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Coneix el riu

There are some 32 native fish species in Catalonia that live, at least some of their lives in fresh water. There are also at least 25 non-native or allochthonous species that are well-established here. The dominant species vary along the course of the river. In the same river basin different fish will be found living in specific areas that are defined by their environmental requirements: temperature, the speed of the river, the type of substrate, etc.

Many native fish are in regression and in a fragile state of existence. All are affected, in one way or another, by problems related to the over-use of water, poor connectivity and competition with invasive species.

Obstacles to Fish Migration

The movements of fish are affected by water shortages, pollution, and hydraulic structures, such as dams, locks, fords, walkways, irrigation pumps, etc.

Resclosa

A weir preventing fish migration. Illustration by Toni Llobet at Ordeix i Bretxa (2007).

How to facilitate Fish Migration

In order to improve connectivity for fish in rivers, ponds and wetlands, one option is to either totally or partially remove the obstacles in their path, or if this is not viable, then constructing special devices to aid fish as they travel up and downstream is an alternative.

Resclosa enderrocada

The destruction of a river barrier to facilitate the movement of fish.

Rampa de peixos

A fish ramp at a weir. Illustration by Toni Llobet at Ordeix i Bretxa (2007).

Different Devices for aiding Fish Movements

There are many different devices for aiding the movement of fish. Some are more natural by design (fish ramps and lateral river by-passes) and are generally more efficient, while others are more technical in design and that require more complex maintenance (pool passes, fish lifts and fish locks, among others).

Fish ramp

Rampa de peixos

Lateral river by-pass

Riu lateral

Pool pass

Safareigs successius

Fish lift

Ascensor

Catadromous Fish

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The eel is the only catadromous fish in this country. It spends most of its life in rivers, ponds or wetlands, in fresh or salt water environments, it only returns to the sea, and then to the Atlantic Ocean, to reproduce. It swims thousands of kilometers. This fish would today be thriving in many rivers if it were not for over-fishing and the barrier effect of dams and locks.

European eel

European eel
Anguilla anguilla

Anadromous Fish

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Anadromous fish spend most of their lives in the sea, where they grow, before returning to continental waters to spawn and reproduce.

	Allis shad

Allis shad
Alosa alosa

	Twaite shad

Twaite shad
Alosa fallax

	European sturgeon

European sturgeon
Acipenser sturio

	Sea lamprey

Sea lamprey
Petromyson marinus

Amphidromous Fish

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Amphidromous fish (although this classification is somewhat controversial and, in general, are also considered catadromous) move between the sea, where they usually breed, and rivers and marshes, where they go to feed.

	Thinlip mullet

Thinlip mullet
Liza ramada

	Thicklip grey mullet

Thicklip grey mullet
Chelon labrosus

	Striped mullet

Striped mullet
Mugil cephalus

	Big-scale sand smelt

Big-scale sand smelt
Atherina boyeri

	European flounder

European flounder
Platichthys flesus

	Black-striped pipefish

Black-striped pipefish
Sygnathus abaster

	Golden grey mullet

Golden grey mullet
Liza aurata

	Leaping mullet

Leaping mullet
Liza saliens

	European bass

European bass
Dicentrarchus labrax

Potamodromous Fish

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Potamodromous fish migrate, especially in order to reproduce. They swim upstream or into flooded river banks to spawn, while looking for the best places for their eggs and their newly-born offspring: in streams, ponds or marshes, whether permanent or temporary.

	Mediterranean barbel

Mediterranean barbel
Barbus meridionalis

	Catalan barbel

Catalan barbel
Barbus haasi

	Ebro barbel

Ebro barbel
Luciobarbus graellsii

	Catalan chub

Catalan chub
Squalius laietanus

	Iberian chub

Iberian chub
Squalius pyrenaicus

	Bermejuela

Bermejuela
Achondrostoma arcasii

	Ebro nase

Ebro nase
Pseudochondrostoma miegii

	Freshwater blenny

Freshwater blenny
Salaria fluviatilis

	European bullhead

European bullhead
Cottus gobio

	Western three-spined stickleback

Western three-spined stickleback
Gasterosteus gymnurus

	Brown trout

Brown trout
Salmo trutta

	Iberian loach

Iberian loach
Cobitis paludica

	Spanish toothcarp

Spanish toothcarp
Aphanius iberus

	Valencia toothcarp

Valencia toothcarp
Valencia hispanica

Invasive Fish Species

Many exotic fish species that were once owned as pets have been released and they now live in local rivers. These fish are a serious issue for autochthonous species as, among other reasons, they are highly competitive and easily replace native species at risk of extinction. Invasive species need to be controlled and we need to ensure that more fish of this type are not introduced.

	Common rudd

Common rudd
Scardinius erythrophthalmus

	Stone loach

Stone loach
Barbatula barbatula

Black bullhead

Black bullhead
Ameiurus melas

	Stone moroko

Stone moroko
Pseudorasbora parva

	Eastern mosquitofish

Eastern mosquitofish
Gambusia holbrooki

	Pumpkinseed

Pumpkinseed
Lepomis gibbosus

	European perch

European perch
Perca fluviatilis

	Rainbow trout

Rainbow trout
Oncorhynchus mykiss

Northern pike

Northern pike
Esox lucius

	Common bleak

Common bleak
Alburnus alburnus

	Goldfish

Goldfish
Carassius auratus

	Common carp

Common carp
Cyprinus carpio

	Iberian gudgeon

Iberian gudgeon
Gobio lozanoi

	Adour minnow

Adour minnow
Phoxinus bigerri

	Common roach

Common roach
Rutilus rutilus

	Wels catfish

Wels catfish
Silurus glanis

Zander

Zander
Sander lucioperca

	Brook trout

Brook trout
Salvelinus fontinalis

	Tench

Tench
Tinca tinca

	Largemouth bass

Largemouth bass
Micropterus salmoides

Illustrations: © Toni Llobet