The marine live bait trade as a pathway for the introduction of non-indigenous species into California: patterns of importation and thermal tolerances of imported specimens

Importation of marine live bait may be an important pathway for the introduction of non-indigenous species (NIS), but little is known about the diversity of species or the numbers of individuals imported via this pathway. In 2009, we investigated the marine live bait trade in California as a potential introduction pathway for NIS. We estimated that in that year, similar to 1,900,000 ghost shrimp (Neotrypaea californiensis), similar to 575,000 bloodworms (Glycera dibranchiata), similar to 600,000 pileworms (Alitta virens), and similar to 1,100,000 lugworms (Perinereis sp.) were imported into California from different parts of the world. Along with the target imported species, hitchhiker species were commonly observed in live bait shipments. We exposed two of the live bait species (G. dibranchiata and Perinereis sp.) to a range of temperature conditions (12, 16, and 24 degrees C) found in nearshore marine habitats of southern California, and found that their short-term survival was not restricted at the two cooler temperature conditions, but that survival of Perinereis sp. was significantly reduced at the highest temperature, 24 degrees C. Though relatively few bait species were imported into the state in 2009, the large number of individuals imported and their high survival in thermal conditions typical of southern California habitats suggests that the live bait trade may be an important potential pathway for the introduction of NIS to this region.