Determination of Population Discreteness in Two Species of Shrimp, Pandalus jordani and Pandalopsis dispar, from Coastal British Columbia Using Parasite Tags and Other Population Characteristics

Abstract

Two digenean metacercariae, Neolebouria tinkerbellae and an unidentified species (Metacercaria A), parasitizing Pandalus jordani, and Metacercaria A parasitizing Pandalopsis dispar, were used as naturally occurring biological markers to determine intraspecific population discreteness. Shrimp were sampled from Imperial Eagle Channel and Trevor Channel, Barkley Sound (west coast of Vancouver Island, British Columbia), and from an adjacent offshore area. The mean size at age and the age composition of P. jordani and P. dispar were also estimated. Many differences occurred among samples in the abundances of the metacercariae, in the mean size at age, and in the age composition for each shrimp species, demonstrating that separate shrimp populations existed. In some cases, natural boundaries separated populations of shrimp, for example, the island chain and shallow waters which lie between Imperial Eagle Channel and Trevor Channel. In other cases, such as occurred for the separate populations identified within Imperial Eagle Channel, there were no apparent topographic barriers. No evidence for the occurrence of offshore or onshore migrations of P. jordani or P. dispar was obtained.