Exploitation history of Atlantic bluefin tuna in the eastern Atlantic and Mediterranean—insights from ancient bones

Abstract

Overexploitation has directly, negatively affected marine fish populations in the past half-century, modifying not only their abundance but their behaviour and life-history traits. The recovery and resilience of such populations is dependent upon their exploitation history, which often extends back millennia. Hence, data on when exploitation intensified and how populations were composed in historical periods, have the potential to reveal long-term population dynamics and provide context on the baselines currently used in fisheries management and conservation. Here, we setup a framework for investigations on the exploitation history of Atlantic bluefin tuna (Thunnus thynnus; BFT) in the eastern Atlantic and Mediterranean by collating records of their zooarchaeological remains and critically reviewing these alongside the literature. Then, we outline how novel multidisciplinary applications on BFT remains may be used to document long-term population dynamics. Our review of literature provides clear evidence of BFT overexploitation during the mid-20th century ce. Furthermore, a strong case could be made that the intensification of BFT exploitation extends back further to at least the 19th century ce, if not the 13th–16th century ce, in the eastern Atlantic and Mediterranean. However, a host of archaeological evidence would suggest that BFT exploitation may have been intensive since antiquity. Altogether, this indicates that by the currently used management baselines of the 1970s, population abundance and complexity was already likely to have declined from historical levels, and we identify how biomolecular and morphometric analyses of BFT remains have the potential to further investigate this.

Length estimation of Atlantic bluefin tuna (Thunnus thynnus) using vertebrae

“…Poorly preserved vertebrae could, however, be identified to type, and in some cases, for example, V1 and V36–39, types should not be needed when vertebrae are especially unique (Appendix S2). It is important for researchers to be able to utilize all vertebrae for BFT size estimations since recoveries of BFT vertebrae are usually few, articulated vertebrae are rare, and recovered BFT vertebrae often vary significantly in rank depending upon their archeological context (Andrews et al, 2022). Seldom can all vertebrae be used for archeological size estimations of fishes.…”

“…This site is unique in being one of the few BFT midden sites located to date. This is important because large BFT are seldom recovered in settlements and salting factories where most excavations have focused on, probably because processing was more practical at the shore (Andrews et al, 2022). Midden sites might therefore provide a more representative sample of BFT fishing in any given region or period.…”

“…Archeological fish remains are vital when investigating the role that fish have played in cultural developments and, conversely, how such developments have impacted fish populations themselves (Colley, 1990; Erlandson & Rick, 2010; Orton, 2016). Studies on fish remains typically utilize a number of methodologies to do this, for example, recording the location, identity, and number of remains recovered (Colley, 1990; Hoffmann, 2005); analysis of their taphonomy and archeological context (Çakırlar et al, 2016; Prieto, 2021; van Neer et al, 2004); their morphological identification, provenance, and genetics inferred by applications of biomolecular tools (Andrews et al, 2021, 2022; Orton, 2016; Richter et al, 2011; Winter et al, 2021); and the estimation of fish size from measurements on fish remains (Casteel, 1976; Desse et al, 1989; Wheeler & Jones, 1989).…”

“…Moreover, size information can be used as an additional species identification criterion and to assess the minimum number of individuals (MNI) recovered in excavations (Orchard, 2005). The need for archeological size metrics to inform present‐day sustainability is particularly important for one key species, Atlantic bluefin tuna ( Thunnus thynnus , hereafter BFT), since it appears to have had a long and intense history of exploitation yet the impact on the population is unknown (Andrews et al, 2022). Despite much interest in BFT archeology (Felici, 2018; García Vargas et al, 2018; Mylona, 2021; Nielsen & Persson, 2020), there are currently no reliable methods to estimate BFT size from archeological remains.…”

“…Cranial elements are sometimes used as the reference of choice because these are readily identified and produce good estimations of body size (Desse & Desse‐Berset, 1996; Jiménez‐Cano & Masson, 2016; Thieren & van Neer, 2016). Given the rarity with which BFT cranial elements are recovered in archeological contexts (Andrews et al, 2022), vertebrae—a robust and well‐preserved element—were chosen as an alternative. Size estimations have been seldom applied to BFT, namely, by Rose (1994), who developed a coarse method of estimating length from a single vertebra (also applied by Mylona, 2018, and Morales‐Muniz & Roselló‐Izquierdo, 2007, who developed a precursor to the current study).…”