Although many fish are captured and released following hook removal by recreational anglers, some fish break the line and are confronted by the potential impediment of a lure lodged in the jaw, buccal cavity, or throat. We simulated break-off events by releasing northern pike (Esox lucius) into Lake Opinicon, Canada with custom-built lures that were manufactured to contain radio transmitters. Treatment groups combined hook placements (lower jaw, upper and lower jaw, throat) and hook types (barbed and barbless) to investigate the effects on pike survival, movement, and lure shedding. Fifty-one pike were released (522 ± 64 mm), three of which died (6%; 95% CI = 2–16%). Data were analysed by dummy variable regression to investigate the main effects of hook placements and hook type in pike. Cumulative distance swam after release was significantly reduced by deep hooking and lower jaw hooking. All fish except for one shed the lures within 14 d of release, and barbed hooks and lures lodged in the lower jaw significantly increased the time required for pike to shed lures. In light with previous work, we documented significant short-term behavioural consequences of lure break-off for pike (i.e. hyperactivity) but the experimental fish rapidly and naturally shed the hooks within days in nearly every instance. Given our findings, for pike (and likely related species such as muskellunge), anglers can be reasonably confident that long-term damage to individuals is limited even when a lure is retained by an animal following a break off event. Nonetheless, use of barbless hooks facilitates lure shedding, and all efforts should be taken to avoid break off events in the first instance using appropriate gear (e.g., wire leader, heavy line) especially when angling for fish with sharp dentition.
Study site and animals
The study was conducted at the Queens University Biological Station (QUBS) in eastern Ontario, Canada, (44°31′N, 76°22′ W) between June 16th and July 11th, 2009. Water temperature ranged from 20 to 24 °C over the course of the field program and the predominant wind direction was out of the north east. Fish capture and tagging complied with guidelines set by the Canadian Council on Animal Care (protocol #1508) with scientific collection permits approved by the Ontario Ministry of Natural Resources.
Northern pike were collected from Lake Opinicon by conventional hook-and-line angling at a variety of locations throughout the lake. Angling gear consisted of medium action spinning rods and reels spooled with 15–20 lb test line. Lures, consisting of spoons and artificial fish imitations (crank baits), were attached to the line with wire leaders and swivels. Treble hooks did not have barbs to minimize injury and to increase ease of hook removal (Alós et al., 2008). On a given day, fish were collected from a location until enough fish were captured to complete a round of releases, no more than five fish at a time. Upon capture, fish were immediately brought to the boat, netted with a rubberized fish net keeping fighting time shorter than 60 s. Following hook removal, fish were assessed and those in good condition (i.e. no visible signs of excessive injury or bleeding) transferred to an onboard live well. The live well was covered and regularly flushed with fresh lake water to enhance stable conditions with holding periods less than 2 h (Arlinghaus et al., 2008a, 2009; Klefoth et al., 2008). Fish were then transported to the QUBS wet lab facility and transferred from the live well to insulated containers with fresh lake water. Water was circulated regularly through the containers to ensure water quality and every effort was made to reduce air exposure and maintain an optimal environment for the fish in the water. After a 1 h holding period, the fish were carefully netted and randomly allocated to control or treatment groups.