Pacific Stock Assessment Review Committee Not Citable Stock Status of Stikine Sockeye C.C. Wood1 and R.A.C. Johnston2 April 2, 1

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Pacific Stock Assessment PSARC Working Review Committee Paper S90-7

stock status of stikine Sockeye

c.c. Wood1 and R.A.C. Johnston2

April 2, 1990

1 Department of Fisheries and Oceans Biological Sciences Branch Pacific Biological Station Nanaimo, B.C. V9R 5K6

2 Department of Fisheries and Oceans 122 Industrial Road Whitehorse, Yukon YlA 2T9

Not Citable .. "! f ..

2 Table of contents

List of Figures 3 List of Tables 4

Abstract 5

1.0 Introduction ...... 7 1.1 Description of Watershed •••••••• 7 1.2 Fish Resources and Utilization 8 1.3 Sockeye Management 10 1.4 Sockeye Enhancement 11 2.0 Methods and Data Sources •••••••••••• 11 2.1 Stock Definitions ••••••• 11 2.2 Escapement Data ••••••• •••••• 12 2.3 Total Run into Canada (Border Escapement) 12 2.4 Catches in Alaska •••••••.•••..••••••• 13 2.5 Stock-Recruitment Analysis •••••••••••••• 13 2.6 Assessment of Juvenile Production in Tahltan Lake 15 3.0 Productivity Evaluations 16 3.1 Tahltan stock •••••••• 16 3.2 Non-Tahltan stock 19 4.0 Pre-season Sockeye Forecasts •••••••••••••••• 19 4.1 Forecasts bf the TCTR ••••••••••••••••••• 19 4.2 Stock-Recruitment Method •••••••••• 20 4.3 Sibling Method ••••••••••••••• 20 4.4 Forecasts for 1990 and 1991 •••••• 21 5.0 Stock Status 23 6.0 Data and Information Needs 24 7.0 Recommendations 26

8.0 Literature cited 27 Tables 30 Figures ...... 37 Appendices ...... 51 1. Salmon catch in the Canadian food fishery •••.••••• 51 2. Salmon catch and effort in the Canadian commercial fishery in the lower Stikine River •••••••.•••.•• 52 3. Salmon catch and effort in the Canadian commercial fishery in the upper Stikine River •••••••••••••. 53 4. Salmon catch and effort in the Alaskan District 108 54 5. Salmon catch and effort in the Alaskan Subdistrict 106-41 and -42 (Sumner Strait) ••••••••••••••.••• 55 6. Salmon catch and effort in the Alaskan Subdistrict 106-30 (Clarence Strait) ...... 56 3

List of Figures Figure 1. Map of the Stikine River and U.S. fishing districts off the mouth of the river 2. Tahltan sockeye escapements 3. Non-Tahltan sockeye escapements 4. Tahltan stock-recruitment analysis 5. Estimated egg-to-smelt (and presmolt fry) survival in Tahltan Lake 6. Tahltan Lake stock-recruitment relationship, 1975-1983 7. Tahltan Lake stock-recruitment relationship, 1959-1983 8. Optimal escapements for Tahltan sockeye 9. Sockeye presmolt production in Tahltan Lake versus escapement 10. Relationship between sockeye smelt size, presmolt fry density, and fertilization in Tahltan Lake 11. Calculated harvest rates on Tahltan sockeye based on estimates of presmolt fry production from equation [5] 12. Non-Tahltan stock-recruitment relationship, 1975-1983 13. Sibling forecast method for Tahltan sockeye 14. Trends in Tahltan sockeye smelt survival 4

List of Tables Table 1. Estimated catches of Stikine sockeye in Alaska, 1979-1989 2. Escapement and returns to Tahltan Lake by aqe and brood year 3 • Escapement and returns for the non-Tahl tan stock by aqe and brood year 4. Tahltan Lake smelt counts and reconstructed presmolt data by brood year 5. Summary of sockeye smolt size in Tahltan Lake relative to abundance and enrichment history 5

Abstract

Sockeye salmon in the stikine River are harvested by both Canada and the United States, and managed and enhanced according to recommendations from the joint Transboundary River Technical Committee (TCTR) of the Pacific Salmon Commission. Two stocks are defined based on practical aspects of their management: the Tahltan Lake stock, and a conglomerate of runs to other parts of the drianage referred to as the "non-Tahltan stock". Spawning escapements to Tahltan Lake are known from weir counts since 1959; those to the non-Tahltan stock have been estimated indirectly using a test fishery, but only since 1979. Catch and age data (and hence total return data by brood year) are available from 1979-1989; before 1979, there was no Canadian commercial fishery, and Alaskan catches of Stikine sockeye were not estimated. Much of the Alaskan catch of Stikine sockeye is incidental to other fisheries, and therefore difficult to estimate reliably. Smelt production in Tahltan Lake has been monitored carefully since 1984. Sockeye fry reared in an Alaskan hatchery from Tahltan broodstock are scheduled to be planted back into Tahltan Lake in 1990 in an effort to increase sockeye production from the Stikine. Stock-recruitment analyses with total return data acquired since 1979 suggest that optimal escapements for the Tahltan and non-Tahltan stocks are 15,000 and 20,000 spawners, respectively. A similar analysis based on Tahltan escapement data from 1959-1989 excluding catch but with an assumed historic exploitation rate of 0.3-0.5 suggests an optimal escapement range of 15,000-20,000. stock-recruitment analyses using presmolt production data from the 1982-1987 brood years assuming presmolt-to-adult survival rates of 0.02-0.05 suggest an optimal escapement range of 14,000-22,000. Thus, the recommended escapement goal for the Tahl tan stock is 20,000 spawners, at the low end of the target range (20,000-40,000) set by the TCTR. Forecasts of Stikine sockeye returns have been very unreliable. The sibling age class method using age 4 returns to predict combined ages 4-6 returns in the following year appears to have merit for the Tahltan stock. The sibling method has been used to develop a "best" Tahltan forecast for 1990; stock-recruitment curves have been used to forecast Tahltan returns in 1991 and non Tahltan in 1990 and 1991. The "best" 1990 forecasts are 30,200, 66,100, and 96,300 sockeye for the Tahltan, non-Tahltan, and total Stikine runs, respectively; the best 1991 forecasts are 33,100, 60,200, and 93,300, respectively. The total sockeye return to the Stikine River in 1989 was 95,718, slightly above the 1979-1988 average of 91,839 sockeye. Although run sizes have fluctuated since 1979, there is no evidence 6 of a trend in overall stikine sockeye abundance. However, the return to the Tahltan stock in 1989 was only 14,111, well below the 1979-1988 average of 29, 149; Tahltan returns have been below average since 1987. In contrast, the non-Tahltan return in 1989 was 81,607 and above the 1979-1988 average of 62,690. Sockeye escapements to Tahltan Lake have been below the target range set by the TCTR (20,000-40,000), and the estimated optimal levels reported here (15,000-20,000) since 1987, ranging from 2,536-8,316. The non-Tahltan escapement in 1989 was within the target range (20,000-40,000) and slightly above the optimal level reported here (20,000); non-Tahltan escapements in 1987 and 1988 were very close (19,353 and 22,840, respectively) to the estimated optimum. Sockeye returns to the Tahltan and non-Tahltan stocks tend to be correlated. However, the non-Tahtlan stock has been relatively more productive in recent years. The poor returns of Tahl tan sockeye since 1987 clearly result from poor survival after smolts have left Tahltan Lake; age 1+ smolt survival has ranged from only 1.1-6.9%. Poor Tahltan smolt survival appears to coincide with the initiation of the smolt enumeration program. However, estimates of smolt survival prior to smolt enumeration (based on calculated smolt production), together with empirical observations regarding the survival of smolts held in cages after enumeration, suggests that the smolt enumeration program is not responsible for recent poor rates of returns. If this is true, and conditions for smolt survival have since improved, Tahltan returns in 1990 and 1991 should be considerably greater than forecasted, because the 1985- 1986 brood years produced record numbers of smolts. f. ' .

7 1.0 Intro4uction 1.1 Description of watershed The Stikine River originates in the Stikine Plateau and Skeena and cassiar mountain ranges of northwestern British Columbia and drains an area of approximately 51,200 km2• It flows for about 640 km passing through the Coastal Mountains before reaching the Pacific Ocean near Wrangell, Alaska. Roughly 98% of the drainage area is located within Canada. The Stikine River is the largest of the northern transboundary rivers which drain from Canada through Southeast Alaska to the Pacific Ocean; the others include the Taku, Alsek, Unuk, Whiting, Chilkat, and Chickamin rivers. The mean annual flow recorded near the mouth of the Stikine is about 1, 600 m3(sec and mean daily maxima have been recorded in excess of 8,400 m /sec, reflecting the dynamic flow regime of the Stikine (Rice 1986). Owing to numerous hydraulic velocity barriers such as the Grand Canyon of the Stikine, located upstream from Telegraph Creek, and Forrest Kerr canyon on the Iskut River, the largest tributary of the Stikine, less than one quarter of the drainage basin is accessible to anadromous fish. Consequently, many of the clear, headwater lakes and tributaries do not currently produce salmon. The accessible portions of the drainage are generally characterized by braided channels and glacially-occluded waters originating from the numerous alpine glaciers of the Coastal Range. A notable exception to this is Tahltan Lake. The drainage basin is sparsely populated. Original inhabitants included Tahltan, Tlingit, and Casca Indians who hunted, fished and trapped throughout the drain~ge (Alaska Geographic 1979). The Tahltan Tribal Council is now the predominate Indian organization in the drainage and represents about 3,500 members. Non-native inhabitants have been in the area for close to a century and were originally attracted to the Stikine by trapping and mining. The Stikine was once an important transportation route for the Klondike gold rush. Most of the human population in the basin is now located in the communities of Telegraph Creek, Dease Lake, Iskut, and Eddontenajon which have a combined population of approximately 825 residents (RCMP, Dease Lake, B.C., pers. comm.). Despite the limited population, the potential for disruption of fish habitat is high due to the enormous potential for development in the hydroelectric, mining and forestry industries, as well as lineal developments to support these sectors. During the last decade, precious metal mines have developed along the Iskut River (Johnny Mountain and snip projects) and in the Chutine drainage; B.C. Hydro has been actively examining the hydroelectric potential of the Stikine; and, logging companies have operated sporadically along the lower portions of the river. Roads have 8 been pushed down the Iskut, into the Chutine drainage, and across the Tahltan rivers to create access to mineral deposits. An extended transportation corridor into the lower Stikine valley and Alaska has also been proposed. In addition, the feasibility of extending electrical transmission lines from Bradfield Canal in Southeast Alaska through the Craig River valley to provide power to mining properties along the Iskut River is being examined.

1.2 Pish Resources and Utilization All five species of Pacific salmon and steelhead trout are produced in the Stikine River. Estimates of total annual production from the Canadian portion of the drainage have averaged approximately 119,200 sockeye, 78,700 coho, 22,100 chinook, 14,200 pink, and 5,500 chum salmon over the period from 1980-1988. The distribution of these species within the watershed has been documented by the Department of Fisheries of Canada (1965); Edgington and Lynch ( 1984) ; Hawthorn et al." ( 1984) ; Northern Natural Resources Services Ltd. (1979); Northwest Enhancement Society (1985) ; and Savoie (1975) • Besides Pacific salmon and steelhead, 18 other fish species have been identified within the Stikine drainage (Rice 1986). There are three gillnet fisheries in the Canadian portion of the Stikine River that harvest salmon and steelhead: an Indian food fishery and two commercial fisheries. Stikine salmon are also harvested by Alaskan fisheries.

Indian Pood Pisherv: The Indian food fishery is centred around the community of Telegraph Creek with fishing sites generally located in the Stikine River upstream of the Chutine River and in the mouth of the Tahltan River (Fig. 1). The most common method of capture is with gillnets set from shore with gin-poles or booms. In some years, gaffing also occurs, particularly in the Tahltan River. Catches from 1985-1989 have averaged 3,802 sockeye, 1,283 chinook (including 233 jacks), 4 coho, 7 pink, 5 chum and 3 steelhead (Appendix 1). The fishery is generally open seven days per week and usually involves 50 to 70 participants over the season, although the average number fishing each week is only about one quarter of this number. Catches are recorded daily by a resident patrolman at Telegraph Creek. The sockeye catch is currently eaten fresh, home-canned, frozen or smoke-dried. Prior to 1972, catch data were not recorded regularly, although Richardson and Johnston (1966), reported that approximately 8,000 sockeye were taken annually during the 1940 1 s. Catches apparently declined throughout the 1950 1 s and 1960 1 s owing to poorer returns and decreased demand for dog food (Rice 1986).

,,,,.. Lower Stikine Commercial Pishery: The largest fishery in the drainage occurs in the lower stikine Riv~+ i.p an areq ¥hi~ ~~tends 9 from the Canada - U.S. border upstream to the confluence of the Stikine and Porcupine rivers and includes the lower 5 km of the Iskut River (Fiq. 1) • The feasibility of commercial fishinq in the lower Stikine was first examined in 1965 by the federal Department of Fisheries; it was concluded that a commercial venture would not be prosperous due to small stock sizes, difficult fishing conditions, and remoteness from markets (Crouter and Todd 1965). Despite these conclusions, a commercial fishery was initiated in 1979 to stimulate economic development and raise the profile of the stikine River in the Canada - u.s. Pacific salmon negotiations. The lower Stikine commercial catch over the most recent five year period has averaged 1,114 chinook (including 211 jacks), 13,117 sockeye, 3,676 coho, 863 pink, and 533 chum salmon, and 205 steelhead (Appendix 2) • The overall wholesale value of this harvest is estimated to be approximately $370,000.00 based on prices described in Masse (1988). Sockeye accounts for about 60% of the total value of the catch. From the inception of the fishery, the number of licenses has been restricted (in 1989 a total of 20 licenses were issued), and, on averaqe, 13 fishermen have participated in the weekly fishing periods. The fishery employs the use of both set and drift qillnets with the latter method becoming more siqnificant in recent years. There are three competinq groups involved in buying and processing fish on the river: the Great Glacier Salmon Coop., the Tahltan Tribal council and the "independents".

Upper Stikine commercial Fishery: A small commercial fishery has existed in the upper Stikine River in the vicinity of Teleqraph Creek since 1975. The fishery was initiated at the request of local residents to serve local markets in the communities of Telegraph Creek, Dease Lake, Cassiar and Watson Lake where the fish are sold fresh or frozen. Catches over the past five years have averaged 648 sockeye, 132 chinook (including 31 jacks), and 4 chum salmon (Appendix 3). Since 1979, the number of licenses in this fishery has been restricted to a maximum of five, althouqh on average, only three fishermen participate. The catch is taken by set qillnets and the fishery is usually open for one, 24-h fishing period each week. u. s. Fisheries: Stikine salmon are caught in Alaskan drift qillnet fisheries located adjacent to the mouth of the Stikine River in District 108, and in the Sumner Strait and Clarence Strait portions of District 106 (Fig. 1). The average catch in District 108 in the past five years was 157 chinook, 3,639 sockeye, 2,931 coho, 8,268 pink and 3,051 chum salmon (Appendix 4). Fishinq effort in the District 108 fishery has declined significantly in the last decade. For example, the average effort for the 1970-1979 period was 796 boat-days, whereas, the average for the 1980-1989 period was 194 boat-days. The reduced effort has resulted in the averaqe annual 10 sockeye catch declining from about 17,700 from 1970-1979 to just under 5,000 sockeye from 1980-1989. catches in Sumner Strait have averaged 489 chinook, 100,345 sockeye, 46,956 coho, 194,145 pink, and 40,456 chum from 1985-1989 (Appendix 5). Sockeye catches, which comprise numerous stocks, have increased dramatically over the past two decades in this sub district. The average annual catch from 1970-1979 was 34, 983 sockeye, whereas, the average from 1980-1989 was 85,935 sockeye. The sockeye catch in Clarence Strait has shown a similar trend, increasing from an average of 19,922 sockeye from 1970-1979, to an average of 59, 740 sockeye from 1980-1989. Additional historic catch data for Clarence Strait appear in Appendix 6. Increases in the District 106 sockeye catch (Sumner and Clarence straits) can probably be attributed to increased production from other important sockeye systems such as McDonald Lake in Southeast Alaska, and the Skeena River in B.C. Interceptions of Stikine stocks probably also occur in other Alaskan gillnet fishing districts (e.g. District 104 and 101), and Alaskan troll, seine and recreational fisheries. The Canada-u.s. joint northern tagging study in 1982 indicated the potential for interception of Stikine sockeye in fisheries adj a cent to Noyes Island and Cape Fox (Gazey and Birdsall 1984).

1.3 Sockeye Management The management of Stikine sockeye is governed by the Pacific Salmon Commission (PSC); harvest and management objectives are specified in Annex IV, Chapter 1, of the Pacific Salmon Treaty. In-season management and stock assessment procedures, and specific objectives with respect to escapement goals have been documented annually in management plans developed by the joint Canada-u.s. TransboundaryRiver Technical Committee (TCTR) (PSC 1988a, 1989a). The current management process includes the formulation of a pre-season forecast and in-season run forecasts based on historic run size and catch per unit of effort (CPUE) data during the fishery, combined with run timing and stock identification information from Canadian and u. s. fisheries. The model is updated annually and described in detail in the annual management plans (PSC 1988a, 1989a). Biological programs which support the management of stikine sockeye include: test fisheries, which are located in Alaskan districts 108 and 106, and in the lower Stikine River in Canada; sampling for stock, age, size and sex composition data in commercial and test fishery catches from districts 108 and 106, and the Canadian lower Stikine fishery; weir counts and biological sampling of sockeye escapements to Tahltan Lake; aerial surveys of index spawning areas throughout the Stikine and Iskut drainages; 11 and, enumeration of smelt emigrations from Tahltan Lake. Results from these programs are summarized annually by the TCTR (PSC 1988b, 1989b).

1.4 Sockeye Bnhancement With the re-negotiation of Stikine harvest sharing provisions of the Pacific Salmon Treaty in 1989, Canada and the U.S. agreed to embark on a joint sockeye enhancement program in the Stikine River commencing in 1989 with a production target of 100,000 adults. The project requires the capture of broodstock at Tahltan Lake, transportation of fertilized eggs by floatplane to a central incubation facility located in Port Snettisham, Alaska, and the release of newly-emerged fry back into Tahltan Lake. Consideration is also being given to planting Tahltan fry into Tuya Lake, a large, clear headwater lake in the Stikine drainage, currently without anadromous salmon, but with the rearing potential to produce an estimated 764,000 adult sockeye; by comparison, Tahltan Lake has the rearing potential to produce only an estimated 126,000 adults (PSC 1988c). The first egg-take at Tahltan Lake occurred in 1989; approximately three million eggs are being incubated at the Port Snettisham hatchery at the time of writing.

2.0 Methods and Data sources 2.1 stock Definitions Two stock components are recognized for the purpose of management: the Tahltan Lake stock which spawns in Tahltan Lake, and the non-Tahltan component which is a conglomerate of stocks that spawn elsewhere throughout the drainage. The Tahltan Lake sockeye population is the only single biological stock in the Stikine River for which annual catch and escapement data are available. Prior to 1980, over 90 percent of the Stikine•s sockeye production was thought to originate from Tahltan Lake (Bergmann 1978) • However, as stock identification techniques improved, it became evident that other stocks, especially the "river stocks" whose progeny rear in the river or in the estuary instead of in nursery lakes, account for the majority of the Stikine sockeye run (Craig 1985; Wood et al. 1987a). The river stocks and glacial lake stocks are extremely difficult to enumerate because they spawn in glacially-turbid water throughout the Stikine-Iskut drainage. They are also difficult to distinguish from each other using biological attributes for stock identification. In contrast, Tahltan Lake sockeye migrate upstream earlier than other Stikine sockeye stocks, and can be identified reliably using a variety of biological attributes (scale patterns, egg diameter, allele frequencies at the lactose dehydrogenase-4 locus, and prevalence of the myxosporean parasite Myxobolus neurobius, Wood et al. 1987b). Hence, the two ~tock mqnagement 12 approach is based on feasibility and convenience rather than on bioloqical principles.

2.2 Bscapement Data Tahltan stock: Spawninq escapements of sockeye salmon to Tahltan Lake have been enumerated at a weir situated near the lake's outlet since 1959. Escapements have ranqed from 1,471 to 67,326 and the trends suqqest a 4- to 5-yr cycle with peak escapements in 1972, 1977, 1981, and 1985 (Fiq. 2). When the escapement data are smoothed with a five year movinq averaqe, lonqterm trends in escapement become more obvious. Generally, the averaqe escapement increased from the initial five year period throuqh the 1963-1968 period. This can probably be attributed to the construction of a water flow control structure at the outlet of Tahltan Lake which has stabilized water flow throuqhout the period of sockeye miqration. From the 1964-1968 period throuqh the 1976-1980 period, the averaqe escapement was fairly stable around the lonq term averaqe (i.e. 19,500 sockeye). The averaqe escapement increased from this level to a peak of 40, 100 sockeye in the 1981-1985 period, but has declined steadily since that time to the most recent 5-yr averaqe of 21,100 sockeye. Non-Tahltan stock: Non-Tahltan sockeye have been enumerated annually by aerial surveys since 1984 in several index areas, but direct enumeration is impractical for most areas owinq to the turbid water and the widespread distribution of sockeye within the watershed. Total escapement for the non-Tahltan stock has been estimated since 1979 by subtractinq the Tahltan escapement and Canadian catches from the estimated total run across the Canada u. s. border ("border escapement") (see Section 2 • 3) • The two measures of escapement are hiqhly correlated after 1984, and there is no indication of an overall trend in escapements since 1979 (Fiq. 3). The non-Tahltan escapement has averaqed 33,425 since 1979.

2.3 Total Run into Canada (Border Bscapement) A test fishery employinq drift and set qillnets immediately upstream of the Canadian border provides CPUE data and samples for stock composition analysis. These test fishery data are analyzed to determine the relative abundance of the Tahltan and non-Tahltan stocks. In addition, the Canadian fisheries are sampled to determine the total Canadian catch of each stock. The total Tahl tan run is calculated by summinq the Tahltan catch and the Tahltan escapement (weir counts). Then, the total border escapement can be estimated by dividinq the total Tahltan run by the estimated proportion of Tahl tan fish in the test fishery. Various procedures were used to estimate the proportion of Tahltan 13 fish between 1979 and 1985 (Craiq 1985; Wood et al 1987a) , but since 1986, a standard procedure has been adopted by the TCTR (PSC 1989a). Estimated border escapements have ranqed from 34,116 in 1979 to 172,717 in 1985, and have averaqed 75,817 since 1979.

2.4 catches in Alaska The number of Stikine sockeye cauqht by the Alaskan fisheries was unknown prior to 1979. Since 1980, catches of Stikine sockeye have been estimated by scale pattern analysis in districts 106 and 108 but not elsewhere (Table 1). The reliability of estimated catches of Stikine sockeye in Alaska is questionable owinq to the number and complexity of mixed-stock fisheries likely to intercept sockeye returninq to the Stikine River. Recent estimates of interceptions of the Tahltan stock in districts 106 and 108 are probably reasonable; estimates from scale pattern analysis have been corroborated for some samples by stock identification procedures usinq other bioloqical markers. However, the total U.S. catch of Stikine sockeye, particularly the non-Tahltan component, remains controversial. The overall Stikine sockeye run appears to have ranqed from 42,415 in 1979 to 202,464 in 1985, and averaqed 92,192 since 1979. Alaskan harvest rates on Stikine sockeye have averaqed 16. 5% since 1979; overall harvest rates have averaqed 38.5% with an averaqe harvest share of 57.5% cauqht by Canadian fishermen.

2.s stock-Recruitment Analysis Tahltan stock: Reliable escapement estimates and aqe composition data are available since 1959 for the Tahltan stock. Unfortunately, the lack of catch data prior to 1979 makes conventional stock-recruitment analysis difficult. Nevertheless, we have attempted stock-recruitment analyses, first, usinq total adult returns since 1979, and second, usinq only adult returns to the Tahltan Lake weir since 1959 (iqnorinq catches), summarized by brood year (Table 2). In the second analysis, we assumed that historical exploitation rates on Tahltan Lake sockeye averaqed over all fisheries has been constant over the period 1959-1989. Ricker stock-recruitment curves were fitted to the data in Table 2 as follows:

curve 1 (Table 2A): ln(R/E) = 1.400 - 0.040(E) [lA] F2,8 = 3.090, p > 0.05, r = -0.53 curve 2 (Table 2B): ln(R*/E) = 0.609 - 0.029(E) [lB] F2, 22 = 5.62.9, p < 0.01, r = -0.44 14 where R denotes adult returns by brood year and E, the parent escapement in thousands of fish. To include the 1984 brood year, we ignored potential contributions by age 2.3 fish returning in 1990 since this age class has never been very abundant. Note that in eqn [lB], R* denotes adult returns to Tahltan Lake excluding catch. The regression analysis for eqn [lB] and trends in residuals are presented in Figure 4. Total returns (TR) can be estimated by R / (1-u) where u is an assumed historic exploitation rate averaged over all fisheries. Thus, the corresponding stock-recruitment relationship for total returns is: ln(TR/E) = ln(R*/(1-u)E) = ln(R*/E) - ln(l-u) = 0.609 - 0.029(E) - ln(l-u) [2] The estimated optimal escapement, found by iteration to maximize TR - E with respect to E, will depend on what historic exploitation rate is assumed.

Hon-Tahltan stock: The historic data on non-Tahltan sockeye catches and escapements are less extensive than those for Tahltan stocks. Although catch and escapement data for non-Tahltan sockeye have been recorded since 1979, they are considered to be less reliable than those for Tahltan sockeye. The accuracy of marine catch data for the non-Tahltan stock is especially questionable given the overlap in run timing between non-Tahltan, Alaskan, Nass, and Skeena stocks and the general similarity in biological attributes between non-Tahltan and some Alaskan stocks; these factors create great potential for misclassification in conventional stock identification analyses (Wood et al. 1988, 1989). Also, the non-Tahltan escapements have been derived from test fishery statistics rather than from actual counts as for the Tahltan stock. Age composition data specific to this stock are not available. Even so, we have attempted a stock-recruitment analysis using estimates of returns for brood years 1975-1984. Because non-Tahltan escapement data are not available from 1975-1978, these escapements were estimated by assuming a fixed ratio of Tahltan:non-Tahltan escapements equivalent to the average ratio from 1979-1986 (0.86:1). Escapements ratios from 1979-1986 were relatively constant; those since 1987 were excluded because they have been much lower (0.11:1 to 0.36:1), reflecting the poor rates of return to Tahltan Lake in recent years (see Section 5). Total returns of non-Tahltan sockeye from the 1975-1984 brood years were reconstructed from the annual catch and escapement data, using age composition data from the Lower Stikine commercial fishery (Table 3). This was necessary because inadequate age data are available for the non-Tahltan escapements. Nevertheless, the age data from the fishery should provide a reasonable indication of the non-Tahltan age composition considering that, on average, 60% 15 of the total annual sockeye catch in the lower Stikine has been non-Tahltan sockeye. A Ricker stock-recruitment curve was fitted to the data in Table 3 as follows:

ln(R/E) = 1.406 - 0.020(E) [3] F218 = 7. 77, p < o. 025, r = -o. 70

2.6 Assessment of Juvenile Production in Tahltan Lake Sockeye smolt migrations have been enumerated at the Tahltan Lake weir since 1984 (Table 4) • The counts are reliable and represent a considerable range in spawning escapements. To test whether low egg-to-smolt survival resulted from limitations on fry recruitment, fry production resulting from the observed escapements was estimated as follows:

PF = (S1+ + S2+f0.6) / 0.5 [4] where PF, s,., and s2• represent the abundance of presmol t fry (in late August), age 1+, and age 2+ smolts, respectively. The constants 0.5 and 0.6 are the assumed survival rates for presmolts to age 1+ smolts, and for yearlings remaining in the lake for a second year, respectively; these rates are typical estimates based on data from other lakes (Dr. Kim Hyatt, Pacific Biological Station, Nanaimo, B.C., V9R 5K6, pers. comm.; Dr. Jeff Koenings, Alaska Dept. Fish and Game, P.O. Box 3150, Soldotna, Ak 99669, pers. comm.). Survival rates from egg to presmolt fry are highly correlated with those from egg to age 1+ smolt, and show the same general pattern when plotted against spawning escapement (Fig. 5). However, the presmol t fry abundance estimate also takes into account the abundance of yearlings holding over in the lake another year to smolt at age 2+. Thus, the presmolt fry estimate should provide more insight into density dependent processes occurring during the first year (incubation through smelting), provided the assumed survival rates are approximately correct. Because age 2+ smolts from the 1987 brood year have not yet been enumerated, we have ignored their contribution to presmolt fry abundance; the estimate of presmolt fry abundance for the 1987 brood year is therefore minimal. A Ricker stock-recruitment curve was fitted to the presmolt fry abundance and escapement data in Table 4 as follows:

ln(PF/E) = 4.713 - 0.028(E) [5] F24 = 3.86, p > 0.05, r= -0.70 I

An optimal escapement range was estimated f+om this relationship by 16 assuming that survival after smelting was independent of density, and that presmolt fry-to-adult survival is typically between 2 and 5%. For example, at a presmolt-to-adult survival of 2%, 50 presmolt fry are required to replace one spawner, and the sustainable yield of adults is maximized at the point on the presmolt production vs escapement curve where the slope equals 50 (i.e. parallel to the replacement line).

3.0 Productivity Evaluations 3.1 Tahltan stock Analysis of Adult Returns: The Ricker stock-recruitment curve fitted to the total adult return data in Table 2A explained 28% of the variation in adult returns, but this was not statistically significant (p> 0.20) owing to the short time series available (Fig. 6). The estimated optimal escapement from this relationship was 15,000 spawners. A second Ricker stock recruitment curve fitted to brood tables compiled from escapement data from 1959 to 1984 (Table 2B, excluding catch) explains less (19%) of the variation in returns, but is statistically significant (p<0.01) (Fig. 7). Here, we assumed implicitly that the historic exploitation rate on Tahltan sockeye averaged over all fisheries has been constant. This assumption is probably unrealistic. Even so, if exploitation rate varied randomly over the period in question independently of run size, then the returns to the lake used in this analysis would be an inefficient (i.e. , noisy) but unbiased estimator of total returns. Stock-recruitment functions based on noisy data will tend to underestimate optimal escapements (Walters and Ludwig 1981). However, this bias would probably be small in comparison to the bias that would arise if exploitation rates varied according to run size. The Alaskan fisheries exploit a large number of small Alaskan stocks as well as a portion of larger, southward-migrating runs to the Skeena and Nass rivers. The fleet is very mobile and fishing areas are scattered throughout Southeast Alaska. It seems likely that exploitation rates on Tahltan Lake sockeye would be determined by many factors in addition to the abundance of this relatively small stock. Thus, overall exploitation rates on Tahltan Lake sockeye were probably only weakly correlated with run size, and the present analysis is considered to be reasonable. Total returns including catch must have been larger than the returns without catch considered in this analysis. The corresponding relationship between total returns and spawning escapement, and hence optimal escapement, depends on the historic exploitation rate (see eqn [2]). Estimates of optimal escapement range from 12,000-30,000 for exploitation rates from 0.1 and 0.9, respectively (Fig. 8). Best estimates of exploitation rate in recent yea+a ~+e a+o:&.:m4 O.l to o.s, which au.gge$ts t:Qqt the optimal 17 escapement for Tahltan Lake is 15,000-20,000 spawners. This estimate includes the previous estimate from eqn [lA], and falls just below the target escapement range (20,000-40,000) recommended by the TCTR (PSC 1988a).

Analysis of Juvenile Production: Sockeye smolt migrations have been enumerated at the Tahltan Lake weir since 1984. Although data are available for only six years, the counts are reliable and represent a considerable range in spawning escapements (Table 4). Thus, these data provide an alternative, independent means for assessing the productivity of Tahltan Lake sockeye. Tahltan Lake was enriched artificially with fertilizer during the summers of 1985 through 1988. Unfortunately, this treatment confounds the assessment of natural productivity, to some extent, given the short time series of data available. Egg-to-smolt survival based on potential egg deposition (assuming 2,900 eggs per female) and the number of age 1+ smelts at the Tahltan weir has ranged from only 1.6% to less than 0.5% since the 1982 brood year (Fig. 5). It is clear that egg-to-smolt survival drops drastically at spawning escapements above 20,000. Egg-to-presmolt survival calculated so as not to exclude production by age 2+ smelts (see Methods) shows this pattern even more clearly. A Ricker stock-recruitment curve was fitted to the presmolt fry production plotted against spawning escapement (eqn [5], Fig. 9). From this plot, we concluded the optimal escapement is in the range of 14,000-22,000 by assuming the average survival of presmolt fry to adults is 2-5%, and that survival after smelting is not influenced by smolt abundance. If presmolt-to-adult survival is less than 2% on average, the appropriate replacement line in Figure 9 will have a steeper slope and the optimal escapement would be correspondingly less. Presmolt-to-adult survival statistics are available for only the last three brood years ( 1982-1984) , and these range from only 0.6 to 1.4%. However, these survival rates are probably anomalous in view of typical survival rates reported for other sockeye runs, and historic run sizes to Tahltan Lake (see next section). The smolt and adult counts at Tahltan Lake are considered to be relatively accurate, but the juvenile production analysis is based on only six years' data and should be interpreted with caution. The chief uncertainty arises from whether brood years 1982-1986 were typical ones. The addition of fertilizers in 1984- 1988 makes this question especially critical. Hydroacoustic and zooplankton surveys undertaken in August 1987 indicate that zooplankton at sizes utilized by sockeye fry (>500 um) were extremely plentiful relative to the fry densities observed (PSC 1988c) • Evidently, lake fertility was increased more 18 than necessary in 1987, and it seems probable in hindsight that fertilization was not required at all. Similarly, there is no indication that lake fertilization in 1985 increased the size of age 1+ smolts from the 1984 brood year compared to those from the 1982 brood year when presmolt fry abundance was comparable (Table 5, Fig. 10). Neither is there any indication that lake fertilization increased the freshwater survival of the 1984 brood year. It could be arqued that fertilization in 1986 and 1987 helped to maintain the relatively large size (5 g) of age 1+ smolts in 1987 and 1988, despite the higher density of presmolt fry. However, there are no untreated years at comparable fry densities to test this arqument, and benefits of fertilization have yet to be demonstrated. Because lake fertilization appears to have been unnecessary, at least at typical presmolt fry densities, it follows that the rearing capacity of Tahltan Lake does not limit its sockeye production. It seems more probable that egg-to-presmolt fry survival is limited by inadequate spawning habitat. The abrupt decline in egg-to-presmolt survival at escapements exceeding 20, ooo is consistent with this explanation (Fig. 5). Tahltan Lake has no tributaries suitable for spawning, and spawning is restricted to the gravel margins of the lake. Alternatively, fry survival may be reduced at high densities owing to the effect of predators feeding in a compensatory fashion, perhaps during the smolt migration at the lake outlet, but only when the smolts are abundant. Tahltan Lake is known to support dense trout and char populations. comparison of Analyses of Adult and Juvenile Production: Both the analyses of adult and juvenile sockeye production from Tahltan Lake indicate that the optimal escapement range is between 15,000 and 20,000 spawners. This agreement is encouraging, but in both types of analysis, it was necessary to make questionable assumptions. In our analysis of longterm adult production, we assumed historic exploitation rates were constant at around 30-50%; in the analysis of juvenile production, we assumed that presmolt fry survival was 2-5%. Because the two analyses are essentially independent, it is possible to examine whether other predictions from the two analyses are consistent by reconstructing historic brood tables from hindcasted estimates of presmolt production. We calculated presmolt fry production for each brood year since 1959 using eqn [ 5] , and then, the range of total adult returns expected with presmolt-to-adult survival rates of 2-5%. We then assigned these expected total returns to calendar years according to the observed age composition in returns to the Tahltan weir (by brood year). Finally, we calculated the harvest rate in each calendar year that would have been required to produce the observed escapement. The resulting trends in "calculated harvest rates11 ·are plotted in Fig. 11 for various presmolt-to-adult survival rates. Note that negative harvest rates result wherever observed escapements, and thus actual returns, exceed the total returns predicted from 19 presmolt production. Clearly, reasonable harvest rate trends result only if presmolt-to-adult survival rates typically exceed 2% (assuminq that the lake's capacity to produce presmolts has not chanqed) • This analysis shows that the adult and juvenile production analyses are loqically consistent. We conclude that it is not merely fortuitous that the two independent estimates of optimal escapement are so similar. Moreover, the historic reconstruction qives further support to our belief that the observed presmolt-to-adult survival rates of 0.6-1.4% are unusually low.

3.2 Bon-Tahltan Stock Analysis of Adult Returns: The Ricker stock-recruitment curve fitted to the total adult return data in Table 3 explained 49% of the variation in adult returns, and was statistically siqnificant (p<0.025), which is surprisinq considerinq weaknesses in the data and the short time series available. The estimated optimal escapement from this relationship is 20,000 spawners (Fiq. 12). This estimate falls in the lower part of the tarqet escapement ranqe (20, 000-40, 000) recommended by the TCTR (PSC 1988a). However, qiven the limitations of the data to which the stock-recruitment model is fitted (see Section 2. 5), this estimate should be considered unreliable.

4.0 Pre-season sockeye Forecasts 4.1 Forecasts by the TCTR A pre-season forecast of the total Stikine sockeye run is required by the Treaty to quide the initial fishinq reqimes in Alaska districts 106 and 108 and in the Canadian in-river commercial fishery. Prior to 1988, annual forecasts were developed by Canada based on brood year escapements, averaqe aqe composition, annual sex composition, and an assumed productivity (return/female spawner) based on historic bio-standards. Returns of the principal aqe classes were calculated, then summed to qive expected total returns. The official forecasts for 1988 and 1989 were developed by the TCTR and were based on the averaqe of the Canadian and U.S. forecasts for each year. In the conventional procedure used by Canada, adult returns to Tahl tan Lake were predicted from the Tahltan Lake smelt count three years earlier assuminq a 10% smolt to-adult survival; non-Tahltan returns were predicted from non Tahltan escapements using the stock-recruitment relationship developed for the Tahltan stock (eqn [2]), assuminq an historic exploitation rate of 40%. Forecasts of non-Tahltan stocks were not made from eqn [3] owinq to the short time series in available data. The U.S. forecast for 1988 was based on a time series analysis of Tahltan returns, whereas the 1989 method involved the use of a siblinq forecast model (PSC 1988a, PSC igs~,il~~ 20

The regression of annual forecasts on actual returns of Stikine sockeye since 1980 indicates a poor, and negative correlation between predicted and observed returns ( r=-o. 3 7) • Total run size estimates were not available prior to 1979 and no forecast was made prior to 1980. The unsatisfactory performance of past forecasts necessitates further examination of the relationships between stock and recruitment, smolts and adults, and sibling age classes. We hope that our forecasting capabilities will improve as more data accumulate.

4.2 Stock-Recruitment Ketho4 Forecasts of Tahltan returns can be made by estimating returns from the age 4, age 5 and age 6 brood year escapements, individually, using eqn [lA], and then by apportioning the respective returns using average age composition data. However, this stock-recruitment relationship is weak (r2=0.28), and based on total return observations for only the past 10 years. Therefore, an alternative method would be desirable. Similarly, return and escapement data for the non-Tahltan stock are available only since 1979, and these are considered to be less reliable than for the Tahltan stock. Perhaps fortuitously, the stock-recruitment relationship in these data ( eqn [ 3] ) is stronger (r2=0.49) than for Tahltan sockeye. Although we are somewhat sceptical of the relationship, eqn [3] can be used to forecast returns of non-Tahltan sockeye following the procedure described for Tahltan sockeye in the preceding paragraph. 4.3 Sibling Ketho4 To test whether the sibling model was worth pursuing, the return of age 5 sockeye to Tahltan Lake in year t+l was regressed on the return of age 4 sockeye in year t. Only age composition data from 1979-1989 were used because it is believed that age determinations prior to 1979 were not as reliable. A strong correlation (r=0.96) was demonstrated between the escapements of sibling age 4 and 5 sockeye to Tahltan Lake from 1979-1989. The correlation between the total returns of sibling age 4 and age 5 sockeye was only slightly weaker (r=0.81, Fig. 13). It appears, therefore, that the sibling forecast procedure will be useful for predicting the returns of age 5 sockeye which typically account for about 80% of the Tahltan sockeye run. No satisfactory procedure has yet been discovered for predicting the returns at age 4. The relationship between total escapement and ln(returns/spawner) at age 4 is weak (r2= 0.19). A slightly better relationship exists between the escapement of age 5 sockeye and the ln(returns/spawner) at age 4 (r2 = 0.30), ~lthough 1;4ia c~c•WJliQn may be spurioJMI given the ii~ited data 21 available. There is a very weak relationship between the escapement of age 4 sockeye and ln(returns/spawner) at age 4. In the four years examined to date, smelt production from Tahltan Lake has been poorly correlated with subsequent returns at age 4 (r=O. 28). Because there seems to be no adequate method for predicting returns at age 4, yet sibling age 4 and 5 returns are highly correlated, we regressed the total Tahltan return (all ages) on the total return of Tahltan age 4 sockeye in the previous year as follows:

T}\+1 = 5.063(R4,t> + 21261 [6] F218 = 12.73, p < 0.01, r=0.78 where: TRt+1 is the total return in year t+l, and R4,t is the return of four-year olds in year t (Fig. 13).

The sibling forecast method was not evaluated for the non Tahl tan stock because there is insufficient age composition data for this stock.

4.4 Forecasts for 1990 and 1991 Tahltan stock: The 1990 forecast of Tahltan total returns based on the age 4-age 5 sibling eqn [6] is 30,200 sockeye. No sibling forecast can be made for 1991 until the total return of 4 year olds is known in 1990. Forecasts for Tahltan returns in 1990 and 1991, based on the stock-recruitment method, eqn [lA], and the average age composition of 80% age 5, 13% age 4, and 6% age 6, are as follows:

Brood Escape. Est'd Return 1990 1991 Year From Eqn [lA] Return Return 1984 32,777 35,825 2,150 1985 67,326 18,400 14,720 1,104 1986 20,280 36,541 4,750 29,233 1987 6,958 21,361 2,777 Total return forecast 21,620 33,114 ======

The forecasts for 1990 and 1991 based on Tahltan smelt counts and an assumed survival of 5-10% are 37,800-75,600, and 58,500- 117,000 fish, respectively. 22 At this time, it appears that, when possible, the sibling method is the most appropriate forecasting method for Tahl tan sockeye. A stronger correlation was observed between age 4 and age 5 Tahltan sockeye returns than between total returns by brood year and escapement, or between total returns and smol t production three years earlier. Our second choice is the stock-recruitment method, perhaps qualified by the smelt forecast. Of course, this evaluation may change as more data become available. Our best forecasts for Tahltan sockeye returns are, therefore, 30,200 in 1990 and 33,100 in 1991, based on the sibling method and stock-recruitment method, respectively.

Non-Tahltan stock: Based on the stock-recruitment relationship described in eqn [3], and average age composition from the lower river (72% age 5, 23% age 4, and 5% age 6), the 1990 and 1991 forecasts of the non-Tahltan sockeye stock are:

Brood Escape. Est'd Return 1990 1991 Year From Eqn [3] Return Return 1984 33,753 70,106 3,505 1985 77,247 67,226 48,403 3,361 1986 25,010 61,872 14,231 44,548 1987 19,353 53,612 12,331 Total return forecast 66,139 60,240 ======An alternative method for forecasting non-Tahl tan returns would be to simply assume that the ratio of Tahltan:non-Tahltan stocks in the total return will be the same as it was in the primary brood year, i.e. five years ago. The ratio of Tahl tan: non Tahl tan escapements in 1985 was 0.87:1, so the forecasted non Tahltan return for 1990 is 34,700 sockeye. Similarly, the ratio of Tahltan:non-Tahltan escapements in 1986 was 0.79:1, and the forecasted non-Tahltan return for 1991 is 46,254 sockeye (using the stock-recruitment forecast of 36,541 Tahltan sockeye in 1991). Tahl tan: non Tahl tan escapement ratios were fairly constant from 1979-1986, but have been declining in recent years. Accordingly, we prefer forecasts for non-Tahltan returns based on the stock-recruitment method, despite obvious weaknesses. At least, forecasts from the stock-recruitment method will not be biased by the recent downward trend in Tahltan smelt survival. Our best forecasts for non-Tahltan sockeye returns are, therefore, 66,100 in 1990 and 60,200 in 1991 based on the stock recruitment method. 23 Total Returns to the Stikine: The total Stikine return forecasts for 1990 and 1991 are 96,300 and 93,300 sockeye, respectively. These are both below the TCTR forecasts (made by Canada) for the Stikine of 122,200 and 136,200 sockeye, respectively, based on Tahltan smolt production and non-Tahltan escapements applied to the Tahltan stock-recruitment model. s.o stock status The total sockeye return to the Stikine River in 1989 was 95,718, slightly above the 1979-1988 average of 91,839 sockeye. Although run sizes have fluctuated since 1979, there is no evidence of a trend in overall Stikine sockeye abundance. However, the return to the Tahltan stock in 1989 was only 14,111, well below the 1979-1988 average of 29,149; Tahltan returns have been below average since 1987. In contrast, the non-Tahltan return in 1989 was 81,607 and above the 1979-1988 average of 62,690. Sockeye escapements to Tahltan Lake have been below the target range set by the TCTR (20,000-40,000), and the estimated optimal levels reported here (15,000-20,000) since 1987, ranging from 2,536-8,316. The non-Tahltan escapement in 1989 was within the target range (20,000-40,000) and slightly above the optimal level reported here (20,000); non-Tahltan escapements in 1987 and 1988 were very close (19,353 and 22,840, respectively) to the estimated optimum. Sockeye returns to the Tahltan and non-Tahltan stocks tend to be correlated (Fig. 14A). However, the non-Tahtlan stock has been relatively more productive in recent years. The poor returns of Tahltan sockeye since 1987 clearly result from poor survival after smolts have left Tahltan Lake; age 1+ smolt survival has ranged from only 1.1-6.9%. There are several possible explanations for these poor rates of return: First, apparent poor rates of return could result from large unreported catches in Alaska where Tahltan sockeye may go undetected in mixed-stock fisheries. Second, marine survival may have been poor owing to natural events. Third, Tahl tan smolt survival may have been adversely affected by the recent enumeration program. Since 1984, the number of smolts leaving Tahltan Lake has been estimated by a volumetric procedure. Smolts are trapped behind a smolt weir, transferred into buckets by dipnet, where the volume of water they displace is recorded, and then released; random samples are collected for biological data and to determine the number of smolts in a given volume of water. Although the entire run is "counted", very little handling of smolts occurs. It seems unlikely that large unreported catches of Tahltan sockeye can have caused rates of return to appear poor in recent years. Sockeye catches in commercial and test fisheries in Alaska 24 durinq the normal period of Tahltan miqration were unusually low from 1987-1989, suqqestinq overall low stock abundance. Because Tahltan smelt production is unknown prior to 1984, we cannot evaluate chanqes in marine survival directly. However, we can estimate the number of presmol t fry produced from historic escapements to Tahltan Lake usinq eqn [5], and calculate presmolt to-adult survival rates for the 1975-1984 brood years. The calculated survival rates compare very favourably with rates observed in the past three years (Fiq. 14B). Moreover, there appears to have been a downward trend in presmolt survival since the 1975 brood year, with one year of apparently exceptional survival (the 1980 brood year which resulted in record returns to Tahltan Lake). Note that calculated presmolt survivals were already very low for brood years prior to those that miqht have been affected by the smelt emumeration proqram. This, toqether with empirical observations reqardinq the survival of smelts held in caqes after enumeration, suggests that the smelt enumeration proqram is not responsible for the recent poor rates of returns. The forecasts for both Tahltan and non-Tahltan returns in 1990 and 1991 are very close to the 1979-1989 averaqe. Because Tahltan smelt production reached record levels (since 1984) in 1987 and 1988, these forecasts, which are not based on smelt counts, imply that smelt survival will continue to be poor. If, however, smelt survival improves, Tahltan returns should be considerably qreater.

&.o Data an4 Information Bee4s Assessment of Stikine sockeye production is limited, first, by the short time series of total return data, and second, the reliability of these data for the period since 1979. Catch data from Canadian fisheries are probably adequate, but the potential for errors in stock identification in Alaskan mixed-stock fisheries means that catch data from Alaskan fisheries may be less reliable.

Catch and escapement data for the Tahltan stock are probably much more reliable than those for the non-Tahltan stock. Escapements for the non-Tahl tan stock are calculated from test fishery CPUE and stock composition estimates. In fact, small changes in the estimate of relative Tahltan:non-Tahltan abundance ("the Tahltan proportion") based on the test fishery can cause large chanqes in the estimate of non-Tahltan escapement. Although current stock identification techniques give precise results for individual (i.e. weekly) samples, these samples must be combined and weiqhted correctly to give an accurate estimate of the Tahltan proportion over the entire run. Weekly samples are typically weighted accordinq to weekly CPUE in the test fishery. Thus, the overall estimate of the Tahltan proportion will be biased if there are stock-specific differences or seasonal trends in catchability 25 (since the Tahltan stock returns earlier in the season than the non-Tahl tan stock) • In recent years, much effort has been directed at evaluating the effect of test fishery design (e.g. the effects of drift nets versus set nets or sonar, bank orientation, mesh size, water level, detritus load, and run size). The present drift net test fishery appears to be a good compromise between practicality and reliability. Tagging studies could be designed to estimate directly the relative catchability of the two sockeye stocks, and of coho and chinook salmon besides; once relative catchabilities are determined, the test fishery CPUE data could be used to estimate absolute border escapements, using the Tahltan sockeye weir count as a "benchmark". such a program might be worthwhile, but would be very expensive. Forecasting and assessment of the productivity of the non Tahltan stock are also hampered by a shortage of age composition data representative of the mix of different populations. However, representative data would be extremely difficult to collect annually from the various spawning grounds. Samples from the fishery are easier to obtain, and may be more representative provided Tahltan sockeye are excluded. In future, samples from the test fishery should be classified as "Tahltan" or 11 non-Tahltan11 using a suitable stock identification technique, so that age data may be obtained from the 11 non-Tahltan11 component. Age data from the "Tahltan" component could be compared with corresponding data from the Tahltan weir to verify the procedure. It is clear from our assessment of Tahl tan sockeye that something limits production from escapements exceeding 20, ooo spawners. At present, it is impossible to determine whether survival is limited during incubation or during rearing/smolting. We are confident, however, that forage for sockeye fry does not limit their growth, nor presumably, their survival. The scheduled outplants of sockeye fry to Tahltan Lake, if properly monitored, should resolve this issue. If the outplanted fry survive and grow well at high stocking densities, then it follows that the incubation environment limits natural production. Moreover, the thermal marks being added to outplanted fry may provide the means to obtain convincing estimates of Tahltan catches in Alaskan fisheries, and hence, the means to accurately monitor trends in smelt survival. Forecasts of stikine sockeye returns have been very unreliable to date. These forecasts are especially important for managing Stikine sockeye because the forecasted run size drives the intricate harvest sharing formulas required under the Pacific Salmon Treaty. New procedures, including the sibling method, show some promise and should be evaluated further. However, the time series of returns is still too short to permit rigorous evaluation of alternate models. 26 7.0 Recommendations 1) Proceed with the scheduled outplants of newly-emerged sockeye fry to Tahltan Lake. These fry are being raised, and thermally marked at the Snettisham hatchery in Alaska. The following benefits are expected: i) increased adult production from Tahltan Lake if the incubation environment currently limits natural production; if no increased smolt production is observed, survival must be limited by other factors during rearing or smolting (e.• g. predation or disease). ii) the occurrence of thermally-marked Tahltan sockeye in Alaskan catches should provide more convincing data on interception rates, and Tahl tan smol t survival than conventional analyses based on natural differences in scale patterns. This is especially true in "outside" fishing areas (e.g. districts 101 and 104) where many sockeye are caught, but present techniques and sampling levels are inadequate to detect relatively small contributions by Tahltan sockeye. If Tahl tan production is increased, and thermal marks prove effective, the proportion of Tahltan sockeye in these areas should also rise to measurable levels. 2) Modify the smolt enumeration procedures at Tahltan Lake to ensure that this program is not responsible for the poor smolt-to adult survival rates observed in recent years. The program should be revised so that only a subsample of the smolt run is handled, instead of the entire run as in the current program. This is also necessary in view of the increase in smol t production from fry outplants expected after 1991. 3) Continue to explore alternate methods of forecasting Stikine sockeye abundance. These forecasts play a critical role in determining harvest rates on Stikine sockeye in the joint Canada u. s. management plan, which is relatively inflexible during the fishing season. 4) Maintain existing enumeration and test fishery programs, but collect additional non-Tahl tan age composition data from test fishery samples. 5) Revise the non-Tahltan escapement goal to 20,000 spawners (from 20,000-40,000) in view of the similarity of estimates from at least two independent analyses. The recommended escapement goal for the non-Tahltan stock remains unchanged at 20,000-40,000 because our point estimate of 20,000 is considered to be unreliable. 27 a.o Literature Cited Alaska Geographic. 1979. The Stikine River. Alaska Geographic 6:93 p. Bergman, W. 1978. Salmon spawning populations of the Stikine River. Unpubl. Rep., Alaska Dept. of Fish and Game, P.O. Box 20, Douglas, Ak 99824. 26 p. Craig, P.C. 1985. Identification of sockeye salmon (Oncorhynchus nerka) stocks in the Stikine River based on egg size measurements. Can. J. Fish. Aquat. Sci. 42:1696-1701. Crouter, R.A. and I.S. Todd. 1965. The Stikine River exploratory fishing program, 1965. Unpubl. Rep., Department of Fisheries of Canada, 555 w. Hastings Street, Vancouver, B.C. V6B 5G3, 17 p. Department of Fisheries and Oceans. 1965. A summary of the status of salmon stocks indigenous to streams originating on the Canadian side of the international border between British Columbia and the Alaska panhandle. Unpubl. Rep., Department of Fisheries and Oceans, S0-6th Street, New Westminster, B.C. V3L 5B3. Edgington, J. and B. Lynch. 1984. Revised anadromous stream catalog of southeast Alaska, District 108: Stikine River and its tributaries. Volume 1. Alaska Department of Fish and G.ame. Tech. Data Rept. No. 125:186 p. Gazey, W.J. and D.A. Birdsall. 1984. Design and execution of a stock interception study: part c, the 1983 north coast salmon tagging project. Unpubl. Rep., Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, B.C. V9R 5K6. 115 p. Hawthorn, R.S., Grant, D.J., and E.J. Koraka. 1984. Biophysical stream survey summary report: Iskut - Stikine - Unuk. Unpubl. Rep., Ministry of the Environment, Victoria, B.C. 17 p. Masse, W.D. 1988. Economic analysis of Stikine River commercial fishing and processing. Unpubl. Rep. Department of Fisheries and Oceans. 555 West Hastings Street, Vancouver, B.C. V6B 5G3. 15 p. Northern Natural Resources Services Limited. 1979. stikine - Iskut aquatic ecological studies, 1978: downstream sections. Unpubl. Rep. prepared for B.C. Hydro. Northwest Enhancement Society. 1985. Biophysical investigations of the Stikine River and its tributaries. Unpubl. Rep., P.O. Box 489, Cumberland, B.C. VOR lSO. 28 Pacific Salmon Commission. 1988a. Salmon management plan for the transboundary rivers, 1988. Report TCTR (88)-2:72 p. Pacific Salmon Commission. 1988b. Salmon catches and escapements to the transboundary rivers in 1987. Report TCTR (88)-3:87 p. Pacific Salmon Commission. 1988c. Sockeye salmon enhancement feasibility studies in the transboundary rivers. Report TCTR (88)-1:23 p. Pacific Salmon Commission. 1989a. Salmon management plan for the Stikine, Taku, and Alsek rivers, 1989. Report TCTR (89)-1. 21 p. Pacific Salmon Commission. 1989b. Preliminary salmon catches, escapements, and enhancement activities in the transboundary rivers in 1989. Unpubl. Rep. prepared for the Pacific Salmon Commission and the Northern Panel by the Transboundary Technical Committee. Rice, c. 1986. A review of the Stikine River fisheries resource. ·Unpubl. Rep., Department of Fisheries and Oceans, S0-6th Street, New Westminster, B.C. V3L 5B3 Richardson, T.H. and N.D. Johnston. 1966. Stikine River red salmon studies. Alaska Department of Fish and Game. Info Leaf. No. 86:25 p. Savoie, P.J. 1975. Stikine River study. Unpubl. Rep., Environment Canada, Fisheries and Marine Service, Whitehorse, Yukon Territory, YlA 2T9. Walters, C.J. and A. Ludwig. 1981. Effect of measurement errors on the assessment of stock-recruitment relationships. Can. J. Fish. Aquat. Sci. 38: 704-710. Wood, c.c., B.E. Riddell, and D.T. Rutherford. 1987a. Alternative juvenile life histories of sockeye salmon (Oncorhynchus nerka) and their contribution to production to the Stikine River northern British Columbia, Canada. p. 12-24. In: H.D. Smith, L. Margolis, and c.c. Wood. Can. Spec. Publ. Fish. Aquat. Sci. 96. Wood, c.c., B.E. Riddell, D.T. Rutherford, and K.L. Rutherford. 1987b. Variation in biological characters among sockeye salmon populations of the Stikine River with potential application for stock identification in mixed stock fisheries. Can. Tech. Rep. Fish. Aquat. Sci. No. 1535:61 p. 29 Wood, c.c., G.T. Oliver, and D.T. Rutherford. 1988. Comparison of several biological markers used for stock identification of sockeye salmon (Oncorhynchus nerka) in northern British Columbia and southeast Alaska. Can. Tech. Rep. Fish. Aquat. Sci. No. 1624:44 p. Wood, c.c., D.T. Rutherford, and s. McKinnell. 1989. Identification of sockeye salmon (Oncorhynchus nerka) stocks in mixed-stock fisheriesin B.C. and southeast Alaska using biological markers. Can. J. Fish. Aqua. Sci. 46:2108-2120. 30

Table lA. Estimated catches of Stikine sockeye in Alaska, 1979-1989: Tahltan stock only.

Alaskan Border Total Alaskan Year Catch Escapement Returns Harvest Rate

1979 5076 14772 19848 0.256 1980 11239 19137 30376 0.370 1981 16189 65789 81978 0.197 1982 24785 42297 67082 0.369 1983 5104 30029 35133 0.145 1984 3211 35425 38636 0.083 1985 25197 80408 105605 0.239 1986 2757 28549 31306 0.088 1987 2242 11922 14164 0.158 1988 2135 7222 9357 0.228 1989 0 14111 14111 0.000

1979-89 8903 31787 40691 0.194 1984-89 5924 29606 35530 0.133 31

Table lB. Estimated catches of Stikine sockeye in Alaska, 1979-1989: Total (combined Tahltan and non-Tahltan).

Alaskan Border Total Alaskan Year Catch Escapement Returns Harvest Rate

1979 8299 34116 42415 0.196 1980 23206 62744 85950 0.270 1981 27538 138503 166041 0.166 1982 43329 68442 111771 0.388 1983 5810 65860 71670 0.081 1984 7827 71857 79684 0.098 1985 29747 172717 202464 0.147 1986 6420 63548 69968 0.092 1987 4061 39262 43323 0.094 1988 3185 41914 45099 0.071 1989 20688 75030 95718 0.216

1979-89 16374 75817 92191 0.165 1984-89 11988 77388 89376 0.120 32

Table 2A: Escapement and returns to Tahltan Lake by age and brood year: Returns including catch.

Returns (including catch)

Brood Escape- year ment 1.2 1. 3+2. 2 2.3 all ages

1975 8159 690 15281 798 16769 1976 24111 15593 74232 8112 97937 1977 42960 4789 53403 2283 60476 1978 22288 6084 34633 803 41520 1979 10211 1142 28522 1089 30753 1980 11018 10043 105674 1820 117537 1981 50790 2179 33850 1926 37955 1982 28257 728 12000 1047 13776 1983 21256 296 6982 1353 8631 1984 32777 3491 10420 ? (13911) 33

Table 2B: Escapement and returns to Tahltan Lake by age and brood year: Returns excluding catch.

Returns to Lake (excluding catch)

Brood Escape- year ment 1.2 1.3 2.2 2.3 all ages

1959 4311 1242 6992 368 105 8707 1960 6387 10856 1185 15 0 12056 1961 16619 195 20520 1080 388 22183 1962 14508 0 37248 388 985 38621 1963 1780 776 2364 985 117 4242 1964 18353 15366 10764 819 168 27117 1965 1471 0 1008 168 0 1176 1966 21580 7056 13690 0 524 21270 1967 38801 4810 49780 0 261 54851 1968 19726 2096 2436 29 567 5128 1969 11805 174 6399 81 656 7310 1970 8419 1053 6314 328 482 8177 1971 18523 902 13737 2169 430 17238 1972 52545 7712 36980 430 6913 52035 1973 2877 5160 10258 1115 612 17145 1974 8101 4014 9180 102 110 13406 1975 8159 306 5170 220 508 6204 1976 24111 5500 46736 508 3396 56140 1977 42960 3048 22074 283 1278 26683 1978 22288 2547 19383 0 656 22586 1979 10211 639 23944 0 673 25256 1980 11018 8200 65281 0 1015 74496 1981 50790 1346 18473 406 856 21081 1982 28257 406 5873 104 253 6636 1983 21256 7 1425 75 832 2402 1984 32777 75 5904 499 ? (7153) 34

Table 3: Escapement and returns for the non-Tahltan stock by age and brood year.

Returns to Lake (including catch)

Brood Escape- year ment 1.2 1.3+2.2 2.3 all ages

1975 9457 5776 30615 830 37221 1976 27947 22266 78867 5789 106921 1977 49795 3321 29834 1017 34172 1978 25834 8906 26112 1553 36571 1979 10371 6782 19805 1778 28365 1980 30807 17087 76439 1075 94600 1981 60089 9777 30093 2640 42510 1982 19645 4657 19272 1123 25053 1983 23484 3696 22458 4020 30174 1984 33753 13101 59493 ? (74797)

* 1975-78 escapements estimated by assuming a fixed Tahltan: non-Tahtlan ratio of 0.86:1 35

Table 4: Tahltan Lake smolt counts and reconstructed presmolt data by brood year (in thousands of fish).

Brood Escape Smolt Counts Estimated Year -ment age l+ age 2+ Presmolts 8

1981 50.8 ? 36 ? 1982 28.3 182 115 747 1983 21.3 497 33 1104 1984 32.8 206 104 759 1985 67.3 707 114 1794 1986 20.3 1057 56 2301 1987 7.0 524 ? 1048 b

a presmolt abundance (age O+, in late August) calculated by assuming: i) 50% survival of presmolts to yearlings: ii) 60% survival of yearlings holding over to smolt at age 2+. b minimum estimate: does not include fry emigrating as age 2+ smolts in 1989 36

Table 5: Summary of sockeye smolt size in Tahltan Lake relative to abundance and enrichment history.

Juvenile Abundance a Mean Weight (g) Year feeding (thousands) as Smolts Fertil as O+ fry age O+ age 1+ total age 1+ age 2+ -ized?

1983 364 60 424 5.8 11.1 no 1984 994 192 1186 4.0 9.8 no 1985 412 55 467 5.8 11.6 yes 1986 1414 170 1584 6.0 13.3 yes 1987 2114 187 2301 6.7 14.8 yes 1988 1048 ? 1048 7.1 ? no

8 age O+ abundance in year t = (age 1+ migration in year t+l)/0.5 age 1+ abundance in year t = (age 2+ migration in year t+l)/0.6 37

~ Canadlm lhrtver Flsherl•• '>. ' \ \ \

Figure 1. Map of the Stikine River and U.S. fishing districts off the mouth of the river. 38 Figure 2. Tahltan sockeye escapements

Number of Fish (thousands)

5-yr moving average

1959 1969 1979 1989 Year 39 Figure 3. Non-Tahltan sockeye escapement (thousands of fish)

Total Index

l.'-.·:O:.I Estimated Total 120 - Index Areas 4 5-yr moving average 100

3 80

60 2

1 20

0 ~____i:=L-....L l.---1=-~~ 0 1979 1984 1989 Year 40

Figure 4. Tahltan stock-recruitment analysis

A: Regression (eqn [18])

2 CJ D

D 1 D CJ

- 1 D D D -2 D

-3 0 10 20 30 40 50 60 Escapement (1000's) Residuals (ln[R/E]) 3 B: Trends in Residuals 2

-1

-2

-3 1959 1969 1979 Year ~ "Returns" do not Include catch ' I

41 Figure 5. Estimated egg-to-smolt (and presmolt fry) survival in Tahltan Lake

Proportion Surviving

D pres molt fry 0.1 + age 1+ smolt

0.05 +-',, ' ' ' ' '·

' ' '. . ~ -====--~~~------t.J " D D 85 \,82 84 '+. --+------.. ------+

o~~~~~~~~~~~_.__~ 0 20 40 60 Escapement (thousands) 2900 eggs/female; age O+ presmolts est. from smolt counts ' >

42 Figure 6. Tahltan Lake stock-recruitment relationshipJ 1975-1983: (from eqn [1A])

Returns Including Catch (thousands)

100 D

50 optimal D D

D D D

o~~_.__~_,_~_.___~~~--'-~---J 0 10 20 30 40 50 60 Escapement (thousands) . ' ' .

43 Figure 7. Tahltan Lake stock-recruitment relationship) 1959-1983 (from eqn [18])

Returns Excluding Catch- ( thousand·s) aor--~~~~~~~~~~~~~

60 0 0

40 0

0 0 0 20 0

0 0 0 0 0 o'--=-~~~~'--~--'-~--'~~-'-~--' 0 10 20 30 40 50 60 Escapement (thousands) 44 Figure 8. Optimal escapements for Tahltan sockeye (from eqn [2])

Optimal Escapement (thousands)

2 Q_ ------·----·-----·-·--·--··· -- -

10 I probable range

oL--~~--~~_._~~~~~~~ 0.1 0.3 0.5 0.7 0.9 Historic Harvest Rate 45 Figure 9. Sockeye presmolt production in Tahltan Lake versus escapement ( eqn [5]

Presmolts (millions)

replacement at * 20/o survival 2 5% *

1 D

...... •····· ..... ···· / ./ ... -·· ... ················

•.. ···

o~/~~~--1.~~~~-'--~~~--'--~~---- o 20 40 60 Escapement (thousands) Age O+ presmolts est. from smolt counts 46 Figure 10. Relationship between sockeye smolt size) presmolt fry density) and fertilization in Tahltan Lake

Smalt Weight ( g)

20 o not fertilized ---* fertilized

15 --· ---- .. -... ··········· .. --- .*·--- * ...... -··--a:90··2+ 10

83 85 D 88 ~--··················-··········--·-·--·······---·-···-··--··----·······---··*------·- e,·-; 5 age 1+ 86 D 84

oL--~~-L---~~-'-~~_.__~~~~~~ 0 0.5 1 1.5 2 2.5 Presmott Abundance (millions)

~ Year refers to year feeding in lake 47 Figure 11. Calculated harvest rates on Tahltan sockeye based on estimates of presmolt fry production from eqn [5]

Calculated Harvest Rate 1.5 .------,

0.5 . 0 .. .. ' . -0.5 ' ..... - - J

-1

-1.5

-2 assuming: 20/o 3.5% ------· 5% -2.5 presmolt survival -3 1965 1970 1975 1980 1985 1990 Year of Return 48 Figure 12. Non-Tahltan stock-recruitmen relationship) 1976-1983 (from eqn [3])

Adult Returns (thousands) 150.-----~~~~~~~~~~~--,

D 100 D

D optimal

oL:__~~-L-~~~~~--L-~~~ 0 20 40 60 80 Escapement (thousands) 49

Figure 13. Sibling forecast method for Tahl tan sockeye ( eqn [6])

Return (Year t+1) (thousands)

o Total Returns * Age 5 Returns ~ 100

0 *

age 5 50 0

oL--~~___._~~~---L-~~~_.______.* 0 5 10 15 Age 4 Return (Year t) (thousands) 50

Figure 14: Trends in Tahltan sockeye smolt survival

Number of Fish (thousands)

Tahltan Returns A 160 Non-Tahltan Returns Talhtan Escapement

120

Prop. Tahltan Prop. Surviving

Prop. Tahltan In Run B 1 Observed Survlval 0.15 Calculated Survlval

0.1

0.5

0.05

09~7-5~~--'-~~~_.__~~--'-~~-1-9~8-3__. 0 ,~ 1977 1979 1981 Brood Year 51

Appendix 1. Sunmary of Canadian Indian food fishery catches of Pacific salmon and steelhead in the upper Stikine River (Telegraph Creek area) from 1972 to 1989.

YEAR CHINOOK SOCKEYE COHO PINK CHUM STEELHEAD TOTAL JACKS ADULTS

1972 230 0 0 0 0 230 1973 200 3670 0 0 0 0 3870 1974 3500 0 0 0 0 3500 1975 1024 1982 5 0 0 0 3011 1976 924 2911 0 0 0 0 3835 1977 100 4335 0 0 0 0 4435 1978 400 3500 0 0 0 0 3900 1979 850 3000 0 0 0 0 3850 1980 587 2100 0 0 0 0 2687 1981 740 5304 8 144 0 4 6200 1982 618 4948 40 60 0 0 5666 1983 1066 4649 3 77 26 46 5867 1984 702 5327 1 62 0 2 6094 1985 94 793 7287 3 35 4 9 8225 1986 569 1026 4208 2 0 12 2 5819 1987 183 1183 2979 3 0 8 2 4358 1988 206 1170 2177 5 0 3 3 3564 1989 115 1078 2360 6 0 0 0 3559 averages: 1972-89 852 3582 4 21 3 4 4371 1985-89 233 1050 3802 4 7 5 3 5105

notes: a) jacks not segregated from 1975 - 1985; b) the 1972 to 1989 chinook average includes jacks. 52

Appendix 2. Sunmary of Canadian coamercial gillnet catches of Pacific salmon and steelhead in the lower Stikine River from 1 9 7 9 to 1989.

YEAR CHINOOK SOCKEYE COBO PINK CHUM STEELBEAD TOTAL DAYS BOAT AVER. NO. JACKS ADULTS FISHED DAYS FISHERMEN

1979 63 712 10534 10720 1994 424 264 24711 42 756 1980 1488 18119 6629 736 771 362 28105 41 668 17 1981 664 21551 2667 3713 1128 280 30003 32 522 16 1982 1693 15397 15904 1782 722 828 36326 71 1063 15 1983 430 492 15857 6170 1043 274 667 24933 54 434 8 1984 1985 91 256 17093 2172 2321 532 231 22696 22.5 145.5 6 1986 365 806 12411 2278 107 295 192 16454 13.5 239 18 1987 242 909 6138 5728 646 432 217 14312 20 287 14 1988 201 1007 12766 2112 418 730 258 17492 26.5 320 12 1989 157 1537 17179 6092 825 674 127 26591 23 325 14

averages: 1979-89 1111 14705 6047 1359 598 343 24162 35 476 13 1985-89 211 903 13117 3676 863 533 205 19509 21 263 13

notes: a) jacks not segregated from 1980 - 1982; c b) the 1979 - 1989 chinook average = total chinook catch, ie. includes jacks; c) the 1979 to 1989 average excludes 1984, the year when the fishery was closed for the season due to poor retums. 53

Appendix 3. Sumnary of Canadian coamercial gillnet catches of Pacific salmon and steelbead in the upper Stikine River (Telegraph Creek area) frcm 1975 to 1989.

YEAR CHINOOK SOCKEYE COHO PINK CHUM STEELBEAD TOTAL DAYS BOAT AVER. NO. JACKS ADULTS FISHED DAYS FISHERMEN

1975 178 270 45 0 0 0 493 1976 236 733 13 0 0 0 982 1977 62 1975 0 0 0 0 2037 1978 100 1500 0 0 0 0 1600 1979 0 1980 156 700 40 20 0 0 916 1981 154 769 0 0 0 0 923 5 11 2 1982 76 195 0 0 0 0 271 4 8 2 1983 75 614 0 0 4 1 694 8 10 1 1984 0 0 0 0 1985 62 1084 0 0 0 0 1146 6 14 2 1986 41 104 815 0 0 0 0 960 7 19 3 1987 19 109 498 0 0 19 0 645 7 20 3 1988 46 175 348 0 0 0 0 569 6.5 21.5 3 1989 17 54 493 0 0 0 0 564 7 14 2 averages: 1975-89 128 769 8 2 2 0 787 6 13 2 1985-89 31 101 648 0 0 4 0 777 7 18 3

notes: a) jacks not segregated frcm 1975 - 1985; b) the 1975 to 1989 chinook average ; total chinook catch, ie. includes jacks; c) the 1975 to 1989 average excludes 1979 and 1984. In 1979, the upper Stikine coamercial catch data was included with lower Stikine data; in 1984, the coamercial fishery was closed. 54

Appendix 4. Sunmary of annual U.S. gillnet catches in District 108 from 1960 to 1989. (catches for 1989 are preliminary).

YEAR CHINOOK SOCICEYE COHO PINK CHUM TOTAL MAX# DAYS BOAT JACKS ADULTS BOATS/WK FISHED DAYS

1960 7824 13635 27479 5584 8189 62711 69 61 1961 7243 21557 36858 52295 12535 130488 62 63 1962 7491 27514 38386 36325 20290 130006 78 57 1963 2107 9995 11697 10340 11155 45294 43 71 1964 2911 20299 29388 114555 10771 177924 70 62 3416 1965 3106 21419 8301 4729 2480 40035 39 48 960 1966 4516 36710 16493 61908 17730 137357 57 62 1841 1967 6372 29226 6747 4713 5955 53013 57 40 1193 1968 4604 14594 36407 91028 14537 161170 89 61 3114 1969 5023 19210 5823 11884 2312 44252 47 37 858 1970 3207 15120 18403 20523 12305 69558 44 41 1180 1971 3717 18143 14876 21806 4665 63207 42 42 892 1972 9332 51734 38520 17153 17363 134102 71 49 1922 1973 9254 21387 5837 6585 6680 49743 74 21 1042 1974 8199 2428 16021 4188 2107 32943 65 16 550 1975 1534 1 1535 49 8 n/a 1976 1123 18 6056 722 124 8043 35 10 130 1977 1443 48374 14405 16253 4233 84708 54 19 740 1978 531 56 32650 1157 1001 35395 54 12 608 1979 91 2158 234 13478 1064 17025 17 5 100 1980 631 14053 2946 7224 6910 31764 24 22 327 1981 283 8833 1403 1466 3594 15579 27 9 177 1982 1033 6886 19971 16988 741 45619 39 21 508 1983 47 178 15484 4171 675 20555 26 17 266 1984 14 1290 5141 4960 1892 13297 8 5 34 1985 20 1060 1926 5325 1892 10223 10 14 50 1986 102 4185 7439 4901 5928 22555 13 25 216 1987 19 149 1620 1015 3331 949 7083 10 13 81 1988 206 1246 12 144 3109 4717 11 8 60 1989 308 10085 4261 27640 3375 45669 15 29 223 averages: 1960-88 3176 14747 14997 19419 6248 56893 44 32 811 1985-89 157 3639 2931 8268 3051 18049 12 18 126 55

Appendix 5. Sumnary of annual gillnet catches in U.S. District 106-41,42, ie. S1111111er Strait, from 1961 to 1989. (1989 catches are preliminary).

YEAR CHINOOK SOCKEYE COHO PINK CHUM TOTAL MAX I DAYS BOAT BOATS/WK FISHED DAYS

1961 75 9471 1851 26435 9657 47489 14 1962 131 19692 6548 45987 9544 81902 31 1963 310 45305 15727 135503 50380 247225 80 1964 316 52943 27338 183402 22913 286912 72 49 2344 1965 679 58736 30570 162271 15763 268019 65 50.75 1658 1966 690 65721 30792 96287 24235 217725 63 74.25 2080 1967 668 60148 10573 52284 19626 143299 71 27 1463 1968 1010 50212 46111 82012 39001 218346 95 52 2997 1969 747 46282 6557 92102 6395 152083 52 31 1147 1970 420 26812 15153 29102 18092 89579 40 41 905 1971 671 33991 24727 283739 19329 362457 103 50 1619 1972 1747 74745 60827 40644 46511 224474 81 41 2152 1973 1540 55254 24921 160297 62486 304498 117 26 2253 1974 1342 46760 28889 57296 38045 172332 126 28 1579 1975 467 19319 4650 29340 7762 61538 71 17 515 1976 237 9319 10367 20251 2301 42475 65 19 366 1977 202 47408 1819 51038 4240 104707 39 17 447 1978 274 1422 26762 9546 3142 41146 51 26.5 389 1979 458 34807 12087 176395 16816 240563 67 25 952 1980 205 48430 10826 16966 15162 91589 55 16 596 1981 598 132359 13158 218359 25994 390468 93 25 1732 1982 648 121220 21387 10343 11896 165494 91 22 1083 1983 268 28153 41196 74347 13001 156965 72 32 875 1984 136 27372 19124 99807 28461 174900 38 32 587 1985 549 172088 50655 319379 45566 588237 98 38 1726 1986 421 85247 104328 105347 48471 343814 103 32 1896 1987 441 79165 17776 117059 25877 240318 83 20 978 1988 452 57337 6349 10894 42210 117242 75 18 815 1989 581 107886 55671 418044 40156 622338 68 34 1716 averages: 1961-88 561 53919 23967 96658 24031 199136 72 32 1326 1985-89 489 100345 46956 194145 40456 382390 85 28 1426 56

Appendix 6. Sunmary of annual gillnet catches in U.S. District 106-30, ie. Clarence Strait, from 1961 to 1989. (1989 catches are preliminary).

YEAR CHINOOK SOCKEYE COBO PINK CHUM TOTAL MAX I DAYS BOAT BOATS/WK FISHED DAYS

1961 326 10967 12839 97762 51875 173769 61 1962 1177 27341 35728 210633 49575 324454 139 1963 1250 35462 36376 379093 39723 491904 129 1964 1766 23598 37316 259684 21305 343669 102 49 3039 1965 1123 29013 45158 463577 11895 550766 118 S0.75 2849 1966 975 24126 32031 304645 16521 378298 100 74.25 2898 1967 650 26237 7097 39325 6744 80053 75 27 1048 1968 306 14459 21040 87095 22365 145265 67 52 1968 1969 289 24061 4191 104998 4511 138050 61 31 1026 1970 365 15966 20317 65790 14139 116577 43 41 1025 1971 665 19211 23358 244236 18351 305821 68 so 1517 1972 826 26593 32600 48823 25871 134713 76 41 1276 1973 391 16741 13526 143324 25243 199225 111 26 1303 1974 696 10482 16825 47041 12258 87302 64 28 712 1975 2120 12732 26312 173675 16206 231045 134 8.S 1159 1976 147 6162 8759 119188 4567 138823 60 21 527 ,,., 1977 469 19615 6582 368069 9060 403795 158 21 940 1978 2408 40152 28816 215169 13403 299948 107 16 1148 \ 1979 2262 31566 15996 471817 18691 540332 147 25 1848 1980 375 58988 5754 28594 11107 104818 98 25 749 1981 967 50546 9453 216909 8577 286452 107 26 1321 1982 1000 72140 10284 15141 6719 105284 88 21 647 1983 299 20789 21234 133820 7143 183285 40 37 589 1984 756 / 64281 22235 243448 41797 372517 53 24 1236 1985 1141 92899 40565 265567 24095 424267 79 36 1372 1986 1283 60462 90584 203137 33818 389284 89 31 1664 '1987 395 57262 16758 126423 16148 216986 74 20 799 1988 652 35186 6754 58605 27410 128607 74 19 682 1989 970 84848 36715 683150 27195 832878 86 34 1588

averages: 1961-88 896 33108 23160 183414 19968 260547 90 32 1334 1985-89 888 66131 38275 267376 25733 398404 80 28 1221