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

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 annually frequented by green sturgeon and containing extensive tidal flats 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 Environ Biol Fish (2017) 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 protected species.

Applying a simplified energy-budget model to explore the effects of temperature and food availability on the life history of green sturgeon (Acipenser medirostris)

“…S2 of the Supplementary material). While physiological rates of ectotherms are often well described by an exponential relationship at low to intermediate temperatures, the relationship can break down towards the higher end of the temperature range, where feeding rate plateaus or even declines (Borin et al, 2017;Hung et al, 1993;Mizanur et al, 2014;Handeland et al, 2008;Lee et al, 2016). We hypothesized this mismatch in observed and predicted growth rates was due to leveling off of feeding rates at high temperatures.…”

“…who suggested that the optimum was between 15°C to 19°C. Mayfield and Chech (2004) reported that food consumption, growth, and food conversion efficiency generally increased with temperature between 11 O C and 15 O C but stayed constant between 15 O C and 19 O C. However, a recent laboratory experiment (Poletto et al, 2018) found that green sturgeon reared at 19 O C grew at faster rates than those reared at 16 O C. In a recent simulation study, Borin et al (2017) reported that the mass-specific growth rate of a 20year old adult green sturgeon increased with temperature until 19 O C and declined above this temperature. In this study, the authors applied the Wisconson bioenergetics model (Hanson et al, 1997) to investigate the effects of different environmental factors, including temperature, on the consumption and growth potential of green sturgeon inhabiting Willapa Bay, Washington.…”

“…Where y BA is conversion efficiency of converting assimilated energy into eggs, and W B0 is the mass of a single freshly laid sturgeon egg. We assumed an average spawning interval of three years, which falls within the estimated range (2-5 years) for green sturgeon (Borin et al, 2017). We estimated W B0 from estimates of green sturgeon egg size.…”

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

“…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., ). Conversely, they may simply hold in these relatively predator‐free and physiologically‐benign zones to save energy or reduce predation risk (Moser & Lindley, ).…”

“…It may be that green sturgeon This article has been contributed to by US Government employees and their work is in the public domain in the USA. use estuaries to "recharge" after coastal migrations (Borin et al, 2017).…”