The toxostome -wherever it may roam

The toxostome -wherever it may roam

Most British anglers have probably never heard of the toxostome. Indeed, many of those who fish its native waters and catch this little fish have probably never come across the name either (it comes from the scientific name toxostoma, meaning hard mouth).

It is a dace-like fish which appears mainly in the waters of southern Europe, particularly in the mountain streams of southern France and northern Spain. It failed to penetrate northern freshwaters in time to colonize the British Isles before they were isolated from mainland Europe. As a result the fish appears in different countries under quite a variety of different names. Although this is a common problem with many freshwater fish in southern Europe, this species’ similarity to the nase, along with the appearance of a great many toxostome hybrids, have confused the issue more than most.

On the move

In more recent years the toxostome has spread into central Europe, mainly because small numbers have been accidentally

In western France, where it occurs mainly in the upper reaches of the Loire and Allier rivers, it is called the soiffe. This same fish also reaches the rivers of the Pyrenees and central Spain and Portugal — but here it has been dubbed the madrilla.

Some experts consider a similar fish in eastern Spain to be a distinct subspecies of the madrilla or soiffe or toxostome.

In Germany the fish’s resemblance to the more common nase has led to it being called the nasling, while a similar fish appearing in the rivers of northern Italy has been christened the casca.

Hybrids between the toxostome and nase are common, with variations also occurring in the Balkans and in Caucasian rivers.

Many of these hybrids have characteristics so similar to those of the native European nase that some fishing texts refer to the toxostome as merely a south European or south-west European nase.

Small scale fish

For British anglers the toxostome, with its compressed blade-like body, can best be likened to a dace. However, it has slightly smaller body scales and rather more of them (52-56 in the lateral line as opposed to the dace’s 48-51). Also, the toxostome’s anal fin is slightly longer, with 10 or 11 branched rays, against 8 or 9 rays on the dace.

The snout is long and fleshy with a horseshoe-shaped mouth on the underside. The lips are very tough with sharp edges that it uses when feeding – scraping encrusting algae off river bed rocks.

Its back is greyish with a blue-green tint and the sides and belly are brilliant silver. The ventral fins are pale yellow and there is a dusky band running from head to tail just above the lateral line.

Toxostome home

The toxostome’s natural habitat is the clear well-oxygenated rivers and streams found in mountain districts. Occasionally it makes a home in unpolluted lakes or in upland areas which haven’t been enriched by agricultural fertilizers or overgrown with vegetation.

The fish does not migrate to spawn, but instead makes short journeys upstream before spawning in the spring, when the water reaches a temperature of 13°C (55°F). A study carried out on the River Doubs in France noted resident toxostome spawning in mid-April. The eggs, shed over shallow gravel beds, hatch in 12-15 days. Each female produces anything from 2000 to 3500 eggs, depending on her size. Many are taken by predators before they hatch.