Aquarium

The underwater world of the Sihl

Seven native fish species and one crab species still live in the Sihl. The original index species, the river trout, is now a rarity, while the barbel and the chub are commonplace. You will find the following species in the aquarium.

Chub

Rounded head, black-edged scales, silvery flanks, often with a golden lustre.
Chub are fairly tolerant of environmental toxins, so they are often the most common species in polluted waters.

River trout

Dark and red spots with light edges, with an adipose fin between the dorsal and caudal fins.
River trout are sensitive to hormone pollution in water, which can cause males to turn into females and vice versa.

Barbel

Thick-lipped mouth, fleshy barbels on the sides of the mouth.
Barbel roe is poisonous and can cause vomiting and diarrhoea.

Bullhead

No scales, toad-like head with a broad mouth, large fan-like pectoral fins.
Bullheads lack a swim bladder and therefore move around the substrate rather than swimming in open water.

Gudgeon

Obtuse snout, two short labial barbels at the corners of the mouth, row of dark patches along the flanks.
These patches act as excellent camouflage on sandy and gravelly substrates.

Common minnow

Lateral line generally extends only to the middle of the body, with a golden longitudinal stripe above.
Common minnows have excellent senses of smell and hearing. If eaten, they emit an alarm substance, which deters others of their species from that location.

Loach

Elongated body, laterally compressed at the rear, six barbels on their fleshy upper lips.
Loach use the barbels as olfactory and gustatory organs when searching for food.

European crayfish

Generally dark but highly variable, blue specimens are relatively common.
European crayfish hibernate and are also able to survive out of water for short periods. Native crayfish are severely threatened by the introduction of foreign crayfish varieties. North American signal crayfish carry the dangerous crayfish plague but are themselves immune to it. The disease is, however, fatal to native crayfish.