Do hooks really rust out?
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Joisey Joe
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I have been monitoring Fish-Hawk for a few years and figure it is time to start contributing!
Our lab (no need to be cryptic - Cooke Lab at Carleton) has been engaged in some local research on this topic. I attach an abstract from a study that we did on Lake Opinicon - it has been accepted for publication in a peer reviewed journal (Fisheries Research). The caveats are that our "long term" time point was only ten days. We are following up this work in 2009 by varying hook size, hook type, and presence of the barb (barbed vs barbless).
Here is the abstract: Research on a wide range of fish species has revealed that deep hooking is perhaps the single most important determinant of injury and post-release mortality in recreational fisheries. However, there is little information on the best option for dealing with deeply hooked fish that are to be released; should the line be cut or should the hook be removed? Using bluegill sunfish (Lepomis macrochirus) as a model we investigated sublethal (e.g., swimming performance, physiological condition, injury levels) and lethal consequences associated with removal of deeply ingested hooks versus cutting the line and leaving the hook embedded in the esophagus, relative to shallowly hooked controls. Neither hook retention nor deep hook-removal altered the swimming performance of the fish in this study relative to controls. However, there was evidence of short-term physiological disturbance. For example, hematocrit was reduced for fish that had hooks removed, consistent with visual observations of bleeding. In addition, blood glucose levels tended to be higher and plasma Na+ levels tended to be lower in deeply hooked fish that had hooks removed indicating stress and ionic imbalance even 24 hrs after capture. During holding experiments we noted the highest mortality levels in fish for which the hook was removed (33 % after 48 hrs and 44 % after 10 days). Mortality rates were lowest for the controls (0 % after 48 hrs and 4 % after 10 days) and intermediate for the line-cut treatment (8 % after 48 hrs and 12.5 % after 10 days). After 48 hrs, 45.5 % of the fish from the line-cut treatment group were able to expel the hook originally embedded in their esophagus, and at the end of the 10 day study, 71.4 % had expelled the hook. Even with the hook left in the esophagus, fish were able to feed although at lower rates than controls during the first 48 hrs of holding. By 10 days post-capture, there were no differences in feeding rates as evidenced by growth patterns among the treatment groups, nor were there differences in the hepatosomatic index. Collectively, the findings from this study demonstrate that cutting the line is a more effective release method than removing the hook when fish are deeply hooked. As such, angler education efforts should focus on disseminating this message to anglers as well as encouraging the use of gear and techniques that minimize incidences of deep hooking (e.g., circle hooks, non-organic bait).
Just a few comments on the "hook experiment" that spawned this entire forum discussion... The experimental design is flawed. The hook placement is not appropriately replicated so one must not put much faith in the findings (this is evidenced in the photo in their article - a more robust design would be to alternate hook types). As pointed out by several posters, local environmental conditions will influence rusting rates. In freshwater we rarely see much rust on lures that we encounter in fish (recaptured) or in lures that we find during snorkeling. However, when hooks are found in the digestive tracts of fish we do see some evidence of rusting.
SJC
Our lab (no need to be cryptic - Cooke Lab at Carleton) has been engaged in some local research on this topic. I attach an abstract from a study that we did on Lake Opinicon - it has been accepted for publication in a peer reviewed journal (Fisheries Research). The caveats are that our "long term" time point was only ten days. We are following up this work in 2009 by varying hook size, hook type, and presence of the barb (barbed vs barbless).
Here is the abstract: Research on a wide range of fish species has revealed that deep hooking is perhaps the single most important determinant of injury and post-release mortality in recreational fisheries. However, there is little information on the best option for dealing with deeply hooked fish that are to be released; should the line be cut or should the hook be removed? Using bluegill sunfish (Lepomis macrochirus) as a model we investigated sublethal (e.g., swimming performance, physiological condition, injury levels) and lethal consequences associated with removal of deeply ingested hooks versus cutting the line and leaving the hook embedded in the esophagus, relative to shallowly hooked controls. Neither hook retention nor deep hook-removal altered the swimming performance of the fish in this study relative to controls. However, there was evidence of short-term physiological disturbance. For example, hematocrit was reduced for fish that had hooks removed, consistent with visual observations of bleeding. In addition, blood glucose levels tended to be higher and plasma Na+ levels tended to be lower in deeply hooked fish that had hooks removed indicating stress and ionic imbalance even 24 hrs after capture. During holding experiments we noted the highest mortality levels in fish for which the hook was removed (33 % after 48 hrs and 44 % after 10 days). Mortality rates were lowest for the controls (0 % after 48 hrs and 4 % after 10 days) and intermediate for the line-cut treatment (8 % after 48 hrs and 12.5 % after 10 days). After 48 hrs, 45.5 % of the fish from the line-cut treatment group were able to expel the hook originally embedded in their esophagus, and at the end of the 10 day study, 71.4 % had expelled the hook. Even with the hook left in the esophagus, fish were able to feed although at lower rates than controls during the first 48 hrs of holding. By 10 days post-capture, there were no differences in feeding rates as evidenced by growth patterns among the treatment groups, nor were there differences in the hepatosomatic index. Collectively, the findings from this study demonstrate that cutting the line is a more effective release method than removing the hook when fish are deeply hooked. As such, angler education efforts should focus on disseminating this message to anglers as well as encouraging the use of gear and techniques that minimize incidences of deep hooking (e.g., circle hooks, non-organic bait).
Just a few comments on the "hook experiment" that spawned this entire forum discussion... The experimental design is flawed. The hook placement is not appropriately replicated so one must not put much faith in the findings (this is evidenced in the photo in their article - a more robust design would be to alternate hook types). As pointed out by several posters, local environmental conditions will influence rusting rates. In freshwater we rarely see much rust on lures that we encounter in fish (recaptured) or in lures that we find during snorkeling. However, when hooks are found in the digestive tracts of fish we do see some evidence of rusting.
SJC
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Joisey Joe
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- Joined: Fri Oct 18, 2002 7:25 am
- Location: Landing, NJ
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fishead-ed
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