Herding Salmon: interpretations of fish weirs, traps, and clam gardens

Wood Stake Fish Weir on Oregon Coast, by Scott Byram, 2010.

by Hannah P. Wellman,

Ph.D. student, U Oregon
Fish weirs, traps, and clam gardens are intertidal zone modifications found on the Northwest Coast. These archaeological features are remains of resource management by indigenous peoples in the past, and sometimes, the present. Archaeologists agree that these features reflect resource management and stewardship, but there are different ways to interpret why, how, and when these features were built, and how archaeologists infer the behavior and motivations of the indigenous peoples who built them. Optimal Foraging Theory (OFT) and Niche Construction Theory (NCT), are evolutionary ecology approaches to understanding hunter-gatherer subsistence strategies and behavior that have been used to interpret fish traps and weirs. OFT assumes that humans behave in predictable ways to get the most resources with the least expenditure of energy. NCT proposes that humans (and all other species!) make changes in their environment, which in turn alters natural selection pressures on the niche inhabitants and their descendants. Another approach is Traditional Ecological Knowledge (TEK), a more integrated approach which places archaeological evidence within a broader context of cultural understanding. Which is best? What might a truly integrated approach might look like?

An example of OFT applied to fish weirs was written by Megan Caldwell. Caldwell (2008) evaluated the fish traps at Comox Harbor through a behavioral ecology framework. She noted that fish traps are a “patch” of a resource. The OFT “patch choice model” predicts that people will target patches, because it is a net gain of energy: after the initial expenditure of energy to build the trap, fish are easy to acquire in large numbers (2008:137). The large quantity of fish in a trap might result in additional benefits. Other species that eat fish may be attracted to the area, such as seals and seabirds (Caldwell 2008:137). Caldwell sees fish trap use at Comox Harbor related to socioeconomic complexity and the development of households. She suggested that increased production of fish relies on the ability to organize and control labor, which in turn required an organizational unit: the household (2008:138). I agree with Caldwell’s use of the patch choice model and her assessment of fish traps as “patches” – they would certainly provide large quantities of fish (2008:136). I am hesitant to tie socioeconomic complexity to the development of fish weirs. While it may be the case at specifically Comox Harbor, I am wary of assigning fish weir technology as yet another step in the trajectory of socioeconomic “complexity” on the Northwest Coast.

In his blog post “Fish Traps at Comox Harbour,” Quentin Mackie posted about Caldwell’s thesis and suggested that a “similar and more holistic argument […] using principles of the ‘built environment’” might be another way to consider the fish weirs. Intertidal modifications like fish weirs and traps have been referenced in NCT literature as a classic example of niche construction – they are literally niches constructed by humans to encourage or focus biodiversity and species-specific productivity in locations across the environment. Smith (2011:837) categorizes niche construction activity into six types, and fish
traps/clam gardens fit nicely into his sixth: “landscape modification to increase prey abundance in specific locations.” Yet Smith’s classification focuses on ecosystem engineering – he does not discuss other evolutionary ecology elements (remember, niche construction involves changing selective pressures in the environment) (Broughton and O’Connell 2006, Laland et al. 2010). As of writing this blog, I am unaware of any publications that have specifically analyzed fish weirs, traps, or clam gardens through a specific NCT framework. So I will give it a shot myself! As I mentioned above, niche construction usually involves significant changes to an ecosystem, resulting in altered selective pressures on the modifier and/or other species in the niche, and accompanying changes in phenotype and behavior (Broughton and O’Connell 2006, Broughton and O’Connell 2010, Laland et al. 2010). Smith (2011) rightly suggests intertidal modifications are good examples of ecosystem engineering, but he does not elaborate upon what selective pressures fish traps and clam gardens alter and the subsequent behavioral feedback. This may be because finding a specific genetic locus that is altered or fixed in a population due to clam gardens or fish traps would be impossible. We could say, however, that intertidal modifications increased general productivity of prey such as clams and different species of fish, and potentially made them easier to harvest within specific environments. This would incentivize the behavior of building intertidal fish weirs/clam gardens, and encourage parents to teach their children about how to build the features, as well as pass on any associated cultural traits and beliefs throughout the generations. Offspring would inherit the modified intertidal environment from their parents, also sometimes called ecological inheritance.

Stone Fish Trap by Elroy White. From Brown and Brown (2009)

Traditional Ecological Knowledge is an approach used by Elroy White. White is   Heiltsuk and his study involved an integration of oral historical knowledge from his community. Instead of trying to quantify or create a typology for the fish traps in his tribe’s territory, White simply asked Heiltsuk community knowledge holders about salmon, fishing, and fish traps (2010:84). White learned about the function of the traps, which were “built to implement a sustainable fishery for subsistence purposes” (2010:75) and a way to “minimize maintenance and to maximize efficiency” (2010:89) in acquiring salmon. Although White doesn’t use an OFT/NCT framework, you may recognize that a focus on maximizing salmon and minimizing maintenance is similar to some of the ideas above. White also writes that the fish traps are “the products of my ancestors’ labor and represent a legacy we have inherited” (2010:75). Sounds like ecological inheritance, no? The oral histories White recorded revealed specific quotidian behaviors involved in working the stone traps that the archaeological record never could. White’s informants described how the stone traps created a fishbowl of sorts by catching all available salmon, which could then be collected based on their suitability for smoking (2010:88) (the ideal salmon for smoking were those with low oil content; 2010:85). Un-harvested salmon were then released back into the stream. Although not in White’s study, a Hilistis informant, Pauline Waterfall, noted that the fish taken by “knowledgeable fishermen” were “not the strongest or the fittest,” thus ensuring the health of the stock because healthy salmon were released (Brown and Brown 2009:47). If humans were selecting specific phenotypes of the available salmon, this is an example of niche construction and human behavior altering selective pressures on other species in the shared environment. Other informants described the removal of the stone wall in several places along the trap once fishing season was over to ensures that salmon can escape, which White calls a “time-honored Heiltsuk conservation process” (2010:86).

Having considered these three studies, the larger themes are apparent. Archaeologists and anthropologists see fish weirs/clam gardens as a means to optimize or create an abundance of desired resources, or as a harvest method chosen to ensure sustainable populations. The development of intertidal zone modifications can be linked to a general concern about conservation and maintaining a sustainable relationship with the environment. Fish traps/clam gardens reflect reflect holistic management by First Nations and Native American fishers on the Northwest Coast. The behavioral ecology approach may be limited; I dislike the strict, predictive take on human behavior, which has acknowledged limitations (Broughton and O’Connell 1999:161). I was under the assumption that I would find NCT the best framework for explaining intertidal modifications, but that approach too can only explain so much. In comparison, Elroy White’s study of stone fish traps in Heiltsuk territory shows that a TEK base for understanding the stone traps is an effective way to learn more about the behaviors surrounding the traps, and still allows for linkages to niche construction and ecological inheritance. I suggest a fully integrated approach would start with an oral history of the clam gardens and fish traps. Then, an evolutionary ecology framework may be considered where applicable. Archaeology is naturally multi-disciplined and open to various interpretations. We should understand intertidal zone modifications as multi-functional, with different cultural, behavioral, symbolic and practical motivations behind their construction. It would also do us well to consider these archaeological features in their full context and consider how we in the present treat and manage our own resources by comparison.

Editor’s Note: The research paper version of this inspired Moss and Wellman to write an article that will appear in the Alaska Journal of Anthropology. M. Moss