P. kauderni was found in 74 sites in 30 islands. Four sites were located in the Lembeh Strait (three islands and Sulawesi) in north Sulawesi, where this species was introduced in 2000, and in one site in central Sulawesi (Luwuk). The rest of sites were located within its natural distribution, i.e., the Banggai Archipelago. Here, it was found in 17 of the 20 major islands and in 10 of the 27 minor islands.
The most isolated subpopulation inhabiting a large island was located in the eastern coast of Tempaus, which is separated from the subpopulation inhabiting Masoni Island by 16 km, and towards the west the closest subpopulation is found in south Bokan, at about 30 km. The second most isolated subpopulations inhabit Bangkulu Island, with its north subpopulation separated by about 13.6 km from south Peleng, and by about 13.5 km from Labobo Kenecil. Then, the subpopulation inhabiting Masoni Island is separated by about 11 km from the subpopulation located in Limbo, and by 16 km from that inhabiting Tempaus. Finally, the subpopulation found in Labobo is separated by about 10 km from the subpopulation located in Bangko and by 13.6 km from the closet subpopulation inhabiting Bangkulu. All other large islands are inhabited by at least one subpopulation of P. kauderni that is separated by no more than (and frequently less) 5 km from another subpopulation inhabiting a different large island. Despite that oceanographic and physiographic conditions, as well as availability of habitats and substrates were similar to those found on big islands inhabited by P. kauderni, no populations of P. kauderni were found in the other 17 minor islands, reefs and atolls located far from the big islands. Furthermore, some of these small islands were separated by very short distances from big islands inhabited by P. kauderni. Thus, no subpopulation of P. kauderni was found in Tanalan (localized at only 3.7 km from the subpopulation inhabiting Masepe), Belangan (at 2 km from the population of Bokan), Bongko (at 3.7 km from the subpopulation of north Bangkulu), Sidula (at 5 km from the subpopulation inhabiting center-east Bangkulu), Togonglantan (separated by 5 km from the subpopulation of Bangkulu and by 6 km from that in habiting Labobo), nor in Tabija, which lays at only 1.5 km from the P. kauderni subpopulation inhabiting the bay localized south of Keya on the nor-occidental coast of Taliabu.
The Luwuk subpopulation, whose origin is not clear, is restricted to a very small area inside the harbor and is exposed to high levels of pollution and contaminants. Despite thorough searching from the harbour mouth to as far north as Botok (68 km), and as far south as Luk (46.5 km), no populations of P. kauderni were found outside the harbour, despite that environmental conditions and substrate availability were much better than those inside the harbor. The closest subpopulation of P. kauderni to the one at Luwuk is located about 100 km southeast, in Patipakaman (Peleng Island).
The Lembeh subpopulation is located about 400 km north of the natural range of P. kauderni natural range; it was first detected in the Lembeh Strait in September 2000 occupying an area of approximately 50 m along the coast of Sarina Kenecil Island. The establishment of this subpopulation is a consequence of accidental or intentional releases from an aquarium fish operation in the area. By November 2000 this subpopulation expanded to the "Police Pier" on the margin of Sulawesi, where by May 2001 about 650 individuals occupied an area of approximately 750 x 250 m. By April 2004, P. kauderni extended its range from the Police Pier to at least 200 m to the south, and at least 500 m to the north. In addition, it was found for the first time in Sarina Island, and in Lembeh Island, where it was introduced in 2002 (Erdmann and Vagelli 2001, Vagelli and Erdmann 2002, Vagelli 2005).
See distribution map, and maps in the attached PDF.
- Allen, G.R. and R.C. Steene 1995 Notes on the ecology and behaviour of the Indonesian cardinalfish (Apogonidae) Pterapogon kauderni Koumans. Rev. Fr. Aquariol. 22(1-2):7-10. (Ref. 9936)
- Allen, G.R. 2000 Threatened fishes of the world: Pterapogon kauderni Koumans, 1933 (Apogonidae). Environ. Biol. Fish. 57:142. (Ref. 35396)
Habitat and Ecology
The Banggai Cardinalfish occurs primarily on shallow sheltered bays and harbors, mainly on silty reef flats with sandy bottoms and sea grass beds. Depth distribution is generally ranges between 0.5 and 6 m, but is most commonly found between 1.5 and 2.5 m. Some populations inhabit very clear waters in coral reef areas, while others inhabit still, murky bays, and some groups are found in sandy patches associates with anemones, and less commonly, in open habitats (low branching corals and rubble). This species inhabits a variety of shallow habitats, including coral reefs (51% of identified groups), seagrass beds (35%), and open areas of sand and rubble (14%). It is most common in calm habitats on the protected side of larger islands; isolated populations also occur in areas affected by strong surge and moderate currents Water temperatures in these habitats range from 28°C to 33°C (Vagelli and Erdmann 2002, Vagelli 2005). There is an ontogenetic shift in habitat and microhabitat use between juveniles and adults that occurs within the same area and depth; all size classes, including mating pairs and brooding males, overlap in their distribution; the shift in use is not the consequence of differential feeding habitats nor intraspecific competition (Vagelli 2004a). The processes governing this ontogenetic shift are not clear. No pre-settlement factor is involved, however, because this species lacks a pelagic larval phase and embryos released by brooding males settle into parental habitat directly (Vagelli 1999, 2002, 2004a; Vagelli and Volpedo 2004).
Juveniles associate with sea grasses, sea urchins, sea stars, sea anemones, soft corals and corals. Adults shelter between the spines of sea urchins but also among anemones, corals, stony hydrozoans, rocks and artificial structures such as jetties (Allen 2000, Vagelli and Erdmann 2002, Vagelli 2004a). Sea anemones utilized include Actinodendron sp., Entacmaea quadricolor, Heteractis crispa, Macrodactyla doreensis, Stichodactyla haddoni, and S. merteensis. Corals include Acropora sp., Anacropora sp., Echinopora horrida, Goniopora sp., Heliofungia actiniformis, Montipora digitata and Seriotopora hystrix. Soft corals utilized include Nephthea sp. and stony hydrozoans include Millepora sp. Sea urchin species utilized include Diadema setosum and Tripneustes sp., while the sea star is Proteaster nodosus. Banggai Cardinalfishes also associate with the submerged roots of mangroves (Rhizophora sp.). Census work showed that 43.7% of the groups were associated with hard corals, 31.9% with urchins Diadema setosum, and 24.4% with anemones (Allen 2000; Vagelli and Erdmann 2002; Vagelli 2004a, 2005).
When sheltering in anemones and Heliofungia corals, P. kauderni often associates with various species of anemone fishes (Amphiprion) and anemone shrimps (Periclimenes), and with several species of Apogonidae (Apogon, Archamia, Cheilodipterus and Sphaeramia when living among spines of sea urchins. In seagrass beds (predominantly composed of Enhalus acoroides), P. kauderni is associated with anemones, isolated live corals, sea urchins or sea stars forming small fish assemblages, commonly with Abudefduf sexfasciatus and several species of Pomacentrus, Chromis and Halichoeres.
As opposed to other described apogonids, P. kauderni has diurnal trophic habits, and its feeding activity decreases with the day and ceases around sunset time. P. kauderni is a carnivore-planktivore that feeds principally upon copepods, but it is also a generalist opportunistic species that feed upon a variety of taxa, principally planktonic demersal and benthic organisms. Stomach content analysis found prey representing 29 taxa with a taxonomic level of suborder or higher belonging to 6 phyla: Rhyzopoda, Annelida, Mollusca, Arthropoda, Chaetognatha, and Chordata. There were no significant differences in diet composition between size classes. Quantitative analysis showed that copepods make up about 79% of P. kauderni diet, and that other important components are decapods and isopods. There was an important variation in diet composition among the sites. Representative food items include ascidian larvae, chaetognaths, post-settled gastropod and bivalve juveniles, polychaetes, acarids, copepods, amphipods, stomatopods, cumaceans, isopods, euphausiids, ostracods, cirriped larvae, mysids, decapod larvae, tanaidaceans, and the larvae of teleost and chironomid insects (Vagelli and Erdmann 2002, Vagelli 2005).
Within its natural geographic range P. kauderni formed groups with a mean of 9.5 individuals, although the majority of them were composed of fewer individuals. Group size varied with age class, habitat and microhabitat. The mean size of the 448 censed groups (3,672 individuals) was 8.2 individuals, and the group means per site ranged from 3.9 to 19.8 individuals. Most groups (73% of all groups) were composed by few individuals (1 to 6). The largest single group found was about 500 individuals (Vagelli and Erdmann 2002, Vagelli 2005).
Banggai Cardinalfish pairs defend territories jointly and for three likely reasons: 1) spawning site defense (viewed as unlikely because spawning sites do not seem to be limiting), 2) partner defense (females defending brooding males), and 3) to avoid spawning attempts by "sneaker male" (Kolm and Berglund 2004). Contrary to predictions for a sex role-reversed species, and all other apogonids studied to date, males assume the role of the principal aggressor towards intruders in their territories prior to brooding (Kolm and Berglund 2004). For both males and females, however, territorial aggression is greater towards intruders of the same sex. In experimental introductions of larger male intruders into territories held by male-female pairs, the intruding male was unable to replace the resident male even though the resident female may have courted the intruder; as well, males never courted intruding females. Because this species may have roles that are sexually equivalent, male and females likely play different roles in the defense of jointly-held territories (Kolm and Berglund 2004).
As with other cardinalfishes, the Banggai Cardinalfish is an obligate paternal mouthbrooder (Hayashi 1999). Reproductive behavior was filmed in situ by Dr. Masayoshi Hayashi (Yokusuka City Museum, Yokusuka, Kanagawa, Japan) and the film was broadcast on Japanese television in 1998. Other details on reproductive behavior were obtained from additional laboratory and field studies. Under laboratory conditions, P. kauderni reproduces throughout the year. Single females in captivity can reproduce once per month, whereas males mouth-brood up to six clutches per year. Females, under laboratory conditions can be reproductively active at about 9 months of age and 35 mm SL. The smallest female with signs of advance gonadal maturation found in the wild was 41 mm SL (Vagelli 1999, Vagelli and Volpedo 2004). Females initiate courtship and use a variety of different behavioral patterns during courtship interactions (Vagelli 1999, Kolm 2001). Between a few days and up to two weeks prior to courtship and spawning, a pair will separate from the main group of fishes, establish a spawning site, and commence territorial behavior (Vagelli 1999, Kolm and Berglund 2004). A secondary male may be allowed into the territory and be courted by the female although this male did not interfere with courtship of the primary male (Vagelli 1999). Spawning and juvenile release (settlement) in the wild appears to follow a lunar cycle, with a major spawning peak during full moon and a second, smaller peak during the last quarter, although in one geographically-distinct population major spawning activity occurs during the last quarter (Vagelli and Volpedo 2004). Courtship occurs during daylight hours and, in laboratory conditions, concludes by mid-afternoon. At the time of spawning and egg transfer, the female exudes an egg mass from her genital papilla that is pulled, fertilized, and then gulped by the male. P. kauderni possesses low fecundity, females produce small egg clutches of up to about 75 eggs of 2.5–3-mm in diameter. The mean clutch size found being incubated by males in the wild was 41 eggs (range=12 to 73) (Vagelli 1999, Vagelli and Volpedo 2004). The male broods an egg clutch for about 20 days; after hatching, the eleutheroembryos (free embryos) remain within the mouth cavity for another 10 days before release. Under laboratory conditions, a female would also court and even spawn with a secondary male (Vagelli 1999). Following spawning and egg transfer, females defend the brooding male from intruders while males manipulate egg masses within their oral cavities; occasionally, intruders attempt to take eggs from a male’s mouth. The fertility rate under laboratory conditions is about 40 to 60%. Besides normal loss due unfertilized eggs and embryos that do not finish developing, an important percentage of eggs are lost during the clutch transfer (Vagelli 1999). Males do not feed while incubating the eggs; upon hatching some 20 days after spawning, the embryos are held an additional 10 days until their yolk is consumed. Then, the juveniles, about 5.0 to 6.0 mm SL, are released from the male's oral cavity. A major settlement peak appears to occur during the full moon and a second minor peak during the new moon (Vagelli and Volpedo 2004). Vagelli (1999, 2004b) and Kolm (2001, 2002) provide laboratory studies of the reproductive biology and early ontogeny of this species, while Vagelli (2004a), Vagelli and Volpedo (2004) and Vagelli, 2005 provide data from field studies. Principal characteristics of the reproductive biology include: 1) parental care of an advanced degree, 2) an elevated level of energy investment per offspring, 3) low fecundity, 4) direct development, 5) a lengthy oral incubation period that includes the retention of free embryos after the eggs hatch, 6) settlement of juveniles within the habitat of their parents (Vagelli and Volpedo 2004).
The sex ratio within groups is approximately equivalent (Vagelli and Volpedo 2004). Longevity in captivity can reach 4 to 5 years (although reproductive activity decreases substantially after 2 to 3 years). However, in the wild most adult specimens are significantly younger (about 2 years old or less). Growth studies in captivity and using wild specimens show P. kauderni follows von Bertalanffy equation L∞ = 69 ± 1.58 mm, k = 0.21 ± 0.016, t0 = -0.72 ± 0.15 months (r²= 0.99). At 12 months of age P. kauderni reaches a SL of about 43.5mm (TL of 64.5mm), at 18 months 47mm (70 mm TL). The largest wild specimen encountered was about 58 mm SL (88.5 mm TL) (A. Vagelli, pers. comm. on 27th Feb 2007).
This species has a relatively short life span (ca. 2.4 years), matures at an average of 0.8 years (FishBase 2004) and has a generation time of 1.5 years (A. Vagelli, pers. comm. on 27th Feb 2007); these are all indications of reasonably good resilience. Unfortunately, this species' small population size, limited distribution, low fecundity, great parental investment, and rate of extraction lower this species resilience with corresponding severe negative effects. The combination of a lack of planktonic dispersal and particular oceanographic characteristics of the Banggai region (deep channels and strong currents) has likely contributed to the extreme philopatry of this species. In addition, its within-parental habitat recruitment, sedentary nature, and shallow habitat preference preclude P. kauderni from dispersing even to nearby islands and have led it to a high degree of genetic structure (Bernardi and Vagelli 2004). P. kauderni is especially susceptible to indiscriminate collecting, e.g., its association with shallow microhabitats greatly facilitates its capture, while the lack of dispersal mechanisms make it almost impossible for this species to re-colonize areas where they have been depleted (A. Vagelli, pers. comm. on 27th Feb 2007).
This species is highly prized in the aquarium trade and thus highly vulnerable to over-fishing, post-capture mortality, and habitat destruction.
- Allen, G.R. and M.V. Erdmann 2012 Reef fishes of the East Indies. Perth, Australia: Universitiy of Hawai'i Press, Volumes I-III. Tropical Reef Research. (Ref. 90102)
- Allen, G.R. and R.C. Steene 1995 Notes on the ecology and behaviour of the Indonesian cardinalfish (Apogonidae) Pterapogon kauderni Koumans. Rev. Fr. Aquariol. 22(1-2):7-10. (Ref. 9936)
Life History and Behavior
Molecular Biology and Genetics
Barcode data: Pterapogon kauderni
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Pterapogon kauderni
Public Records: 7
Specimens with Barcodes: 8
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
Several subpopulations affected by the aquarium fishery exhibited dramatic declines between 2001 and 2004, among them: a complete extinction of a subpopulation was documented off Limbo Island in 2004. According to a 2001 census this subpopulation was composed of about 50,000 fish (densities = 0.02 fish/m²); and a small subpopulation off Bakakan Island that harbored 6,000 fish in 2001 was reduced to 17 individuals in 2004 (Vagelli 2005).
The rate of decline for this species is difficult to calculate, since the earliest quantitative surveys (2001) were carried out several years after the harvest began within its natural geographic range. However, one subpopulation localized inside a bay in Southwest Banggai Island has been off limits to all fishing since before the beginning of the trade (the bay is privately owned by a pearl farm business). The bay has the typical habitats, microhabitats, and oceanographic characteristics in which P. kauderni is found throughout the Archipelago, and therefore this subpopulation may be used to estimate what the historical baseline abundance for this species could have been. The density of this subpopulation was 0.63 individuals/m²).
This density is significantly higher than the mean density (0.07 individuals/m²) of the eight censuses completed in 2004 in unprotected sites [S = 0.05; highest d= 0.21 (Bokan); lowest d= 0.028 (Bangkulu)]. In addition, a census was carried out about 300 m from the protected bay and the density was 0.071 ind./m² (Lunn and Moreau 2004, Vagelli 2005). If the 0.63 density value is considered as the historical normal density for this species within the Archipelago, then a reduction of approximately 89% took place since the start of the fishery (about 9 to 10 years before the 2004 censuses).
However, at one of these sites (Masoni) the density increased from 0.03 to 0.06 individuals/m² between 2001 and 2004. This increase is thought to have occurred in response to a collecting ban that the local people imposed in early 2003. In another site (Bokan) a more significant increase was found in 2004, i.e., 0.21 individuals/m². In this case too, collection in the census site (which has an area of occupancy of only about 1 km²) was banned in 2002 by the village chief because of disputes with outside collectors (Vagelli 2005).
The size class structure of populations found during the last survey (2004) within the natural range of P. kauderni, agree with those reported previously, where most fish encountered were large juveniles (6 to 9 months old), whereas newly released recruits (<15 mm TL) are rare (Vagelli and Erdmann 2002). Thus, in 2004 of a total of 3,672 individuals censused, within the Archipelago, 1,364 (37.1%) were adults, 2,140 (58.3%) were older juveniles and 168 (4.6%) new recruits and small juveniles up to about 2 months of age (Vagelli 2005).
The decline information is not sufficient to apply Criterion A and likewise Criteria C and D cannot be used because the population is too large. However, based on the very small area of occupancy (AOO), the severe fragmentation (see the documentation below) and the ongoing continuing decline (local extirpations and marked decrease in population size in recent years) due to exploitation for the international aquarium trade, this species is assessed as Endangered under Criterion B.
P. kauderni exhibits the highest degree of population structure that has been documented for a marine fish (Hoffman et al. 2005). This is a unique case of genetic isolation in populations separated by extremely short distances. Studies utilizing both mt DNA and micro-satellites have already indicated that populations occurring on reefs of the same islands, separated by only a few kilometers, are genetically isolated from one another (Bernardi and Vagelli 2004). For instance, assignment tests performed in 23 subpopulations from all over the Archipelago, showed that 20 had a significant self-reassignment. When considering all the Bangkulu populations, 94% of the individuals from this island were reassigned back to the island - range 80.0% to 100% (Vagelli et al. in prep.). The lack of suitable habitats between subpopulations coupled with lack of dispersal mechanisms, are the most likely reasons for this isolation.
Banggai Cardinalfish populations are distinguished for having two monophyletically-distinct clades: a southwestern clade restricted to the southwest of Bangkulu Island, and northern and eastern clades distributed throughout the remainder of its range (Bernardi and Vagelli 2004). Eleven polymorphic tetranucleotide microsatellite loci have been isolated from male fishes; polymorphism ranges from 2 to 15 alleles and expected heterozygosities range from 0.107 to 0.928, thus allowing for genetic studies of this species with very high resolution (Hoffman et al. 2004).
Generation length is estimated at being 1.0 years (FishBase 2004), however more recent estimates place it at 1.5 years (A. Vagelli, pers. comm. on 27th Feb 2007).
Although resident in naturally-silty harbors and bays, this species might experience negative impacts from harbour dredging and associated pollution, as well as sediment from coastal development and use.
Juveniles may be vulnerable to local population dynamics of anemones and sea urchins that provide mutualistic microhabitat. Threats to these might be from harvest (aquarium trade or food trade) or coral bleaching (anemones). Adults may be vulnerable to local population dynamics of sea grasses.
Threats to the Species:
The Banggai Cardinalfish is highly-prized in the aquarium trade (Allen 2000, Vagelli and Erdmann 2002, Kolm and Berglund 2003). It has been heavily exploited by the aquarium trade since its rediscovery in 1994. Despite claims that captive breeding has been successful, most aquarium specimens are still captured in the wild. Fishes are collected, mainly with nets, and held in floating nets until purchased by fish buyers who visit individual fishers at least 3 to 4 times a month. Collectors are paid a small sum (ca. US $0.01 to 0.025 in 2001) per fish by buyers who, in turn, sell to exporters for US $ 0.10 to 0.12 a fish (Vagelli and Erdmann 2002). Since 1999, the fishery has expanded from Banggai Island and Bandang Island to villages in the Bokan area, on Bangkulu Island, Labobo Island, and Peleng Island, with most collection occurring near their own villages. By 2001, at least 17 villages and 230 fishermen were involved in the P. kauderni trade (Lunn and Moreau 2004). An estimated minimum of 600,000 to 700,000 individuals were collected per year by local fishers prior to 2001 (Vagelli and Erdmann 2002, Lunn and Moreau 2002); current harvest rates are believed to exceed 700,000 to 900,000 fish/yr (Vagelli 2005).
P. kauderni are shipped primarily by boat from the Banggai Archipelago to national exporters via Tumbak and Manado and to a Bali exporter via Palu, and also direct to Bali exporters. An estimated 115,000 fish/month were transported on the Tumbak–Manado route, 3,000/month along the Palu to Bali route, and up to 10,000 fish/month were sent direct to Bali in 2001 (Lunn and Moreau 2004). These numbers are close to earlier estimates of 50,000 to 60,000 fish/month arriving in North Sulawesi for exportation, with total estimated trade for 2000 and 2001 of 700,000 fish (Vagelli and Erdmann 2002). Transhipment mortality is high because of lengthy travel times, usually 18 to 48 hours by boat (Vagelli and Erdmann 2002); no data on mortality from collecting or holding prior to transhipment appears to be available. The high mortality rate contributes to the disparity in prices paid to fishers and buyers (Vagelli and Erdmann 2002). A minimum of four aquarium fish export companies operate in Bali; others exist in Kendary and Manado (Sulawesi). he majority of P. kauderni captured in the Banggai Archipelago are destined for the international aquarium trade, with most exported to the United States, Europe and Asia. Wabnitz et al. (2003) and Lunn and Moreau (2004) further document the aquarium trade.
In addition to the estimate of number of individuals collected and shipped reported in the assessment, trade surveys carried out by Lunn and Moreau (2004) suggest that a minimum of 118,000 Banggai Cardinalfish were sold each month by fishers in the Banggai Islands. Trade volumes are in all likelihood greater as this estimate only includes fish bought by Tumbak- and Palu-based buyers, not taking into consideration individuals collected and shipped from alternate locations, or lost to pre-sale mortalities in fishers’ holding cages (Lunn and Moreau 2004).
A recent study showed that, despite the use of non-destructive fishing methods, the fishery had a negative effect on fish density when sites with high fishing pressure were compared to sites with low fishing levels (Kolm and Berglund 2003). 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) (Stephens et al. 1999, Stephens and Sutherland 1999, Kolm and Berglund 2003).
In addition to more detailed trade statistics to accurately reflect real trade volumes, regular monitoring of the fishery should be undertaken, particularly as studies seem to indicate that the expansion of the trade to new, previously unexploited areas is underway, moving outwards from Banggai Island to all of the major islands in the area. Lunn and Moreau (2003) also highlight that the pool of potential fishers could be large, particularly given that obstacles to entering the fishery appear to be minimal and alternative livelihood opportunities limited.
This species is reportedly parasitised by four main parasite types. Three of them have been already identified, i.e., nematodes (6.6% of all individuals analyzed), digenetic trematodes (7.9%); and 4.8% of individuals were parasited by cestodes (plerocercoid larvae). The last type of parasites found consists of an undescribed isopod which was found encysted in the body cavity and on the external stomach wall of 7.2% of individuals analyzed. These endoparasites are currently being investigated and preliminary results indicate that they belong to a new family of epicaridean isopods with an unknown life cycle (Vagelli and Erdmann 2002, Vagelli 2005).
Indirect evidence strongly suggests that the Crocodile-fish Cymbacephalus beauforti (Platycephalidae), several species of Lion-fish Pterois (Scorpaenidae) and the grouper Epinephelus merra (Serranidae) prey upon P. kauderni, particularly in areas inhabited by large groups. Other likely predators are the Stonefish Synanceia horrida (Scorpaenidae), several species of moray eels of the genus Gymnothorax, and Echidna nebulosa (Muraenidae) and the sea-snake Laticauda colubrina (Elapidae) (Vagelli 2005).
The species is thought to suffer high mortality during the first days after settlement due to predation, including cannibalism (Vagelli 2002). For instance, despite that under laboratory conditions the average number of juveniles released was 40, and the average clutch size of brooding males in the wild was 18 embryos, out of 81 groups of new recruits found in the wild during 3 expeditions, most of them consisted of one or two individuals (mean: 2.3 individuals). The three largest groups found consisted of 15, 12, and nine individuals (Vagelli 2004a, Vagelli 2005).
A newly emerging threat (a viral disease) has been documented in wild-harvested individuals maintained in captivity. The origin of the iridovirus, as well as the prevalence in and impacts to wild populations, is currently under investigation (A. Vagelli, pers. comm. on 27th Feb 2007).
Frequent earthquakes recently affected several zones within the Banggai Archipelago had a potential detrimental impact on localized P. kauderni subpopulations
In order to obtain reliable estimates of trade volumes for this and other marine ornamental species it is recommended that Indonesian government (and other governments) disaggregate the ‘aquarium fish’ category so that trade statistics can be obtained at least for marine versus freshwater species; and ideally by species.
It is further recommended that a trade monitoring system be established through direct collaboration with 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 (Wabnitz et al. 2003). Moreover, collectors and traders should be encouraged to gain MAC certification for the Banggai Cardinalfish.
Additional 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 recommended (Lunn and Moreau 2004). The development of environmental education material and programmes to promote public awareness are strongly encouraged and the potential implementation of marine protected areas should also be investigated (Lunn and Moreau 2004).
In summary, conservation actions required for this species include the development, implementation, and effective enforcement of regulations designed to significantly reduce and regulate the collection and export of this species for the aquarium trade (a proposal to include this species in CITES Appendix II was withdrawn (CoP 14 Prop. 19 ); and to protect and conserve critical habitat. Management actions that would benefit both this species and the fisher communities that harvest it at present could include artificial propagation at the local level with the intention of substituting completely captive-bred fish for wild-caught fish. In addition, a concerted and effective effort should be made to reduce post-capture mortality at all levels of the collection, marketing, and export chain.
Relevance to Humans and Ecosystems
The Banggai cardinalfish (Pterapogon kauderni) is a small tropical cardinalfish family Apogonidae. It is the only member of the genus Pterapogon. This attractive fish is popular in the aquarium trade. It is among the relatively few marine fish to have been bred regularly in captivity, but significant numbers are still captured in the wild and it is now an endangered species.
This species is restricted to the Banggai Islands of Indonesia. This species has an extremely limited geographic range (5,500 km²) and small total population size (estimated at 2.4 million). The Banggai cardinalfish is composed of isolated populations concentrated around the shallows of 17 large and 10 small islands within the Banggai Archipelago. A small population also occurs off Central Sulawesi, within Luwuk harbor. One additional population has become established in the Lembeh Strait (North Sulawesi), 400 km north of the natural area of the species distribution, following introduction by aquarium fish traders in 2000. Small populations seen (May 2014) in Secret Bay, north west Bali (Banggai cardinal fish, Secret Bay, Bali)
This species grows up to 8 centimetres (3 in) total length. It is easily differentiated from all other cardinalfish by its tasseled first dorsal fin, elongate anal and second dorsal fin rays, deeply forked caudal fin, and color pattern consisting of three black bars across the head and body and prominent black anterior edges on the anal and second dorsal fin. The male can be differentiated from the female by a conspicuous enlarged oral cavity, which is apparent only when they are brooding.
The Banggai cardinalfish is the only member of its family that is diurnal. It is a demersal tropical marine fish that forms stable groups of about 9 individuals in shallow water, being most common at 1.5 to 2.5 meters in depth. It inhabits a variety of shallow habitats, including coral reefs, seagrass beds, and open areas of sand and rubble. It is most common in calm habitats on the protected side of larger islands. It is often found associated with the seagrass Enhalus acoroides and the long spined sea urchin Diadema setosum. It occurs among various living benthic substrates such as sea urchins, sea anemones, and branching corals; young fish are most commonly associated with sea anemones, while juveniles and adults occur most frequently among long-spined sea urchins and branching corals, as well as sea stars, hydrozoans, and mangrove prop roots. Individuals of 2 to 60 hover above the urchins, with the younger ones about 2 to 3 centimeters SL staying closest to them. The fish retreat among the spines when threatened. Individual fish exhibit well-defined homing behaviour and return to the original location of their group when disturbed. The Banggai cardinalfish often coexists with various anemonefish and anemone shrimp when sheltering in anemones and corals; when found among sea urchin spines, it associates with several other genera of cardinalfish. Following removal of the fish by aquarium collectors, the abundance of associated invertebrates has been shown to decline.
This fish is an opportunistic feeder. Its diet includes planktonic, demersal, and benthic organisms. Copepods constitute the bulk of their diet. It serves as an important food source for several species of lionfish (Pterois spp.), the honeycomb grouper (Epinephelus merra), the crocodilefish (Cymbacephalus beauforti), the snowflake moray (Echidna nebulosa), the estuarine stonefish (Synanceia horrida), and the yellow-lipped sea krait (Laticauda colubrina).
The Banggai cardinalfish is a paternal mouthbrooder. The female plays an active role in courtship and pair formation, which occurs a few hours to a few days before spawning. Mating pairs establish spawning territories several meters away from the main group and vigorously defend them. The eggs are about 2.5 millimeters in diameter. The young remain in the male's mouth cavity for an undetermined period after hatching. Unlike many other species of marine fish, the Banggai cardinalfish lacks a planktonic stage in its life history. The species has a short life span, reaching around four years in optimal conditions in captivity, and perhaps 1 to 2 years in the wild.
The fish is collected by local fishers and sold into the aquarium trade. This species first appeared in the international trade around 1995 or 1996. By 2001, 600,000 to 700,000 fish were exported annually. Trade estimates for 2001 through 2004 are 700,000 to 900,000 fish per year with collection occurring throughout the archipelago. Surveys identified significant (>90%) declines in two populations that were fished from 2001 to 2004, including the extinction of a population off of Limbo Island.
This fish has been successfully bred in captivity. Captive breeding presents an alternative to wild-caught fish. However, the relatively high cost–benefit ratio of its production combined with the large number of less expensive wild-harvested fish has prevented expansion of aquaculture efforts. In addition, a newly emerging threat in the form of a viral disease has been documented in wild-harvested individuals maintained in captivity.
Collection for the aquarium trade has threatened this species with extinction. This increases the demand for captive-bred specimens. It is listed as an endangered species by the IUCN based on its small range, the fragmentation of its distribution, and its continuing decline due to exploitation for the international aquarium trade. In 2007, it was proposed that the species be listed for protection under CITES Appendix II, which could limit export of wild caught individuals, but Indonesia would not support this, and the proposal was withdrawn.
The Banggai cardinalfish are sexually monomorphic. The pairs form up to two weeks prior to spawning. The female courts the male from pair formation until spawning. The female's size determines the fecundity and egg size, but the male's size determines the reproductive output, or the amount of the eggs that the pair produces. Therefore, pairing tends to occur among individuals of similar sizes, so the male is able to care for all the eggs that female produces.
In the Banggai cardinalfish, courtship behavior is usually initiated by the female. Upon choosing a mate, the female isolates her potential mate from other individuals in the colony by creating a spherical spawning site that is about 50-60 centimeters in diameter. The general movement that the female exhibits is called ‘side by side trembling,’ which is where the female approaches the male from behind with a vigorous trembling motion while the male stays motionless. Then she places herself alongside him and tilts her body thirty degrees outward from its vertical plane, when the male and female’s caudal and anal fins come into contact. The female repeats this movement until the male responds with sporadic ‘mouth opening,’ a sign of receptiveness. Such courtship behavior may last from several hours to two to three days. When an intruder interrupts a female’s courtship behavior, the female would rapidly and aggressively chase the intruder away if the intruder is of the same sex. However, when the secondary male, or the intruder male approaches, he, instead of the female, exhibits trembling behavior, and also helps to defend the female and primary male’s isolated territory. If the primary male does not respond to female’s trembling, the female leaves periodically to visit the secondary male and displays trembling behavior which often results in mating.
Selection of mates
Although the females initiate courtship, female and male cardinalfish are mutually selective. Females have been observed courting larger males more intensively. Even when they are already in the process of courting one male, they often moved on to an intruder male if it is larger than the original. Females have also been observed producing larger eggs for larger, hence more ‘attractive,’ males. Females are also able to increase egg size even after the onset of egg maturation if they encounter a new, larger male to brood its eggs. Male Banggai cardinalfish also exhibit preference by size, as larger females tend to lay larger eggs, and egg size positively affects traits such as offspring size, survival, growth, time until maturation, and swimming performance. However, it also takes into account information conveyed by females’ courting movement. The ‘side by side trembling’ described in the previous section can be subcategorized into two different movements: ‘rush’ and ‘twitch’. ‘Rush’ refers to the first part of the movement when the females approaches the male, folding the pelvic, dorsal and anal fins together and quickly swimming past the male for a distance of 10-40 centimeters. Then it performs the ‘twitch’, where it twitches, or trembles her body close to the male. Studies have shown that the intensity of the ‘rush’ behavior is important for the male in predicting the female’s potential reproductive effort, as the intensity of the behavior correlates positively with clutch weight. On the other hand, the number of twitches performed per day strongly associates with how close to spawning the female is. By forming a pair with a female with more mature eggs, or closer to spawning, a male can increase his reproductive rate. Furthermore, it can match his readiness to spawn to females’ by observing its ‘twitch’ behavior.
When the male accepts female courting, the female expels eggs from the urogenitial papilla. Female Banggai cardinalfish produce a relatively small clutch, consisting of no more than ninety eggs that are two to three millimeters in diameter. Once approximately three-fourths of the egg mass protrudes from the female, the male takes the eggs from her. This process is immediate, taking no more than two seconds. Eggs may be lost in the process if the male drops them, as it is usually immediately consumed by other fish in the area. Males also have the ability to detect dead eggs and expel them from his mouth. The male broods the eggs in his mouth for up to 30 days, during which it does not feed. After spawning, the female stays with the brooding male for at least few days. Females aggressively defend its territory by immediately chasing any intruders that approach the brooding male. They also exhibit relaxed form of ‘side by side trembling’, and confine the male to a small space.
Juvenile Banggai cardinalfish do not go through any pelagic larval phase. Instead, they experience a high growth rate. Although the free embryos maintain their size difference after hatching, they grow several folds while being brooded inside their father’s mouth. Therefore, at release, juveniles are many times heavier than they were at hatching. Juveniles settle directly within the parents’ habitat upon release from their father’s mouth. They form a tight school around different structures such as sea urchins, corals and anemones and swim around together while the father does not exhibit much caring behavior.
Banggai cardinalfish live in shallow lagoons in groups that include up to 500 individuals. They are often found near sea urchins, where the fish hide when threatened. They are capable of hiding among the spines of sea urchins without being stung. In addition to sea urchins, other living benthic substrates such as soft corals, anemones, hydrozoans and mangrove roots also serve as microhabitats where the Banggai cardinalfish group around. These groups of fish are rather sedentary, and movements between groups are observed to be very limited especially because they feed on plankton that pass through water currents. Such limited dispersal of Banggai cardinalfish prevents them from spreading over large geographic ranges, and thus serves as a major risk of extinction along with heavy exploitation by aquarium fish collectors as well as low fecundity.
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