Warming seas drive worldwide population trajectories of marine fishes

Abstract

Climate warming is expected to lead to widespread changes to marine fish populations. In Chapter 1 of this thesis, I review how rising sea surface temperatures alter the physiological performance of fishes in their local environment, ultimately driving species-level range shifts and changes to community structure. I examine how population responses to warming seas are mediated by species traits and interspecific interactions, and consider the consequences of altered species distributions for fisheries and conservation planning. In Chapter 2 of this thesis, I present a large-scale investigation of marine fish responses to warming seas. I compiled and analysed 144,661 population abundance time series from 42 surveys conducted over 62 years (1963-2024), comprising 2,669 fish species, across pelagic, benthic and reef habitats. I coupled these time series with monthly sea-surface temperature records to quantify abundance–temperature relationships. Using global species range data and binomial generalised linear mixed models, I tested whether the position of a population within its species’ latitudinal range predicted its response to warming. The results revealed a globally coherent pattern of populations being more likely to respond positively to warming at the poleward side of their range and respond negatively to warming at the equatorward side of their range. This pattern was clearest in longer time-series, and amplified in species with faster growth rates, greater fecundity and smaller body sizes. At the community level, models show that over two-thirds of marine fish communities exhibited this pattern, collectively demonstrating a globally coherent fingerprint of climate warming. Based on the findings reported in this chapter, I suggest that warming will drive further changes to community structure at a global scale, with implications for fisheries and marine conservation.

Date of Award	20 Jan 2026
Original language	English
Awarding Institution	University of Bristol
Supervisor	Martin J Genner (Supervisor) & Hugo B Harrison (Supervisor)