The mandarinfish Synchiropus splendidus

Extremely limited scientific information, particularly on its biology and fishery, is available for the small, benthic dragonet of the Western Pacific. All individuals traded for the aquarium industry are taken from the wild and the impact of heavy collection (21,458 individuals based on importers' data or 11,168 individuals based on exporters' data in GMAD, traded within the EU only) on fish populations is unknown. It is subject to a sex-selective fishery (up to 70 per cent of fish caught are male) as larger males are most attractive to hobbyists. This has the potential to disrupt exploited populations, both by direct removals and through the indirect effects of removing larger adult males in a mating system where females prefer to spawn with large males.

In the Philippines, Batasan Island fishers heavily targeted mandarinfish between 1987 and 1995. In 1998, average size was recorded at 30 mm total length compared with 60 mm in the 1980s, and reduced numbers were recorded at capture sites. After the mid-1990s, prices fetched by mandarinfish on the aquarium market dropped and the fishery declined. Though species size has recovered somewhat since 1995, abundances are still low - 1,000 fish in three hours of fishing when fish were common, versus 23 fish in two hours in 2001.

In addition to being vulnerable to collection in the wild, this species is difficult to maintain in captivity as it needs to be provided with large amounts of live prey and must be kept in a

well established aquarium with live substrate and plenty of hiding places131.

It is recommended that continuous efforts be made to rear this species in captivity to lessen sex-selective pressure on wild populations. However, due to its aquarium 'unsuitability' (see below, p 43) overall imports of this species should be closely monitored and restricted. Individual specimens should only be considered for sale to experienced aquarists.

Source: Sadovy170

□ the fact that very little is known about existing populations

□ the degraded and deteriorating state of its habitats, mainly due to destructive fishing practices159, and

□ its popularity amongst hobbyists.

A recent study showed that, despite the use of nondestructive fishing methods, the fishery had a negative effect on fish density when sites with high fishing pressure were compared to sites with low fishing levels155. Fishing also had a significant effect on group size (halving of average group size where sites with high and low fishing pressure were compared), which may lead to strong negative impacts on individual fitness in the future (referred to as the Allee effect in the scientific literature)155, 160, 161.

As a precautionary measure the species has been informally proposed for listing on the IUCN Red List of Threatened Species as 'Critically Endangered'157. Should such a listing be made official it would merely draw attention to the threats facing this species without imposing any trade restrictions.

Soon after the Banggai cardinalfish appeared in the aquarium trade, a breeding programme was developed at the New Jersey State Aquarium162. As this fish can be reared through its entire life cycle in captivity162, it is strongly recommended that efforts be developed to raise this species in captivity and in the field (preferably in Indonesia to avoid removing livelihoods from local communities). This would reduce the need to capture wild specimens to supply the trade. It is further recommended that a trade monitoring system be established through direct collaboration with aquarium fish exporters. Targeting and inputting trade volumes of the Banggai cardinalfish into GMAD could help spearhead such a monitoring initiative and allow better estimates of traded numbers to be derived. Improvements in the sustainability of the current trade through directed training programmes on holding, packing and shipping, to reduce mortality rates of the species, are also recommended75. The development of environmental education material and programmes to promote public awareness are strongly encouraged and the potential implementation of marine protected areas should be investigated75.

Hippocampus spp.

Seahorses are distinctive, bony fishes, which belong to the family Syngnathidae, a family that also includes seadragons, pipefishes and pipehorses. All seahorses are included in one genus, Hippocampus. There are approximately 40 recognized species of seahorse, with a few more likely to be described in the future163. New species of seahorses recently described include Hippocampus denise6 and H. queenslandicus'bk.

Seahorses have a global distribution, with the highest diversity occurring in the Indo-Pacific. They typically inhabit marine or brackish water and occur at depths of 1-15 m, among seagrasses, kelp beds, algal and rocky reefs, mangrove prop roots and coral reefs, with a few species preferring open sand or muddy bottoms165. Very little is known about the basic life history parameters of most seahorse species. For species where data are available individuals mature between the age of six and twelve months166. In all species of seahorses it is the male who becomes pregnant and broods the developing embryos for ten days to six weeks depending on species and water temperature. Seahorses form faithful long-term pair bonds and a male will mate exclusively with a female partner. Once the young are born, they are fully independent and receive no care from either parent. Seahorses are particularly vulnerable to overcollection as they have a limited reproductive rate (due to lengthy brooding) and their social structure can easily be disrupted (due to faithful pair bonding) further reducing the reproductive rate166. To compound the problem their habitat range is under threat from anthropogenic activities, which are quickly destroying ecosystems of the coastal zone. A number of reports167 have expressed concern over overexploitation in the wild and consequent declines in populations of seahorses.

All seahorses are listed as 'Vulnerable' or 'Data Deficient' on the IUCN Red List of Threatened Species, except for H. capensis, which is listed as 'Endangered'. In November 2002, Hippocampus spp. was listed in Appendix II of CITES, to become effective on 15 May 2004, meaning that permits will be required to import and export species of this genus (32 species as recognized by CITES Appendix II). Six species were listed on the basis that harvest for trade exceeds sustainable levels that can be continued in perpetuity, and the remaining 26 were listed to bring trade in specimens of the other species under effective control, as individual Hippocampus species can be extremely difficult to differentiate. The European Regulation, which entered into force in 1997, lists Hippocampus spp. on Annex D. Until their inclusion in CITES Appendix II and thus corresponding up-listing to Annex B on 15 May 2004168, Hippocampus spp. will remain listed in Annex D.

In Australia, seahorses have been protected since 1 January 1998169 as their populations are considered to be rare/and or threatened with overexploitation6. Export permits will be granted only for specimens that have been reared in approved captive breeding programmes, or taken from the wild during an approved harvesting operation.

It is also important to remember that once caught and placed in an aquarium seahorses are notoriously difficult to keep, requiring a steady supply of varied live foods. Moreover, they are highly vulnerable to a number of fungal, parasitic and bacterial infections. Even public aquaria, with access to vast resources and often highly competent and trained staff, admit that these are among the most difficult fishes to maintain in captivity.

Invertebrates

Giant clams, popular invertebrates in the aquarium trade, occur in association with coral reefs throughout the tropical Indo-Pacific region. These bivalve molluscs obtain food in two ways: by filtering phytoplankton (small algae) from the surrounding water and through zooxanthellae embedded in their mantle that are able, through photosynthesis, to produce nutrients, using sunlight. Giant clams are susceptible to over-harvesting due to the ease with which they can be collected (they are sessile, live in shallow water to maximize use of sunlight and can easily be spotted due to their colourful appearance), their late sexual maturity (with size and age at maturity varying with species and geographical location), slow growth, sporadic reproduction patterns and low natural recruitment rates. Insufficient life history information exists to identify conservation issues for the vast majority of more than 500 invertebrate species in trade.

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Responses

  • susie
    What is the avarage size of the mandarin fish?
    7 years ago

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