News and Short Contributions Special Studies

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News and Short Contributions

Special Studies Radiographic Age Determination of Pacific provides a basis for inferring the probable species com- Salmon: Species and Seasonal Inferences position of a site assemblage. Within particular species of AUBREY CANNON salmon, the vast majority of fish spawn at specific ages. The presence or absence of salmon of those age classes University of Toronto Toronto, Ontario within a recovered archaeological assemblage provides a basis for assessing the presence or absence of associated Radiographs are used to age archaeologically-recovered vertebrae of species. It is otherwise impossible to differentiate Onco- Pacific salmon (Oncorhynchus sp.). In application, the method rhynchus provides an explanation for observed size variability in vertebrae from species based on the morphology of the majority the site eNamu, on the central coast ofBritish Columbia. The of skeletal elements (D. Cannon 1987: 5), although re- results also provide a means for assessing the species and seasonality of covery and microscopic analysis of otoliths can yield this the Namu salmon fishery and demonstrate a consistency in fishing information (Norden 1961: 790-791; Casteel 1976: 25). patterns during 4000 years esite occupation. Given the specific timing of the spawning runs of different Pacific salmon species, it is possible to assign very specific Introduction dates to seasonal fishing activity based on the frequency of the different salmon species recovered. Other methods Age and growth studies of fish have widespread appli- based on the percentage frequency and estimated season- cation in fisheries research, and they also have been applied ality of a number of different fish species have been pro- in a range of archaeological and paleoenvironmental stud- posed (Leach 1979) and criticized as inadequate (Nichol ies aimed largely at detecting seasonality of prehistoric 1982), but the advantage of using salmon species is that fishing activity or climatic variation affecting growth rates their seasonal presence is in most cases narrowly restricted of fish. Growth increments visible in scales, bones, and to a particular time of year. otoliths provide the basis for these studies. The difficulty in many archaeological situations lies in the recovery and age and growth reading of sufficient numbers of fish re- Method and Evaluation mains to produce reliable average age and growth esti- In many fish, growth annuli on the surface of vertebrae mates. Seasonal growth readings are further complicated are clearly visible under normal or polarized light with the by variation in rates of growth, variation in the timing of naked eye or the aid of a microscope (Casteel 1976: 78- seasonal annulus formation, and potential difficulty in de- 81; Rojo 1987: 220-221). In other cases, annuli are not termining the extent of seasonal growth. clearly visible, and it is impossible to determine age from A number of studies have relied on determinations of simple visual inspection (e.g., Nordeng 1961: 79). seasonal growth in fish remains (e.g., Casteel 1972; Rojo Growth annuli were not clearly visible on the salmon 1987: 220-221), but seasonal readings based on fish bone vertebrae from the Namu excavations, and it was therefore increments necessarily lack precision (Monks 1981: 202). impossible to visually assess the age of the fish represented, The present study is not concerned with determining the even with the aid of a microscope. Alternatives such as extent of seasonal growth in fish remains but is concerned sectioning and polishing of vertebrae to view annuli were with problems of age determination from the numbers of not feasible because of the time and expense this would annuli (annual growth rings) present in the vertebrae of involve. It was impractical to examine in this manner the Pacific salmon (Oncorhynchus sp.). The aim of the partic- several hundred vertebrae necessary to give a statistically ular study described was to account for temporal variation accurate assessment of the Namu salmon age-profile. in the size of salmon vertebrae recovered from over 4000 As an alternative, an experimental attempt was made to years of shell-midden deposits at the site of Namu (EISx- radiographically examine the vertebrae to see if alternating 1), on the central coast of British Columbia (FIG. 1). winter- and summer-growth bands could be distinguished. Age determination of the remains of Pacific salmon For this purpose, the H. G. Fischer model FP200 portable 104 News and Short Contributions

graphically-visible rings were true annuli. The comparison with average weight at the end of the first winter's growth BRITISH COLUMBIA made it possible to distinguish between the first winter- growth check and the smaller, irregular, and narrow bright ring that was often visible within the first annulus. This is the method recommended by Chugunova (1963: 22- 24) as a way of distinguishing the juvenile growth ring that may form within the first year of life as a result of environmental change, as in the departure of young salmon for offshore feeding grounds. The weight of the living fish may be estimated from annuli width via a gen- eralized regression formula describing the relationship between Oncorhynchus sp. fish weight and vertebral width (Casteel 1974: 178). With some experience in the examination of radiographs, age determinations could be made quickly and accurately. In the archaeological study specimens, from one to three winter-growth rings were visible. In a com- 10 9 10 km parative specimen of chinook salmon (0. tshawytscha), five winter rings were visible, indicating a fish that was six years old. An attempt to apply the method to a number Figure 1. Map showing location of the Namu site on the central coast of British Columbia. of different Pacific fish families (e.g., Gadidae, Hexagram- midae, and Pleuronectidae) failed to reveal any radiographically-visible concentric rings that could be inter- preted as growth annuli. The fact that salmon bone is x-ray unit of the Department of Archaeology, Simon generally less dense than that of most other fish may have Fraser University, was used. Vertebrae were placed directly allowed easier passage of x-rays through summer-growth on dental x-ray plates and exposed to a radiographic out- bands, in marked contrast to the radiopacity of the denser put of 70 kvp at 20 ma for 0.5 seconds at a distance of winter-growth bands. In other species of fish, the entire 64 mm. The results showed very clearly an alternating surface of the vertebra was generally much more radio- series of narrow, bright (radiopaque) and wider, dark (ra- paque, making it impossible to distinguish alternating diolucent) bands on the surface of each vertebra (FIG. 2). growth bands. Nevertheless, given the importance of These bands correspond to visible narrow bands of slow salmon to the prehistoric subsistence economies of NW winter growth (denser) and wider bands of more rapid North America, the method has significant archaeological summer growth (less dense). Age determination from potential. Application of the method to the Namu ar- these radiographs was simply a matter of counting the chaeological specimens made it possible to account for bright, narrow bands to determine the number of winter- size variation observed in vertebrae and had further im- growth periods. plications based on the varying life histories of Pacific Using this method, hundreds of vertebrae could be salmon species. checked in very little time, but because the method was experimental a series of checks were made to determine whether the radiographically-visible bands were true an- Species Characteristics and Implications nuli and therefore an accurate basis for age determination. Each of the five Pacific salmon species that spawn in This was done by: 1) examining comparative specimens British Columbia has a distinctive life history. In relation of Oneorhynchus by the same method; 2) comparing ra- to spawning behavior, they are differentiated on the basis diographic age determinations with those based on the of their age at spawning, the range of streams in which annuli visible on scales of comparative specimens; and 3) they commonly spawn, and the specific time of year at comparing weight estimates based on the width of the which their spawning peak occurs. Because Pacific salmon first annulus to known average weights of chum salmon were mostly available to native fishing only at the time of (0. keta) at the end of their first year of growth (Ricker their return to spawning streams, determination of the age 1964). In all cases these checks confirmed that the radio- profile of archaeologically-recovered salmon allows for rea- Journal of Field ArchaeologylVol. 15, 1988 105

(Aro and Shepard 1967: 232). The freshwater systems that flow into the Rivers and Smith Inlets of the central coast are another major producer, accounting for 16% of the combined British Columbia and Washington total (Aro and Shepard 1967: 242). The sockeye salmon that spawn in these central coast systems are evenly divided between four and five-year-old fish, and the peak spawning runs in the region are in July. Chinook salmon (0. tshawytscha) are the largest of the Pacific salmon, and although they can spawn at ages rang- ing from three to eight years, most return to spawn in their fourth or fifth year (Hart 1973: 125). Chinook spawn in relatively few streams (Aro and Shepard 1967: 265) and are now extremely rare in the small streams of Figure 2. Radiograph of Oncorhynchus vertebrae exhibiting: A: one the central coast region (Pomeroy 1980: 175; Rohner winter's growth; B: two winters' growth; and C: three winters' 1967: 45). In central and northern British Columbia, peak growth. spawning is in September (Aro and Shepard 1967: 269). Species characteristics provided the basis for deriving soned inference of the species involved, and, by implica- inferences from the Namu salmon age profile. Although tion, the time of year when fishing took place. the species overlap in spawning ages allows for potential Pink salmon (0. gorbuscha) are easily distinguished on ambiguity in identifications based on an age profile, in the basis of age because they almost invariably spawn at application age determination provided conclusive evi- two years of age (i.e., after one winter's growth). Pink dence for the absence of some species and the likely pres- salmon spawn in substantial numbers in certain streams ence of others, as well as an explanation for observed of the central coast region, and their peak spawning in the variation in vertebra size. region takes place in late September (Aro and Shepard 1967: 282; Hunter 1959: 849). Application Chum salmon (0. keta) spawn at ages varying from two Namu is the site of a major shell-midden accumulation to seven years, but those maturing at less than three years on the central coast of British Columbia (FIG. i) that had or more than five years are insignificant in number (Neave, more or less continuous prehistoric occupation dating Yonemori, and Bakkala 1976: 31). The greatest number back to as early as 10,000 b.p. (radiocarbon years). The of chum reach maturity at four years of age (Hunter 1959: earliest deposits do not contain shellfish, and the resulting 838), although substantial numbers return at three years soil acidity has also prevented the preservation of bone. of age (Henry 1954: 7-10). At present, the central coast The present study is based on material from excavations area produces large numbers of chum salmon, with spawn- conducted in 1978, in which a depth of 4 m of midden ing spread over a wide number of streams (Aro and She- was exposed (Carlson 1979). In the earliest shell-bearing pard 1967: 254,286). Chum salmon enter streams to layers of this deposit, dating from 6500 to 5000 b.p., and spawn a little later than pink salmon (late September or in the later shell-midden deposits, dating from 5000 to early October), with older chum the first to enter the 2200 b.p., the preservation of faunal remains, including stream and the youngest the last to enter (Hunter 1959: tens of thousands of salmon vertebrae, was good. All 837,849). faunal remains were processed and identified, and the In British Columbia, 95% of coho salmon (0. kisutch) salmon vertebrae from one 2 m x 2 m excavation unit spawn in their third year of life (i.e., after two winters' were analyzed to determine the nature and extent of var- growth) (Godfrey 1965: 7). Coho are the most wide- iability in vertebra size. spread species of Pacific salmon in British Columbia and The salmon vertebrae recovered from individual exca- are also the latest species to spawn (October and Novem- vation levels and stratigraphic divisions within the 2 m x ber) (Aro and Shepard 1967: 261). 2 m unit were sampled and measured to provide a statis- Sockeye salmon (0. nerka) spawn at four or five years tically-accurate estimate of the mean vertebral width per of age and are mainly restricted to a few major river level. Visual assessment during the course of identification systems such as the Fraser, which accounts for 67% of had seemed to indicate considerable variance in vertebral production in British Columbia and Washington State width between levels, with some possibility of systematic 106 News and Short Contributions

size variation over time. Detailed analysis showed that the late summer and fall. Of these, it could be determined kind of evidence for systematic size variation that might that pink salmon made very little contribution to the indicate temporal shifts in climate and fish growth-rates Namu assemblage. Because pink salmon invariably spawn was not present, but there was an indication of consider- at two years of age, only a small percentage of pink salmon able fluctuation in the average size of vertebrae from dif- were potentially represented in the Namu assemblage. ferent excavation levels. This variation was even more Pink salmon are abundant in a number of coastal streams, pronounced when vertebral width was converted to an such as the Koeye River south of Namu, but it is obvious estimate of fish weight. It was in an effort to account for that, throughout prehistory, Namu was never considered this variation that an examination of the age profile of the an important pink-salmon fishing site. The remaining salmon vertebrae was initially undertaken. salmon species (chum and coho) therefore must have Using the radiographic method of age determination made up the vast majority of the prehistoric salmon fish- described above, it was possible to determine the age ery. The spawning age of coho salmon most closely fits profile of each of the vertebrae samples. Overall, 88.9% the Namu age profile, but a substantial proportion of of the vertebrae exhibited two winters' growth (FIG. 2B), chum salmon also spawn at three years of age, even though while a much smaller percentage exhibited either one the majority normally spawn at four years of age. The (3.0%) or three (8.1%) winters' growth (FIG. 2A,C). Based presence of a small but significant percentage of four-year- on the level-by-level age profile it was possible to account old salmon indicates the probable presence of chum, and for the vertebral size variation that was observed. Al- it is known from ethnographic accounts that this species though three-year-old fish were predominant in every was favored for winter preservation (Romanoff 1985: level, those levels with a slightly higher than average per- 154). Chum are also a very common species on the central centage of two-year-old fish and/or a slightly lower than coast, spawning in appreciable numbers in a large number average percentage of four-year-old fish had smaller than of coastal streams such as the Namu River. average vertebrae, while the opposite situation accounted The presence of some proportion of chum salmon pre- for levels with larger than average vertebrae. But beyond sents a difficulty in explaining the relative lack of four- accounting for variation in size, the age profile of the year-old fish that should have been present if chum salmon salmon remains also gave a very clear indication of the were an appreciable part of the Namu salmon fishery. One species and seasonality of the Namu salmon fishery. possible explanation comes from the timing of the chum Based on the life histories of Oncorhynchus species, it salmon entry into spawning streams. Long-term obser- was possible to all but eliminate certain species as constit- vation of a salmon stream on the central coast has shown uents of the Namu assemblage. None of the Namu ver- that among chum salmon, which follow pink salmon in tebrae indicated fish older than four years of age (three spawning in late September, older four-year-old fish are winters' growth), and only a small percentage was as old the first to enter the spawning stream, followed by as four years. Sockeye spawn in their fourth or fifth year younger mature fish nearer the end of the spawning run of life, as do the majority of chinook. At present, the in early October (Hunter 1959: 849). A consistent late majority of sockeye in British Columbia spawn in only a arrival of the Namu inhabitants would account for missing few major river systems and are not common in small all but a fraction of older four-year-old chum salmon as coastal streams. Chinook do spawn in coastal streams, but well as most of the local pink salmon run. A major pink they are now rare in the central coast region. Therefore, or chum salmon fishery elsewhere in the region (possibly these species would not be expected to occur in great at the Koeye River) would account for this consistent late numbers in the Namu deposits unless they were brought arrival at Namu. Presence at Namu by early to mid-Oc- to the site from elsewhere. The absence of sockeye and tober would allow for fishing during the latter part of the chinook indicates the complete absence of a summer chum salmon run and the entire run of coho that followed salmon fishery at Namu, and this circumstance supports in October and November. other evidence that indicates a probable summer seasonal A consistent early to mid-October arrival at Namu best abandonment of the site (A. Cannon 1987). At present, explains the age profile of the recovered salmon remains. a large proportion of the native population of the central No evidence was found to suggest the less likely expla- coast region travels to Rivers Inlet in late June to take nation that different salmon species and four-year-old advantage of the sockeye salmon run (Rohner 1967: 24), chum were differentially processed at the site, resulting in the first of the season's salmon runs. the destruction of their remains. Preserved salmon of other The remaining three Oncorhynchus species all spawn in species, possibly lacking vertebrae as a result of processing, Journal of Field ArchaeologylVol. 15, 1988 107

Table 1. Namu salmon age profile by period. eye (four years old), and pink salmon (two years old) Salmon Age Classes (%) could be taken. It could also provide an indication of Period Sample Size Date (years bp.) 2 years 3 years 4 years regional or temporal variability in the availability and/or 5 384 3500-2200 6.3 86.6 7.2 accessibility of preferred species. The Thompson Indians 4 802 ca. 4200— 1.7 88.9 9.4 of the Fraser Plateau, for example, most preferred chinook 3500 3 495 5000—ca. 3.0 89.2 7.9 and sockeye salmon but resorted to pink salmon when 4200 other species were scarce (Teit 1900: 230-231). 2 194 6500-5000 2.1 92.8 5.0 With the important role that salmon played in prehis- 1 0* 10,000-6500 toric subsistence economies all around the northern Pacific *No faunal remains preserved. Rim, it is important to gain as much understanding as may have been brought to Namu from elsewhere, but, possible about past uses of this resource. Methods that assuming that the recovered remains are representative of will quickly and inexpensively yield statistically valid in- the fish caught at the site, at Namu salmon fishing itself formation concerning the nature of archaeological salmon took place relatively late in the season and consisted largely remains will go a long way toward achievement of this of coho and possibly later-spawning three-year-old chum understanding. salmon. The interesting point of the Namu findings is the re- Acknowledgments markable consistency of the inferred seasonal pattern over I want to thank Dr. Roy Carlson for providing me with at least 4000 years of site occupation. Table 1 shows the the opportunity to study the Namu faunal material; An- salmon age profile for each of four (out of five) temporal drew Barton for his help and suggestions during the periods defined for this part of the Namu deposits. The course of this research; and Debbi Yee Cannon for draft- consistency of the fishing pattern extends to well before ing Figure 1 and critically commenting on the manuscript. the likely achievement of full salmon-stream productivity This paper was written with the financial aid of a Social around 5000 b.p. (Fladmark 1975), and well beyond the Sciences and Humanities Research Council of Canada precipitous decline of the local Namu salmon fishery some- Post-doctoral Fellowship. This assistance is gratefully ac- time after 3500 b.p. (A. Cannon 1987). This pattern knowledged. makes clear the early and continuing presence of a coastal adaptation in the region that involved a seasonal round closely attuned to the availability of different species of Aubrey Cannon has had extensive experience in the excavation and Pacific salmon. analysis iffaunal remains from a number of sites on the coast if British Columbia. His other research interests include the study of Further Applications material-culture variability in ethnographic and historic contexts. He The procedures outlined here have potential application recently completed his PhD. in archaeology at the University of at any prehistoric site on the North Pacific coast in which Cambridge and is currently a post-doctoral research fellow in the salmon vertebrae are recovered in substantial numbers. Department ofAnthropology at the University of Toronto. Mailing The species composition of a salmon assemblage is of address: Department eAnthropology, University of Toronto, 100 St. interest for a number of reasons, particularly so as a basis George Street, Toronto, Ontario, Canada M5S 1A1. for inferring variation in seasonal fishing activity at a particular site or group of sites within a region. Specific Aro, K. V., and M. P. Shepard application in the Namu region would involve looking at 1967 "Pacific Salmon in Canada. Salmon of the North Pacific the salmon from a variety of sites to determine whether Ocean Part IV," International North Pacific Fisheries Com- they also indicate long-term consistency in the seasonal mission Bulletin 23: 225-327. exploitation of a particular salmon species. Possible ex- Cannon, Aubrey amples include sockeye salmon fishing at Rivers Inlet and 1987 "Central Coast Economic Prehistory: Namu (E1Sx-1) perhaps pink salmon fishing at sites such as the Koeye Fauna 6500-2200 BP," unpublished report on file, De- partment of Archaeology, Simon Fraser University, Bur- River. naby, British Columbia. In interior regions, as along the Fraser and Columbia Cannon, Debbi Yee drainages, age determination of salmon remains could aid 1987 Marine Fish Osteology: A Manual for Archaeologists. Simon in distinguishing spring chinook-fishing sites from fall Fraser University, Department if Archaeology Publication fishing sites where chinook (four and five years old), sock- No. 18. Burnaby, British Columbia.

108 News and Short Contributions

Carlson, Roy L. Nordeng, H. 1979 "The Early Period on the Central Coast of British Co- 1961 "On the Biology of Char (Salmi alpinus L.) in Salangen, lumbia," Canadian Journal of Archaeology 3: 211-228. North Norway. I. Age and Spawning Frequency Deter- mined from Scales and Nytt Magasin for Zoologi Casteel, R. W. Otoliths," 10: 67-123. 1972 "Some Archaeological Uses of Fish Remains," American Antiquity 37: 404-419. Pomeroy, John Anthony 1980 "Bella Bella Settlement and Subsistence," unpublished "Use of Pacific Salmon for Estimating Fish Size 1974 Otoliths Ph.D. dissertation, Simon Fraser University, Burnaby, with a Note on the Size of Pleistocene and Pliocene British Columbia. Salmonids," Northwest Science 48(3): 175-179. Ricker, W. E. 1976 Fish Remains in Archaeology and Paleo-environmental Stud- 1964 "Ocean Growth and Mortality of Pink and Chum ies. London: Academic Press. Salmon," Journal of the Fisheries Research Board of Canada Chugunova, N. I. 21: 905-931. 1963 Age and Growth Studies in Fish: A Systematic Guide for Rohner, Ronald P. Ichthyologists. Jerusalem: Israel Program for Scientific 1967 The People of Gilford: A Contemporary Kwakiutl Village. Translations. National Museum of Canada Bulletin No. 225, Anthro- Flaclrnark, Knut R. pological Series No. 83. Ottawa. 1975 A Paleoecological Model for Northwest Coast Prehistory. Na- Rojo, Alfonso tional Museum of Man Mercury Series, Archaeological Survey 1987 "Excavated Fish Vertebrae as Predictors in Bioarchaeo- of Canada Paper No. 43. Ottawa: National Museums of logical Research," North American Archaeologist 8: 209- Canada. 226. Godfrey, Harold Romanoff, Steven 1965 "Coho Salmon in Offshore Waters. Salmon of the North 1985 "Fraser Lillooet Salmon Fishing," Northwest Anthropolog- Pacific Ocean Part IX, Coho, Chinook and Masu Salmon ical Research Notes 19: 119-160. in Offshore Waters," International North Pacific Fisheries Commission Bulletin 16: 1-39. Teit, James A. 1900 "The Thompson Indians of British Columbia," in Franz Hart, J. L. Boas, ed., The Jesup North Pacific Expedition. Memoir of 1973 Pacific Fishes of Canada. Fisheries Research Board of Canada the American Museum of Natural History Vol. 1, Part 4. Bulletin 180. Ottawa. New York. Henry, K. A. 1954 Age and Growth Study of Tillamook Bay Chum Salmon. Fish Commission (f Oregon Contribution No. 19. Portland. Hunter, J. G. 1959 "Survival and Production of Pink and Chum Salmon in Friable Pigments and Ceramic Surfaces: A a Coastal Stream," Journal of the Fisheries Research Board of Canada 16: 835-886. Case Study from sw Iran Leach, B. F. JAMES A. NEELY 1979 "Fish and Crayfish from the Washpool Midden Site, New The University of Texas at Austin Zealand: Their Use in Determining Season of Occupa- tion and Prehistoric Fishing Methods," Journal of Ar- PAUL S. STORCH chaeological Science 6: 109-126. South Carolina State Museum Monks, Gregory G. Columbia 1981 "Seasonality Studies," in Michael B. Schiffer, ed., Ad- The loss offriable pigments, as well as the ceramic surfaces to which vances in Archaeological Method and Theory 4. New York: they were applied, was researched in an attempt to stay the destructive Academic Press, 177-240. processes affecting sherds recovered by survey in sw Iran. Prior to Neave, F., T. Yonemori, and R. G. Bakkala experimental treatment, the pigments and salt dorescences were 1976 "Distribution and Origin of Chum Salmon in Offshore identified using optical and instrumental analyses. A technique for Waters of the North Pacific Ocean," International North cleaning the calcareous encrustations from the pigment and ceramic Pacific Fisheries Commission Bulletin 35: 1-79. surfaces without the use of acids was developed. This cleaning Nichol, R. K. technique also solved a problem encountered in x-ray diffraction 1982 "Seasonal Dating from Fish Frequencies," Journal of Ar- analysis when studying pigments applied to ceramics affected by salt chaeological Science 9: 391-393. encrustations. Several consolidant solutions were tested and applied to Norden, C. R. polychrome painted sherds recovered from one of the sites in the Deh 1961 "Comparative Osteology of Representative Salmonid Luran Plain. An acrylic resin was found to be acceptable as a consol- Fishes, with Particular Reference to the Grayling (Thy- idation agent. The authors feel that the experiments and results mallus arcticus) and Its Phylogeny,"Journal of the Fisheries presented will serve as useful models for archaeologists and Research Board of Canada 18: 679-791. conservators facing similar problems.