Offset Circle Hooks Research Articles

The physiological effects of capture stress, recovery, and post-release survivorship of juvenile sand tigers (Carcharias taurus) caught on rod and reel

Current shark fishery management regulations in the US Atlantic, as well as other regions worldwide, mandate the release of sand tigers (Carcharias taurus) captured in recreational fisheries. To examine the efficacy of this strategy as a conservation tool, the physical and physiological effects of capture stress and post-release survivorship were examined in juvenile sand tigers angled on conventional rod and reel tackle with offset circle hooks. Analysis of blood samples obtained immediately after capture (n=84) indicated that, relative to minimally stressed captive individuals, juvenile sand tiger blood biochemistry is disturbed after brief (<7min) angling events. Serial blood sampling of five captive sharks subjected to a 3min simulated rod and reel angling event revealed rapid and significant disruptions in blood biochemistry with physiological recovery within 12–24h. Post-release monitoring of 65 sharks surgically implanted with acoustic tags demonstrated high degrees of immediate (99%), short- (82%), and long-term post-release survivorship (75%). Physiological disruptions did not appear to reduce immediate survivorship (5 days post capture), however, sharks hooked internally had lower rates of survival 50–100 days following release. Overall, these results suggest that juvenile sand tigers are able to cope with and survive the physiological stress associated with brief rod and reel capture, but physical trauma associated with hook location can impair post-release survival. Regardless, mandatory release appears to be a viable management strategy for juvenile sand tigers captured in rod and reel fisheries.

Performance of Non-Offset and 10° Offset 18/0 Circle Hooks in the United States Pelagic Longline Fishery

Industry standard fishing hooks used prior to 2004 during Us commercial pelagic longline (Pll) fishing were the 8/0-10/0 J-hooks with a 20°-25° offset�a lateral deviation of the hook point relative to the hook shaft. However, federal regulations enacted in 2004 require the Us Pll industry to employ circle hooks allowing up to 10° offset during fishing operations. Until recently, there have been no studies directly comparing the performance of non-offset and 10° offset circle hooks in commercial Pll applications. Our study alternated non-offset and 10° offset circle hooks along the gear length on individual Pll deployments in the western north atlantic, gulf of mexico, and Windward Passage in the caribbean sea. The study compared the relative performance of both hook types in terms of: (1) catch rates, (2) percent mortality, and (3) the percentage of deep-hooked target and bycatch species. For swordfish, Xiphias gladius (linnaeus, 1758), several experiments indicate: (1) marginally higher catch rates, (2) significantly lower mortality, and (3) significantly less deep hooking on non-offset than 10° offset circle hooks. Most of the performance differences for blue marlin, Makaira nigricans lacepede, 1802, were insignificant; however, one study produced significantly higher mortality on 10° offset than non-offset circle hooks. The present study suggests that, relative to non-offset circle hooks, 10° offset circle hooks may reduce fishing efficiency and can counteract the conservation benefits commonly associated with circle hooks (e.g., lower mortality). However, additional research is required to assess the effects of offset hooks on tunas, billfishes, and elasmobranchs.

Relationship Between Hook Type and Hooking Location in Sea Turtles Incidentally Captured in the United States Atlantic Pelagic Longline Fishery

Because incidental capture in pelagic longline fishing gear potentially kills or injures thousands of sea turtles annually, solutions to reduce the frequency and mortality rate of these interactions are critical conservation priorities. Understanding factors that affect post-hooking mortality rates remains an important component to evaluating the population-level impact of these interactions. Post-release mortality may be dependent upon the nature of the interaction (hooking location and/or entanglement) and amount of gear remaining at release. Hooking location can impact the ability of the crew to remove gear, as deeply ingested hooks cannot be removed safely. We examined the effects of hook type (circle vs J-hooks), offset (degrees), and other factors on hooking location in leatherback, Dermochelys coriacea (Vandelli, 1761), and loggerhead, Caretta caretta (linnaeus, 1758), sea turtles incidentally captured from 2000 to 2010 using fishery observer data. Significant differences in hooking location in loggerheads were observed between offset J-hooks and non-offset and 10° offset circle hooks; loggerheads were most often mouth/beak hooked with circle hooks, whereas most had swallowed offset J-hooks. Greater offsets appear to increase the frequency of deeply ingested hooks. Leatherback sea turtles were predominately externally hooked regardless of hook type, but mouth hookings occurred significantly more often on non-offset (0°) circle and J-hooks than on 10° offset circle hooks. When combined with outreach and education on careful release protocols, the use of circle hooks may increase post-interaction survival by modifying hooking location and facilitating maximum gear removal.

Can Circle Hook Offset Combined with Baiting Technique Affect Catch and Bycatch in Pelagic Longline Fisheries?

Circle hooks have become a standard requirement in many commercial longline fisheries in the united states, and are used increasingly worldwide. Circle hooks, when compared to J-hooks, are thought to reduce bycatch without significantly decreasing (and possibly increasing) catch of most target species. Circle hook offset and baiting technique are also thought to influence bycatch and mortality of species of concern, such as sea turtles and billfishes. We compared non-offset circle hooks to those with a 10° offset and single or threaded baiting techniques in the united states atlantic and gulf of mexico pelagic longline fishery. Offset and/or baiting techniques were compared within sets targeting one of three species independently: swordfish, Xiphias gladius linnaeus, 1758, yellowfin tuna, Thunnus albacares (bonnaterre, 1788), and bigeye tuna, Thunnus obesus (lowe, 1839). Most comparisons of catch and bycatch did not differ between gears or techniques. In swordfish-directed sets, we found a 46% decline in catch of atlantic sailfish when using 18/0 non-offset circle hooks single baited with mackerel compared to 18/0 10° offset circle hooks with threaded mackerel. In yellowfin tuna sets, single baiting significantly decreased target catch by 22% and escolar catch by 28%, compared to threaded baiting. We detected no significant effect of any of the offset or baiting treatments on the bycatch of sea turtles and most other species of concern due to the rarity of capture events. We conclude, in part, that bycatch mitigation research in other fisheries with larger detrimental population level impacts to species of concern may potentially yield greater conservation benefits.

A comparison of circle hook and J hook performance in a western equatorial Atlantic Ocean pelagic longline fishery

Catch composition, catch rates, hooking location, and status at release at haulback were monitored during 81 experimental sets (launches and hauling fishing per day) in a commercial pelagic longline fishery targeting tuna in the equatorial South Atlantic Ocean. Circle hooks (size 18/0, 0° offset) and J-style hooks (size 9/0, 10° offset) with squid baits were deployed in an alternating fashion. The catch composition was not significantly different for most species between the two types of hooks, except for bigeye tuna, which showed a significantly higher proportion of catches on the circle hook ( p ≫ 0.001) and for sailfish, pelagic stingray, and leatherback sea turtle, which had higher catch rates on the J-style hook ( p = 0.018, p ≫ 0.001, and p = 0.044, respectively). Bigeye and yellowfin tuna showed significantly higher rates of survival at the time of gear retrieval with circle hooks, and circle hooks hooked bigeye tuna, yellowfin tuna, swordfish, and sailfish significantly more often externally than internally. Our results suggest that the use of size 18/0, 0° offset circle hooks in the equatorial pelagic longline fishery may increase the survival of bycatch species at the time of gear retrieval with minimal effects on the catches of target species.

Effect of changes in hook pattern and size on catch rate, hooking location, injury and bleeding for a number of tropical reef fish species

The Queensland Great Barrier Reef line fishery in Australia is regulated via a range of input and output controls including minimum size limits, daily catch limits and commercial catch quotas. As a result of these measures a substantial proportion of the catch is released or discarded. The fate of these released fish is uncertain, but hook-related mortality can potentially be decreased by using hooks that reduce the rates of injury, bleeding and deep hooking. There is also the potential to reduce the capture of non-target species though gear selectivity. A total of 1053 individual fish representing five target species and three non-target species were caught using six hook types including three hook patterns (non-offset circle, J and offset circle), each in two sizes (small 4/0 or 5/0 and large 8/0). Catch rates for each of the hook patterns and sizes varied between species with no consistent results for target or non-target species. When data for all of the fish species were aggregated there was a trend for larger hooks, J hooks and offset circle hooks to cause a greater number of injuries. Using larger hooks was more likely to result in bleeding, although this trend was not statistically significant. Larger hooks were also more likely to foul-hook fish or hook fish in the eye. There was a reduction in the rates of injuries and bleeding for both target and non-target species when using the smaller hook sizes. For a number of species included in our study the incidence of deep hooking decreased when using non-offset circle hooks, however, these results were not consistent for all species. Our results highlight the variability in hook performance across a range of tropical demersal finfish species. The most obvious conservation benefits for both target and non-target species arise from using smaller sized hooks and non-offset circle hooks. Fishers should be encouraged to use these hook configurations to reduce the potential for post-release mortality of released fish.

Catch‐and‐Release Mortality in Subadult and Adult Red Drum Captured with Popular Fishing Hook Types

AbstractSaltwater anglers along the entire coast of the southeastern United States target red drum Sciaenops ocellatus more frequently than any other recreational fish species. The frequency of catch‐and‐release angling has increased dramatically for this species in the past two decades, but little is known about the survival of released fish. This study demonstrates that catch‐and‐release mortality rates for subadult and adult red drum differed significantly among the most popular types of fish hooks in each fishery. To investigate the effect of hook type on anatomical hooking location and short‐term (48‐h) mortality, we captured subadults (339–825 mm total length (TL)) by use of 2/0 J‐hooks (n = 57 fish), 4/0 nonoffset circle hooks (n = 58 fish), and 4/0 offset circle hooks (n = 57 fish). Nonoffset circle hooks penetrated shallow regions of the body (jaw, tongue, or inside of mouth) significantly more frequently (90%) than did J‐hooks (60%) or offset circle hooks (80%). Nonoffset circle hooks also resulted in the lowest rate of subadult mortality (2%). Adults (660–1,138 mm TL) were captured on bottom longline gear with 7/0 J‐hooks (n = 60) and 9/0 nonoffset circle hooks (n = 107). The frequency of deep hooking in adults was significantly higher for J‐hooks (30%) than nonoffset circle hooks (3%). Only deep hooked fish were monitored for 48‐h survival. Adult mortality after 48 h was lower for nonoffset circle hooks (1.9%) than for J‐hooks (3.3%). These mortality rates should be considered in future red drum stock assessments.

Effects of circle versus J-style hooks on target and non-target species in a pelagic longline fishery

The U.S. Atlantic coastal pelagic longline fishery that targets tunas and swordfish also interacts with a wide range of non-target species including billfishes and sea turtles. Preliminary studies indicate that a change in terminal gear from J-style hooks to circle hooks may reduce bycatch mortality, but the effects of this change on catch rates of target species are unclear. To evaluate this, we monitored catch composition, catch rates, hooking location, and number of fish alive at haulback during 85 sets in the fall and spring seasonal fisheries from a commercial vessel operating in the western North Atlantic. Circle (size 16/0, 0° offset) and J-style (size 9/0, 10° offset) hooks were deployed in an alternating fashion. Hook–time recorders were used to assess time at hooking and temperature–depth recorders to measure gear behavior. Catch rates for most species categories were not significantly different between hook types ( P < 0.05), although circle hooks generally had higher tuna catch rates in the fall and lower swordfish catch rates in the spring. In the fall, both total catches and catches of pelagic rays were significantly higher on J-style hooks. Yellowfin tuna in the fall and dolphinfish in the spring caught on circle hooks were significantly larger than those caught on J-style hooks. In both seasonal fisheries, circle hooks caught fishes in the mouth more frequently than J-style hooks, which hooked more often in the throat or gut, although these differences between hook types were not statistically significant. Yellowfin tuna in the fall fishery were over four times more likely to be hooked in the mouth with circle hooks than with J-style hooks. Several target and bycatch species showed higher rates of survival at haulback with circle hooks, although only for dolphinfish in the fall fishery was this difference statistically significant. Our results suggest that the use of 0° offset circle hooks in the coastal pelagic longline fishery will increase the survival of bycatch species at haulback with minimal effects on the catches of target species.

Largemouth bass catch rates and injury associated with non-offset and offset circle hook configurations

Although circle hooks are being viewed as a means to reduce injury and mortality of recreationally caught-and-released fish, subtle differences in hook configuration (such as the degree that the hook point is offset from the shank) could affect performance. We compared hooking and landing efficiency, anatomical hooking depth and location, ease of hook removal, and amount of bleeding between largemouth bass angled on either non-offset (0°) or slightly offset (2°) circle hooks. Non-offset circle hooks were more efficient at hooking and landing largemouth bass than the offset design. Fish were hooked more deeply with non-offset hooks; non-offset hooks penetrated the corner of the mouth whereas the offset hooks penetrated the terminal upper and lower lip. Overall, there were no differences in the frequency that fish were hooked in potentially lethal locations (e.g. gullet, eye). The design and hooking location of non-offset hooks led to greater difficulty in hook removal and slightly higher rates of bleeding. Offset circle hooks have been identified as more injurious in previous studies but we found little difference in injury that may lead to serious infection or mortality between hook types. Given that non-offset circle hooks have a higher capture efficiency for largemouth bass, anglers will likely adopt their use.

The Effects of Catch‐and‐Release Angling on the Growth and Survival of Juvenile White Seabass Captured on Offset Circle and J‐Type Hooks

AbstractDespite the growing number of recreational anglers targeting white seabass Atractoscion nobilis in California, no information is available on the mortality rates of juveniles following catch and release. We captured juvenile white seabass (430–577 mm total length) with 4/0 offset circle hooks (n = 113) or 4/0 J‐type hooks (n = 108) or with a net (control, n = 30) to investigate the effect of hook type on anatomical hook location. We also examined how hook location affected growth and survival for 90 d following release. Offset circle hooks penetrated the lip region significantly more frequently (73%) than did J‐type hooks (41%). Hook location was directly correlated with mortality; all mortalities involved hook damage to the visceral region. A 10% postrelease mortality rate was observed for fish caught on both offset circle and J‐type hooks. All mortalities occurred within 5 d postrelease. Survival was enhanced when deeply embedded hooks were left in place rather than removed from the visceral tissue. Hook‐caught fish showed no reduction in growth when compared with control fish, but deeply hooked fish grew at a significantly lower rate than did fish hooked in the mouth. Angler success rates did not differ significantly between hook types. We recommend that catch‐and‐release mortality be incorporated into the management plan for white seabass.

Mortality rate of striped marlin (Tetrapturus audax) caught with recreational tackle

A project was initiated in the autumn of 2000 to document the mortality of striped marlin caught on recreational fishing tackle, with a follow-up study conducted in autumn of 2001. Fish were caught using typical recreational fishing methods and 80 pop-up satellite archival tags were deployed with new software and mechanical release mechanisms that allowed tags to detach and transmit early if the fish died. The first year study was also designed to compare the effectiveness and associated mortality of circle hooks versus J-hooks, while the second year study compared offset and non-offset circle hooks. All fish were caught on live bait. Circle hooks were found to be equally effective in hooking and landing striped marlin and far less likely to cause serious bleeding or become lodged in areas other than the mouth. Non-offset and 5° offset circle hooks had very similar performance. Depth and temperature records allowed us to determine the fate of individual marlin following release. In total, 16 of 61 fish died (mortality rate of 26.2%), all within 5 days of release (mean 1.5 days). Injury was a clear predictor of mortality; 100% of fish that were bleeding from the gill cavity died, 63% of fish hooked deep died, and 9% of those released in good condition died.