HOOK WOUNDS ON FISH:
HOW MUCH DAMAGE DOES YOU HOOKS MAKE?
Big hooks makes bigger lesions on the fish compared to smaller hooks: The deeper the hookpoint penetrate, the higher is the risk of cutting deeper lying major bloodvessels or making lethal damages on organs such as heart or brain. In order to put comparative figures on the potential lesions from different hooks, I have measured the exact proportions of some of the most popular salmonid hooks for spin- and flyfishing – and calculated the potential acreage and volume of the wounds.
Text and photos: Jens Bursell
ITS QUITE LOGICAL that a big hook leads to bigger lesions if it´s fully penetrated. This is also the conclusion in scientific works such as “Mortality of Chinook and Coho Salmon in Their First Year of Ocean Life following Catch and Release by Anglers (T. Gjernes, A.R. Kronlund and T. J. Mulligan – 1993) who concludes: “Proportionately larger hooks can lead to injuries, that are more severe than injuries from smaller hooks in two ways. First, the longer points penetratemore deeply before the bend of the hook is reached. Second, the greater gape of a large hook permits the hook point to impinge on central parts of the head before the shank contacts the periphery of the jaw. Thus, a larger hook is more likely to wound sensitive areas such as the gills, large blood vessels, or the brain.”
Left: An arched cone describes well the potential internal lesion from hooks. Right: The distance from hookpoint to start of bend (r = column “F”) was measured to calculate the volume of the lesion from the formula Volume = 2¶/3 x r3 (1-cosV).
In order to compare the potential lesions from different hooktypes (trebles vs doubles vs singles), patterns and hooksizes, I measured the exact dimensions and calculated volume of lesions making the assumption, that the best geometric shape describing internal lesions is an arched cone. Depending on the angle of pressure and the way the fish moves and rolls during the fight - the shape of the internal lesion could have many forms, but for a simple comparison of potential damage from different hooks, I think this is a good average scenario who illustrates the point quite well.
THE VOLUME of an arched cone was calculated from the formula:Volume = 2¶/3 x r3 (1-cosV), where V is the angle of the cone (see formula in column “G” in the excel-file “hooklesions.xls” in the article-archive on R = radius is in this case the distance from hookpoint to start of bend (r = column “F”). This formula have been verified by professor Bergfinnur Duurhus from Mathematical Institute in Copenhagen, Denmark.From practical experience we know, that the frequency of when the fish is hooked on 1, 2 or 3 branches is approximately 0,5 : 0,4 : 0,1(ref: Jens Bursell, Henning Trier and Jesper Fohrmann). Based on this we found the weighted average of damage from trebles in column “J”. Additionally we know from practical experience with double hooks (ref: Jesper Fohrmann), that the frequency of where the fish is hooked on 1 or 2 branches is approximately 0,1 : 0,9. Based on this we found the weighted average of damage from doubles in column “J”.
THEACREAGEof the scar was calculated from the formula describing the acreage of a circle (A = ¶ x r2)– where the diameter is wirediameter + height of barb (column “C”)and r is the radius of this diameter (Column “D”).
Based on these calculations its easy to get a rough overview of the potential tissue damage caused by different types and sizes of hooks. It´s clear, that small hooks makes less tissue damage.
THE RELASE-RIG WITH TWO TREBLES – as used for seatrout with in-line lures is a good example on how you harm the fish less with much smaller hooks. The lesion from this rig is calculated in column “V”: We know that in at least 70 % of the cases the fish is only hooked at the end hook. In the other 30 % of the cases it sits on the front hook. Only in some of these cases the fish is hooked on both hooks, but in order not to underestimate the damage made when using two trebles, we have in this example assumed, that the fish is hooked on two different hooks in all 30 % with this frequency: 2 branches - 0,35 : 3 branches - 0,35 : 4 branches - 0,2 : 5 branches - 0,1 (column “T”). Compare the potential damage from the release-rig with two sz 12 trebles with the potential tissue damage from the standard mounting for these type of lures: One very big single – Owner S-61 sz 3/0 – and you will see that the potential scar from this big single is approx. 5 times bigger than for a release-rig with two small trebles!
As a golden rule – the size of the lesion is approximately the same, when the trebles is two standard sizes smaller than the single. Y-axis: Volume of lesion (mm3), X-axis: Hooksize. Lower curve: Volume of lesion when the trebleOwner ST 36 BC X only is penetrated with one branch. Upper curve: Volume of lesion when the same treble Owner ST 36 BC X is penetrated with three branches (weighted average).
IT´S CLEAR TO SEE from the figures in these calculations, that’s its nonsens to discuss how much damage different hook makesin terms of lesions, bleeding and potential risk of infections – without looking a the exact dimensions and type of the hooks: As a good example is small trebles, who makes much less damage than large singles. As a golden rule – the size of the lesion is approximately the same, when the trebles is two standard sizes smaller than the single-hook.
See the original excel.file with all columns and formulas at under articles