Population biology of the freshwater shrimp Paratya curvirostris (Heller, 1862) (Decapoda: Atyidae)

The life history of the endemic New Zealand freshwater shrimp Paratya curvirostris (Heller, 1862) (Decapoda: Atyidae) in 3 streams in North Canterbury is described. Each female carried on average 2000(±634) eggs and incubation took about 28 days at 14–18°C. Mixohaline planktonic larvae were found in the Ashley Estuary and in small numbers in fresh water. Post‐larvae had a carapace length of 0.5–1.5 mm, and most developed into males which occurred in freshwater streams. At a carapace length of 5.0–6.0 mm males developed into females which could be ovigerous at any time of year and could bear several successive broods. Estimated growth rate was greatest from late winter to early summer with a maximum weekly rate of 1.5 mm carapace length calculated in spring. The behaviour of a female during egg hatching is described in detail.