Habitat destruction by destroying the foundation species is one of the important damages caused by invasive species.The red alga Kappaphycus alvarezii is commercially important as a source of carrageenan and has been introduced in many countries for commercial cultivation.Due to its invasive potential, this red alga has been widely reported to be a big threat to coral reefs in many reef regions including the Gulf of Mannar (GoM) in India.Here we report the invasion of red alga K. alvarezii to new reef sites in Valai and Thalaiyari Islands within GoM and the coral mortality caused in the newly invaded sites from 2019 to 2021.We also discuss the geographical extension of K. alvarezii within GoM from its initial invasion point and its impact on corals from 2005 to 2021.During our regular reef monitoring surveys within GoM, we found K. alvarezii to be overgrowing live acroporan corals of Valai and Thalaiyari islands of GoM for the first time in May 2019 and we used standard underwater protocols to assess the impact of the alga on corals at different time periods between May 2019 and March 2021.Live coral cover in the invaded area decreased by 9.1% in Valai Island and by 3.9% in Thalaiyari Island due to the coral mortality caused by K. alvarezii during the study period.K. alvarezii was observed to overgrow live corals and kill them eventually at the affected sites.Acropora branching morphotype was found to be the most affected by K. alvarezii.Various measures including manual removal have been taken to keep the invasion under control.In spite of the efforts to eradicate K. alvarezii from the reefs of GoM, it remains a persistent threat to the survival of corals.We emphasize the importance of properly managing the already stressed and ecologically sensitive reef resources of GoM from the invasion of K. alvarezii in order to guarantee the long-term livelihood benefits of dependent fisher-folk.

The western mosquitofish, Gambusia affinis (Baird & Girard, 1853), from North America, is considered one of the 100 worst invasive species in the world. In October 2020, sixteen individuals of western mosquitofish were captured from the Eastern Himalayas of China, making this the first record of western mosquitofish in the region. Since the Eastern Himalayas is part of the Himalaya Biodiversity Hotspot, mosquitofish could represent a potentially significant threat to local biodiversity in the whole Himalaya or the Qinghai-Tibetan Plateau (QTP), including indigenous fishes. More monitoring and management of western mosquitofish should be conducted in the Eastern Himalayas to mitigate invasion risk and protect the native fish biodiversity from this exotic species.

Perkinsus marinus belongs to the Chromista Kingdom and is recognized as an opportunistic parasite of mollusks native to the west coast of the Atlantic Ocean.The native range of this species is the Atlantic Ocean, however, it was introduced to the Gulf of California (GC) by a transfaunation of oysters.This microorganism has invaded new niches in the GC and continues to colonize different species of bivalve mollusks.For the first time, P. marinus was detected in the mussel Mytella strigata from the southeast coast of the GC in 2020 by staining and molecular techniques.The moderate number of cells of this myzozoan in the mussel coincides with the reports for other species of ostreids, venerids, and mytilids in the area, which suggests that it is expanding its geographical range and host species.The invasive potential of the parasite in new environmental niches and species of mollusks with commercial importance elevate the need for a risk assessment.

The penaeid shrimp Penaeus aztecus Ives, 1891 has been collected off the Catalan coast for the first time. This represents the first report of the species for the Iberian Peninsula waters. Its morphological description, as well as the DNA sequenced fragment, agree with the descriptions assigned to Penaeus aztecus. This constitutes the first record of the species in the Spanish Mediterranean coast and the confirmation the species westward expansion along the Mediterranean Sea probably been drifted from the later invasion in the Gulf of Lions.

The occurrence of the exotic Atlantic blue crab Callinectes sapidus Rathbun, 1896 (Crustacea: Decapoda: Portunidae) is reported for the first time from the Moroccan Atlantic coast.Working with local fishermen, we gathered 160 records of the Atlantic blue crab from several estuarine, coastal and marine areas, in the period between June and August 2021.These new records confirm its establishment in the Atlantic coasts of North Africa, suggesting a southern range expansion.These findings, likely exacerbated by growing populations along the Atlantic coast of Morocco and temperate coastal waters, provide new insights into the invasion dynamics of this species in the northeast Atlantic Ocean.

During intertidal rocky shore surveys on the east coast of South Africa in 2018, the
\nnon-indigenous giant purple barnacle Megabalanus tintinnabulum (Linnaeus, 1758),
\na well-known fouling and globally-invasive species, was discovered. This motivated
\na survey of the entire South African east coast at 31 rocky shore sites, which
\nconfirmed that breeding populations of this barnacle have been established in most
\nwave-exposed low-shore intertidal habitats between the Mozambique border and
\nMkambati Nature Reserve and that its current South African distribution spans 725
\nkm of coastline. Another non-indigenous and common fouling species, the titan
\nacorn barnacle M. coccopoma (Darwin, 1854), was discovered at three of the sites,
\nits local distribution spanning 370 km of coastline. While currently uncommon, this
\nspecies is known to reach high densities in other non-native regions. Both Megabalanus
\nspecies are large and conspicuous and were not found during extensive surveys in
\nthe 1990s and early 2000s, suggesting that their introduction and spread occurred
\nwithin the past two decades.