Southward re-distribution of tropical tuna fisheries activity can be explained by technological and management change.

There is broad evidence of climate change causing shifts in fish distribution worldwide, but less is known about the response of fisheries to these changes. Responses to climate-driven shifts in a fishery may be constrained by existing management or institutional arrangements and technological settings. In order to understand how fisheries are responding to ocean warming, we investigate purse seine fleets targeting tropical tunas in the east Atlantic Ocean using effort and sea surface temperature anomaly (SSTA) data from 1991 to 2017. An analysis of the spatial change in effort using a centre of gravity approach and empirical orthogonal functions is used to assess the spatiotemporal changes in effort anomalies and investigate links to SSTA. Both analyses indicate that effort shifts southward from the equator, while no clear pattern is seen northward from the equator. Random forest models show that while technology and institutional settings better explain total effort, SSTA is playing a role when explaining the spatiotemporal changes of effort, together with management and international agreements. These results show the potential of management to minimize the impacts of climate change on fisheries activity. Our results provide guidance for improved understanding about how climate, management and governance interact in tropical tuna fisheries, with methods that are replicable and transferable. Future actions should take into account all these elements in order to plan successful adaptation.

A reconstructed database of historic bluefin tuna captures in the Gibraltar Strait and Western Mediterranean.

This data paper presents a reconstruction of a compilation of a small but consistent database of historical capture records of bluefin tuna (Thunnus thynnus; BFT hereafter) from the Gibraltar Strait and Western Mediterranean (Portugal, Spain and Italy). The compilation come from diverse historical and documentary sources and span the time interval from 1525 to 1936 covering a period of 412 years. There is a total of 3074 datum, which reach up to 67.83% of the total implying a 32.17% of missing data. However, we have only reconstructed the captures for the time interval 1700-1936 and we provide these reconstructions only for this time interval and for 9 out of 11 series due to the scarcity and inhomogeneity of the two oldest capture time series. This reconstructed database provides an invaluable opportunity for fisheries and marine research as well as for multidisciplinary research in climate change.

Comparative study of muscle proteins in relation to the development of yake in three tropical tuna species yellowfin (Thunnus albacares), big eye (Thunnus obesus) and skipjack (Katsuwonus pelamis).

Burnt tuna (BT), or yake-niku, is a quality flaw of the muscle characterised by a pale colour and grainy and exudative texture. Cathepsin-L, water soluble and total protein components from normal and BT muscles, from three tropical tuna species - yellowfin (YFT, Thunnus albacares), bigeye (BET, Thunnus obesus) and skipjack (SKJ, Katsuwonus pelamis) - were compared by electrophoretic and western blot analyses to identify biomarkers for BT. As expected, SDS-PAGE patterns were species-specific but differences, due to BT, were observed only between some low ionic strength extracts of BET and YFT. Protein oxidation and cell proliferation analysed by immunoblotting did not show differences between BT and normal muscles. Gelatine zymography revealed different gelatinase activity patterns that, although not linked to BT, may affect the final texture of the muscle. A 43 kDa band, identified as creatine kinase by proteomic analysis, showed the potential to be a good indicator for BT in BET and YFT.