Effects of hook type on injury and capture efficiency of rock bass, Ambloplites rupestris , angled in south‐eastern Ontario

The injury rates, hooking efficiency, and mortality in rock bass, Ambloplites rupestris Rafinesque, angled using circle hooks and three conventional hook types were compared. Circle hooks have only recently been introduced to recreational fisheries and differ substantially from other hook designs. Unlike conventional hooks, the point of a circle hook bends back towards the shank of the hook such that the point is perpendicular to the shank. Circle hooks have been touted by angling media, conservation organizations and tackle manufacturers as effective tools for minimizing injury and mortality of fish while maintaining capture efficiency (Montrey 1999; Stange 1999). The basic premise behind circle hook use is that the orientation of the hook point will prevent deep hooking, yielding high jaw hooking rates consistent with minimal injury and mortality. Empirical assessments of this premise are lacking, especially in freshwater systems (Cooke, Suski, Barthel, Ostrand, Tufts & Philipp, in press). Because of the interspecific variation in feeding mode, mouth morphology, gape size and angling techniques, it is necessary to examine the performance of circle hooks relative to other hook types to determine if the use of circle hooks should be advocated as a conservation measure. In this study, rock bass were used because of their frequency of capture in recreational fisheries, coupled with their high rates of release as a result of low food value (Cooke, Philipp, Dunmall & Schreer 2001). All fish were angled from Lake Opinicon, Ontario, between 18 May and 15 June 2001. During that time, water temperatures ranged from 18 to 26 C, but previous studies examining the effects of hook type on injury and mortality in some confamilial species (bluegill Lepomis macrochirus Rafinesque and pumpkin seed L. gibbosus L.) revealed that water temperature did not significantly influence injury or mortality rates across the range of water temperatures examined (Cooke et al. in press). For this reason, the influence of temperature on injury rates was not examined. Four commercially available hook types that are frequently used by anglers to target rock bass were used: baitholder hook (size 6, bronze, offset, down eye, model 3181UK, Eagle Claw Inc.), Aberdeen hook (size 6, gold, light wire, ringed eye, model 3202UK, Eagle Claw Inc.), circle hook (size 6, black/chrome, curved in point, mutu light, model 5114–051, Owner Inc.), wide bend (size 6, bronze, plain shank, offset, ringed eye, model L042, Eagle Claw Inc.). All anglers used the same organic bait (Crappie Nibbles, silver glitter, Berkley Inc.), and all anglers fished for equal lengths of time using all different hook types. The duration of time the fish was angled was standardized to 15–30 s. Upon capture, several different response variables were recorded. The location of hook penetration was measured from the anterior aspect of the (lower) lip to the deepest (i.e. most posterior) point of hook penet-