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1 . Papua New Guinea     Papua New Guinea
REEF FISH DIVERSITY

The diversity of fishes recorded in locations around Papua New Guinea (PNG) is similar to neighbouring countries such as Indonesia, Malaysia and the Philippines (the Indo-Pacific centre of marine diversity). The number of fish species recorded on single dives in PNG is frequently exceptional including many of the highest per site diversities ever recorded during rapid ecological surveys. The diversity of fishes in any given location is largely an interaction between the overall species pool and the variety of habitats available. Species diversity is often correlated with structural complexity of the reef substratum (Munday and Jones 1998) and typically declines on reefs that have been overfished or where the reef structure has been damaged by natural or anthropogenic impacts. The high diversity of reef fishes at locations and individual reefs in PNG indicates that these reefs are probably in good condition.

The most comprehensive published record of fishes for PNG catalogues 2,146 species in 3 volumes (Kailola 1987a, Kailola 1987b, Kailola 1991). Kailola’s checklist of fishes was largely based on the fish collection at the Kanudi Fisheries Laboratory in Port Moresby, which was established in 1960 and contained over 4,500 samples, representing 1,373 species when the first volume of her checklist was published (Kailola 1987a). In the last decade, there has been continued attention to describing the diversity of fishes in PNG, mostly focusing on coral-reef fishes. The total fish fauna of PNG is now estimated to be well over 3,000 species (Kailola 1991; Allen and Swainston 1993), of which approximately 1,500 species are associated with coral reefs (Allen 1998).

Comprehensive species lists of fishes have been compiled for: (1) Kimbe Bay on the island of New Britain; (2) Madang Lagoon; (3) Milne Bay region; (4) Kamiali, near Lae; and (5) Bootless Bay, near Port Moresby. All of these locations exhibit very high diversity of fishes, ranging from 577 - 1,039 species (Table 4). This diversity compares very favourably with locations in Indonesia, where up to 1,111 species have been recorded at specific locations. In PNG, Gobies (Gobiidae) are the most diverse family of fishes at most locations, closely followed by damselfishes (Pomacentridae) and wrasses (Labridae) (Table 5). Preliminary checklists have also been compiled for the Lak region on the southern tip of New Ireland (Gochfeld 1996) and Collingwood Bay, south of Popondetta in the northern Province (Rei unpublished), however the relatively low number of species in these checklists (361 and 110 respectively) indicates that many species remain to be recorded at these two locations.

Total reef fish species diversity has been predicted at local and regional spatial scales using the ‘coral-reef fish diversity index’ (CFDI), developed by Allen in 1998. The combined diversity of 6 key families (Chaetodontidae, Pomacanthidae, Pomacentridae, Labridae, Scaridae, Acanthuridae) is used to predict total diversity of the fish fauna through a simple linear regression equation {for areas less than 2,000km2 the predicted total diversity = 3.39 (CFDI) _20.595}. The 6 families used in the CFDI are suitable for estimating total diversity within sites and ideal for comparing diversity among sites because they are taxonomically well documented, conspicuous and relatively easy to identify, and usually comprise over 50 percent of the fish (Allen 1998). Using CFDI, it is possible to predict total diversity without indepth surveys of cryptic and often difficult to identify species, such as Gobiidae and Blenniidae. The CFDI indicates that the species lists for Milne Bay, Kimbe Bay and Madang are likely to be relatively complete, whereas a considerable number of species remain to be detected in Bootless Bay and Kamiali (Table 4). Cryptic species are probably undersampled in all these lists.

In addition to high overall diversity of fishes in PNG, the diversity of fishes on individual reefs is exceptionally high. During a rapid biodiversity assessment in Milne Bay the number of species seen on 60-90 minute survey dives ranged from 101-270 (Allen 1998). The 4 richest sites were among the highest levels of diversity ever recorded by G.R. Allen during rapid ecological assessments conducted in the Indo-Pacific region (surpassed only by one site in Irian Jaya). In Milne Bay the Conflict Group had the greatest concentration of species with an average of 220 species recorded per dive. In a similar rapid biodiversity assessment in Kimbe Bay, the number of species seen on survey dives ranged from 93-193 (Allen and Munday 1994). In Kimbe Bay, the greatest concentration of species was near Cape Heussner, where at least 180 species (maximum 193) were recorded on each dive. In the Madang area, up to 197 species of reef fish have been recorded on a single dive (Allen 1998), while at the nearby Bagabag Island 264 species were observed in a single dive (Jenkins pers. com). In the Lak region of New Ireland, up to 145 species have been recorded from a single site (Gochfeld 1996). In similar biodiversity assessments by G. R. Allen at other locations, the per site diversity of fishes in PNG has only been equalled or surpassed at three Indonesian localities: the Raja Ampat Islands (off W. New Guinea); Flores; and Komodo Island, where 273, 239, and 203 species respectively have been recorded on a single dive.

The shore fishes of PNG are part of the Indo-west Pacific ichthyofauna (Allen and Swainston 1993; Allen 1998), with all sites sharing most of the same species of fish, however, sufficient species differences between the northern and southern reef fish faunas make them distinct. A cluster analysis of species present in the six key families (Chaetodontidae, Pomacanthidae, Pomacentridae, Labridae, Scaridae, Acanthuridae) at locations in PNG, Great Barrier Reef, Indonesia, and Malaysia revealed that the fish fauna at locations on the north coast and islands of PNG is more closely affiliated with locations in eastern Indonesia than with Bootless Bay on the southern coast of PNG (Fig. 2). Among the locations in PNG the species composition of the fish fauna in Kimbe Bay and Madang are most similar. These two locations in conjunction with Milne Bay and Kamiali are closely allied with the fish fauna of Komodo, Irian Jaya, Manado and Flores. The Bootless Bay reef fish fauna is clearly distinct from the PNG north coast fauna and the Indonesian fauna. The distinction between the fish fauna on the northern and southern sides of PNG is probably linked to the separate geological histories of these areas and to historical and modern barriers to dispersal. The southern part of New Guinea has always been part of the Australian tectonic plate while the northern part of New Guinea is a composite of terranes built up over much more recent geological times (Pandolfi 1992). Therefore, the marine fauna of northern New Guinea has a relatively recent history of establishment. The PNG mainland presents a barrier between northern and southern waters, thereby restricting dispersal of marine organisms between these regions. Furthermore, in recent geological times a land connection between Australia and southern New Guinea during periods of glaciation would have prevented exchange of marine fauna between southern New Guinea and Indonesia (Myers 1991). Unfavourable hydrological conditions in the Arufura Sea may have also prevented dispersal between these regions even when a land bridge was absent. Similar barriers to dispersal did not appear to occur between northern New Guinea and Indonesia. Consequently, the fish fauna of northern PNG has probably had much greater opportunity for exchange of species with Indonesia than the southern fauna. Despite the close geographic vicinity of southern PNG to the northern Great Barrier Reef, and the ancient geological links between Australia and southern PNG, it appears that the Bootless Bay fish fauna can be clearly separated from the GBR fish fauna. This indicates that exchange of fishes between these two locations by dispersive larvae is probably not extensive.

There are relatively few endemic species of reef fishes in PNG. Of 2045 species of fishes from 17 families commonly encountered on coral reefs, only a total of 18 species are probably endemic to PNG and 22 species are probably endemic to New Guinea as a whole (PNG and Irian Jaya; Table 6). Endemics in PNG from the indicator families shown in Table 4 include Chrysiptera cym atilis (Milne Bay), C. niger (Tufi to D’Entrecasteaux), C. sinclairi (Bismarck Archipelago), Pom acentrus albim aculus (Madang area), P. colini (Milne Bay to Port Moresby), Cirrhilabrus condei (Milne Bay and New Britain), C. pylei (Milne Bay), Novaculichthys sp. (Milne Bay). The rate of endemism in the Milne Bay province appears to be considerably higher than other regions of PNG (Table 6). This might be possibly due to the many islands and isolated reefs in the province that could support self sustaining and reproductively isolated subpopulations, thereby promoting species divergence. Several endemics in Milne Bay are known only from very restricted locations and warrant special attention. Trichonotus halstead (Halstead’s Sand-diver) is only known to occur in an area of less than 2,000m2 at Observation Point on Normandy Island in Milne Bay (Clarke and Pohle 1996; Allen 1998). Several undescribed species are only known from the Milne Bay area, at this time. One of these, a species of Rhabdam ia (cardinalfish) has only been recorded from one location. Allen (1998) also notes that the only known population of Chaetodontoplus m elanosom a (Black velvet Angelfish) in PNG occurs at Samarai, Sideia, and Basalaki Islands in Milne Bay. Most records of this species in Indonesia are actually the closely related C. dim idiatus. Therefore, it appears that the stronghold of C. m elanosom a is the cool water on the southern coast of Sideia and Basalaki Islands in Milne Bay. Two species of shrimp goby, Vanderhorstia flavolineata described by Allen and Munday (1995) and Am blyeleotris arcupinna described by Mohlman and Munday (1999) are currently only known from Kimbe Bay and the north coast of New Britain, but are likely to be more widespread.

REEF FISH ABUNDANCE

The abundances of fishes important to commercial and subsistence fisheries have been estimated in a number of locations. In contrast, there have been very few estimates of the abundances of non-commercial reef fishes in PNG. In part this reflects the low capacity for conducting monitoring programs and the lack of expertise in fish identification other than for commercial species. Recent efforts by local and regional universities have established monitoring programs for reef fish populations in several locations. In 1999 an annual monitoring program was established to track fish populations on reefs in Kimbe Bay, some of which have recently been closed to fishing (Table 7). Monitoring of protected areas near Madang has also been established. In January 1999 total reef fish density at four sites in Madang lagoon varied from 4.21-7.91 fish/m2, with a mean of 5.84 fish/m2 (Jenkins unpublished data).

Some evidence suggests that fish stocks on PNG reefs are in good condition, although without good estimates of density over appropriate spatial and temporal scales, there is uncertainty in assessing their status. A questionnaire sent to members of the PNG Divers Association revealed that most respondents had not observed any declines in the overall abundances of reef fishes in their areas of operation. Also, in general, subsistence and artisinal fishing on reefs throughout most of PNG is thought to occur well below maximum harvest levels (Dalzell and Wright 1986; Kailola 1995; Dalzell et al. 1996). The overall level of harvesting may be as little as 20% of the maximum sustainable yield (Huber 1994). Reef fish populations may be under pressure, however, from greater subsistence and artisinal fishing near large coastal towns and cities where there are larger populations and greater access to markets. The size and composition of subsistence and artisinal fisheries catches varies greatly throughout PNG, however, the artisinal component increases markedly around coastal towns (Kailola 1995). Lock (1986a) noted that at least one area near Port Moresby was being overfished and two other areas were fished to their maximum sustainable potential. In the Port Moresby artisinal fishery, the catch of small fish is increasing and catch per unit effort is declining (Lock, 1986b), which is evidence of overfishing. Similar trends have been reported near other population centres (Agardy and Pernetta 1993; Kailola 1995).

Destructive fishing practices have also reduced the abundances and diversity of reef fishes in PNG, although the effects are probably relatively localised (see threats Threats to Reefs chapter). Reef bombing has been practised in many coastal areas (McGregor 1993) and has both a direct effect on abundance of nearly all reefs fishes in the vicinity of the explosion, because of the indiscriminate nature of its action, and an indirect effect through the destruction of habitat. Repeated use of explosives in some areas has resulted in reefs that contain few living corals and are almost devoid of topographic structure (Halstead et al. 1998). Such severe damage to the reef habitat can have dramatic effects on both the diversity and abundances of reef fishes (Sano et al. 1987). Some reefs around Manus Island have been severely damaged by the use of explosives for fishing, which has resulted in a decline in both the diversity and abundances of fishes (Kanawi pers. com).

RECOMMENDATIONS

Marine protected areas and appropriate resource management programs need to be further developed to help protect the exceptional diversity of fishes in PNG. In the first instance marine protected areas might best be located in areas of known high diversity (e.g. Milne Bay, Kimbe Bay, Madang). To be representative of the reef fish fauna, protected areas will also be needed on the southern coast of PNG (e.g. Bootless Bay). The Milne Bay province deserves special conservation attention because of its high diversity and higher rate of endemism than other areas in PNG. Future protected areas in Milne Bay should encompass the distributions of endemic species. Trichonotus halstead (Halstead’s Sand-diver) is so far only known to occur in a small area at Observation Point on Normandy Island and urgent attention should be given to protecting the only known population of this fish.

Biodiversity surveys have been conducted in a number of the major marine regions of PNG. Surveys are now required in the Admiralty Islands and Bouganville region to achieve a more comprehensive assessment of marine biodiversity throughout PNG. The Kanudi fish collection is an invaluable reference collection of PNG fishes, however, lack of proper maintenance and vandalism over recent years has meant it has fallen into disrepair. It needs rehousing and maintaining before it becomes irrepairable.

To date almost all the attention on reef fish abundances has concentrated on estimating the sustainable yield of food fishes (Kailola 1995). There are only a few reliable estimates of abundance for reef fishes and most of these are recent and come from a couple of restricted areas. Monitoring of fish abundances in conjunction with newly established marine protected areas will provide valuable baseline data that is currently missing for PNG fishes. These monitoring programs will also provide quantitative data on the benefits of marine protected areas that is essential for their continued success and for encouraging other communities to establish protected areas. The spatial scale of this sampling, however, will need to be increased many fold and include many more locations if any valid generalisations about the status of reef fish populations in PNG are to be achieved. One of the greatest direct impacts on reef fish numbers currently comes from subsistence and artisinal fisheries, however, overfishing probably only occurs near major population centres such as Port Moresby and other regional coastal towns. Fishing pressure on reef fishes will increase as the populations of coastal towns and cities continues to grow and will be exacerbated by impacts of sewerage and pollution that are associated with large urban populations. Special attention should be given to monitoring fish abundances and size frequencies in areas where populations are increasing rapidly and in areas where future anthropogenic threats are likely. These are the areas most at risk and where well designed monitoring programs can have useful and applied outcomes.
Source: Munday P.L. and G.R. Allen , 2000 , Diversity and Abundance of Reef Fishes in Papua New Guinea. . Chapter 3. In: Munday, P.L. (2000). The Status of Coral Reefs in Papua New Guinea. Global Coral Reef Monitoring Network (GCRMN) Report. (See Document)

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