Plenty more fish in the sea? - Part One

As I write this, the world's foremost climatologists, ecologists and earth scientists are meeting in Berlin to decide whether or not the 'Anthropocene' should become an actual epoch. Originally conceived by Eugene F. Stoermer in the 1980s, the specifics of this anthropocentric period are highly contested. William Ruddiman, who will be making his case at UCL this coming Tuesday, asserts that humans have impacted the environment for thousands of years longer than the couple of hundred years since the industrial revolution usually cited as the Anthropocene. Regardless of the timescale, one thing is certain - present environmental conditions are such that human agency is an increasingly important factor and we are already beginning to see the effects of anthropogenic climate change.

A report by the International Fund for Agricultural Development (IFAD) identifies temperature as one of the climate change impacts on fisheries. Fish and most marine non-mammals are poikilotherms - they have no internal mechanism for heat regulation and are reliant on their surrounding environment to maintain an optimal body temperature. Therefore as climate change proceeds to increase ocean temperatures, fish and other organisms will migrate north to cooler waters in order to secure their optimal temperatures. An analysis of 50 fish species in UK and Irish waters found that 70% responded to increasing temperatures by changing their distribution, with an increase in typically warm-water species and a marked decline in colder-water species. In this scenario there will be winners and losers with fish migrating to higher latitudes, providing a larger marine stock. By contrast, tropical and warmer latitudes will experience a decline potentially threatening the livelihood of some of the poorest coastal communities.

Rising sea surface temperatures also poses a threat to marine habitats, which in turn disturbs fish ecosystems. Coral reefs provide a habitat for a variety of fish species, particularly in the vital juvenile stage of the life cycle. However, as temperatures rise they become increasingly susceptible to the process of coral bleaching and fish species are severely limited in their choice of spawning ground. On top of the pressures of temperature rise, coral reefs are vulnerable to the threat of ocean acidification, which will be discussed in the next post.

Welcome! You've come to the right plaice...

The importance of marine ecosystems in global food supply today is undeniable. Marine fisheries are assessed as contributing 80 million tonnes of protein a year to human diet, and offer a livelihood for 8% of the world's population. Fish is particularly important in developing countries, acting as a vital source of protein for growth and development where meat is otherwise unavailable or expensive. But demand for this vital food source is not static - demand for fish is forecast to increase in line with the expanding population and improving levels of economic development.

Fisheries as a food source have the potential to achieve the resource sustainability in food supply that we desperately need. This diagram from National Geographic represents the quantity of feed mass required to produce a pound of body mass. At 1.1 pounds of feed, fish is clearly more efficient than chicken, pork or beef and seems a suitable candidate for a resource-stretched future. However, while a mass global dietary shift towards fish may be efficient, it is also difficult to attain under present circumstances. And let's face it - who wants to eat nothing but fish?

The pressures that climate change poses to fish stocks and global fish supply are still not fully understood, and will only make a bad situation worse. Fisheries are in quite dire straits due to human over-exploitation coupled with a limited understanding of marine ecosystem dynamics. Global marine catch peaked in 1996 and has been in decline ever since, and it is now thought that as many as 64% of global fisheries are in a state of over-exploitation.

It's clear therefore that if fish is to remain a staple source of protein and nutrients in the human diet it is important to understand the threats posed to global fish supply and the actions we can take to limit them. The purpose of this blog is not to offer a comprehensive solution to the problems facing fisheries - I can assure you that I'm hopelessly under-qualified for such an undertaking. Instead, over the coming weeks this blog will examine the science behind climate change and fisheries as well as exploring proposed and implemented management strategies. And of course, no geographical inquiry will be complete without a healthy dose of case studies, so you can look forward to (I use that phrase reluctantly) analyses of marine and fluvial ecology.

Please feel free to comment and contribute, and hopefully we can start insightful discussion regarding this crucial resource!