3. Materials and Methods: Connecting exploited species, aquatic habitats, and fishing strategies

In the reconstruction of past aquatic adaptations along the east African coastline, fish remains are of particular importance as they represent the principal form of evidence of these practices. Very limited examples of fishing tools have been recovered from archaeological contexts in this region. Fish remains, on the other hand, are numerous and can be used to identify what species were exploited in the past. Furthermore, the connection between fish species and particular fishing strategies and exploited habitats allows us to reconstruct past fishing activities from archaeological fish remains samples.

We compared archaeological fish remains data from two Swahili regions that represent different maritime landscapes: a near-shore archipelago (Shanga) and large offshore islands (Zanzibar and Pemba sites) (Table 1). The Shanga faunal material is particularly exemplary because of the large size of the sample and its association with a long chronological timeline spanning the 8th to 15th centuries (Mudida and Horton 1996). The fish material analysed is from Trench 2, a deposit of domestic midden material; 6009 fish bones were identified to species or taxa of local marine fish (Mudida and Horton 1996, 380). Excavations on Pemba and Zanzibar islands produced five faunal assemblages yielding a total 1034 identified fish remains, summarised by Horton and Mudida (forthcoming). These samples provide comparative data of sites in this region for the 7th to 15th centuries: Fukuchani (7th–8th), Unguja (7th–10th) and Tumbatu (12th–14th) are found around Zanzibar Island while Ras Mkumbuu (10th–15th) and Mtambwe Mkuu (9th–14th) are found along the Pemba coastline. Both sets of faunal material were collected using 5mm mesh screens and analysed by Nina Mudida using the comparative osteological collection at National Museums of Kenya. Descriptions of the morphological features and criteria used to differentiate the represented fish taxa are available in the published sources of these data (for the Shanga data, see appendix in Horton and Mudida 1993, 683-93 and footnotes in Mudida and Horton 1996; for the Pemba and Zanzibar data, see footnotes in Horton and Mudida forthcoming).

Site comparisons are possible because of the uniformity in the collection and identification methods among the fish remains assemblages. However, the sample sizes range from 19 identified specimens at Fukuchani to 5,999 identified specimens at Shanga. We acknowledge that the samples with less than 100 identified specimens (Fukuchani, Ras Mkumbuu, and Mtambwe Mkuu) should be interpreted with caution, since a small sample size limits how effectively it represents actual economic behaviours rather than taphonomic effects. Taken as preliminary studies, nonetheless, the patterns of habitat exploitation in these small offshore island samples are in line with those of the other offshore island samples that have more robust sample sizes (Tumbatu and Unguja Ukuu). Ongoing analyses of larger assemblages from Fukuchani and Unguja Ukuu (Prendergast and Quintana Morales in prep) can be compared to these patterns in the future.

Although there is overlap in the range of environments occupied by fish species, particular fish species generally inhabit certain sections of the marine environment, and the composition of these species at each site can be used to estimate the variable exploitation of aquatic habitats. Five aquatic habitats are used to represent the types of environments generally occupied by different types of fish along the East African coast: coral, estuary, sandy-muddy, outer reef, and various (a similar classification was used by Van Neer 2001, and Nakamura 2011). The last category, various, includes fish species that inhabit several marine zones. These categories were chosen to represent typical coastal habitats along most of the East African coast, to be easily identified around coastal settlements through surveys and maps, to be relevant to local traditional fishing activities, and to be easily associated with populations of fish species according to the current fish ecology literature. Fish were classified into habitats using the most specific taxonomic category possible to account for the behavioural variability within each fish family. The analysis includes only the fish remains identified to species and genus, which make up 74–99% of the reported fragments from each site and represent 67 taxa overall (58 of which are unique species). The habitats associated with different species were identified using widely used references on marine fish in the Western Indian Ocean (Fischer and Bianchi 1984; Froese and Pauly 2012). The summarised ecological information about each fish species in these references was used to determine its habitat category. Because the Shanga material represents a long sequence of phases, it was possible to analyse patterns of fish exploitation over time using the same analytical methods. Shifts in the representation of different aquatic habitats could be associated with a combination of social and environmental changes (Quintana Morales 2013b).

Various factors determine the catch composition of fish species, including the exploited habitat, season, fishing method and fishers' skill. To explore past exploitation strategies, we compared the dominant species in each habitat to the target species associated with artisanal fishing practices in this region. An aspect of fishing that is not often reported in the ethnographic and historical sources, the link between fishing strategies and fish catch is often studied by fisheries officers and marine biologists in order to manage and conserve coastal resources. We summarised three examples of these studies along with information we collected in the field in order to provide an overview of the common artisanal fishing gear used in this region and their target species (Table 2). We used this information to infer past fishing strategies from the composition of species in the sample assemblages, which allows us to explore the use of different fishing strategies within each habitat category.