Making the Most of Fish Farms

Abstract

M aking the M ost of F ish F arms B S J Julian Zhu When most people hear the word ‘fish,’ they think of food. In 2009, the Food and Agriculture Organization (FAO) of the United Nations reported world consumption of fish at 117.8 million tons, up more than fifteen million from 2004 (FAO, 2009). Fish, to all but the most dedicated ichthyologist, are represented primarily by dish, taste, and breed: salmon, Atlantic cod, tuna, and the like. However, the prospects of fish as a means of feeding a growing world population are beginning to look more and more perilous. By now, most educated citizens have some idea of the devastation overfishing has caused on wild fish stocks. Overfishing – or harvesting more fish than natural reproduction can sustain – has been prevalent on a global scale for decades, but only recently has the collapse of fish stocks worldwide drawn widespread political attention. Aquaculture – the farming of marine species (primarily fish, but also crustaceans, sea plants, and other marine Figure 1. Nile tilapia, a popular aquaculture fish breed. organisms) – offers a possible alternative to traditional capture, one that could not only ease the burden on wild fish populations, but play a significant role in feeding a growing world population. Despite its promise, however, aquaculture in its current state is far from the perfect solution to providing fish to the world both sustainably and economically. The environmental impact of fish farms as well as the pitfalls of economic inefficiency demand that aquaculture be inspected with a discerning and skeptical eye. Aquaculture on an industrial scale is still a relatively new phenomenon, and monitoring its impacts – both the obvious and hidden – is a responsibility that both potential fish-farmers and policymakers ought to assume. Different fish species are chosen for aquaculture for a variety of reasons, from taste and economic value to hardiness and ease of growth. Of fish species, tilapia is rising as a strong contender for the title of the most popular and aquaculture-viable strain (Bradford, 2011). Similarities in taste and texture between tilapia and Atlantic cod – one of the most popular and heavily overfished fish species “Aquaculture offers a possible alternative to [...] capture” consumed today – make tilapia meat a viable substitute for the overfished cod in most cases, and is therefore growing in market value. More critically, however, tilapia is both hardy and easy to grow, with a flexible diet and relatively high tolerance to environmental factors such as salinity and temperature. That said, the very qualities that make tilapia such a highly valued aquaculture fish make it an extremely potent invasive species. High rates of reproduction and growth, paired with a tolerance to everything but the lowest temperatures, make Mozambique tilapia – the most common strain of farmed tilapia found today – dangerous invaders in tropical and subtropical environments; additionally, tilapia exhibit strong parental care that includes housing young in the parent’s mouth, granting tilapia spawn a far greater range of mobility than that of other fish breeds (Costa-Pierce, 2003). Due to these factors, invasive tilapia have already penetrated ecosystems in Florida, California, and elsewhere, outcompeting native species and presented a serious threat to native biodiversity. For this reason, fish farmers in the United States are seeking to replace the Mozambique strain with Nile tilapia, an easier-to-raise, less aggressively invasive variety. Furthermore, genetic manipulation of aquaculture species targets the precise traits that make fish strains better invaders: increased growth rate, size, and reproductive ability. In addition to threatening ecosystems, aquaculture also raises a significant question about its economic efficiency. If aquaculture is to be marketed as the sustainable 1 • B erkeley S cientific J ournal • S cience of F ood • V olume 16 • I ssue 1