DISTRIBUTION AND SEASONAL ABUNDANCE OF JUVENILE SALMON AND OTHER FISHES IN THE YUKON DELTA by Douglas J. Martin Clifford J. Whitmus and Lon E. Hachmeister Envirosphere Company 10900 N.E. 8th Street Bellevue Washington 98004 Eric C. Volk and Steven L. Schroder Washington Department of Fisheries Rm. 115, General Administration Building Olympia, Washington 98504 Final Report Outer Continental Shelf Environmental Assessment Program Research Unit 660 July 1987 123 The completion of this study could not have been accomplished without the aid of many individuals and organizations. We wish to thank all of the field team members including: Messrs. Richard Tyler, Dan Tyler, Clarke Beaudry, and Ms. Allison Reak. We also thank the ADF&G crew at Pilot Station for providing fish samples and Messrs. Larry Buklis and Jim Raymond (ADF&G) for providing supporting information concerning Yukon salmon. Special thanks to Mr. Calvin Van Zee, Envirosphere Company, for his assistance in obtaining and processing satellite images. We are especially grateful to Mr. Jake Johnson and staff of the Emmonak Fisheries Cooperative for their generous assistance in repairs of field equipment. Logistical support was provided by the NOAA/OAD Helicopter Group, from Miami, Florida, and staff of the NOAA/Ocean Assessment Division, Anchorage. Special thanks to Messrs. Carl Anderson and Michael Meyer from NOAA for their concern and assistance in helping to make the job a little easier. We also thank Dr. David Carneggie and Mr. Michael Fleming, EROS Anchorage Field Office, U.S. Geological Survey, for providing the AVHRR digital tapes. This study was funded in part by the Minerals Management Service, Department of the Interior, through an interagency agreement with the National Oceanic and Atmospheric Administration, Department of Commerce, as part of the Alaska Outer Continental Shelf Environmental Assessment Program. 125 ABSTRACT The purpose of this study was to identify the importance of aquatic habitdt$ in tne Yukon River Delta for juvenile salmon and otner fishes, and to determine the vulnerability of these fish to the pOtentiiIl inp<acts of an oil spill. An investigation was conducted of the distributary cnannels, nearshore, and shallow offsnore naDitats to determine the outmigrdtion timing, distribution, and seasonal abundance of juvenile salmon and other fishes in the Yukon River Delta. Fisheries and oceanographic data were collected from three surveys that began immediately following ice breakup (i.e., early June) and ended in mid-,4ugust 1986. Results indicated that outmigrat on of juvenile chinook salmon ~nd chum salmon began before ice breakup. Chinook salmon smelts peaked on :,e’veral ,dates during June and Ju” y With the largest CatCneS Occurr”ng during late June. The peak timing of the juvenile chum salmon o!]t:nigr~tion occur’s during the mid to latter part of [June. Low numbers (of both ~pecies continued to outmigrate during the rest of the summer. The lengths of all outmigrant chinook salmon exceeded 69 mm, whicn suggests that most srnolts ‘were ag? 1+. Outmigrant chum fry were comprjseq different size groups with average lengths ranging of t~r~e from 36 mm to 60 mm. C!I~nOOK and cnum .juv.~n 1P5 uti ized tne, outer delta front and delta pldtforim habitats to a great?r extent tnan tne nearshore intertidal snvironnent. lJtilizat on of t’ dal slougn and inudflat nabitats were intermittent and rest~ Cte,i to regions near major distributary channels, whereas utilization of the offshore habitats was constant and relatively uniform along the delta front. There was no difference in the average size or size composition of juvenile salmon in lower river and otner hai>i tats which suggests that outmigrants were not residing in the shallow delta environment. Tne results ndicate that the lower river, intertidal habitats, delta platform, and delta front are not utilized as a nursery area but rather as a migrat” on corridor for juvenile Sdlrlon. Juvenile salmon that migrate through tne delta front are most likely moving to deeper estuarine habitats in the prodelta. 127 The migratory routes through the delta and the utilization of delta habitats by juvenile salmon are thought to be influenced by the unique physiographic conditions. The network of sub-ice channels and the ldrge river discharge carry juvenile salmon across the delta platform and distribute them along the delta front. Estuarine conditions that may be important rearing habitat exist only at the delta front and seaward as a result of the massive freshwater plume. Peak outmigration of juvenile coregonid fishes occurred during July. Juvenile cisco were approximately three times more abundant than juvenile sheefish and juvenile whitefish. Intertidal mudflats and tidal sloughs are the most important habitats for these species. Populations of .juveni e salmon would be vulnerable to an oil spill in the offshore habitats and in the migration corridor. Outmigrants that mdy utilize tne prodelta would be the most vulnerable to oil impacts because this habitat is located within the OCS lease area of Norton %[jnd . Sheefish, wnltefish, and cisco populations would be highly vulnerable to an oil spill that reached the nearshore environment. 128 TABLE OF CONTENTS Page ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...125 ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...127 LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...127 LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...131 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...135 2. METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...138 2.1 DESCRIPTION OF STUDY AREA. . . . . . . . . . . . . . . . . . . . . . . . . . . ...138 2.2 SAMPLING PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...140 2.3 SAM PLING TECH PIQUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...144 2.3.1 Water Quality and Physical Measurements . . . . . . . . . . . . ...144 2.3.2 Fish Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...145 2.3.3 Catch Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...148 2.4 ANALYTIC PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...148 2.4.1 Hydrographic Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...148 2.4.2 Data Recording and Archival. . . . . . . . . . . . . . . . . . . . . . . . ...151 2.4.3 Run Timing, Relative Abundance and Density . . . . . . . . . . ...152 2.4.4 Size Composition and Growth. . . . . . . . . . . . . . . . . . . . . . . ...153 2.4.5 Associated Environmental Conditions . . . . . . . . . . . . . . . . ...155 2.5 CHUM SALMON OTOLITH STUDY.... . . . . . . . . . . . . . . . . . . . . . . ...155 2.5.1 Sample Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 2.5.2 Laboratory Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...156 . 3. RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...157 3.1 WATER QUALITY AND PHYSICAL MEASUREMENTS . . . . . . . . . ...157 3.1.1 Discrete Physical Measurements . . . . . . . . . . . . . . . . . . . . . ...157 3.1.2 River Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...158 3.1.3 Hydrographic Characterization . . . . . . . . . . . . . . . . . . . . . . . ...158 3.2 CATCH SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171 3.2.1 Effort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...171 3.2.2 Species Composition and Distribution . . . . . . . . . . . . . . . . ...175 TABLE OF CONTENTS (Continued) Page 3.3 CHINOOK SALMON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...177 3.3.1 Migration Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 3.3.2 Distribution and Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...177 3.3.3 Size Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180 3.3.4 Associated Environmental Conditions . . . . . . . . . . . . . . . . ...184 3.4 CHUM SALMON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...184 3.4.1 Migration Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 3.4.2 piSt.ribWlp~ and Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...191 3.4.3 SiZe Composition a m.,...... . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 3.4.4 Associated Erwimtimental Conditions . . . . . . . . . . . . . . . . ...195 3.4.5 Otoli+h M4crostruc$ureand increment Periodicity . . . . . . . ...202 3.4.6 Residency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 3.4.7 Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...210 3.5 OTHER FISHES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...210 . 3.5.1 Migraticm Tinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213 3.5.2 Distribut4an and Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 4. DISCUSSION . . . . . . . % . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219 4.1 CHINOOK SALtiQN, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219 4.1.1 Outmigratkm” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 4.1.2 Distribution and tlabitat Utilization . . . . . . . . . . . . . . . . . . . ...222 4.1.3 Resick%@y.., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...225 4.2 CHUM !3ALMQN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 4.2.1 Outmlgratkm.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226 4.2.2 Distrib#ti@ and t-+labitat Utilization . . . . . . . . . . . . . . . . . . . ...229 4.2.3 Determining Residency With Otoliths . . . . . . . . . . . . . . . . . ...231 4.2.4 Residency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .234 4.2.5 Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...235 4.3 VULNERABILITY TO OIL AND GAS DEVELOPMENT . . . . . . . . . . ...235 5. REFERENCES CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...239 APPENDIXA. Water Quality Data and Physical Conditions During Summer 1986 in the Yukon River Delta . . . . . . . . . . . . . . . . ...247 APPENDIXB. Fish Catch and Fish Length Statistics Groupedby Specie~Station, and Date for the 1986 Summer Survey of the Yukcm F?iver Delta.. . . . . . . . . . . . . . . . . . . . . . . . . . . . ...251 AP#ENDtXC. Length Frequency of Juvenile Chum Salmonby Staticmand Tirrie Period During Summer 1986.............271 . .. ‘. 1 30 LIST OF FIGURES Figure Page 2-1 Vicinity map of Norton Sound showing the location of the Yukon River Delta study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...139 2-2 Depositional environments of the modern lobe of the Yukon Delta . . ..l4l 2-3 Location of sample sites for thesummer 1986 survey of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...143 2-4 Location of study area andsample stations included in the analysisof hydrographic properties in the Yukon River Delta . . . . . . ...150 3-1 Yukon River discharge at Pilot Station during summer 1985 and 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...159 3-2 Vertical sections of salinity fortheon/offshore direction and the along-shore direction, and horizontal contours of surface saiinity distribution and sources of freshwater inputto the area for the June 12, 1986 survey of the Yukon River Delta.... . . . . . . . . ...160 3-3 Vertical sections of salinity fortheon/offshore direction and the along-shore direction, and horizontal contours of surface salinity distribution and sources of freshwater input to the area for the June 15, 1986 survey of the Yukon River Delta . . . . . . . . . . . . ...162 3-4 NOAA AVHRR satellite imagery of the Yukon River Delta, approximate scale l:3million, June 15, 1986 . . . . . . . . . . . . . . . . . . . . ...164 3-5 NOAA AVHRR satellite imagery of the Yukon River Delta, approximate scale l:l.5 million, June 15,1986 . . . . . . . . . . . . . . . . . . ...166 3-6 NOAA AVHRR satellite imagery of the Yukon River Delta, approximate scale l:750,000, June 15,1986 . . . . . . . . . . . . . . . . . . . . . ...168 3-7 Vertical sections of salinity fortheon/offshore direction and the along-shore direction, and horizontal contours of surface salinity distribution and sources of freshwater input to the area for the June 19, 1986 survey of the Yukon River Delta.... . . . . . . . . ...170 3-8 Vertical sections of salinity fortheon/offshore direction and the along-shore direction, and horizontal contours of surface salinity distribution and sources of freshwater input to the area for the August 6, 1986 survey of the Yukon River Delta . . . . . . . . . . . ...172 3-9 Catch per unit effort of juvenile chinook salmon during summer 1986 from the lower river, stations 13 and 17, of the Yukon River Delta.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...178 131 LIST OF FIGURES (Continued) Figure Page 3-1o Length frequency of juvenile chinook salmon by time period during summer 1986 from the lower river stations 13 and 17, of the Yukon River Delta.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...181 3-11 Length frequency of juvenile chinook salmon during the period June 12-15, 1986 from the Iowerriver, delta platform, and the delta front habitats of the Yukon River Delta . . . . . . . . . . . . ...183 3-12 Length frequency of juvenile chinook salmon during the period June 12-15, 1986 from thedelta front, stations 1,2, and 3,0 fthe Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...185 3-13 Length frequency of juvenile chinook salmon during the period June 12-15, 1986 from the delta platform, stations 4,5, and60fthe Yukon River Delta. . . . . . . . . . . . . . . . . . . . . . . . . . . . ...186 3-14 Catch per unit effort of juvenile chum salmon during summer 1986 from the lower river, stations 13 and 17, of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...190 3-15 Length frequency of juvenile chum salmon by time period during summer 1986 from the lower river, stations 13 and 17, of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...193 3-16 Length frequency of juvenile chum salmon during the period June 12-15, 1986 from offshore, tidal slough, and lower river habitats of the Yukon River Delta.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...196 3-17 Length frequency of juvenile chum salmon during the period June 17-20, 1986 from offshore and lower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...197 3-18 Length frequency of juvenile chum salmon during the period July 7-14, 1986 from offshore and Iower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...198 3-19 Posthatching otolith increment frequency for chum salmon collected during summer 1986 from the Yukon River Delta . . . . . . . . ...203 3-20 Regression of posthatch otolith increment number on length of chum salmon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204 3-21 Frequency histograms and statistics of otolith increment widths for sixteen outer increments from chum salmon caught in the delta platform anddelta front of the Yukon River Delta . . . . . . . . . . ...208 3-22 Plot of length with time forjuvenile chum salmon caught in the lower Yukon River during summer 1986, . . . . . . . . . . . . . . . . . . . ..2l2 3-23 Catch perunit effort ofjuvenile sheepish, juvenile whitefish, and juvenile cisco during summer 1986 from the lower river station 17,0 fthe Yukon River Delta. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214 132 LIST OF TABLES Table Page 2-1 Location and description of stations sampled during the 1986 field season of the Yukon Delta study . . . . . . . . . . . . . . . . . . . . . ...142 2-2 Specifications for fish sampling gear used for the summer 1986 survey of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . ...146 2-3 Comparison of species composition and catch statistics for the purse seine and tow net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...147 2-4 Estimates of towing speed, area sampled, and volumeof water sampled during typical 10-minute hauls with a 1.8 mand6.8m tow net..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...154 3-1 Summary of sampling effort for beach seine and purse seine gear during the summer 1986 survey of the Yukon River Delta . . . . . . ..173 3-2 Summary of sampling effort for tow net during the summer 1986 survey of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . ...174 3-3 Number of fish caught by species and habitat during summer 1986 in the Yukon River Delta. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...176 3-4 Estimated average density of juvenile chinook salmon during summer 1986 in the offshore, coastal, and lower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...179 3-5 Percentage adjusted catch of chinook salmon associated with surface and bottom temperature in the delta front and delta platform habitats of the Yukon River Delta during June 12-19, 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...187 3-6 Percentage adjusted catch of chinook salmon associated with surface and bottom salinityin the delta front and delta platform habitats of the Yukon River Delta during June 12-19, 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...188 3-7 Percentage adjusted catch of chinook salmon associated with water visibility in the delta front and delta platform habitats of the Yukon River Delta during June 12-19, 1986...........189 3-8 Estimated average density of juvenile chum salmon during summer 1986 in the offshore, coastal, and lower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...192 133 LIST OF TABLES (Continued) Table Page 3-9 Percentage adjusted catch of chum salmon associated with surface and bottom temperature in the delta front and delta platform habitats of the Yukon River Delta during June 12-19, 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...199 3-1o Percentage adjusted catch of chum salmon associated with surface and bottom salinity in the delta front and delta platform habitats of the Yukon River Delta during June 12-19,1986 . . . . . . . . ...200 3-11 Percentage adjusted catch of chum salmon associated with water visibility in the delta front and delta platform habitats of the Yukon River Delta during June 12-19, 1986...........201 3-12 Results of t-tests on fish length and otolith increment number, and estimated increment periodicity for chum salmon from the fish holding experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 3-13 Mean and 95 percent Cl. of otolith increment number for juvenile chum salmon by habitat and results of a multiple range test on increment number among habitats . . . . . . . . . . . . . . . . . . . . . . . . 211 3-14 Estimated average density of sheefish during summer “ 986 in the offshore, coastal, and lower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 3-15 Estimated average density of whitefish during summer 1986 in the offshore, coastal, and lower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...216 3-16 Estimated average density of cisco during summer 1986 in the offshore, coastal, and lower river habitats of the Yukon River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...217 3-17 Estimated average density of boreal smelt, smelt sp., and Pacific herring during summer 1986 in the delta front and delta platform habitats of the Yukon River Delta . . . . . . . . . . . . . . . . ...218 4-1 Outmigration timing and size at outmigration of chinook salmon smelts from the Yukon River drainage . . . . . . . . . . . . . . . . . . . . .220 4-2 Outmigration timing and size at outmigration of chum salmon smelts from the Yukon River drainage . . . . . . . . . . . . . . . . . . . . .227 4-3 Sizes of chum salmon juveniles in estuarine habitats . . . . . . . . . . . . ...232 4-4 Growth rate of juvenile chum salmon in freshwater . . . . . . . . . . . . . . ...236 134