Several sea cucumber species (Echinodermata: Holothuroidea) are fished, mostly for export of the dried product for Oriental consumers. Previous studies had analysed the historical trends at the world-scale until 2014. In the Western Indian Ocean (WIO) holothurian fisheries have a long history and several programmes have tried to ameliorate their management. Information has been recently gathered through a questionnaire and access to the most recent, yet unpublished available data (2015 to 2021) from different countries, through the evaluation of catches and/or processed product, present management systems, the imports of beche de mer and other products from Indian Ocean (IO) countries into the major market hub of Hong Kong SAR, and the Food and Agricuture Organisation (FAO) yearly statistics. The results are first presented for WIO countries, highlighting recent improvements in management. Imports from 16 WIO countries into the Hong Kong market (2017-2020 data) indicate the importance of the hub. The FAO world statistics are used to present the changes for the last few years, concentrating on the WIO countries. The recent trends show that demand for holothurians is still very high. Inconsistencies in the unit used in the reported statistics (fresh or dry weight) exist, and this needs to be addressed. The national data should be collected at the species level, to be able to follow the changes and the stock status. A regional approach is needed to encourage use of comparable management tools and follow future trends.

This datasheet on Paracentrotus lividus covers Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Biology & Ecology, Environmental Requirements, Impacts, Uses, Management, Economics, Further Information.

Sea cucumbers in Malaysia have been overexploited for decades, and their stock status in both Peninsular Malaysia and Sabah has dropped to an extreme low, resulting in direct impacts on both coastal communities and marine ecosystems. As a result, the Malaysian government is now looking for alternatives such as fisheries management, conservation and aquaculture to manage the depleting wild stocks. This project is a product of fruitful collaboration between the Malaysian government and an Australian-based private company. Since its inception in July 2014, a hatchery, nursery and broodstock rearing facility has been set up. The first spawning trials were done in February 2015 followed by nine other successful spawning events over a period of nine months. Overall, the spawning success rate was about 60% and the fertilisation rate was 85%. Broodstock are now being conditioned in tanks, with some male and female individuals kept separately. Spawning events produced around 4,300,000 larvae with a survival rate of over 30% during the larval stage. Settlement occurred at day 12 after fertilisation, and about 30,000 juveniles (3–5 mm long) have been produced so far. at the commercial level. A survey undertaken in 2012 by a local marketing company revealed at least 13 registered Malaysian companies claiming to be involved in research and development activities to develop derivative products from sea cucumbers, mainly species in the genera Stichopus (BioSys Consulting Pty Ltd 2012; Purcell et al. 2014). The Malaysian government is now looking for alternatives such as fisheries management, conservation and aquaculture to manage the depleting wild stocks. This project is a product of fruitful collaboration between the Malaysian Department of Fisheries (DOF), AADCo Projects Malaysia Sdn Bhd6 (spinoff from research conducted by an Australian-based company, Asia Aquaculture Development Co. Pty Ltd) and a local engineering company (Sesaga Engineering Snd Bhd). The project, led by the spin-off company, aimed at developing and commercialising a sea cucumber aquaculture system for producing premium quality trepang (beche-de-mer). This project is developed under the business incubator programme of the Fisheries Research Institute (FRI), Pulau Sayak, Kedah, Malaysia. Our aim within the next three years is to implement a commercially viable sea cucumber aquaculture facility that will: • allow a continuous production of good quality trepang; 1 Asia Aquaculture Development Company Pty Ltd, Suite 4.1/105 Kippax street, Surry Hills, 2010 NSW, Australia 2 AADCo Projects Malaysia Sdn Bhd, 2980-02 Kompleks Chai Leng, Jalan Baru 13700, Prai, Pulau Pinang, Malaysia 3 Sesaga Engineering Sdn Bhd, 2980-02 Kompleks Chai Leng, Jalan Baru, 13700, Prai, Pulau Pinang, Malaysia 4 Fisheries Research Institute Langkawi, Pejabat Perikanan Daerah Langkawi,Bukit Malut, 07000 Langkawi, Kedah, Malaysia 5 Fisheries Research Institute Pulau Sayak, Kampung Pulau Sayak, 08500 Kota Kuala Muda, Kedah, Malaysia 6 Sdn Bhd is an abbreviation for sendirian berhad, a Malaysian term meaning “private limited”. * Author for correspondence: dev@aadcoprojects.com 68 SPC Beche-de-mer Information Bulletin #36 – March 2016 • allow a better quality control on final products; • achieve higher production rates; and • supply the increasing worldwide demand with a labeled premium quality product. Since its inception in July 2014, a hatchery, nursery and broodstock rearing facility has been set up. The first spawning trials were conducted in February 2015 and were followed by several other successful spawning events over a period of nine months. An overview of the project’s achievements thus far is described in the following sections.

The use of visual and chemical cues in host detection is regarded as important but relatively unknown for many symbionts. The small circumtropical caridean shrimp Gnathophylloides mineri forms a close symbiotic association with sea urchins, particularly Tripneustes gratilla, in many parts of the world. G. mineri is known to occur in temperate eastern Australia but the breadth of host use and selection of hosts amongst different species of sea urchins is relatively unknown. The abundance of G. mineri on three co-occurring species of sea urchins, T. gratilla, Heliocidaris tuberculata and Pseudoboletia indiana were measured in eastern Australia. These species of sea urchins were chosen because of either a known prior association with this shrimp elsewhere in the world, or due to their abundance in the area in temperate Australia where the shrimp occurs. Field collections showed that the association between shrimp and sea urchin appears extremely host-specific, with G. mineri only observed on T. gratilla, at an average density of two shrimp per sea urchin. Moreover, the majority of symbionts occurred on the underside (oral region) of T. gratilla. A visual laboratory experiment showed that G. mineri would actively move towards T. gratilla in preference to the other potential host species in the absence of chemical signals. Using a Y-maze, we tested the reaction of G. mineri to the absence of visual signals but the presence of chemical signals originating from their host, and from other species of potential host sea urchins. Seawater alone was used as a negative control. We demonstrated that G. mineri could detect T. gratilla from a distance, the same host that the shrimp are associated with in the field, using visual and chemical cues. Moreover, G. mineri react quickly to visual and chemical host signals by moving towards T. gratilla in preference to other species of sea urchins or in the absence of a signal. The relative importance of visual versus chemical cues is, however, unknown.

Lipid and protein biochemistry of eggs (84 μm in diameter), embryos and early larvae of the tropical echinoid Tripneustes gratilla (Linnaeus 1758) were quantified to determine how maternal provisions are used to fuel development of the echinopluteus. The eggs contained a mean of 30.82 ng lipid and 87.32 ng protein. Energetic lipids were the major lipid component (55.52% of total lipid) with the major class being triglyceride (TG: mean 15.9 ng, 51.58% of total). Structural lipid was dominated by phospholipid (PL: mean 11.18 ng, 36.26% of total). Early embryogenesis was not a major drain on egg energetic lipid and protein. Development of the functional feeding larva used ca. 50% of initial egg energetic lipid and most of this was TG. Maternal TG was still present in the 8-day echinoplutei and it was estimated that this energetic lipid would be depleted in unfed larvae by day 10. There was no change in PL. In a separate experiment lipid biochemistry of rudiment stage larvae and early developing juveniles were quantified to determine how lipids are used during metamorphosis. Fed larvae accumulated lipid (mean 275.49 ng) with TG and PL being the major energetic and structural lipids, respectively. Larval lipid stores were not appreciably depleted by metamorphosis and so were available for the early benthic stage juvenile. Juveniles started their benthic existence with 314 ng total lipid (TG: mean 46.84 ng, 14.9% of total, PL: mean 137.51 ng, 43.67% of total). Nile Red histochemistry and histology showed that the stomach serves as a nutrient storage organ and, that lipid stores accrued by larvae sustain developing juveniles for up to 4 days post settlement. Triglyceride supported both non-feeding stages of development and the prefeeding larval and perimetamorphic benthic stage. In this first study of lipid stores in settlement stage echinoderm larvae, we show that T. gratilla larvae sequester the same major energetic lipid (TG) to support the early juvenile that the female parent provided them to fuel early development.

The reproductive cycle of the edible echinoid Tripneustes gratilla(Linneaus 1758) was investigated in a population located in the southwest coast of Madagascar (Toliara). The reproductive cycle was followed for two consecutive years (October 1999 to October 2001) and characterised by means of gonad and maturity indices. T. gratilla has an annual reproductive cycle mediated by seawater temperature, day length and feeding activity. The histology of the gonads revealed six different maturity stages grouped in three main reproductive phases: growing and maturing, spawning, and spent and recovering. Reproduction is seasonal. Growing and maturing stages occurred from late summer to early winter correlating with decreasing temperatures and day length. Spawning occurred during mid and later winter, when temperatures and day lengths were lowest. Spent and recovering urchins were observed from late summer to early winter. Besides, the reproductive cycle was also influenced by food quantity in the gut, the repletion index was higher after spawning and gametogenesis started when sufficient amount of nutrient reserves accumulated in gut tissues and nutritive phagocytes of the gonads. This study reveals that the maturity index, based on histological analysis of gonads, is more reliable than gonad index in characterising the reproductive cycle of echinoids. In view of fishery management, we recommend harvest of T. gratilla from November to February, when individuals are in the pre-gametogenic stages. Keywords: echinoid, reproductive cycle, maturity index, tripneustes gratilla, abiotic factors West Indian Ocean Journal of Marine Science Vol. 4 (1) 2005: pp. 47-60

The abundance of echinoderm larvae, in particular sea cucumber larvae, was assessed in the lagoon of To- liara Great Reef in southwest Madagascar from December 2000 to May 2002. More than 9000 echinoderm larvae were collected, 33% of which came from sea cucumbers. Mean larval density varied greatly de- pending on the season. Sea cucumber larvae were most abundant during the hot season (November to April) with an average of 77 larvae per 350 m 3 as compared to 1 larva per 350 m 3 during the cool season (May to October). Sea cucumber larvae were found in large numbers at the time temperatures dropped, ac- counting for 50% of the total number of echinoderm larvae observed. Sea cucumber larvae were not found in the plankton from June to October. Three different families of sea cucumbers were observed: Holothuri- idae, Stichopodidae and Synaptidae. Holothuriidae were the most numerous, accounting for 86% of all sea cucumber larvae collected.

Summary The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.

Richard Rasolofonirina, Devarajen Vaïtilingon, Igor Eeckhaut and Michel Jangoux Institut Halieutique et des Sciences Marines, Université de Toliara, BP 141, Toliara 601, Madagascar; Laboratoire de Biologie Marine (CP 160/15), Université Libre de Bruxelles, 50 Av. F. D. Roosevelt, B-1050 Bruxelles, Belgique; Laboratoire de Biologie Marine, Université de Mons-Hainaut, 20 Place du Parc, 7000 Mons, Belgique.

The symbiotic interaction, population and infestation dynamics of the muricid Vexilla vexillum (Gmelin, 1791) on 2 echinoid species, Tripneustes gratilla (Linnaeus, 1785) and Echinometra mathaei (Blainville, 1825), was investigated on the barrier reef off Toliara (Madagascar). V. vexillum is an ectoparasitic muricid which was exclusively found in association with sea urchins, on which it moves freely and browses over the integument. Host recovery from damage caused by muricid grazing was dependent on lesion size. Small lesions regenerated while larger ones were subjected to secondary infections, which led to host death. A 27 mo survey (2000 to 2003) of the muricid's population dynamics revealed annual recruitment episodes during the mid-summer season (December to January). Patterns of recruitment peaks were apparently linked to its reproductive cycle. Demographic parameters including growth and mortality rates of the muricid were estimated from analysis of size-frequency distributions. Growth was described by the von Bertalanffy function. The model predicts that V. vexillum is a fast-growing species in which asymptotic shell length (L infinity = 1.024 cm) is reached 6 to 7 mo after recruitment. The growth rate constant K, and shell length at settlement L0, were estimated from the model. Estimated mortality rate was 55% yr(-1); V. vexillum has a short lifespan. The observed high growth rate together with the high mortality rate suggest that V. vexillum is a semelparous species. A field survey of the infestation dynamics of V. vexillum was performed during 3 consecutive years, with seasonal variation in parasite prevalence on both echinoid host species. Although both T. gratilla and E. mathaei were infested, a preference towards T. gratilla was noted. This was attributed to T. gratilla's test morphology (which allows better accessibility for grazing), to the muricid's higher recognition capacity of T. gratilla (as determined by olfactory experiments) and to the high recruitment predictability of that particular host. This study provides novel information on the biology of V. vexillum, an echinoid epidermal grazer, and its relationship with 2 ecologically and economically important echinoid species.

The feeding biology of the echinoid Tripneustes gratilla from a sea-grass bed off Toliara, on the south-west coast of Madagascar, was investigated during the summer and winter seasons. Repletion indices of the gut of T. gratilla varied seasonally, in such a way that higher amounts of food occurred in the gut in winter than in other seasons. Conversely, a more detailed analysis of one summer and one winter sample of the gut tissue dry weights revealed higher weights in summer (February) than in winter (August). This was interpreted as a varying capability of nutrient storage and closely related to the feeding activity of the echinoid. This inverse relationship between feeding activity and nutrient storage was suggested to be dependent on gonadal growth. Indeed, higher food consumption was observed during the post-spawning period (August), that is, when most of the energy accumulated was used up for gonadal growth. Low feeding activity occurred when a sufficient amount of energy was accumulated in gut tissues (February), the time corresponding to the initiation of gonadal growth. Investigations on the feeding habits, using Ivlev's electivity index, revealed preferential feeding of T. gratilla on Syringodium isoetifolium, the dominant seagrass species found in the gut. This was partly related to the higher availability of that particular seagrass species in the field. However, its soft and terete leaf blade's morphology also makes it easier to manipulate and ingest. Studies on the feeding behaviour indicated the presence of a diel feeding cycle in T. gratilla individuals in both summer and winter seasons. Yet, its pattern varied between the two studied months (one summer and one winter) as the cycle was less contrasted during period of active feeding, i.e. in winter compared to summer. This study provides novel information on how intrinsic factors, such as physiological state, can govern the feeding activity of T. gratilla living in a seagrass habitat.

Effect of delayed metamorphosis and food ration on late (competent) larvae and postlarvae of Paracentrotus lividus were investigated. Metamorphosis of competent larvae was either not delayed or delayed from 1 up to 4 days. Larvae were starved or submitted to two different food rations of the algal species Phaeodactylum tricornutum. Larvae during the prolonged competence period and the resulting postlarvae were characterised by: (1) the size of the larval body, (2) the size of the rudiment, (3) the rate of metamorphosis, (4) the size of postlarvae 24 h after metamorphosis, (5) the rate of opening of mouth and anus, (6) the rate of survival, and (7) the growth rate of early postmetamorphic individuals. Both the width of the larval body and the diameter of the echinus rudiment grew in competent larvae that were fed. Unfed larvae did not grow. There was no significant difference in growth between the two food rations. The rate of metamorphosis was higher with larvae that metamorphosed soon after they became competent. Lower capacity of larvae to metamorphose during the delay period was associated with treatments yielding a greater larval width and rudiment diameter during the same period. Postlarval development was affected by a delayed metamorphosis treatment inflicted on competent larvae before metamorphosis. Acquisition of exotrophy happened earlier in postlarvae issued from prolonged competent larvae whatever the larval food rations. The delay treatment negatively affected the development of the digestive tract though it positively affected the growth of early postmetamorphic individuals during the first 6 days following metamorphosis. However, selective mortality occurred afterwards as bigger individuals died preferentially.