Journal of Aquaculture Research & Development

The unintended consequences of simplifying the Sea: Making the case for complexity

International Conference on Aquaculture & Fisheries

July 20-22, 2015 Brisbane, Australia

Leigh Michael Howarth

Posters-Accepted Abstracts: J Aquac Res Development

Abstract:

Many over-exploited marine ecosystems worldwide have lost their natural populations of large predatory finfish and have become dominated by crustaceans and other invertebrates. Controversially, some of these simplified ecosystems have gone on to support highly successful invertebrate fisheries capable of generating more economic value than the fisheries they replaced. Such systems have therefore been compared with monocultures created by modern agriculture on land, in that existing ecosystems have been converted into those that maximize the production of target species. It is however, widely recognized that monocultures are ecologically unstable. On land, crops and animals must be treated with a diverse array of chemicals and biological controls to maintain yields in the face of pests, weeds and diseases. Similar methods are also used in aquaculture but in the open sea, no such mechanisms exist. In this study, they explore the consequences of simplifying the sea and whether maintaining low-diversity conditions in the marine environment for our long-term exploitation is viable. By drawing on a number of concepts and case-studies we argue that, in many cases, the loss of large finfish has triggered dramatic ecosystem shifts to states that are both ecologically and economically undesirable and difficult and expensive to reverse. In addition, we find that those stocks left remaining are unusually prone to collapse from disease, invasion, eutrophication and climate change. We therefore conclude that the transition from multispecies fisheries to simplified invertebrate fisheries is causing a global decline in biodiversity and is threatening global food security, rather than promoting it.