Tridacna noae was previously relegated as one of the many variants of T. maxima. However, McLean (1947) pointed out that T. noae had moderately to tightly spaced scutes on the upper (i.e., ventral) shell compared to the close-set scutes of T. maxima. Also, in living specimens, T. noae can be readily distinguished from T. maxima through discrete teardrop-shaped markings on the mantle, typically bounded by white, yellowish, pale green or pale blue margins. Furthermore, genetic analyses showed that T. noae and T. maxima are distinct (Su et al. 2014). Another described species, Tridacna ningaloo from Western Australia (Penny and Willan 2014), is similar in appearance to T. maxima and T. noae, but Borsa et al. (2015) established that T. noae and T. ningaloo have no apparent genetic or morphological differences (except, possibly, in mantle patterns). Thus, T. ningaloo should be regarded as a junior synonym of T. noae.

There was no prior Red List assessment for this species as it was previously considered as one of the many variants of T. maxima.

Tridacna noae has a broad geographic distribution based on the current information: from the Ryukyus (southern Japan), Taiwan, the Philippines, Indonesia, Western Australia, Cook Island, some of the Pacific Islands (e.g., Palau, Papua New Guinea, Samoa, Solomon Islands, American Samoa, Fiji), and Christmas Island. On the other hand, seeing how new geographic records are being added, the geographic range and distribution are incomplete. Reef surveys generally confirm the presence of abundant T. noae throughout its geographic range, as well as strong signs of natural recruitment replenishing local stocks. In some locations, the distribution of this species is patchy, but the overall numbers appear to be moderately stable. Given that it is associated with coral reefs, there is evidence of declining quality of habitats. There is no strong evidence to suggest a decline in global population, but the species continues to face localised threats including overharvesting in specific communities for local consumption or the marine aquarium trade.

As this species is popular in the aquarium trade (formerly known as the Teardrop Maxima), the mariculture knowledge is well-established and has been successful in raising cultured individuals. However, there have been limited efforts in translocating or restocking the cultured clams for conservation, or these efforts are not well understood or underreported (i.e., it is unclear whether efforts have led to an increase in stock numbers). In addition, breeding programmes typically use a limited number of genetic populations. This narrow genetic basis could reduce the species’ resilience to environmental changes and diseases in the future. Giant clams are vulnerable to climate change, as rising temperatures can cause bleaching of their photosymbionts. Ongoing monitoring is important to provide early warning of potential future declines.

Based on the best available information, this assessment places Tridacna noae as Least Concern. CITES provides ongoing protection for this species. The species is present in a small area of occupancy (AOO), and has ongoing threats, but there is no current evidence for ongoing population decline. Additional information about the impacts of threats from fishing, ornamental trade, or habitat degradation, would prompt a reassessment.

Tridacna noae is a recently resurrected species, separated from T. maxima by both morphological and genetic data (Su et al. 2014); because of historical confusion with T. maxima, the geographic range information may be incomplete. The current reported geographic range is from the Ryukyus (southern Japan), Taiwan, the Philippines, Indonesia, Western Australia, Cook Island, some of the Pacific Islands (e.g., Palau, Papua New Guinea, Samoa, Solomon Islands, American Samoa, Fiji), and Christmas Island (Borsa et al. 2015, Militz et al. 2015, Neo and Low 2017, Marra-Biggs et al. 2022).

Since the resurrection of this species, there has been a growing number of studies on the distribution and abundance of Tridacna noae. However, the current information is insufficient for estimating global population status.

The presence of this species in the Ryukyus Archipelago was first highlighted by Kubo and Iwai (2007), who recorded its existence in Naha and Ishigaki‐jima Island and its absence in Onna Village. Kubo and Iwai (2007) were the first to raise the potential confusion between T. noae and T. maxima, as the giant clam is in high demand in local markets, suggesting that the two species should not be given the same Japanese name. It was also found that the relative abundance of T. noae in these fisheries' surveys was very low (1.9%) compared with that of the dominant T. maxima (98.1%) (Kubo and Iwai 2007). A subsequent study on giant clam distribution in Okinawa Island found that the relative abundances of T. noae and T. maxima were 3.0% and 97.0%, respectively, suggesting that T. noae is generally uncommon or rare in the Ryukyu Archipelago.

In the Kavieng Lagoon system, Papua New Guinea, almost 42% of the specimens previously recorded as T. maxima could now be classified as T. noae. Also, re-surveys of the Ningaloo Reef Marine Park revealed the presence of T. noae only, with no signs of T. maxima (Johnson et al. 2016); these recent findings challenge an earlier survey reporting the presence of (only) T. maxima in the same study site (Black et al. 2011). Snorkel surveys on the reefs in Yap (Federated States of Micronesia) also identified high abundances of T. noae, which would have previously been recorded as T. maxima (C.C.C. Wabnitz pers. obs. 2016). Moreover, in Nauru, the only species found on the reefs during dedicated reef invertebrate surveys were recently re-identified as T. noae (D. Thoma pers. comm. 2016).

The densities of T. noae varied widely among the few surveys available on this species. In Australia, the reported densities ranged from 5 to 28 individuals per 100 m² (Black et al. 2011, Johnson et al. 2016); in the Kavieng Lagoon (Papua New Guinea), the reported density was 0.273 individuals per 100 m² (Militz et al. 2015); in Dongsha Atoll in South China Sea, the reported density was 1.846 individuals per 100 m² (Neo et al. 2018); and in Okinawa-Ryukyu Archipelago, the reported density was 0.04 individuals per 100 m² (Neo et al. 2019).

The initial phylogeographic structure of this species was examined by Huelsken et al. (2013, as Tridacna sp.), who reported substantial genetic differences between the populations from Ningaloo Reef and the Solomon Islands. The latter patterns were also observed in other Tridacna species, including T. crocea and T. maxima. This research was expanded by Fauvelot et al. (2019) to include a wider geographic range of T. noae using mitochondrial and microsatellite markers. Results from two types of genetic markers revealed a consistent population structure, partitioning T. noae into three distinct lineages: (1) eastern half of the Indo-Malay archipelago and Western Australia, (2) Melanesia and Micronesia, and (3) Central Polynesia. Similar to other Tridacna species, this limited gene flow patterns suggest restricted expansion of populations and that may put populations at risk in the future.

Based on mitochondrial haplotypes, three lineages have been identified within the distribution range of the species: the western tropical Pacific, Indonesia and islands near eastern Australia, and the central Pacific islands. Within each haplotype, a weak or non-existent relationship between genetic and geographic distances was observed, suggesting well-connected populations within each region (Fauvelot et al. 2019). Given that giant clams are broadcast spawning species with pelagic larvae, their genetic connectivity is likely influenced significantly by ocean currents. This genetic connectivity within each region has been corroborated by other studies, such as those conducted at Dongsha Atoll and Hainan, which indicate low genetic diversity within local and adjacent populations (Neo et al. 2018, Chao et al. 2021).

As a recently resurrected species, data on the habitat and distribution of Tridacna noae are scarce but inferred to be similar to that of T. maxima. This species is generally found in intertidal reef flats and shallow lagoons, occupying depths of 1–15 m (Borsa et al. 2015, Militz et al. 2015). It is occasionally found as deep as 30 m (Fauvelot et al. 2020). Individuals may grow up to 30 cm, with the largest reported individual at 35 cm (Militz et al. 2015). It is also a boring species, with individuals often found partially embedded within reef substrata.

Research on the reproduction ecology of T. noae is increasing steadily, with the early attempts of ex situ breeding carried out in Taiwan (Su 2013, Su et al. 2021) and some culture trials for mariculture grow-out and possibly aquarium trade in the Federated States of Micronesia (C.C.C. Wabnitz pers. obs. 2016). Embryology, larval development, and feeding ecology of T. noae in Papua New Guinea have recently been described (Southgate et al. 2016, 2017; Braley et al. 2018; Militz et al. 2021). Breeding trials between T. maxima and T. noae provided preliminary evidence that both species can hybridise and produce juveniles (Militz et al. 2017, 2019), suggesting that hybrids could exist in the wild.

The threats to this species are harvesting for food (Kubo and Iwai 2007, Neo et al. 2018, 2019) and the ornamental aquarium trade (Wabnitz and Fauvelot 2014). This species appears to be primarily collected for mariculture research or sale for the aquarium trade (e.g., Federated States of Micronesia; C.C.C. Wabnitz pers. obs. 2016). Fishing of the species may also be listed as a potential threat.

This species has been fished for food (Kubo and Iwai 2007 in Okinawa, Japan; Neo et al. 2018 in Dongsha Atoll, South China Sea), but harvesting data is limited. In addition, any previous exploitation of T. noae would not have been reported because of previous confusion with T. maxima.

Notably, according to Wabnitz and Fauvelot (2014), reef aquarists have always informally distinguished T. noae from T. maxima specifically because of the teardrop-shaped patterns on the mantle, referring to them as teardrop maxima. Due to their distinct features, teardrop maximas tend to fetch a higher price in the aquarium trade market. This species has been seen in aquarium markets in Guangzhou and Hong Kong (M.L. Neo pers. obs. 2016). However, the trade volume is limited as they are sometimes not differentiated when reporting to the CITES Trade Database (https://trade.cites.org/). For instance, Vietnam appears to be exporting wild-caught T. noae as T. maxima in the wildlife trade (M.L. Neo pers. obs. 2018).

All giant clams (subfamily 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). The Animal Committee of CITES held a meeting to provide updates on species taxonomy, which included T. noae (UNEP-WCMC 2018).

In situ protection of stocks: Though non-specific, giant clams are protected under wildlife laws in some countries (e.g., Indonesia, the Philippines, and Australia).

Stock enhancement through mariculture: Several ex situ attempts have been conducted to breed T. noae in Taiwan for restocking purposes (Su 2013, Su et al. 2021). Some culture trials for mariculture grow-out were reported in the Federated States of Micronesia (C.C.C. Wabnitz pers. obs. 2016), while successful hatchery production has been reported in Fiji (P.C. Southgate pers. comm. 2018). Aquaculture studies on the species are growing steadily (e.g., Southgate et al. 2016, 2017; Militz et al. 2017 2019, 2021; Braley et al. 2018; Lee et al. 2023).

Aquarium trade: This species is well-known in the ornamental trade as the teardrop clams or teardrop noae (formerly known as teardrop maxima, Wabnitz and Fauvelot 2014). Because of the taxonomic confusion with T. maxima, the records for T. noae trade have not been properly captured in the CITES Trade Database. In addition, there is limited information regarding the mariculture of this species for the aquarium trade (Vogel and Hoeksema 2024).

This species has been assessed as a proposed threatened species in a status review for the US Endangered Species Act, also on the basis of being a look-alike species to other protected species (NOAA, 2024).