U.S. Dept Commerce/NOAA/NMFS/NWFSC/PublicationsNOAA Technical Memorandum NMFS-NWFSC-20Juvenile Salmonid Stranding in the Lower Columbia River, 1992 and       1993Susan A. Hinton and Robert L. EmmettNational Marine       Fisheries ServiceNorthwest Fisheries Science CenterCoast Zone and       Estuarine Studies Division2725 Montlake Blvd. E.Seattle WA       98112-2097       
December 1994
U.S. DEPARTMENT OF COMMERCERonald H. Brown,       Secretary       
National Oceanic and Atmospheric AdministrationD.       James Baker, Administrator

National Marine Fisheries ServiceRolland A.       Schmitten, Assistant Administrator for Fisheries 
ABSTRACT
Stranding of juvenile salmon (Oncorhynchus spp.) on beaches of the lower Columbia River was studied during April-September 1992 and March-July 1993. Stranding was documented as a significant cause of juvenile salmon mortality by the Washington Department of Fisheries (WDF) in 1974 and 1975 and occurs when the surges and wakes of deep-draft vessels wash fishes onto beaches. Eight sites where stranding had been documented by WDF were studied. Data collected at each site included characteristics of passing vessels (type, speed, surge, and wake height), physical attributes of each beach (slope and distance from the navigational channel), and the number of fishes utilizing the water adjacent to the beach. After a vessel passed a site, the beach was searched for stranded fishes. Eleven stranded fish were found during the study; however, six of these may not have been stranded by passing vessels. Various physical factors such as river-surface elevation, beach slope, vessel design and speed, and the distance between the passing vessel and the beach, and biological factors such as fish condition, may need to interact for stranding of juvenile salmonids to occur. Our observations indicated that stranding of juvenile salmonids is not presently a significant cause of juvenile salmonid mortality in the lower Columbia River. 
CONTENTS- Introduction 
- Methods 
- Sampling 
- Data   Analysis 
- Results 
- Discussion 
- Acknowledgements 
- Citations 
- Appendix   Figures 
- Appendix   Table 1 
- Appendix   Table 2 
- Appendix   Table 3 
INTRODUCTIONIn 1975, an estimated 145,000 chinook (Oncorhynchus tshawytscha), 1,359 coho (O. kisutch), and 4,771 chum (O. keta) salmon, and 537 trout (Oncorhynchus spp.), all juvenile fishes, were stranded on lower Columbia River beaches due to ship wakes from deep-draft vessels traveling in the navigation channel, (Bauersfeld 1977). Stranding occurs when juvenile salmonids, residing or migrating in shallow subtidal habitats, are carried by a ship's wake or surge onto beaches above the normal water line. The water from the wake or surge then recedes or is absorbed quickly on the beach, leaving the fish stranded. Factors that can affect stranding include vessel hull design, draft and speed; channel depth and distance from shore; river height; tide stage; and beach slope, width, and shape. 
Several of the U.S. Army Corps of Engineers' (COE) beach nourishment dredged-material disposal sites have been identified as stranding sites. The COE has 89 designated dredged-material disposal sites between the mouth of the Columbia River and River Kilometer (RKm) 161. In 1992 and 1993 the National Marine Fisheries Service conducted a study to document the extent of juvenile salmonid stranding in the lower Columbia River and the physical attributes of beaches which may contribute to stranding. Eight beach sites where stranding of salmonids had been observed in the past were studied. Four sites are frequently used (within the past 5 years) as COE dredged-material disposal sites and four are infrequently used (not used within the past 5 years).

Our objectives were to determine if stranding was still a serious source of juvenile salmonid mortality and if so determine the causes and recommend ways to eliminate it.
METHODSSamplingFrom April through September 1992 and March through July 1993, eight potential juvenile salmon stranding sites were sampled several times a month (Fig.1., Appendix Figs. 1-8). Sampling consisted of an initial search of a site immediately upon arrival, to find any fishes already on the beach. After a vessel passed the site, an extensive search for stranded fish was initiated by walking as much of the beach as feasible (up to 1.6 km). Occasionally the search was expanded to the opposite shores. Sites were visited during the time of day when the majority of deep-draft vessels were expected to pass by. Vessel schedules were obtained from the Columbia River Bar Pilots Association to minimize field time and maximize observations. Sites were occupied during various tide stages and times of day. 
Data collected during each sampling effort included: date, time, river height, tide stage, estimated vessel speed, vessel direction, size of vessel-caused surge, size of vessel- caused waves, stern position (in or out of the water), type of vessel, and number of fishes stranded. We measured the slopes, widths, and heights of the beaches in August 1992. Five of the sampling sites had both a dredged-material disposal site beach and a "natural" beach in proximity. Both beach types were searched for stranded fish during each sampling effort.

Beach seining was usually conducted at each of the eight sites to document the species, numbers, and sizes of fishes utilizing the water adjacent to the beaches. Three species of Pacific salmon (Oncorhynchus spp.) in the Columbia River system are listed under the Endangered Species Act (ESA) of 1973, necessitating a collection permit prior to any beach seining. In 1992, seining was limited until an ESA permit to collect juvenile salmonids was received in late August. In 1993, beach seining was conducted from March through July.

Figure 1. Eight potential juvenile salmonid stranding sites surveyed along the lower Columbia River, April-September 1992 and March-July 1993.

The seining was done with a 50-m variable mesh (19.0-, 12.7-, and 9.5-mm) beach seine with knotless web in the bunt to reduce descaling of fish. One end of the seine was anchored in dry sand, then using a 5-m boat, the net was fully extended along the shoreline and pulled offshore in a wide arc, completing a half-circle upon returning to the beach. Collected fishes were identified, counted, and a maximum of 50 individuals of each species was measured (total length, TL, in mm) and weighed (g). For salmonids, measurements included TL, fork length (FL), and weight (g). When more than 50 individuals of a species were collected at a site, the excess was counted and weighed as a group. Juvenile salmonids were anesthetized using a benzocaine (ethyl-p-aminobenzoate) solution prior to being measured and weighed.
Data Analysis
For each beach seine effort, individual species and total fish densities (number/ha) and weights (g/ha) were estimated using the catch data and area sampled. The estimated area sampled by the beach seine was 2,540 m2 (Hinton et al. 1990). Two community structure indices were also calculated for each sampling effort. The first was Diversity (H), which was determined using the Shannon-Wiener function (Krebs 1978):

where pi = n i /N (n i is the number of individuals of the i th taxon in the sample, and N is the total number of individuals in the sample) and s = number of taxa. The second community structure index was Equitability (E), which measures the proportional abundances among the various taxa in a sample (Krebs 1978):

where H = Shannon-Wiener function and s = number of taxa. Equitability can range from 0.00 to 1.00, with 1.00 indicating that all taxa in the sample are numerically equal.
RESULTSIn 1992, each of the eight potential juvenile salmonid stranding sites was occupied at least twice between late June and September. In 1993, each site was visited at least three times between late March and early July. We observed 74 (1992) and 71 (1993) deep-draft vessels, most of which produced surges and waves capable of stranding juvenile salmon (Appendix Table 1). One stranded fish was found in 1992 and 10 stranded fish in 1993 (Table 1); however, six of the fishes found in 1993 were already partially decayed and the cause of their stranding could not be attributed to any passing vessel we observed. All the fish we found stranded were juvenile chinook salmon. 
The most common vessels observed during the survey were regular freighters (30%) and car ships (20%) (Fig. 2). About 50% of the vessels were traveling between 22 and 26 km/h (Fig. 3). Stern position, which can have an effect on the size of surges and waves, was most often observed to be in the water. The majority of surges produced by passing vessels were less than 0.25 m in height (54%), and the majority of the waves (47%) were between 0.5 and 1.0 m in height (Fig. 3). Surge and wave height are also affected by beach slope and the distance between the beach and the vessel. Topographies at the eight sites ranged from nearly flat to extremely steep, with several areas having both types (Appendix Figs. 1-8).

Fifteen fish taxa were captured by beach seine during the 1992-93 juvenile salmonid stranding survey (Appendix Table 2). Dominant fishes captured throughout the study included chinook salmon, threespine stickleback (Gasterosteus aculeatus), starry flounder (Platichthys stellatus), peamouth (Mylocheilus caurinus), and coho salmon Appendix Table 3. Fish densities ranged from 43 to 2,248 fish/ha (Table 2. Overall diversity (H) was low, ranging from 0.51 to 2.19 and equitability (E) was moderate, ranging from 0.22 to 0.85. Together H and E indicate few fish species were caught per seine and the numbers of two or more of these species were numerically similar.

Juvenile salmonids were present in 100% of the beach-seine efforts conducted during June-September 1992 and 1993 (Table 3), with densities ranging from 70 to 1,053 salmonids/ha. This indicated that the juvenile salmonids were utilizing the nearshore areas and were therefore potentially exposed to stranding conditions generated by a passing vessel.

All the chinook salmon were juveniles, with most between 45 and 105 mm TL from April through July (Figs. 4, 5). The mean length of these salmonids increased during the sampling season, with few fish less than 75 mm TL by July. Coho salmon captured in April and May 1993 were usually between 140 and 170 mm TL and showed no change in length over the 2-month period (Fig. 6).
Table 1. Lengths and weights of juvenile chinook salmon found on Columbia River beaches, 1992 and 1993. DateRKmTotallength(mm)Fork length(mm)Wt.(g)8 Jul 92148.180735 13 Apr 9396.13332115 Apr 93129.2*11911014*46421*423814238123 Apr 93148.1*74684*464214542130 Apr 9396.1*5652218 May 9374.550471* Fish were partially decayed, cannot attribute presence to any passing vessel. Figure 2. Types of vessels observed passing the eight potential juvenile salmonid stranding sites surveyed along the lower Columbia River in 1992 and 1993. Figure 3. Characteristics of vessels and their associated wakes observed while passing potential juvenile salmonid stranding sites along the lower Columbia River, 1992 and 1993. One hundred and forty-five vessels were observed. Table 2. Summary of fish catches during the stranding survey at eight sites along the Columbia River, 1992 and 1993. RKm Date No./ha Wt. (g/ha) H(a) E(b)199261.617 Sep 2,2487,5081.69 0.7317 Sep 823 6,013 1.06 0.4174.5 11 Jun 898 8,433 0.80 0.34148.118 Sep 79 2911.54 0.77199361.6 14 Apr 269 -c 1.83 0.6514 May 367- 1.59 0.5314 May 1,268 - 0.59 0.2324 Jun1,0673,8811.680.5674.5 29 Apr 815 2,969 1.14 0.4418 May 556 31,449 1.86 0.669 Jun29212,267 1.92 0.6882.6 28 Apr 440 - 1.23 0.6225 Jun 1655350.700.7091.7 7 May 1,622- 2.19 0.692 Jun 1,308 - 0.88 0.292 Jul 1,319 48,355 1.30 0.4696.113 Apr 107 - 1.700.8530 Apr 178 12,519 1.66 0.599 Jun47354,4692.120.71129.215 Apr431221.100.6912 May697-0.900.39139.816 Apr7361,8590.510.226 May590- 1.40 0.60148.1 23 Apr 107 1,323 1.05 0.4527 Apr 301 9,166 1.62 0.54(a)Diversity.(b)Equitability.(c)no weights were recorded.DISCUSSIONIn 1974 and 1975, juvenile salmonid stranding caused by deep draft vessels was a notable source of mortality, with daily estimates at some Columbia River beach sites as high as 117 fish per vessel (Bauersfeld 1977). However, in 1992 and 1993, only five juvenile salmonids were found stranded in association with passing deep-draft vessels. It is unclear why so few fish were stranded in 1992 and 1993. 
The stranded fishes found in 1974 and 1975 may have been influenced by dissolved gas supersaturated river water, caused by spilling of water at upstream hydropower dams. In 1974 and 1975, river flows and the dissolved gas saturation values were higher than those observed during our survey (Fig. 7). Dissolved gas levels above 106% decrease juvenile chinook salmon swimming performance (Schiewe 1974). In 1975, dissolved gas levels in the Columbia River were above 106% at Prescott, Oregon (RKm 115) from 22 April through 15 July (Park et al. 1976). Fishes stranded during this period (peak migrational period) may have been weakened by the high dissolved gas concentrations and therefore became susceptible to stranding.

Stranding also can occur during low flow years (Earl Dawley, NMFS, Northwest Fisheries Science Center, Seattle, WA pers. commun.). Dawley observed stranding of large numbers of subyearling chinook salmon (approximately 20 to 100 fish) three different times in 1977, after a large vessel passed Jones Beach, Oregon (RKm 75). Dawley also observed about 200 subyearling chinook salmon stranded at one time during a low tide in 1984 at Jones Beach, Oregon. Dawley believes that most of these stranded fish had been recently released from a hatchery and were not physiologically prepared for migration.

Although juvenile salmon can become stranded on beaches along the lower Columbia River, it presently does not appear to be a common event. Apparently, many factors must act simultaneously for stranding to occur. Vessel speed and shape, distance of vessel from beach, tide stage, beach slope, salmon abundance and condition, and river flow conditions, in any combination may have to interact for salmon to become stranded. In 1977, the Washington Department of Fisheries made four recommendations that we believe are generally being followed today.
- All dredge disposal berms facing the navigation channel shall be contoured   with a minimum 9% gradient immediately after disposal.     
- 1 March to 30 June - All deep draft ships shall travel less than 26 km/h   from RKm 33.7 to RKm 162.5.     
- 1 July to 31 July - All deep draft ships shall travel less than 26 km/h   from RKm 33.6 to RKm 109.4 from 10 p.m. through 6 a.m. each day.     
- 1 March to 31 July - If Columbia River stage continually ranges above 2.1   m as measured at the Rainier, Oregon gauge, the above recommendations would   not apply.     
Though stranding is presently not a serious problem on the lower Columbia River, fishery resource agencies should occasionally survey lower Columbia River beaches during the peak juvenile salmon migration to insure that vessels are complying with the above guidelines and salmon are not stranded. Table 3. Summary of salmonids captured by beach seine at the eight potential juvenile salmonid stranding beaches along the Columbia River, June-September 1992 and April-July 1993. All salmonids (chinook salmon, coho salmon, steelhead, cutthroat trout) were combined for each beach seine. When more than one beach seine was made, the no./ha values are means. Sampling period RKm No. of seine effortsFrequency of occurrence (%)Density (no./ha)            1992June 139.8 1 100 811September 61.6 2 0 -74.51 0 -1993April/May 61.6 3 1007074.52 100 19582.61 100 39791.71 100 82396.12 10087129.2 2 100 360139.82 100612148.12100160Mean2 100 338June/July 61.6 1 100 28774.51 1008782.6 1 100 13491.7 2 100 1,05396.1 1 100256*129.2 1 100339*148.1 1 100 602Mean1 100 345*Seine efforts were made on shore opposite from original site Figure 4. Length frequency distribution of juvenile chinook salmon captured by beach seine in the Columbia River, June 1992. Figure 5. Length frequency distributions of juvenile chinook salmon captured by beach seine in the Columbia River, 1993. Figure 6. Length frequency distributions of juvenile coho salmon captured by beach seine in the Columbia River, 1993.Figure 7. Average daily spill (kcms) and dissolved gas readings (%saturation) at Bonnevile Dam. Saturation values for 1974 and 1975 are single readins; 1992 and 1993 saturation values and flow values for all years are 24-hour means. ACKNOWLEDGMENTSWe thank Sheila Turner, Beverly Heskiss, Margaret Toner, and George McCabe, Jr., for their assistance in data collections, and the Columbia River Bar Pilots Association for providing vessel identifications and schedules. Funding for this study was provided by the NMFS-COE Habitat Restoration Program. CITATIONS- Bauersfeld, K. 1977.   
- State of Washington Dep. of Fisheries Tech. Rep. No. 31. Effects of   peaking (stranding) of Columbia River dams on juvenile anadromous fishes below   The Dalles Dam, 1974 and 1975. Report to the U.S. Army Corps of Engineers,   Contract DACW 57-74-C-0094, 32 p. plus appendices. (Available from U.S. Army   Corps. of Engineers, Portland District, P.O. Box 2946, Portland OR 97208.)   
- Hinton, S. A., G. T. McCabe, Jr., and R. L. Emmett. 1990.   
- Fishes, benthic invertebrates, and sediment characteristics in intertidal   and subtidal habitats at five areas in the Columbia River estuary. Report to   the U.S. Army Corps of Engineers, Contracts E86880158, E8690107, E86900048, 92   p. plus appendices. (Available from Northwest Fisheries Science Center, 2725   Montlake Blvd E., Seattle WA 98112.)   
- Krebs, C. J. 1978.   
- Ecology: The experimental analysis of distribution and abundance. Harper   Row, New York, 678 p.   
- Park, D. L., E. M. Dawley, R. F. Krcma, C. W. Long, E. Slatick, J. R.   Smith, and G. A. Swan. 1976.   
- Evaluation of fish protection facilities at Little Goose and Lower Granite   Dams and review of other studies relating to protection of juvenile salmonids   in the Columbia and Snake Rivers, 1975. Final Report to U.S. Army Corps of   Engineers, Contract DACW68-75-C-0111, 50 p. plus appendices. (Available from   Northwest Fisheries Science Center, 2725 Montlake Blvd E., Seattle, WA 98112.)   
- Schiewe, M. H. 1974.   
- Influence of dissolved atmospheric gas on swimming performance of juvenile   chinook salmon. Trans. Am. Fish. Soc. 103(4):717-721.     
APPENDIX FIGURESAppendixFigure       1.AppendixFigure       2.AppendixFigure       3.AppendixFigure       4.AppendixFigure       5.AppendixFigure       6.AppendixFigure       7.AppendixFigure       8.APPENDIX TABLES
Appendix Table 1--Summary of vessels and their characteristics, observed during the juvenile salmonid stranding survey, April-September 1992 and March-July 1993.

Appendix Table 2--Fish taxa captured by beach seine at potential juvenile salmonid stranding beaches along the Columbia River, June-September 1992 and March-July 1993.

Appendix Table 3--Summaries of individual fishing efforts (by station) conducted during June-September 1992 and March-July 1993 at eight beaches selected as potential stranding sites along the Columbia River. A dash (-) indicates the data was not recorded. Diversity (H) and Equitability (E) are also presented for each effort.