Hooking Mortality

By Jordan Weeks

Discussions among my musky fishing friends often revolve around muskellunge biology. How long do they live? How old is a 50-inch fish or what is the mortality rate for caught-and-released muskellunge? The answers to these questions are never easy and vary greatly from lake to lake and by region of the country. However, the last question, regarding hooking mortality is by far the most difficult to answer. This is because it is especially hard to find information pertaining to muskellunge hooking mortality in peer-reviewed scientific literature. Furthermore, it is very difficult to follow angler-caught fish after they are released.  One way to accomplish this task would be to fit angler-caught fish with radio tags and follow them for a period of time after capture (for more information on this type of research see Project Noble Beast-http://projectnoblebeast.blogspot.com/). Unfortunately, implanting a radio tag can cause additional mortality and may not give us the “real” answer. However, since this technique is as good as we can get, the results from these studies can give us a valuable look into the world of angler-caught muskellunge.

If you ask most diehard musky anglers, they will tell you that 100 percent of the fish they catch are released successfully and swim away. Very few people will admit that they had a musky die on them, perhaps because they fear the repercussions from their peers or perhaps they really believe that all the fish they catch and release survive.  The fact is, if you catch enough muskies you will kill some in the process. Just how many is a piece of information that all musky anglers need to appreciate. Am I suggesting that we stop fishing muskies? Absolutely not. However, I think an appreciation for our impacts on the fish population is a good thing. This article will attempt to provide some information that will let us better understand our impacts on the resource.

As a fisheries scientist I often use findings from research on similar species to help learn about another species of interest. In this case I will outline a paper about northern pike to help us learn about “Size selectivity, injury, handling time, and determinants of initial hooking mortality in recreational angling.”  Researchers captured 415 northern pike from two lakes. Objectives of the study were to: 1.) assess the effect of lure type and size and bait type and size on the size of pike captured by rod and reel as well as the distribution of legal (20-inch minimum size limit) and sub-legal fish in the catch; 2.) measure the effect of lure or bait type and size on hooking location, injury (amount of bleeding), and handling time (time of hook removal); and 3.) determine the factors associated with initial hooking mortality (within one hour of catch).

Answers to these questions are of particular interest to fisheries scientists attempting to manage muskellunge as much controversy exists over the effectiveness of harvest regulations (size limits) in recreational fisheries (Paukert et al. 2001; Radomski et al. 2001). The argument arises, in part, because some fish will die after release as a result of angling methods, and those that don’t die after release will, most likely experience a suite of sub-lethal disturbances and injuries that may affect longterm growth and fitness (Cooke et al. 2002; Alringhaus et al. 2007a). Of course these are the worst case scenarios. In fact, some fish may experience no ill effects as a result of capture.  In situations where the fisheries goal is natural reproduction, protecting the female muskellunge past maturity in order to allow for replacement is very important. Replacement is when an egg successfully hatches, grows to maturity and that fish, now an adult, spawns, creating another generation of fish. If, during the course of angling activities, we kill most of the female fish, no regulation will be effective. In addition, because male muskellunge rarely exceed 40 inches the focus of most fishing effort is geared toward larger-growing female fish, possibly increasing capture rate and angling mortality.

But does angling really have a profound affect on our muskellunge populations? Researchers used gear intended to reflect common tactics used by anglers which included various line and rod types, multiple lure sizes, livebait (quick-strike rig with two treble hooks), and barbed single and treble hooks. Once a pike was captured, the fish was landed as quickly as possible using a knotless landing net, rubber net or by hand. After unhooking, the fish was placed into a large cooler with recirculating lake water and observed for one hour. If the fish was deeply-hooked no attempt was made to dislodge the hooks, rather the hook was cut using a boltcutter and remained in the fish. Although fish captured undoubtedly experienced additional stress from delayed release in a cooler, no other options were available for researchers.

Researchers found:
“ 80.5 percent of fish captured on livebait were of legal size.
“ Bait type was not related to the size of fish captured.
“ Bait size was related to fish size (large lures caught large fish).
“ Natural bait was more likely to be deeply ingested (15.4 percent of the fish captured on livebait were hooked in the gullet).
“ Bait type and size were related to hooking location (75 percent were hooked in non-critical areas, such as the upper and lower jaws).
“ Small lures were more likely to hook the fish in the gills and less likely to hook the fish in the upper jaw whereas medium and large lures were less likely to hook the gills
“ Deeply-hooked fish bled more than those hooked in non-critical locations
“ Initial mortality (within one hour) was unrelated to bait type, size, fish size, fishing method, or hooking location, The only significant variable was presence of bleeding.

Of the 415 fish captured by researchers only 10 experienced initial mortality (2.4 percent, +/- 1.5 percent). Of course there is no measure of delayed mortality in this study so this should be assumed to be a minimum number (perhaps Project Noble Beast will help us obtain this information).

Many variables went into this study, however I feel it is a reasonable example of average initial mortality for angler-caught fish. Of course, some of you are better at releasing fish than others and other variables could decrease this number. The first and most obvious to me is the impact of air exposure (unhooking, measuring and picture-taking). While many anglers are adamant about water release these researchers found that northern pike are resilient to air exposure for up to four minutes, which is plenty of time to unhook, measure, and snap a nice picture should you choose to do so. So, while water release certainly reduces the chance that a fish is dropped on the bottom of the boat or injured some other way, it does not necessarily reduce initial mortality (for the record, I measure, using a bump board and photograph every muskellunge I catch).

So, while it appears that esocids (pike and muskies) are rather robust to injury associated to capture, most of us will, by the process of angling, kill some fish. However, knowing that larger baits not only catch larger fish but are less likely to hook a fish deeply, livebait is more likely to hook fish deeply, and knowing when to cut hooks on a lure rather than attempt removal, we can better choose techniques to reduce mortality on the fish we love. In addition, proper release tools, a good landing device and a plan can also help. Good fishing!

Arlinghaus, et al. 2008. Size selectivity, injury, handling time, and determinants of initial hooking mortality in recreational angling for northern pike: the influence of type and size of bait. North American Journal of Fisheries Management 28: 123-134.

Paukert et al. 2001. An overview of northern pike regulations in North America. Fisheries 26(6):6-13.

Radomski et al. 2001. Visions for recreational fishing regulations. Fisheries 26(5):7-18.

Cooke et al. 2002. Strategies for quantifying sub-lethal effects of marine catch-and-release angling; insights from novel freshwater applications. Pages 121-134 in J. A. Lucy and A. L. Studholme editors. Catch and release in marine recreational fisheries. American Fisheries Society Symposium 30, Bethesda Maryland.

Arlinghaus et al. 2007a. Understanding the complexity of catch-and-release in recreational fishing: an integrative synthesis of global knowledge from historical, ethical, social, and biological perspectives. Reviews in Fisheries Science. 15:75-167.

Jim Saric

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