The Science Of Circle Hooks
July 05, 2012
The concept of a circle hook is almost as old as fishing itself. Archeologists have found ancient circle-style hooks made of reindeer horn in Japan, and similar designs of shell from Polynesia. In North America, Native Americans from the West Coast carved bone hooks that resemble some of today's designs. Circle hooks are, however, one of the hot items in today's fishing industry.
Demand has steadily grown from a base in marine commercial fisheries, particularly longlining, where baited hooks are set to fish passively. In addition to setting without rod action, circle hooks are favored in commercial fisheries because they hook and retain fish, even on slack lines. They also tend to hook fish in the jaw, causing less mortality than standard J-hooks.
Inland, trotliners and limbliners first tried circle hooks. Today, more anglers are experimenting with circle hooks for various species, based on their perceived benefits: Jaw hooking, which should make removal easier; reduced gut-hooking, resulting in less mortality; and easy setting of the hook, which would be ideal for inexperienced anglers and in deep water situations. Other possible advantages include fewer lost fish, fewer snags, and safer handling. Recently, fishery management agencies have recommended circle hooks for their conservation benefits. In a few situations, regulations even require circle hooks.
But what is a circle hook? This term has been applied to a range of designs, from models with a point that mildly turns toward the shank, to a true circle that snags nothing at all if placed in your pocket. In-Fisherman editors have used certain designs extensively in a variety of situations. We'll continue to report our findings as we move forward. Overall, variation in design, along with lack of standardization of sizes among manufacturers, have led to conflicting results and confusion. We receive questions and reports about different designs and sizes for various species and sizes of fish, without resolution of any specific questions.
There's been a similar rise in scientific studies of these tools, particularly their anatomical hooking position, degree of wounding, hooking success rate, and mortality. Dr. Steve Cooke and Cory Suski of the University of British Columbia recently published a major review of scientific findings on this topic.* They charted the increase in studies from 1996, when there were none, to 2004 when 15 were completed or in progress. They then reviewed the results of 43 separate evaluations of circle hooks.
Most have addressed marine fisheries, with striped bass the most common subject. That's due to the huge striper fishery on the East Coast, where annual catch-and-release angling mortality has been estimated at 1.3 million fish, more than the number taken in the commercial fishery that year. Generally, the species most studied are those commonly captured on live or dead baits and those that have substantial hooking mortality with conventional hooks.
Cooke's and Suski's analysis resulted in some conclusions about circle hooks, along with many exceptions, further questions, and new areas for research.
Hooking Mortality: From a management standpoint, hooking mortality is critical when regulations require release of fish of a certain size range. And, of course, fish that are voluntarily released should be in viable condition. Delayed mortality can be important, but it's far more challenging to measure. When results of all studies were lumped, circle hooks resulted in lower mortality than other types, mostly J-hooks and octopus styles. Mortality estimates for circle hooks ranged from 0 to 34 percent, compared to 0 to 46 percent for J-hooks.
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.
Hook Size: Though there are general guidelines, it's often impractical to use hooks to match the expected size of fish. Large circle hooks don't hook small fish efficiently, and there's evidence that small circle hooks are more likely to hook larger fish in the gullet. This was evident in a study with sunfish. Larger circle hooks also may cause more eye-hooking of small fish, though they don't hook small fish efficiently. Obviously this is a vast topic, involving the nearly infinite range of fish sizes and the many hook styles and sizes.
Offset and Non-offset Designs: In describing hooks, "offset" refers to the amount of deviation in the plane of the hook point relative to that of the shank. In studies of sailfish and striped bass, offset circle hooks caused more damage than non-offset ones. But this result has not been consistent. It appears that the degree of offset (15 degrees is considered severe) affects rate of damage and mortality. A recent study on walleyes found no difference in deep-hooking between non-offset and 15 degrees offset circle hooks, however. Jigs were less likely to deep-hook walleyes than octopus or circle hooks (#4 Mustad Demon Circle Fine Wire) fished with leeches and crawlers.
Hot Topics: Cooke and Suski report that flies tied on circle hooks are a hot item, due perhaps to the conservation bent of many fly fishers. Preliminary results suggest, however, that circle hooks were not as effective at landing trout and bluegill as J-hooks, and removal time was greater. Bleeding and tissue damage were similar between hook types.
Sucker fishing for muskies in cold water continues to be popular in a few areas. This technique causes high mortality by stomach-hooking, when anglers allow muskies to swallow the hook. There's no data on use of circle hooks yet, but conservation benefits seem likely. Then again, perhaps single hooks of any design might compare unfavorably with the use of tandem treble hooks rigged in quick-strike fashion. One can only guess, based on personal observation.
Only one unfinished study has addressed circle hooks for ice fishing. As might be expected, trout were hooked deeper on J-hooks than on circle hooks, but mortality figures weren't available. Further benefits or drawbacks of circle hooks for ice fishing remain unproven. Gut-hooking of pike and walleye on tip-ups might be reduced with circle hooks, provided the hooks turn and set under firm hand-pressure on the line. Here again, quick-strike rigs have proven to reduce the incidence of gut-hooking while increasing hook-up percentage.
Trotlines and limblines fished for catfish are well suited to circle hooks. Opening the gap a bit on full circles has provided better hook-up ratios in some situations, though again, differences among hook types affect results. Open gaps also make it easier to bait hooks. Overall, circles hook and hold fish well and reduce mortality considerably, important as more length- and bag-limit regulations are enacted. But again, personal experiences also suggest that eye damage is common when circles are used on setlines.
Regulatory Issues: Cooke and Suski report that several jurisdictions require circle-hook use: Canadian white hake fisheries; some Maine groundfish (cod, haddock, etc.); some California coastal salmonid fisheries; and a section of the Delaware River striper fishery. But circle hooks aren't clearly defined, in many cases. There's a need for standardization of terminology and products in the tackle industry. A proposed requirement for circle hooks in all striped bass livebait fisheries was recently defeated due to lack of such standardization.
Cooke and Suski conclude, "Advances in hook design clearly have the potential to significantly reduce injury and mortality of fish that are to be released. Circle hooks represent the first major effort to alter hook design for conservation purposes. Of particular interest are studies that vary the degree to which the hook forms a circle, the gap between hook point and shank, and the size of hook relative to fish size." We couldn't agree more.
We also ask the fishing community not to look solely at any one technique or technology -- such as circle hooks -- for all the answers. In the "Inside Angles" column of this issue, Editor In Chief Doug Stange again describes a technique that can greatly reduce mortality of fish deeply hooked with conventional hooks.
We're in an age when selective harvest is a necessity. The objective is to ensure that we can continue to harvest and eat some fish, while releasing others to sustain good fishing into the future.