From the Field--Idaho fishery biologists tested the effects of three hook types fished with two angling methods on deep hooking and angling success of wild stream trout.* Anglers fished from shore or waded, and presented nightcrawlers to trout in pool and run areas using three hook styles: an inline circle hook (Eagle Claw Lazer Sharp L702G), in-line J-hook (Lazer Sharp L214), and offset J-hook (Eagle Claw 84). All hooks were #8, barbed, and fished on 6-pound Trilene XL monofilament.
Anglers fished each hook type using two methods that the researchers called active and passive. Active fishing used a quick hook-set with a sharp lift of the rod once a bite was detected. In passive fishing, the rod was gently lifted while slowly reeling up slack and applying constant pressure when fish bit.
Overall, 20 percent of rainbow trout and cutthroat trout were deep-hooked--the hook embedded in the esophagus or deeper, or in the gill arches. Deep-hooking was the result of a combination of hook type and fishing method. It was greater for offset J-hooks fished passively and in-line J-hooks fish actively than for offset J-hooks fished actively and in-line circle hooks fished actively. Hooking success (the ratio of hook-ups to strikes) was greatest for in-line J-hooks fished actively, and lowest for passively fished offset J-hooks and circle hooks.
The researchers offer that the higher deep-hooking rate of J-hooks in this study could be due to the narrower profile compared to the circle hook, making it easier for trout to swallow J-hooks. They conclude that while the capture efficiency for circle hooks was lower than for J-hooks, circle hooks appear to have potential to reduce deep hooking in stream trout. However, less deep-hooking on baited circle hooks occurs when hooks are fished actively, rather than by passive methods that are often recommended. Setting the hook in traditional manner when a trout bites seems to limit the time a fish has to swallow a baited hook.
* Sullivan, C. S., K. A. Meyer, and D. J. Schill. 2013. Deep hooking and angling success when passively and actively fishing for stream-dwelling trout with baited J and circle hooks. N. Am. J. Fish. Mgmt. 33: 1-6.