Results:

Species Groups: Pisces

Migration between fresh- and saltwater

GROMS home > Results > Species Groups > Pisces > Migration between fresh- and saltwater

Pisces: Migration between fresh- and saltwater

Migration between fresh- and saltwater - diadromous species
A considerable number of fish species cross the barrier between salt- and freshwater, either to spawn in saltwater (catadromous), or to spawn in rivers (anadromous). Eels are catadromous, and the spawning journey of the European eel (Anguilla anguilla) to the mysterious spawning grounds deep in the Sargasso Sea is a well-known example. The area was found indirectly, by painstaking mapping of larvae of distinct sizes, thereby circling in the breeding area (Schmidt 1923). The upstream migrations of anadromous salmon are easier to observe. Huge numbers of fishes attracted fishermen and predators in many temperate river systems. The productivity was enormous, and during the U.S. depression, Pacific salmon sold as "poverty steak" for 10 cents a pound. In 1993, prices were up to 8 dollars a pound, due to damming of the Sacramento river (Dingle 1996). Winter runs up the Sacramento sustained a harvest to over a million fish, but dropped to a pitiful 191 fish in 1991. This decline is clearly caused by the Red Bluff Diversion Dam, and survival of the salmon populations is now totally dependent on the amount of water allotted for the spawning runs (l.c., p. 408). Similar declines are observed throughout industrialised countries, some of which have now started expensive rehabilitation programs (Neumann et al. 1998). The most recent dramatic decline is observed in sturgeons (Acipenseriformes). Within the former Soviet Union, a system of hatcheries compensated partially the losses caused by large river dam projects. Today, the operation of hatcheries is ineffective, and illegal fisheries are driving several species towards the brink of extinction. 18 anadromous sturgeon species have now been listed on Appendix II of CMS, and a recent total catch ban of three nations bordering the Caspian Sea will hopefully help to save the species at the last minute (see references in Figures A2.84 and A2.85).

Finally, there is amphidromous migration; this refers to fish that migrate from freshwater to the sea or vice versa. This migration is not for breeding, but mainly associated with feeding or because of climatic reasons. Examples are the endangered sawfishes (Pristis spp.), which are now a target species for industrial fisheries (see Table 4.11).

All species depending on freshwater are suffering from degradation of river habitats and pollution. The "Living Planet Report" identified freshwater systems among the most endangered habitats (Loh et al. 1998). Finally, it needs to be kept in mind that marine fisheries may jeopardise conservation efforts: The bycatch of industrial fisheries targetting small species for fishmeal (known in German as "Gammelfischerei") will affect any juveniles of anadromous species trying to grow in the sea.

Tab. 4.12: Migratory fish species, red-listed as "Data Deficient". (Red List 2000: Hilton-Taylor 2000). Research is needed to assess their threat status, because many of these species are probably endangered. Many of these species are widely distributed, as indicated by the number of range states, as calculated according to the Red List 2000. Therefore, they probably cross international boundaries during migration.			Tab. 4.12: Wandernde Fischarten mit Rote-Liste-Status "Daten defizitär" (Red List 2000: Hilton-Taylor 2000). Hier besteht dringender Forschungsbedarf, da viele dieser Arten möglicherweise gefährdet sind. Die hohe Anzahl der Verbreitungsstaaten (berechnet nach Rote Liste 2000) zeigt, daß viele dieser Arten weit verbreitet sind. Daher überqueren sie wahrscheinlich während ihrer Wanderung internationale Grenzen.
Class: Order	Family	Scientific name		Common name	Migration	Range states RL 2000
Actinopterygii:
Clupeiformes	Clupeidae	Alosa fallax		Killarney shad	anadromous	36
	Clupeidae	Alosa pontica		Black Sea herring	anadromous	15
	Clupeidae	Clupeonella cultriventris		Azov Sea sprat	anadromous	11
	Clupeidae	Alosa alosa		Alice shad	anadromous	19
	Engraulidae	Thryssa scratchleyi		Freshwater anchovy	catadromous	1
Cypriniformes	Cyprinidae	Aspius aspius		Aral asp	potamodromous	31
	Cyprinidae	Chalcalburnus chalcoides		Caspian shemaya	potamodromous	9
	Cyprinidae	Rutilus frisii		Kutum	anadromous	11
Perciformes	Eleotridae	Eleotris sandwicensis		Sandwich Island sleeper	amphidromous	1
	Gobiidae	Luciogobius pallidus			amphidromous	1
	Gobiidae	Lentipes concolor		Oopu alamoo	amphidromous	1
	Gobiidae	Awaous guamensis		Oopu Nakea	amphidromous
	Gobiidae	Sicyopterus halei		Red-tailed goby	amphidromous	1
	Gobiidae	Sicyopus jonklaasi		Lipstick goby	amphidromous	1
	Percichthyidae	Macquaria australasica		Macquarie perch	potamodromous	1
	Terapontidae	Scortum hillii		Green-hide jack	potamodromous
Salmoniformes	Galaxiidae	Aplochiton taeniatus			amphidromous
	Osmeridae	Osmerus eperlanus		European smelt	anadromous	16
	Salmonidae	Coregonus peled		Northern whitefish	anadromous	8
	Salmonidae	Coregonus albula		Vendace	anadromous	18
	Salmonidae	Coregonus lavaretus lavaretus		Baltic whitefish	anadromous
	Salmonidae	Coregonus oxyrinchus		Houting	anadromous	15
	Salmonidae	Coregonus nasus		Broad whitefish	anadromous	14
	Salmonidae	Stenodus leucichthys		Connie	anadromous	6
	Salmonidae	Coregonus pidschian		Ob� whitefish	anadromous	8
Synbranchiformes	Synbranchidae	Ophisternon candidum		Blind cave eel	potamodromous	1
Cephalaspidomorphi:
Petromyzontiformes	Petromyzontidae	Eudontomyzon mariae		Ukrainian brook lamprey	limnodromous	14
	Petromyzontidae	Mordacia lapicida		Chilean lamprey	anadromous	1
Elasmobranchii:
Rajiformes	Potamotrygonidae	Potamotrygon motoro		South American freshwater stingray	potamodromous	5

• Maps

This document is part of the publication "Riede, K. (2001): The Global Register of Migratory Species � Database, GIS Maps and Threat Analysis. Münster (Landwirtschaftsverlag), 400 pp." + CD (see copyright), orders: http://www.lv-h.de/bfn .