¢§|3d|3€ ICHIGAN STATE UNIVERSITY LIBRARIE Wm“ mlmmmwm Ill 11m Hlllllllll 9 Michigan State 3 1293 00574 9258 University This is to certify that the thesis entitled Age and Growth of Saginaw Bay Walleye with Observations on Trap Net Mortality and Population Size presented by David Jon Borgeson has been accepted towards fulfillment of the requirements for Master of Science degree in Fisheries and Wildlife Major professor Date February L 1990 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE MSU Is An Affirmative Action/Equal Opportunity lndltutlon AGE AND GROWTH OF SAGINAW BAY WALLEYE WITH OBSERVATIONS ON TRAP NET MORTALITY AND POPULATION SIZE BY David Jon Borgeson A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 1990 tososfix ABSTRACT AGE AND GROWTH OF SAGINAW BAY WALLEYE WITH OBSERVATIONS ON TRAP NET MORTALITY AND POPULATION SIZE by David Jon Borgeson In Michigan in the early 1980's a walleye (Stizostedion vitreum vitreum) population was being established in Saginaw Bay. In order to better manage this new fishery, information on walleye growth, survival, year-class strengths, population size, and the incidental mortality caused by commercial trap netting was needed. In 1984 and 1985 walleye caught in the commercial trap nets set off Bay Port were scale sampled, weighed, measured and checked for tags. The number of walleye observed dead in nets was also noted. Walleye in Saginaw Bay exhibited excellent growth, 182 mm at age 1, 331 mm at age 2, 407 mm at age 3, 474 mm at age 4 and 523 mm at age 5. Differences in first year growth apparently reflect whether walleye were planted as spring or fall fingerlings. It appears year-class strength is strongly influenced by fingerling plants. The trap net fishery is not causing excessive mortality to the walleye population, with only 3.33 percent of the walleye observed dead in the nets. Survival was estimated to be 0.67. The walleye population in 1984 was estimated to be 1.20 million, and the 1985 population between 2.19 and 4.15 million walleye. ACKNOWLEDGEMENTS Bay Port Fish Company supported this study by hiring me to work on their boats and in their fish house during the summers of 1984 and 1985 and by helping me handle walleye during their lifting operations. I thank Forest, Todd, and Connie Williams and Denny Root for this opportunity, their support, and their friendship. I thank Dr. Niles Kevern for his direction and patience, and Drs. William Taylor and Patrick Muzzall for their support and guidance. I would also like to thank the Michigan Agricultural Experiment Station for financial support. iii TABLE OF CONTENTS Page LIST OF TABLES. O O O O O O O O O O O O O O O O O O O O C v LIST OF FIGURES O O O O O O O O O O O O O O O O O O O O 0 Vi INTRODUCTION. 0 O O O O O O O O O O O O O O O O O O O O O 1 Description of Study Area. . . . . . . . . . . . . . 2 METHODS O O O O 0 O O I O O O 0 O O O O O O O O O O O O O 7 RESULTS 0 O O O O O O O O O O O O O O O O O O O O O O O O 9 Age, Growth and Year-Class Strengths of Walleye. . . 9 Population Estimates from Tag Recaptures . . . . . . 15 Trap Net Mortalities . . . . . . . . . . . . . . . . 18 DISCUSSION. 0 O O O O O O O O O O O O O O O O O O O O O O 20 Age, Growth and Year-Class Strengths of Walleye. . . 20 Population Estimates from Tag Recaptures . . . . . . 22 Trap Net Mortalities . . . . . . . . . . . . . . . . 23 CONCLUSION. O O O O O O O O O O O O O O O O O O O O O O O 24 LITERATURE CITED. 0 O O O O O O O O O O O O O O O O O O O 25 iv Table LIST OF TABLES Size (mm) at age of Saginaw Bay Walleye compared to state averages and Western Lake Erie stock. . . Mean lengths (mm) of Saginaw Bay walleye at different sampling times in 1984 and 1985. . . . . Mean total length-at-age of walleye year classes from Saginaw Bay . . . . . . . . . . . . . . . . . Percentage of fingerlings planted in Saginaw Bay as spring and fall fingerlings, 1981 - 1985. . . . Total number of walleye and tagged walleye observed in trap nets in Saginaw Bay in 1985 and 1985 O O O O O I O O O O O O I O O O O O O O O C 0 Estimates of walleye population susceptible to trap net fiShery O O O O O O 0 O O O O O O O O O 0 Observed walleye mortalities in trap nets in Saginaw Bay in 1984 and 1985 . . . . . . . . . . . Saginaw Bay Walleye trap net catch per lift by year class compared to Lake Erie and annual fingerling stocking rates. . . . . . . . . . . . . Page 10 11 12 14 16 17 19 21 LIST OF FIGURES Figures 1 Saginaw Bay region with study area stippled. 2 Historical commercial harvest of walleye in Saginaw Bay 0 O O O O O O O O O O O O O 0 vi INTRODUCT ION Until 1945 walleye (Stizostedion vitreum vitreum) were an important component of Michigan's Saginaw Bay commercial fishery, with a high of 930 metric tons harvested in 1942. By 1950 their numbers had dropped to insignificance and stocks remained at near zero until the late 1970's (Schneider and Leach 1979). The decline has been attributed to the intensive commercial fishery for walleye and to the fouling of the spawning substrate by organic material and toxins (Schneider 1977). In the 1960's fisheries workers in Wisconsin and Michigan developed inexpensive and effective means of rearing large numbers of walleye to fingerling size in outlying rearing ponds. Because of great interest in walleye, especially among anglers, and the past performance of walleye in Saginaw Bay, attempts to re-establish significant numbers in the Bay began in the early 1970's using the new rearing pond technology. The pond-reared fingerlings made an immediate and dramatic impact on walleye survival and enthusiasm for the program caused it to grow rapidly. By 1979 releases of over 250,000 two to three inch walleye fingerlings from five ponds were annually stocked into the bay. The sport catch grew, from an estimated catch of 6,700 from June 1983 to May 1984 to an estimated 73,000 walleye in 1986 (Keller et 1 2 a1. 1987). Walleye were beginning to appear in large and, according to commercial fishermen on the bay, even nuisance numbers in commercial trap nets set for other species (perch, catfish). Concern was expressed that incidental catch and handling by commercial trap netters might significantly increase walleye mortality and limit population ’growth. Biologists also wondered about the growth rate and survival of walleye as numbers kept increasing and about the upper limits to expansion of the stocks. Michigan fisheries workers began tagging walleyes on their spawning migration in 1981 to begin to get information on their movement, exploitation rate and survival rate. The object of this study of walleye age, growth and trap net mortality with observations on population size is to increase the knowledge and understanding of these factors in order to improve our ability to manage walleye stocks in Saginaw Bay. Description of Study Area The study area is in the Bay Port area of Saginaw Bay. Bay Port is a commercial fishing settlement once supporting hundreds of commercial fishermen and their families. It remains as the bay's most active commercial fishing center, but on a much reduced scale. Since 1980 the entire bay averaged 567,000 pounds of catfish, with 850,000 pounds of carp and 68,000 pounds of perch harvested in 1986 (Keller et a1. 1987). Bay Port is located in Wildfowl Bay just inside 3 Sand Point, the narrow peninsula that separates the inner from outer Saginaw Bay on its southeast shore. The bay itself is one of the major bays on the Great Lakes, historically second in the commercial production of walleye in the Great Lakes (Hile 1954). It is shallow and productive. The inner bay averages 15 feet in depth and the outer bay 46 feet (Figure 1). Totalling 1,143 square miles in area, Saginaw Bay represents 5 percent of Lake Huron's surface (Keller et a1. 1987). Rich, flat agricultural lands surround the bay. The bay is fed by one large river system, the Saginaw River, and a dozen or so smaller ones including the Rifle, Au Gres, Pine, Kawkawlin, Quanicassee, Sebewaing, Pigeon, and Pinnebog rivers. Pollution of the Saginaw River has caused problems in the bay both from nutrient enrichment and agricultural and industrial waste (Schneider 1977). This problem is to a large degree abated through water quality reform, but some problems persist, especially chemical contaminants in larger carp and catfish possibly caused by lingering contaminants in the sediments. Walleyes stocked from rearing ponds are, for the most part, released in tributaries and the walleye home to these streams, especially the Saginaw and its major tributary, the Tittabawassee, to spawn (Keller et a1. 1987). These spawners, tagged in large numbers below Dow Dam on the Tittabawassee River, formed the basis for making population estimates from trapnet-caught fish examined at Bay Port. The historical commercial fishery production in Saginaw 4 Bay shown by walleye catch in Figure 2 (Keller et a1. 1987) is legendary and it is an important source of local pride in fishing villages like Bay Port. The growing sport fishery for yellow perch has resulted in conflicts with the commercial fishery. The walleye resurgence has been fully claimed by sportfishermen. No commercial harvest is allowed nor is any likely to be. Au Sable Pl \ \ '\ 7} lbwnsPt \~ ' ‘6): \\ 0 J‘ , OUTER BAY \ mace \ \ \ ‘-\ 5 x5- OCharily 15, :3” - Pi-AU Gres \ Ausnn :ogomnq c, \ \ z: , Sand#i, _ ' INNER BAY Q 4 5% Z a . 9:233:92; 0y Port . QT::§V‘.?('-' /Noyonaumg 6° . 9 .\ Pl. 062’ .;. ‘ \ 9 Fish Pl. 5' Sebewalng ,/ / I’ll say A. J“. W" - Quanicassee ‘3 3 \ o O l 8’. , a? N J‘ 0 0 / / So in «TIC/é 9 0W 6" '~ ’3. Miles 04% 9 l0 2f: 3: ’v¢ . . . . E \\ 0 M 20 30 ‘” Kilometers Figure l. Saginaw Bay region with study area stippled (Keller et a1 1987). cam— Plll’h amm— b .lll IL .Ahmma Hm um umHwav mom socflmmm cm w>mHHm3 mo umm>umn HmfloquEoo Hmowu0umfl: .N ousmwm Lcm> at: SE 82 oz: 2:: 82 22 82 82 W; - l.l!(lk-o-fwol-lwl. lrllulab p p p p p p P p p C "H .K/ H /r /. ,« nu U ->\/\< << /\ l\oz mmm mem mme Hmm emme .oH “mnsm>oz mmm emm mOm mme mae emm mmmH .m umnonoo mmm mmm Hem o~e mmm emme .m umnouoo mmm mmm mme mme mmm mmme .e uwnsmummm Hem mme mme mmm mmm emmH .m “mnemummm mmm mem Hem mam eme mHe mmm mmme .m umsmse emm Hmm mmm mee eee ace NOm emmH .mm mesa mmm mmm HOm mme ooe mmmm .H mean 0mm mmm eme mme mmm emmm .~ mean mmm mmm emm mme mme Hmm mmmm .HH mm: mmm mmm mmm mee mmm emme .mH wage HH> H> > >H HHH HH H 0 ”6mm "mama .mmmH can emmH am wwawa mememfimm ucmuwwmfio um wxwaemz hem socmmmm mo AEEV mnumcmq com: .N wanna 12 me mmm hmm mmm vhv 50v Hmm NmH cow: hma NmH vmma whv nmm moN mama mow How mam mwa Nmma mam vhv mmv mmm mwa Hmma om mam mww mmm Ham mma Omaa mm 5mm mmm Hmv mmv mmm hma mhma Hm 00m mom hmm vhv maw Hmm aha mhma ha me mmm hmm mmw mew «hm ham mma hhma sz HHH> HH> H> > >H HHH HH H mmmHU Ham» .mmm Socwmmm Eoum mmmmmHo Maw» mamHHms mo wmoluMInumcmH Hmuou cow: .m manme 13 plantings were divided into spring and fall plantings, and in 1981 walleye were planted as fall fingerlings averaging 58.5 mm (Table 4). The 1983 year class exhibited greater first year growth than the other year classes (Table 3). The 1985 year class began to appear in the nets in November with a mean length of 229 mm, but the 1984 year class was not observed in the nets in the fall of that year. Annulus formation occurred in May. The walleye condition factor, observed weight over expected weight (Bagenal 1978), varied somewhat during the year, generally rising from 0.987 in May to 1.006 in October. The length- weight relationship is described by the equation W=6.2373 x -6 3.0721 10 L 14 Table 4. Percentage of fingerlings planted in Saginaw Bay as spring and fall fingerlings, 1981—1985. /1 Fingerlings % Spring % Fall Year Planted Fingerlings Fingerlings 1981 294,656 0% 100% 1982 269,540 40% 60% 1983 892,547 99% 1% 1984 1,098,737 70% 30% 1985 834,231 100% 0% /1 From State of Michigan fish stocking reports 1981-1985. 15 Population Estimates from Tag Recaptures Recaptures of adult walleye tagged on their spawning run in the Saginaw and Tittabawassee River system (Table 5) provided a basis for estimating the population of walleye fully recruited to the Saginaw Bay trap nets. The Peterson population estimates (Bagenal 1978) using 1984 recaptures of walleye tagged in 1984 was 1.20 million walleye. Use of walleye tagged in 1983 and recaptured in 1984, and an estimated survival rate of 0.67, similar to the 0.62 estimated by Keller et a1 (1987), provided an estimate of 1.21 million walleye in Saginaw Bay (Table 6). Estimates for 1985 were higher. Using 1985 recaptures of walleye tagged the same spring, the resulting population estimate was 2.19 million walleye. Walleye tagged in 1984 but recaptured in 1985 provided an estimate of 4.15 million (assuming the same annual survival rate of 0.67). The population estimate resulting from the use of 1983 tags recaptured in 1985 (0.67 annual survival rate assumed) was 2.38 million walleye. Combining these estimates by year provides a population estimate of 1.2 million walleye for 1984 and at least 2.2 million in 1985. Walleye trap net catch per unit of effort (net lifts) increased from 42.1 to 54.3 (30 percent) from 1984 to 1985, reflecting the increased fingerling plants of 1983 and 1984. 16 Table 5. Total number of walleye and tagged walleye observed in trap nets in Saginaw Bay in 1984 and 1985. Total Year Number Number Recaptures Tagged Tagged Caught 1984 1985 1981 441 0 0 l 1982 727 0 l 0 1983 3566 0 4 5 1984 4152 2021 7 5 1985 4106 7471 O 14 Table 6. Estimates of Net Fishery. 17 Walleye Population Recruited to Trap Method Estimate of Population in 1984 Using 1984 Recaptures Using 1983 Tagged Fish Caught in 1984 1.20 Million 1.21 Million Method Estimate of Population in 1985 Using 1985 Recaptures Using 1984 Tagged Fish Caught in 1985 Using 1983 Tagged Fish Caught in 1985 2.19 Million 4.15 Million 2.38 Million * All estimates assume a 0.67 rate of survival. 18 Trap Net Mortalities Walleye mortalities in the trap nets do not appear to be excessive, with an average mortality rate of 3.33 percent of the total number of fish caught (Table 7). The deaths were evenly split between walleye gilled in the heart (the larger meshed portion of the net preceding the lifting pot) of the net and those floating free in the pot. Five walleye were observed gilled and dead in the leads when nets were being pulled from the bay. Gilling of walleye was observed only in the hearts and leads. The mortality rates varied seasonally with higher values occurring during the summer months (June through August) and in November. The highest mortality observed in one net was 30% of the 39 fish caught in a net on July 6, 1985. The pot anchor of this net had come loose and two storms moved the net considerably between lifts. Lower mortality rates occurred in May, September and October, with no dead walleye observed in October of 1984. The live walleye in the net appeared to be in excellent condition and remained so after being handled and returned to the water. There is no reason to believe any delayed mortality was occurring. l9 Awmm.mv mam Awmm.av OmH Awmn.av mma ~m¢.m “mummy cuom mamuoe Awmm.mv mom Awmm.av mNH Awnm.av mNH H>¢.n «Hanum>o Awho.mv 0m Awmo.~v 0H Awmo.vv Om «aw umnEm>oz Awoo.~v «H .mwm.Hv m Ammb.ov m ohm Hmnouoo AwOH.~V Om Ame.Hv HH Awmm.ov m Hma umnewumom “www.mv Hm Ame.Hv ma Awmm.av ma me.H umsmsm Aw~¢.mv am Aw¢0.¢c mm Ammm.~v mm mmm.a sass Awmm.ov mm Awmw.ov ma Awmn.av O¢ m-.~ wean Awmw.ov m Awmm.ov m Awoo.ov 0 new mm: "mmma Awmm.mv we vam.av hm Awmo.~v aw Hmo.~ ”Hamuw>o Aw~.~Hv mH Awno.¢v m Awma.mv 0H mma umnEm>oz Awoo.ov o Awoo.ov o Awoo.ov o OmH nonouoo Ammv.av HH Awwm.ov h Awwm.ov v ~¢n umnewumwm Awmm.mv ma AwOm.Hv n Awmw.av m hmm umsms¢ vah.mv ma Awfim.flc m Awm~.¢v «H Hmm sage vaa.>v h Awmo.mv m Awwo.vv w mm moon uwmma comm uom cw womb pummm unmsmo mama Hmuoe mcflumoflm a“ owflflflo nmhm .mwma 0cm vmma c“ wmm Snowmmm c“ mad: man» s“ mwwuflflmuuoa whoaamz cw>ummno .h wanna DISCUSSION Age, Growth and Year-Class Strengths of Walleye The strong 1982 year class may in part be a result of natural reproduction augmenting the relatively small fingerling plant (Table 8). Strong year classes are often a regional phenomenon born of favorable weather conditions during spawning and early life history (Busch et a1. 1975). Walleye in western Lake Erie brought off an exceptionally strong year class in 1982 and the 1983 year class failed. Another strong year class followed in 1984 (Haas et a1 1988). This was not echoed in Saginaw Bay. The 1983 year class was as strong or stronger than the 1982 or 1984 cohorts. This adds support to the idea that fingerling plants are strongly influencing year-class strengths in Saginaw Bay. The smaller size of age I walleye in Saginaw Bay as compared to Western Lake Erie also supports this idea. It appears that the longer the walleye spend in the rearing ponds, the smaller they will be at age I. Fall fingerlings were only slightly larger than spring fingerlings at time of planting. With the longer time spent in food rich Saginaw Bay, and because they were planted at a length when they would feed almost exclusively on fish (Houde 1967), the year classes dominated by spring fingerlings show faster first year growth than year classes with split plantings or those dominated by fall fingerlings. Those year classes 2% 21 .mm.o on o» nonnasoamo was am>a>u=m .cwms mm3 mumm» nuon Eoum «m hash umuwm Eoum mama cmnz .vama ca cmuasuomu maasm uoc mmMao now» mama m\ .aama .am am mama Eoum ~\ .aama .am um omauma Eoum a\ vm.o am~.¢ma mama vs.~ a.aa nan.amo.a mama Ama.o . vm.h mm.v m.a nam.~ma mama mm.o Amo.amv 0m.a Amm.vav mm.a m.na me.ma~ mama am.o Amm.~ V 0v.a Ama.m V mm.a n.m ama.¢m~ aama av.o AOa.a v om.o Ao~.~ V aa.a m.aa ama.m Gama am.o Aaa.o a Nm.o Aa¢.o a ~a.a a.aa >~¢.vm mnma mm.o Am~.o a aa.o Am~.o V mm.o m.m ooo.m~ ahma Om.o Aam.o . aa.o Aam.o v am.o n.am oho.¢ puma mama mama m\ am>a>u=m Awaum oxmav mam 3MCammm a\ chCH cwxooum mmmao amscca ~\ mono uwz moms meaaumm» mosaaumeam umwm .moumm mcaxooam meaaumeam amsccm 0cm mama wxmq ou pmummfiov mmmau Haw» an yuan Mom noumo umz mane mmwaamz ham 3MCammm .a wanna 22 consisting of spring and fall fingerlings may result in two groups of walleye with dramatically different first year growth patterns and different times of recruitment to the fishery. The age distribution in the catch suggests a healthy growing stock, but much of this may be due to the influence of the state walleye stocking program on the bay. It is impossible to say with these data at hand, but there is enough correspondence between year-class strength in the trapnet catch and annual fingerling stockings for the relationship to be largely cause and effect (Table 8). Population Estimates from Tag Recaptures No evidence of substantial out-migration of walleye was apparent from tag recaptures. If walleye were leaving the bay, one would expect the population estimates based on returns of 1983 tagged fish recaptured in 1985 to produce the highest estimate and the 1984 recapture of 1983 tagged fish to provide a bigger estimate than 1984 tagged fish recaptured the same year. But that did not happen. The 1984 tagged fish recaptured in 1985 produced the largest estimates but, except for this one, the estimates were remarkably consistent. Another estimate consistent with these may be derived from data presented by Keller et a1. (1987). In 1986, an estimate of 2.43 million walleye results when their estimates of 0.03 exploitation and a sport catch of 73,000 are used. 23 The apparent increase in the walleye population in the bay could be directly due to increases in releases of walleye fingerlings in 1983 and 1984. Fingerling plants in those two years were 892,547 and 1,098,737 respectively. This was an increase of 3.5 times the plants in 1980, 1981, and 1982 which totaled 574,094 fish (Table 3). Increased stocks also could result from increased natural reproduction in the bay or immigration of naturally produced walleye. Natural year class strength was very high for walleye in western Lake Erie in 1982 (Haas et al. 1988). The same weather conditions that favored Lake Erie reproduction in 1982 could have had the same impact on natural reproduction in the bay and its tributaries and the good weather could have helped the stocked walleye survive. Trap Net Mortalities The trap net fishery does not appear to be causing excessive mortality to the walleye population of Saginaw Bay. The commercial fishermen handle the walleye carefully and quickly return them unharmed to the water. Mortalities in the summer may in part be due to crowding of fish in nets in warm water. Frequent periods of rough weather during the year may also have contributed to the mortality in the pots. Storms and high winds delay lifting of the nets, extending the period of time the walleye remain confined. Gilling of some fish is inevitable, and it seems to be limited to the larger mesh of the hearts and leads. CONCLUSION Since the walleye year-class strengths in Saginaw Bay appear to be highly influenced by stocking, it is vital to maintain the stocking rates of fingerling walleye. Though not approaching the numbers in Lake Erie, the walleye grow rapidly in the bay, quickly entering the sport fishery and maintaining excellent growth providing a fishery for large walleye. The commercial fishery for catfish and perch continues to flourish in Saginaw Bay without harming the sport fishery for walleye. The large number of fish species and productivity of the bay should allow for non—competitive coexistence of the two fisheries. Continued stocking of spring fingerlings, while monitoring for possible natural reproduction, and continued water quality improvements are needed to ensure a sound walleye population and possibly more naturally produced fish. 24 LITERATURE CITED LITERATURE CITED Bagenal, T. 1978. Methods for assessment of fish production in fresh waters. Blackwell Scientific Publications Ltd. Busch, W.-D.N., R.L. Scholl, and W.L. Hartman, 1975. Environmental factors affecting the strength of walleye, Stizostedion vitreum vitreum, year-classes in western Lake Erie, 1960-1970. Journal of Fish. Res. Bd. of Can., 32:1733-1743. Deriso, R.B., S.J. Nepszy, and M.R. Rawson 1988. Age structured stock assessment of Lake Erie Walleye. (Report of the July 22-24, 1986, workshop). G.L. Fish. Comm. Spec. Publ. 88-3. Haas, R.C., M.L. Fabrizio, and T.N. Todd 1988. Identification, movement, growth, mortality and exploitation of walleye stocks in Lake St. Clair and the western basin of Lake Erie. Fish. Res. Rept. No. 1954. MDNR Fish. Div. Hile, R. 1954. Fluctuations in growth and year class strength of the walleye in Saginaw Bay. U.S. Fish and Wildlife Serv. Fish. Bull. 91. Houde, E.D. 1967. Food of pelagic young of the walleye, Stizostedion vitreum vitreum, in Oneida Lake, New York. Trans. of the Amer. Fish. Soc. 96:17-24. Keller, M., J.C. Schroeder, L.E. Mrozinski, R.C. Haas, and J.R. Weber 1987. History, status, and management of fishes in Saginaw Bay, Lake Huron, 1981-1986. Fish. Tech. Rept. No. 87-2. MDNR Fish. Div. Michigan Fish Stocking Records 1981-1985. MDNR Fish. Div. Schneider, J.C. 1977. History of the walleye fisheries of Saginaw Bay, Lake Huron. Fish. Res. Rept. No. 1850. MDNR Fish. Div. Schneider, J.C., and J.H. Leach 1979. Walleye stocks in the Great Lakes, 1800-1975: Fluctuations and possible causes. G.L. Fish. Comm. Tech. Rept. No. 31. 25