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

Authors: BORIN, JOSHUA - University Of Washington; MOSER, MARY - National Oceanic & Atmospheric Administration (NOAA); HANSEN, ADAM - Colorado Parks And Wildlife; BEAUCHAMP, DAVID - University Of Washington; CORBETT, STEPHEN - Ocean Associates, Inc; Dumbauld, Brett; PRUITT, CASEY - Washington State Department Of Natural Resources; RUESINK, JENNIFER - University Of Washington; DONOGHUE, CINDE - Washington State Department Of Natural Resources

Submitted to: Environmental Biology of Fishes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2017
Publication Date: 8/21/2017
Citation: Borin, J., Moser, M., Hansen, A., Beauchamp, D., Corbett, S., Dumbauld, B.R., Pruitt, C., Ruesink, J., Donoghue, C. 2017. Energetic requirements of green sturgeon (Acipenser medirostris) feeding on burrowing shrimp (Neotrypaea californiensis) in estuaries: importance of temperature, reproductive investment, and residence time. Environmental Biology of Fishes. 100:1561-1573. https://www.doi.org/10.1007/s10641-017-0665-3.
DOI: https://doi.org/10.1007/s10641-017-0665-3

Interpretive Summary: Green sturgeon (Acipenser medirostris), are a long lived species of fish whose populations along the west coast of North America have declined and one population segment is listed as threatened under the US Endangered Species Act. These fish are anadromous and undertake extensive migrations along this coast from California to British Columbia, Canada where they occupy estuaries during the summer and early fall. Warm water and abundant prey in these estuaries may provide a significant benefit for their growth. We applied a bioenergetics model to investigate how variation in estuarine temperature, spawning frequency (which only occurs in a few river systems), and duration of estuarine residence affect consumption and growth potential for individual green sturgeon. We made several conservative assumptions in this model including that green sturgeon achieve observed annual growth by feeding solely in conditions represented by Willapa Bay, Washington, an estuary with extensive tideflats where burrowing shrimp (Neotrypaea californiensis) are an important prey resource. Model results suggested that consumption rates increased little with reproductive investment (<0.4%), but responded strongly (10-50%) to water temperature and duration of estuarine residence, with higher temperatures and longer residence times requiring greater consumption to achieve equivalent growth. Although green sturgeon occupy Willapa Bay from May through September, acoustically-tagged individuals have only been tracked for much shorter periods (34 days on average). Using this 34 day estuarine residence period resulted in unrealistically high consumption rates to achieve observed growth, whereas longer durations required sustained feeding, and therefore higher total food intake, to compensate for metabolic costs at warm temperatures. These model results provided a range of per capita consumption rates for these fish feeding in estuaries, which could be used to inform management decisions regarding resource use (such as these burrowing shrimp) and habitat protection for these fish.

Technical Abstract: Habitat use can be complex, as tradeoffs among physiology, resource abundance, and predator avoidance affect the suitability of different environments for different species. Green sturgeon (Acipenser medirostris), an imperiled species along the west coast of North America, undertake extensive coastal migrations and occupy estuaries during the summer and early fall. Warm water and abundant prey in estuaries may afford a growth opportunity. We applied a bioenergetics model to investigate how variation in estuarine temperature, spawning frequency, and duration of estuarine residence affect consumption and growth potential for individual green sturgeon. We assumed that green sturgeon achieve observed annual growth by feeding solely in conditions represented by Willapa Bay, Washington, an estuary with extensive tideflats that harbor a major prey source (burrowing shrimp, Neotrypaea californiensis). Modeled consumption rates increased little with reproductive investment (<0.4%), but responded strongly (10-50%) to water temperature and duration of residence, as higher temperatures and longer residence required greater consumption to achieve equivalent growth. Accordingly, although green sturgeon occupy Willapa Bay from May through September, acoustically-tagged individuals are observed over much shorter durations (34 d + 41 d SD, N=89). Simulations of <34 d estuarine residence required unrealistically high consumption rates to achieve observed growth, whereas longer durations required sustained feeding, and therefore higher total intake, to compensate for prolonged exposure to warm temperatures. Model results provide a range of per capita consumption rates by green sturgeon feeding in estuaries to inform management decisions regarding resource and habitat protection for this imperiled species.