Summary
Catch and release is a common practice among recreational anglers. In instances when fish are deeply hooked, the proper techniques for promoting survival are poorly understood, although evidence suggests that the fishing line should be cut rather than attempting to remove the hook. Bluegills Lepomis macrochirus were used as a model to identify the role of hook size (sizes 8 and 12), style (Aberdeen, baitholder, single egg), and the presence of barbs (only for baitholder hooks in size 10) on survival and hook retention for fish deeply hooked and the line cut. Eight hook style and size variants were manually embedded in the dorsal esophagus of fish, monitored over 10 d, and compared with unhooked controls. There was some evidence that Aberdeen style and larger hooks (size 8) incurred greater mortality over the 10‐d monitoring period, while barbless hooks did not improve survival. Hook retention was high (>90%) for all deeply hooked fish. “J” style hooks, such as Aberdeen, and larger hooks may not be warranted for bluegills; however, we suggest that anglers use an adaptive approach when they select for a gear type appropriate to their target catch and simply adjust for alternate gear and techniques if deep hooking persists.
Methodology
Study area and fish capture
Our study was conducted at the Queen's University Biological Station (44°34′N, 76°19′W), located on Lake Opinicon, a centrarchid‐dominated lake in southeastern Ontario. Additional details on Lake Opinicon and the bluegill fishery can be found in Cooke et al. (2003). Our experiment was conducted between August 21 and 30, 2010, in which all fish were collected and subjected to experimental treatment on the first day and posttreatment monitoring occurred over the following 10 d. Water temperature ranged between 23°C and 25°C during the capture and holding period.
Within a 6‐h period, we collected 179 bluegills (mean total length ± SD, 130 ± 25 mm) by rod and reel using a small piece of earthworm on barbless circle hooks (size 10). All fish were landed within 10 s of being hooked. We retained all fish that were shallowly hooked (i.e., hooked in the jaw) and appeared healthy (i.e., showed no sign of bleeding, parasites or fungus; had regular ventilation rate). We did not select for a specific size of fish; however, by using a size 10 hook we excluded many of the highly abundant subadult fish (Cooke et al. 2005). Hooks were removed underwater in a water‐filled trough and fish were temporarily (i.e., for no more than 10 min) transferred to a 50‐L cooler and supplied with frequently replenished fresh lake water before processing.
Experimental treatments
We had eight different deep hooking treatments and a control group in which fish were only subjected to the stressors of capture and captivity. The treatment hooks varied in the size, style, and presence of barbs. To evaluate survival and hook retention of fish deeply hooked with different hook styles and sizes we used three barbed hook types (Aberdeen, Mustad, model 3260b; baitholder, Mustad, model 92681; single egg, Gamakatsu, model GAM‐0052) in two sizes (large, size 8; small, size 12) that are commonly used by anglers when targeting bluegill and other panfish. The hook styles chosen each have distinct design elements (see Figure 1). Baitholder style hooks possess a set of small barbs along the shank, and a point aligned in the direction of the eye. Aberdeen style hooks resembled a typical “J” style design and have an extended shank and parallel point. Single egg hooks have a relatively round bend, and a short shank compared with the alternate styles. In addition, to evaluate the extent to which a barb influenced hook retention and survival, we used and compared the performance of barbed and barbless hooks using a single hook type and size (size 10 baitholder, Mustad, model 92681).
For all fish except the controls, treatments involved deep‐hooking a fish using hemostats (as per Pope et al. 2007). Unlike Fobert et al. (2009), attempts were made to reduce the variation associated with the degree of deep hooking and specific anatomical location by adopting a more experimental and controlled approach where fish were hooked manually in the esophagus to enable for a more direct assessment of hook size and style and their influence on survival and hook retention. The hook was passed into the esophagus of the bluegill until the hook point was no longer visible and gently pulled anteriorly with the hook oriented upwards to hook the tissue and emulate a moderate hook set. Hooks were therefore uniformly positioned in all fish. The esophagus appears to be the most sensitive location to be hooked and incurs the greatest mortality compared with other hooking locations (Pelzman 1978; Pope et al. 2007), which is why we selected that location. Each hook had 15 cm of 2.72‐kg (6 lb) test fishing line attached to determine hook retention based on line protrusion from the mouth or anus. All fish, including controls, were marked with individually numbered anchor tags (Floy Tag & Manufacturing, Seattle, Washington) posterior to the dorsal fin on the left side to distinguish fish among groups. After processing, fish were transferred to a round tank (1.4 m diameter, 1 m depth) containing a continuous flow of approximately 700 L/h of lake water and held for 10 d. Water temperatures were the same as lake temperatures (23–25°C) and dissolved oxygen was at ambient levels (80–100% saturation). The holding tank was outdoors with a mesh covering (to prevent predation), thus providing fish with natural light and weather conditions. During the holding period, fish were fed twice daily until satiation with frozen blood worms. The tank was siphoned and cleaned daily.