FALKLAND ISLAND FRESHWATER FISHES

ZEBRA TROUT REPORT

There are several thousand freshwater ponds and lakes in the Falkland Islands, along with many streams and small rivers. Coastal ponds are generally more fertile, more profilic in aquatic vegetation and attract large numbers of duck and grebe. The Falklands have several significant river systems, the most important among them being the Murrell, Malo and San Carols rivers on East Falkland and the Warrah and Chartres rivers on West Falkland. These rivers are rain fed, sometimes peat stained and relatively acidic. Many streams, where they cross the heath lowlands at the base of small valleys, are often bordered by rich green swards with extensive areas of brown swamp rush, tall rush and small rush. Accumulations of peat are widespread but there are no large areas of blanket or bog areas.

Waterfowl

Swans, geese and ducks form the most numerous family of birds in the Falkland Islands. 22 species have been recorded. The 14 resident birds are:

Black-necked Swan Photo: Allan White

Black-necked Swan Coscoroba Swan Kelp Goose Upland Goose Ruddy-headed Goose Chiloe Wigeon Falkland Steamer Duck Flying Steamer Duck Crested Duck Yellow-billed Pintail Speckled Silver Teal Silver Teal Cinnamon Teal Red Shoveler

Cygnus melancoryphus Coscoroba coscoroba Chloephaga hybrida malvinarum Chloephaga picta leucoptera Chloephaga rubidiceps Anas sibilatrix Tachyeres brachypterus Tachyeres patachonicus Lophonetta spectalariodes spectalariodes Anas georgica spinicauda Anas flavirostris Anas versicolor fretensis Anas cyanoptera Anas platalea

Chiloe Wigeon Photo: Allan White

All but one of the Falkland species are powerful flying birds that also breed in southern South America but there is no firm evidence that Falkland breeding waterfowl migrate. The Falkland Steamer Duck, an endemic species that has short wings and a very heavy body, cannot achieve free flight. The four geese belong to a strictly southern South American group known as sheldgeese. Upland, Ruddy-headed, Ashy-headed (a vagrant) and the female Kelp Geese all have similar black and white wing patterns. Birds and Mammals of the Falkland Islands gives full details of all these birds, and more.

Freshwater Fish

There are two explicitly freshwater fish species native to the Islands:

The Zebra Trout Aplochiton zebra
In 1833-34 Charles Darwin, or his shipmates, collected from the Falkland Islands the first specimens of the zebra trout known to science. A midwater species, it reaches at least 225mm in the Falklands and, not a shy fish, can be seen swimming freely in pools in streams. It is now struggling to survive and has all but disappeared from all of the waters where brown trout have become established.

The Falklands Minnow Galaxias maculatus
This is a small slender fish very widespread throughout the Falklands, especially in the lower reaches of streams but in many lakes and ponds swimming in small loose shoals. They can grow to 120mm, but more often are a much smaller 70-80mm. Both the minnow and the zebra trout are thought to spend part of their lives at sea.

Three primarily marine species are itinerant invaders of Falklands fresh waters: the Falklands mullet Eleginops maclovinus, and two species of atherinid ‘smelt’, Odontesthes smittii and O. nigricans.

The European and British brown trout Salmo trutta
Introduced into the Islands in the 1960s, is now one of the most widespread and commonly encountered freshwater fishes in the Islands.

The Falklands are now recognised as outstanding for its trout fishing. Go to www.falklands.gov.fk/Trout_Fishing.html for more about the fishing, the season for this and regulations.

For further information and identification of Falkland freshwater fishes see Falkland Islands Freshwater Fishes: A natural history, available from our webshop.

Freshwater Fish Report
The results of a project undertaken in December 2008 and January 2009 to survey the two native Falkland freshwater fish, Zebra trout and Falkland minnow: Freshwater Fish in the Falklands – Conservation of Native Zebra Trout

News Report
Zebra Trout incident at Cape Dolphin

Freshwater Invertebrates

Water Beetle (left) Water Boatman (right)

Although only a few aquatic insect species are found on the Islands, they are common in freshwater where predatory fish are not present. The most numerous insects are the tiny larvae of flies, especially non-biting midges. These are preyed upon by water beetles, which can be found swimming freely in most freshwater but seem particularly abundant in small ponds. Water boatmen also favour small ponds, where they feed on algae. The larvae of caddis-flies also graze on algae and can be found in great numbers on both ponds and stream beds. Caddis-fly larvae construct protective tubes from a variety of debris including sand, pond-weed and dead vegetation. The adult caddis-flies are generally found perched on vegetation by stream/pond banks. The only other common insects to be found in freshwater are the larvae of stoneflies. These can be found on the underside of rocks submerged in running water.

For further information see Insects of the Falkland Islands.