':>\\ 1..'2-'2 J\4 Qt1 Inter-Departmental Report if\\). 9t-

BRISTOL BAY DATA REPORT NO. 94

NUSHAGAK RIVER PINK FORECAST STUDIES

by Wesley A. Bucher Fishery Biologist

Alaska Department of Fish and Game Division of Commercial Fisheries

ec.\'l'i~ ~e<'l, l'S :/..~) ; t->.R'-' ~"'-"s / Dillingham, STATE OF Au\S~o"-~~~1 . fi'JELIS DEPARTMENT OF FIS~O cilME Alaska Resources Lillrarv & {nformation Services LIBRARY library Buik!ing, Suite 111 January, 1983 3211 ProviUcncc Drive P.O. BOX 3-2000 Anchorage, AK 99508-t-6\4 JUNEAU, ALASKA 98802·2000 Table of Contents ··Page

List of Tables ...... •.. i

[] List of Figures ...... i

Introduction ...... •....•...... •... 1

Materia 1 s and Methods...... 5 [] Sampling Site •...... 5 Sampling Techniques ...... •...... 6 Adjustment and Expansion of Counts ...... •...•. 12

[] Results .•....••••...... •...... •...... •.. 13

Pink Salmon •...... •...... 13 0 Migratory Patterns ...... · ...... ••....•.. 15 Chum Sa 1men ...... •...... •..... 15 Other Species ...... •...... 17

Discussion ...... •...... 17

Marine Survival •...... •...... •...... •....•...... 19 0 Recommendati ens ....•..•....•.....•....•...... 19 0 Literature Cited ...•...... •...... •....•...... 21 Appendices. • ...... • . . . • ...... • ...... • . • . . . • . . . 22

0 J 0 J u J J List of Tables Table 1 Catch and escapement of to Nushagak district, r1u , by year, in thousands of fish, 1958-1982 ...... 3 2 Escapement and return of pink salmon to Nushagak district, [] Bri s to 1 Bay, by brood year, 1958-1982 ...... 4 3 Pre-season forecast and actual return of pink salmon to 0 Nushagak district, Bristol Bay, by year, 1966-1982 ...... 4 4 Discharge records for Nushagak River at Ekwok, in cubic 0 feet per second, by month, 1981 ...... •.•...... • 7

[] List of Figures Figure 1 Nushagak River drainage, Bristol Bay area .....•.•...... 2 2 Surface velocity and depth profile at the sample site, J Nushagak River, 1981 •••.•..•••...•...... •..• ·•..••.. 8

3 Inclined-plane trap used for catching· pink fry, 0 Nushagak River, 1981 .....•.•••...... •...... •... 11 4 Vertical sampling unit used for catching pink fry at depths in the Nushagak River ...... •.•...... 10 5 Daily catch per hour of pink salmon fry in the Nushagak 0 River, 1981 ...... ••...•....•...•....•••. ·.· .....•.••.•.... 14 6 Daily catch per hour of fry in the Nushagak [] River, 1981 ...••...... •...••...••...•....•...... ••.•.... 16 ] l [] u ] 'J [] ll INTRODUCTION Pink salmon is the second most abundant species in Bristol Bay with runs n occurring only in even years. Pink salmon production during odd years is almost 0 non-existent. The majority of pink salmon are produced from river systems entering the Nushagak district, with the bulk of this production originating 0 in the Nuyakuk River, a tributary to the Nushagak River (Figure 1). Since 1958, the total run (catch plus escapement) of pink salmon to the 0 Nushagak district has averaged 3.2 million fish (Table 1). This includes 1972, lJ a year which produced a very low total run of 126,000 fish, presumably a result of the severe winters of 1970-71. In 1976 however, an escapement of 863,000 0 pinks to Nushagak district produced a phenomena 1 run of 13.8 million in 1978, for a 16 to 1 return per spawner (Table 2). 0 The estimated exvessel value, or the value of pink salmon paid to fishermen 0 in Bristol Bay, was 5.4 million dollars in 1978 and 2.2 million dollars in 1980. During the 20-year period from 1961-80 pink salmon have accounted for about 4% 0 of the exvessel value of the commercial salmon harvest for all five species in Bristol Bay. 0 Forecasting pink salmon returns has been extremely difficult, as returns u per spawner have ranged from a low of 0.1 to nearly 17 (Table 2). Past forecasts .have been developed using spawner~return ratios, which are proved to be unreliable (] and consequently of very limited value. The most recent example is the Depart-

' . [J ments 1980 forecast ;of 1.4.7 million pinks, of which 5.0 million fish actually returned (Table 3). , The 1980 forecast was prompted by the 1978 record return [] which provided an esc'apement of 9. 4 million, more than twice as 1arge as any previously observed. 'Forecast error for pink salmon has average 2.6 million u fish or slightly le~s than the long-term average total run. This forecasting j 1 J bRISTOL DAY

nr.vrstD tlrl DnAwN IY I. i!UHin .. ~~··.. ·· .. ..$ ,. .. . ,...... ~" ..~ " ~ +.. JE-~ I NONVIAHUK r; r.Y.~- - 18' --·- ·•1": "'-'"~Kf·~--·

\\_ ~AKF. 1··-... ·. \::::!nO!IVI:HOn ·''-1-~·. ~~- Jc·-.~\-·~. \ 1>~. .... ~_.,,~ .. J --\1 II (r~./>-l \-. Sample CAP I CONU ANTINI Site

BRISTOl BAY EGEGIK "'"r,. '-----._.,...-

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CAP I! LAKU N tO I 0 10 10 30 ·/j'·· ...... -- ::p:e •• ,,,. tpo" M ll r s tpe• •!•" I D 1] l~ Table 1. Catch and escapement of pink salmon to Nushagak district, Bristol Bay, by year, in thousands [] of fish, 1958-1982.

0 Year Catch Escapement..!./ Total Run

[] 1958 1 '114 4,000 5 '114 1960 290 146 436 D 1962 880 54 if 1 ,423 [1 1964 1 ,498 9lly 2,408 1966 2,337 1 ,442 3,779 0 1968 1 ,705 2 '161 3,866 1970 418 153 570 0 1972 68 59 126 0 1974 414 58~ 999 1976 740 86:,?:./ 1 ,603 0 1978 4,348 9,38~ 13 '735 1980 2,203 2,785 4,988 0 1982 1 ,28~ 1,657 2,943 u Mean 1 ,331 1 ,899 3,230

] .lf Tower enumeration on Nuyakuk system began in 1960; 1958 escapement was estimated by aerial survey means to be ] from 2.5 to 4.0 mill ion plus. 2/ Includes aerial survey estimates of the Wood River drain­ . age, Igushik River and Snake River systems, as well as estimated escapement in the Nushagak-Nuyakuk system below u the counting tower. [] 3/ Preliminary.

] 3 J n Table 2. Escapement and return of pink salmon to Nushagak ] district, Bristol Bay, by brood year, 1958~1982.

n Brood Year Esca[!ement Return Return/S[!awner . 1958 4,000 436 0.11 [J 60 146 1 ,423 9.75 62 543 2,408 4.43 64 911 3,779 4. 15 [] 66 1 ,442 3,866 2.68 1968 2 '161 570 0.26 70 153 126 0.82 D 72 59 999 16.93 74 586 1 ,603 2.74 ~] 76 863 13,735 15.92 1978 9,386 4,988 0.54 80 2,785 1 ,286 0.46 [} 82 1 ,657

J Mean 1 ,899 2,935 4.90 [] Table 3. Pre-season forecast and actual return of pink salmon to Nushagak district, Bristol Bay, by 0 year, 1966-1982.

Pre-Season Actual Percent D Year Forecast Return Run/Forecast 1966 2,300 3,779 164% ] 68 4,500 3,866 86% 70 2,500 570 23% 72 1 ,400 126 9% ~] 74 307 999 325% 1976 3,047 1 ,603 53% 78 3,193 13 ,735 430% [] 80 15,700 4,988 32% .; l 82 9,200 2,943 32% <. •. J

..:]

] i ': 4 I I J i ! ' L] problem stems from a nearly total lack of knowledge concerning pink salmon in this area. Prior to 1981, no biological studies had ever been conducted 0 on pink salmon in Bristol Bay. In 1980 the Alaska Legislature appropriated $31,500 to begin investigating means of improving both pre-season and in-season pink salmon forecasts. Studies u were initiated in the spring of 1981 on the Nushagak River to evaluate production from the 1980 pink salmon escapement. Specific objectives of these studies 0 were designed to provide information on emigrating pink salmon fry· in the r] Nushagak River. They were as follows: '-· 1. Develop and evaluate various methods of capturing and sampling migrating pink salmon fry in the Nushagak River. D 2. Describe the spatial and temporal distribution and relative abundance of pink salmon fry at a selected site in the Nushagak River during the spring emigration. ,_:} 3. Investigate the potential for developing a pink salmon fry abundance index program. D ,4. Document biological characteristics of migrating pink salmon fry as well as other juvenile salmonids present in the sample catches.

0 5. t~onitor associated environmental parameters during the outmigration period. [] 6. Monitor adult pink salmon returns.on even numbered years to.the Nushagak River to interpret and evaluate indices of fry abundance. u MATERIALS AND METHODS l Sampling Site The sampling site was that section of the Nushagak River approximately 4 km (2.5 miles) below Portage Creek (Figure l). The area was selected not only as a suitable location for sampling pink fry, but is also the site.where the adult salmon sonar enumeration project is located. This is the only location in the lower Nushagak where the river is entirely contained in one

~J channel. The site is within the upper limit of tidal influence, and

5 :J J D experiences some tidal depth and velocity fluctuation. The intensity of the tidal influence varies with prevailing discharge conditions.which can change 0 significantly due to the physical nature of the Nushagak River. During the months of May and June, when the fry are emigrating, water levels are low, 0 but steadily rising. [J The width of the river at the sampling site was measured during winter months by fiberglass tape and found to be 241 m (790ft.). During the month 0 of May surface measurements were also made at various points across the river, including points corresponding to the actual sampling stations. Mean velocities fJ ranged from a low of 1.4 feet per second (fps) to a high of 4.81 fps. An [] approximate profile incorporating these data is shown in Figure 2. Monthly mean river discharge rates have been measured on.the Nushagak 0 River at Ekwok by USGS for the years 1954-76. Although this data does not reflect water velocities at the sampling site, it does indicate.the range of D hydrological conditions that exists in the main river drainage. Discharge 0 rates (in cubic feet per second) have ranged fr.om 87,100 to 6,000 since observations have first been recorded. Discharge records for 1981 are [] summarized in Table 4.

[] Sampling Techniques J An inclined plane trap, similar to one developed by F.-R.I. (Univ. of Washington) for use on the Newhalen River, was selected as.the primary [] capture gear (Figure 3). Because the trap is only designed to sample the top .8 m (24 inches) of the water column, a second trap was built to sample 0 vertical strata within the water column (Figure 4). The vertical sampler, ·. i] consisting of two sock-type nets, was patterned after equipment developed L. for use on the Fraser River by the Department of Fisheries of Canada (Todd, ] 1966). One net captured fry migrating at the surface while the position of

] 6 J Table 4. SOrT~WES! ALASKA !} 15302500 NUSRAGAf R!VER A~ EKWOK L. (Na~ional stream-quality &ccounting network station)

LOCATION.--l.at 59.20'57", long 157.28'23", in SE~SE);; aec.35, 1.9 5., k.4S W., Hydrologic Unit 19040002, on right bank at Ekwok, 0.6 mi {1.0 km) upstream from Klutuk Creek, and 40 ud (64 km) northeaat of Dillingham. 0 DRAINAGE AREA.--9,850 mi' (25,500 km'), approximaoely. WATER-DISCHARGE RECORDS [] PERIOD OF RECORD.--October 1977 to current year. GAGE.--Nonreeording gage. Altitude of gage is 90ft (27m), from topographic map. Prior to Apr. 17, 1979, at site 0.4 ~ (0.6 km) downstream at different datum. REMARKS.--Water-discharge recorda good except thoae for period of no gage-height record, Nov. 1 to Apr. 26, which 0 are poor. EXTREMES FOR PERIOD OF RECORD.~-M&ximum discharge, 87,100 ft'/a (2,470, m'/s) Oct. 12, 1977, gage height, 1D.64 ft (3.243 m), site and datum then in uae; maximu: gage height, 14.46 ft (4.407 m), siee and datum then in uae, in April 1979, from floodoarka, backwater from ice; minimum daily discharge, about 6,000 ft'/s (170 m'/a) 0 Mar. l to 12, 1979. EXTREMES FOR CURRENT YEAR.--Maximum discharge, 52,600 ft'/& (1,490 m'l•) May 12, gage height, 9.61 ft (2.930 m); minimum daily, about 7,200 ft'l• (204 m'/a) Dee. 26-31. '''.· '] l.'

DISCHARGE, IN CUBIC FEET PER SECOND, WATER YEAR OCTOBER 1980 TO SEPTEMBER 1981 MEAN VALUES

D DAY OCT NOV DEC JAN FEB I'.AR APR MAY JUN JUL AUG SEP 1 27900 27000 11000 7400 7800 10000 11000 37900 38800 30300 27200 26300 2 27400 27000 11000 7400 7800 10000 11000 39SOO 35300 29900 27000 25900 3 27000 25000 11000 7400 7800 10000 11000 40400 38200 29300 27800 25900 0 4 26800 25000 10000 7400 7800 10000 11000 40600 38100 28600 28900 25700 5 26400 25000 10000 7400 7800 10000 11000 43600 38000 27800 29000 26000 6 25700 24000 10000 7600 8200 11000 12000 44000 37700 27000 28300 26800 7 25500 24000 9400 7600 8200 11000 12000 44200 37400 26400 27400 26300 0 8 25100 23000 9400 7600 8200 11000 12000 47500 38100 25700 27300 25900 9 24500 22000 9400 7600 8200 12000 12000 48600 39200 25300 27800 25300 10 23700 20000 8600 7800 8200 12000 12000 50500 41000 26400 29300 24800 11 22900 20000 8600 7800 8600 12000 14000 51300 46300 28000 30300 24700 0 12 22600 19000 8600 7800 5600 12000 14000 52~00 51300 29400 32600 24800 13 22500 19000 8600 7800 8600 12000 16000 51900 47900 302'00 37500 24400 14 23200 17000 8600 7800 8600 12000 16000 50500 44200 30600 37600 24200 15 28000 17000 8600 7800 8600 12000 18000 4&800 42100 32700 35400 23900 0 16 36800 17000 8200 7600 9000 12000 18000 47600 40300 36500 33900 23800 17 :nooo 16000 8200 7600 9000 12000 21000 47400 38800 38800 32800 23900 18 32300 16000 8200 7600 9000 12000 21000 46600 39000 37600 31900 24200 19 30500 15000 8200 7600 9000 12000 24000 46200 37200 36000 31100 23500 0 20 31000 '15000 8200 .7600 9000 12000 24000 47100 36800 35700 31200 22600 21 32400 14000 7400 7600 '9200 22000 27000 50100 36300 35300 30300 22000 22 33200; 14000 7400. 7600 9200 12000 27000 51300 35300 33900 29000 21500 23 33100 13000 7400 7600 9200 ;zooo 30000 51800 34400 29100 28100 21200 24 35500 13000 7400 7600 9200 12000 30000 47400 33600 30700 27600 21000 ] 25 38700 12000 7400 7600 9200 12000 34000 41800 32700 30100 28700 21000' 26 41500 12000 7200 7600 9600 1!000 34000 39200 3:800 29500 32900 21000 27 39000 12000 7200 7600 9600 11000 36200 38600 31400 29400 33600 20900 28 35100 11000 7200 7600 10000 11000 36600 38000 31100 29000 30600 20600 29 32400 11000 '7200 7600 11000 36500 39000 30800 28600 28600 20100 30 31000 11000 7200 7600 11000 36400 43600 30600 28100 27700 20000 31 27900 7200 7600 11000 43200 27700 26900 .TOTAL 926600 536000 264000' 235800 243200 353000 628700 1411000 1136700 943600 938300 708200 MEAN 29890 17870 8516 ' 7606 8686 1!390 20960 45520 37890 30440 30270 23610 MAX 41500 27000 11000 7800 10000 12000 36600 52500 5:300 38800 37600 26800 tuN 22500 11000 7200 7400 7800 10000 11000 37900 30600 25300 26900 20000 CFSM 3.04 l. 81 .87 .77 .88 1.16 2':13 4.62 3.85 3. 09 3.07 2.40 IN. 3.50 2.02 1.00 . 89 .92 l. 33 2.37 5.33 4.29 3.56 3.54 2.67 AC-FT 1838000 1063000 523600 467700 482400 700200 1247000 2799000 2255000 1872000 1861000 1405000 CAL YR 1980 TOTAL 10460000 I'.EAN 28580 !'.AX 80300 !!IN 7200 CFS!'! 2.9C IN 39 .. 50 AC-FT 20750000 J lo"TR YR 1981 TOTAL 8325100 MEAll 22810 !'.AX 52500 MIN 7200 CFSH 2.32 IN 31.44 AC-FT 165:0000 7 c L__J r-- --l :-·---~ r~---, r- -~ ,---~-~ r------~ ~ L....J '----.! c:.:....J LJ L:.:::J CJ c:J '-----' [ l r -J ,______) c:...._:] LJ

Depth ---- Velocity 0 _....._ 5.0 - ...... 5 / --- ..... _____ -----...... / -- 4.0 / / -.... ~ / u / "" --

30 0 100 200 300 400 500 600 700 800 North South Bank Distance (Ft.) Bank

Figure 2. Surface velocity and depth profile at the sample site, Nushagak River, 1981. []

[1 the second net was adjustable and could be fished at any selected depth to the bottom of the river. The nets were fished simultaneously and comparison [] of catches allowed an estimate of .the proportion of fry migrating at depths. The long-range objective of the sample design was to deri.ve an estimate ilL__ of total run size, corrected for the proportion of the river strained to the total river width, and for any proportion of the population migrating at Lr] depths. Factors expected to have the greatest effect on variability of the [] individual catches were site, time of day, and date of capture. A single inclined plane trap was available for use in 1981 and was fished .at three selected locations across the river, which was assumed to represent the [] horizontal distribution in each third of the river. The season was divided into sample days which began at 0600 hours and the trap was fished for an

'J eight-hour interval at each sampling station each day as specified in a lattice-type sampling scheme. The sample day consisted of three eight-hour 0 periods: 0600-1400, 1400-2200, and 2200-0600. The trap was rotated through 11 the stations so that within a three-day period, every station was sampled u during each of the three time periods. ~] The vertical sampler was also fished for two-hour time intervals. [] However, this trap was not regularly rotated through the three sample stations as was the inclined plane trap. Instead it was positioned in each of _the J stations so as not to interfere with the sample scheme for the inclined plane trap. Three net positions were established for the movable net, [] which was capable of fishing to the bottom of the river. All three [] combinations of fixed and variable depth net settings were fished twice at each two-hour time period, at each station. At each station the traps were attached to a pair of buoyed headlines affixed to two anchors. The traps were inspected and cleaned every two hours ] 9 ] [] [] 0 fj D 0 0 [] [] ] [] ] ']

] Figure 3. Inclined-plane trap used for catching pink fry, Nushagak River, 1981. J iO lc._ ] ] ,-] L_ 0 0 ~] 0 l] 0 D lJ :] I.

[] ~J Figure 4. Vertical sampling unit constructed for sampling pink salmon r fry in the Nushagak River. '-l ] J 11 []

[} to help maintain constant fishing efficiency. At each inspection the catch was separated by species, enumerated and released. Sampling was conducted throughout the period of the fry migration and ended 21 June when fry catches had significantly declined. Samples of 10 pink and chum fry were taken from the catch for length [] and weight analysis at regular two-hour intervals. The fry were blotted dry on a paper towel, weighed with a dial-a-gram balance (mean weight), and [] individually measured with a caliper. Length and weight data, as well as ] catches by time period, were later entered into a computer data file for analysis. [] Adjustment and Expansion of Counts ] Daily catch per hour was calculated for each sampling station, extra­ polated from eight hours of sampling at a particular site each day. There were time periods when the trap could not be fished at a given site due to problems associated with high water, i.e. dragging anchors, heavy debris, etc. Missing data for those periods was supplied by linear interpolation .. The [] daily catch per hour was then summed for all sample days and multiplied by 24 [] hours to obtain a trtal estimate of fry emigrating within.that segment of.the river defined by thl! ·sample station. ! ,. ] A rough estimat~ of the numbers of fry emigrating in .those sections of . river not sampled by 'the inclined plane trap was made by expanding the total J catches at stations 1, 2, and 3 by appropriately scaled fa.ctors. These factors D were a function of l:!i'stance between the individual fishing stations with respect to the tota 1 distance across the river (Bucher, 1980). The following expansion '] factors were used: Site 1 - 67.4, Site 2 - 110.0, and Site 3 - 65.7. '] 12 ] J To derive a total outmigration estimate, an area density model was used J which can be described by the following equation:

J 49 3 N=:L:L:·cid J d=6 i =1 Where: N = total estimated fry outmigration C =catch per hour from inclined plane trap D = distance expansion factor H = 24 hours d =sample day J i = sample station

D RESULTS 0 The inclined plane trap was first fished on 4 May and fished continuously for 50 consecutive days. Actual fishing time totalled 872 hours between D 4 May until 16 June measuring the relative proportion of fry migrating at various depths below the surface. During periods of increased river discharge, D both traps required constant cleaning and adjustment due to debris in the 0 water. At times the traps fished at a reduced efficiency because of the debris load, and on a few occasions, anchors were torn loose and the traps D had to be re-installed. [] Pink Salmon J Daily catches of pink salmon fry ranged from 0 to 19,260. Figure 5 shows. the daily catch per hour of pink fry for the period 4 .May ~· 16 June. I ) u Peak catches occurred.on 12· June when the catch per .hour reached 5,822 and [] densities of fry were so great that subsampling of the two-hour periods was necessary to reduce catches to a level that would allow separation of species ] and enumeration. Expansion of catches laterally to estimate numbers of fry travelling in those sections of river not sampled produced a total outmigration ] 13 J r- ---. L...J . [___j. L::_] LJ. LJ ,--] L---.J c..=J [__:_:_] c--J c::::J [___j L.__j ,- -] [~] r·- · 1 L.J :.:.:__:] L_J '----' 2000

1660

1330

::::> 0""' :r:

LLI ""'c_ 1000 :c u 1- ~ cr: .. --~-.,. '-'

660

330

, ~ I I I 0 I I I I I I • 48 14 18 23 28 33 38 43

SAI1PLE DAYS · (l~ay 14 - June 16)

Figure 5. Daily catch per hour of pink salmon fry in the Nushagak River, 1901. l estimate of 110,065,328 pink fry. Lengths of the fry averaged 36.2 mm, while 0 the average weight was .26 g. Although some change in length and weight was

/ [] observed over the duration of the migration, the average length and weight was not weighted by periodic outmigration estimates. J Horizontal distribution of fry across the river appeared directly related to river velocity as the highest catches occurred in those sections with the D highest water velocity. The bulk of the emigrants (7g%) passed down the middle 0 section of the river, while approximately 18% travelled within 60 feet of the north bank, and only 3% passed down the 60-foot section of .river adjacent to ~ the south bank.

0 Migratory Patterns D Data .which may indicate trends in migration timing and distribution has been entered into a computer fi 1e which wi 11 a 11 ow detai 1ed ana_lys is~ D Programming is not yet completed and therefore, results from this analysis will 0 be published in a future report. D Chum Salmon ,, Daily catches of .chum salmon fry ranged from 0 - 2,237. Figure 6 S'hows J the daily catch per hour of chum fry for the period 4 May - 16 June. Peak

I! .. catches of chums occurred on 12 June when the catch per hour reached 2,237. J Although the major portion of chums appeared to migrate with.the pink fry, n significant numbers of .chum fry were caught during May 10-12. At this date only station one (near the north shore) had been established. It is -likely u that the chum catches would have been higher at station two· (in the middle of

.. ] the river) if the trap had been fishing there on t~ay 10-12 . ~.

] 15 J r------·l r c..::_] ~ c:::J -J --l L.:J c.:::.::::J r- J cu-l r ---J c- -~ c_::] :____] ~ .______; ~ r-J r- c c.:::.::::J ~

250

200

0:: :::> 0 ::t: 150 0:: WJ "- ::t: ~ u en 1- 5 100

50

4 8 13 18 23 28 33 38 43 48 SAMPLE DAYS (May 4 - June 16) Figure 6. Catch per hour of chum salmon fry in the Nushagak River, 1981. n i] The fact that the daily peak chum fry catch coincided with.the peak '- day of the pink fry migration is somewhat suspect, and may be artificial. D Subsampling of the catch, due to the large numbers of pink fry present during the peak period, may have yielded a biased estimate of the ·numbers of chums 0 actually present. [] Expanding catches by the same method used to generate a total outmigration estimate for pink fry produced a chum estimate of 12 ,823 ,2BO.. .Average 1ength and weight of the chum fry was 39.7 mm and . 46 g, respectively. 6 ··--~-. __::::~-

[] Other Species 0 Although project operati ona 1 plans ca 11 ed for documentation and study of other juvenile salmonids present in the catches, very few other species 0 were caught in the traps. They were as fo11 ows: 90 sockeye smo 1ts, 22 king salmon smolts, and four coho smolts. Lengths, weights, and scale samples 0 were co 11 ected from these fish. However, due to the 1ow catches of these 0 other species, the samples are undoubtedly a poor representation of.their respective migrations. It is possible that the majority of these smolts are 0 large enough to avoid the traps, since the optimum water velocity for operating 0 the traps was found to be less than three fps. ] DISCUSSION J The model used to estimate the total outmigration incorporates certain basic assumptions, some of which are not entirely true or correct. 0 These are a follows: ·• 1. Fry distribution throughout the river is random, i.e. those areas of river sampled by the inclined plane trap are similar to those 0 adjacent sections not sampled.

17 J n 2. Passage rate of fry during non-sampled hours (within 24-hr. period) J is similar to the passage rate during the eight hours.that.the trap is fishing at a given site, i.e. an eight-hour sampling period is representative of the 24-hr. passage rate. 0 3. River velocity fluctuations do not significantly affect the inclined plane trap's fishing efficiency. 0 4. Significant numbers of fry do not migrate beneath.the top 22 inches of the water column or avoid the trap mouth. [] It was recognized that the efficiency of both traps would be influenced by mesh size, water turbidity and velocity, fouling by detritus and floating L1 materials, and orientation in the river current. Further, Hamalainen· (1978) 0 has shown that the lattice sample method of estimation (Pella and Jaenicke, 1976; Cochran and Cox, 1957; Stober, et a 1. , 1976) does not account for di ffe.rences 0 in velocity between trap sites, and thus may over-estimate fry emigration by as much as 20 percent. J Because changes in water velocity have been shown to affect trap 0 efficiency, the two near-shore sites (having reduced flows) would be expected to produce smaller catches. Results of this study supported these expectations. 0 However, it is generally recognized that most salmon fry (and smolts) migrate D downstream near the surface and towards the center in the strongest current, (McOoanld, 1960). Therefore, changes in trap efficiency, as measured by D relative catches between stations, would be masked by the natural behavior of salmon fry to travel in the strongest current.

J Beca~se the observed velocity at stations I and III was n0t significantly u lower than the center station this season (1 fps), and sampling effort was allocated equally between stations (as opposed to sampling high density sections

,_~] more heavily), it is doubtful that the outmigration estimates would be i] substantially changed if corrections for velocity as suggested by Hamalainen '- (1978) had been incorporated.

18 J D Marine Survival ] The 1981 Nushagak pink fry emigration was estimated to be 110.1 million. The subsequent adult return (catch plus escapement) in 1982 was estimated to l1 be 2.943 million. Although these figures are still preliminary, they do allow 0 an estimate of marine survival, which was calculated to be. 2.7%. This figure compares well with survival estimates of wild pink salmon fry from Tutka Bay, f],_ in lower Cook Inlet. Where Dudiak (pers. comm.) has calculated marine 0 survival to be 6.0% to 1.7% for the years 1978-81. ,-] As in Bristol Bay, pink salmon returns in Cook Inlet exhibit an even-odd L year cycle. However, in Cook Inlet the odd year runs are dominant, while Nushagak pinks are just the opposite. Dudiak's estimates show the minimum 0 survival rates (1.7%- 2.1%) are observed on the even-year runs. He attributes J the differential survival to intraspecific predation during the months of July and August while the pink fry and returning adults are occupying the 0 same estuarine habitat. A similar theory was put forth by Barber (lg79) as well. The idea seems plausible for Nushagak pink salmon and certainly 0 warrants future study. [] Recommendations [] It has been suggested that a total fry migration estimate is unnecessary and that an index of fry abundance is all that is needed to predict adult J returns. The index would be generated by comparing catches from a single 0 site fished year after year in the same manner. However, data from this first season's study suggest that catches may be affected by changes in the fry [] migration path past the sampling sites due to wind direction, water level (tide stage) and fry abundance. Therefore, index sampling may be less J sensitive in monitoring relative pink fry outmigration abundance than random J (lattice) sampling. J 19 n ,-] It would be preferable to fish more stations across the river for.shorter :] time intervals, but the difficulty with which the trap was moved fr.om station L. to station precluded more intensive sampling. It would be more practical to [j use more traps (preferably three) that would allow additional sampling of both time and area. More than three would be very labor intensive and would L1 also interfere with boat traffic on the river. It was planned that changes in trap eff.iciency due to changes in water 0 velocity would be compensated by monitoring water velocity and statistically ] adjusting the catches (Hamalainen, 1978). Due to equipment failure, insufficient velocity data were gathered to properly monitor and adjust the [] catch data. Future studies should incorporate adequate means for collecting velocity data on a periodic or continual basis. 0 It appears that this project has potential to be a successful program for estimating pink salmon fry production. Once an accurate determination 0 of the adult returns (catch plus escapement) has been made, marine survival 0 can be calculated which will be used to interpret and evaluate the fry abundance estimate. Knowing the approximate number of pink salmon fry that 0 go to sea, and the percentage of fry that survive to return as adults should '] allow more accurate forecasts in future years. ] J i] ]

~1 20 ] J [] LITERATURE CITED [] Barber, F. G. 1979. Disparity of pink salmon runs, a speculation. i} Fish. Mar. Serv. ~1S Rep. 1504 : iv + 7 p. · L. Bucher, W. A. 1980. 1979 Wood River smolt studies. In 1979 Bristol Bay sockeye salmon smolt studies. (Ed. C. P. Meacham). [] Alaska Department of Fish and Game, Technical Data Report No. 46, pp. 12-33. . Cochran, W. G. and G. M. Cox 1957. Experimental designs, 2nd ed. John 0 Wiley & Sons, Inc., New York, 611 pp. · Hamalainen, A. H. 1978. Effects of instream flow levels on sockeye salmon [] fry production in the Cedar River, Washington. M. S. Thesis, Univ. of Washington. · McDonald, J. 1960. The behavior of Pacific salmon fry during their down­ 0 stream migration to freshwater and salt water nursery areas. J. Fish. i] Res. Board Can. 17 (5): 655-676. l_ Pella,·J. J. and H. W. Jaenicke 1976. Some observations on the biology and variations of populations of sockeye salmon of the Naknek and Ugashik systems of Bristol Bay, Alaska, 1956-1962. Unpubl. MS., 0 Northwest Fisheries Center, Auke Bay Fisheries Laboratory, National ~1arine Fisheries Service, NOAA. ·

Stober, Q. J., R. E. Narita, A. H. Hamalainen, and S. L. Marshall 1976. 0 Preliminary analysis of the effects of 1nstream flow level on the reproductive efficiency of Cedar River sockeye salmon. Annual Progress Report. FRI - UW - 7619. Todd, I. S. 1966. A technique for the enumeration of chum salmon fry in 0 the Fraser River, British Columbia. Can. Fish. Cult. 38 : 3-35. ]

[]

J 21 :] '· n n [] 0 0 APPENDIX D J 0 J J 0 0 J D 0 [] [] ] ] J

Table 1. Pink salmon fry catches per hour in the inclined plane J trap, by day and site, Nushagak Riyer, l98l.l/

11,_ Mean Catch Date Site I Site II Site III Per Hour [] 5/ 4 .2 (.2) (. 2) .2 5 .2 ( . 2) ( . 2) .2 6 .9 (.9) ( . 9) . 9 7 0 8 .4 ( .4) (. 4) .4 5/ 9 .8 (. 8) (. 8) .8 D 10 5.6 (5.6) (5.6) 5.6 11 5.2 (5.2) (5.2) 5.2 12 3.7 (3. 7) (3. 7) 3.7 J 13 6.0 (6.0) (6.0) 6.0 5/14 2.7 5.8 (5.8) 4.8 15 (2.3) . . (22.3) 12.5 12.4 0 16 (2.3) (22.3) 14.0 12.9 17 1.8 38.7 6.9 15.8 J 18 (9.4) (47.8) 16.4 24.5 5/19 17.0 56.9 21.7 31.9 20 (28.6) 71.7 24.3 41.5 21 40.1 74.1 32.4 48.9 J 22 51.2 169.5 (27.6) 82.8 23 (48.9) ( 143. 1 ) (27.6) 73.2 0 5/24 46.6 116.7 22.7 62.0 25 14.7 49.2 3.2 22.4 26 32.8 78.2 8.1 39.7 0 27 18.7* (.153.3) 7.7 59.9 28 (46.0) 228.4 13. 1* 95.8 J 5/29 73.2 290.7* . (38.8) 134.2 30 49.4* (308.0) 64.5 378.9 31 47.2 . 325.2 13.0 128.5 ] 6/ 1 96.6 640.1 57.6 264.8 2 . 106.7 755.9 305.4 389.3 6/ 3 12.7 .1 772.5 50.0 316.5 ~] 4- 1 ,517 .6 1,171.7 94.2 927.8 5 74.1 .· 1 ,182. 1 . 139.2 465.1 6 263.4 (1 ;356.3) (130. 1 ) 583.3 [] 7 620;9 1,530.5 121.0 757.5

·_ i l · (continued) ~-

J 22 J !] '-

:J Table 1. (continued)

] Mean Catch Date Site I Site II Site III Per Hour ] 6/ 8 145.0 830.8 4.5 326.8 9 878.6 1 ,494.3 43.6 805.5 10 166.0 2,314.1 108.8 863.0 11 194.6 4,702.3 77.7 1,658.2 LJ 12 5,821.8 2,475.0 20.1 2,772.3 6/13 319.3 5,276.9 363.8 1,986.7 D 14 747.6 (2,716.0) 49.0* l ,170.9 15 646.9* (2,716.0) (24. 7) l ,129.2 16 136.3 . 155.1 0.3 97.2 J 17 37.2 29.1 59.1 41.8 0 6/18 51.0 469.6 4.9 175.2 Total 32-,812.0 J 12,50£.0 2,037.0 lJ Based on extrapolation from eight hours of sampling at each site J for each day. Numbers in parentheses are interpolated. Numbers marked with an asterisk are an average of two eight-hour periods. 0 ] J [] 0 J ~] ] 23 :J n Table 2. Chum salmon fry catches per hour in the incl1?ed plane [J trap, by day and site, Nushagak River, 1981.-

] Mean Catch Date Site I Site II Site III Per Hour 5/ 4 0 0 0 0 D 5 0 0 0 0 6 .4 (. 4) (. 4) .4 ] 7 (4.4) (4.4) (4.4) 4.4 8 8.4 (8.4) (8.4) 8.4 5/ 9 7.3 (7.3) (7.3) 7.3 0 10 39.8 (39.8) (39.8) 39.8 11 102.1 (1 02.1) . ( 102 .1) 102. l 12 41.2 (41.2) (41.2) 41.2 ] 13 26.9 (26.9) (26.9) 26.9 5/14 9.3 (9.3) 23.0 13.9 15 (7.6) (7.6) 18.7 11.3 D 16 (7.6) (7.6) 21.0 12.1 17 5.9 20.0 12.6 12.8 J 18 8.8 22.5 15.7 15.7 5/19 10.8 22.5 10.5 14.6 20 1.8 15.8 14.6 10.7 0 21 5.5 19.5 14.7 13.2 22 16.3 17.4 (8.9) 14.2 D 23 (12.9) (17.0) (8.9) 12.9 5/24 9.4 16.6 3.0 9.7 25 3.0 8.5 1.4 4.3 ill __ , 26 1.4 1.5 . 0.9 1.3 27 0.7* (2. 0) 0.3 1.0 28 ( • 6) 2 .5, 0.5* 1.2 D 5/29 .5 2.51 . (0. 7) 1.2 30 1.0 (2.5il* 0.9 1.5 31 1.8* 2.5 ' '1.0 1.8 CJ 6/ 1 .9 9.1. 0 3.3 2 1.5 5. 9i 3.6 3.7 ! 0 6/ 3- 0.6 12.3 ' 0.3 4.4- 4 4.0 3.7 2.5 3.4 5 2.8 2. 7i 2.5 2.7 [j 6 0.4 (4.9) (2. 7) 2.7 7 .9 7.0 2.8 3.6 [] (continued) J 24 J J J Table 2. (continued)

Mean Catch J Date Site I Site II Site III Per Hour 6/ 8 5.2 5.8 0.3 3.8 [] 9 14.7 97.4 1.9 38.0 10 3.9 135.9 24.8 54.9 11 113.0 205.7 9.5 109. 4. D 12 688.3 1,275.0 10.6 658.0 6/13 65.5 734.6 59.5 286.5 14 45.9 (371.5) 9.3* 142.2 0 15 37.2* (371.5) 4.7 137.8 16 9.1 8.4 0 5.8 0 17 0.5 0.3 4.3 1.7 6/18 1.5 47.4 0.1 16.3 D Total 1,331.0 3,727. 0 527.0 J

'1 J l/ Based on extrapolation from eight hours of sampling at each site for each day. Numbers in parentheses are interpolated or extrapolated from catches made at a different site due to high water. Numbers marked with an asterisk are an average of two 0. eight-hour periods. D J

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