Evaluation of the interactive effects of air exposure duration and water temperature on the condition and survival of angled and released fish

Abstract

At present, there is a reasonable understanding of the independent effects of catch-and-release (C&R) angling stressors, such as air exposure and water temperature, on endpoints such as physiological disturbance, behavioural impairment and mortality. However, little is known about the multiplicative or interactive nature of these different C&R stressors. This study used bluegill (Lepomis macrochirus) as a model to evaluate the combined effects of water temperature and air exposure on fish behaviour, equilibrium status and short-term mortality following C&R. Experiments were replicated over 3 days with different ambient water temperatures (18.3, 22.8 and 27.4 • C). On each day, fish were captured by standard angling techniques, exposed to a range of air exposure durations (0, 30, 60, 120, 240, 480 and 960 s), and subsequently monitored for behavioural changes (within the first 300 s) and short-term (48 h) delayed mortality. Additional fish were captured by seine net for use as controls. There was an interactive effect of temperature and air exposure, whereby fish exposed to the highest temperature and longer air exposure durations lost equilibrium more often and had depressed ventilation rates relative to fish exposed to minimal air exposure and the lowest temperature. Immediate mortality at the lowest temperatures was negligible. However, significant delayed mortality (up to 80%) was noted at the highest water temperature (27.4 • C) in fish exposed to the three longest air exposure groups. In addition, at 27.4 • C, mortality among fish exposed to 480 and 960 s occurred at a faster rate than in any other treatment group. These results indicate that at low to moderate water temperatures, extended air exposure for bluegill may result in little mortality. However, at high water temperatures, short-term mortality (within 48 h) can be substantial, especially for fish that experience extended air exposure durations. Anglers and managers must recognize that C&R stressors can interact to have more dire consequences than when applied independently.

Quantifying Delayed Mortality from Barotrauma Impairment in Discarded Red Snapper Using Acoustic Telemetry

“…This large variability is influenced by multiple factors, including season, fishery sector, geographical region, and water depth, and is further convoluted by interactions among these factors (Gingerich et al 2007). Moreover, the majority of these studies have only assessed immediate discard mortality, or mortality that is observed from surface observations within several seconds postrelease, while delayed mortality is unknown.…”

Use of external Indicators to Evaluate Stress of Largemouth (Micropterus salmoides) and Smallmouth (M. dolomieu) Bass at Tournaments

“…Other studies report even low levels of stress resulting from increased water temperature can cause noticeable changes in behavior (e.g. loss of equilibrium, impaired swimming ability) [15,17].…”

“…angling induced injury, barotrauma, or exhaustion) and delayed (within five days of angling) mortality. In numerous studies, high levels of angling or hauling (transport in a livewell or other enclosure) induced stress was linked to an increased likelihood of delayed mortality [8,9,15]. Mortality due to air exposure did not correspond to changes in blood chemistry among commercially captured Pacific halibut (Hippoglossus stenolepis) [10].…”

“…Immediate mortality from angling stress (i.e. angling induced injury, barotrauma, or exhaustion) is usually negligible in centrarchids, except in cases of extreme temperatures [15,16]; however, delayed mortality can still present a problem for catchand-release anglers. Research into fish stress levels can help determine when and why fish experience the most stress, allowing catch-and-release anglers to take corrective actions and minimize sub-lethal impacts of angling on fish.…”

Short-term survival of discarded pearl perch (Glaucosoma scapulare Ramsay, 1881) caught by hook-and-line in Queensland, Australia

“…These factors have been the subject of numerous studies in recent years and include hook type or size (Aalbers et al, 2004;Butcher et al, 2008;Cooke et al, 2005;Graves and Horodysky, 2008;Grixti et al, 2007;Mapleston et al, 2008), hooking location (Alós et al, 2008;Butcher et al, 2007;McGrath et al, 2009;Pope and Wilde, 2004), landing apparatus (Barthel et al, 2003;Danylchuk et al, 2008;De Lestang et al, 2008) and duration of exposure to air (Gingerich et al, 2007;Reynolds et al, 2009).…”