Life History 



Between the ages of 1 and 3 years, most individuals of this species are 

 sexually mature males. The transition to the female gender may begin as early 

 as 20 months, although it is more common at 32 months, and by 43 months almost 

 all individuals are functional females (Haynes and Wigley 1969). Some females 

 spawn twice, although most spawn only once in their lifetimes. Estimated 

 normal life span for individuals of this species in the Gulf of Maine is 4 to 

 5 years (Wigley 1972). 



In offshore waters of the Gulf of Maine copulation occurs after females molt 

 (Haynes and Wigley 1969). Eggs (330 to 500) are carried on the female's 

 pleopods (appendages on the underside) through the winter, during which time 

 females migrate inshore. Egg-bearing shrimp may prefer cold water and 

 therefore in the winter move gradually inshore, where the waters are cooling 

 (Stickney and Perkins 1977). The time of hatching depends on water 

 temperatures during the winter in which the eggs are being carried on the 

 female. In warm years hatching may take place as early as February and most 

 hatching is usually completed by April (personal communication from A. P. 

 Stickney, Maine Department of Marine Resources, Augusta, ME; November, 1977). 

 After hatching, larvae are planktonic (suspended in the water column) until 

 they lose their exopods (swimming appendages) after about three months 

 (Stickney and Perkins 1977). Male juveniles remain inshore until their second 

 winter (end of 2nd year) when they begin to migrate offshore. In the fall 

 egg-bearing females (end of 4th year) begin their migration inshore. 



The diet of the adult shrimp varies with the season, consisting of a larger 

 proportion of molluscs in the winter and crustaceans in the summer. The 

 shrimp may also eat polychaetes, protozoans, and echinoderms. 



Habitat Preferences 



The northern shrimp is considered a benthic species, although males and 

 females not carrying eggs may migrate vertically through the water column at 

 night to feed. Shrimp live in the subtidal zone of the marine system, usually 

 on unconsolidated bottoms composed of mud, silt, or sand that are high in 

 carbon and nitrogen content (Bigelow and Schroeder 1939). Larvae live in the 

 water column. 



Factors of Abundance 



The northern shrimp appears to have well-defined environmental requirements. 

 Salinity tolerance as high as 30 to 35 ppt is suggested by Wigley (1972) and 

 Haynes and Wigley (1969). The temperature tolerance of this species ranges 

 from 28 to 53°F (2 to 11. 5° C), although larvae can live in waters as warm as 

 57 F (14°C; TRIG0M 1974). 



There are 2 known parasites of the northern shrimp. One of these affects the 

 eggs of the shrimp and has been tentatively identified as a parasitic 

 dinof lagellate (Stickney 1978). The affected eggs are no longer viable and 

 fecundity is reduced. The other organism is a dinoflagellate of the genus 

 Gymnodinioides and infects the gills of adult shrimp (Apollonio and Dunton 

 1969). It is not known if mortalities from these parasites alter the shrimp 

 population. 



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