Life history and habitat Japanese eel

japanese eel

the japanese eel , other anguillid eels live in fresh water , estuaries feed , grow yellow eels number of years before begin mature , become silver eels. silver eels migrate out of fresh water ocean , start long journey spawning area. adult japanese eels migrate thousands of kilometers freshwater rivers in east asia spawning area without feeding. spawning area of species discovered in 1991 collecting small leptocephali 10 mm in size, , in 2005 same team of japanese scientists @ university of tokyo found more precise location of spawning based on genetically identified specimens of newly hatched preleptocephali 2 5 days old in small area near suruga seamount west of mariana islands (14–17° n, 142–143° e). in more recent years, more preleptocephali have been collected, , japanese eel eggs have been collected , genetically identified @ sea on research vessel. collections of eggs , hatched larvae have been made along western side of seamount chain of west mariana ridge. furthermore, mature adults of japanese eel , giant mottled eel captured using large midwater trawls in 2008 japanese scientists @ fisheries research agency. adults of japanese eel appear spawn in upper few hundred meters of ocean based on recent catches of spawning adults, eggs, , newly hatched larvae. timing of catches of eggs , larvae , ages of larger larvae have shown japanese eels spawn during few days before new moon period of each month of spawning season.

after hatching in ocean, leptocephali carried westward north equatorial current , northward kuroshio current east asia. in open ocean, larvae feed on marine snow, before metamorphose glass eel stage. glass eels enter estuaries , headwaters of rivers , many travel upstream. in fresh water , estuaries, diet of yellow eels consists of shrimp, other crustaceans, aquatic insects, , small fishes.

the japanese eel population, along anguillid eel populations worldwide, have declined drastically in recent years, presumably due combination of overfishing , habitat loss or changing water conditions in ocean interfering spawning , transport of leptocephali. in case of japanese eel, spawning affected north-south shifts of salinity front created area of low-salinity waters resulting tropical rainfall. front thought detected adult spawning eels , affect latitudes @ spawn. northward shift in front occurred on past 30 years appears have occurred, cause more larvae retained in eddies offshore in region east of taiwan, , southward shifts in salinity front have been observed in recent years increase southward transport mindanao current flows celebes sea. these types of unfavorable larval transport thought reduce recruitment success of japanese eels reach river mouths glass eels.