Crangon franciscorum: Difference between revisions
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The two most important natural environmental factors affecting the health of the shrimp population are water temperature and salinity. The shrimp thrive in [[brackish water]], with a preferred salinity of 14 parts per thousand when young to 24 parts per thousand when ready to spawn.<ref name = Ellinger/> In contrast, open ocean waters have a salinity of about 35 parts per thousand. The species prefers a water temperature of about 18 degrees centigrade, or 65 degrees Fahrenheit. <ref name = Ellinger/> Because these factors vary within the bay, based on the seasons each year, and the variations in the inflow of fresh water in heavy rainfall years as opposed to drought years, the shrimp migrate around the bay, seeking optimal conditions. When heavy flows of fresh water enter the bay, mature females migrate to the saltier parts of the central bay, or out the [[Golden Gate]] to the [[Gulf of the Farallones]].<ref name = Ellinger/> There, they mate with males who prefer a slightly saltier environment. The females then incubate from 2,000 to 8,000 eggs<ref name=PSMFC/> <ref name = Ellinger/> and when hatched, the young shrimp migrate back to the shallower and less salty estuaries around the bay.<ref name = Ellinger>{{cite news | last = Ellinger| first =Micky | title =From the Bottom Up: The Tiny Bay Shrimp Makes History | newspaper =Bay Nature | location = [[Berkeley, California]]| pages = | language = | publisher = | date =January 1, 2002 | url =http://baynature.org/article/from-the-bottom-up/| accessdate = July 2, 2016}}</ref> As the newly hatched shrimp develop and mature, they gradually migrate to "deeper, cooler and more saline water". <ref name=Estuary/> |
The two most important natural environmental factors affecting the health of the shrimp population are water temperature and salinity. The shrimp thrive in [[brackish water]], with a preferred salinity of 14 parts per thousand when young to 24 parts per thousand when ready to spawn.<ref name = Ellinger/> In contrast, open ocean waters have a salinity of about 35 parts per thousand. The species prefers a water temperature of about 18 degrees centigrade, or 65 degrees Fahrenheit. <ref name = Ellinger/> Because these factors vary within the bay, based on the seasons each year, and the variations in the inflow of fresh water in heavy rainfall years as opposed to drought years, the shrimp migrate around the bay, seeking optimal conditions. When heavy flows of fresh water enter the bay, mature females migrate to the saltier parts of the central bay, or out the [[Golden Gate]] to the [[Gulf of the Farallones]].<ref name = Ellinger/> There, they mate with males who prefer a slightly saltier environment. The females then incubate from 2,000 to 8,000 eggs<ref name=PSMFC/> <ref name = Ellinger/> and when hatched, the young shrimp migrate back to the shallower and less salty estuaries around the bay.<ref name = Ellinger>{{cite news | last = Ellinger| first =Micky | title =From the Bottom Up: The Tiny Bay Shrimp Makes History | newspaper =Bay Nature | location = [[Berkeley, California]]| pages = | language = | publisher = | date =January 1, 2002 | url =http://baynature.org/article/from-the-bottom-up/| accessdate = July 2, 2016}}</ref> As the newly hatched shrimp develop and mature, they gradually migrate to "deeper, cooler and more saline water". <ref name=Estuary/> |
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==Environmental stresses== |
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| ⚫ | When exposed to sewage in a laboratory, the species shows behavior described as "avoidance of the toxicant".<ref>{{cite book|url=https://books.google.com/books?id=DoE3gchMBv4C&pg=PA55&dq=Crangon+franciscorum&hl=en&sa=X&ei=EPQBVZqCAYjFggTDt4S4CQ&ved=0CDcQ6AEwBQ#v=onepage&q=Crangon%20franciscorum&f=false|title=Environmental Toxicology and Risk Assessment|publisher=[[ASTM International]]|volume=2|page=55-56|isbn=0803114850}}</ref> It is "sensitive to pollution in estuaries".<ref name=PSMFC/> |
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==Commercial fishing== |
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| ⚫ | When exposed to sewage in a laboratory, the species shows behavior described as "avoidance of the toxicant".<ref>{{cite book|url=https://books.google.com/books?id=DoE3gchMBv4C&pg=PA55&dq=Crangon+franciscorum&hl=en&sa=X&ei=EPQBVZqCAYjFggTDt4S4CQ&ved=0CDcQ6AEwBQ#v=onepage&q=Crangon%20franciscorum&f=false|title=Environmental Toxicology and Risk Assessment|publisher=[[ASTM International]]|volume=2|page=55-56|isbn=0803114850}}</ref> It is "sensitive to pollution in estuaries".<ref name=PSMFC/> |
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This species was by far the most common type of shrimp in [[San Francisco Bay]] in the 19th century, and was the most important species for its commercial shrimp fishery from the 1870s to the 1930s, accounting for about 90% of the shrimp catch.<ref name = Bonnot>{{cite news | last = Bonnot| first =Paul | title = The California Shrimp Industry| newspaper =Fish Bulletin No. 38 | location = Terminal Island, California| publisher =Division of Fish and Game of California | date =1932 | url =http://content.cdlib.org/view?docId=kt3f59n68z&brand=calisphere&doc.view=entire_text | accessdate = June 26, 2016}}</ref> |
This species was by far the most common type of shrimp in [[San Francisco Bay]] in the 19th century, and was the most important species for its commercial shrimp fishery from the 1870s to the 1930s, accounting for about 90% of the shrimp catch.<ref name = Bonnot>{{cite news | last = Bonnot| first =Paul | title = The California Shrimp Industry| newspaper =Fish Bulletin No. 38 | location = Terminal Island, California| publisher =Division of Fish and Game of California | date =1932 | url =http://content.cdlib.org/view?docId=kt3f59n68z&brand=calisphere&doc.view=entire_text | accessdate = June 26, 2016}}</ref> |
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Revision as of 05:05, 7 July 2016
| Crangon franciscorum | |
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| Species: | C. franciscorum
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| Binomial name | |
| Crangon franciscorum Stimpson, 1856
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Crangon franciscorum is a species of shrimp in the Crangonidae family which is endemic to California,[1] and found from Puget Sound in the north to San Diego, California in the south.[2] Its common names include bay shrimp, sand shrimp, common shrimp, grass shrimp, black shrimp, California shrimp and black tailed shrimp.[2]
This shrimp species is "an important part of the estuarine food web" in the greater San Francisco Bay.[3] It feeds on bivalves, amphipods and foraminiferins, and is prey for various fish,[3] including striped bass, white sturgeon, Pacific tomcod and shellfish such as Dungeness crab.[2] Its diet is "heavily influenced by predator size, temperature-salinity preferences, and prey availability."[3]
Life cycle
The shrimp are short-lived, with a lifespan ranging up to 18 months for males and 30 months for females. The males spawn once while longer lived females spawn twice. There is some evidence that the species may be protandrous hermaphrodites, which means that surviving males are transformed into females after one year of life. This may account for the longer lifespan of females.
The two most important natural environmental factors affecting the health of the shrimp population are water temperature and salinity. The shrimp thrive in brackish water, with a preferred salinity of 14 parts per thousand when young to 24 parts per thousand when ready to spawn.[4] In contrast, open ocean waters have a salinity of about 35 parts per thousand. The species prefers a water temperature of about 18 degrees centigrade, or 65 degrees Fahrenheit. [4] Because these factors vary within the bay, based on the seasons each year, and the variations in the inflow of fresh water in heavy rainfall years as opposed to drought years, the shrimp migrate around the bay, seeking optimal conditions. When heavy flows of fresh water enter the bay, mature females migrate to the saltier parts of the central bay, or out the Golden Gate to the Gulf of the Farallones.[4] There, they mate with males who prefer a slightly saltier environment. The females then incubate from 2,000 to 8,000 eggs[2] [4] and when hatched, the young shrimp migrate back to the shallower and less salty estuaries around the bay.[4] As the newly hatched shrimp develop and mature, they gradually migrate to "deeper, cooler and more saline water". [5]
Environmental stresses
When exposed to sewage in a laboratory, the species shows behavior described as "avoidance of the toxicant".[6] It is "sensitive to pollution in estuaries".[2]
Commercial fishing
This species was by far the most common type of shrimp in San Francisco Bay in the 19th century, and was the most important species for its commercial shrimp fishery from the 1870s to the 1930s, accounting for about 90% of the shrimp catch.[7]
References
- ^ Fransen, C.; De Grave, S. (2015). "Crangon franciscorum Stimpson, 1856". WoRMS. World Register of Marine Species. Retrieved March 12, 2015.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e "Shellfish of the Pacific Northwest" (PDF). SteamNet Project. Pacific States Marine Fisheries Commission. Retrieved July 4, 2016.
- ^ a b c Wahle, Richard A. (May 1985). "The Feeding Ecology of Crangon franciscorum and Crangon nigricauda in San Francisco Bay, California". Journal of Crustacean Biology. 5 (2). Crustacean Society: 311–326. Retrieved July 2, 2016.
- ^ a b c d e Ellinger, Micky (January 1, 2002). "From the Bottom Up: The Tiny Bay Shrimp Makes History". Bay Nature. Berkeley, California. Retrieved July 2, 2016.
- ^ Cite error: The named reference
Estuarywas invoked but never defined (see the help page). - ^ Environmental Toxicology and Risk Assessment. Vol. 2. ASTM International. p. 55-56. ISBN 0803114850.
- ^ Bonnot, Paul (1932). "The California Shrimp Industry". Fish Bulletin No. 38. Terminal Island, California: Division of Fish and Game of California. Retrieved June 26, 2016.
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