U.S. Department of Agriculture Animal and Plant Health Inspection Service Wildlife Services

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Technical Papers OF THE BUREAU OF SPORT FISHERIES AND WILDLIFE

30. Estimates of Some Vital Statistics of Northern Pike, Walleye, and Sauger Populations in Lake Sharpe,

By Joseph H. Elrod and Thomas J. Hassler

UNITED STATES DEPARTMENT OF THE INTERIOR, WALTER J. HICKEL, SECRETARY Leslie L. Glasgow, Assistant Secretary for Fish and WiZdZife, Parks, and Marine Resources Fish and Wildlife Service, Charles H. Meacham, Corrmissioner Bureau of Sport Fisheries and Wildlife, John S. Gottschalk, Director Washington, D.C. · October 1969 CONTENTS

Abstract .• 3

Lake Sharpe 3

Collection and treatment of data 3

Results 5

Northern pike 5

Relative abundance 5

Age composition. 5

Sex ratios 5

Growth. 5

Survival 5

Walleye .. 7

Relative abundance 7

Age composition 7

Sex ratios 10

Growth. 10

Survival 10

Sauger ... 11

Relative abundance 11

Age composition 12

Sex ratios 13

Growth 13

Survival 13

Summary and conclusions 14

References 17

2 ESTIMATES OF SOME VITAL STATISTICS OF NORTHERN PIKE, WALLEYE, AND SAUGER POPULATIONS IN LAKE SHARPE, SOUTH DAKOTA

By Joseph H. Elrod and Thomas J. Hassler Bureau of Sport Fisheries and Wildlife North Central Reservoir Investigations, Pierre, South Dakota

AB.5TRACT. --Catch-effort data derived from gill net samples were used to estimate relative abundance, age composition, sex ratio, growth rate, survival rate, and relative year -class strength of northern pike , walleye, and sauger populations in Lake Sharpe, , S. D., during the first 3 years of impoundment (1964-66). Catches were generally highest in tailwaters. Females were more numerous and larger at most ages than males. A large 1964 year class of northern pike and walleye dominated catches of these species through 1966. Survival rate of the 1964 year class of northern pike declined with age. Survival of pre-1964 year classes of walleye and sauger was higher from 1965 to 1966 than from 1964 to 1965. Relative abundance of northern pike declined during the period considered.

Research on Lake Sharpe (Big Bend LAKE SHARPE Reservoir), on the Missouri River in South Dakota, includes studies of the effects of im - on the Missouri River was poundment and water-level management on the closed in December 1963, and Lake Sharpe filled fish populations. This report contains an anal­ ear1 y in 1964 . Marked diurnal and weekly flue - ysis of gill net samples and a description of tuations in water level occurred until December some biological characteristics of the three 1965, when pool level was stabilized at 433 meters principal game fish populations in this r eser - (1,421 feet) above mean sea level with an annual voir -- northerri pike (Esox lucius), walleye mean variation of less than 0.5 meter (1.64 feet). (Stizostedion vitreum) , and sauger (Stizostedion The lake is approximately 130 kilometers (81 canadense). Its primary purpose is to provide miles) long, has a surface area of 22, 600 estimates of relative abundance, age composi­ hectares (55 ,845 acres), a maximum depth of tion, sex ratio, growth rate , survival rate, 24 meters (78 feet) and a volume of 23 .4 x lo8 and r elative year-class strength during the cubic meters (1, 900, 000 acre-feet) (fig. 1). Dis - first 3 years of impoundment ( 1964 to 1966) so charge from Oahe Reservoir is the principal that changes within populations may be docu - water source with some runoff entering from mented. the Bad River and smaller intermittent tributaries .

The South Dakota Department of Game, COLLECTION AND TREATMENT OF DATA Fish, and Parks provided assistance in gill netting in the summer of 1965. The U.S. Fish populations were sampled with a Bureau of Commercial Fisheries made available 350-foot ( 107. 7 meter) gill net composed of seven some fish specimens in the fall of 1966. 50- by 6-foot (15 .2- by 1.8-meter) panels of the following consecutive mesh sizes: 3/4, 1, 1-1/4,

3 4 Technical Paper 30: Bureau of Sport Fisheries and Wildltfe

1-1/2, 2, 2-1/2, and 3-1/2 inches bar measure age indicators was established for northern pike (1.9, 2.54, 3.18, 3.81, 5.08, 6.35, and 8.89 from Oahe Reservoir by Hassler (1969), and centimeters). A standard unit of effort was there is no reason to doubt the applicability of one net fished on the bottom overnight. the scale method to this species in Lake Sharpe. Duration of sets ranged from 17 to 24 hours, Confidence in age determinations from scales with a mean of 18. 7 hours in Oahe tailwaters, of walleye and sauger was based on (1) the and 19 . 8 hours at other locations . independent recognition of a newly recruited dominant year class ( 1964) from time -series Fishing was conducted weekly from length-frequency distributions, ( 2) the October 1964 to June 1965 and biweekly there­ appearance of an annulus each year only during after through January 1967 at a fixed location the spring and early summer months, (3) the in Oahe tailwaters. From June through consistency of independent scale readings, September, 1965 and 1966, fishing was also and ( 4) the occurrence on the scales of all fish conducted biweekly at six approximately equi­ estirµated to be older than the 1964 year class distant downstream locations (fig. 1). Addi­ of successive narrow growth zones followed by tional fish were obtained from trap nets and an unusually wide growth zone beginning in incidental gill net catches. 1964--the first year following impoundment.

Each fish was measured (fork length in millimeters) and sexed. A scale sample Estimates of relative abundance (an index was taken from every fish in 1964 and from of population abundance in which variations in the randomly selected individuals from 1965 to availability of fish to the fishing gear are 1967. Ages were determined from scales, and assumed to be random;(see Beverton and Holt, fish taken on or after January 1 were credited 1957, and Gulland, 1965), age composition, with a new annulus. Validity of scale rings as growth and survival rates, and relative year-

---

Fig.ure 1 :--Lake Sharpe, South Dakota (sampling locations indicated by circles). Elrod and Hassler: Vital Statistics of Fish. Populations in Lake Sharpe 5

class strength were based on catch per standard Sex ratios unit of effort. Calculations and definitions follow Ricker ( 1958). Data were arbitrarily Females of the 1964 year class were grouped into three time periods that afforded twice as abundant as males during the first 3 maximum utilization of specimens, that is, years of life (table 3). In other year classes (1) March-May, (2) June-September, and (3) males were more numerous at ages II to IV in October-January. !/ Growth and mortality 1964; at ages Ill and IV in 1965; and at age I in rates are assumed to be consistent within each 1966 . The numbers of northern pike in most of time period and therefore comparable between the older age groups were small; hence, sex years. Moreover, annual growth would be ratios may be biased. Disregarding age, females expected to be completed by October and not were more than twice as numerous as males in resume appreciably before the end of May. All 1965 and 1960. available specimens were used for computing sex ratios. Growth

RESULTS Mean length of females was greater than than of males at all ages (table 4). Mean length NORTHERN PIKE of age I northern pike of both sexes was less in 1966 than in 1965, although the length range was Relative abundance greate r in 1965. Age II females had a greater mean length in 1966 than in 1964 . The numbers The highest catch per unit of effort was of fish in older age groups were too small for in Oahe tailwaters during the third period in comparisons to be meaningful. 1964 (table 1). Catches at that station subse­ quently declined and reached their lowest levels Annual instantaneous growth rates of fish in 1966. In 1965 and 1966, catches during the of the 1964 year class, calculated from the data second period were lower than those during the in table 4, were as follows: first and third periods . A decline from 1965 to 1966 was also evident at six of seven sampling Males Females locations during the second period. Catch per Age 0 to I 0.293 0.457 unit of effort during the second period was Age I to II -0.053 0.113 highest near West Bend in both years. Growth rate of both sexes was considerably Age composition greater during the first than during the second year of life, with females growing nearly twice Catches included fish of ages 0 ( 1964 as fast as the males. The negative value for males only) through VI (table 2). In every year the reflected a shorter mean length at age II in 1966 mean age reflected the dominant 1964 year (only seven fish were taken) than at age I in 1965. class; no other year class appeared in apprec i­ able numbers . The 1965 year class accounted Survival for about 8 percent of the catch in 1966, and there was no evidence of the 1966 year class . Annual survival rates of the 1964 year Relative year -class strength, estimated from class were calculated from the first-, second-, catch of age I fish per unit of effort at all and third-period catches in Oahe tailwaters and locations during the second period, indicated from second-period catches at the remaining the 1964 year class to be 18 times as abundant locations (table 5). ·survival was approximately as the 1965 year class . a third higher from age 0 to I than from age I to II, and estimates based on the tailwater catches !/ Length data from sauger were grouped into were consistent. The higher survival rates at a March-July period each year. the downstream locations during the second period 6 Technical Paper 30: Bureau of Sport Fisheries and Wildlife

Table 1:--Catch of northern pike per gill net set at seven locations in ,Lake Sharpe, 1 South Dakota. ty time period, 1964-66 ~umber of net sets in parenthesis7.

Location Collection Oahe Farm Medicine Chapelle Joe West Big Bend period tailwaters Island Creek Creek Creek Bend Dam All 1964

3. Oct.-Jan. 25.1(17)

1965

l. Mar. -May 18.7(ll) 2. June-Sept. 8.2( 9) 0.4(7) 5.1(7) 6.7(7) 10. 7(7) 12.3(7) 7.2(6) 7.6(50) 3. Oct. -Jan. 13.1( 8)

1966

1. Mar.-May 6.2(12) 2. June-Sept. 2.4 (18) 2.9(9) 4.3(9) 4.6(9) 7.0(8) 8.3(9) 2.8(9) 4.3(71) 3. Oct.-Jan. 2.7( 9)

Table 2:--Percentage age composition and Table 3:--Sex ratio (Females/Males), at each mean age of northern pike in gill age, of northern pike caught by all net catches in Lake Sharpe , South gears in Lake Sharpe , South Dakota, Da~ota, 1964-66 LNumbers of fish 1964-66 lNumber of fish in parenthesii17 in parenthesi]?.

Collection year Collection year Age 1964 1965 1966 Age 1964 1965 1966

0 85.2 (277) 0 2.1 (280) ( 0) ( 0) I 0.6 ( 2) 97.5 (732) 8.4 ( 36) I 1.0 ( 2) 2.1 (789) 0.8 ( 50) II 7.7 25) 0.1 ( 1) 88.5 (379) II 0.5 ( 30) l/ ( 1) 2.3 (418) III 3.4 ( 11) 0.9 7) 1. 2 ( 5) III 0.4 11) 0.1 ( ll) 1. 3 ( 7) IV 2.2 ( 7) 0.8 ( 6) 0.2 1) IV 0.8 ( 7) 0.2 ( 7) y ( 3) v 0.9 ( 3) 0.1 ( 1) 1. 2 ( 5) v 2.0 ( 3) 2.0 ( 3) 5.0 ( 6) VI 0.5 ( 4) 0.5 ( 2) VI 0) 1.0 ( 4) y ( 2)

Mean 0.4 (325) 1.1 (7 51) 1.9 (428) All 1. 7 (333) 2.0 (815) 2.1 (486) age

]) Females only could result from downstream emigration from the tailwaters • The lower catch per unit of effort in the tailwaters during the second There was little difference between the survi - period, coupled with a marked increase in val rates of males and of females, although mean lengths (up to 15 centimeters) at that of females tended to be higher. successive downstream stations during this period, lends support to this interpretation. Elrod and Hassler: Vital Statistics of Fish Populations in Lake Sharpe 7

Table 4:--Mean and range of fork lengths, by age and sex, of northern pike ca•1ght by all gears at the Oahe tailwa~ers station in Lake Shar pe, South Dakota, Oct.-Jan. 1964-66 /NUmber of fish in ' parenthesi~/.

Collection :z:ear 1964 1965 1966 Length Length Length (mi lli- (milli- (mi lli- Age Sex meters) Range meters) Range meters) Range

0 t 405 318- 472 (118) ( O) ( O) ~ 424 282- 524 (253) ( O) ( 0)

I O' 564 1) 544 317-680 (31) 471 418-595 (12) ~ 656 1) 671 412-774 (83) 545 503-604 ( 7)

II i! 617 521- 688 23) ( O) 516 452-612 ( 7) ~ 680 594- 778 11) ( 0) 752 540-945 (46)

III t 670 618- 762 12) 0) 663 620-706 2) ~ 846 813- 870 4) 0) 830 1)

IV o' 723 677- 792 5) ( 0) 0) ~ 877 859- 909 3) ( 0) 881 831-930 ( 2)

v t 754 1) ( 0) 0) ~ 994 984-1004 2) 984 972-996 ( 2) 0)

VI 0 O) 842 815-870 2) ( O) ~ 0) ( 0) ( 0)

WALLEYE Age composition

Relative abundance Catches contained individuals of ages 0 through VIII in every year except 1965 (table 7). Catch per unit of effort in Oahe tail - In 1964 walleyes of age 0(1964 year class) and waters was greater during the third period age IV (1960 year class) were about equally (Oct. -Jan.) than during other periods in every represented and dominated the catches, although year (table 6). There was little difference be­ fish of age III (1961 year class) and age V (1959 tween first- and second-period catches. Second­ year class) were also well represented. In period catches, however, were higher in the 1965 and 1966 the 1964 year class at ages I and tailwaters than at any other location, although II, respectively, continued to dominated the catches at the extremes of the reservoir proper catches, with the strength of the 1960 year class (Farm Island and Big Bend Dam) were lower still evident; age 0 fish (1965 year class) were than those at midreservoir locations in both absent. One age IX walleye (1957 year class) 1965 and 1966. Catch per unit of effort at was caught in 1966. Mean population age dropped most locations increased from 1965 to 1966. from 2 . 9 years in 1964 to 2 .4 years in 1965 and 8 Technical Paper 30: Bureau of Sport Fisheries and Wildlife

Ta?le 5:--Survival rates (s) of the 1964 year class of northern pike, by sex, estimated from catch per gill net (c/f) in Lake Sharpe, South Dakota, 1964-66.

c/f c/f c/f 1964 s 1965 s 1966 Oahe tailwaters March-May t 6.00 0.362 2. 17 ~ 12.18 0.281 3.42

June-Sept. t 1.89 0.116 0.22 ~ 6.11 0.236 1.44

Oct.-Jan. 0 6.94 0.522 3.62 0.122 0.44 ~ 14.70 0.620 9.12 0.158 1.44

Lake Sharpe June-Sept . t 2.49 0.659 1.64 ~ 4.95 0.628 3.11

Table 6:--Catch of walleye per gill net set at seven locations in .Lake Sharpe, South Dakota, by time period, 1964-66 L]fumber of net sets in parenthesii_?.

Location Collection Oahe Farm Medicine Chapelle Joe West Big Bend period tai !waters Island Creek Creek Creek Bend Dam All

1964 3. Oct.-Jan. 24.6(17)

1965 1. Mar.-May 6.2 ( 11) 2. June-Sept. 7.7( 9) o. 2(7) 1.6(7) 4.1(7) 2.4(7) 2.9(7) 0.5(6) 3.1(5Cl) 3. Oct.-Jan. 13.2( 8)

1966 1 • Mar.-May 6.2(12) 2. June-Sept. 6.6(18) 1.7(9) 4.7(9) 2.4(9) 4.1(8) 5.4(9) 2.3(9) 4.2(71) 3. Oct.-Jan. 36.1( 9) Elrod and Hassler: Vital Statistics of Fish Populations in Lake Sharpe 9

Table 7:--Percentage age composition and mean age of walleye in gill ne t catches in Lake Sharpe, South Dakota, 1964-66 LF\imber of fish in parenthesi~7.

Collection ;tear A~e 1964 1965 1966

0 26.1 93) ( 0) 0.2 1) I 4.8 17) 58.3 (199) 9.7 58) II .., .o ( 25) 5.0 ( 17) 75. 7 (453) III 13.8 ( 49) 4.1 14) 1.8 ( ll) IV 21.6 ( 77) 7.3 25) 2. 0 ( 12) v 16.3 ( 58) 12.3 42) 2.7 16) VI 6.7 ( 24) 10.0 34) 4.5 27) VII 2.5 ( 9) 1.8 6) 2.5 15) VIII 1.1 4) 1. 2 4) 0.7 4) IX 0) 0) 0 . 2 1)

Mean age 2. 9 (356) 2.4 (341) 2. 4 (598)

Table 8 :--Sex ratio (Female/Ma le), at ea::h age, of walleye caught by al l gear s in Lake Sha.:- pe, So~th Dakota, 1964-66 L}'fl.1rnber o f fish in pa:enthesi.§/'.

Collection ;tear A~e 1964 1965 1966

0 1. 5 ( 89) 0) 0) I 3. 3 ( 17) 1.6 (201) 2.5 56) II 1.3 25) 0.7 ( 17) 1. 2 (455) III 0 . 9 49) 4.0 ( 15) 2. 3 ( ll) IV 0.5 82) 1.1 ( 25) 1.3 14) v LS ( 58) 0.6 42) 0.7 17) VI 1.6 ( 24) 2.1 34) 0.3 28) VII 2.0 9) y 6) (). 9 15) VIII y 4) 1.0 4) y 3) IX 0) 0) }j 1)

All 1. 2 (357) 1.4 (344) 1. 2 (600)

y Females only

1966. Passage of the relatively large 1960 year curves as two peaks that shifted to the right in class through the fishery and e ntrance of the successive years (fig. 2). large 1964 year class are evident in the catch 10 Technical Paper 30: Bureau of Sport Fisheries and Wildlife

Sex ratios

1964 Females were more numerous than males in 18 of the 26 age-group comparisons (table 8). Sex ratios within year classes varied between age groups and showed no consistent pattern, 0 although sex ratios in the 1960 and 1961 year classes accounted for five of the seven ratios in which males dominated. Sex ratios among the older age groups (VII-IX) may be biased because of the paucity of specimens.

Growth i

0 Mean length of walleye males was greater la.. 1965 ..... N=l4 than that of females at age II and at age I in 0 1964 . Beginning at age III, mean length of Q females was greater than that of males g in all years (table 9). Mean lengths of males and females in most age groups were less in 1965 and 1966 than in 1964 . Absence of fish i in older age groups (VII-VIII) in 1965 and 1966 precluded comparisons between years . 1966 N•32 0 Instantaneous growth rate of fish of the 1964 year class was higher from age I to II than from 0 to I for both sexes as shown below:

Males Females 0-1 0.292 0.278 I-II i 0.392 0.293 Males grew at a faster rate than females 0 II m DZ 'll lZI: from age 0 to I and from age I to II. In the AGE 1960 year class-, females grew faster than ma I es from age IV to V , and from V to VI at the following estimated rates: FiJure 2:--Catch curves of walleye taken by gill net at Oahe tailwd.ters station, Lake Males Females Sharpe. So~th Dakota, 02t.-Jan.1964-66 C/F = catch per gill net set. Age IV to V 0.039 0.076 Age V to VI 0.020 0.086 Relative year -class strength was esti­ mated from the rriean catch of age I fish per Survival unit of effort at all locations during the second period. Since walleye were not completely Annual survival rates (calculated from vulnerable to capture by our gear at age I, it third-period catches in Oahe tailwaters) were was assumed that the fraction of a year class variable beyond age III and generally higher from which was vulnerable to the gill net at age I was 1965 to 1966 than from 1964 to 1965 (table 10); constant from year to year. The 1964 year however, three of the seven estimates from 1964 class was three times more abundant than the to 1965 were 0 .4 or greater. 1965 year class. CORRECTION for

ESTIMATES OF SOME VITAL STATISTICS OF NORTHERN PIKE, WALLEYE, AND SAUGER POPULATIONS IN LAKE SHARPE, SOUTH DAKOTA

TechnicaJ Paper 30 of the Bureau of Sport Fisheries and WiJdJife U. S. Department of the Interior October 1969

On page 10 of this paper the graph in figure 2 is wrong (the graph of figure 3 was inadvertently used). On the back of this sheet, page 10 is reproduced with the cor­ rect figure 2. Please insert this sheet at the proper place in your copy of Technical Paper 30. r 10 Technical Paper 30: Bureau of Sport Fisheries and Wildlife

Sex ratios

Females were more numerous than males in 18 of the 26 age-group comparisons (table 8). Sex ratios within year classes varied between age groups and showed no consistent pattern, although sex ratios in the 1960 and 1961 year classes accounted for five of the seven ratios in which males dominated. Sex ratios among the older age groups (VII-IX) may be biased because of the paucity of specimens.

Growth

Mean length of walleye males was greater than that of females at age II and at age I in 1 ~64 . Beginriing at age III, mean length of females was greater than that of males in all years (table 9). Mean lengths of males and females in most age groups were less in 1965 and 1966 than in 1964. Absence of fish in older age groups (VII-VIII) in 1965 and 1966 precluded comparisons between years .

Instantaneous growth rate of fish of the 1964 year class was higher from age I to II than from 0 to I for both sexes as shown below:

Males Females 0-1 0.292 0.278 1-11 0.392 0.293

Males grew at a faster rate than females from age 0 to I and from age I to II. In the 1960 year class, females grew faster than .males from age IV to V, and from V to VI at the following estimated rates: Fi'.gure 2: - -Catch curves of walleye taken by gill net at Oahe tailwaters station, Lake Males Sharpe, South Dakota, Oct.-Jan.1964-66. Females C/F = catch per gill net set. Age IV to V 0.039 0.076 Age V to VI 0.020 0.086 Relative year -class strength was esti­ mated from the mean catch of age I fish per Survival unit of effort at all locations during the second period. Since walleye were not completely Annual survival rates (calculated from vulnerable to capture by our gear at age I, it third-period catches in Oahe tailwaters) were was assumed that the fraction of a year class variable beyond age III and generally higher from which was vulnerable to the gi'll net at age I was 1965 to 1966 than from 1964 to 1965 (table 10); constant from year to year . The 1964 year however, three of the seven estimates from 1964 class was three times more abundant than the to 1965 were 0 .4 or greater. 1965 year class. Elrod and Hassler: Vital Statistics of Fish Populations in Lake Sharpe 11 ge a rs Tahle 9:--Mean and ra~ 3e of fork length3, by a ge and se~, of W • ' !e ~ ~ ca1ght by all in Lake Shai:pe, So'.!th Dako ta, Oct.-Jan .. 1964-56 ffembe r 0 ~ fi<;h in parenth ~ 3iy.

Collection l'.ea r 1964 1965 1966 Length Leng th Leng th (milli- (milli- (milli- A8e Sex meters) Ran8e meters) Ran8e me t ers) Ran !:2 e

0 0 188 165-237 (41) 0) 0) ~ 194 145-242 ( 62) 0) 200 1)

I 0 341 295-367 ( 3) 251 225-313 (12) 232 215-248 6) ~ 319 288-363 (13) 256 214 - 308 (26) 241 209-295 (19)

II 0 386 320-415 (12) 394 365-428 4) 37 2 280-440 (219) ~ 381 330 -47 2 (16) 0) 347 275-481 ( l~)

III 6 437 325 -559 (28) 437 1) (0 ) ~ 484 357 -615 (26) 478 1) ( 0)

IV c 465 357-587 (64) 469 433-536 5) 46 2 450-482 4) ~ 541 369-678 (31) 547 517 - 577 3) 603 1)

v 6 495 431-616 (31) 483 39 5-520 (l 5) 47 0 454-492 6) ~ 581 514-638 (46) 582 553-651 ( 6) 545 435 -612 4)

VI 0 511 47 5-555 ( 9) 517 510-535 2) 491 461- 525 (10) ~ 626 557-702 ( 15) 621 610-612 2) 63'l 620-661 5)

VII & 582 508- 5 7 5 4) 0) ':>l 2 47 ) - 571 8 ) ~ 663 631-679 6) 628 60'.i-65 2 2) 646 l)

()) VIII 6 0) 590 1) ~ 652 594-699 4) 649 615-68 2 2) 671 6)6-694 l)

Catch of the 1964 year class per unit of strengths precluded calculution of survival rates effort increased from 1964 to 1966 in Oahe directly from the cutch curves. tailwaters (table IO), and at age II, walleyes of this year class accounted for 76 percent of SAUGER increased availability at most reservoir stations in 1966 (table 6). Recruitment of this Relative abundunce year class to the gill net from age I to II was greater than total mortality, thus precluding Catch per unit of effort wus generally calculation of a survival rate . The variability higher in Oahe tailwaters in 1964 and 196S than in recruitment between years may be seen in during comparable periods of 1966; however, the average catch curves plotted in figure 2. there was no significant change in catches from Lack of approximately equa l year-class 1965 to 1966 at downstream locations (table 11). 12 Technical Paper :30: Bureau of Sport Fisheries and Wilalife ,

Tab:~ 10:--Su::-v i val rates (s) of walleye estim.1ted i:roai catch per gill net set (c/f) 03.'le ta i_ h1:1ter station in Loike Sharp.~. S. D., 1964-66,

c/[ c/f c/f 1964 s 1965 s 1966

0 6.06 0.11

1.00 5.88 2.78 0.630 [I 1.65 0.61 26.22 0 . 151 [ [ [ ·1. 18 0.25 0.352 1.760 [I' 5.59 1.12 0.44 0 . 795 4.53 2.62 0.89 0.110 0.637 \I I 1. .'.i7 O. SQ 1.67 O. Y+O 2.000 \I I l 0.59 1.00 0.644 0.66Q \I I I I 0.24 0.38

Tabl e 11 :--Catch of s aug2 r per gi. 11 n·:>t set at seven locations in La'ta, by tim2 pedod, 1954-66 ffernber of fish in pa 7enth2si_D.

Loe a Lion Co 11 t-C ti on Onh <: Farm MLdicin<: ChapLllL JOL West Bi g Bend pLriod Lili lwilLLrs ls Lind C rL·t:>k CrL' Ek CreLk BLnd Dilm All

196.'.i

,' ) • Oc L ~ -J ci n.

I . ~· ·1 ;1 r. - Mil v 11.9(11)

2 • j U '1 L - S l''1 l • ').ti( 9) 0.6(7) 1 .6(7) l.4(7) 0.6(7) 0.1(7) 0.2(6) 2.0(SO)

.3 • Oc: L • - J < l n .. 2. 2 ( 8)

1%6

! • 1't1r. · ·~1 c1 y 2. l(l2l 2 . .JU:-1L-S c pl. 2 • .'.i( !K) l.1(9) I. 1(9) 0.8(9) 0.7(8) 0. 2 (9) 0.1(9) 1.4(71) :3 • Oc l • - .Lrn. 1. 8 ( 9)

Second-period catches were also generally Age composition higher in the tJ ilwatcrs than at the downstream locations in both 196;) and 1966. Of the down­ The 1961, 1962, and 1964 year classes stream locations, catches indicated slightly la rgcly dominated sauger catches during the greater relative abundance at midrescrvoir. .1-ycar period, ar.d their passage through the Elrod and Hass le r: Vital Statis tics of Fish Populations in Lake Sha rpe 13

fishery is evident from the s hape of the de­ The 1965 vear cla s s made a r e la tively scending limb of the catch curves in figure .3. s trong s howing a t. age I in 1966 and might be The oldest specimen taken in 1964, for expected to contribut e significant 1y in s ubseque nt example, was age VI, while in 1966 a nd 1967 yea rs. Catch of age I sauge r per unit of e ffo rt fish of age s VII and VIII w e re taken (ta ble 12). ;t rhe downs trea m locatio ns indicated that the Mean age increased from 2. 7 to .3. I yea rs 1965 vea r class was fuur times a::; abunda nt as during this period. Although age 0 fi s h were the IQ64 war class. CHL·hes o f agl' I fish relatively scarce in the catches, the s tre ngth werL" sm~ ll; hL" nCL', thL' est imat e· o f VL'ar-cla;.;s of the 1964 year class was a lready apparent s trL·ng th ma\· b L" suhjl'ct tu consid L" rahle err o r. during the first year of life . Sex ratios

1964 Female sa ugl'r s w e r l' mure numL"rous N•l59 than males in 15 of 22 s ex-ratio comparisons (table 13). Maks of the 1962 year class uut - numbered iemales at agL"s 11 thro ugh IV and 0 accounted fo r three of the five ratios in which males werL· dominant. l\luch of thL· variation in sex r <.ll ios within and between the older YL"i.I r classes wi.ls prohi.thly the result of small numhL·rs offish.

Growth

Compi.trison of di.I i i.I colkclL'd during thL· .... 0 1965 period :\'larch-July shmvL·d thi.lt in 196.'i m ea n IL"ngth ..... N=14 (.) of females wi.ls grei.lter than tha t of ma ks a t a II ages hl'yond LJgl' I. The diffL'rL· ncL· in mL«Jll s izL· Q (!) a t agl' I was not sti.ltistic;illv signifiL;,1nt (t ;,1hll" 14). g In 196() mean IL"ngth of mall· saugL·rs ;,1t ;,1gL· II was greLJter than th

were largL"r tlwn male,; ;,1t ;i II o th L· r <1gL·,..; ..\gL · II fish of hoth Sl'X L',..; \\'L· re smalkr in JlJ()() 1h;111 fish 1966 oft hL' same age in J lJ(1"i. Too k\\' indh· idu;1 )s 0 N•32 were collected to c;,1kulatl' gro\\'lh ratL·,.; .

Surviv<1 I

,\nnual ,..;ur \'i\·al r

Table 12:--Percen~age age compositio~ and mean age of saug~r in gill net catches in Lake Sharpe, South Dak0:::a, 19 64-66 DJ•rnber of fish in pa.:-e ilthesis7.

Collection ye

0 4.8 6) 0) 0.7 1) I 8.0 10) 25 .7 ( 53) 14.7 22 ) II 36.0 45) 7.8 ( 16) 39.4 59) III 34.4 43) 2 5. 7 53) 8 .0 12) IV 6.4 8) 26.2 54) 11.] 17) v 8 .0 10) 7. 8 16) 13.] 20 ) VI 2.4 3) 6. 3 (1 )) 8 .7 13) VII 0) o. j ( 1) 2.7 4) VIII O) ( 0) 1.] 2)

Mean age 2. 7 (12 5) 2.9 (206) J. 1 (1 SO) -----·

a ll gear s in La•~e Tab~e 13:--Sex: i:atio (F e: males/Males), a t each age, of saugz r- caught by pa r eathe sii_7. Sharp:?., Sou·~h Dak.)ta, 1964-65 ,1i•Jm':)e r- of f i 'ih in

Col le<.: Lion l'.L i.lr A c 1964 196 5 1966

0 2. 0 6) ( 0 ) () ) 2.1 10) l. 2 ( 5·3) 1. 2 22) II 0 . 6 4 5) 0.8 16) 1.6 65) ITI 1. 'l 41) (). ') 56) 1. 4 12) IV 1 . 5 9) (). 7 58) (). 7 17>

\I 9 . 0 10) 2.0 21) 1. () ( 22> VI 2 .o ]) 14.0 I)) l . ·3 ( 13) VII 0) l/ 2) ·1.0 ( .'.,) VII I 0) ()) l.O 2)

All 1. 2 (126) 1.0 (22 1) 1.4 ( l .J 7)

1/ Females on l y

age I; hence, a survival rate could not he calcu­ SUMMARY AND CONCLUSIONS lated. Calculation of survival rates from the catch curves was invalid owing to the unequal This study demonst rat es that changes year class sizes (fig. 3). have occurred within the northern pike , walleye, a nd sauger populations following impoundment of Lake Sharpe. The large 1964 vcar class of Elrod and Hassler: Vital Statistics of Fish Populations in Lake Sharpe 15

Table 14:--MP-an and ra~ge of fork lengths, by age and sex, of sa~ger caught by all gears in La'

1965 1966 Length Length (milli­ (mi 11 i­ Age Sex meters) Range meters) Range

183 169-195 7) ( O) 186 145-207 9) ( 0)

II 120 286-343 ( 7) 249 201-304 (15) 336 302-359 ( 5) 233 202-325 (23)

Ill 360 304-407 (30) 353 l) 370 261-425 (14) 344 270-405 5)

IV 386 328-482 (26) 375 362- 390 ( 6) 434 403-471 (16) 451 450-452 ( 2) v 393 328-449 ( 4) 396 373-426 ( 8) 483 417-555 7) 440 392-495 ( 6)

VI 485 1) 398 376-420 ( 2) 534 463-632 6) 536 484-593 ( 8)

VII 0) 595 1) 501 1) 533 517-542 3)

VIII ( O) 543 ( 1) ( O) _(_Ql

Table 15:--S;.i::-vival rates (s) of sa•J;Ser estimated from catch per gill net set (c/O at the Oa'i.e tailwater3 station in Lake Sha-:-pe, S. D . . 1964-65,

c/f c/f c/f 1964 s 1965 s 1966

0 0. ·35 O.ll

0.11 0.38 1. 22 0.183 II '3. 12 0.11 1.00 0.16'.) 0.846 II I 3.18 0.50 0.11 O. ll9 1.120 IV 0.76 0.56 0.328 0.868 v 0.94 0.25 0.33 0.138 0.880 VI 0.24 0.13 0.22 16 Technical Paper 30: Bureau of Sport Fisheries and Wildlife

northern pike and walleye dominated catch sam - than that of males through age II. Male w ~ lleye ples of both species during the first 3 years of grew faster than females through age II , but impoundment. Sauger reproduced in 1964 and thereafter females grew faster and to larger 1965, but contributions of these year classes sizes. Female sauger were larger than males in numbers of fish were small. Catches of of the same age after age II. sauger and northern pike per unit of effort de­ clined from the maximum levels in Oahe tail­ Northern pike and walleye used in growth waters during the third per·iod of 1964 -65 and comparisons were collected from October through the first period of 1965. The increased catch January when growth for the year was essentially of walleye per unit of effort in Oahe tailwaters completed. Mean length at each age, therefore, during the third period and elsewhere through­ would approach a maximum attained prior to out the reservoir in 1966 was due to the influ,x the time of annulus formation. Mean lengths of of the 1964 year class. sauger were calculated from fish collected from March through July, and except for virgin fish, Highest levels of relative abundance of in which annulus formation occurred ea rlie r all three species generally occurred in Oahe than in adults, the m eans also r eflect the maxi­ tailwaters. Excluding this location, catches of mum attained length prior to annulus formation. walleye during the June-September period were higher between Medicine Creek and West Bend Based on catches in Oahc tailwaters , than elsewhere; sauger were slightly more survival of the 1964 year class of northern pike abundant in the Medicine Creek area, while declined with increasing age . The higher abundance of northern pike increased down - apparent survival rate from age I to II at the stream to West Bend. Walleye and sauger we re downstream locations was discussed earlier. common in the tailwaters throughout the year. Catch of the 1965 year class per unit of e ffort Northern pike, on the other hand, occurred in was only one-eighteenth that of the 1964 year greatest numbers in the tailwaters from class, and ther e was no evidence of survival of October through May. the 1966 year class. Relatively low s urvival r a tes accompanied by two successively poor Mean population age of northe rn pike year classes (1965 and 1966) indicate a decline and walleye was largely influenced by the in the relative abundance of this species during relatively abundant 1964 year class. Mean the period considered. ages of northern pike and sauger increased during the period of the study, while that of Surviva l of pre impoundme nt year classes walleye declined slightly . Mean ages of the (1956-63) of both walleye and saugcr was lower three species increased and decreased in - from 1964 to 1965 than from 1965 to 1966. versely with their abundance in catches. Survival estimates of over LOO percent probably r e sulted from the small numbers of fish in catch Female northern pike were slightly samples , but they suggest good survival from more nume rous than males at most ages. 1965 to 1966. Survival rates could not be calcu ­ Dominance of female northern pike and walleye lated for the 1964 year class of either walleye at age 0 in 1964 suggests either differential or sauger because fish of age II we re probably survival during the first summer of life, or not completely recruited to the gill net. Catch an unbalanced sex ratio at fertilization. The curves of neithe r s pee ies could be used for cal - sex ratio of the 1964 year class of both species culation of survival rates because of unequal remained remarkably constant during successive year -class strength . year of life (tables 3 and 8). The absolute number of fish recruited to Females of the three species attained a each species population from a given year class larger size than males. Growth rate of female would be difficult and impractical to determine. northern pike of the 1964 year class was greater Relative year-class strength based on standardized Elrod and Hassle r: Vita l Sta tistics of Fish Populatio ns in Lake Sharpe 17 catches of age I fish at s e ve n r e s e rvo ir locations Gulland,J. A. during the summer, howeve r, prov ide s an in­ 1965. Manual of m e thods for fish stock formative and comparative m easure of r elative assessment. Part I. Fish population recruitment to each of the s e important game analysis. FAO Fisheries Technical fish populations. Pape r No. 40, Revision I.

Estimates of the biological charac - Hassler, T. J. teristics of the three spe cie s populations are 1969 . Biology of the northern pike in Oahe believed to be unbiased and afford a practica l Re s e rvoir, 1959 through 1965. U.S. means of following postimpoundment changes Bureau of Sport Fisheries and Wildlife, within such populations. Continuing studie s T echnical Paper 29. seek to docume nt changes within the s e populations and to verify, by m eans of tagging expe rime nts, Ricke r, W. E. estimate s derived from e mpirica l data and 1958. Handbook of computations for also to explain ca use and e ffe ct r elations con - biological statistics of fish populations. ce rning these change s. Fishe ries Research Board of Canada, Bulletin 119, 300 p. REFERENCES

Beverton, R. ] . H., and S. ] . Holt. 1957. On the dynamics of exploited fish populations. Fishe rie s Investigations, London (2) 19: 533 p.

·:i U. S. GUVE HN:\IL1' T i ' IH N Tl ~(; O FFIC I< : l'Hi' ' () - :H oi-7 7' • As the Nation's principal conservation agency, the Depan­ ment of the Interior has basic responsibilities for water, fish, wildlife, mineral, land, park, and recreational re­ sources. Indian and Territorial affairs are other major concerns of America's "Department of Natural Resources." The Department works to assure the wisest choice in managing all our resources so each will make its full contribution to a better United States -- now and in the future.

UNITED STATES DEPARTMENT OF THE INTE R I OR F I SH AND W I LDLIFE SERVICE BUREA U OF SPORT FISHERIES AND WILDLIFE W A S H INGTON . D . C . 2 0 240

P OSTAGE AND FEES PAI D U . S. DEPARTMENT OF THE INTERIOR