What happens to the fish as our oceans get warmer?

  • Fishes
  • Other species
  • Targeted
  • Past
Years funded
  • 2021, 2022
  • Research

This study uses long-term reef fish survey data, by underwater visual census, from 2011 – 2017. Sarah will use the dataset to investigate differences in the reef fish community at different sites around the islands and assess annual changes in patterns of abundance at the site, considering which factors are causing these variations, with particular consideration of extreme climate events (ocean warming event in 2016).

What happens to the fish as our oceans get warmer?

Sarah Purvis

Project leader
About the project leader

Not to sound corny, but I have always been at one with the ocean and, according to my father, started swimming confidently at the age of four – thanks to his expert teaching skills, of course. But it was not until I visited D’Arros Island in 2014 on an educational trip with Island School Seychelles that the wonders of the ocean really appealed to me, especially the vibrant coral reefs. I remember snorkelling over one of the healthiest and most colourful and pristine reefs I had ever seen! After a week of intensive fun and highly informative activities, I went...

Project details

Investigating the impacts of a large-scale ocean warming event on reef fish community structure at a remote tropical site in Amirantes, Seychelles.

Key objective

To quantitatively assess the relative importance of annual changes in coral cover and environmental temperature on the diversity and abundance of the reef fish communities on the coral reefs of D’Arros and St Joseph.

Why is this important

Coral reefs are highly biodiverse ecosystems that provide important goods and services to many people worldwide. Despite their economic and ecological value, they are threatened by a suite of human-induced stressors. Of these, sea temperature rise that results in coral bleaching has arguably the most impact.

Research following past bleaching events suggests that reefs can recover from coral loss over timescales of decades if they are not affected again by mass bleaching or the presence of other anthropogenic stressors. However, current trajectories of global warming make this scenario seem unlikely. The 2015–2016 global coral reef bleaching event was the most persistent and widespread in history. In its aftermath, efforts are required to understand the extent of the post-bleaching coral mortality, the ability of reefs to recover and the consequences of bleaching on the reefs’ biodiversity.


Large-scale bleaching events affect the ecology of reef fish in a variety of ways. It is often difficult, however, to accurately disentangle the effects of coral bleaching from other co-occurring anthropogenic disturbances. Studying the effects of bleaching events in remote environments that remain isolated from other human disturbances is therefore valuable.

Previously published research has investigated the extent of changes to hard coral cover at different sites around the D’Arros and St Joseph island group in Seychelles in response to the 2016 global bleaching event and shown significant declines in coral cover during and after the event. Habitat features and environmental conditions are known to play a key role in structuring natural communities and yet the effects of climate-induced bleaching events on reef fish assemblages remain poorly understood. It is therefore important to investigate how the dramatic loss of coral cover impacts the fish communities inhabiting coral reefs. Understanding the response of reef fish to global warming is important for selecting appropriate criteria for evaluating reef resilience and informing future conservation strategy.

Aims & objectives

The aim of this study is to explore the relationships between tropical reef fish assemblages and environmental temperature and coral cover so as to better understand the impact of large-scale bleaching events on the structure and function of coral reef fish communities.

To do this, the study will address several specific objectives:

– describe patterns in the diversity and abundance of reef fish communities at a series of sites around D’Arros and St Joseph;

– assess annual changes in the diversity and abundance of reef fish communities at the site, with particular reference to the 2016 bleaching event;

– use multivariate analyses to evaluate trends in reef fish abundance and diversity in relation to environmental temperature and hard coral cover.