Info for catch and release fisherpeople

[mrfish 327]

Hi all,Just came across this recent study and thought it might be interesting to a few of you and give you something to consider when selecting your tackle. (If you cant be bothered reading it all then it basically says that stainless steel hoooks dont oxidize quickly whereas carbon steel does, using hooks with baitholders promoted oxidation as it provides a weak point for decay and breakages. diametre of hooks at 0.9mm are better options for fast decay )Reviewing hook degradation to promote ejection afteringestion by marine fish 2011Shane P. McGrathA, Paul A. ButcherB, Matt K. BroadhurstB,Dand Stuart C. CairnsCAbstract. Awidely recommended strategy for releasing fish that have ingested hooks is to simply cut the line. The utilityof this approach is based on the premise that the individual will eventually eject the hook following sufficient oxidation.However, few quantitative data are available describing the mechanisms affecting hook decay. We addressed this issue bytesting the independence of various technical factors on the degradation of 828 hooks comprising 23 designs (absolutesizes 227–611mm2) after protracted submersion in seawater. Twelve replicates of each hook were destructively assessedfor compression and tensile strengths (using a force gauge) and 24 replicates were weighed, photographed and submersedin seawater. After submersion for 8 and 28 days, 12 replicate hooks were removed, re-photographed, re-weighed and testedfor compression and tensile strengths to provide indices of decay. Hook degradation was mainly affected by the wirematerial and diameter and could be significantly promoted by choosing carbon steel designs, either with a wire diameter of#0.9mm for the examined sizes or, alternatively, bait-holder barbs (or similar modifications) along the shaft. By rapidlyoxidising and weakening after ingestion, such designs could ultimately help to reduce negative impacts of hooks onreleased fish.Some excerpts of interest from the article" HOOK WEIGHT: At the end of the experiment (28 days), none of stainless-steel hooksappeared to be oxidised, whereas the carbon steel designs werereduced to as little as 95% of their original weights.""HOOK POINT: Although stainless-steel hooks retained theirinitial point length, carbon-steel hooks had only 92.06%remaining after 28 day.""Irrespective of all other parameters, the wire material had thestrongest impact on oxidation and strength. Unlike the carbonsteelhooks, after 28 days in seawater, the stainless steel designsretained most of their initial strengths, weights and pointlengths; which means that the latter remained sharp. This resultis important since, once ingested, stainless-steel hooks would beexpected to have a greater probability of penetrating soft tissueand vital organs during progression through the digestive tract. By comparison, after 28 days of submersion, the carbon-steelhooks were significantly oxidised to a condition whereby somehad less than 95 and 38% of their initial weights and hook pointsrespectively. "Bait-holderbarbs and similar modifications to wire diameter could be anappropriate strategy for increasing the probability of bothstainless- and carbon-steel hooks breaking and the latteroxidising, after ingestion. In support of such effects, Broadhurstet al. (2007) attributed the bait-holder barbs on nickel-platedcarbon-steel hooks to rapid decay and weak points on theshaft which facilitated breakage (often within 3 weeks) duringingestion by yellowfin bream.""In the interim, anglers should be encouraged to avoidstainless-steel hooks and choose carbon steel designs with thenarrowest wire diameter. Based on the results here, hooks withsimilar absolute sizes, but made from a wire diameter of lessthan ,0.9mm should still provide sufficient tensile strength,while promoting rapid oxidation and subsequent breakage.Existing hooks (including stainless steel designs) with thickerwire could be easily modified by anglers to make them weaker,by incorporating notches similar to bait-holder barbs. Suchmodifications could help to reduce unaccounted fishing mortalityand further validate catch-and-release as an appropriatemanagement tool for conserving stocks."