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Milt

From Wikipedia, the free encyclopedia
(Redirected from Soft roe)
For people named Milt, see Milt (name). For the orchid genus abbreviated Milt., see Miltonia. For the native Saxon word for the spleen, see Spleen.
Collecting Chinook salmon milt at a USFWS hatchery

Milt is the seminal fluid of fish, mollusks, and certain other water-dwelling animals. They reproduce by spraying this fluid which contains the sperm, onto roe (fish eggs). It can also refer to the sperm sacs or testes that contain the semen.

Milt (sometimes spelled melt[1][2]) or soft roe[3] also refers to the male genitalia of fish when they contain sperm, used as food. Many cultures eat milt, often fried, though not usually as a dish by itself. As a food item, milt is farmed year-round in nitrogen tanks, through hormone induction or photoperiod control.[4]

Production

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Production of milt may be affected by external stimuli. Goldfish are known to produce more milt when isolated from other males in their group[5][6], but will continue to produce high levels even when exposed to the scent of an unfamiliar male, suggesting that milt production is affected by close contact to rival males.[6] Milt production is also stimulated by the scent of a female fish.[5] Milt itself may contain pheremones that attract ovulating females.[7]

Intersex fish are less likely to release milt, or may fail to produce milt at all, due to their sperm ducts being blocked.[8] Even when intersex fish do produce milt, the sperm density is lower than normal, and the sperm that is present typiclaly has less motility than normal.[9]

Use in captive breeding

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At fish hatcheries, workers manually squeeze milt out of male fish, then use the milt to fertilize harvested eggs. This can be done to many fish while alive, and afterwards the fish can be released.[10] Pacific salmon hatcheries are an exception; the fish, returning from migration,[11] are killed via a guillotine and then the milt is poured over eggs, either by squeezing the male over them or by putting the milt in a dropper and squeezing it in.[12]

After collection, milt may be refrigerated for brief periods of time to increase sperm motility. Pacu milt, for example, will still have live sperm after 8 hours, and the motility will be higher compared to milt stored at room temperature. [13]

Milt as food

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Though many North Americans find the consumption of milt taboo,[14] it is popular in many Asian and European cuisines, and has been called "the male counterpart to caviar".[15]

Asian cuisine

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European cuisine

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Other uses

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Milt is highly absorbent of rare earth elements such as neodymium and iron. The heavier the rare earth element, the higher its affinity for milt.[19] Because of this, it has been proposed as an environmentally-friendly way to recover rare earth elements from waste.[19]

Chemical composition

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Herring milt is 82.5% water, 2% fat, 16.7% protein, and 2% ash for fish with 21% milt. Cod milt is 82% water, 1.1% fat, 14.5% protein, and 1.8% ash.[20]

See also

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Wikimedia Commons has media related to Milt.

References

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  1. ^ "Two quick recipes for Melts (aka soft herring roes)". The Fish Society. 4 August 2018. Archived from the original on 30 June 2022. Retrieved 2 August 2023.
  2. ^ Dick Lauder, Thomas (1877) [First published 1825]. Lochandhu: A Tale of the Eighteenth Century (Second ed.). Elgin: James Watson. p. 28. Retrieved 2 August 2023 – via Google Books. A mass of herring melts, tinged with the streams of claret, had fallen into his hair, and this, added to his temporary stupor, had led to the Doctor's mistake.
  3. ^ "Roe (food)". Encyclopedia Britannica.
  4. ^ "Vegetal Production". Gases in Agro-food processes. 2019. pp. 153–219. doi:10.1016/B978-0-12-812465-9.00013-X. ISBN 978-0-12-812465-9.
  5. ^ a b Stacey, Norm (December 2001). "Milt production in goldfish: regulation by multiple social stimuli". Comparative Biochemistry and Physiology Part C: Toxicology and Pharmacology. 130 (4): 467–476.
  6. ^ a b Fraser, Jane (1 October 2002). "Isolation increases milt production in goldfish". Journal of Experimental Zoology. 293 (5): 511–524.
  7. ^ Scott, Anne M. (9 July 2019). "Spremine in semen of male sea lamprey acts as a sex pheromone". PLOS One.
  8. ^ Harris, Catherine A. (8 October 2010). "The Consequences of Feminization in Breeding Groups of Wild Fish". Environmental Health Perspectives. 119 (3): 306–311.
  9. ^ Jobling, Susan (2002). "Wild intersex roach (Rotilus rotilus) have reduced fertility". Biology of Reproduction. 67 (2): 515–524.
  10. ^ "DEC Fish Hatchery FAQs". New York Department of Environmental Conservation.
  11. ^ Mitchell, Hannah (22 June 2022). "4 million mouths to feed: Life at the Dworshak Fish Hatchery". U.S. Army.
  12. ^ Schick, Tony (24 May 2022). "The U.S. has spent more than $2B on a plan to save salmon. The fish are vanishing anyway". Oregon Public Broadcasting.
  13. ^ Spica, L.N. (5 June 2024). "Viability duration of pacu (Piaractus mesopotamicus) milt stored under refrigeration". Brazilian Journal of Biology. 84.
  14. ^ Caterucci, Christina (18 April 2025). "Bad Seed". Slate.
  15. ^ Theriault Boots, Michelle (2 February 2015). "Alaska fish processors chase Japanese market for an unusual product-cod semen". Anchorage Daily News.
  16. ^ Corporation, Zojirushi America (2018-05-11). "An Acquired Taste of Japan – Shirako". Zojirushi Food & Culture Blog. Retrieved 2025-04-27.
  17. ^ "What is Milt: Dicovering the Weird Ingredient Made of Tuna Sperm". www.finedininglovers.com. Retrieved 2025-04-27.
  18. ^ Kirshenblatt-Gimblett, Barbara (12 April 2024). "An Ashkenazi delicacy made of fish sperm". Forward.
  19. ^ a b Takahashi, Yokio (9 December 2014). "Recovery and Separation of Rare Earth Elements Using Salmon Milt". Plos One.
  20. ^ Batista, I (2007). "By-catch, underutilized species and underutilized fish parts as food ingredients". Maximising the Value of Marine By-Products. pp. 171–195. doi:10.1533/9781845692087.2.171. ISBN 978-1-84569-013-7.
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