AGFC Review of Hooking Mortality Studies

Here is the justification AGFC’s biologist Jeff Williams is presenting for the proposed change in regulations allowing barbed and treble hooks in the catch and release sections on Bull Shoals and Norfork tailwaters. This is a departure from the barbless, single hook rule we have had for many years in the catch and release regulated areas. See the proposals in the post below, “AGFC 2009 Trout Regulation Proposals.”

FYI, Darrell Bowman was the AGFC lead trout biologist prior to Jeff Williams.

The Issue of Hooking Mortality and Trout Management

Jeff Williams – Arkansas Game & Fish Commission

Darrell Bowman – Bella Vista Property Owners Association

Harvest restrictions, such as length limits or catch-and release regulations, have long been a tool for biologists to manage recreational fisheries.  Although length limits were historically implemented to prevent over harvest and protect juvenile fish until they reached maturity, they have also been used to increase the size distribution of fish populations.  Regardless of the type of harvest restriction, the primary goal is to reduce the mortality of fishes in the population of interest.  However, angling related mortality includes direct mortality from harvest as well as post-release hooking mortality of fishes that are caught and released.  Therefore, if the fish anglers are required to release under a particular regulation die anyway as a result of hooking mortality then the ultimate effectiveness of the regulation may be limited.  For this reason, regulations that prohibit certain angling gear generally accompany special regulations such as length limits and catch-and-release requirements.  The Arkansas Game and Fish Commission (AGFC) currently prohibits the use of natural or scented baits in areas with special trout regulations solely because of the higher post-release mortality associated with bait fishing compared to that observed with artificial lures and flies.  A review of the scientific literature substantiates this practice.

Hunsaker and Marnell (1970) compared hooking mortality for cutthroat trout in Yellowstone Lake caught on single hook lures, single barbless hook lures, single treble hook lures, and single barbless treble hook lures, single hook baited with a worm.  In summary, hooking mortality for all lures combined was 4%.  Hooking mortality for bait-caught trout was 48%, overall.  However, for bait caught trout, they evaluated hooking mortality for trout that swallowed the hook separately from trout that did not swallow the hook, which resulted in drastically different results.  Hooking mortality was 8% for trout that did not swallow the hook, but was 73% for trout that did swallow the hook.  Overall, 55% of the trout caught on bait, swallowed the hook.  Taylor and White (1992) conducted a statistical analysis of results from 18 trout hooking mortality studies and generated an overall summary of those studies.  They found that hooking mortality overall was 4% for artificial single and treble hook lures combined, compared to 31% hooking mortality associated with bait-caught trout.  Pauley and Thomas (1993) studied cutthroat trout hooking mortality comparing single hook lures, single treble hook lures, and bait (worms).  They found a much higher mortality rate for artificial lures than any other study at 20% for single hook lures and treble hook lures combined.  However, bait-caught trout hooking mortality (49%) was more than double that of artificial lures.  Schill (1996) measured hooking mortality for rainbow trout caught on worms in both a hatchery and a trout stream.  He found the lowest overall hooking mortality (16%) associated with bait fishing for trout, of the studies reviewed herein.  Like Hunsaker and Marnell (1970), Schill found very low mortality associated with trout that were not deep-hooked at only 2% in the hatchery study.  However, 63% of the trout studied were deep hooked.  Of those deep hooked, mortality was 74% for trout released after the hook was removed and 47% for trout released by cutting the line.  This represents a 36% reduction in hooking mortality simply by cutting the line. 

These studies indicate that the high post-release mortality associated with bait is directly related to the higher incidence of deep-hooking with bait.  Because bait is fished passively (“slack line”), the fish has a greater chance of being hooked in the gut or other vital organ.  In contrast, both artificial lures and flies, which are fished actively, have a higher incidence of hooking fish in the jaw or other non-lethal location resulting in a much lower post-release mortality.

Although there are those that would contend that only artificial lures with single hooks should be allowed in special regulation areas, the scientific literature does not support this assertion.  Klein (1965) caught trout from a rearing pond with a daredevil type lure equipped with either a single hook or a single treble hook, and then released the trout into a raceway to monitor post-release hooking mortality.  Overall, he found low hooking mortality with both hook types, but actually measured lower hooking mortality with treble hook lures (3%) than with single hook lures (6%).  Klein stated that the single hook was often taken farther into the mouth than the treble hook and therefore, inflicted a more serious injury than the treble hook, which usually hooked in the edge of the mouth.  Marnell and Hunsaker (1970) measured 5% hooking mortality for cutthroat trout caught on treble hook lures.  Hunsaker and Marnell (1970) studied hooking mortality for cutthroat trout in Yellowstone Lake with barbed flies, barbless flies, barbed treble hook lures, barbless treble hook lures, and a trolled single hook and worm.  They found low hooking mortality for all four artificial lure types with 4 % for single hook lures and 4% for treble hook lures.  Dotson (1982) only documented one trout mortality out of a sample of 315 trout while comparing hooking mortality differences between single and treble hook lures.  Schill et al. (1986) documented 3% hooking mortality in Yellowstone River managed under catch-and-release regulations with artificial lures and flies.  Snuffer and Alexander (1992) compared hooking mortality for wild brook trout caught with five different lure types including Mepps spinners and Cleo spoons rigged with either a single hook or a treble hook, and Rapala lures with two treble hooks.  They found 2% hooking mortality when lures were equipped with a single hook and 8% hooking mortality when lures were equipped with a single treble hook.  They found no mortality associated with Rapala lures with two treble hooks.  Taylor and White (1992) found that hooking mortality overall was 4% for single hook lures and 5% for single treble hook lures.  Pauley and Thomas (1993) compared hooking mortality of sea-run cutthroat trout associated with spinners equipped with either a single hook or a single treble hook and found much higher mortality rates than any other study at 16% for single hook lures and 24% for single treble hook lures.  These higher rates were attributed to the fact that sea-run cutthroat are larger and more aggressive than stream dwelling cutthroat and therefore took lures deeper than trout in other studies.  Schisler and Bergersen (1996) measured 4% hooking mortality for rainbow trout caught on artificial flies.  Schill and Scarpella (1997) found an overall 5% hooking mortality associated with artificial lures and flies by summarizing results from other salmonid studies.

The requirement of artificial lures with barbless hooks in areas under special regulations is also not clearly supported by the fisheries literature.  Hunsaker and Marnell (1970) compared hooking mortality for cutthroat trout in Yellowstone Lake caught on single hook lures, single barbless hook lures, single treble hook lures, and single barbless treble hook lures.  They found no significant difference in hooking mortality for single hook lures (4%) and single barbless hook lures (3%).  For treble hook lures, they found higher mortality with barbless treble hooks (6%) compared to barbed treble hooks (3%), but again the difference was not statistically significant.  Dotson (1982) found no mortality with either barbed or barbless single hooks.  Schill and Scarpella (1997) summarized the results from past salmonid hooking mortality studies.  For flies and artificial lures combined across studies, average hooking mortality was 4.5% for barbed hooks and 4.2% for barbless hooks.  They stated that “a 0.3% mean difference in hooking mortality from the two hook types is irrelevant at the population level, even when fish are subjected to repeated capture”.  Therefore, they deemed the restriction of barbed hooks, a “social issue”.

Based on the current knowledge of hooking mortality associated with terminal tackle, the prohibition of natural or scented baits in special trout management areas in Arkansas will likely continue.  The use of circle hooks for bait fishing has demonstrated the potential of reducing post-release mortality to less than 10% hooking mortality.  However, there remains much research to be done on this subject before bait fishing with circle hooks would be allowed in special management areas. 

The scientific literature indicates that artificial lures of any type will likely yield less than 10% hooking mortality.  However, the type of artificial lures allowed in special regulation areas throughout Arkansas has been inconsistently applied.  Some areas allow barbless, treble-hooked lures while others require lures with single, barbless hooks.  This inconsistency in what types of lures are allowed can be very confusing to anglers.  And although the requirement of lures with single, barbless hooks is likely the most conservative approach, it may unnecessarily exclude anglers that prefer to use treble-hooked lures.  Barbless lures do not significantly reduce hooking mortality, but probably reduce some damage to fish and therefore have a value in trout management.  In the future, the AGFC Trout Management Program will endeavor to make the types of artificial lures allowed in special regulation areas consistent throughout the state.

I’ll follow up with some comments on the proposals in June.

© 2009, Scott Branyan

About Scott Branyan

Scott Branyan, a native Arkansan, is a full-time fly-fishing guide.
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