There was substantial variation among species, however. For striped bass, mortality with circle hooks ranged from under 1 percent to 6 percent while J-hooks accounted for 9 to 18 percent mortality, a sizeable difference. Red drum, salmon, and tuna also showed major differences.

But in studies with bluegill and pumpkinseed, rock bass, largemouth bass, and summer flounder, mortality rates were similar between circle hooks and conventional designs (including octopus, sproat, and widegap). Bass mortality was low with circle (5.1 percent) and octopus (6.6 percent) hooks with fathead minnows as bait. Sunfish mortality was extremely low for all hook types (1 percent) and no rock bass were killed by hooking. For flounder, mortality for all hook types was between 12 and 16 percent.

Injuries and Mortality: Physiological damage from hook setting and removal can be minor or severe, including brain damage, blinding, and gill tearing. Cooke and Suski report that post-mortem exams of stripers killed with conventional hooks found damage to the heart, liver, gill arch, kidneys, and intestines. As circle hooks are not often swallowed, such damage is reduced. The summary of studies found that jaw hooking was far more frequent with circle hooks than other types. The incidence of gut hooking with circle hooks is low (generally less than 5 percent). Bleeding also was lower with circle hooks, a factor often related to hooking location.

Circle hooks did tend to cause more eye damage than other types, however. The point of some hooks tends to penetrate the eye orbit as it sets, and further damage may result from removal. Blinded fish are obviously far less likely to thrive, and the wound is a dangerous entry point for bacteria.

Time required to remove hooks can affect mortality, since fish are typically held out of water during the process. Cooke and Suski note that this factor hasn't been examined widely, but that circle hooks generally were more difficult to remove. But again, this factor varies among fish species and likely also varies based on specific design and hook size in relation to fish size.

Hooking efficiency is important to anglers and managers, as regulations requiring circle hooks won't be well received if anglers seem to miss or lose more fish than with traditional designs. The overall conclusion from the compilation of the studies was that J-hooks hooked fish more readily than circle hooks, but when hooked, circle hooks were responsible for higher landing rates.

Hooking efficiency is related to equipment and experience. As experienced users have learned, circle hooks don't work with stiff rods and standard hooksets. Slower action rods allow fish to pull against the rod without ejecting the bait, while the hook slides to the jaw and often into the corner of the mouth. Hooksets snatch the hook out, without giving the hook point a chance to catch and eventually set. This behavior must be learned, however, and habits die hard. Moreover, circle hooks don't work well for fish that nibble at baits without engulfing them, since hook-ups require that the hook be fully within the fish's mouth.

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