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Examples of traditional fishing and uses of giant clams' meat and shells by local communities. (a) Fishing on a 'mapiko' (accumulation of giant clam shells) at Napuka atoll (French Polynesia). (b) Shells of giant clams used as flower pots in a garden on Mare Island (New Caledonia). (c) Skewers of smoked giant clams for sale at Kavieng market (Papua New Guinea). (d) Shells of the giant clam (T. gigas) and the fluted giant clam (T. squamosa) used for garden ornamentation (Kavieng). All pictures by S. Andr efou€ et.
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Giant clam populations have been over-exploited throughout their range over the past decades for their meat and shells. Tridacna maxima, commonly known as the ‘small giant clam’, has remained relatively untargeted by fishers in areas where larger species occur (e.g. Tridacna squamosa), and high densities of the species are still observed on some is...
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... species of giant clams were traditionally exploited by local fishers for meat consumption or shell use as common household items (e.g. food dishes or garden ornaments; Mingoa-Licuanan and Gomez 2002) (Fig. 1). Giant clams have important cultural significance as they are inte- grated into cults and traditional myths (Chong 2006) and are seen as items of prestige (Hviding 1993;Lancrenon and Zanette 2011). Giant clams are also of distinct ecological significance as they contribute to reef development and are an impor- tant prey item and ...
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... Globally, it is widely documented that the populations of giant clams are steadily declining throughout the Indo-Pacific region (see Apte et al., 2010;Van Wynsberge et al., 2016;Neo et al., 2017;Mehrotra et al., 2021;Braley, 2023). For the first time, this study provides an overview of giant clam population trends in Malaysia, and a comprehensive assessment on their population status with detailed species diversity, distribution, density, and size-class structure across Peninsular Malaysia. ...
... A plausible explanation could be that giant clam populations on the west coast did not thrive as the local conditions of higher sedimentation and poorer coral reef coverage (Toda et al., 2007;Safuan et al., 2018) made it challenging for their survival and recruitment (Elfwing et al., 2001;Neo and Todd, 2012). In contrast, giant clam densities recorded on the east coast Peninsula were significant, if not higher than most global estimates that typically ranged from 0.001 to 0.01 clams per 100 m 2 (Van Wynsberge et al., 2016;Neo et al., 2017). Looking across the South China Sea, giant clam densities of Peninsular Malaysia (0.5-20.4 clams per 100 m 2 ) are one of the highest compared to other populations: South China Sea (Spratly Islands) (Calumpong andMacansantos, 2008, Lasola andHoang 2008;Van Long et al., 2008); Singapore (Neo and Todd, 2012); Anambas Islands (Harahap et al., 2018); South China Sea (Dongsha Atolls) (Neo et al., 2018); Gulf of Thailand (Mehrotra et al., 2021); Sabah (Bavoh et al., 2021). ...
... To explain the disparity in giant clam densities across the region, the "reef type" may have substantial effects on densities in a meta-analysis (Van Wynsberge et al., 2016). For instance, the continental reef type is only behind semi-closed atolls, and have similar median densities of giant clam compared to open atoll (Van Wynsberge et al., 2016). ...
... Their adductor muscle and mantle serve culinary and ornamental purposes, respectively. However, rampant overfishing and habitat degradation have led to a marked decline in the population of giant clams [4][5][6]. Consequently, their trade is now regulated by Appendix II of the United Nations Convention on International Trade in Endangered Species of Wild Fauna and Flora. ...
The habitats of giant clams are undergoing environmental changes, and giant clam populations are declining. The present study was conducted to facilitate clam conservation. We conducted three 18-week trials to investigate the effects of nutrient, temperature, and salinity on the growth performance and survival rates (SRs) of juvenile Tridacna noae, adult Tridacna crocea, and subadult Tridacna derasa, respectively. Regarding nutrient sources, no significant differences were observed in shell length gain, specific growth rate, or SR between clams fed with Chaetoceros muelleri or commercial feed (hw nanotip) and those in a control group (juvenile phototrophs). Regarding temperature, clams cultivated at 27 °C exhibited significantly better growth performance and SR than did those cultivated at 19 °C or 31 °C (p < 0.05). By week 6, all clams in the 19 °C and 31 °C groups had died, indicating that suboptimal growth temperatures have severe adverse effects. Regarding salinity, clams cultivated at 34‰ exhibited significantly higher length gains and specific growth rates than did those cultivated at 20‰ or 25‰ (p < 0.05). SR was not significantly affected by salinity. Understanding how environmental factors affect giant clam populations may help researchers devise effective clam conservation strategies.
... There is no clear explanation for this. Since traded numbers show much fluctuations over the whole period and this turnaround occurred only in the last year of the observation period, it could be the start of a new trend or become succeeded by a reverse change.There are various possible explanations for the decline in the market of wild-sourced clams, one of which is that there could have been a decrease in the densities of natural populations, leading to smaller available stocks for exploitation(Andréfouët et al., 2005;van Wynsberge et al., 2016van Wynsberge et al., , 2017Neo et al., 2018;Ramah et al., 2019). There are various reports on the overexploitation causing strong population declinesMecha and Dolorosa, 2020;Mehrotra et al., 2021) and on the negative effects of elevated sea water Tridacna populations have also been common without human impact and can perhaps be linked to climate change(Liu et al., 2020a). ...
... Sediment samples of sharks (including 124 reads of the critically endangered broadnose wedgefish, Rhynchobatus springeri at 99% and 100% ID of two ASVs) can potentially support seawater eDNA detections by representing ecosystems that have historically supported these populations (Ellegaard et al., 2020). In addition, because our primer was not limited to bony fishes, we were also able to detect 111 ASVs (127, 696 reads) of the small giant clam (Tridacna maxima, 97% ID), a species that has more recently been targeted by fishers in the Indo-Pacific as other giant clam stocks have crashed (Supplementary Table A8, Van Wynsberge et al., 2016). These detections can be further validated for appropriate interpretation through modeling the local biophysical processes that determine the persistence and degradation of eDNA, as well as the lab-based processes that affect amplification efficiencies (Barnes and Turner, 2016;Hansen et al., 2018;Collins et al., 2019;Mathieu et al., 2020). ...
Monitoring coral reef communities remains a scientific cornerstone of marine biodiversity conservation and management. Environmental DNA (eDNA) has recently emerged as a passive detection tool to enumerate organisms in dynamic marine systems. The utility of eDNA to provide meaningful results for coral reef conservation and management in Indonesia, a hyper-diverse and data-limited tropical area, however, remains poorly understood. In this study, we conducted seawater and sediment eDNA surveys in three regions of Indonesia and amplified them using a general metazoan primer. We found that eDNA revealed a diverse array of reef organisms overall (>11,000 amplicon sequence variants, or ASVs), including species of management importance (i.e., sharks and mollusks) that are otherwise missed by conventional surveying methods. Most fish and coral eDNA detections were verified by our concurrent visual surveys of those taxonomic groups, demonstrating the utility of these two methods as complementary approaches for broad-scale reef bioassessment. Almost half of the ASVs, however, were unclassified Eukaryotes. We estimated that with our eDNA protocol, 119–197 water samples and 259–375 sediment samples would be needed to recover the complete suite of operational taxonomic units (a genetic proxy for species) in each region. Despite not reaching the full saturation of potential diversity or taxonomic detection within regions, eDNA sampling revealed community compositions were regionally distinct, even though water and sediment samples differed in community structure and exhibited high heterogeneity. Our precursory examination of a taxonomically-broad eDNA survey in Indonesia highlights the short and long-term utility of the method as a confirmatory and complementary tool for biomonitoring, research, and conservation purposes. Nonetheless, more rigorous sampling, methodological refinements, and database curation are needed for eDNA to reach its full potential in Indonesia.
... There are several studies that have been conducted on the abundance of clams in Indonesia, one study conducted by Othman, Goh & Todd, [5] revealed that habitat loss, pollution, and increased sea surface temperatures are the causes of declining clam populations. Van Wynsberge et al. [6] found that human population is closely related to clam abundance. According to Setiyaningsih [7], clams in Pulau Seribu are under threat of population decline due to the culture and habits of the surrounding community who consume clams. ...
... E < 0.4 : Small population uniformity 0.4 < E < 0.6 : Moderate population uniformity E > 0. 6 : High population uniformity ...
This research aims to find out the biodiversity and distribution patterns of clams and the relationship between clam abundance and coral reef conditions in the Waters of Kayu Angin Bira Island, Kepulauan Seribu. The research was conducted between April and July 2022, with field data collection taking place in September 2022 at four chosen stations. These stations were selected based on variations in water depth and were situated in the South, West, North, and East regions of the waters surrounding Kayu Angin Bira Island. The data collection was conducted using survey methods. Coral reef data collection using LIT (Line Intercept Transect) method and clam observation using belt transect. The results showed that in the waters of Bira Kayu Angin Island, 25 individuals of 2 species of bivalve class were found, namely Tridacna squamosa, Tridacna crocea. The highest relative abundance of clams is found at the eastern station which is 20% and the lowest relative abundance is found at the southern, western and northern stations which is only 8%. Low diversity index of Tridacninae Clams was discovered at the four stations, which ranged from 0.451 - 0.662 and the uniformity index at the four stations ranged from 0.650 - 0.954, indicates high population uniformity. Based on Morisita distribution index, which ranges from 0.4 - 0.74, the spatial distribution of Tridacninae clams could be assigned as uniform. The relationship between clams and coral reefs is 0.7284, shows that clams have a strong relationship with the condition of coral reefs.
... In contrast, T. maxima occurs in more or less high densities in four of the five archipelagos of French Polynesia (it is absent or nearly absent in the Marquesas), which represents the extreme eastern range of this species (Neo et al., 2017). In French Polynesia, T. maxima preferentially occurs in shallow waters of lagoons (but see Van Wynsberge et al., 2016). In several atoll lagoons of the Tuamotu Archipelago, T. maxima grow and form large permanent aggregations of individuals (Gilbert et al., 2005), reaching the highest recorded densities over all of its range (Van Wynsberge et al., 2016). ...
... In French Polynesia, T. maxima preferentially occurs in shallow waters of lagoons (but see Van Wynsberge et al., 2016). In several atoll lagoons of the Tuamotu Archipelago, T. maxima grow and form large permanent aggregations of individuals (Gilbert et al., 2005), reaching the highest recorded densities over all of its range (Van Wynsberge et al., 2016). ...
... Tridacna maxima remains abundant over all of French Polynesia (Gilbert et al., 2006;Van Wynsberge et al., 2013): it is not a species threatened with extinction in any of the French Polynesia islands. Yet its abundance has significantly decreased in the past decades or even recent years in many areas, in particular owing to overfishing in the densely populated areas of the Society Islands (Van Wynsberge et al., 2016), and in some lagoons owing to massively lethal weather warming events (Van Wynsberge & Andréfouët, 2017;Andréfouët et al., 2018). ...
The small giant clam, Tridacna maxima , is distributed from the Red Sea and East African coast to French Polynesia. Across this widespread Indo‐Pacific range, T. maxima shows strong population structure, in agreement with its limited dispersal abilities.
Peripheral populations may have smaller effective population sizes, increasing their vulnerability under any environmental changes. Understanding evolutionary processes at play in such regions located at the edges of T. maxima distribution is a prerequisite in the context of transfers and restocking programmes.
In this study, giant clams were sampled from 14 atolls and islands within four archipelagos in the peripheral region of French Polynesia, in 2001–2002 and/or in 2012–2013, then genotyped at the COI gene and at nine microsatellite loci.
Mitochondrial lineages of T. maxima from French Polynesia diverged from those sampled in Micronesia, Melanesia, the Coral Triangle and the Red Sea by 6.6–7.3%. Within French Polynesia, significant genetic structure was found, indicating restricted gene flow, and it was stable through time. Most of the genetic variation at microsatellite loci was between archipelagos. The most differentiated archipelago was the most geographically isolated (the Austral Islands).
The current patterns of genetic structuring of T. maxima in French Polynesia probably result from long‐term genetic isolation with limited dispersal ability. In addition, these results underlined that sufficiently large populations of T. maxima have persisted in the Central Pacific during the last sea‐level regression.
Strategies to optimize transfers and restocking programmes should be designed to preserve the genetic diversity and structure observed here, to avoid the risks of altering the genetic structure, allele loss and/or introduction of maladapted alleles in the receiving populations.
... Pengunjung juga lebih banyak mengambil jenis kima yang berukuran lebih besar, sehingga populasi T. maxima pada sisi pulau bagian dalam cenderung lebih stabil. Selain itu, jenis T. maxima juga memiliki tingkat resistensi yang lebih tinggi terhadap tekanan karena tingkat reproduksi yang lebih tinggi serta keberadaannya yang lebih dominan pada daerah ekosistem terumbu karang (Van Wynsberge et al., 2016). Kima menjadi salah satu sumber protein yang banyak dimanfaatkan oleh masyarakat pesisir indonesia (Silaban et al., 2022). ...
... Jenis T. maxima merupakan jenis yang kepadatannya lebih besar dibandingkan dua jenis lainnya. Hal ini disebabkan keberadaan kima jenis ini banyak ditemukan pada wilayah yang terdapat ekosistem terumbu karang (Van Wynsberge et al., 2016). Keberadaannya yang merata pada ekosistem terumbu karang juga menjadikannya sebagi biota simbion bagi berbagai ikan karang sebagai tempat berlindung dari pemangsa (Neo et al., 2015). ...
Pulau Gosong merupakan salah satu wilayah perairan yang telah dilindungi oleh pemerintah melalui Surat Keputusan Menteri Kelautan Dan Perikanan Republik Indonesia No.78/KEPMEN-KP/2020. Salah satu potensi perairan yang terdapat di Pulau Gosong adalah habitat populasi berbagai jenis biota kima. Ancaman terhadap populasi kima semakin meningkat akibat pemanfaatan berlebih yang dilakukan oleh manusia. Penelitian ini dilakukan dengan tujuan untuk mengidentifikasi jenis, mengukur kelimpahan dan kepadatan berbagai jenis biota kima di Pulau Gosong. Pengamatan dilakukan pada dua stasiun dengan menggunakan metode belt transect sepanjang 100 meter dengan total lebar pengamatan lima meter. Hasil penelitian menemukan tiga jenis biota kima yang teridentifikasi di perairan Pulau Gosong meliputi ima Raksasa (Tridacna gigas), Kima Kecil (Tridacna maxima) dan Kima Selatan (Tridacna derasa). Kondisi menunjukkan bahwa Pulau Gosong memiliki sekitar 43% kekayaan jenis biota kima yang ada diseluruh Indonesia. Kelimpahan relatif tertinggi ditemukan pada jenis T. maxima dengan nilai 66,67%, sedangkan kelimpahan relatif terendah ditemukan pada jenis T. derasa dengan nilai 6,67%. Kepadatan kima paling tinggi ditemukan pada jenis T. maxima dengan nilai 0,02 ind/m2, sedangkan kepadatan paling rendah ditemukan pada jenis T. derasa dengan nilai 0,002 ind/m2. Kepadatan jenis T. gigas menunjukkan nilai yang sama baik di stasiun 1 maupun stasiun 2 yakni dengan nilai sebesar 0,008 ind/m2. Hal ini menunjukkan adanya keseimbangan populasi jenis T. gigas yang terdapat di Pulau Gosong.
... However, despite CITES regulations, local exploitation bans, and increased mariculture activities, giant clams are still under threat. Global demand of live individuals for ornamental trade, shells for carved artwork as a substitute for ivory, and abductor muscle for consumption has led to overexploitation of giant clams in virtually all populated regions and local extinction in various places (Larson 2016;Van Wynsberge et al. 2016). In the Western Indian Ocean (WIO), a drastic decline in giant clam densities due to anthropisation is reported for Mauritius (Ramah et al. 2019). ...
There are currently 12 recognised extant species of giant clams (Cardiidae: Tridacninae) inhabiting the tropical waters of the Indo-Pacific. Six species have been newly described or rediscovered since 1982, such as the recently resurrected species Tridacna elongatissima in the Western Indian Ocean. In order to investigate the distribution range of this species, 24 specimens have been collected and identified by DNA barcoding. This study provides the first record for T. elongatissima in Tanzania and expands both the northern (Zanzibar, Tanzania) and southern (Ponta de Ouro, Mozambique) ranges of this species.
... Olahan daging kima dapat digunakan sebagai bahan makanan serta hasil lahan cangkang digunakan sebagai bahan bangunan dan kerajinan tangan (Neo & Todd, 2013). Selain itu, kima yang masih hidup juga menjadi salah satu komoditas dalam perdagangan akuarium hias (Van Wynsberge et al., 2016). Tingginya nilai jual dan permintaan pasar dari seluruh penjuru dunia mengakibatkan terjadinya eksploitasi yang berlebihan. ...
ABSTRAK Kima (Giant clam) merupakan kelompok kerang laut yang termasuk da lam anggota F amili C ardiidae dan K elas Bivalvia . Kima merupakan salah satu komoditas perdagangan internasional yang bernilai ekonomis tinggi. Kondisi habitat Kima yang heterogen sangat menarik untuk diteliti, terutama dalam rangka memahami karakteristik habitat dan keanekaragaman spesies kerang kima di zona intertidal P antai B ilik Taman Nasional Baluran. Untuk menentukan karakteristik habitat yang dipilih populasi kerang kima dan keanekaramanan spesies, dilakukan metode road sampling dengan cara ‘tracking’ pada tipe-tipe habitat dan a nalisis karakteristik habitat mengggunakan klasifik a si analisis substrat karang laut. Karakteristik habitat yang paling disukai kerang kima adalah RCK (rocks) dengan prosentase 64.28% dan yang terendah S (sand) dengan prosentase 3.57 %. Keanekaragaman spesies kerang kima di zona intertidal pantai Bilik TNB tergolong rendah, sejumlah 4 spesies yang ditemukan yaitu Tridacna crocea, T. maxima, T. squamosa dan Hippopus hippopus. Nilai kemerataan menunjukkan hasil yang mendekati nol yang berarti ada spesies yang mendominasi dalam komunitas kerang kima yaitu spesies T. crocea yang jumlahnya mencapai 38 individu . Kata Kunci: Kima, Tanjung Bilik , T aman N asional Baluran ABSTRACT Kima (Giant clam) is a group of sea shells that belongs to the cardiidae family and the Bivalvia class. Kima is one of the international trade commodities with high economic value. This heterogeneous habitat condition is interesting to study, especially in order to understand the habitat characteristics and species diversity of clams in the intertidal zone of the Baluran National Park chambers. To determine the characteristics of the habitat selected by the clam shell population and species diversity, a road sampling method was carried out by 'tracking' the habitat types and the Habitat characteristics analysis using coral reef classification. The most preferred habitat characteristics for clams are RCK (rocks) with a percentage of 64.28% and the lowest is S (sand) with a percentage of 3.57%. The diversity of species of clams in the intertidal zone of Bilik TNB beach is low, numbers 4 species were found, namely Tridacna crocea, T. maxima, T. squamosa and Hippopus hippopus. The evenness value shows a result that is close to zero, which means that there are species that dominate in the clam shell community, namely T. crocea, which number reaches 38 individuals. Keywords : Kima , Bilik Capet, Baluran National Park
... In the past decades, giant clam populations had been over-exploited due to high economic demand as a food source and in the ornamental aquarium trade (Van Wynsberge et al., 2015;Mies et al., 2017). Considering the global declination of giant clam species worldwide, it had become a great urgency to protect and conserve these marine bivalves. ...
