Do sturgeon limit burrowing shrimp populations in Pacific Northwest Estuaries?

Abstract

Green sturgeon, Acipenser medirostris, and white sturgeon, Acipenser transmontanus, are frequent inhabitants of coastal estuaries from northern California, USA to British Columbia, Canada. An analysis of stomach contents from 95 green sturgeon and six white sturgeon commercially landed in Willapa Bay, Grays Harbor, and the Columbia River estuary during 2000-2005 revealed that 17-97% had empty stomachs, but those fish with items in their guts fed predominantly on benthic prey items and fish. Burrowing thalassinid shrimp (mostly Neotrypaea californiensis) were important food items for both white and especially for green sturgeon taken in Willapa Bay, Washington during summer 2003, where they represented 51% of the biomass ingested (84.9% IRI). Small pits observed in intertidal areas dominated by these shrimp, are likely made by these sturgeon and we present evidence from exclusion studies and field observation that the predator making the pits can have a significant cumulative negative effect on burrowing shrimp density. These burrowing shrimp present a threat to the aquaculture industry in Washington State due to their ability to de-stabilize the substrate on which shellfish are grown. Despite an active burrowing shrimp control program in these estuaries, it seems unlikely that current burrowing shrimp abundance and availability as food is a limiting factor for threatened green sturgeon stocks. However, these large predators may have performed an important top down control function on shrimp populations in the past when they were more abundant.

Occurrence and biological characteristics of broadnose sevengill sharks (Notorynchus cepedianus) in Pacific Northwest coastal estuaries

“…As such, sevengill sharks represent one neglected aspect of an otherwise relatively well-studied system, where a great deal of research has focused on bottom-up production (Roegner et al 2002;Hickey and Banas 2003;Parrish et al 2003;Reusink et al 2003), especially when compared to research on upper levelpredators (but see Dumbauld et al 2008).…”

Energetic requirements of green sturgeon (Acipenser medirostris) feeding on burrowing shrimp (Neotrypaea californiensis) in estuaries: importance of temperature, reproductive investment, and residence time

“…Green sturgeon are benthic feeders (Moyle 2002;Dumbauld et al 2008), but their diets are not well documented. Based on gut contents of sturgeon caught as bycatch in the summer 2003 Willapa Bay salmon fishery (N = 9), burrowing shrimp Neotrypaea californiensis were present in more than half of the fish and represented 89% of identifiable gut contents by mass (Dumbauld et al 2008).…”

“…Based on gut contents of sturgeon caught as bycatch in the summer 2003 Willapa Bay salmon fishery (N = 9), burrowing shrimp Neotrypaea californiensis were present in more than half of the fish and represented 89% of identifiable gut contents by mass (Dumbauld et al 2008). To estimate the maximum likely consumption rate of burrowing shrimp for individual green sturgeon, all model simulations assumed a diet composition of 100% burrowing shrimp.…”

“…While in the estuary, green sturgeon consume burrowing shrimp (Neotrypaea californiensis), which dominate stomach contents (Dumbauld et al 2008). N. californiensis is a habitat engineer whose presence at high densities defines an estuarine habitat type (Bshrimp beds^, Ferraro and Cole 2011).…”

A feeding experiment using captive green sturgeon (Acipenser medirostris Ayres, 1854): Testing non-invasive methods to assess condition and growth

“…Recent efforts to designate and protect critical green sturgeon habitat have highlighted the lack of information regarding where and when these fish feed. They are known to aggregate in the Washington estuaries in summer and are thought to feed there (Dumbauld, Holden, & Langness, ; Moser & Lindley, ). It may be that green sturgeon use estuaries to “recharge” after coastal migrations (Borin et al., ).…”