David Sims (biologist)

Beginning in 1995 Sims studied the behavioural ecology of the plankton-feeding basking shark, the world's second largest fish.[10] He showed from long-term field studies of behaviour and satellite tracking that basking sharks feed on specific assemblages of zooplankton and do not hibernate in winter,[11][12][13] overturning an understanding which had stood for nearly 50 years.[14] Sims' satellite tracking of basking sharks were some of the first long-term trackings of any shark species[15] and contributed directly to successful conservation proposals to list basking sharks on Appendix II of the Convention for International Trade in Endangered Species (CITES) (Feb 2003)[16][17] and the Convention for the Conservation of Migratory Species of Wild Animals (CMS) (Nov 2005).

Basking sharks were also studied to find out how fish actually respond to variations in zooplankton prey density gradients in the ocean, showing basking sharks were useful as 'biological plankton recorders', results which were published in the journal Nature.[18] Results have demonstrated the biological significance of ocean fronts to predators,[19] which have potential as candidates for high-seas protected areas.[10]

Since 2001, Sims has also made significant contributions[20] to understanding of climate change impacts on fish populations, including how climate-driven warming has altered migration timings,[21][22] dramatic community changes of European marine fish,[23][24] and vertical habitat compression of sharks due to ocean deoxygenation which can increase vulnerability to longline fishing.[25]

Research has identified common scaling laws that describe movement paths and behaviour patterns of marine predators.[26][27][28][29][30]

It is argued that Sims' work has provided the strongest empirical evidence[31][32][33] for the existence of movement patterns that are well approximated by biological Lévy flights and Lévy walks, a special class of random walk that theoretically optimise random searches for sparsely distributed resources.[34] It is said that Sims' work has shifted the debate on biological Lévy walks from whether they exist, to how and why they arise.[32][33] He also conducted the first empirical field tests of the Lévy flight foraging hypothesis.

In the book Bursts: The Hidden Pattern Behind Everything We Do, the physicist and best-selling author Albert-László Barabási writes: "Yet if a Lévy flight offers the best search strategy, why didn’t natural selection force animals to exploit it? In February 2008 David Sims showed that it did, in fact."

Sims' 2008 Nature paper announcing the discovery of Scaling laws of marine predator search behaviour is a Web of Science Highly Cited Paper. Since then additional evidence for biological Lévy walks has accumulated across a wide range of taxa including microbes and humans[35] and in fossil trails of extinct invertebrates,[36] suggesting an ancient origin of the movement pattern. His work contributes to the emerging understanding[37] in animal movement ecology that normal diffusion is insufficient for describing natural movements such as searching behaviour but that anomalous diffusion is required.

His studies published in Nature on Lévy and Brownian searches in ocean predators[26][27] inspired the optimal-foraging decision process used in an optimisation algorithm – the "Marine Predators Algorithm"[38] – a high-performance optimizer with applications to engineering and medicine, including electrical modeling of photovoltaic power plants,[39] renewable-energy systems design,[40] and COVID-19 x-ray image classification.[41]

In 2016 Sims led an international team tracking ocean-wide movements of sharks. They found pelagic sharks like the shortfin mako aggregate in space-use "hotspots" characterized by fronts and high plankton biomass.[42] Data showed longline fishing vessels also targeted the habitats and efficiently tracked shark movements seasonally, leading to an 80% spatial overlap. The work suggests current hotspots are at risk from overfishing and argued for introduction of international catch limits. The results were reported widely in the media including in The Times newspaper[43] and the journal Science.[44]

He initiated the Global Shark Movement Project, an international collaboration of research groups across 26 countries. The database assembled contains over 2,000 satellite tracks of sharks and is used "to find out where sharks aggregate, how distributions are influenced by environmental variations, and the global overlap with anthropogenic threats such as fisheries".

In 2019 the team published its first results in Nature reporting a global spatial risk assessment of sharks.[45] They showed nearly one quarter of shark space-use hotspots overlap with longline fisheries each month, rising to over 60% each month for commercially valuable sharks (like shortfin mako) and internationally protected species (like great white shark). Shark hotspots were also associated with significant increases in fishing effort, leading the team to conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). They suggest large-scale marine reserves centred on shark hotspots could help to limit shark exploitation on the high seas. The paper was reported worldwide including by the BBC,[46] CNN[47] and NPR.[48]

It has been commented[49] that the paper has "provided a much-needed blueprint for conservation actions that could be used to provide sharks with safe havens in our increasingly crowded oceans".