Ichthyoplankton

Fish produce many eggs, typically about 1mm across, and usually release them into the open water column

Diagram of a fish egg: A. vitelline membrane B. chorion C. yolk D. oil globule E. perivitelline space F. embryo

Ichthyoplankton (from Greek: ἰχθύς, ikhthus, "fish"; and πλαγκτός, planktos, "drifter"^[1]) are the eggs and larvae of fish. They are usually 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 juveniles. Fish larvae are part of the zooplankton that eat smaller plankton, while fish eggs carry their own food supply. Both eggs and larvae are themselves eaten by larger animals.^[2][3]

Fish can produce high numbers of eggs which are often released into the open water column. Fish eggs typically have a diameter of about 1 millimetre (0.039 in). The newly hatched young of oviparous fish are called larvae. 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.

Ichthyoplankton can be a useful indicator of the state and health of an aquatic ecosystem.^[2] For instance, most late stage larvae in ichthyoplankton have usually been predated, so ichthyoplankton tends to be dominated by eggs and early stage larvae. This means that when fish, such as anchovies and sardines, are spawning, ichthyoplankton samples can reflect their spawning output and provide an index of relative population size for the fish.^[3] Increases or decreases in the number of adult fish stocks can be detected more rapidly and sensitively by monitoring the ichthyoplankton associated with them, compared to monitoring the adults themselves. It is also usually easier and more cost effective to sample trends in egg and larva populations than to sample trends in adult fish populations.^[3]

History

Interest in plankton originated in Britain and Germany in the nineteenth century when researchers discovered there were

Fish About fish Diversity Ethnoichthyology Evolution Diseases and parasites Fisheries Fishing Fish as food Fear of fish FishBase Fish kill Hypoxia in fish Ichthyology Anatomy and physiology Fish anatomy Fish physiology Anguilliformity Bone dermal intramembranous ossification Cleithrum Chromatophore Fins dorsal fin Gill branchial arch gill raker gill slit pharyngeal arch pharyngeal slit Glossohyal Hyomandibula Jaw pharyngeal jaw Leydig's organ Mauthner cell Meristics Operculum papillare Papilla Photophore Physoclisti Physostome Pseudobranch Shark cartilage Scales ganoine Spiral valve Suckermouth Swim bladder Teeth pharyngeal teeth shark teeth Fish age Digital Library Sensory systems Sensory systems in fish Ampullae of Lorenzini Barbel Hydrodynamic reception Electrocommunication Electroreception Jamming avoidance response Lateral line Otolith Passive electrolocation Capacity for pain Schreckstoff Surface wave detection Vision Weberian apparatus Reproduction Fish reproduction Bubble nest Clasper Egg case Fish development Ichthyoplankton Juvenile fish Life history theory Milt Mouthbrooder Polyandry in fish Pregnancy Roe Sequential hermaphroditism Spawning Spawning triggers Locomotion Fish locomotion Fin and flipper locomotion Amphibious fish Walking fish Flying fish Undulatory locomotion Tradeoffs for locomotion in air and water RoboTuna Other behaviour Aquatic predation Aquatic respiration Bait ball Bottom feeders Cleaner fish Diel vertical migration Electric fish Filter feeders Forage fish Migrating fish Paedophagy Predatory fish Salmon run Sardine run Scale eaters Schooling fish Sleep in fish Venomous fish Fish intelligence Habitats Coastal fish Coldwater fish Coral reef fish Deep sea fish Demersal fish Euryhaline fish Freshwater fish Groundfish Marine habitats Pelagic fish Tropical fish Wild fish Other types Bait fish Coarse fish Farmed fish Game fish Genetically modified Hallucinogenic fish Oily fish Rough fish Whitefish Weird fish Fish groups Predatory fish billfish mackerel salmon sharks tuna Forage fish anchovy herring sardine Demersal fish cod flatfish pollock rays Lists Aquarium fish Blind fish Fish common names Fish families Fish on stamps Ichthyology terms Large fish Threatened rays Threatened sharks Prehistoric fish more lists...

Eggs List of egg topics Types Bird Fish and amphibian Monotreme Fossil record Fossil (pathological) Cephalopod Fish Reptile (dinosaur) Biology Embryo Ichthyoplankton Ootheca Oviparity Spawn Zygote Components Yolk White Shell As food List of dishes Trophic egg Boiled Custard desserts Eggs Benedict Fried Omelette Poached Pickled Roe Scotch Scrambled Smoked Soufflé In culture Easter egg Egging Fabergé egg Humpty Dumpty Oomancy Ovo vegetarianism Category

Plankton About plankton Algal bloom CLAW hypothesis High lipid content microalgae Holoplankton Meroplankton Milky seas effect Paradox of the plankton Planktology Red tide Spring bloom Thin layers More... By size Eukaryotic picoplankton Heterotrophic picoplankton Microphyte (microalgae) Nanophytoplankton Photosynthetic picoplankton Picobiliphyte Picoeukaryote Picoplankton Bacterioplankton Bacteriastrum Aeromonas salmonicida Cyanobacteria Cyanobiont Cyanotoxin Enteric redmouth disease Flavobacterium Flavobacterium columnare Pelagibacter ubique Marine bacteriophage SAR11 clade Streptococcus iniae Phytoplankton Auxospore Axodine Chaetoceros Chaetocerotaceae Coccolithophore Emiliania huxleyi Eustigmatophyte Frustule Heterokont Nannochloropsis Navicula Prasinophyceae Raphidophyte Thalassiosira pseudonana Diatom orders Centrales Pennales (Classes: Coscinodiscophyceae Fragilariophyceae Bacillariophyceae) Flagellates Brevetoxin Choanoflagellates Dinoflagellates Flagellum Pfiesteria piscicida Saxitoxin Symbiodinium Velvet (fish disease) Zooplankton Chaetognatha Ciguatera Ctenophora Gelatinous zooplankton Hunting copepods Ichthyoplankton Jellyfish Marine larvae Crustacean larvae Salmon louse Sea louse Copepod orders Calanoida Cyclopoida Harpacticoida Monstrilloida Poecilostomatoida Siphonostomatoida More... Related topics Aeroplankton Algaculture Algal mat Algal nutrient solutions Artificial seawater Autotrophs Biological pump Diel vertical migration Dimethylsulfoniopropionate f-ratio Fish diseases and parasites Heterotroph HNLC Macroalgae Manta trawl Marine mucilage Microbial mat Ocean acidification Primary production Stromatolite Tychoplankton Zoid C-MORE CPR AusCPR MOCNESS SCAR

• Ichthyoplankton Survey Methodology Presentation by Yoshinobu Konishi, SEAFDEC-MFRDMD.
• Salmon Eggs Hatching at the Seymour Hatchery Youtube video.

External links

• Ichthyoplankton Information System Alaska Fisheries Center, NOAA.
• Early life history section American Fisheries Society.
• Larval Fish Laboratory Colorado State University.
• Recent advances in the study of fish eggs and larvae Sci. Mar., 70S2: 2006.
• Guides and keys to larval and early juvenile fishes Warner College of Natural Resources, Colorado State University.

• Ahlstrom, Elbert H. and Moser, H. Geoffrey (1976) "Eggs and larvae of fishes and their role in systematic investigations in fisheries" Revue des Travaux de l'Institut des Pêches Maritimes, 40(3-4): 379–398.
• Balon, Eugene K. (1990) "Epigenesis of an epigeneticist: the development of some alternative concepts on the early ontogeny and evolution of fishes Guelph Ichthyology Reviews, 1: 1–48.
• Blaber, Stephen J. M. (2000) Tropical estuarine fishes: ecology, exploitation and conservation John Wiley and Sons, Page 153–156. ISBN 978-0-632-05655-2.
• Browman, Howard I. and Skiftesvik, Anne Berit (2003) The Big Fish Bang: Proceedings of the 26th Annual Larval Fish Conference Institute of Marine Research. ISBN 978-82-7461-059-0.
• Finn, Roderick Nigel and Kapoor, B. G. (2008) Fish larval physiology Science Publishers.ISBN 9781578083886.
• Cowan, J.H., Jr. and R.F. Shaw (2002) "Recruitment" Chap. 4. pp. 88–111. In: L.A. Fuiman and R.G. Werner (eds.) Fishery Science: The unique contributions of early life stages, John Wiley and Sons. ISBN 978-0-632-05661-3.+
• Chambers RC and Trippel EA (1997) Early life history and recruitment in fish population Springer. ISBN 978-0-412-64190-9.
• Houde ED (2010) "Fish Larvae" Page 286–295. In: JH Steele, SA Thorpe and KK Turekian, Marine Biology, Academic Press. ISBN 978-0-08-096480-5.
• Kendall Jr., Arthur W. (2011) Identification of Eggs and Larvae of Marine Fishes 東海大学出版会, 2011. ISBN 978-4-486-03758-3.
• Miller, Bruce S. and Kendall, Arthur W. (2009) Early life history of marine fishes University of California Press. ISBN 978-0-520-24972-1.
• Miller TJ (2002) "Assemblages, Communities, and Species Interactions" Pages 183–205. In: Lee A. Fuiman and Robert G. Werner, Fishery science: the unique contributions of early life stages, John Wiley and Sons. ISBN 978-0-632-05661-3.

References

Notes

See also

• Coregonus maraena eggs about one month after fertilization

• Salmon eggs in different stages of development.

• Male goldfish encourage a spawning female and discharge sperm to externally fertilize her eggs

• Within days, the vulnerable goldfish eggs hatch into larvae, and rapidly develop into fry

• Atlantic herring eggs, with a newly hatched larva

• Freshly hatched herring larva in a drop of water compared to a match head.

• Early stage herring larvae imaged in situ with yolk remains

• A 2.7mm long larva of the ocean sunfish, Mola mola,

• Late stage lanternfish larva

• A 9mm long late stage scaldfish larva

• Larvae of a conger eel, 7.6 cm

Gallery

The fish they chose to investigate was the yellow tang, because when a larva of this fish find a suitable reef it stays in the general area for the rest of its life. Thus, it is only as drifting larvae that the fish can migrate significant distances from where they are born.^[16] The tropical yellow tang is much sought after by the aquarium trade. By the late 1990s, their stocks were collapsing, so in an attempt to save them nine marine protected areas (MPAs) were established off the coast of Hawaii. Now, through the process of larval drift, fish from the MPAs are establishing themselves in different locations, and the fishery is recovering.^[16] "We've clearly shown that fish larvae that were spawned inside marine reserves can drift with currents and replenish fished areas long distances away," said one of the authors, the marine biologist Mark Hixon. "This is a direct observation, not just a model, that successful marine reserves can sustain fisheries beyond their borders."^[16]

In 2010, a group of scientists reported that fish larvae can drift on ocean currents and reseed fish stocks at a distant location. This finding demonstrates, for the first time, what scientists have long suspected but have never proven, that fish populations can be connected to distant populations through the process of larval drift.^[14]

Fish larvae develop first an ability to swim up and down the water column for short distances. Later they develop an ability to swim horizontally for much longer distances. These swimming developments affect their dispersal.^[15]

The larvae of the yellow tang can drift more than 100 miles and reseed in a distant location.^[14]

Dispersal

The most effective predators are about ten times as long as the larvae they predate on. This is true regardless of whether the predator is a crustacean, a jellyfish, or a fish.^[13]

^[7]) 70%.Engraulis encrasicolus and South African anchovy (^[12] were responsible for 10%Peruvian anchoveta while ^[12]) were responsible for 28% of the mortality in their own egg population,Engraulis mordax Fish also cannibalise their own eggs. For example, separate studies found northern anchovy (^[11] in a herring spawning area with 20,000 herring eggs in their stomachs, and concluded that they could predate half of the total egg production.cod Another study found ^[8] eggs back in 1922.herring were observed satiating themselves with haddock fish eggs and larvae. For example, predate Adult fish also ^[10] Because they are so abundant, marine invertebrates inflict high overall mortality rates.^[9][8].krill and marine snails, amphipods, jellyfish, arrow worms, copepods, such as marine invertebrates For example, they may be fed upon by [7]

Survival

The spawn (eggs) of a clownfish. The black spots are the eyes developing. Salmon eggs. The growing larvae can be seen through the transparent egg envelope.	Developmental stages according to Kendall et al. 1984[6]				Salmon egg hatching. The larva has broken through and is discarding the egg envelope. In about 24hrs it will absorb the remaining yolk sac and become a juvenile.
	Main stages	Egg stage	Spawning to hatching. This stage is used instead of using an embryonic stage because there are aspects, such as those to do with the egg envelope, that are not just embryonic aspects.
		Larval stage	From hatching till all fin rays are present and the growth of fish scales has started (squamation). A key event is when the notochord associated with the tail fin on the ventral side of the spinal cord develops flexion (becomes flexible).	The larval stage can be further subdivided into preflexion, flexion, and postflexion stages. In many species, the body shape and fin rays, as well as the ability to move and feed, develops most rapidly during the flexion stage.
		Juvenile stage	Starts with all the fin rays being present and scale growth underway, and completes when the juvenile becomes sexually mature or starts interacting with other adults.
	Transitional stages	Yolk-sac larval stage	From hatching to absorption of the yolk-sac
		Transformation stage	From larva to juvenile. This metamorphosis is complete when the larva develops the features of a juvenile fish.

Ichthyoplankton researchers generally use the terminology and development stages introduced in 1984 by Kendall and others.^[3] This consists of three main developmental stages and two transitional stages.^[6]

Developmental stages

• Plankton pumps: Another method of collecting ichthyoplankton is to use a Continuous Underway Fish Egg Sampler (CUFES). Water from a depth of about three metres is pumped onto the vessel and filtered with a net. This method can be used while the vessel is underway.^[5]

• Neuston net tows are often made at or just below the surface using a nylon mesh net fitted to a rectangular frame
• The PairoVET tow, used for collecting fish eggs, drops a net about 70 metres into the sea from a stationary research vessel and then drags it back to the vessel.
• Ring net tows involve a nylon mesh net fitted to a circular frame. These have largely been replaced by bongo nets, which provide duplicate samples with their dual-net design.
• The bongo tow drags nets shaped like bongo drums from a moving vessel. The net is often lowered to about 200 metres and then allowed to rise to the surface as it is towed. In this way, a sample can be collected across the whole photic zone where most ichthyoplankton is found.
• MOCNESS tows and Tucker trawls utilize multiple nets that are mechanically opened and closed at discrete depths in order to provide insights into the vertical distribution of the plankton
• The manta trawl tows a net from a moving vessel along the surface of the water, collecting larvae, such as grunion, mahi-mahi, and flying fish which live at the surface.

After the tow the plankton is flushed with a hose to the cod end (bottom) of the net for collection. The sample is then placed in preservative fluid prior to being sorted and identified in a laboratory.^[5]

• There are many types of plankton tows:^[5]

Research vessels collect ichthyoplankton from the ocean using fine mesh nets. The vessels either tow the nets through the sea or pump sea water onboard and then pass it through the net.^[5]

Retrieving a plankton sample

Sampling methods

^[3].fish stocks of spawning abundance, then the samples could indicate the relative size or quantitatively Around the beginning of the twentieth century, research interest in ichthyoplankton became more general when it emerged that, if ichthyoplankton was sampled ^[4], living in the open water column like other plankton.pelagic eggs, drifting in the water. This established that fish eggs could be cod around the Norwegian coast. Sars found fish eggs, particularly fisheries to investigate G. O. Sars marine biologist Ichthyoplankton research started in 1864 when the Norwegian government commissioned the [3]