Tripneustes gratilla is a ubiquitous sea urchin in tropical seagrass beds, which can occupy various shallow water habitats, from sand flats, coral reefs, and coral rubble areas to seagrass beds and macroalgal flats ((Lawrence & Agatsuma, 2007); (Toha et al., 2017)). T. gratilla is an opportunistic herbivore, consuming its favorite seagrass, macroalgae, and microalgae species, while avoiding calcareous algae due to its tough cell wall ((Lawrence & Agatsuma, 2007); (Loma T et al., 2002)).

In Southeast Asia (the Philippines, Malaysia, Vietnam, and Indonesia), the locals harvest and consume Tripneustes gratilla roe as a local delicacy ((Regalado et al., 2010); (Rahim & Nurhasan, 2016); (Hoa et al., 2019); (Satyawan, 2014)). The people in East Lombok have a tradition of harvesting biota from seagrass beds, including sea urchin T. gratilla, during low tide events (Satyawan, 2014). Overharvesting, especially in seagrass beds close to local villagers’ residences, resulted in reduced sea urchin density and small test-diameter size (Nane & Paramata, 2020). This research aimed to record the diversity, morphometry, abundance, and habitat type of sea urchins in North Lombok coastal areas and record the gleaning activity conducted by local villagers in sea urchin habitats. This research also indicated overharvesting by local villagers of North Lombok. In addition, this study provided valuable baseline information for monitoring the sea urchin population in North Lombok.

A total of 5 sea urchin species were recorded from seagrass beds of Kombal Bay, Pemenang Subdistrict (Table 1).

T. gratilla and Pseudoboletia maculata were included in family Toxopneustidae, while Salmacis bicolor and S. sphaeroides were included in the family Temnopleuridae, and Maretia planulata were included in the family Maretiidae (Figure 3).

T. gratilla was the most abundant species in 2023, with an absolute abundance of 0.24 - 0.30 ind./m2 and a relative abundance of 95.6 - 100%. The absolute abundance in this study is higher compared to the absolute abundance recorded in Eastern Lombok, Indonesia (0.01 - 0.04 ind./ m2) and Maluku, Indonesia (0.008 ind./m2) (Satyawan, 2014); (Uneputty et al., 2017). However, the absolute abundance recorded in this study is lower compared to the absolute abundance

recorded in South-Eastern Sulawesi, Indonesia (2.7 - 10.0 ind./m2) (Nane & Paramata, 2020). The relative abundance obtained in this study is higher than that recorded in Borneo, Malaysia (0.34 - 2.51%) (Rahim & Nurhasan, 2016). In regard to abundance, T. gratilla dominated the sea urchin assemblage in the seagrass beds of Teluk Kombal. Seagrass beds provide microhabitats for T. gratilla to graze and hide from predators (, 2020).

In 2024, the absolute abundance of T. gratilla dropped to 0.01 ind./m2 ( Table 1). Only 1 or 2 sea urchins were recorded in a 100 m2 area of seagrass beds between May 2024 and July 2024. The diversity of sea urchin species also decreased from 4 species in 2023 to only 2 species in 2024. In the absence of P. maculata, S. bicolor, and S. sphaeroides and the abrupt decrease of T. gratilla abundance, the abundance of sand dollar M. planulata increased rapidly. The inferior sand dollar now thrives on the scarcely populated seagrass meadow. In the absence of dominant sea urchin species, inferior species can occupy territories outside of their original niche (Steneck, 2013).

Mean weight, mean test diameter, and mean test height were not significantly different (P > 0.05) when sampling was conducted with the belt transect method. In contrast, sampling with the wandering transect method showed a significant difference (P < 0.05) in all morphometric parameters (Table 2 Morphometric parameters of T. gratilla collected using belt transect and wandering transect methods).

Each survey method has its advantages and drawbacks. The belt transect method provided absolute abundance data but was time-consuming, requiring transects and collecting fewer samples. Wandering transects collected more samples, surveyed vast areas in less time, and required no transects but needed more absolute abundance data and may have overlooked smaller sea urchins.

From August to October 2023, the mean weight, mean test diameter, and mean test height increased significantly, from 34.14 to 49.60 g, from 42.76 to 48.58 mm, and from 24.57 to 27.52 mm, respectively. However, the total sea urchins collected in October 2023 was nearly three times smaller compared to the August 2023 data.

Surveys conducted in May, June, and July 2024 recorded sea urchins with bigger mean weight, mean test diameter, and mean test height compared to the surveys conducted in August, September, and October 2023. However, the total number of

T. gratilla in each survey conducted in 2024 was extremely low compared to the previous year. The considerable weight and size differences can be attributed to seasonal variation (Juinio-Menez et al., 2008); (Satyawan, 2014) or intraspecific competition (Narvaez et al., 2020). The location of sea urchins in seagrass meadows is also a contributing factor. Compared to the more accessible and highly exploited area, invertebrates, including T. gratilla, were more prevalent in the inaccessible or remote seagrass meadows (Nordlund et al., 2010). Based on personal observation, seagrass meadows fringes areas were often overlooked by local villagers, and the majority of sea urchin was found in the area.

Morphometric data are an essential tool in assessing sea urchin population health and sustainability. Food availability (Smith & Garcia, 2021) grazing zones, and domestic pollution (Caill-Milly et al., 2020) affected sea urchin morphometrics. Likewise, sea urchin morphometric data and abundance may be indicative of overharvesting (Tamti et al., 2021) or underexploited (Guinda et al., 2016).

The shift of relative abundance in the test diameter class highlighted the decrease of weight and size. In August 2023, the 45.0 - 49.9 mm test diameter class had the highest relative abundance compared to other classes (Figure 4), but in September 2023, the highest relative abundance shifted to the 35.0 - 39.9 mm test diameter class, two size classes smaller. Local villagers avoided small sea urchins because of the limited amount of roe. The mean test diameter size harvested by local people in September 2023 was 52.08 ± 1.48 mm, while the mean test diameter size ranged from 48.2 - 55.9

mm. There were reductions in the frequency of size classes 45.0-49.9, 50.0-54.9, and 55.0-59.9 by

40.7%, 56.2%, and 100%, respectively (Figure 4).

The size classes were within the range of sea urchin size that local villagers catch (personal observation; Satyawan 2012). The bigger diameter class experienced a greater reduction in frequency. During two sampling days, at least 2 local people harvested T. gratilla. Each person collected 100 - 110 sea urchins, mostly T. gratilla. Two size classes that contained more subjects in September 2023 disappeared in 2024. Only two size classes, each containing only one subject, were recorded in July 2024. The disappearance could be due to death of age or ecological factors.

In the wild, T. gratilla life expectancy was estimated to be between one and two years (Tanita et al., 2023). Overfishing resulted in the absence of larger size classes in Sulawesi (Nane & Paramata, 2020). In East Lombok, T gratilla reached sexual

maturation after 1.2 years or after reaching test diameter size of 58.2 mm (Satyawan, 2014). There were only 2 sea urchins that reached the sexual maturation size in 2024.

Harvesting sea urchins from the wild population usually target subjects with larger test sizes due to higher roe yield. Harvesting activity resulted in the change of size-frequency distribution and the total number of subjects compared to the undisturbed population (, 2013).

Additional surveys were conducted from May 2024 to July 2024 in Kombal Bay and other selected locations to compare the T. gratilla population status in North Lombok and to observe gleaning activities conducted by local villagers. In general, T. gratilla abundance in each location was extremely low compared to that in Maluku (Uneputty et al., 2017) and in the Philippines (Juinio-Menez et al., 2008).

In North Lombok, the highest T. gratilla abundance was recorded in the dense seagrass meadow of Sira Beach, Tanjung, and in the coral reefs of Karakas Beach, Gangga, while the lowest abundance was recorded in Kecinan Beach, Mentigi Beach, and Medana Bay ( Table 3).

The total area, habitat type, and substrate type of Kombal Bay, Sira Beach, and Medana Bay were roughly similar. Kombal Bay had the lowest seagrass cover (47.0%) compared to that in Medana Bay (75.0%) and Sira Beach (80.9%) based on quadrat transect. The low abundance of sea urchins in Sira Beach, Kombal Bay, and Medana Bay was concerning. In Pacitan Beach, East Java, T. gratilla was ubiquitous in seagrass meadows with an absolute abundance of 0.07 ind/ m2, despite moderate seagrass percentage coverage of 31.44% (Muzaki et al., 2019).

Gleaning is a common activity conducted by local villagers during the low tide period, especially in the villages close to seagrass meadows

and shallow coral reefs. The duration of gleaning activity was affected by several factors. Gleaning activity usually lasted 1 - 2 hours and finished after the exposed seagrass meadows were inundated or before sunset (personal observation).

In this study, we observed that Medana Bay was the most favorite gleaning location, followed by Kombal Bay and Sira Beach. Most of the gleaner was adult female, except in Kombal Bay and Kecinan Beach. The majority of gleaners collected gastropods, while adult females also collected Gracilaria sp. as a secondary catch (Table 4). The main purpose for gleaning was collecting food material for home consumption.

Economic issues could be one of the reasons that local villagers conducted gleaning. As much as 27% of North Lombok people were categorized as poor and earned a monthly income of IDR 478,906 (Muzaki et al., 2019). Gleaning can have negative impacts on seagrass meadows. Seagrass meadows are preferred by gleaners due to higher catch rates compared to the coral reefs, mangrove, and tidal flats. (Aldea, 2023). However, a high number of gleaners and an increased human population can cause overharvesting or a decrease in the abundance of targeted invertebrates (Nordlund et al., 2010); (Stiepani et al., 2023).

From 7 locations, we found 11 gleaners that collected sea urchins as either a primary or secondary catch. In Pandanan Beach, 5 adult females collected T. gratilla as a secondary catch with each person collected an average of 5 sea urchins. From interviews (n = 2), the gleaners collected T. gratilla to make vegetable side dishes ( Figure 5).

In Sira beach, a married couple collected 91 sea urchins, while in Medana Bay, a team of two married couples collected 116 sea urchins during one gleaning activity. The husbands used snorkeling equipment to search and collect sea urchins from the reef crest and fore reef zone. The wives received the catch, cracked open sea urchins in half, and retrieved the roe. Sea urchin roe was placed in plastic bottle, and depending on the catch, can either be used for home consumption or be sold in local market (Figure 5).

A 500-mL-plastic bottle filled with sea urchin roe was offered between IDR 20,000 to IDR 30,000. In Sira Beach, the catch consisted solely of T. gratilla, while in Medana Bay, it mainly consisted of T. gratilla with several Toxopneustes pileolus and Pseudoboletia maculata.

In 2023, we recorded 2 gleaners in Kombal Bay who collected T. gratilla as their primary catch. However, in 2024, in the same location, we hardly encountered gleaners that collected sea urchins. Interviews with gleaners revealed that the number of sea urchins was too small to be collected and used for consumption.

In Gangga Subdistrict, local villagers only collected gastropods and avoided sea urchins. Based on interviews with local villagers of Karakas Beach, they have no tradition of using sea urchins as food materials. Local villagers also revealed that only outsiders from the Pemenang Subdistrict and Tanjung Subdistrict collected sea urchins during low tide.

The majority of gleaners conducted gleaning activity every day, approximately 2 to 3 days, during spring low tide or when seagrass meadows were completely exposed (personal observation). Apparently, harvesting sea urchins was affected by local tradition and local wisdom.

Gleaning, especially carried out by adult females or housewives, can support families by providing protein and food security. Most of the time, gleaning requires little to no equipment (Pike et al., 2024)and can be done by young child (Furkon et al. 2020) . However, gleaning, for trading, without supervision and regulation resulted in the decline of target species (Nordlund et al., 2010); (Satyawan, 2014), and habitat destruction by trample (Furkon et al. 2020) . The continued increase in the number of gleaners further exacerbated the problem (Nordlund et al., 2010). Interviews with gleaners, especially older villagers, revealed the decline of catch and disappearance of certain target species (Nordlund et al., 2010). Interviews with gleaners in Kombal Bay (n = 5) also revealed similar conditions.

Several management methods, such as mariculture and restocking (Juinio-Menez et al., 2008), have proven to be successful in resolving the problem that arises with sea urchin T. gratilla gleaning and overharvesting. Furthermore, identification of spawning sites, establishing minimum catch size, and catch prohibition at certain sites had resulted in higher population density. Mariculture in sea cages, rather than larval release restocking, was cost-effective and feasible for stock enhancement in developing countries (Juinio-Menez et al., 2008). Regulation of minimum harvest size, marine sanctuary enforcement, and grow-out of hatchery produced juvenile or wild population in sea cages has proven to be successful in restoring and maintaining sea urchin population in the Philippines (Juinio-Menez et al., 2008). Temporal harvest prohibition during the spawning period could also be established to guarantee natural spawning and breeding (Guinda et al., 2016).

Overharvesting, excluding grazers, such as sea urchins, can increase macroalgal cover and alteration of the macroalgal community (Kriegisch et al., 2020)or habitat damage due to trampling of marine biota living in seagrass meadows (Nordlund et al., 2010). Due to its ecological role, the decrease or increase of sea urchin biomass can affect the balance of trophic levels in the seagrass ecosystem (Clores, 2023), change community structure (Steneck, 2013), and cause overgrazing of seagrass beds (Moreira-Saporiti et al., 2023).

The low absolute abundance of T. gratilla and the decline of sea urchin species diversity in North Lombok prospectively indicated overharvesting. The number of gleaners and the gleaning activity conducted by local villagers prospectively harm seagrass meadows, especially on T. gratilla abundance. A study on diversity, abundance, and

morphometry can provide a base for characterizing sea urchin population and provide a strong baseline to design and implement management policy. Moreover, regular monitoring can be used to obtain the current status of the sea urchin population and check the progress of its management policies.