2002.05.13

First Day Cover:

4 stamps

Printing: Offset Lithography with Die-Cut
Paper: 110 gsm
Stamp Size: 30 mm x 48 mm
Perforation: 13 per 2cm
Designs:
48c: Redigobius sp.
96c: Spotted Flagtail (Kuhlia Marginatus)
$1.23: Silverstripe Mudskipper (Periopthalmus Argentilineatus)
$2: Snakehead Gudgeon
Sheets of 50 stamps
Designer: Mr. Nick Cartmell
Artist: Mr. George Bennett
Text: Aaron Jenkins, MSC
Printers: Cartor Security Printing, France

Although the marine fishes of the Fiji islands are reasonably well documented, the same cannot be said of the freshwater fish fauna. Very few studies have been done to determine which freshwater species inhabit Fijian freshwater habitats. Freshwater fish species are those that either live their entire life cycle in freshwater or are commonly found in this habitat as an adult. Freshwater habitats can be broadly classified as either 'lotic' (flowing) or 'lentic' (still). Lotic ecosystems include streams, flowing springs or seepages, artificial ditches and flumes. Lentic systems contain two types of standing waters which ecologists refer to as 'palustrine' (bogs, marshes and swamps) or 'lacustrine' (lakes, ponds and reservoirs). Most of these major habitat types are represented in Fiji, and most are populated by fishes.

Within each of the main ecosystems there is considerable variation, depending on local factors such as terrestrial vegetation, climate and human impact. As far as we know most freshwater sites in Fiji are populated by relatively few species. For example, the average number may range from 4-5 species for small creeks in mountainous terrain to 15-20 for larger floodplain rivers.

Fishes inhabiting a particular stretch of stream or section of pond are finely tuned to their surroundings. Their continued survival is dependent on the availability of adequate food resources and shelter, as well as the correct conditions for breeding. Food supplies fluctuate greatly according to the seasons, and the life cycles of resident fishes are often geared to make maximum use of these resources for the production of gametes and the growth of their young.

One of the major threats to the indigenous freshwater fishes and freshwater habitats of Fiji is the introduction of fishes that are not native to the Fiji Islands. Ecological impacts to native fauna by introducing non-native fauna include 1). habitat alteration (ie. displacement of aquatic vegetation/degradation of water quality) 2). Introduction of parasites, pathogens and diseases 3). Trophic alterations (ie. may prey on naturally abundant native species) 4). Hybridisation - (ie. deterioration of native genetic stocks) 5. Spatial alterations (ie. overcrowding may inhibit breeding of native species).

Like many island countries of the Pacific, the freshwater fish fauna of Fiji is fairly impoverished (ie few species) and dominated by euryhaline (able to tolerate a wide range of salinities) species of marine origin. Currently there are 32 known indigenous freshwater fishes in the Fiji Islands and 15 introduced fishes that have established themselves in Fijian freshwaters. Fortunately, there are no reports of extinction events involving indigenous Fijian freshwater fishes. There is no doubt that logging, urban development and pollution will continue to impact native freshwater fish populations, and could conceivably result in extinctions. Many species have highly localised distributions and are therefore extremely vulnerable. The following five fishes highlight the beauty and importance of the indigenous Fijian freshwater fish fauna.


The Spotted Flagtail (Kuhlia marginata) :
This silvery fish can be seen in the brackish waters of estuaries but is most commonly seen in small, clean, fast-flowing coastal streams, within several kilometres of the sea, where it congregates in rocky pools below rapids and small waterfalls. This species can also penetrate far inland in large rivers such as the Rewa. All species within the family spawn eggs that float in the water column. They feed on insects and their larvae, prawns crabs and small fishes. They can reach around 20 cm length and can be an important source of protein for inland communities. In Fiji, there are three known species of Flagtail. The Spotted Flagtail is known from New Guinea northward to southern Japan and east to the Society Islands.


The Snakehead Gudgeon (Giurus margaritacea):
This brightly coloured fish occurs in a wide variety of habitats including large rivers, swamps, lakes and turbid or clear tributary streams to elevations of at least 400 m. Spawning occurs year round with each female depositing between 100,000 - 220,000 eggs. Eggs are deposited on the bottom and adults provide parental care for the eggs. The main items in the diet of adults are aquatic insects and nymphs with lesser amounts of algae, other aquatic plants and small crustaceans. The species can reach a maximum size of about 20 cm length. This species is widely distributed from Madagascar to northern Australia and the islands of Melanesia. This species was formerly referred to as Ophieleotris aporos.


The Common Mudskipper (Periophthalmus argentilineatus):
This peculiar looking fish usually occurs in brackish mangrove areas and occasionally in the lower sections of freshwater streams usually below about 20 m elevation. It often rests on the muddy banks above water and on the bottom while underwater. It can be found individually or in groups and is carnivorous, with insects as its primary diet. It lays its eggs on the bottom and adults provide parental care for the eggs. It can reach a maximum size of about 10 cm length. This species is widespread in the tropical Indo-Pacific region from East Africa to Samoa.


The Rainbow Prigi (Hypseleotris geuntheri ):
This colourful fish is restricted to purely freshwater habitats and is usually found in clear-flowing streams within 5-10 km of the sea. It is usually found hovering in mid-water in schools. It is a carnivore and eats primarily insects and micro-crustaceans. Females deposit thousands of eggs on rock, wood or plants and then provide parental care until the eggs hatch. It reaches a maximum size of around 6 cm length. This species is known from Indonesia, New Guinea, New Ireland, Caroline Islands, New Caledonia, Fiji and Samoa.

A new species for the Fiji Islands - (Redigobius sp.)
This beautiful fish was found in 2001 by the author and students as part of a wetland managers training course in the Savura River watershed. It was found in a stream that feeds Suva's main water supply and is also found in streams in the Nakavu area. It is potentially a species new to science with its closest affinities to Redigobius leptochilus. If it is indeed R. leptochilus , which has only been recorded from Indonesia, West Papua and Palau, then this would be a new species record for Fiji. This stamp is a painting based on the first photographic image ever captured of this species. Other members of this genus inhabit fresh and brackish waters such as mangroves, tidal creeks, and lowland streams below about 50 m elevation. They rest on the bottom either solitary or in groups. They are all carnivorous with benthic invertebrates their primary food source. They tend to lay their eggs on the available substrate and exhibit parental care of the eggs. These are tiny fish and obtain a maximum size as adults of 3.5 cm. Currently, this species is only known from Fiji.

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