THE DYNAMICS OF BROWN TROUT (SALMO TRUTTA) AND SCULPIN (COTTUS SPP.) P‘OPULATIONS AS INDICATORS f 0F EUTROPHICATION ' Thesis for the Degree of \Ph. D. MICHIGAN STATE UNIVERSITY WAYNE L. SMITH .1972 LIBRA " Michigan State IJnTvenfiry This is to certify that the thesis entitled THE DYNAMICS OF BROWN TROUT (SALMO TRUTTA) AND SCULPIN (CO'I'I'US SPP.) POPULATIONS AS INDICATORS OF EU‘I'ROPHICATION presented by \ Wayne L . Smith has been accepted towards fulfillment of the requirements for __;Eh.D_.____degree in Fisheriesia Wildlife dire“, w- gem. I 9 Major professor Date JuZLv 10+. 1972 0-7639 ”as... at . ~ “0A5 N3 300K BINDERY INC. usuav muons _ 3P.IIIMT.IICIISI£ ' W 1/ I TIT mm "”0 I SNIAQ 2 III! III III I I " Br ioust compari includi Th densiti PopuIat Th densiti This re Scquin . declini' Th' margina: mean f9 Has Squ tI‘OUt “I | pOPUTatk It caDebi 11 SPEC ABSTRACT THE DYNAMICS OF BROWN TROUT (SALMO TRUTTA) AND SCULPIN (COTTUS SPP.) PORULAITDN§ AS INDICATORS 0F EUTROPHICATION By Wayne L. Smith Brown trout and sculpin populations were studied in three var- iously perturbed stream sites in northern Michigan. Intraspecific comparisons were made of several aspects of population dynamics including the intrinsic rate of natural increase (r). The upper Jordan River, nearly pristine and with high population densities, exhibited r values judged adequate for maintainance of the pepulations. The other sites were compared with this baseline. The moderately perturbed lower Jordan River had less population densities and survival but greater mean fecundities for both species. This resulted in a positive r for the trout but the birth rate of the sculpins could not compensate for the death rate and the population was declining. The Au Sable River, the most eutrophic and suspected of being marginal trout water, also had lesser population densities and greater mean fecundities than the upper Jordan. Survivorship of the sculpins was sufficient to yield a positive r. However, the low survival of the trout resulted in a strongly negative r, suggesting inability of the. papulation to sustain itself. It appeared that moderate eutrophication enhanced the reproductive capability of trout but beyond a certain level of perturbation the effects were damaging. It was suggested that fishing pressure, genetics, and species interaction could also have influenced the results. water espec Wayne L. Smith The intrinsic rate of natural increase of short-lived, cold- water fish species could be a useful tool in monitoring water quality, especially if studies were continued through several generations. THE DYNAMICS OF BROWN TROUT (SALMO TRUTTA) AND SCULPIN (COTTUS SPP.) POPULATIONS AS INDICATORS OF EUTROPHICATION By . 0") Wayne L? Smith A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Fisheries and Wildlife 1972 l ‘T I 2*)" 'F—VI—‘fiu “5'31". 5m w H. Roe‘ and to and T. I assista PFOJect Su Trainin through Resourc¢ I964. ACKNOWLEDGEMENTS I would like to extend my sincere appreciation to Dr. Eugene H. Roelofs for his advice and guidance during the course of this study, and to my committee members, Drs. Howard E. Johnson, Frank R. Peabody, and T. Wayne Porter for their review of the manuscript. I also wish to thank my colleagues on the project for their assistance in the field work, and Dr. Terry A. Haines who directed the project. Support for the research was obtained in part from F. W. P. C. A. Training Grant 5Tl-WP-109, and partly from Grant 14-31-0001-3153, through the United States Department of the Interior, Office of Water Resources Research, as authorized under the Water Resources Act of 1964. 11' INTI SELI BROI SCUI DISI LIT APP APP APP APP APP TABLE OF CONTENTS INTRODUCTION . , . . . . . . , . . . . . ....... SELECTION AND DESCRIPTION OF STUDY SITES ....... Site I ........ . ........ . . . . Site 2 . . ...... . , . . ......... Site 3 . . ....... . . ......... . BROWN TROUT POPULATIONS . . . . . . . . . . . . . , , Population Estimation .............. Sex Ratio, Sexual Maturity, Fecundity . . . . . . Survivorship and Net Reproduction Rate . . . . . Intrinsic Rate of Natural Increase ....... SCULPIN POPULATIONS ................. Papulation Estimation .............. Sex Ratio, Sexual Maturity, Fecundity ...... Survivorship and Net Reproduction Rate ..... Intrinsic Rate of Natural Increase ....... DISCUSSION . . . . . . . . . ........... , . LITERATURE CITED . , ................. APPENDIX A . . . . . . . . . ........... . . APPENDIX B . . , , . . . . . .......... . . . APPENDIX C . . . . ...... . ........... APPENDIX D ...................... APPENDIXE.......,,, .......... ,. iii TABI IO. II. I2. 13. TABLE TO. IT. 12. 13. LIST OF TABLES Estimated numbers of brown trout per hectare in the Jordan and Au Sable rivers ......... Lengths and weights of gravid brown trout collect- ed in September, l970 and 1971 ......... Sex ratios of the brown trout populations based on a composite of the I970 and l97l collections. Means and ranges ( ) for brown trout fecundity and egg diameters in the Jordan and Au Sable rivers ..................... The significance of the differences in mean fecundities and mean egg diameters for age II and age 111 brown trout ............ Estimated number of brown trout ova per hec- tare produced in 1970 and l97l as estimators of the l969 female cohort ............. Life table for female brown trout surviving to age 2.5 in T972 ................ Intrinsic rates of natural increase (r) for the brown trout populations in the three study sites Estimated numbers of sculpins per hectare in the Jordan and Au Sable rivers ......... Lengths and weights of gravid sculpins collected in March, l970 and April, l97l ......... Sex ratios of the sculpin populations based on a composite of the I970 and l97l collections . Means and ranges ( ) for sculpin fecundity and egg diameters in the Jordan and Au Sable rivers The number of sculpin ova per hectare produced in 1970 . . . .- ................ iv PAGE I] 12 l3 I4 15 17 18 20 22 24 24 25 27 LIST I TABLE I4. IS. A-A. A-C. LIST OF TABLES (continued) TABLE PAGE 14. Life table for female sculpins surviving to age 2.5 in 1972 ..................... 27 15. Intrinsic rates of natural increase (r) for the sculpin populations in the three study sites . . 28 A-A. Chemical water quality parameters investigated in 1970 in the Jordan and Au Sable rivers ...... 39 A-B. Maximum and minimum temperatures (°C) and dissolved oxygen concentrations (mg/liter) in the upper Jordan River during the sampling periods of 1970 and 1971 40 A—C. Maximum and minimum temperatures (°C) and dissolved oxygen concentrations (mg/liter) in the lower Jordan River during the sampling periods of 1970 . . . . 41 A-D. Maximum and minimum temperatures (°C) and dissolved oxygen concentrations (mg/liter) in the Au Sable River during the sampling periods of 1970 and 1971 42 ‘3 xi- IMlT-flfl Figu A-E LIST or FIGURES Figure Page 1. Map of the Jordan River showing the location of the study sites ..... . ......... 5 2. Map of the Au Sable River showing the location ' of the study site ............... 7 A-E. Age determination of sculpins .......... 43 vi to o< asso< evide ical speci few h ducti INTRODUCTION For the past few hundred years man has caused stream degradation to occur at an accelerated rate due to increased industrialization and associated urbanization. The trend toward eutrophication has been evidenced by changes in physical features, water chemistry, and biolog- ical indicators. Many studies have described the changes in faunal Species composition and growth during the course of degradation but few have considered the subtle effects on fish fecundity and repro- ductive potential. Fecundity in fish has been defined by various authors as the number or weight of viable eggs present at the peak of sexual maturity just prior to spawning. The number of eggs is variable intraspecifically and some work has been done to determine the causes of the variability. The basic factors governing fecundity are size and condition of the fish (Shapovalov and Taft, 1954; Vladykov, 1956; Scott, 1962; Bagenal, 1969). McFadden, EELQl: (1962) showed that in fertile streams receiving agri- cultural drainage and domestic effluents the average size of brown trout was larger and fecundity was consequently greater than for fish of the same age in infertile water. Wydoski and Cooper (1966) report similar findings for brook trout in infertile streams; poor nutrition and high population density were blamed for the stunted populations and the relatively small contribution of body weight to gonad development. In a study of the johnny darter, Tsai (I972) showed that fish in sew- age contaminated water grew larger and had higher fecundity than fish in cold reservoir tailwater. waste forme Mount inhib low e and B sensi crite poten (1967 Pollu Prese can r varig 2 Currently, to determine the effects of organic and inorganic wastes that are being added to our streams, acute bioassays are per- formed on adult fish, their eggs and fry. Saunders and Sprague (1967), Mount (1968), and Brungs (1969) have shown that heavy metals can inhibit spawning and reproduction even when the concentrations are low enough to have no effect on adult survival or growth. Macek (1968) and Brungs (1969) suggest that egg production is the most critical and sensitive of parameters, that it can serve as a basis for water quality criteria, and that there is a need for studying changes in reproductive potential. By analysis of the intrinsic rate of natural increase, Linton (1967) was able to predict the collapse of rock bass p0pulations in polluted sections of a warm-water stream. It is the purpose of the present study to determine if subtle changes in reproductive potential can reliably predict the decline of cold-water fish p0pulations in variously perturbed stream sites. part choic batio proje to va centr hibit tion. Sites and s- the o' enVlrI SELECTION AND DESCRIPTION OF STUDY SITES Three sites were selected on two trout streams in the northern part of the Lower Penninsula of Michigan (Figures 1 and 2). The choices were made on the basis of varying degrees of apparent pertur- bation by man. Certain chemical parameters were studied over the course of the project (Appendices A through D). In general, water temperatures tend to vary more widely in the upper Jordan but the dissolved oxygen con-I centration is the most stable and relatively high. The Au Sable ex- hibits the largest diurnal fluctuations in dissolved oxygen concentra- tion. Gislason (197l) studied the invertebrate populations at the same sites and judged the upper Jordan environment to be the most predictable and stable and the species diversity to be the highest. Diversity in the other sites was lower, indicating a more rigorous and unpredictable environment attributed to the impact of man. Site 1 The upper reaches of the Jordan River traverse a state forest that is uninhabited by man. Use of the stream is limited to occasional wading fishermen; numerous fallen logs prevent the use of watercraft. In order to preserve the nearly pristine conditions, camping is pro- hibited along the banks. The stream averages 14 m in width, the mean depth is 0.6 m, and the June, I970, discharge was 0.6 m3 per second. The stream bed consists predominantly of sand with occasional beds of 3 Figure 1. Map of the Jordan River showing the location of the study sites. Jordan River «b ._E_ P tunes... 5:. 3582.1 522. n. _ «#35 x N fl. 9—5 2 33m 590.. garb Figure 2. Map of the Au Sable River showing the location of the study site. A u Sable River H ._e _ n“? 92m I. ‘1 €2.08: — 2... 2:5 I 35. «sum .2 of m stre the comp abun (so Site the Siti SOON con Iis inc 1? in Ina 6C1 Na d1 8 of marl concretions. Where silt beds occur along the edges of the stream, Chara vulgaris is the predominant macrophyte. Numerically, the slimy sculpin (Cottus cognatus) and brown trout (Salmo trutta) comprise approximately 80% of the fish biota. Other species in lesser abundance are brook trout (Salvelinus fontinalis), rainbow trout (Salmo ggirdneri), and the brook stickleback-(Culaea inconstans). The coho salmon (Oncorhynchus kisutch) is the only transient species. 2.15.2.2 A second, more perturbed site was chosen on the lower reaches of the Jordan River approximately 22 km downstream from the first station. Situated between the sites is the Jordan River National Fish Hatchery, some agricultural land, and numerous cabins. The hatchery outfall contributes waste products from excess fish food and from fish metabo- lism. At site 2 the channel is relatively free of obstructions and increasing use is made of the stream by canoeists. The stream averages 17 m in width, 0.8 m in depth and had a discharge of 3.5 m3 per second in June, 1970. The stream bed is sand with marl concretions and the banks are lined with deciduous brush and cedar trees. The dominant aquatic macrophytes are Elodea canadensis and Potomogeton filiformis. Numerically, the mottled sculpin (Cottus bairdi) and brown trout are the dominant fish species. C, cognatus comprises approximately 7% of the total cottid population. Brook trout, rainbow trout, and the central mudminnow (Umbra lima) comprise small percentages of the resident community. Various transient species occur seasonally upon their migration from Lake Charlevoix. 5.1m. The Au Sable River study site is located approximately 7 km down- stream from the town of Grayling. This site is considered the most perturbed of the three sites, receiving effluents from municipal sewage treatment, a state fish hatchery, and possibly from the Septic systems of numerous cabins and homes along the stream. Extensive use is made of the stream by fishermen and canoeists. The stream averages 23 m in width, 0.3 m in depth, and had a discharge of 4.0 m3 per second in June, 1970. The stream bed is composed of sand and gravel with extensive silt deposits at the edges. The dominant aquatic macrophyte is Potomogeton filiformis which densely covers the bottom in some areas during its growing season. The dominant fish species, numerically, are the mottled sculpin and brown trout. Resident species in lesser abundance include the brook trout, creek chub (Semotilus atromaculatus), blacknose dace (Rhinichthys atratulus), johnny darter (Etheostoma nigrum), rainbow trout, and common shiner (Notropis cornutus). Other transient species occur during the summer months, some of which are usually considered warm-water species. BROWN TROUT POPULATIONS Population Estimation In August of 1970 and 1971 and in May, 1972, the brown trout populations by age classes were estimated by the Bailey modification of the Petersen formula. The modification provides an estimate of a small age class, known to exist, even though no recaptures occur in the census catch (Bailey, 1951). The fish were collected by electro- fishing and two mark-release periods were employed in 1970 and 1971. All shocking efforts were separated by at least 24 hours. It was later determined by a randomized block design and analysis of variance that there was no significant difference (P > 0.05) in population estimation whether there was one or two precensus marking periods. Therefore, the 1972 estimations were based on one marking period. During every collection period the total length and weight data were recorded and scale samples were removed for age determination. For comparison of age class densities it was necessary to estab- lish a standard unit of measurement. Consequently, the estimates in Table l were computed on a per-hectare basis. Collection of the age 0 fish was much more difficult in sites 2 and 3 due to higher rates of discharge and the accompanying turbulence, higher turbidity and coldr, and the presence of dense beds of aquatic plants, particularly in site 3. In addition, electrofishing has an inherent bias against the collection of smaller fish. Fortunately, age 0 fish need not enter into the computation of survivorship, net reproductive rate, and the TO ll intrinsic rate of natural increase. It is apparent from Table I that the upper Jordan River (site 1) contains a much greater density of brown trout than either of the other sites. This was also reported by Quick (1971). Table 1. Estimated numbers of brown trout per hectare in the Jordan and Au Sable rivers. Site 1 Site 2 Site 3 Age 1970 1971 1972 1970 1971 1972 1970 1971 1972 O 3050 4720 * 328 400 * 57 107 * I 740 1340 * 254 311 * 582 164 * II 480 365 270 77 126 112 226 205 50 III 75 25 5 25 9 9 7 8 32 IV 5 O 10 2 2 O 2 O O * Not estimated Sex Ratio, Sexual Maturity, Fecundity; In September of 1970 and 1971, approximately one month before the advent of spawning, collections were made to determine the population sex ratio, the percentage of mature females per age class, and the age-specific fecundity. Part of the samples for these determinations were captured outside of the study sites. The sample sizes and the physical measurements of gravid females are presented in Table 2. It can be noticed that there is very little difference in mean values between the two years for any given age class at a given site. It is also apparent that the females from site I grow more slowly, probably a reflection of the campetition occurring in a more dense population. JENNMQMMAH? .6. 13,141..“ I... 12 Table 2. Lengths and weights of gravid brown trout collected in September, 1970 and 1971. Number of Total Length (mm) Weight(g) Site Age Year Females Mean ‘Range Mean Range II 1970 7 220 206-263 114 80-168 1971 12 217 198-231 101 80-120 1 III 1970 7 255 211-279 180 100-248 1971 5 261 245-292 162 120-216 IV 1970 l 290 - 260 - 1971 l 305 - 310 - II 1970 9 262 220-288 180 110-254 1971 9 271 236-300 207 150-290 2 III 1970 5 370 319-408 486 288-642 1971 2 366 340-390 493 395-590 IV 1970 I 411 - 638 - 1971 0 - - - - II 1970 7 269 260-281 181 154-224 1971 22 263 228-310 176 110-290 3 III 1970 3 324 291-378 359 247-550 1971 I 333 - 376 - IV 1970 l 364 - 470 1971 0 - - - Quick (1971) found a significant difference (P = 0-01) in total length between site I and the others when comparing various age classes. The sex of mature fish was determined by gross inspection of the gonads. The ovaries, with ruptured membranes, were placed in Gilson's fluid (Bagenal, in Ricker, 1968) for a minimum of 24 hours. The pre- served and hardened ova were then counted directly. As an ancillary study the mean egg diameters were obtained by measuring a linear sample of 30 eggs from each mature female. £-«L& f ['34 l1..u..l.A .‘rlflo..4.r.~.»..0.i .m. 13 A composite of two collections was required in order to secure an adequate sample for determination of sex ratio. From the data (Table 3) a sex ratio of 1:1 was assumed. Table 3. Sex ratios of the brown trout populations based on a composite of the 1970 and 1971 collections. Percentage of 95% Confidence Site Mature Females Interval 1 44.6 31.7-57.6 2 48.9 33.6-64.9 3 51.8 37.6-65.1 All of the age III and IV females were found to be sexually mature. However, age IV females occurred so inconsistently that their contribu- tion to total fecundity was considered negligible. Consequently, only the fecundity for the productive age classes II and III appears in Table 4. Atretic ova, showing obvious signs of degeneration, were counted but not included in the results since fecundity in this study was taken to be the number of mature ova in a ripe female. Less than 1% of the total egg count in each of the Jordan River sites was composed of atretic ova and the Au Sable River had 3% atresia. Analysis of variance was employed to determine if fecundities and egg diameters differed between ages and among stations. After differences were detec- ted, Duncan's new multiple-range test with modification for unequal sample size showed where the differences existed between sites (Table 5). Apparently, sites 2 and 3 are similar but some differences existed between each of these and site I. Site 2 has the lowest population den- sity and the greatest size of individual females. It would be expected Table 4. Means and ranges ( ) for brown trout fecundity and egg diameters in the Jordan and Au Sable rivers. Site Age Year Fecundity Diameter (mm) 1 II 1970 263 3.385 ( 192- 373) (2.606-4.162) 1971 267 3.362 ( 197— 401) (2.896-3.784) III 1970 463 3.840 ( 249- 763) (3.203-4.162) 1971 376 3.638 ( 243- 567) (3.462-3.874) 2 II 1970 445 3.272 ( 168- 706) (2.835-3.712) 1971 786 3.500 ( 513-1142) (3.175-4.090) III 1970 983 4.051 ( 543-1207) (3.572-4.616) 1971 1263 4.153 (1110-1416) (3.963-4.343) 3 II 1970 394 3.382 ( 317- 538) (3.074-3.897) 1971 458 3.139 ( 301- 715) (2.633-3.643) III 1970 885 3.476 ( 652-1325) (3.178-3.802) 1971 963 3.842 15 Table 5. The significance of the differences in mean fecundities and mean egg diameters for age II and age III brown trout. An S indicates significance at P < 0.05, N indicates no signifi- cance. Fecundities Egg Diameters Sites Compared II III , II III 1 and 2 S S N S 1 and 3 N S N N 2 and 3 N N N N that the fecundity values would also be larger thus accounting for the greater number of differences with site 1, the opposite extreme in density, size, and fecundity. Since fecundity is correlated to body size, linear regressions were computed between fecundity (Y) and total length (X) and between fecun- dity (Y) and total weight (X) using the 1970 data. Pairs of slopes were tested for differences according to the F-test of Sokal and Rohlf (1969). A difference (P < 0.05) was noted in only one instance, the comparison of fecundity-length coefficients of age II fish from sites 1 and 3. The same situation did not exist with age III fish, therefore, no definitive conclusions can be assumed. Survivorship and Net Reproduction Rate The calculation of the net reproduction rate (R0) and the intrinSic rate of natural increase (r) are based on survivorship (1x), the probability at birth for a female to be alive at any given age (x). To determine lx it is necessary to estimate the initial population size from which the females originated, here considered to be the number of ova produced in 1969. This cohort would result in sexually mature age 16 II trout in 1972. Deevey (1947) has stressed that construction of a horizontal life table in which survivorship of a cohort is followed is superior to a vertical life table in which survivorship between age classes is calculated at one point in time. In the latter case, erroneous estimates can occur if the age composition of the population is unstable, probably the normal Situation in nature. Since the current project was not initiated in time to obtain fecun- dity data in 1969, the data from 1970 and 1971 were utilized as two estim- ators of the 1969 cohort (Table 6). Because the sex ratio was assumed to be 1:1 it was only necessary to divide the number of ova per hectare by two in order to obtain the number of females in the original cohort. The number of mature females per hectare expresses the age class p0pulation estimates corrected for sex ratio and for age II fish a correction is also made for the percentage of mature females in the population. The lx values in Table 7 were obtained by dividing the number cf age II females surviving until 1972 (Table l) by the two estimators of the 1969 female cohort (Table 6). The mx values express the mean number of female zygotes that an age II fish might be expected to produce based on the 1970 and 1971 values in Table 4. The products, Ixmx, represent the total number of female zygotes produced per female or the rate of multiplication in one generation. In life tables of other species, generally with a greater number of reproductive age classes, the lxmx values must be summed in order to include the contributions of all age classes. The summation is then designated R0, the net reproduction rate. In this study only the age II fish were considered since older fish make a negligible contribution to p0pu1ation expansion. In addition, by following the cohort only to maturity, the effects of variable fishing pressure in the three sites upon the older fish can be minimized. Estimated number of brown trout ova per hectare produced in Table 6. 1970 and 1971 as estimators of the 1969 female cohort. Number of Mature Total Number of Number of Female Site Age Females/Hectare OvaZHectare _Zygotes/Hectare 1970 1971 1970 1971 1970 1971 1 II 157a 1193 41,291 31,773 III 38 13 17,594 4,888 58,885 36,661 29,442 18,330 2 II 23b 37b 10,235 29,082 III 13 5 12,779 6,315 23,014 35,397 11,507 17,698 3 11 76c 69c 29,944 31,602 III 4 4 3,540 3,852 33,484 35,454 16,742 17,727 a -- based on 65.22% maturity factor b -- based on 59.09% maturity factor c -- based on 66.67% maturity factor 18 Table 7. Life table for female brown trout surviving to age 2.5 in 1972. (lxmx is equivalent to R0) Estimator Ix mx lxmx mx Ixmx Site Year (x 10-3) f (1970)_. (1970) (1971) (1971) 1 1970 4.5853 132 0.6052596 134 0.6144302 ‘ 1971 7.3646 132 0.9721272 134 0.9868564 2 1970 4.8666 223 1.0852518 393 1.9125738 1971 3.1640 223 0.7055720 393 1.2434520 3 1970 1.4932 197 0.2941604 229 0.3419428 1971 1.4102 197 0.2778094 229 0.3229358 Therefore, the individual lxmx values of Table 7 are assumed to be approximately equal to an expected R0 and can be used for comparative purposes since the mean generation length is equivalent among the sites. 0f the three sites it is apparent that the population in site 2 is far more capable of sustaining itself than either of the others. Site 1, considering the maximum survivorship value, has a population that might be marginally maintaining itself with the age II females alone. The Au Sable (site 3), however, has an extremely low Ro that would not be sufficiently enhanced even if older age classes had been' considered. Intrinsic Rate of Natural Increase The rate of increase of a population is a function of the birth and death rates. When the birth rate exceeds the death rate the popula- tion increase (r) is depicted by a positive slope. Three factors are l9 responsible for establishing and maintaining a positive r: a reduction in the age of maturation, an increase in fecundity, or increased sur- vivorship of reproductive females. Environmental conditions can act favorably or unfavorably on these factors resulting in fluctuations in the sign of r (Andrewartha and Birch, 1954). In this study, r values could be calculated for only one generation. The determination of r over this short time period must be used only to indicate the relative environmental conditions among the three sites at one point in time. The intrinsic rate of natural increase for each population was calculated according to the formula expressed by Birch (1948): 2 e'rxlxmx = l where e is the base of the natural logarithms; x is the age expressed as the midpoint of the year (2.5 in this study); and the product, lxmx, is as described previously. A summation of values was not required since only one age class was considered. Trial values for r were substituted into the equation along with each lxmX value from Table 7. The final r values accepted were those which caused the left side of the equation to most closely approximate unity. The resulting positive or negative num- bers are presented in Table 8 in two columns representing maximum fecun- dity of age II fish combined with the two survivorship estimators. Maximum fecundity was utilized in order to determine if negativity existed in any sites. The use of minimum fecundity would only serve to make negative numbers more negative. The r values in Table 8, by. definition, reflect the same conclusions as reported for R,. No matter which estimator of survivorship is utilized, the Au Sable population growth rate has a consistently negative slope indicating a declining population. .r.. fifl...w.l..oo. ‘1’. D r- Naif? . Table 8. 20 Intrinsic rates of natural increase (r) for the brown trout populations in the three study sites. The two columns result from the maximum fecundity observed (1971) combined with the two estimators of survivorship, 1970 and 1971 (Table 7). r Site 1970 Estimator 51971 EstTmator l -0.l95 -0.005 2 0.087 0.259 3 -0.452 -0.429 SCULPIN POPULATIONS ngulation Estimation The sculpin populations were estimated at the same time and accor- ding to the same methods as the brown trout estimations. The only difference was in age determination which utilized the sagitta otoliths (See Appendix E) since sculpins are essentially devoid of scales. Two species of Qgttg§_were present among the three sites. Site 1 had 100% Q, cognatus, site 2 contained approximately 7% C, cognatus and 93% C, bairgi, and site 3 had 100% 9, 921591, Because of the small percentage of Q, cognatus in the lower Jordan, adequate samples were never obtainable for correlation with the upper site. Consequently, some comparisons of an intraspecific nature could only be attempted between the mottled sculpin populations of sites 2 and 3. The popula- tion estimates for the three sites are presented in Table 9. As with the brown trout, the young of the year captures are biased because of the electrofishing technique, water conditions, and the small size of the specimens. Apparently, however, the sculpin populations per age class in the Au Sable River are much smaller than those of the two Jordan River sites. Sex Ratio, Sexual Maturity, Fecundity In March, 1970 and April, 1971, collections were made immediately prior to the spawning season to determine the overall sex ratio, the per- centage of mature females per age class, and the age-specific fecundity. The sample sizes and physical measurements of the sculpin females are 21 22 caeee_ema 062 a o o 0 mm o mF m“ o o >H m m_ o mmp mom mm cum mo, omm HHH mm mm mm NFm.F ape mom.m oem.m mmo.~ omm._ HH oom.~ mmm mmm omm Nwm.o moe.~ mom.m mmm.o_ ooF.m H s mmm.m Nmm.m « oom.mm mmn._r « mmo.m~ mo¢.mm o mum” pan okmp mnmfi Pumfi onmp mnmp —~mp oum~ mm< m mpwm N mpwm _ mpwm .mem>_e mpamm 3< new :mueoa mcu cw memuom; emu mcmapaum eo mamasac nmumswumm .m opamh 23 presented in Table 10. Apparently the females in site 3 grow at a faster rate. This is also true for the population as a whole (Quick, 1971). The sex of mature fish was determined by gross inspection of the gonads. The ova were preserved, enumerated, and measured by the same methods that were used with the brown trout. A composite of two collections was required in order to secure an adequate sample size for determination of sex ratio. From the data (Table 11) a sex ratio of 1:1 was assumed. All age II females were found to be sexually mature; a few mature age I females were also found but their contribution to total egg production was considered negligible. For the same reason the inconsistently occurring age IV fish were disregarded. The fecundity and egg diameters of the more productive age classes are presented in Table 12. In every age class in each site the fecundity increased in 1971 over that of 1970. This general improvement could be based on weather conditions but there is no evidence to support this theory. Mean fecundities and egg diameters of the mottled sculpin in the Au Sable River are consistently higher than those of equivalent age classes in the lower Jordan site. The Student's "t" test showed that the differences were significant (P < 0.01) in every comparison. Linear regressions were computed between fecundity (Y) and total length (X) and between fecundity (Y) and weight (X). The data used were from age 11 and III mottled sculpin from 1970 and the age II fish from 1971. Small sample size prohibited the use of age III data from 1971. Pairs of slopes by age class were compared by an F-test. The results showed a consistent, significant difference (P < 0.05) between the fecundity-length coefficients of sites 2 and 3. The Au Sable sculpins exhibit greater increase in egg production per unit increase 24 Table 10. 1970 and April, 1971. Lengths and weights of gravid sculpins collected in March, Number of Total Length (mm)_ Weight (9) Site Age Year Females Mean Range Mean Range II 1970 6 62 56-69 3 2-4 1971 7 61 57-74 2 2-5 1 III 1970 10 73 64-84 6 4-10 1971 5 79 71-90 7 4-11 IV 1970 3 82 62-101 10 6-18 1971 0 - - - - II 1970 I8 68 62-72 3 1-4 1971 8 79 70-85 7 4-11 2 III 1970 38 80 71-90 6 4-9 1971 3 92 85-98 12 8-16 IV 1970 7 104 97-114 12 11-15 1971 O - - - - II 1970 10 80 63-95 11 4-17 1971 10 97 91-106 16 13-22 3 III 1970 7 108 100-116 21 16-25 1971 2 110 _ 107-112 25 23-26 IV 1970 0 - a 1971 0 - - Table 11. Sex ratios of the sculpin populations based on a composite of the 1970 and 1971 collections. Percentage of 95% Confidence Site Mature Females Interval 1 55.4 42.4-68.4 2 54.4 46.6-62.3 3 62.3 40.3-75.2 Table 12. Means and ranges ( ) for sculpin fecundity and egg diameters in the Jordan and Au Sable rivers. Site Age Year Fecundity Diameter (mm) 1 II 1970 109 2.077 (66-167) (1.713-2.206) 1971 138 1.753 (86-234) (1.643-1.832) III 1970 162 2.179 (108-210) (I.983-2.343) 1971 244 1.974 (88-382) (I.833-2.072) 2 II 1970 231 1.270 (166-292) (1.063-1.488) 1971 406 1.315 (285-546) (1.200-1.422) III 1970 413 1.332 (256-712) (1.111-1.503) 1971 698 1.332 (491-825) (I.214-1.404) 3 II 1970 493 1.586 (301-684) (1.250-1.868) 1971 759 1.712 (590-987) (1.655-1.800) III 1970 958 1.733 (617-1247) (1.645-1.913) 1971 995 1.710 (970-1020) (1.681-1.738) 2.6 in length than do the lower Jordan fish. In comparing fecundity-weight coefficients, only the 1970, age II slepes were significantly different. Apparently the differences in the fecundity is more a function of length than of weight. Survivorship and NetReproduction Rate The survivorship of the mature age II sculpins in 1972 was calcu- lated from the number of ova produced by the p0pulation in 1970. The number of ova per hectare in the original cohorts is shown in Table 13. The number of mature females per hectare expresses the age class p0pu- lation estimates corrected for sex ratio. Since the ratio is 1:1, the number of females produced can be obtained by dividing the total number of ova per hectare by two. The 1x values in Table 14 were obtained by dividing the number of age II females surviving until 1972 (Table 9) by the 1970 female cohort (Table 13). This resulted in an "observed" survivorship for the sculpins rather than an estimated survivorship which was necessary with age II brown trout. Although sculpins older than age II are numerous enough to make an appreciable contribution to population growth, their survivor- ship was not computed since it would have required a vertical estimation. By utilizing only age II fish the relative production of the major contributors could be compared. The mX values express the mean number of female zygotes that an age II fish can produce based on the values in Table 12. The lxmx values are regarded as equivalent to R0 for com- parative purposes. The life table shows that age II fish alone are fully capable of maintaining or increasing the population in sites 1 and 3. The lower Jordan (site 2) population can not be sustained by age II fish. Further- more, if the lxmX products are computed using the vertical survivorship 27 Table 13. The number of sculpin ova per hectare produced in 1970. Number of Mature Number of Number of Female Site Age Females/Hectare Ova/Hectare Zygotes/Hectare I II 640 69,760 III 325 52,650 122,410 61,205 2 II 1331 307,461 III 29 ‘ 11,977 319,438 159,719 3 II 17 8,381 III 0 .______O 8,381 4,190 Table 14. Life table for female sculpins surviving to age 2.5 in 1972. . -3 Site IX (X 10 ) mX lxmx 1 21.5669 55 (1970) 1.1861795 69 (1971) 1.4881161 2 4.1072 116 (1970) 0.4764135 203 (1971) 0.8337616 3 6.2052 247 (1970) 1.5326844 380 (1971) 2.3579760 28 of the age 111 and IV females and the maximum mx, Ro would be: lxmx = 0.9481480. Even using maximum values the estimated R0 of site 2 would be less than that required for maintainance of the population. Intrinsic Rate of Natural Increase The r values in Table 15 for the sculpin p0pulations were computed according to the formula discussed with the brown trout. It follows, from the conclusions reached concerning the sculpin R0, that site 2 should exhibit a negative population growth. When comparing the positive slapes, the Au Sable sculpin population has a much greater r value than the upper Jordan population. However, it must be kept in mind that two species of cottids are involved with this comparison. Table 15. Intrinsic rates of natural increase (r) for the sculpin populations in the three study sites. Site r 1 0.159 2 -0.073 3 0.343 DISCUSSION The presence of the two cottid species in this study indicates that the streams are not degraded to any serious extent since both species have little pollution tolerance. Generally, Cottus cognatus inhabits the upstream, colder reaches of a stream near the source and Q, baigdj_inhabits warmer, downstream areas (Koster, 1937; Robins, 1961). Temperature was considered by Koster to be the greatest limiting factor in the distribution of Q, cognatus but the maxima in the upper Jordan are higher than those of the lower Jordan. It appears more likely that habitat might be more significantly limiting. The coloration of the slimy sculpin is more suited to the light-colored bottom type and the clear shallow water of the upper Jordan. The darker mottled sculpin is better suited to the deeper, darker water of the lower site and of the Au Sable site. The presence of either species in a stream, however, does not guarantee that a stream is suitable trout water. The author inventoried eight sites on a lower Michigan stream and found large populations of Q, bgirgj_but no trout. Apparently, some factors within the tolerance limits of sculpins are limiting to trout. If one compares the r values for the brown trout (Table 8) and the sculpins (Table 15) it can be observed that the signs of r are opposite for the two species in each of the three sites. The immediate impres- sion is that some form of competitive interaction is occurring, possibly a predator-prey relationship. Analysis of stomach contents was beyond the scope of this project and a search of the literature revealed 29 “git-i. r... P. pfl..vnri 1| 9. a. 1 W4.” ‘1‘ 30 conflicting opinions. Koster (1937) claimed that sculpins are inconse- quential as predators on trout eggs and fry. They may even act as buffers, protecting young trout from predation by other sources. Bailey (1952) is in agreement, stating that aquatic insects comprised 99.7% of the total number of all food items in sculpin stomachs and only 0.1% was composed of fish and fish eggs, not necessarily trout. Similar feeding habits were reported by Patten (1962). Greeley (1932) observed attempts by sculpins to capture trout eggs during the act of spawning before the redd could be covered but the trout females were generally successful in chasing them off. He suggested that the scul- pins probably could not dig into a trout redd and the eggs found in sculpin stomachs were probably obtained by scavenging the eggs that failed to get buried in the gravel. Conversely, Phillips and Claire (1966) found one species, 9, perplexus, was capable of moving through gravel depending on the size of the fish and the gravel. They conclude that sculpins could be significantly important as predators on salmonid eggs and alevins. Clary (I972) agrees that sculpins are potentially significant in trout fry mortality but not on eggs within the redd. Hunter (1959) found that sculpin food consisted exclusively of salmon fry during periods of fry migration. Salo, and Hikita and Nagasawa (in Patten, 1962), expressed the opinion that sculpins will feed heavily on salmon fry when the fry are in great numbers, suggesting a density- dependent factor. It is probably safe to conclude that sculpins are . competitive with trout as far as taking larval aquatic insects although the sculpins are benthic in feeding habits. They are probably opportun- istic, ingesting salmonid eggs and fry when the possibility exists. In laboratory aquaria sculpins were observed to feed readily on large steelhead eggs and nightcrawlers, and in the field sculpins have 31 been captured with large annelids or large sculpins extending from their mouths. Evidently, ration size is not as significant as some authors believe and sculpins could compete with trout for some of the larger food organisms. Although sculpins are benthic and secretive, they may be considered a food supply for trout. The eggs, deposited on the roof of caverns under rocks or logs, can be eaten by salmonids that are small enough to enter the crevices. This probably occurs when the guarding male temporarily leaves the nest. Metzelaar (1929) stated that the sculpins are "the most important food fish of trout in Michigan streams". Although they only move a few meters at a time when disturbed (Koster, 1937), they do maintain a home range (generally less than 50 m) over which they move nocturnally. This movement results in a nocturnal drift which is probably of adaptive significance in the dispersal of the species (Sheldon, 1968). However, the time of the drift coincides with the feeding habits of brown trout and the sculpins are particularly vulner- able to predation during this period. As yet, the interaction between the sculpin and trout populations is not fully understood. It is recommended from this study that the samples accrued over the past three years be subjected to stomach analysis in order to determine the food habits of the sculpins. Addi- tional collections should be made during the period between brown trout spawning and the swim-up stage. Similarly, trout stomachs should be - analyzed, especially from those fish collected at night. Salmonids produce a small number of eggs when compared with most fish but hatchability is generally higher (Wydoski and Cooper, 1966). However, the mortality rate for the first year is extremely high, re- sulting in a small number of females surviving even to the beginning of 32 the reproductive age classes. Yet, the age 11 brown trout in this study bore the major responsibility for egg production, as high as 86% of the combined fecundities of age II and III fish over the three sites. This is consistent with the findings of Libosvarsky and Lusk (1970) who re- ported 83%. Likewise, the sculpin age class II contributed an average of 84% of the total fecundity. Although the older age classes can have much higher fecundities, the decreased rate of survival observed almost negates their gonadal contribution. McFadden, §t_§1, (1962) and Bagenal (1969) have stated that larger brown trout eggs produce larger fry with higher survival rates than fry from small eggs. Therefore, the production of fewer larger eggs may be just as effective in recruitment as many small eggs. The upper Jordan site, in a nearly pristine condition, has a relatively high density of brown trout resulting in low mean fecundity and egg diameter. Yet, the p0pulation is just slightly less than unity in terms of R, and is probably fluctuating about unity in reality. This is possible because the rate of survivorship is in a state of homeostasis with the low fecun- dity and egg diameter values. McFadden, gt_gl, (1967) reports that survival rather than birth rate is the principal immediate cause of R, changes. Jensen (1971) claims that the compensatory mechanism that balances births and deaths is a change in age-specific fecundity. It is doubtful whether an increase in fecundity or egg diameter would have any effect on recruitment in the overcrowded population of the upper ‘ Jordan River. As McFadden has suggested, the same number of progeny will survive regardless of the number spawned. The trout population in site 1 represents the norm or standard against which other streams can be compared. It is natural for an unexploited population to fluctuate about the carrying capacity of the 33 environment. The resulting density has lowered the growth rate to where age 11 and some older trout do not attain legal catchable size and are not removed from the population by fishing. An interesting study could result if the current lO-inch limit was reduced to 8 inches, thereby cropping some of the age 11 fish. A decrease in survivorship and intra- specific competition should result in increased growth rate, fecundity, and egg diameter. The sculpins in site I also exhibit the highest relative density, greatest eggdiameter, and lowest mean fecundity. But again, the high survival value is compensatory and yields an R, > 1. The lower Jordan brown trout are much less dense than the trout in site 1. Accordingly, the mean fecundity and egg diameter values are high and survival is sufficient enough to yield the greatest R, of the three sites. Fishing pressure is not as great in site 2 as in site 1 so the low density can probably be attributed to lack of suitable brown trout habitat. Deep holes under obstructions are rare and the population is well-spaced. The fecund females are larger in site 2 indicating better nutrition but whether this can be attributed to in- creased nutrient input or to their distribution is a matter of conjec- ture. Water chemistry analysis shows the two Jordan River sites to be similar. Relative to the other sites the lower Jordan sculpins are inter- mediate in fecundity and low in egg diameter and survival values. Con- sequently, the R0 is somewhat less than unity even though the population is dense enough to produce a large quantity of eggs. The Au Sable brown trout are approximately as dense as in site 2 and as a population produce a similar complement of eggs. Assuming that the nutrient input in site 3 is greater, one would expect to find the 34 largest females and the greatest contribution to gonadal development. Instead, there is a trend for these factors to be intermediate among the three sites and when combined with the lowest survival rate the result is a very negative r. At the same time the sculpin population, with the highest relative fecundity and intermediate survivorship, has a very positive r. It does not seem possible that poor water quality could be responsible for the apparent decline of the trout population when the sculpins, good indicators of pollution, are experiencing a positive slope of almost the same magnitude. More likely the poor survival of age II trout can be attributed to fishing pressure. The Au Sable River is well used by fishermen, particularly in the study site which is adjacent to a public landing. The age II fish are almost all over the legal size limit and tend to be localized in long, deep holes where they can be more readily caught. It has been suggested by Incerpi and Warner (1969) that variations in fecundity can be caused by genetic differences in fish species in different watersheds. This thought must be considered in this study since the Jordan River drains west to Lake Michigan and the Au Sable River flows east through several dams to Lake Huron. Since plantings of brown trout from a common stock do not occur, the populations must be considered isolated. This is especially true of the sculpin popula- tions which were never planted. It is conceivable that intraspecific differences in fecundity could be a function of the separate gene pools and not a current environmental effect. Upon completion of this study it is apparent that trends in population abundance of cold-water species can be ascertained by the use of an approximate R, and r. For comparative work, horizontal life tables which include only the first really productive age class are 35 adequate for short-lived species. However, in comparative work, variable fishing pressures can exert an effect on survivorship. It is recommended that if heavily fished streams are involved, a non-game species such as the sculpin should be studied. It is also essential that a series of cohorts should be followed over a period of years in order to definitively ascertain the reproductive potential of a popula- tion. If a continued decline is observed, the knowledge could be vital to successful fisheries management of associated game species. At all times, other biotic and abiotic parameters must be monitored in order to establish the cause of possible negative effects. 1:5“ 1. v. LITERATURE CITED LITERATURE CITED Andrewartha, H. G. and L. C. Birch. 1954. The distribution and abundance of animals. Univ. of Chicago Press. 782 p. Bagenal, T. B. 1969. The relationship between food supply and -fecundity in brown trout Salmo trutta L. J. Fish Biol., 1: 167-182. Bailey, J. E. 1952. The life history and ecology of the sculpin, Cottus bairdi punctulatus in southwestern Montana. Copeia, 4: 243-255. Bailey, N. J. 1951. On estimating the size of mobile p0pu1ations from recapture data. Biometrica, 38: 293-306. Birch, L. C. 1948. The intrinsic rate of natural increase of an insect population. J. Anim. Ecol., 17: 15-26. Brungs, W. A. 1969. Chronic toxicity of zinc to the fathead minnow, Pimeghales promelas Rafinesque. Trans. Amer. Fish. Soc., 98: Clary, J. R. 1972. Predation on the brown trout by the slimy sculpin. Prog. Fish-Culturist, 34: 91-95. Deevey, E. S. 1947. Life tables for natural populations of animals. Quart. Rev. of Biol., 22: 283-314. Gislason, J. C. 1971. Species diversity of benthic macroinvertebrates in three Michigan streams. Unpub. master's thesis, M.S.U. Lib., 62 p. Greeley, J. R. 1932. The spawning habits of brook, brown, and rainbow trout and the problem of egg predators. Trans. Amer. Fish. Soc., 62: 239-248. Incerpi,A. and K. Warner. 1969. Fecundity of landlocked salmon, Salmo salar. Trans. Amer. Fish. Soc., 98: 720-723. Jensen, A. L. 1971. Response of brook trout (Salvelinus fontinalis) populations to a fishery. J. Fish. Res. Bd. Canada, 28: 458-460. Koster, W. J. 1937. The food of sculpins (Cottidae) in central New York. Trans. Amer. Fish. Soc., 66: 374-382. 36 37 Libosvarsky, J. and S. Lusk. 1970. On the bionomics and net production of brown trout (Salmo trutta Morpha Fario L.) in the Loucka Creek, Czechoslovakia. Polish Jour. of Ecology, 18: 361-382. Linton, K. J. 1967. The dynamics of five rock bass populations in a warm-water stream. Unpub. Ph.D. thesis, M.S.U. Lib., 102 p. Macek, K. J. 1968. Reproduction in brook trout (Salvelinus fontinalis) fed sublethal concentrations of DDT. J. Fish. Res. Bd. Canada, 25: 1787-1796. McFadden, J. T., E. L. Cooper, and J. K. Anderson. 1962. Some effects of environment on egg production in brown trout (Salmo trutta). Limn. and Ocean. Jour., 10: 88-95. , G. R. Alexander, and D. S. Shetter. 1967. Numerical changes and population regulation in brook trout (Salvelinus fontinalis). J. Fish. Res. Bd. Canada, 24: 1425-1459. Metzelaar, J. 1929. The food of the trout in Michigan. Trans. Amer. Fish. Soc., 59: 146-152. Mount, 0. I. 1968. Chronic toxicity of copper to fathead minnows (Pimephales promelas, Rafinesque). Water Research, 2: 215-223. Patten, B. G. 1962. Cottid predation upon salmon fry in a Washington stream. Trans. Amer. Fish. Soc., 91: 427-429. Phillips, R. W. and E. W. Claire. 1966. Intragravel movement of the reticulate sculpin, Cottus perplexus, and its potential as a predator on salmonid embryos. Trans. Amer. Fish. Soc., 95: 210- 212. Quick, R. F. 1971. The age and growth of brown trout (Salmo trutta) and sculpin (Cottus spp.) as it relates to eutrophication in the Jordan and Au SaEIe Rivers. Unpub. master's thesis, M.S.U. Lib., 86 p. Ricker, W. E. 1968. Methods for assessment of fish production in fresh waters. IBP, Blackwell Scientific Pub1., Oxford, England. 313 p. Robins, C. R. 1961. Two new Cottid fishes from the fresh waters of eastern United States. Copeia, 3: 305-315. Saunders, R. L. and J. B. Sprague. 1967. Effects of copper-zinc mining pollution on a spawning migration of Atlantic salmon. Water Research, 1: 419-432. Scott, D. P. 1962. Effect of food quantity on fecundity of rainbow trout, Salmo ggirdneri. J. Fish. Res. Bd. Canada, 19: 715-731. Shapovalov, L. and A. C. Taftz 1954. The life histories o; the steelhead rainbow trout Salmo airdneri airdneri an s ver salmon (Oncorhynchus kisutch). Calif. Fisfi. and Game, Fish Bull. 98. 38 Sheldon, A. J. 1968. Drift, growth, and mortality of juvenile sculpins in Sagehen Creek, California. Trans. Amer. Fish. Soc., 97: 495-496. Sokal, R. R. and F. J. Rohlf. 1969. Biometry. W. H. Freeman and Co., San Francisco. 776 p. Tsai, C. 1972. Life history of the eastern johnny darter, Etheostoma olmstedi Storer, in cold tailwater and sewage-polluted water. Trans. Amer. Fish. Soc., 101: 80-88. Vladykov, V. D. 1956. Fecundity of wild speckled trout (Salvelinus fontinalis) in Quebec lakes. J. Fish. Res. Bd. Canada, 13: Wydoski, R. S. and E. L. Cooper. 1966. Maturation and fecundity of brook trout from infertile streams. J. Fish. Res. Bd. Canada, 23: 623-649. APPENDICES 39 22m.e-oe.mv Awo.o-mo.cv Amm.o-ho.ov Ammm-mm_v Aee_-~m_v “ma_-NN_V me.a eo.o o_.o mm. om_ mm_ hoo.¢-oe.ov Aao.o-2o.ov Ase.o-mm.ov Aomw-mmpv A_om-eopv Aeom-mapv w_.~ mo.o mm.o mom om, Ne, Ao_.m-om.ov “mo.o-_o.ov Aem.o-am.ov AoFN-Am_V Amm_-ao_v Ae_~-oa_v Pe._ mo.o me.o mm, _m_ 38, maeeea_eu meeeeamaea eeaoeeez mee_om _aeoe “maeeeaz sueee_a¥p< deem Peace eeaeeez .gouw_\me :_ A v mouse; ecu memos mm vanadLQXd aea ae_=mae 6;» nee mp\op .m~\a .a\a .Fp\m .m_\A .e~\e .FM\m .M\m .~F\a .mN\m :6 added__ou eta: mmpasmm Loam: .meo>wa mpnmm =< ecu caugoa as» cw chop :r umpmmwpmm>ce mgouosegmq zuchac Lopez _mowsm;u < xHozmam< Maximum and minimum temperatures (°C) and dissolved oxygen concen- trations (mg/liter) in the upper Jordan River during the sampling periods of 1970 and 1971. 40 APPENDIX B 1970 1971 Temperature Dissolved Oxyggp Temperature Dissolved Oxygen Month Max. Min. Max. Min. Max. Min. Max. Min. May - - - - 14.0 6.0 11.7 9.4 Jun 20.0 10.0 11.2 9.8 18.7 13.9 9.3 8.1 Jul - - - - 18.4 10.0 9.8 6.8 Aug 18.0 11.4 10.4 9.1 16.3 8.8 11.5 7.7 Sep 15.6 12.8 9.6 8.3 - - - - Oct 8.9 5.6 11.7 10.5 11.0 7.5 12.7 10.7 Nov 4.0 1.5 13.3 12.6 - - - - uni-NH. I; %%Q 41 APPENDIX C Maximum and minimum temperatures (°C) and dissolved oxygen concen- trations (mg/liter) in the lower Jordan River during the sampling periods of 1970. Temperature Dissolved Oxygen Month Max. Min. Max. Min. Jun 16.7 10.6 10.5 9.6 Aug 15.5 12.5 11.1 9.0 Sep 15.0 12.2 11.1 8.5 Oct 7.0 5.5 ' 11.7 10.5 Nov 5.0 2.0 13.9 13.1 42 APPENDIX D Maximum and minimum temperatures (°C) and dissolved oxygen concen- trations (mg/liter) in the Au Sable River during the sampling periods of 1970 and 1971. 1970 1971 Temperature Dissolved Oxygen Temperature Dissolved Oxygen Month Max. Min. Max. Min. Max. Min. Max. Min. May - - - - 11.0 7.0 10.6 8.7 Jun 21.1 15.0 11.5 6.8 19.5 17.0 12.8 7.9 Jul 20.0 13.9 11.0 7.1 21.0 17.0 12.3 6.1 Aug 21.5 16.0 11.5 5.8 20.9 16.0 10.0 5.1 Sep 15.6 11.7 10.7 7.5 - - - - Oct 10.5 7.5 10.5 8.0 16.5 13.8 10.2 7.0 Nov 7.0 6.0 11.7 11.1 - - - - 43 APPENDIX E Appendix E. Age determination of sculpins. Photographs are from Cottus bairdi collected In the lower Jordan River in April, 1971. Age I Age 11 a. central core b. first summer c. second summer d. third summer Age 111 "IIIIILIIIIIIIIIIIIII