Assessing the relationship between a Neotrypaea californiensis parasite and a potential host for natural biocontrol in shellfish aquaculture

The ghost shrimp Neotrypaea californiensis is a species of burrowing shrimp that negatively affects Pacific oysters Magallana gigas , by burying and suffocating these shellfish, and is considered a pest by shellfish aquaculture workers. The present study was undertaken to better understand the transmission and lifecycle of a larval spirurid nematode, Ascarophis sp., and determine whether this nematode could enhance biocontrol of ghost shrimp on shellfish aquaculture beds. We examined the relationship between mean larval Ascarophis sp. abundance in estuarine N. californiensis populations on the US West Coast and the feeding activity of migrating sturgeon Sinosturio spp., which feed on benthic organisms including N. californiensis and are potentially the definitive hosts of this nematode. Mean Ascarophis sp. abundance in N. californiensis populations was positively correlated with sturgeon feeding pit density, and parasite abundance was higher in larger N. californiensis (carapace length ≥12.5 mm). While nematode abundance in N. californiensis populations was positively related to sturgeon feeding activity, there was no evidence that nematode presence in the shrimp influenced this relationship. A laboratory experiment revealed that while N. californiensis size affected their burrowing speed, Ascarophis sp. infection did not. Our results do not support the idea that the presence of Ascarophis sp. enhances N. californiensis predation or would be useful for biocontrol. However, our findings improve understanding of the relationship between Ascarophis sp., their intermediate host, N. californiensis , and their potential final hosts, migrating sturgeon species.