New recruits

In Oregon, pink shrimp larvae are released in early spring, and are planktonic for about 7-8 months before settling to the bottom in the fall. In the plankton, they pass through a series of zoeal growth stages or "instars" before they become recognizable as small shrimp. These young of the year or "zero age" shrimp are often found much higher in the water column than their adult counterparts.

Maturing shrimp

After one year pink shrimp between 13 and 17 mm in carapace length, and are reproductively mature. Oregon’s pink shrimp like many other shrimp are protandrous hermaphrodites, meaning they begin life as a male and over time will change to a female.

Generally, this transition takes place between its 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 a 1 year old shrimp, which are normally male, it is common to see the largest 1 year olds mature first as females and become viable for winter reproduction. These are known as “primary females”.

The next year class

By the second year of life, pink shrimp are generally all females, between 18 and 25 mm in carapace length. In the fall, female shrimp begin producing eggs, which are carried attached to their abdomen over the winter. A female prodces from 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 Oregon’s 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 in pink shrimp populations; nearly all three year old females will die following their third clutch of eggs hatching.

Due to predation on shrimp by fish and man alike shrimp’s life history is a successful design for continued persistence of sustainable populations.