Letter to FWC chairman from Dr. Justin Grubich regarding 2002-2004 Foul Hooking Tarpon study

Dr. Justin Grubich letter to FWC 2013Letter from Dr. Justin Grubich as PDF.

This letter, dated May 8, 2013, was sent to FWC Chairman, Kenneth Wright by Dr. Justin Grubich regarding the 2002-2004 Foul Hooking Tarpon study.

To read the entire article accompanying this letter, please see Expert named in FWC study speaks out: The jig snags tarpon.



Justin R. Grubich Ph.D.
Associate Director of Biodiversity Informatics

May, 8th, 2013

Ken Wright, Chair
Florida Fish and Wildlife Commission

Dear Mr. Wright,

Recently, I was contacted by Randy White and Bill Bishop in regards to my involvement with the 2002-2004 Foul Hooking Tarpon study in Boca Grande Pass. Their contention, as you are well aware, is that the unique jigging technique known as break-away jigs used in Boca Grande Pass to catch tarpon is an illegitimate method used to foul-hook or ‘snag’ these fish when they are not exhibiting feeding behaviors. They contacted me to ask if I would review the outcomes of the study and whether my involvement has been accurately represented in the FWC’s 2003 summary report.

I have to admit I have not followed this issue since I was first contacted by the FWC to provide expert testimony on the feeding behavior of tarpon. As you are probably aware, I was contacted by the FWC sometime around 2003-4 because of my 2001 research publication regarding the strike kinematics and jaw functional morphology of juvenile tarpon. My recollection of that phone call was approximately a 30 minute discussion where I was briefly informed of the Boca Grande jigging issue and asked a series of questions of how tarpon jaws work during the strike and whether it’s possible these jig’s hook placement in the clipper could be the result of feeding behavior.

Prior to being contacted by the FWC, I had no experience or background knowledge of the Boca Grande tarpon fishery or the techniques used, including what and how a break-away jig works which truth be told was not effectively communicated to me by the FWC representative during the interview. My lack of familiarity with the issue and jigging technique was correctly pointed out by Mr. White on his web page regarding my original testimony.

However, I would like to point out to the Commission and all parties involved that I am not just a scientist in a lab dissecting fish. I am also an avid angler and an IGFA International Committee Representative. I have been fishing for tarpon since the early 80’s in the Florida Keys and Everglades. As a teenager, I worked as a first mate on a Key West charter boat and after college spent two years as a NMFS observer on commercial longline vessels. So, beyond being a scientific expert in fish functional morphology, I think I am also uniquely qualified to review and comment on the ‘fishing’ side of this issue.

That said, I would first like to clarify some misrepresentations of my testimony that is now part of the public record on the FWC website regarding the 2002-2003 Boca Grande Tarpon Catch and Release Mortality Study results. I am quoted as saying that tarpon “can miss during the strike’ and ‘invariably turn their heads after the strike which is how they ARE getting snagged in their clipper plates”.

First of all, missing prey during the strike is a characteristic of all predators and is a quite common occurrence as any angler will frustratingly acknowledge. If predatory fish never missed, there would be no prey left and eventually no predators either. So that statement really is not unique to the discussion of tarpon feeding. I’ll elaborate more on this topic later in the letter. Second, my point about tarpon turning away after the strike and getting ‘snagged’ in the clipper plates should not be taken as a definitive statement to explain all hook placements in the clipper plate.

I was simply providing a plausible scenario from my knowledge of tarpon feeding behavior for why hook placement in the clipper plates MAY occur after a strike. That’s not to say there are not other plausible or more probable ways for hook placement to occur in the clipper plates depending on the specific fishing scenario and techniques being used. My statement was simply referring to the fact that the maxilla (clipper plate) is the largest bone of the upper jaw mechanism in tarpon with a broadly lateral orientation that consequently provides a large surface area for the hook point to snag, penetrate, or wrap around (in the case of large gap hooks).

Lastly, my use of ‘snag’ or ‘snagging’ at that point in time was meant to indicate a purely mechanical definition of the hook gaining purchase in the fish’s mouth region, head, or even body regardless of whether it was coincident with an intentional feeding strike or not. To be clear, it was not based on any previous knowledge of fishing definitions or FWC regulations regarding foulhooking or snagging. I was admittedly ignorant of such semantic issues then.

This brings up my last point regarding my testimony and its portrayal in the FWC report and website. Let me reiterate my whole involvement with this issue revolves around a single discussion. At no point in time was any background material of the break-away jig issue, the tarpon fishery at Boca Grande Pass, or the initial 2002-2003 results of the catch and release mortality study ever provided to me before or after my interview.

So, my original testimony should not be taken to support either position, as it was not based on a thorough review of the issue or any experimental evidence regarding fishing techniques and catch and release mortality in which I participated.

I have since tried to educate myself on the techniques of break-away jig fishing and the environmental conditions of the Boca Grande Pass tarpon fishery. I have also reviewed the summary report that includes more data from 2004 than the original FWC website 2002-2003 results where I am quoted. After reviewing both reports, I have to concur with Dr. Motta’s testimony reversal that the evidence indicates break-away jigs result in higher foul hooking percentages.

The current FWC definition identifies any hook placement in or around the mouth regardless of orientation as a non-foul hooked fish. Even with this more conservative definition, the results show that break-away jigs still have significantly greater foul hook placement in other parts of the tarpon compared to live bait, although the report suggests the percentage is not unusual compared to other foul hook estimates in other fisheries. However, IF hook orientation is taken into account to include foul hooking as when the hook is driven from the outside into the mouth cavity in either the upper or lower jaws, then the percentage of foul hooking associated with break-away jigs would be 7/26 (27%) for the 2003 results on the FWC website. This foul hooking percentage defined by hook orientation is substantially higher (> 10%
difference) than foul hook estimates in other popular recreational fisheries including salmon fisheries.

The reason hook orientation may important to the discussion of foul hooking is because it is indicative of the behavioral intent of the tarpon. Did the tarpon attempt to capture the lure or bait via a feeding strike? You see, in addition to
using swimming speed to overtake elusive prey, tarpon employ a suction feeding strategy whereby they rapidly expand their jaws and buccal cavity to literally suck the prey backwards into their mouths. Now, the thing about suction generation in fishes is that due to hydrodynamic constraints and the viscosity of water, it is only really effective in a small area just in front of the mouth aperture.

The amount of drag induced on a prey item (i.e. suction force) during a strike rapidly decreases as the distance to the prey becomes greater than 50% of the mouth’s maximum gape. So for even the largest tarpon that means their effective suction strike distance would be less than 6 inches. What does this have to do with hook orientation?

Well, if a tarpon is actively feeding, it will be employing these suction strikes in focused efforts directly in front of their opening jaws to maximize the suction force on the bait or lure in order to draw it into their mouth cavity. And, that means upon closing the jaws around the prey and then turning away, the hook set will most likely be oriented from inside the mouth cavity to the outside of the jaws as indicated by 100% of the live bait results from 2003.

In contrast, less than 50% of the break-away jigs’hook orientation indicate an active suction feeding strike may have been employed by the tarpon. But, in my original testimony, I was quoted as saying tarpon can miss the target during the strike and potentially still get hooked. Indeed they can and often do miss elusive prey, but that probability is greatly diminished with dead drifting tethered baits or lures that are not employing or mimicking escape behaviors.

Even with live baits that have some restricted escape mobility, the 2003 results show tarpon successfully engulfed the prey into the mouth cavity every time indicating an intentional feeding strike. So, with a non-moving or slowly drifting target, tarpon are even less likely to miss and be foul hooked in an outside/in manner during an intentional suction feeding strike.

Whether or not the flossing tactic commonly referred to in salmon fishing circles is also applicable to the break-away jigging technique used in Boca Grande Pass remains to be scientifically verified. Underwater video footage of the break-away jigging technique would be a good start to ascertain the validity of that claim.

However, I will note that the morphology and mechanics of the tarpon clipper plate have features that make ‘flossing’ a plausible scenario. For example, the maxilla of a tarpon includes a continuous ridge of small villiform teeth that line the entire ventro-lateral margin of this enlarged bone.

These tiny velcro-like teeth are very good at grasping slippery objects (usually fleeing fish prey) but are equally good with monofilament as any good tarpon angler can attest to their abrasive abilities on leader material. Even when the maxilla is in its resting (non-suction feeding) position these tiny teeth are exposed from the tip of the jaws to its posterior margin and could provide a roughened snag point for monofilament drifting past even when the fish is not exhibiting feeding behavior. Fish will often shake their head and/or quickly snap their jaws (not to the extent of a full suction strike) when something irritates their head.

Tarpon stacked up like cordwood facing into the current in Boca Grande Pass may be exhibiting such a snapping behavior of the head and jaws in response to the irritation of hundreds of lines of monofilament sliding past them and snagging on the villiform teeth of their maxillae. The angler might perceive this nonfeeding behavior as the tell-tale tap when using the break-away jig. In addition, keep in mind whenever the lower jaw of a tarpon is opened beyond a 10 degree rotation, it causes the maxilla to swing forward and flare laterally (the extent of which is directly linked to the amount of lower jaw rotation).

This lateral expansion and the gripping action of the villiform teeth can cause the monofilament to be threaded between the inside surface of the clipper plate and the cheek (aka suspensorium) facilitating a snagging hook set with an outside/in orientation. So, you can see how non-feeding motions and the morphology of the tarpon’s jaws could result in foul-hooking or snagging tarpon in the mouth when they are not actually intending to feed. This specific flossing scenario of how break-away jigs may work in the Boca Grande Pass tarpon fishery is of course a hypothesis that would need to be tested.

In closing, I appreciate the opportunity to set the record straight regarding my original testimony and hope these additional insights into tarpon feeding behavior and functional morphology are informative. If I can be of any further
assistance regarding this issue, please feel free to contact me.

Kindest Regards,

Justin Grubich


Useful links:

FWC Summary Report on the Catch-and-Release Mortality Study on Tarpon 
in Boca Grande Pass, 2002–2004

2002-2003: Incidence of Foul-hooking in FMRI* Boca Grande Pass Tarpon Catch and Release Mortality Study

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