In this post we present selected parts of the very interesting paper titled “Tooth oxygen isotopes reveal Late Bronze Age origin of Mediterranean fish aquaculture and trade“, by Sisma-Ventura Guy et al.
Fishing was an essential economic component of many ancient societies, as evidenced by the presence of fish remains, fishing gears, and fish-associated artifacts in numerous archaeological sites world-wide. In the southern Levant, past exploitation and trade of fish has been explored primarily based on the occurrences of fish bones in coastal, riverine and lake-side archaeological sites and through inference from the modern distribution patterns, habitat preferences and ecological niches of these fish species. In the Levant, this has mostly been done for fish that a priori were identified as ‘exotic’. For example, the identification of key Nilotic species such as Lates niloticus (Nile perch) and Bagrus sp. (Bagrid catfish) in archeological sites of the southern Levant testified that long-range trade systems between Egypt and Canaan have emerged more than 5000 years ago (during the Early Bronze Age).
The gilthead seabream (Sparus aurata, Linnaeus, 1758) frequently appears in archaeological sites of the southern Levant, since prehistoric times (Late Pleistocene). This species is characterised by thick-enamelled, molar-like teeth, which are used for cracking shellfish (i.e., bivalves, gastropods and crustaceans). Sparus aurata is an euryhaline and eurytherm marine fish which migrates between near-shore, inshore (lagoons) and open sea environments. Thus, while the appearance of S. aurata in inland sites clearly indicates long range trade systems remains of this species in Levantine coastal sites have so far been interpreted as reflecting local fishing activity.
State of the art research methodologies provide multiple empirical ways to explore trade and maritime connections of desirable fish source marketing to distant places. For example, past provenance and long-range trade of fish from the North Atlantic have been studied using the C and N stable isotopes of bone collagen (Atlantic cod) and by aDNA analysis. However, fish bone C and N isotope analyses require the preservation of collagen, and they are limited to “young” fish because constant bone remodeling causes the isotopic signature to adjust to local conditions in adult fish. In the North Aegean (northeast Mediterranean), these analyses showed no clustering with locality or species, and for both isotopes they demonstrated a general overlap between freshwater and marine fish, probably due to bone diagenesis. Hence other isotopic proxies are required to assess fish provenance.
Enameloid of fish teeth is highly resistant to diagenetic alterations, and thus in many cases preserve information regarding the original salinity and temperature of their past aquatic habitat (i.e. marine, rivers, lakes, and lagoons). In closed or semi-closed water bodies with a high degree of evaporation, the δ18OWater are enriched in 18O relative to the seawater that feeds them. Enameloid of fish teeth from such water bodies carry distinctively high δ18OPO4 values, which reflect hypersaline habitats of the fish. The Bardawil lagoon (Sabkhat al Bardawil; along the northern coast of Sinai, Egypt is such a water body.
We assess the provenance of ancient S. aurata from archaeological layers in the southern Levant by using phosphate oxygen isotope analysis of fish teeth enameloid as a proxy for fish habitat salinity.
The fortunes of the Mediterranean southern Levant have always been intertwined with that of its Saharan neighbour in Egypt. Those two different agro-ecological regions were economically interdependent and from the first consolidation of centralized power in Egypt in the 3rd millennium BCE (the Egyptian Old Kingdom), Egypt episodically controlled the southern Levant, whence it could extract the Mediterranean products required for its subsistence and spiritual life. Interconnections between the two regions, however, were not only dictated by cultural and political factors but by climatic fluctuations in both. Traffic between Egypt and the Levant was conducted through marine or terrestrial routes through northern Sinai, which was both affected by it in antiquity and provides archaeological proxies for its intensity today. The main question we asked is whether the distribution of these fish to the Levant was a historically-unique and context-dependant phenomenon or rather of more sustainable nature.
Identification of Fishing Grounds/Habitats and Formation of Coastal Lagoons in the Southeast Mediterranean
A key factor in the formation of coastal lagoons in the southeast Mediterranean was the post-glacial stabilisation of the sea level. Over the last 4,000 years sea level stabilised close to its present-day level, reaching the current level (±1m) at around 3,620 ± 160 years BP (1,620 BCE; based on optically stimulated luminescence dating of marine sand deposits, overlain by aeolian sand). Sea-level stabilisation allowed the formation of the perennial shallow hypersaline Bardawil lagoon along the northern Sinai coast, due to the establishment of long-shore currents that transported Nile sands which built up blocking sandbars.
During the Early Holocene (Pre-Pottery Neolithic; PPN): PPNA; ~9,700 years BCE; 11,700 years BP) δ18OPO4 values indicate that S. aurata was captured mainly from southeast Mediterranean waters and to a lesser extent from hypersaline lagoons. The latter results are the first proof of the past existence and exploitation of hypersaline coastal lagoons along the eastern Mediterranean coast during the Early Holocene. Due to the sharp rise in sea level at the onset of the post-glacial period the nature of these lagoons remains unknown. Nevertheless, local fishing in Mediterranean littoral waters was previously assumed based on fish remains from the now-submerged PPNC site of Atlit-Yam in northern Israel.
Mid-Holocene (Chalcolithic period and the Early Bronze Age: 4,500–2,500 years BCE; 6,500–4,500 years BP), δ18OPO4 values indicate that S. aurata was primarily captured ‘locally’, namely along the southeast Mediterranean coast, however, data are insufficient for reconstructing the variability of fishing grounds for this time span. Currently, we have no data regarding the Middle Bronze Age (MBA). However, by the end of the LBA (~1,200 years BCE; ~3200 years BP), and onwards the fish-harvesting pattern in the southeast Mediterranean changed drastically, shifting to exploitation of S. aurata from a hypersaline source almost exclusively. Whereas only 13.9% of the teeth (n = 33) analysed from pre-LBA contexts (PPN to EBA) had δ18OPO4 values indicative of hypersaline habitats, 84.2% of the teeth (n = 57) from the LBA to the Iron Age (IA) were characterised by high δ18OPO4 values typical for fish from hypersaline habitats. This pattern also prevails in the Byzantine period (n = 10). The δ18OPO4 values of sparid teeth from the LBA onwards are similar to those of extant S. aurata from the Bardawil lagoon. In addition, from the late LBA onwards, both dentary bone and teeth of the same specimens of S. aurata displayed hypersaline isotopic signatures, suggesting that those fish may have spent their entire life cycle in the Bardawil lagoon.
Fish Body Mass as Indicator for Fishing Intensity
The body size of S. aurata (i.e. total length-TL (cm) and body mass-BM (kg)), can be calculated from the maximum length of the molariform tooth crown. Body size of S. aurata reflects ontogenetic age and can thus be used as a proxy of fish exploitation. Smaller average fish body size in both archaeological and modern contexts is associated with higher intensity exploitation of their nursery, i.e. the Bardawil lagoon. During the Holocene, the size pattern of S. aurata clearly changes, exhibiting a decrease and lower range in fish size (i.e. harvesting of younger individuals) for specimens from the hypersaline lagoonal waters of the Bardawil. The values estimated for S. aurata body size (body mass and total length) show significant decrease in the range and average size. The range of S. aurata decreased from a mean BM of 1.6 ± 0.8 kg (n = 33) and TL of 45.0 ± 8.3 cm during PPN–Early Bronze Age (EBA) to a mean BM of 1.1 ± 0.4 kg (n = 57) and TL of 40.7 ± 5.1 during LBA–IA, and to a mean of 0.78 ± 0.4 kg (n = 10) and mean TL of 36.4 ± 3.8 in the Byzantine period, approaching the average fish size of modern aquafarm Sparus (~0.45 kg) (for BM: 1-Way ANOVA: F = 3.9968; p < 0.0001; F = 3.532; For TL: p < 0.001; F = 3.267).
This trend of reduction in fish body size accords chronologically well with cultural changes and spreads over a millennial time-scale, starting in the LBA, continuing to the Iron Age and to the Byzantine period. Interestingly, we witness the appearance of larger fish only at Tel Dor, where we identified in the past S. aurata captured from the Mediterranean littoral zone. Overall, the reduction in S. aurata mean and maximum body size demonstrates similarity with present day fishery data from the Bardawil lagoon (age group 1–3 years), where S. aurata are intensively exploited due to their abundance in this unique hypersaline nursery. The decrease in S. aurata body size, to a range similar to present-day fish from the lagoon is in line with observations from traditional extensive aquaculture.
From the LBA onwards we find evidence for extensive and likely year-round exploitation of S. aurata in the Bardawil lagoon.
Sparus aurata were traditionally exploited extensively in coastal lagoons, until intensive rearing systems for this fish were developed during the 1980s. Therefore, the cradle of marine aquaculture may be rooted in the Bardawil hypersaline lagoon. For more than 2,000 years it functioned as the major source for Sparus aurata for the Levant. This started not later than the LBA (~1,200 years BCE; 3200 years BP) as extensive harvesting and still continues today as intensive aquafarming.
A Diachronic Summary: Fish Exploitation in The Context of Egypto-Levantine Exchanges
In the southern Levant, for the last 50,000 years, S. aurata were exploited by local coastal fishing communities. The first evidence for fishing in hypersaline lagoons appears during the PPNB ca. 9,500 years BP, but these remains are scarce and are insufficient to indicate systematic exploitation of hypersaline lagoons during this period. However, the occurrence of fish remains in Neolithic inland sites of the Judean Mountains (central Israel) indicates that the transportation of dry fish from the Mediterranean coast was already established in the Early Holocene.
From the LBA period onwards, non-local (“exotic”) S. aurata with hypersaline δ18OPO4 signatures were imported from the Bardawil lagoon, almost entirely replacing S. aurata caught locally in coastal waters. These results contradict the conventional null hypothesis assuming that in coastal sites of the Levant S. aurata remains will represent local fishing, exhibiting that regardless of the site location (coastal or inland) most of the S. aurata were “exotic” (nonlocal) with δ18OPO4 signatures of the Bardawil lagoon.
In archaeological sites across the southern Levant, this fundamental change in fish provenance coincides with a sharp increase in the abundance of exotic Nilotic fish, such as Nile perch (Lates niloticus) and the Nile catfish. Our results, therefore, provide new evidence for the intensity of Egypto-Canaanite long-distance, inter-regional trade connections in this period, which seem to have even included commercialization of fish from Bardawil lagoon. This pattern, which further intensified in the Iron Age and lasted at least until the Byzantine period, most likely comprised dried S. aurata, as depicted in Egyptian reliefs and as observed from the fragmentation patterns on some of the S. aurata remains recovered in Jerusalem (inland).
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