The coastal fringe of the Indian Ocean along the East African continental shelf is a rich area of biodiversity. The large amounts of fish remains found at a majority of Swahili sites, dated between the 7th and 15th centuries CE, attest to the continued use of aquatic resources. Fishing along the east African coastline has been characterised as being largely inshore. Fishers in this area exploit a range of inshore habitats such as mangrove stands, mudflats, sea grass beds, and coral reefs. Although these habitats are interconnected, they are characterised by different sets of fish species that are exploited through unique strategies and tools. Several authors have linked identified fish remains from particular sites with the exploitation of various inshore habitats in that area (e.g. Mudida and Horton 1996; Fleisher 2003; Van Neer 2001). However, little work has been done to understand the connection between aquatic habitats, fishing strategies and exploited species across the region. This article explores aquatic subsistence strategies in relation to local environments and histories in a comparative regional context (Figure 1): a near-shore archipelago (Lamu archipelago, site of Shanga) and two large offshore islands (Zanzibar and Pemba, the sites of Unguja Ukuu, Fukuchani, Tumbatu, Ras Mkumbuu and Mtambwe Mkuu).
The Swahili coast of East Africa represents an exceptionally interesting area to study the relationship between maritime urban communities and the aquatic environment. The first archaeological evidence for coastal settlement dates to the very early first millennium CE, on Mafia and adjacent islands. These Early Iron Age sites contain substantial evidence for the exploitation of aquatic resources, including fish bones and shell-fish (Chami 2000; 2004; Crowther et al. 2012). Many more sites date from the 7th century onwards on both the coast and offshore islands; they are generally located on the shore or immediately behind. These form the basis of the subsequent Swahili urban culture, with extensive long-distance trade links with the Middle East, South and South-east Asia and China (Horton and Middleton 2001). The first evidence for Islam is late 8th century, and the adoption of stone and brick architecture dates to the 10th century; by this time larger sites with populations of several thousand existed among a number of much smaller village sites. Fish and shell-fish continue to be key components in the diet and enable these settlements to thrive in areas of relatively low agricultural potential. In this early period the key sites are Manda (Chittick 1984) and Shanga (Horton 1996) in the Lamu archipelago, Tumbe/Chwaka on Pemba (Fleisher and LaViolette 2013) and Fukuchani and Unguja Ukuu on Zanzibar (Juma 2004; Horton forthcoming).
The 11th century saw a major urban transformation, with many of the early sites being abandoned or severely disrupted, and new settlements developing nearby. At Shanga, this involved destruction of the older buildings and the burning down of the mosque. Unguja Ukuu and Tumbe were abandoned, and re-established at nearby Chwaka (LaViolette and Fleisher 2009) and Kizimkazi (Horton forthcoming; Kleppe 2001), while new urban complexes developed at Ras Mkumbuu, Mtambwe Mkuu on Pemba, and Tumbatu Island (Horton forthcoming). These (and maybe over 400 others along the Swahili coast) developed a distinctive urban culture, with numerous stone houses, as well as mud houses, laid out in a tight landscape of houses and narrow streets; good examples of this from the 14th and early 15th century include Shanga (Horton 1996) and Songo Mnara (Wynne-Jones 2013; Fleisher and Wynne-Jones 2012), the subject of a major current research project. Fish remains an important element in these places, even though the populations are now substantial and widely distributed along the whole coast. The towns became successful trading ports, with many imports, and centres of craft and productive activity (especially iron working, cloth and bead making). The Portuguese arrival in 1498 left extensive descriptions but little lasting economic impact, and several of the port-cities survive as functioning entities into the 21st century, where fishing remains a very important element in the economy (Horton 2006).