This assessment is based on the revised taxonomic concept of Tridacna rosewateri, which includes T. lorenzi as a junior synonym.

In the most recent phylogeny, T. rosewateri is more closely related to Tridacna elongatissima (a Western Indian Ocean species) and T. squamosina (a Red Sea species) (Fauvelot et al. 2020), suggesting that the shell morphology among these three species would share greater similarities.

Live individuals rediscovered in the 2010s were initially described as a new species, Tridacna lorenzi, but preliminary genetic evidence revealed that they were T. rosewateri (Fauvelot et al. 2020). For now, T. lorenzi is considered a junior synonym of T. rosewateri. Although the genetic distinction between both species is not well supported, additional data is needed to confirm their conspecificity (Fauvelot et al. 2020).

These new findings generally confirm that T. rosewateri has indeed been a valid species since its last sighting in 1984.

Tridacna rosewateri has an extremely narrow geographic range. It is known only from a few localities: Mascarene Plateau (Saya de Malha and Nazareth Banks), Cargados Carajos Archipelago (St Brandon), and Tromelin Island. Despite extensive surveys, this species appears to be generally rare and occurs in small abundances.

Very little is known about this species as there had been no confirmed living records since its initial discovery in 1984. It was only rediscovered in the early 2020s, when the existence of living T. rosewateri was detected through genetic barcoding, but only a handful of sightings were reported after that. Population information, general use, and threats are generally lacking for this species, and population decline cannot be inferred accurately at this stage.

Based on the currently available data, this species has a very restricted area of occupancy (AOO is 48 km²) and may occur in few locations (possibly four location, but without information on threats it is not possible to confirm this). However, the range is not well understood and is confounded by taxonomic uncertainty, which also means that information on threats and ongoing potential decline is not clear, thus Tridacna rosewateri is currently listed as Data Deficient.

Tridacna rosewateri currently is known only from Mauritian waters, specifically in the Mascarene Plateau (Saya de Malha and Nazareth Banks), Cargados Carajos Archipelago (St Brandon), and Tromelin island. It is endemic to the Western Indian Ocean.

In general, the population information on Tridacna rosewateri is greatly limited. The distribution of this species comprises four areas that may represent four distinct locations: Saya de Malha and Nazareth Banks (Mascarene Plateau), Cargados Carajos Archipelago (St Brandon), and Tromelin Island. In a 1984 expedition, nine individuals were collected from the Saya de Malha Bank (currently administered by Mauritius), Indian Ocean (Sirenko and Scarlato 1991). They measured 6.7–19.1 cm in shell length.

Between 2011 and 2015, an expedition to the Cargados Carajos Archipelago, Mascarene Plateau, collected approximately 10 individuals (Monsecour 2016). The article also described the species (under the name Tridacna lorenzi) as common on the sand and loose rubble in very shallow waters (0–1 m). The material measured 11.3–26.0 cm in shell length. The identification of this species was later confirmed using both morphological and genetic evidence (Fauvelot et al. 2020).

In 2018, an expedition to the Nazareth Bank, Mascarene Plateau, discovered two T. rosewateri individuals in their natural habitats at depths of 38.60 m and 39.66 m, respectively (Ramah et al. 2021). The identification of these individuals was confirmed using morphological evidence (Ramah et al. 2021).

In the most recent phylogenetic studies, T. rosewateri is more closely related to Tridacna elongatissima (a Western Indian Ocean species) and T. squamosina (a Red Sea species) (Fauvelot et al. 2020, Tan et al. 2022). Due to small abundances, there is no current information on population structure for T. rosewateri.

There is very little information regarding the species’ habitat. Based on the handful of sightings, this species appears to have contrasting habits. Sirenko and Scarlato (1991) reported that individuals were collected in the community of sparse madrepore corals densely covered by seagrass (Thalassodendron ciliatum). On the other hand, Monsecour (2016) described specimens from turbid, shallow lagoon waters with observations that the species was living unattached to the substrate and sitting on sand and loose rubble. In the most recent sighting, Ramah et al. (2021) reported two individuals found in >30 m deep and attached (or partially embedded) to the coral substrates.

Its reported depth range is also highly variable, occurring in shallow turbid lagoon waters (0–1 m) (Monsecour 2016) to deep reef plateaus (12–13 m and 38–39 m) (Sirenko and Scarlato 1991, Ramah et al. 2021).

The threats to this species are currently unknown.

According to Monsecour (2016), T. rosewateri is locally common in the Cargados Carajos Archipelago, Mascarene Plateau. It is eaten by the local fishermen, and the shells are used as saucers or ashtrays.

The species is not known to be traded.

All giant clams (family Tridacninae) are listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) on the basis of so-called 'look-alike species', i.e., species whose specimens in trade look like those of species listed for conservation reasons (Wells 1997). Thus, CITES regulates the international trade in any of their parts (shells, tissues, alive or dead).

No other known conservation actions are in-place due to a lack of data on the population size, distribution and trends, life history and ecology, use and trade, and threats.

Further information on the distribution and population density, to allow confirmation of its full area of occupancy (AOO) and current and/or past population, would be needed in order to assess this species in a category.