Clam Density Research Articles

Will swimming crab change their territoriality when prey density increases?

Territoriality is a common expression of territorial behavior. However, the territorial behavior of the swimming crab, Portunus trituberculatus, is not fully understood. In this experiment, an indoor camera system (an infrared camera, video recorder, monitor, light source, cylindrical experimental aquarium, shade cloth, and shelter) was used to explore the territory size, time allocation, and behavioral changes of the swimming crab. The crab's foraging type was determined according to their behavior under different prey densities. The crab's territorial behavior was evaluated using a “territorial behavior score (calculated according to the total number of territorial behaviors, defense time, the number of bouts, and the winning percentage of the initial crab).” With an in se in clam density, (1) the size of territory occupied by the crab decreased, the success rate of eviction, the proportion, and the number of active fights decreased, the prior residence effect gradually weakened, and the “territorial behavior score” decreased significantly; (2) feeding time and time spent occupying shelter increased, whereas the defense time (animal patrols and expelling of intruders) and free time (animal is motionless) decreased when the intruder was absent. The time occupying the shelter did not change in the intruder's presence. Comparing our results with previous studies, we found that the foraging type of swimming crab is an energy maximizer (spending more time feeding after consuming enough net energy for its activities). Increasing the prey density can weaken the territoriality of swimming crab. To our knowledge, this is the first research on the territorial behavior of the swimming crab. Our results enrich the literature on the territorial behavior of crustaceans and provide a basis for predicting population size changes in Portunus trituberculatus.

Comparative evidence for harvesting-driven enhancement of clam beds in northeastern New Brunswick, Canada

Populations of infaunal clams can be affected by natural and anthropogenic factors. Two such factors include sediment porewater pH and clam harvesting. To date, however, the potential effects of clam harvesting on sediment pH conditions and corresponding clam densities remain understudied. To fill this knowledge gap, we sampled sediment pH conditions and the densities of three clam species (Mya arenaria spat, and all life stages of Macoma balthica and Gemma gemma) in harvested and non-harvested areas at two sites (Miramichi and Point aux Carr) in eastern New Brunswick, Canada. Within sites, sediment pH conditions were higher within harvested areas and correlated with significantly higher clam densities compared to non-harvested areas. Between sites, clam abundances were significantly higher at the site with lower pH conditions, suggesting that reduced clam densities associated with low sediment pH may be restricted to small spatial scales in this region. These results add to a growing body of literature suggesting that, under certain contexts, commercial clam harvesting may enhance habitat suitability and benefit some clam populations. The ways in which commercial clam harvesting affects habitat suitability and clam densities under a wide range of ecological and anthropogenic conditions warrant future investigation.

Drivers of the Abundance of Tridacna spp. Giant Clams in the Red Sea

Giant clams (Subfamily Tridacninae), are important members of Indo-Pacific coral reefs, playing multiple roles in the framework of these communities. Although they are prominent species in Red Sea reefs, data on their distribution and densities in the region are scarce. The present study provides the first large-scale survey of Red Sea Tridacna spp. densities, where we examined a large proportion of the Saudi Arabian Red Sea coast (1,300 km; from 18° to 29°N). Overall, Tridacninae were found at densities of 0.19 ± 0.43 individuals m–2 (±SD). Out of the total 4,002 observed clams, the majority (89%) were Tridacna maxima, with 0.17 ± 0.37 individuals m–2, while only 11% were Tridacna squamosa clams with 0.02 ± 0.07 individuals m–2. We also report on a few (total 6) Tridacna squamosina specimens, found at a single reef. We identified different geographical parameters (i.e., latitude and distance to shore) and local environmental factors (i.e., depth and reef zone) as the main drivers for local Tridacna spp. densities. Our results show that the drivers influencing the densities of Red Sea giant clams are complex due to their co-occurrence and that this complexity might explain the high variation in Tridacninae abundances across the Indo-Pacific, but also within a given reef. We also estimate that giant clam calcification likely contributes to an average of 0.7%, but potentially up to 9%, of the overall mean calcium carbonate budget of Red Sea coral reef communities.

No experimental evidence for vector-free, long-range, upstream dispersal of adult Asian clams [Corbicula fluminea (M\xfcller, 1774)

The Asian clam (Corbicula fluminea) is one of the rapidly spreading, very successful aquatic invasive species, which has become established widely in many parts of the world. Its spread is assumed to be by both passive and active dispersal. However, the importance of active pedal movement in dispersal is hardly known. Since there was no direct evidence of this phenomenon, field observations were combined with laboratory experiments to find out if the clams move upstream actively, and how this is affected by the quality of the substrate, the density of the clams, and the water velocity. Field observations were conducted at a small watercourse with no waterborne transport. Experiments were done in an indoor artificial stream system, where the distances moved by adult clams were measured via digital image analysis. Substrate grain size, starting density of clams, and water velocity significantly affected clam movement. Fine grain sediment and slow flow velocity both facilitated spread, while there was no clear pattern of density-dependent dispersal. Also, we found no clear preference for either upstream or downstream movement. The maximum distance moved in the lab experiments predicts no more than 0.15 km/y active pedal movement in an upstream direction, while our field observations detected a much faster (0.5–11 km/y) upstream movement, which might be explained by passive dispersal, such as via human transport and ecto- or endozoochory. Overall, it seems that active movement of the species cannot read to long-distance migration.

The Spatial Distribution, Growth, and Reproduction of the Bivalve Macoma calcarea (Gmelin, 1791) off the Novaya Zemlya Coast

The population and biological characteristics of the bivalve mollusk Macoma calcarea (Gmelin, 1791) off the Novaya Zemlya Archipelago, eastern Barents Sea, are considered. The biomass of Macoma clams in the study area varied from 3.9 to 350.6 g/m2; the population density varied from 13.3 to 196.6 ind./m2. It was shown that the biomass and population density of clams do not depend on the depth and near-bottom water temperature; the size structures and growth rates were similar at different depths. The life span was found to differ significantly between clams that lived at depths shallower than 100 m (17 years) and deeper (26 years). At depths shallower than 100 m, aggregations of this species consisted mainly of juveniles (up to 4 mm); at the stations with greater depths, both juveniles and individuals with a shell length of 14.9 mm were found in abundance. Individuals of M. calcarea reach sexual maturity at an age of 3–4 yr, with a shell length of over 7.5 mm. At the stations with greater depths, there were significantly more mature clams than immature ones, and more males than females. Three stages of gametogenesis were identified in the examined females. The size of mature, ready to be spawned oocytes was 175 μm.

Population structure of giant clams (tridacnidae) in Aceh Besar district waters

Giant clams have an essential ecological role in the coral reef ecosystem. Given the decreasing number of giant clams in nature, the status of giant clams as protected animals, and there is still little information about giant clams, data or information is needed to make policies regarding giant clam conservation management. This study aimed to determine the population structure of giant clams (Tridacnidae) in the coral reef area of Aceh Besar District. The research was conducted in May 2018, located in Aceh Besar Regency waters with six observation stations. Observation of giant clams is carried out using a visual census technique with the belt transect method. The observations showed that the giant clams found in Aceh Besar waters consisted of 2 species, namely Tridacna maxima and Tridacna crocea. Overall stations, the individual density of giant clams is 0.041 ind. m-2. The diversity index of giant clams shows a value ranging from 0–0.97, classified in the low diversity category. The similarity index value of giant clams is classified into the stressed to stable similarity category with values ranging from 0–0.97. The dominance index value of giant clams is classified in the medium to high dominance category with values ranging from 0.52 to 1. The distribution pattern of the two giant clam species found in the waters of Aceh Besar District has a uniform distribution pattern with values ranging from 0.20–0.29. The overall population structure of Tridacnidae is in unstable condition.

POPULATION STRUCTURE AND REPRODUCTION OF THE RAZOR CLAMS Solen lamarckii (Chenu, 1843) IN THE INTERTIDAL ZONE OF API API VILLAGE WATERS, BENGKALIS REGENCY

Razor clam (Solen lamarckii) is a type of pelecypoda that has high economic value on the Api api village waters, Bengkalis Regency. This research aims to study the population structure and reproduction of razor clam. The study was carried out over 2 month period from September to October 2019 at Api api village waters, Bengkalis Regency. Razor clam samples were collected by using a 1 x 1 m2 frame that laid along transect. There were 5 plots and 5 subplots along the transect as replications. The result showed, the population density of razor clams is 3.12 species/m2 in September and 2.88 species/m2 in October 2019. The distribution pattern of razor clams was uniform. While, the most common size of razor clam is the medium size category (40-60 mm) both in September and in October 2019. The average value of gonado somatic index (GSI) was 2.28-8.60%. Histological analysis indicated that maturity gonad stage of razor clam was commonly found in September is maturity gonad stage I (60%), while in October is stage III (40%) and stage IV(30%).

KARAKTERISTIK HABITAT DAN STRUKTUR POPULASI KERANG BAMBU (Solen lamarckii, Chenu 1984) DI ZONA INTERTIDAL DESA APIAPI KECAMATAN BANDAR LAKSAMANA KABUPATEN BENGKALIS

The study about habitat characteristics and population structure razor clam (Solen lamarckii, Chenu 1984) in intertidal zone Apiapi Village Bandar Laksamana District Bengkalis Regency conducted on January 2020. The purpose of this study was to analyze about habitat characteristics and population structure of razor clam and the correlation between substrate particle size and population density of razor clam. The habitat parameters measured include the physical and chemical parameters of sea waters. Determination of the station using purposive sampling method. Razor clam samples were collected by using a 1 x 1 m2 frame that laid along a transect. There were 4 plots and 3 subplots along the transect as replications. The result showed, the sediment tipe was sandy substrate, organic material was low, total suspended solid was high. Population density of razor clams was 3.3-23.3 Ind/m2. The distribution pattern of razor clams through each plot was uniform. While, the most common size of razor clam 5.04-5.62 cm. The correlation between particle size and population density of razor clam was strong.

Inventarisasi kima (Tridacnidae) di Pulau Batu Bilis, Desa Kelarik Kecamatan Bunguran Utara, Kabupaten Natuna, Kepulauan Riau, Indonesia

Batu Bilis Island Kelarik Village is surrounded by shallow coral reefs with a fairly bright level of water brightness, making it a habitat for important economic biota in the form of clam shells (Tridacnidae). The purpose of this study is to identify the types of clam shells and determine the value of shellfish. Closing data is carried out on 9 (nine) points. Using the Benthos Belt Transect method, with an observation area of 140 m². The results were found 2 (two) types of clams, namely Hole Clams (Tridacna crocea) and Small Clams (Tridacna maxima). The highest density of Hole Clams is at point 9 (nine) with a value of 1.142.9 individual/ha, then the lowest density at point 7 (seven) 142,86 individual/ha. The highest density of Small Clams is at point 7 (seven) with a density value of 928,57 individual/ha and the lowest density at point 8 (eight) with a value of 71,43 individual/ha. The quality of physical-chemical parameters in Batu Bilis waters is still in the normal range for the life of clams shells such as temperature 29,4⁰C, salinity 29,5‰, current speed 0,08 m/s and brightness 100%.

Are Juvenile Manila Clam Ruditapes philippinarum Free from Perkinsus olseni Infection in Korean Waters?

As a suspension feeder, Manila clam Ruditapes philippinarum (A. Adams and Reeve 1850) plays a crucial role in the coastal soft bottom ecosystem in the temperate region, linking the benthic primary production to the upper trophic level. Manila clam density on tidal flats on the west coast of Korea has been declining for the past decades, and infection by the protozoan parasite Perkinsus olseni (Lester and Davis 1981) is one of the major causes for the decline. Recent studies carried out in Japan revealed that P. olseni induces mortalities of the juveniles in their natural habitats, which may lead to the recruitment failure and subsequent decline in the clam population. In this study, we surveyed P. olseni infection in juvenile Manila clam occurring on two tidal flats on the Taean coast. Ray’s fluid thioglycollate medium assay (RFTM) revealed that P. olseni infection was not limited to the adult clams, and the juvenile and small-sized clams are also infected by P. olseni. As young as four-month-old juveniles from Jugyo tidal flat were infected by P. olseni, with the prevalence (i.e., percentage of the infected individuals) of 75.0% and the intensity of 7.77 × 105 cells g−1 wet tissue weight (WT). The adult Manila clams (SL > 30 mm) from Jugyo tidal flat showed a prevalence of 96.0%, and the intensity as 5.80 × 10 cells g−1 WT. The observed infection prevalence and intensity of the juvenile are somewhat comparable to those of the adult clams, suggesting that a high level of P. olseni infection in the juveniles may lead to mortality and a long term decline in the clam population density.

Rapid localized decline of a French Polynesian coral reef following a climatic irregularity

Coral reefs are among the most biologically diverse and complex marine ecosystems on Earth. However, anthropogenic impacts continue to degrade coral reefs worldwide, potentially increasing the ability for localized climatic irregularities or fluctuations to cause rapid changes to habitats over limited spatial scales. Bora-Bora Island was impacted by one such irregularity between 02th and January 05, 2020, with adjacent reefs subjected to a combination of low tides, high temperature and algal bloom. Our monitoring surveys showed that after only four days of these conditions, live coral cover on some Bora-Bora reefs rapidly declined from 80 ± 7% to 20 ± 7%. In addition, the density of fishes and giant clams also decreased (i.e., respectively, from 3.6 to 6.1 individuals per m2 before climatic anomaly to 2.6 and 2.2 individuals after climatic anomaly). This study suggests that, as the mean environmental conditions continue to move towards to abiotic limits on coral reef growth and persistence, even small fluctuations above these limits could have dramatic impacts on the resilience of reef communities.

Habitat Preferences of PokeA (Batissa violacea var. celebensis von Martens, 1897) Basic on Substrat Characterisation in Pohara River Southeast Sulawesi

This research is motivated by the lack of information about the habitat preferences of pokea clams in Pohara River, Southeast Sulawesi. This study aims to determine the density, distribution pattern and habitat preferences of pokea clams in the Pohara River, Southeast Sulawesi. This research was conducted for 6 months (April-September 2011). Sampling of pokea, water quality, and sediment texture was carried out in the Pohara River and analyzed at the FPIK UHO Laboratory. The density and distribution of pokea were calculated using a standard formula and analyzed using Mann Whitney and Chi Square respectively, while the habitat preferences based on different substrate textures were analyzed using Principal Component Analysis (PCA) and Cluster Analysis (CA) in the Multivariate Statistical Package (MVSP). The results showed that the density of pokea clams ranged from 117±96.78-816±594.84 ind/m2 which was distributed in cluster over the entire cross-section of the river. Pokea clams were found in all substrate textures from gravel to clay. The habitat preference of pokea clams indicated by the highest density was found in the clay texture. Pokea clams relatively do not like the habitat of coarse sand and gravel texture which is characterized by pokea population with the lowest density

Distribution and density of Lutraria rhynchaena Jonas, 1844 relate to sediment while reproduction shows multiple peaks per year in Cat Ba-Ha Long Bay, Vietnam.

Lutraria rhynchaena Jonas, 1844 is of great commercial interest, but its reserves have dramatically declined over recent decades. Therefore, there is an urgent need of scientific basis to propose effective fishery management measures and improve artificial aquaculture of the clam. In this study, we investigated the distribution and density of L. rhynchaena, sediment characteristics, and established the clam’s reproductive cycle through monthly observations from August 2017 to July 2018. The study results showed that distribution and density of clams are related to sediment types, and the sediment type of medium sand is likely the best benthic substrate for the clams. The spawning of clams occurred throughout the year with three spawning peaks in January, April and September. For the sustainable management of the clam resource in Cat Ba-Ha Long Bay, the fishery authorities can issue a ban on harvest of the clam in spawning peak months in January, April and September.

Depuration processes affect the Vibrio community in the microbiota of the Manila clam, Ruditapes philippinarum

As filter-feeders, bivalve molluscs accumulate Vibrio into edible tissues. Consequently, an accurate assessment of depuration procedures and the characterization of the persistent Vibrio community in depurated shellfish represent a key issue to guarantee food safety in shellfish products. The present study investigated changes in the natural Vibrio community composition of the Ruditapes philippinarum microbiota with specific focus on human pathogenic species. For this purpose, the study proposed a MLSA-NGS approach (rRNA 16S, recA and pyrH) for the detection and identification of Vibrio species. Clam microbiota were analysed before and after depuration procedures performed in four depuration plants, using culture-dependent and independent approaches. Microbiological counts and NGS data revealed differences in terms of both contamination load and Vibrio community between depuration plants. The novel MLSA-NGS approach allowed for a clear definition of the Vibrio species specific to each depuration plant. Specifically, depurated clam microbiota showed presence of human pathogenic species. Ozone treatments and the density of clams in the depuration tank probably influenced the level of contamination and the Vibrio community composition. The composition of Vibrio community specific to each plant should be carefully evaluated during the risk assessment to guarantee a food-safe shellfish-product for the consumer.

Context-dependency of eelgrass-clam interactions: implications for coastal restoration

Facilitative interactions between co-occurring species sustain diverse communities and constitute a vital functional component of coastal marine ecosystems. In seagrass ecosystems, facilitation ensures the survival and resilience of this important habitat. As seagrass meadows are in decline, innovative restoration strategies incorporating facilitative interactions could open new avenues in marine restoration. Here, we investigated the interactions between eelgrass Zostera marina and the Baltic clam Macoma balthica, and tested whether clams could enhance early survival and biomass increase of transplanted eelgrass shoots in the northern Baltic Sea. We measured eelgrass responses to differing densities of clams, as well as porewater ammonium (NH4+) and phosphate (PO43-) concentrations in field and aquarium experiments. Overall, survival of transplanted plots was high, independent of clam density. Specifically, we found that clams facilitated eelgrass above- and below-ground biomass in low porewater nutrient conditions, potentially through nutrient release, but inhibited growth in high-nutrient conditions, particularly where clams were added at high densities. Our results show the important role of infaunal bivalves for nutrient fluxes within seagrass meadows. Most notably, we highlight the importance of considering and testing context- and density-dependency when studying interspecific interactions, as clams could both benefit and hamper Zostera biomass increase. This becomes particularly crucial when incorporating such interactions in a restoration context.

Are predator-prey model predictions supported by empirical data? Evidence for a storm-driven shift to an alternative stable state in a crab-clam system

A dynamic systems approach can predict steady states in predator-prey interactions, but there are very few examples of predictions from predator-prey models conforming to empirical data. Here, we examined the evidence for the low-density steady state predicted by a Lotka-Volterra model of a crab-clam predator-prey system using data from long-term monitoring, and data from a previously published field survey and field predation experiment. Changepoint analysis of time series data indicate that a shift to low density occurred for the soft-shell clam Mya arenaria in 1972, the year of Tropical Storm Agnes. A possible mechanism for the shift is that Agnes altered predator-prey dynamics between M. arenaria and the blue crab Callinectes sapidus, shifting from a system controlled from the bottom up by prey resources, to a system controlled from the top down by predation pressure on bivalves, which is supported by a correlation analysis of time series data. Predator-prey ordinary differential equation models with these 2 species were analyzed for steady states, and low-density steady states were similar to previously published clam densities and mortality rates, consistent with the idea that C. sapidus is a major driver of M. arenaria population dynamics. Relatively simple models can predict shifts to alternative stable states, as shown by agreement between model predictions (this study) and published field data in this system. The preponderance of multispecies interactions exhibiting nonlinear dynamics indicates that this may be a general phenomenon.

The effects of wet wipe pollution on the Asian clam, Corbicula fluminea (Mollusca: Bivalvia) in the River Thames, London

The aim of the present study was to evaluate “flushable” and “non-flushable” wet wipes as a source of plastic pollution in the River Thames at Hammersmith, London and the impacts they have on the invasive Asian clam, Corbicula fluminea, in this watercourse. Surveys were conducted to assess whether the density of wet wipes along the foreshore upstream of Hammersmith Bridge affected the distribution of C. fluminea. High densities of wet wipes were associated with low numbers of clams and vice versa. The maximum wet wipe density recorded was 143 wipes m−2 and maximum clam density 151 individuals m−2. Clams adjacent to the wet wipe reefs were found to contain synthetic polymers including polypropylene (57%), polyethylene (9%), polyallomer (8%), nylon (8%) and polyester (3%). Some of these polymers may have originated from the wet wipe reefs.

Effects of hard clam (Mercenaria mercenaria) density and bottom shear stress on cohesive sediment erodibility and implications for benthic-pelagic coupling

The interacting effects of little neck hard clam (Mercenaria mercenaria) density and bottom shear stress on cohesive sediment erodibility were investigated. Short-term stepwise erosion experiments in 30 and 40 cm diameter Gust microcosms over a range of 0.0083 to 0.1932 Pa were performed using sequential 20-minute constant shear stress steps while sampling turbidity regularly. In addition, sediment erodibility was monitored in two one-month long ecosystem experiments with tidal resuspension and 0, 10, and 50 hard clams in 1 m3 shear turbulence resuspension mesocosms (STURM) with an initial stepwise erosion experiment (0.313 to 0.444 Pa). In short-term erosion experiments, a low density of hard clams did not significantly affect sediment erodibility, but a high density of hard clams destabilized muddy sediments through significantly decreased critical shear stresses and higher erosion rates, resulting in higher cumulative suspended mass (CSM). In long-term erosion experiments, the sediment stabilized over time between treatments and decreased to a CSM of approximately 60 g m–2 with different densities of hard clams. This was likely due to development of microphytobenthos, mediated by the filter-feeding clams, bottom shear stress and increased light. Bioturbation by a dense bed of hard clams in interaction with infrequent high bottom shear due to storms may increase CSM in the water column, with subsequent direct and indirect effects on the ecosystem. However, more controlled longer-term erosion studies to determine the interacting effects of long-term exposure to high bottom shear stress, benthos, and microphytobenthos on sediment erodibility and benthic-pelagic coupling are needed.

Characteristic changes in the population dynamics of asari (Manila) clam Ruditapes philippinarum in a period of stock decrease on the Banzu intertidal flat, Tokyo Bay

In Tokyo Bay, harvesting of asari (Manila) clam Ruditapes philippinarum has decreased since the early 2000s. In the present study, based on the abundance of sampled clams in four sites from 1998 to 2015 in the Banzu intertidal area, the authors discussed changes in the processes of population dynamics of asari clam which are possibly related to harvest decrease in Tokyo Bay. The findings are summarized as following two points. Firstly, the recent decline in the harvest of asari clams in Tokyo Bay may be caused by the mortality of benthic juveniles. The spatial density of juvenile clams at recruitment showed a varied increase during the study period. In contrast, from the recruitment to adult stages, the mortality coefficient z and von Bertalanffy growth function k consistently increased and decreased, respectively. Moreover, decreasing trends in the spatial density of adult clams were apparent in the concurrent period. Thus, the decrease of adult clams was suggested to be due to poor survival in juvenile clams after recruitment. Secondly, the depletion of the autumn cohort and spatial relocation of the large juveniles were apparent after 2009. The autumn cohort significantly decreased in size-frequency composition, despite the increased abundance and size of juvenile clams at recruitment after 2009. Referring to recent reports, predation by fish may be one of the processes that depleted the abundance of the autumn cohort. Additionally, the density of year-class cohorts increased for 2–4 months from their first appearance to the completion of recruitment, which was likely due to the spatial immigration of large juveniles into the study area. The physical stress of sea water movement caused by increasing strong wind may have encouraged the spatial transport of the juveniles. The depletion of the autumn cohort and spatial immigration of the large juveniles were temporally overwrapped with the period of an outbreak and continuing infestation of the parasitic sea spider Nymphonella tapetis after 2007. This observation can hypothesize that poor burrowing activity due to the parasitic infestation allowed the clams to suffer predation or passive transport. However, above changes in population dynamics after the late 2000s cannot be solely connected to decline of asari harvest, because that decrease in the harvest of asari clams in Tokyo Bay began in the early 2000s; there remain factors other than this one that may have acted on the stock decline after the early 2000s in Tokyo Bay.

Study of giant clam resources for potential marine tourism in Morella Waters, Central Maluku

The giant clam is marine mollusk that lives in the coral reef ecosystem and is protected by CITES Appendix II has the high potential object as marine tourism. This study aimed to analyze the potency of clams, which are part of the coral reef ecosystem for the use of diving and snorkeling ecotourism with clams, as the main object in Morella. The parameters used for the analysis of the clam population are 1) density of clams; 2) diversity index and Tourism Suitability Index. There were five species of clams in Morella, such as Tridacna maxima, T. squamosa, T. gigas, T. crocea, and Hippopus hippopus. The widest distribution was shown by T. maxima. The highest population of clam in Lettang Beach was T. squamosa. The highest percentage of coral reef coverage was found at Lubang Buaya Beach at 81.10%, and the lowest was at Hallasy Beach at 55.53%. The highest diversity of reef fish species was found in Lettang Beach, with 197 species. All areas were suitable to be used as tourist attractions for snorkeling activities of clams and reefs. Whereas, Hallasy Beach, Lubang Buaya Beach, and Lettang Beach were suitable to be used for clam and coral attractive object of diving activities.