Close Encounters with a Fish Screen: Integrating Physiological and Behavioral Results to Protect Endangered Species in Exploited Ecosystems

Abstract

Protection of endangered species that are restricted to highly modified ecosystems and threatened by anthropogenic activities often includes regulatory design and operational criteria for structures and facilities located within the species' critical habitat. In many freshwater systems, loss of fishes at water diversions has contributed to population declines of multiple species. Fish screens prevent removal of fish from the habitat; however, under current design criteria, the degree of protection provided by screens is unknown for most affected species. We used a large laboratorybased flume to observe and quantify the responses of delta smelt Hypomesus transpacificus, an endangered osmerid threatened by water diversions in California's Sacramento-San Joaquin Estuary, to a simulated fish screen. For a range of flow and environmental conditions, we measured screen contact frequency, swimming behavior, injuries, and survival. Delta smelt experienced frequent temporary contact with the screen, and contact rates were influenced by flow and time of day-light level. Contact was injurious, and postexperiment mortality rates were directly related to both contact frequency and severity as well as temperature. Quantitative models showed that, for this species, both behavioral responses such as swimming velocity and physiological responses to fish screen contact, as modified by environmental conditions, controlled the species' performance and its risk from the diversion and the screen. The results illustrate that ecologically effective protection strategies and regulatory criteria developed on the basis of multiple integrated responses of the organism to the stressor offer greater benefits and certainty to both the organism and the regulated activities.

Approach velocity and impingement duration influences the mortality of juvenile Golden Perch (Macquaria ambigua) at a fish exclusion screen

“…Whilst screens can reduce fish entrainment, they are of limited utility if they induce injury and mortality due to screen impingement. This is consistent with existing literature where screen contact and impingement have been shown to be positively correlated with approach velocities (Danley et al 2002;Swanson et al 2005;White et al 2007;Young et al 2010). In the current study, impingement of Golden Perch was observed at approach velocities of 0.05 m/s and increased significantly with increased Figure 3.…”

“…Although this work has been limited to a small number of species, life stages and screen types, it has been preliminarily recommended, based upon field and laboratory experiments, that approach velocities should not exceed 0.1 m/s to protect native Australian juvenile fish ). Furthermore, criteria for exclusion screens have focused primarily on approach velocity (Peake 2004;Boys et al 2013b) or its interaction with sweeping velocity (Danley et al 2002;Swanson et al 2004Swanson et al , 2005White et al 2007;Young et al 2010); however, the role of pumping at different velocities and durations may play in influencing fish impingement and subsequent survival has not been investigated. Since there are a wide variety of species and life stages vulnerable to extraction at pump offtakes in the MDB (King & O'Connor 2007;Jones & Stuart 2008;Baumgartner et al 2009;Baumgartner & Boys 2012), guidelines will need to protect a diverse fish community.…”

Effect of water temperature on laboratory swimming performance and natural activity levels of adult largemouth bass

“…Critical swimming speed (or U crit ), measured using a swim tunnel, has long been regarded as the best metric of swimming performance because it indicates maximal aerobic swimming capacity (Beamish 1978). More recently, researchers have argued that U crit tests have been used arbitrarily (Plaut 2001;Nelson et al 2002) and methods such as laser gaits and swimming flumes that result in the fish moving more freely or voluntarily are a more representative metric (Nelson et al 2002;Peake and Farrell 2004;Swanson et al 2004Swanson et al , 2005McDonald et al 2007). One method that measures voluntary activity is field-based telemetry.…”

Influence of Approach Velocity and Mesh Size on the Entrainment and Contact of a Lowland River Fish Assemblage at a Screened Irrigation Pump

“…Most fish screen guidelines in these countries (except New Zealand) were developed to protect migratory salmonids during seaward migration phases [11], [18]. It is increasingly accepted that other species impacted by diversions have been poorly considered in screen guidelines [19] and it is important to consider larger components of the migratory fish assemblage when developing guidelines [12].…”