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New recruits
Pink shrimp larvae are released in early spring, and are planktonic for about 4-6 months before settling to the bottom. While in the planktonic stage, they pass through a series of zoeal growth phases or "instars" before they become recognizable as small shrimp. These "zero age" shrimp are often found higher in the water column than their adult counterparts. |
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A zero age shrimp |
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Maturing shrimp
After one year, pink shrimp are between 13 and 19 mm in carapace length and are reproductively mature. Oregon’s pink shrimp, like other Pandalid family shrimp, are protandrous hermaphrodites, meaning they begin life as a male and change to female.
Generally, the pink shrimp’s transition from male to female takes place between their 1st and 2nd year, however there are a number of factors that can alter this cycle. For example, in a year that populations are dominated by age one shrimp, which are normally male, it is common to see the largest age one shrimp mature first as females and become viable for winter reproduction. These are known as primary females. |
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Three year classes of shrimp |
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The next year class
By their second year of life, pink shrimp are generally females of between 18 and 25 mm carapace length. In the fall, female shrimp produce roe that is stored in their heads (head roe), then transported (and fertilized) to their bellies as fertilized eggs, where they are carried over the winter. A female produces between 1,000 to 3,000 eggs, which hatch in early spring to begin the cycle again.
Three year olds, which are exclusively female, only comprise a small percentage of the pink shrimp population. Three year old pink shrimp are usually between 25 and 29 mm in carapace length. Four year olds are not normally found, given the toll of natural and fishery mortality.
Pink shrimp live short lives and population levels are widely variable. Due to predation by fish and humans, the life history of pink shrimp is a successful design for continued persistence of sustainable populations. |
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Two mature female shrimp; one with head roe and one carrying eggs |
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