Resear~H Division

RESEAR~H DIVISION Oregon State .Game Commission Federal Aid Project F- 72- R I Coastal Cutthroat MARilYN llQHS GU!N LIBRARY HPJFiEI..D tf.}\RINE SCI ENCE CENTijl ORtGON STATE UNIVERSITY - -- _____...... "-11 1\..,~c; CATCH, MIGRATION, GROWTH AND SURVIVAL OF STOCKED COASTAL

CUTTHROAT TROUT IN MUNSEL LAKE, OREOON

by Delbert G. Skeesick, Graduate Assistant Research Division Oregon Game Commission

FEDERAL AID TO FISH RESTORATION Progress Report Cutthroat ecology

F-72-R-1 July 1, 1964-June 30, 1965

Oregon state University Corvallis, Oregon Fishery Research Report Ntunber 2 September 196 5 Munsel lake trout study1

A study of the migration, survival, growth and catch of coastal cut throat trout, Sa.lmo clarki clarki Richardson, of hatchery origin, has been in progress since November, 1961, at Munsel Lake, Lane County, Oregon. The purpose of the study has been to evaluate the present management practices, and to develop more efficient techniques for providing trout fishing in coastal lakes. The initial results of this study were reported by Hansen2. The latest phase of the study has been the release of equal numbers of equivalent size cutthroat trout and rainbow trout, Sa.lmo gairdneri gairdneri Richardson, to compare the survival, growth, and return to the angler of the two species. The total catch of each of numerous plants of cutthroat trout has been estimated through the use of a creel sampling program. The tendency of planted cutthroat trout to migrate downstream has been monitored at a weir on the Munsel Lake outlet. The weir has been in operation each migratory period since April, 1962. Each migrant was tagged for later identification. Survival of each group released into the lake has been estimated using either the Schnabel or Petersen method (Lagler, 1956). Each new release grolip was given a distinctive mark and was then used as the marked segment of the population. Survival of sea~run fish was estimated from tag returns and from recaptures at the Munsel Creek weir.

1Part of research toward PhD thesis at Oregon state University.

2 Hansen, D. 1963. The influence of natural mortality and other life history factors on the yield to the angler of planted cutthroat trout in Munsel Lake, Oregon. MS Thesis, Oregon state University, 67 pp (unpublished). 2.

The growth exhibited by each group of fish has been monitored by weighing and measuring all fish captured while netting for populati2n estimates, while trapping at Munsel Creek weir, and while checking tag returns from sea-run fish.

Characteristics Munsel lake is the lowest in a chain of four interconnected lakes which lie between the coastal sand dunes and a western ridge of the Coast Range. The lake has a surface area of 93.3 acres and reaches a maximum depth of 75 feet with a mean depth of 30 feet (Figure 1). The shoreline is 14,720 feet with the shore development of 2.o3. Thirty-two percent of the lake area is less than 15 feet in depth. The lake bottom is of three distinct types. Sand bottom extends out ward from the west and northwest shore to about the 40-foot contour. The south, east, and north shores are mainly clay-like in composition with some interspersion of rubble to about 40 feet. The deep areas, the upper end of the north arm, and the area around the mouth of Aikerley Creek have a soft, mucky bottom.

The surface temperature ranges from 46°F in December to 72°F in August

(Appendix A). A thermocline becomes established below 18 feet in early April and persists until early December. The epilimnion maintains a depth of about 20 feet during the warming period and increases in depth as the surface temperature declines in the fall (Appendix B).

30akley, A. L. 1962. Coastal Lake studies VII, Munsel Lake, Oregon. Fish Commission Research Division, Coastal Rivers Investigations; Clackamas, Oregon 23 pp. (unpublished). MUNSEL LAKE

0---==---==-===== 500 1000 SCALE IN FEET

Figure 1. Munsel lake, Oregon showing ac.cess points and bottom contours at ten foot intervals. 4-

The summer oxygen concentrations are near saturation in the epilimnion, exceed saturation in the thermocline and decline rapid~ in the hypolimnion (Appendix C and D). B.r mid-summer the oxygen concentrations below 40 feet is five ppm or less. Water samples taken August 9, 1960, indicate a total hardness of 36 ppm and total dissolved solids of 48.4 ppm (Oakley, £Q £11.). Aquatic vegetation is limited. water shield, Brasenia schreberi Gmelin, occasionally interspersed with pond weed, Potamogeton ~., forms a narrow band along the west and north shores. Several small patches of water lily,

Nuphar polysepa.lum Engelm., are found at the heads of coves, and one small

~tand of bulrush, Scirpus valid"Q.s Vahl, occurs near the outlet. Some cover for fish is provided by the many wind-felled trees lining the shore.

Munsel Lake has been managed as a trout lake since 1952. Prior to this study, most plantings were fish of sub-legal size. There is practically no natural propagation of salm.onids owing to the sandy bottom in tributaries.

The lake also contains sizeable populations of largemouth black bass,

Micropterus salmoides Lacepede; yellow perch, Perea flavescens Mitchill; kokanee, Oncorhynchus nerka Walbaum; and prickly sculpin, Cottus asper

Richardson. Lesser numbers of brown bullhead, Ictalurus nebulosus LeSueur; bluegill, Lepomis macrochirus Rafinesque; and warmouth, Chaenobryttus gu1osus

Cuvier, also inhabit the lake. At one time, squawfish, ptychocheilus oregonensis Richardson, were abundant in the lake, but none have been encountered during this study although they are common in the other lakes in the chain. Fishing conditions

The trout season in Munsel Lake usually opens the third weekend in April and continues until October 31. Fishing is allowed from one hour before

s~ise until one hour after sundown.

There is no closed season on warmwater species.

The bag limit is 10 trout, not more than five of which may be over 12

inches. Because of the rapid turnover of planted fish, a bag limit of five

fish over 12 ~ches has not occurred often enough to have influenced the

study.

A public access site is located in the southwest corner of the lake.

Here a boat launch ramp is surfaced with gravel, but because of its steepness,

it discourages many fishermen.

The only section of lakeshore accessible to bank fishermen is between

the boat launching site and a small beach about 200 yards eastward (Figure 1).

A resort located on the west side of the lake has boats for rent.

There are eight summer cabins and two permanent dwellings along the west

and north, shores of the lake. The lake residents fish from their own boats

with varying regularity.

Weather conditions affect the angling and anglers. Prevailing summer

winds from the northwest force boat anglers to fish in the more protected

north arm of the lake. At the same time the wind discourages the bank anglers.

Program

Resident anglers cooperated by recording their fishing effort and catch

on forms provided by the census clerk. Accompanying each form was an outline

\ of a fish with the fins identified, and a list of marks that they might encounter. 6.

Since the inception of the study, 63,019 fish weighing 10,352 pound$ have been stocked in Munsel lake. The releases are of four categories:

"fall fingerlings", released near the close of the fishing season for study of growth and survival; "post-season legals", released after the close of the fishing season for use in estimating survival of previous releases;

"pre-season legals 11 , released prior to the opening of the season for estimating over-winter survival of previous releases and for determining return to the angler; and "in-season legals", released between June and August for survival estimate of previous releases, and for determining the effectiveness of summer plants. All groups were used to determine the migratory characteristics of hatchery-reared cutthroat. Table 1 is a complete list of releases through the 1964 fishing season.

The release groups that were to be immediately exposed to angling were distributed throughout the lake using a planting boat, while those liberated in November were generally released at the public boat landing. The purpose of distributing the fish . from · a boat was to speed the mixing of the new release group with the resident groups, and to reduce the vulnerability of the new group to angling. 7.

Table 1 Chronological listing of groups released within the study period

Type Number Approx. of per fork Number Date S:Qecies :Qlant Mark 12ound len,:;th liberated ll/21/61 Cutthroat "Fall fingerling" RVAd 10.6 6.0 7,579 ll/21/61 II "Fall fingerling" BV 10.6 6.0 7,632

4/2/62 II "Pre-season legal" LVAd 4-5 9.0 4,000 8/2/62 II "In-season legal" LV 2.7 9-5 1,499 11/1/62 II "Post-season legal 11 LVRM 1.4 12.0 1,369 ll/29/62 II "Fall fingerling 11 HM 10.9 6.0 8,088

4/4/63 II "Pre-season legal11 RMAd 5.1 9.0 3,004

7/11/63 II 11 In-season legal" mAd 3.0 9.5 999

8/19/63 II "In-season legal 11 1M 2.3 .10.5 1,001

10/22/63 II 11 Fall fingerling" Ad 18.2 5.0 20,202 ll/13/63 II 11Post-season legaltt BVAd 1.4 12.0 708

3/D/64 II "Pre-season legal" RV 4-9 8.5 2,000 6/4/64 " "In-season legal" RVLM 2.8 9.5 1,002 6/4/64 Rainbow "In-season legal" .· LVRM 3.1 9.0 1,000

7/16/64 Cutthroat "In-season legal 11 RVAd 2.3 10.0 1,001

7/16/64 Rainbow "In-season legal" LVAd 3-3 8.5 1,000 ll/10/64 Cutthroat "Post-season legal" RM 1.2 12.5 468 / 11/10/64 Rainbow 11 Post-seal3on legal" LV 0.83 ]3.5 467 8.

Creel census

A creel sampling program was designed to estimate the total angler take of each of the release groups. The sampling schedule contained the following

characteristics: (1) one weekend day and one week day were sampled each week;

(2) all holidays, and both opening weekend days were sampled; (3) boat anglers

and bank anglers were treated separate~; (4) lake residents kept records of

their fishing efforts and their catch; (5) week days and weekend days were

in different strata and the sampling days were determined randomly, then were not sampled again until all the other days in the stratum had been

sampled; (6) all week days were assumed to be alike, as were weekend days.

All parties leaving the lake were interviewed to determine the number

of anglers, the total hours fished, and the catch by release group. Fisher

men were checked for the complete angling day from daylight until dark on

sampling days.

The catch records of the lake residents were collected each month. The total catch of each release group is summarized in Table 2. The

percent captured of fish released in 1961 and 1962 is from Hansen (££cit.).

The percent for 1963 and 1964 is calculated by dividing the catch of each

group by the number available to be caught. The number taken in gill nets

and the number leaving the lake as downstream migrants was subtracted from

the total number of each group released to determine the number available to

be caught.

The"fall fingerlingn cutthroat returns ranged from 13.4 percent in the

1962 season to 0.32 percent in the 1964 season. A sample of the latter group

was collected short~ after release, and all specimens were examined for

disease by Dr. John Fr.yer, microbiologist at Oregon state University, Corvallis,

Oregon. Of the 37 specimens examined, 43 percent had overt symptons of kidn~ 9. disease, 12 percent were possib~ infected, and 45 percent had no indication of the disease. One fish of this group also was infected with furunculosus. The percentage incidence of the two diseases are minimal since preserving the specimens precluded culture of the infected tissue. The slight difference in yield from the RVAd and BV "fall fingerling" releases may be attributed to different planting sites. The BV group was released at the public boat launch while the RVAd group was released into Aikerley Creek about 50 yards above Munsel lake. Subsequent gill netting in the upper lakes indicated that some of the Aikerley Creek group had migrated upstream. The "pre-season legal" cutthroat returns were from 43.0 percent for the

1962 release to 23.4 percent for the 1963 release. The 1964 return was intermediate, although pathological examination of five specimens revealed a 6b percent incidence of both kidney disease and furunculosus.

The "in-season legal" cutthroat returns ranged from 75.3 percent for the 1962 release to 36.8 percent for the July 1964 release.

The 11post-season legal" cutthroat returns were 23.7 percent for the

1962 release group and 33~4 percent for the 1963 release group. The 1964 release group will not be available to anglers until April 24, 1965. The relative~ poor return from these groups can be attributed to downstream· migration before the trout season opens, and to mortalities during the 5-1/2 month interval before the.y became available to the angler. Table 2 shows that there was little second or third-year contribution . from aey plant •

The relationship between size at release and percent return to the angler is indicated in Figure 2. The two curves describe the highest and lowest returns respective~ for the cutthroat released at equivalent sizes. Table 2

Estimated total catch of each release group expressed as a percentage of each group available to the angler

Fall finger li!!.§s Pre-season legals Year Wild RVAd BV RM Ad . LVAd RMAd RV 1962 847 1,002 1,686 1963 31· 32 16 262 .34 697 1964 5 0 3 15 65 1 1 546 Totals 36 879 1,021 277 65 1,721 698 546

Percent captured 11.6 13.4 3.4 0.32 43.0 23.4 28.8

In-season legals Post-season legals Year LV !MAd IM RVLM L~ RVAd LVAd1/ LVRM BVAd 1962 1,100 1963 29 346 491 316 1964 l 21 60 !:J:J.7. J,LaJ, ).24 27.6 0 122 Totals 1,130 367 551 437 444 324 276 316 192

Percent captured 75.3 42.8 62.5 46.6 49.0 36.8 30.5 23.7 33.4 .b 1/Rainbows 11.

;:tl P. M t) P. ..s:l ~ Ill •.-I fH fH 0 M ~ t) § z

OJ ses~Te~ ~UTT~9~U1J TlOS'WS-lSOd

- ses~t~~-- -- uos-eas-ur

S9S~T9~ UOS~S-lS0d ~--~------~------_.------~------~0 0 0 0 ...::t N 12.

The fish planted in Munsel lake are extremely vulnerable to angling.

Many good catches of newly planted fish occur within a few hours after release. Hansen (op cit.) observed that 90 percent of the catch of fish which were available at the start of the 1962 season was removed within the first six weeks of the season. Fifty percent of the total catch of the 1962 in-season plant was taken in the first five days after release. Rapid removal of available fish occurred in 1963 and 1964 also.

The "post-season legal" and "pre-season legal" cutthroat (BVAd and RV) plants available at the start of the 1964 season were removed considerably faster than their counterparts (LVRM and RMAd) at the start of the 1963 season (see Figure 3). The more rapid removal was partly due to a 26 per cent increase in fishing effort during opening week. Two factors also operated to reduce the availability of the 1964 groups. The 1964 migratory season peaked approximately two weeks earlier than the 1963 season, and the 1964 "pre-season legal" release (RV) was diseased.

The 1963 "fall fingerling" cutthroat release group (Ad) had a slower harvest rate in 1964 than its homolog in 1963 probably as the result of the small size of fish. The mean size of this group did not reach the eight-inch minimum size limit until two weeks after the season had opened. The group demonstrated a poor return to the angler, probably because of its diseased condition at the time of release.

The more rapid return of "in-season legal" cutthroat of the July 1963

(LMAd) release was due to a doubling of fishing effort the first week after the fish were stocked (see Figure 3). During the 1964 season, effort declined after the July release (RVAd). Farlier plants and a group of rain bow released at the same time also contributed to the creel, removing some of the pressure from the July 1964 release. ..,--.,.------/

"Pre-seas on legal" 6o "Post-season legal"

40 1963 season 1963 season 1964 season 1964 season -a 20 of-) ~ C) -;;: 0 of-) B 100 ~ 0 / 80 / / ,-- r-/ r-" 60 ./ /"" I / I ,----J I 40 / 1 "In-season legal" """' "Fall fingerling" I I 1963 season I 20 season / 1964 season season 0 2 4 6 8 10 12 2 4 6 8 10 12 Weeks ~ Figure 3. Cumulative percent of total catch by week for comparable cutthroat releases. . 14.

Equal numbers of cutthroat and rainbow were planted in the two 1964

"in-season legal" releases. In each case the two groups of fish were mixed in the liberation truck and distributed around the lake in a planting boat. As a result they were subject to the same conditions and the same fishing pressure. The cutthroat were cropped considerably faster than the rainbow {Figure 4). Five weeks after the June groups were released, 93 percent of the total cutthroat (RVLM) catch and 65 percent of the total rainbow (LVRM) catch had been taken. The total catch for the season for these two groups was equivalent (Table 2). Five weeks after the July groups were released, only 69 percent of the total cutthroat (RVAd) catch and 51 percent of the total rainbow (LVAd) catch had been removed (Figure 4). At the t:ilne the last two groups were released, the epilimnion was 20 feet thick and was 70•F. The fish moved into the deeper, cooler water and consequently were not as available to the anglers. This somewhat slower rate of removal was true of

the July 1963 (LMAd) cutthroat release also. The fishing effort expended by the different types of anglers is tabu lated in Table 3. The distribution of effort over the 1963 and 1964 seasons is shown in Figure 5. Table 3 Calculated total effort and total catch by the different angler types for each year, 1962 to 1964

Boat &.nk Residents Total Total Total Year Anglers hours Catch Anglers hours Catch Anglers hours Catch

1962 1,683 3,155 3,593 379 543 283 200 376 759 1963 787 2,133 1,349 151 248 150 214 630 622

1964 1,078 2,832 1,800 445 864 155 276 650 40.9 15.

June release Cutthroat - 80 ------...... ---Rainbow--- / 60 / / / 40 / ..c: / 0 / -+' / ~ 20 / / ,.; / ~ -+' ~ 0 -+' 5i July release _... 0 ______,.,.. ~ r p,. 80

_.. 60 ,_ ___...... - // -Rainbow 40 / / / 20 / / / 0 ~~~~~~--~--~--~~--+---~--~----~--~--~~--~~1 2 3 4 5 6 7 8 9 10 11 12 Weeks after release Figure 4. Cumulative percent of total catch by week comparing simultaneously released cutthroat and rainbow groups in 1964. 900 1963 season 700 1964 season

400

I ~ I I\ I I \ 300 I I \ I ~\ I \ I ~ I \ I \ \ I \ I \ I \ I \ II I I \ I "\ A \ I \ I \ I \ I \ I \ I \ I \ v \ I II \ I v II \ I 100 -_j I' ' \ I \ I " 2 Week of season

Figure 5. Calculated week~ effort by all types of anglers during the 1963 and 1964 fishing season. 17.

The greatest effort is expended by boat anglers who either launch their own boat or rent one from the resort on the west side of the lake. The boat angler catch-per-hour for the three years has been 1.14, 0.63 and 0.64 fish respective~. The lake residents angle from boats also, and for the first two years of the study had higher success ratios ttmun non-resident boat anglers.

The lake residents had a catch-per-hour rate of 2.02, 0.91 and 0.63 fish.

Their better success ratio is probab~ due to better knowledge of the distribution of fish in the lake, better knowledge of recent releases, and better utilization of the prime fishing hours. Bank anglers have the poorest success as exhibited by the catch-per-hour of 0.52, 0.60, and 0.18 fish for the three successive years. The reason for this relative~ poor return f~r the effort expended is that bank anglers are limited to a 200-yard section of shoreline near the boat landing in the southwest corner of the lake. As the surface water temperature rises the fish tend to move into deeper water during the day and frequent the shore area late in the evening to feed on emerging mayflies. The increase in anglers and decrease in success during the 1964 season was primari~ due to bank anglers continuing to fish after the movement to deep water had occurred.

Migration

The seaward migration of trout liberated in the lake has been monitored since April 1, 1962. The total number of migrants of each release group is listed in Table 4.

The second and thi~d-year migrants were primari~ fish that had moved into the outlet stream short~ after release and perhaps because of the slower growth in the stream did not migrate during the first season that they could have done so. Several fish in the second and third-year migrations were fish that had migrated the first year, returned, spawned, and were heading seaward again. 18.

Table 4 Downstream migration of cutthroat trout trapped at Munsel Creek weir, 1962-1964

Percent of number Release Date of Number of migrants originally grouQ release 1262 126.2 126~ released RVAd ll/21/61 286JJ 33 2 4.2 BV ll/21/61 30c}l 31 2 4.5

LVAd 4/2/62 433 12 3 ll.2 LV 8/2/62 19 1.3 LVRM ll/1/62 142 2 10.5 RM ll/29/62 65 14 1.0 RMAd 4/4/63 210 16 7.5

!MAd 7/ll/63 4 0.4 1M 8/19/63 26 2.5

Ad 10/22/63 65 0.3 BVAd ll/13/63 90 12.7

RV 3/13/64 69 3.4 Wild fish 18 36 20

1/An estimated 10 percent migrated before completion of trapping facilities.

The high number of wild cutthroat migrating compared to the number of wild cutthroat catight in the lake (Table 2) indicates that the major pabitat of wild cutthroat is in the streams, where they are not fished. The small

over-all number of wild cutthroat in the catch and in the migration iindicates that suitable spawning and nursery areas are virtually non-existent.

The downstream migration began in March of each year, peaked in April and May, and ended in June. The weekly totals shown in Figure 6 indicate --.---...------.. .

19.

250 1962 200

100

en t- 0 z 200 ~ a:: 1963 -(!) ~ 100 IJ.. 0

a:: IJJ m 0 :!E 200 z~ 1964

100

JUNE

Figure 6. Week~ downstream migration of cutthroat trout at Munsel Creek weir. 20 . some variation in timing from year to year. There was a tendency for the fish planted at a larger size to migrate earlier. During the 1962 migratory season an estimated 10 percent moved downstream before trapping facilities were completed. Migrating fish were tagged with the vinyl subcutaneous tag described by Butler (1957) during the 1962 and 1963 migratory seasons. A modification of the spaghetti tag described by Watson (1963) was used during the 1964 migratory season (Figure 7). Each fish was anesthetized with MS 222,

Sandoz, weighed, measured, tagged, examined for marks, and released below the weir.

Tag returns were 1.56 and 0.98 percent respective~ for 1962 and 1963 when the subcutaneous tags were used. The 1964 migrants with the spaghetti tag had a return of 19.34 percent.

Most of the tagged fish were captured in the sea-run cutthroat fishery on the Siuslaw estuary. The 1964 returns were 2 fish in late July, 28 in

August, 1..4 in September, and 2 in ear~ October. The 1962 returns were 4 fish in August, 6 in September, and 1 in October. Table .5 lists the locations of the captures.

straying was documented in 1962 and 1964 respective~ when 6.7 percent and 7.7 percent of the total tag recoveries occurred in river systems other than the Siuslaw. One tagged cutthroat was recovered in 1962 from the Sixes

River which empties into the Pacific Ocean 85 miles south of the Siuslaw

River. In 1964 four fish were recovered in the tidewater area of the Alsea

River, 32 miles to the north of the Siuslaw River. The perce~t straying reported here is a minimum since no effort was made to encourage returns from other river systems. Figure 7. Modified spaghetti tag on downstream migrant cutthroat. (photo courtesy R. Osterling). 22.

Table 5 Recovery of tagged cutthroat from each downstream

migration through June, 1965

Year of ca:Qture Location of recovery 1962 1963 1964

Munsel Creek weir (upstream trap) 1 3 3

Munsel Creek weir (downstream trap) 4 2 3

Siuslaw River 10 45 North Fork Siuslaw River 1

Alsea River 4 Sixes River 1

Total 16 5 56

TWo other examples of straying were reported. A subcutaneous tagged cutthroat was released into the North Fork Alsea River at the Oregon Game

Commission Alsea Hatchery March 6, 1963 and was caught on August 20, 1963 at Mapleton on the Siuslaw River. A wild cutthroat was tagged at Munsel Creek weir with a spaghetti tag on April 24, 1964 and was captured August 7, 1964 in the Alsea River near the mouth of Canal Creek.

Survival and mortality

As indicated by speedy removal of each new~ released group (Fidures

3 and 4) and rapid decline in angling success (Table 6), angling mortality was maximum immediate~ after release. The main contribution of each release group was within the first five weeks after it became available to the angler.

Variation in the catch-per-hour during the latter weeks for the 1963 "in- season" plants was part~ due to small sample size resulting from light fishing effort. The high values for the August 1963 release group during .23. the tenth and eleventh weeks were the result of increased availability of the remaining fish. The lake surface temperature had dropped sufficiently for the fish to move into shallower water just before the end of the season.

Table 6

Catch-per-hour each week for "pre-season legal" and "in-season legal"

cutthroat and "in-season legal" rainbow, released in 1963 and 1964

Weeks 1963 cutthroat 1964 cutthroat 1964 rainbow after "Pre- "In- "In- 11Pre- "In- "In- "In- "In release season" season" season" season" season" season" season 11 season 11

1 0.17 0.97 1.08 O.ll 0.41 o.oo 0.67 0.41 0.48 0.13 0.24 0.07 3 0.47 0.34 0.39 0.39 0.28 0.37 0.16 4 0.36 0.35 0.09 0.29 0.43 0.27 0.33 5 0.81 0.32 0.87 0.10 0.15 0.21 0.22 6 1.33 0.13 0.22 0.05 0.06 0.08 0.12 7 0.52 0.04 1.00 0.55 o.oo 0.15 0.02 0.02 8 0.35 0.05 0.24 0.02 o.oo 0.08 0.30

9 0.09 0.07 0.04 0.02 0.19 0.17 0.17

10 0.15 0.09 1.78 o.oo o.oo 0.11 0.05 0.49

11 0.00 1.08 1.04 0.20 0.00 0.22 0.02 0.36

12 0.10 0.06 0.00 0.20 0.19 0.27

1/Dashes indicate no fishing effort expended.

The "in-season legal" rainbow release of June, 1964 had a catch pattern quite similar to the cutthroat but the July rainbow releases reacted quite j. differently (Table 6). Th~ did not enter the fishery until the third. week, and then contributed well until the end of the season.

Estimates of survival where each new plant serves as the marked fish for 24. a population estimate indicate that there was a relationship between time of year and percent mortality per week. A composite of week~ mortality rates is shown in Figure J. The highest rates occur in the spring when the fish inhabit the surface area. The rate declines in the summer when the fish inhabit the deeper areas, then increases again in the winter as the fish again move to the surface. The mortality for each group in the lake from causes other than angling ranged from less than 22.2 percent for the 1962 "in-season legal" release to 98.8 percent for the 1963 "fall fingerling" release (Table 7). The mortality figures for the RV, RVLM, RVAd, LVRM, and LVAd release groups will be reduced on~ slight~ when the 1965 catch and migration data are known.

There is a relationship between the sii~e at release and the percent mort-ality from unknown causes. In each year, fish of legal size released prior to the season had a higher mortality than those released later in the season at a larger size (Table 8). The unknown loss of 11 post-season legal'~ fish was high because these fish were at liberty approximately five months before the.y could be fished. Thus, immediate availability had the effect of reducing the mortality due to unknown causes. 25.

~ (I) 5 (I) ~ ~ (I) p. 4 t>. ;q+) <17 3 t ~ 2

~(I) (,.) ~ (I) jl., 1

0 Spring Summer Fall Winter

Figure 8. Upper and lower estimated percent weekly mortality to causes other than fishing, for "pre-season 11 and "in-season" cut throa.t and rainbow trout. 26~

Table 7 Mortality from known and unknown causes for all release groups stocked prior to the close of the 1964 fishing season

Total Loss from Percent loss Release Estimated downstream Sampling unknown from unknown grOUf:1 catch migrants mortalit;y causes causes RVAd 879 321 c)Y 6,370 84.1 BV 1,021 342 1411 6,255 82.0 LVA.d 1,721 448 1511 1,816 45.5 LV 1,130 19 lrfl 333 22.2 LVRM 316 144 4711 862 63.0 RM 277 79 26 7,706 95.3 . RMAd 698 226 66 2,014 67.0

LMA.d 367 4 140 488 48.8 IM 551 26 ll8 306 30.6 Ad 65 65 ll6 19,956 98.8

BVAd 192 90 132 294 41.5 RV 546 69 106 1,279 64.0 RVIM 437 65 500 50.0 LVRM (Rainbow) 444 94 462 46.2 RVAd 324 ll9 558 55.8 LVAd (Rainbow) 276 95 623 62.3

111962 sampling mortality unknown 27. Table 8

Percent mortality from unknown causes for group stocked prior to the

close of the 1964 fishing season according to time of release

Year of "Fall "Pre-season "In-season "Post-season release fingerling" legal" legal" legal 11 Cutthroat 1961 84.1, 82.0 1962 95-3 45-5 22.2 63.0 1963 98.8 67.0 48.8, 30.6 41..5 1964 64.0 50.0, 55.8

Growth

The estimation of growth in length and weight, over a long period of time, has been hindered by the rapid decline in numbers of each group after release. The 1961 "fall fingerling" plants (BV and RVAd) provided the best samples for growth analysis. Some migrated to the ocean in the spring of

1962, while others became resident in the lake or in Munsel Creek until the 1963 migratory season. At migration the mean fork length of the creek resident fish was 228 nun (Figure 9) and thE~ir mean weight was 88 gm (Figure 10).

The growth rate was 4 nun and 3 gm per month. Fish that remained in the lake until the 1963 migration ha.d a mean increase of 7 nun in length and 9 gm in weight per month. Fish moving into the marine environment had an accelerated growth the first sununer. The mean increase in length between May and

November was 21 mm per month and the estimated increase in weight was 49 gm per month. The weight estimate was derived by comparing the known lengths of 1963 returnees at recovery against a length-weight curve developed from 1964 tidewater recoveries. .--~~------~~ - - ' -

500

400

~-~Sea / Run (10) ------stream (40)

100 Dec. e • Apr. une Aug. ug. .1961 1962

Figure 9. Increase in length of 1961 "fall fingerling" cutthroat inhabiting three different areas, sample size in parentheses.

l\) .00 500

Sea Run (8) 400 --~

300

I I 200 La.ke (8)

100 ------stream (36)

0 ~~--~~--~----~~--~----~~--~~--~~--~----~~--~---Dec. Feb. Apr. June Aug. Oct. Dec. Feb. 4pr. June Aug. 1961 1962 1963 Figure 10. Increase in weight of 1961 "fall fingerling" cutthroat inhabiting three 1\) '-0 different areas. Average weight of sea-run fish estimated from condition . factor of 1964 sea-run fish, sample size in parentheses. 30.

Activities related to spawning caused the sharp drop in weight of the sea-run cutthroat. The estimated weight loss was 99 gm per fish, which was a 24 percent decline from mean weight the previous November.

Summary

A study of hatchery-produced coastal cutthroat trout released into

Munsel Lake has been in progress since November, 1961. This report summa rizes the return to the angler, migration, growth, and survival aspects of the study.

Eighteen plantings totaling 63,019 fish were made. Four size groups were released at four different times of, the year. Highest returns were from an intermediate size group planted while the fishing season was in progress. Lowest returns were from the fingerling size group planted in .the fall after the close of the season. The largest size group planted after the season closed contributed to the fishery at about the same rates as groups released just prior to the opening of the season.

The downstream migration began in March, peaked in April and May and ended in June of each year. All migrants were tagged as they moved down

Munsel Creek. Fish planted at a :larger size contributed most heavily to the migration. Large fish migrated earlier. Returning sea-run fish were captured in the Siuslaw River estuary from July through October. Anglers accounted for 79 percent of the tag recoveries. About 7 percent of the tag recoveries were from river systems other than the Siuslaw.

Estimates of survival were made using each new release group as the marked-fish segment of the population. The highest mortality rate occurred in the spring. The mortality rate declined through the summer and fall and increased again in the winter. Poor survival of one lot of fish released as fingerlings was caused by disease. 31.

Growth rate in three different environments was monitored. stream growth averaged 4 mm per month, lake growth was 7 mm per month, and marine growth was 21 mm per month. Spawning activity of returning sea-run fish caused a 24 percent loss in body weight. 32.

Literature cited

Baldwin, E. M. 1956. Geologic map of the lower Siuslaw River area, Oregon. U. S. Geological Survey Oil and Gas Investigation Map OM-186. Butler, R. 1957. The development of a vinyl plastic subcutaneous tag for trout. Calif. Fish and Game, 43(3):201-212. Iagler, K. F. 1956. Freshwater fishery biology, Wn. C. Brown, Dubuque, Iowa, 1956, 421 pp. vatson, J • . 1963. A method for tagging immature herring. U. S .. Fish and Wildl. Serv. Spec. Sci. Rept.--Fish. No. 451, 7 pp. 33.

APPENDI.X ~ ·.-! Q) -'= 6o• ~ Q) ~ -'= &! II) Q) Q) ~ bO Q) 50° 0

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT . NOV. DEC. VJ Appendix A .t-. . Munsel Lake surface tem.perature-1964 35 •.

5 April 6 May 8 June 0

+l C) C) 40 '+-! -~ ..Q 50

15.C) Q 6o

70 40. so· 6Q• 70° 40° so• 6oo 70° 40. so• 6o• 70.0

6 July 16 sept. 22 Oct. 0

+l C) C) '+-! 40 -~ ..c: +l 50 0.. I) Q 60

70 40° so· 6o• 70° 40° so· 6o• 70° 40° so• 6oo 70° Temperature in p• Appendix B Munsel Lake Temperature Profi1es-l964 0

------

70L-~~--_.----~--~--~----~--~--~----~--~--~----~--~ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Oxygen in PPM

Appendix C

Munse1 Lake summer oxygen profiles-1964 0

--...- ..> ...-...-

28 Sept.

70L-______. ______~------~------~------~------~--- 0 20 40 60 80 100 120 Percent saturation

Appendix D

Percent saturation values for oxygen profiles in Munsel Lake-1964 •j . : ; j: . i .. I''. : ·I

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