenyan haplotype was identical to the one found in Western Europe but was not present anywhere else (Hap_11, GenBank: MK026681 in Oficialdegui et al, 2019).…”

“…Briefly, genomic DNA was extracted from muscle tissue using a modified DNA saltextraction protocol and proteinase K; a fragment of the mitochondrial gene coding for the cytochrome c oxidase subunit I gene was amplified using the primers LCO1490 and HCO2198 and PCR amplifications were carried out in a 20-ml reaction volume. In addition, we also re-assessed 10 sequences (559 bp; Genbank Accession number: MF170527-36) recently published by Vella et al (2017), referring to a population established in Malta, as well as the 65 haplotypes (608bp) reported by Oficialdegui et al (2019). The 84 sequences in total were then analysed.…”

“…In fact, it has already been suggested that several red swamp crayfish populations in Central Europe could have originated as consequence of aquarium releases (see Chucholl, 2013), though there are no genetic evidences. The very recent origin of the Maltese population, first detected in 2016 (Vella et al, 2017), and its occurrence together with other invasive decapods widely used by aquarists (e.g., Procambarus virginalis or Atyopsis moluccensis) (Deidun et al, 2018), suggest that pet trade may have facilitated the arrival of the invasive crayfish to Malta. The identical genetic identity of this Maltese population to haplotypes found in China (Oficialdegui et al, 2019) and that live crayfish specimens imported into Europe are originated by pet trade from southeast Asian countries (Chucholl, 2013;Patoka et al, 2014) suggest an Asian origin.…”

Mechanical excavation of wetland habitat failed to eradicate invasive American red swamp crayfish (Procambarus clarkii) in Malta

“…et al, 2004) and have an average annual movement range of 44 m (Gherardi et al, 2000). Given the limited movement range, the lower abundance and smaller median carapace length of crayfish in the lower reaches (Figure 4), we believe the crayfish within the lower reaches might have relatively recently colonized this area from the upper reaches of the stream (the target of the restoration project), where the crayfish have been known to exist since at least 2016 (Deidun et al, 2018;Vella et al, 2017).…”

“…Islands in 2016 (Deidun et al, 2018;Vella et al, 2017) There are records of other invasive species of crayfish in Malta, in particular, the Australian red claw crayfish Cherax quadricarinatus, the marbled crayfish Procambarus virginalis (in a nearby water reservoir) and the signal crayfish Pacifastacus leniusculus (Deidun et al, 2018), but their presence in the Fiddien valley system is unknown.…”