© 2018. Published by The Company of Biologists Ltd | Journal of Experimental Biology (2018) 221, jeb180935. doi:10.1242/jeb.180935 RESEARCH ARTICLE Angling-induced injuries have a negative impact on suction feeding performance and hydrodynamics in marine shiner perch, Cymatogaster aggregata Melissa Thompson1, Sam Van Wassenbergh2,3, Sean M. Rogers4, Scott G. Seamone4 and Timothy E. Higham5,* ABSTRACT and Cooke, 2008). Declining fish biodiversity and stocks highlight Fishing is a popular and lucrative sport around the world and, in the importance of fishing regulations and catch-and-release some cases, may contribute to declining fish stocks. To mediate this programmes (Lewin et al., 2006). Catch-and-release involves problem and maintain fish biomass in aquatic ecosystems, catch- recreational anglers catching and then quickly releasing a fish and-release fishing, whereby a fish is caught and immediately back into the water to help preserve the fish biomass, while still released, has been implemented in many countries. It is unclear enabling the continuation of fishing practices (Pollock and Pine, whether the injuries to the mouth that are caused by the hook have an 2007). Catch-and-release was initially thought to have a very impact on feeding performance of fishes. Using high-speed video and minimal impact on fish populations given that anglers were not computational fluid dynamics (CFD), we asked whether injuries removing fish from the habitat (Bugley and Shepherd, 1991). around the mouth caused by fishing hooks have a negative impact on However, average post-release mortality can be as high as 67% due suction feeding performance (measured as maximum prey velocity) to the stresses from catch-and-release, raising questions about the of the commonly angled marine shiner perch (Cymatogaster efficacy of this fishing method (Bettoli and Osborne, 1998). This aggregata). We hypothesized that fish with mouth injuries would mortality is due to many factors involved with fish capture and exhibit decreased feeding performance compared with controls. Ten handling, which includes, but is not limited to, time exposed to the shiner perch were caught using scientific angling and 10 were caught air, the roughness of being handled, time from being hooked to using a seine net. Feeding events were then recorded at 500 frames being brought up out of the water, where on the fish it was hooked, per second using a high-speed camera. Compared with the control the experience of the angler, the depth from which the fish was group, maximum prey velocity was significantly lower in the injured pulled, and fish size (Cooke et al., 2002; Bartholomew and group (P<0.01). Maximum gape, time to peak gape, maximum jaw Bohnsack, 2005). A study on the mortality of fishes after being protrusion and predator–prey distance were comparable between caught by recreational anglers indicates that fishes have species- the control and injured groups, leading us to conclude that the specific variability in their mortality, with most mortalities injury-induced hole in the buccal cavity wall reduced the pressure occurring between 4 h and 4 days after being caught (Broadhurst gradient during mouth expansion, thereby reducing the velocity of et al., 2005). Most studies generally do not consider the potential water entering the fish’s mouth. This was confirmed with our CFD impacts of hook injuries around the mouth as contributing to this modelling. Fishing injuries in nature are likely to depress feeding mortality, and it is generally viewed as the preferred way to catch a performance of fish after they have been released, although it is fish (Bartholomew and Bohnsack, 2005). Recent studies have currently unclear whether this has a significant impact on survival. examined the impact of hook removal (DeBoom et al., 2010) and the size and style of fish hooks (Robert et al., 2012) on the survival KEY WORDS: Fishing, Prey capture, Catch-and-release, Mortality, and feeding rate of freshwater fishes. Yet no study has addressed Conservation, CFD how such injuries may influence suction feeding performance of fishes immediately after they have been released, or the INTRODUCTION hydrodynamics of suction following an angling-induced injury. Recreational fishing is popular throughout the world and has Many species of fishes employ suction feeding, in which the significant socioeconomic impacts (Arlinghaus and Cooke, 2008). expansion of the buccal cavity creates an area of low pressure, Given the worldwide popularity of recreational angling, it is not drawing in a volume of water and the prey (Lauder, 1980; Muller, surprising that there are some ecological and conservation risks et al., 1985; Day et al., 2005, 2015; Higham et al., 2006a,b). It is associated with the large amounts of fish being caught (Arlinghaus likely that this feeding strategy would be most affected by angling- induced injuries, especially those that create a hole to the ambient water, given the importance of an intact buccal cavity for generating 1Department of Biology, University of Alberta, Edmonton, AB, Canada, T6G 2G7. suction forces. Indeed, fishing hooks and gear can cause tears and 2Département Adaptations du Vivant, UMR 7179 CNRS/MNHN, 57 rue Cuvier, Case Postale 55, 75231 Paris Cedex 05, France. 3Department of Biology, University injuries in the skin and membranes surrounding the mouth (Cooke of Antwerp, Universiteitsplein 1, 2610 Antwerpen, Belgium. 4Department of et al., 2003) and, therefore, could reduce the strength of suction. Biological Sciences, University of Calgary, Calgary, AB, Canada, T2N 1N4. If the injuries from fishing equipment are decreasing the fish’s 5Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA 92521, USA. chances of catching prey by decreasing feeding performance, then it might also affect the survivability of the fish until it is able to fully *Author for correspondence ([email protected]) heal. Incidence of complete and successful healing may partially T.E.H., 0000-0003-3538-6671 explain why short-term mortality of fishes is generally higher when compared with long-term mortality of released fishes (Pollock Received 15 March 2018; Accepted 6 August 2018 and Pine, 2007). Journal of Experimental Biology 1 RESEARCH ARTICLE Journal of Experimental Biology (2018) 221, jeb180935. doi:10.1242/jeb.180935 Experiments List of symbols and abbreviations Each of the experiments took place in the housing aquaria (76-liter), CFD computational fluid dynamics which were modified with a white background and a grid (with dots CSA cross-sectional area 1 cm apart) for scaling. Three to five individuals were placed into the Dexp total duration of head expansion aquarium and left to acclimate for a minimum of 1 h. If the fish did Mexp total magnitude of head expansion distance not appear motivated to eat, additional time was given until they were TTPG time to peak gape TTPJP time to peak jaw protrusion motivated. At that point, a 3 mm piece of tube worm was dropped into Vnode velocity of expansion of the nodes of the head surfaces in the middle of the tank and the feeding event was recorded in lateral the CFD model view at 500 frames per second using an Edgertronic high-speed camera (SC1, Sanstreak Corporation, San Jose, CA, USA) (Fig. 1). A minimum of three feeding events was recorded for each individual. In Using the marine shiner perch (Cymatogaster aggregata), we the case where a feeding event was not perpendicular to the camera, combined high-speed videography and computational fluid additional events were recorded and only the first three suitable strikes dynamics to determine the role of hook-induced injuries in the were used in analyses. The trial was still considered suitable if the fish performance and hydrodynamics of suction feeding. Shiner perch deviated only slightly from perpendicular. The results from these are ideal for this study as they are easily caught via recreational trials did not differ from the other trials. angling, exhibit specialized suction feeding behavior and Following the feeding events, the fish was placed into a 76-liter morphology (Chu, 1989), and are easily kept in laboratory. Our tank with enrichment. This process was completed until all fish were integrative approach enabled us to test the hypothesis that fishing- recorded and weighed. After the experiment was completed the fish induced injuries (holes through the membranes and skin) reduce were released at the point of capture or euthanized with Eugenol suction feeding performance (maximum prey velocity) by altering (>400 mg l−1) according to BMSC Animal Care standard operating the flow of water into the mouth during mouth expansion. procedures. MATERIALS AND METHODS Computational fluid dynamics Location and animals A computer-aided design model approximating the shape of the Ten shiner perch (Cymatogaster aggregata Gibbons 1854) were head and buccopharyngeal cavity of the shiner surfperch was caught from a boat via scientific angling in the Bamfield Inlet near designed based on MRI data from The Digital Fish Library project the Bamfield Marine Science Centre (BMSC) on Vancouver Island, (Fig. 2A,B). The ‘Blend’ functionality of ANSYS SpaceClaim BC, Canada (48°50′03.5″N, 125°08′12.7″W) in July 2017. An Direct Modeler 18.0 (ANSYS Inc., Canonsburg, PA, USA) was additional 10 individuals were caught via seine net on Wizard Islet used to fit volumes around three internal and three external in Trevor Channel (48°51′30.3″N, 125°09′32.7″W) in June 2017. ellipses. The axes of these ellipses correspond to the heights and The average standard lengths of fish in the control and injured widths of the head and buccopharyngeal cavity measured on the groups were 10.3 cm (range, 9.8–11.5 cm) and 9.1 cm (range, 6.0– MRI scan sections (see Fig. 2A). A subtraction operation of 11.5 cm), respectively. Body mass ranged from 12.3 to 41.1 g.