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How many times have you watched a mate or experienced angler cut the leader instead of remove the hook from the mouth of a fish? It’s standard practice in most billfish tournaments. Crews don’t want to waste valuable tournament time, they don’t want to get injured handling a fish and there’s increased physiological stress to the fish the longer the crew handles them. I recently fished the 2007 Yamaha Contender Miami Billfish Tournament. Over 500 billfish were caught and released. The following week the top teams traveled to Key West to catch another 500-plus fish. That means there were up to 1,000 sailfish swimming around with hooks in their mouths. It made me wonder how long these hooks stay in the fish, and if the fish actually survive.

Everyone’s got a different claim as to how fast hooks rust out and how much harm they do to the fish. Capt. Nate Goodwin of the My Three Sons, a top tournament competitor, estimates that it takes two months for a hook to rust out or dislodge. Capt. Court Vernon, of Capt. Harry’s Fishing Supply, surmised that embedded hooks would rust out in a few days. Vernon was so interested in this topic that he graciously donated hooks for Worldwide Angler’s experiment.
South Florida fishing luminary Capt. Bouncer Smith says, “I catch fish all the time with hooks in their mouths and stomachs.” He believes hooks can stay in a fish for a year or more. Some of his previously caught fish have small amounts of leader attached to the hook, but he has never caught a fish with more than five feet of leader attached. He’s convinced that leaving long leaders kills fish. He cites ESPN’s Billfish Extreme Release League’s (BXRL) rule that no more than three feet of leader may be left on the fish after releasing. Bouncer believes that all billfish tournaments should implement leader retrieval rules similar to those in the BXRL.

With these questions in mind, I decided to enlist the help of a high school buddy, marine biologist Dr. Adam Ludwig. We researched many scientific journals. Here’s what we came up with.  

THE SCIENCE BEHIND CUTTING THE LEADER

According to a study published in 2002 by Ron Taylor of the Florida Fish and Wildlife Research Institute (FFWRI), circle hooks were shown to result in significantly lower hooking mortality and higher catch rates in several species. Controlled studies have also shown that most fish released after hook and line capture survive. Researchers working in Boca Grande Pass, using sonic transmitters that popped off after an average of about five hours, found 26 of 27 tarpon survived release from hook and line, according to R.E. Edwards as reported in Gulf of Mexico Science. Other studies, as conducted by the FFWRI, as well as a 2005 report by A. Bartholomew and J.A. Bohnsack in Fish Biology and Fisheries, demonstrated that fish hooked in the gills or gut experience lower survival rates than those hooked in the mouth.

That said, cutting the leader can be a good idea. Higher post-release survival rates are observed in deeply hooked fish (throat or gut) when the leader is cut rather than attempting to remove the hook. A 2004 study of white seabass by Aalbers, Stutzer, and Drawbridge that appeared in the North American Journal of Fisheries Management, showed 65 percent of deeply hooked fish died when hooks were removed compared to 41 percent when hooks were left embedded. Also, FFWRI found that four of 12 deep-hooked snook died when the hook was removed compared to zero of 12 when the leader was cut. Angler expertise involved in capture, hook removal, and release directly contributes to the overall physiological stress on the fish. The struggle and trauma associated with deep hook removal can lead to exhaustion, causing physiological imbalance, muscle failure and even death. Therefore, it is clear that sometimes it’s better to cut the leader, especially when increased handling may do more harm than good.

LONG-TERM SURVIVAL?
What is not as well researched is longterm effects of embedded hooks on fish and how long it actually takes for hooks to rust out. Some research indicates that fish with embedded hooks are capable of rejecting, expelling or encapsulating them. Recent scientific evidence suggests hooks may actually remain intact for several months. According to one study, stainless steel hooks (Owner SSW 4/0 J-type hook and Owner 4/0 Super Mutu Lite offset circle hook) were only 50 percent degraded after being submerged 90 days and 90-100 percent degraded after 150 days. That’s nearly five months. Many factors would work together to determine the length of time embedded hooks could remain intact. Composition of the hook, water movement, temperature, and pH of the fish’s tissue may all be important factors affecting rates of hook corrosion. 

Even less is known about how an embedded hook might affect survivorship in released fish. Of particular interest would be to study the physiological, immune and growth effects of prolonged hook attachment. After reviewing the evidence in the four articles cited above, Adam and I decided to conduct our own experiment. Ideally we would put sonic tags on a bunch of sailfish with hooks stuck in their mouths and compare survival rates, but that would have required major funding. We decided to simply take hooks commonly used in billfish tournaments, submerge them in saltwater and determine how quickly they corroded.

THE WORLDWIDE ANGLER HOOK TEST

Submerged Hook Experimental Design:
We decided to perform a side-byside comparison of three of the leading tournament circle hooks provided by Capt. Harry’s Fishing Supply. We tested Mustad (#3995 BLN 5/0), Eagle Claw (#L2004 ELG 7/0), and Owner (#5379151 5/0) hooks by submerging them in seawater and checking every three days for signs of rust. Six hooks from each brand were embedded in foam. The foam was attached to a concrete block for submersion. This hook-testing device was submerged in seawater below the docks at Miami Beach Marina, Miami Beach, Fla. We recorded the time (number of days) it took for initial signs of rust or corrosion to appear. We also recorded the time (number of days) until a hook exhibited greater than 50 percent rust coverage and greater than 90 percent rust coverage.   

Submerged Hook Results:
At press time our experiment had been hanging from the dock for 36 days. After nine days submerged in seawater, the Mustad and Owner hooks were the first to show signs of rust (Table 1 and Figure 1). The first sign of corrosion was detected at the eye of the hook for all Mustad hooks and at the barb for all Owner hooks. At nine days, the Eagle Claw hooks showed degradation to the rust-proof coating but no signs of rust were detected. By nineteen days, the Eagle Claw hooks showed their first signs of rust and within 36 days all Eagle Claw hooks were more than 50 percent rusted (Table 1 and Figure 1). None of the Mustad or Owner hooks had reached greater than 50 percent corrosion at press time. Although the Eagle Claw hooks took longer to show signs of initial corrosion, they appeared to oxidize more thoroughly over 36 days.  

CONCLUSION:
There’s no simple answer as to how long it takes for hooks to rust out or how harmful they may be to fish. We did learn that none of the hooks tested will “rust out in a couple of days,” as some anglers believe. In fact, it seems more likely that embedded hooks would become dislodged, expelled or encapsulated before they would be lost due to rust. More in-depth research is needed to determine the long-term effects of embedded hooks on gamefish. In most circumstances, removal of the hook is preferred, but with deeply hooked fish, this may do more harm than good. As a rule of thumb, if you’re going to cut the leader, we suggest cutting as close to the hook as possible. This will reduce the probability of entanglement, mucus membrane irritation and swimming impairment.

We will continue to monitor the submerged hooks until they reach greater than 90 percent corrosion. In addition, we are planning a second experiment using hooked baitfish in pens to monitor corrosion, dislodged or expelled hooks and survival. We are also looking into hooks that are manufactured with “weak points,” designed to oxidize faster than the surrounding metal (U.S. Patent 4715142), and dehooking devices that make removal of circle hooks easier.

We welcome any technical or material assistance with this project. Stay tuned for future updates, and feel free to contact us with your personal experiences and comments via our survey below.

TELL US WHAT YOU KNOW

If you thought this article was interesting, take a minute and email us your answers to the below survey to scott@worldwideanglermag.com. Put “rusty hooks” in the subject line.

1. Approximately what percentage of fish do you release via cut-leader release during tournament fishing?

2. Do you ever catch billfish with embedded hooks? If yes, how frequently? Are the hooks corroded or not?

3. How long is the leader material on the embedded hooks you see? Do you ever see more than five feet of leader material on a live fish?