Hello, I have been reading posts on this board for several years. The subject of WSR, CNR, hooking mortality, fishing opportunity allocation, and the science supporting fisheries management choices is critical to continuing angling opportunity in the Northwest. With this in mind (and seeing that long posts are acceptable) I am posting excerpts from a letter I wrote for the recent WSR moratorium hearings. My opinion is that the stress effects on reproductive fitness of hooking and releasing maturing fish should be considered in management decisions. Note that this is my opinion. As I am often reminded by my fishing partner of the past 35 years sport fishermen, unlike fisheries scientists, don't have to let the facts interfere with their opinions. I hope the following will be a positive addition to the discussion.
Mandatory wild steelhead release is an effective management tool to protect depressed wild steelhead populations caught in a fishery targeting hatchery steelhead. It does not insure restoration of depressed or threatened populations but it is a necessary first step. My concern is not about the wild steelhead retention moratorium. If wild populations are judged to be depressed to a point where it is necessary then it should be implemented. My concern is about targeted catch and release fisheries on these same wild populations
Catch and release fisheries is a management tool for managing people, to create opportunity for people to fish, and to maintain a stable population of fish. There are many examples of successful catch and release fisheries. The cutthroat trout fishery in Yellowstone National Park is often cited as one of the most successful. The potential problem with steelhead catch and release fisheries is that the fishery targets maturing fish unlike catch and release fisheries in rivers for resident trout that take place post spawning. The 5% to 10% mortality associated with release is well known. What is not well known is the stress-related effect of catch and release fisheries on reproductive fitness.
The effect of stress on reproduction is a recognized and studied phenomenon. It is a driving force of evolution and an important component to the understanding of ecological interactions. There are many studies that have looked at the effect of stress on the growth and reproduction of fishes. In a July 24, 2000 news release the Washington Department of Fish and Wildlife outlined plans to study the effects of catch and release stress on the reproduction of sturgeon in the lower Columbia River. The aquaculture industry has a strong interest in understanding the effects of stress on salmonid reproduction. The effect of stress on fish in hatcheries has been recognized for some time (***erlund et al. 1981).
When a fish (or any animal) is subjected to physical stress a two-part response occurs. One is a catecholamine release (adrenaline rush) and second is the cortisol response. The adrenaline has the immediate effect of increasing activity, the fight or flight response. The cortisol response has a much slower response time and is similar to the maturation process (Powell 2002). It is the cortisol response that effects the reproductive process.
Elevated cortisal levels are particularly important because they can effect the progeny of stressed fish. In the early development stages of fertilized eggs the steroids in the eggs come from maternal sources (Hwang et al. 1992). High levels of cortisal in eggs from stressed fish decreased from fertilization to hatching. At some point in development maternal hormones are replaced with hormones synthesized in the egg. The maternally produced steroids can effect the embryonic development (Schreck et al. 1991), even to the point of altering the sexualization of the gonad.
In an investigation of stress at various times during the maturation of female rainbow trout (Contreras-Sanchez, et-al. 1998) reports that repeated stress significantly affects reproductive traits. Mild acute stress administered early in the maturation process, 3 months to 1.5 months before final maturation did not effect the time of ovulation with respect to a control group. Fish that were subjected to stress over the entire period and also the last 1.5 months ovulated on an average 2 weeks earlier than the control group. Relative fecundity was significantly different and egg size and swim-up fry were smaller in fish subjected to stress early in the maturation process. Observations of the progeny of the stressed fish indicated they performed as well as the progeny of the control fish with respect to juvenile growth and disease resistance. In this study eggs from stressed females were fertilized with sperm from unstressed males.
In a study (Campbell et al. 1991) eggs and sperm from both stressed females and males was used. They observed a delay in ovulation, reduced egg size and lower sperm counts. The egg survival was 63.4% from the stressed fish and 84.8% from the control group.
The focus of the research discussed above was to evaluate the effect of stress on reproductive fitness. The fish were exposed to long term low-level stress or repeated short-term acute stress. The stress-induced inhibition of reproduction can have consequences for both wild and domestic populations. Short time acute stress from exposure to fishing gear may interfere with reproduction (Pankhurst et al. 1997). They express a concern that the impact of fishing on natural populations may be greater than just mortality. Catch and release fisheries should be evaluated for effects on reproductive success. A study looking at steroid levels in rainbow trout captured by angling (Pankhurst et al. 1994) found high cortisol levels increasing for a few hours after capture then recovering to resting values after 24 hours. They state that this may not affect reproduction at an advanced stage of maturity but could be important at earlier stages.
Chronically stressed fish have prolonged cortisol elevations (Pickering 1993). There many factors that can expose wild fish populations to stress, warm water, low level pollution, and natural environmental stresses. The acute stress of catch and release angling in addition to these other stresses could have a severe impact on the reproductive success of wild steelhead and salmon populations. A recent study (Meka 2002) of catch and release angling of Alagnak River rainbow trout in Alaska indicated some of the possible problems. The focus of the study was hooking injury and mortality but blood samples were taken from the fish before release. The time for capture and handling and the water temperature were recorded. The results of the blood chemistry indicated that the cortisal level increased significantly relative to the duration of the angling process, the water temperature, and the size of the fish. The time to land and release a fish was related to the size. In all cases there was a significant increase in cortisol levels. The increase was greater at higher temperatures. This study divided the anglers in to two groups, experienced anglers and novice anglers. Novice anglers injured more fish (70%) than experienced anglers (56%) did. Experienced anglers took significantly longer to land their fish than did novice anglers. One could surmise from this that even though the hooking mortality is probably lower with experienced anglers, the time that they spend to land the fish could lead to greater cortisol levels and potential loss of reproductive capability.
LITERATURE CITED
Campbell, P. M., T. G. Pottinger, and J. P. Sumpter. 1991. Effects of acute stress on time of ovulation, fecundity, egg size, egg survival, and sperm counts in rainbow trout. Biol Reprod. 47:269.
Contreras-Sanchez, W.M., C.B. Schreck, M.S. Fitzpatrick, and C.B. Pereira. 1998. Effects of stress on the reproductive performance of rainbow trout (Oncorhynchus mykiss). Biol Reprod. 58(2):439-447.
***erlund, U. H. M., J. R. McBride, and E. T. Stone. 1981. Stress related effects of hatchery rearing density on coho salmon. Transactions of the American Fisheries Society 110:644-649.
Hwang, P. P., S. M. Wu, J. H. Lin, and L. S. Wu. 1992. Cortisol content of eggs and larvae of teleosts. General and Comparative Endocrinology 86:189-196.
Meka, J. 2002. Evaluating the effects of catch-and-release on hooking injury and immediate physiological response of Alagnak River rainbow trout captured by catch-and-release angling. Report at
http://www.absc.usgs.gov/research/Fisheries/Alagnak/catch_and_release.htm Powell, J. 2002. Broodstock Health: Stress Effects. Salmon Health Report in Northern Aquaculture. Mar:2002
Schreck, C. B., M. S. Fitzpatrick, G. W. Feist, and C. G. Yeoh. 1991. Steroids: developmental continuum between mother and offspring. Pages 256-258 in A. P. Scott, J. P. Sumpter, D. E. Kinne, and M. S. Rolfe. Reproductive physiology of fish. Proceedings Fourth International Symposium on Reproductive Physiology of Fish, University of East Anglia, Norwich, UK (7-12 July 1991).
Pankhurst, N. W., and G. Van Der Kraak. 1997. Effects of stress on reproduction and growth of fish. In G. Iwana, A. D. Pickering, J. P. Sumpter, and C. B. Schreck, editors. Fish stress and health in aquaculture.
School of Experimental Biology Series. Volume 62. Cambridge University Press, London, UK.
Pankhurst, N. W., and M.Dedual. 1994. Effects of capture and recoverey on plasma levels of cortisol, lactate and gonadal steroids in a natural population of rainbow trout. J. Fish Biol. 45:1013-1025.
Pickering, A. D. 1993. Growth and stress in fish production. Aquaculture 111:51-63.