Abstract
Studying the sublethal effects of catch-and-release (C&R) is challenging, as there are several potential sources of bias. For example, if behavioural alterations immediately after the release event are to be studied, separation of tagging effects from actual C&R effects is required, which is a challenge in the wild, particularly in marine environments. To investigate the effects of C&R on Atlantic cod (Gadus morhua) in their natural environment, 80 cod were caught in fyke nets, fitted with acoustic transmitters, and released. After recovery from tagging and handling for at least 14 days, nine individuals were recaptured and released at least once during experimental angling, following best release practice. All cod survived the C&R event and did not show any large-scale behavioural changes (i.e., changes in diel vertical migrations). However, analysis of small-scale vertical movements showed that three individuals underwent short-term alterations (e.g., reduced or increased swimming activity). This study showed that pretagging fish with acoustic transmitters before experimental angling is an option when investigating fish behaviour immediately after the release event in marine environments. Moreover, release guidelines for cod should be developed, as cod can recover quickly if caught in shallow waters (<20 m) and properly handled and released.
Highlights
During the last two decades, recreational fisheries have been increasingly recognized both as an important contributor to fishing mortalities of marine fish stocks (Coleman et al 2004; Cooke and Cowx 2004; Lewin et al 2006; McPhee et al 2002) and as a socioeconomically important activity (e.g., Arlinghaus and Cooke 2009)
Based on the before data, there was no statistical support for our experimental angling being selective on fish length, Diel vertical migration (DVM), or mean depth occupied by the fish (p > 0.3; Fig. 3; Table 2)
Since the cod were fitted with acoustic tags several weeks prior to the C&R experiment, it was possible to study even small behavioural alterations immediately after the C&R event without bias caused by additional handling (Bridger and Booth 2003; Donaldson et al 2008)
Summary
During the last two decades, recreational fisheries have been increasingly recognized both as an important contributor to fishing mortalities of marine fish stocks (Coleman et al 2004; Cooke and Cowx 2004; Lewin et al 2006; McPhee et al 2002) and as a socioeconomically important activity (e.g., Arlinghaus and Cooke 2009). Apart from ethical challenges connected to C&R (Arlinghaus 2008), the hooking, fighting, and handling of fish can lead to unintended post-release mortalities (for reviews see Bartholomew and Bohnsack 2005; Hühn and Arlinghaus 2011; Muoneke and Childress 1994) or sublethal effects like behavioural alterations or physiological stress responses (Cooke et al 2013; Cooke and Sneddon 2007). As post-release mortalities and sublethal impacts can vary substantially between species, it is important to conduct species-specific C&R studies that can aid in the development of best practice guidelines to minimize negative impacts (Cooke and Suski 2005)
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