Editing Plankton (section)

===Ichthyoplankton===
{{main|Ichthyoplankton}}
[[File:Salmonlarvakils 2.jpg|thumb|Salmon egg hatching into a ''sac fry''. In a few days, the sac fry will absorb the yolk sac and start feeding on smaller plankton.]]

[[Ichthyoplankton]] are the [[Fish eggs|eggs]] and [[larvae]] of fish. They are mostly found in the sunlit zone of the [[water column]], less than 200 metres deep, which is sometimes called the [[epipelagic]] or [[photic zone]]. Ichthyoplankton are [[planktonic]], meaning they cannot swim effectively under their own power, but must drift with the ocean currents. Fish eggs cannot swim at all, and are unambiguously planktonic. Early stage larvae swim poorly, but later stage larvae swim better and cease to be planktonic as they grow into [[Juvenile fish|juveniles]]. Fish larvae are part of the [[zooplankton]] that eat smaller plankton, while fish eggs carry their food supply. Both eggs and larvae are themselves eaten by larger animals.<ref name=NOAA>[http://swfsc.noaa.gov/textblock.aspx?Division=FRD&id=6210 What are Ichthyoplankton?] Southwest Fisheries Science Center, NOAA. Modified 3 September 2007. Retrieved 22 July 2011.</ref><ref name=Moser2006>{{Cite book|url=https://books.google.com/books?id=Qdzg0Vfql2sC&pg=PA269|title = The Ecology of Marine Fishes: California and Adjacent Waters|pages = 269–319|isbn = 9780520932470|last1 = Allen|first1 = Dr. Larry G.|last2 = Horn|first2 = Dr. Michael H.|date = 15 February 2005| publisher=University of California Press }}</ref> Fish can produce high numbers of eggs which are often released into the open water column. Fish eggs typically have a diameter of about {{convert|1|mm}}. The newly hatched young of oviparous fish are called [[larva]]e. They are usually poorly formed, carry a large [[yolk sac]] (for nourishment), and are very different in appearance from juvenile and adult specimens. The larval period in oviparous fish is relatively short (usually only several weeks), and larvae rapidly grow and change appearance and structure (a process termed [[metamorphosis]]) to become juveniles. During this transition larvae must switch from their yolk sac to feeding on [[zooplankton]] prey, a process which depends on typically inadequate zooplankton density, starving many larvae. In time fish larvae become able to swim against currents, at which point they cease to be plankton and become [[juvenile fish]].