Aquaculture on Leonard Lopate

Today The Leonard Lopate Show on WNYC featured a segment called “The Future of Fish” with Bryan Walsh  of Time Magazine. Walsh recently published a cover story in Time about the worldwide rise of aquaculture, the practice of raising domesticated fish for human consumption.

There was a lot of valuable information covered in the segment, and Walsh proved himself as a journalist with thorough understanding of his subject. He correctly asserts that fish are the last wild-caught animal food that we consume in large amounts, and that the inevitable trend as we deplete our fisheries is to replace lost wild populations with domesticated varieties grown in fish farms.

There was some quality ecology in the interview, as Walsh pointed out how the fish species we choose to domesticate influence the impact of aquaculture. If we insist on farming the same species that we currently catch wild, aquaculture will only expand the already-great impact we have on wild fisheries. For example, salmon are a mid- to top-level predator in their marine environment, so raising captive salmon requires that we feed them large amounts of fish lower in the food chain. Whether these fish are caught wild (which decreases the resource base available to wild predator species) or grown through aquaculture (requiring large inputs of some other food source), feeding fish to fish is terribly inefficient. Walsh pointed out that particular species are being developed for aquaculture that can be fed conventional vegetable feed or feed waste; this is far more prudent because domesticated fish that are herbivores will be far less costly to raise (notice how all our major domesticated animals are herbivores?). Walsh mentioned that some researchers are trying to create “integrated aquaculture systems” in which waste products from primary fish production are utilized by other species (such as bivalves or crustaceans) that can also be harvested. Creating a ‘mini ecosystem’ within fish farms has the potential to lower their impact by departing from the model of expensive inputs and damaging outputs used in conventional terrestrial farming.

Walsh also did not gloss over the real threats that aquaculture presents. He acknowledged that mangrove forests are targeted for the creation of fish farms, and discussed briefly one of the ecosystem services (storm surge protection) that these critical biomes provide. He also discussed how escapees from fish farms (such as carp) can wreak havoc on local ecosystems.

I also appreciated that Walsh very explicitly pointed out that aquaculture cannot develop using the model of modern terrestrial agriculture, whose resource-intensive unsustainable methods are in part responsible for declines in marine fisheries (mostly through the process of eutrophication). He went so far as to say that we need to regulate aquaculture now before the industry expands enough to lobby away prudent regulation, a bold but I think appropriate suggestion (especially coming from a journalist).

The segment also had interesting bits on how the perspectives of differing stakeholders affect fisheries management and how lowered supply, increased demand, and rising prices create a positive feedback loop that encourage fisheries depletion.

I admire Leonard Lopate for his scientific curiosity, but he can be frustrating to listen to because he makes a lot of scientific gaffs. In this segment he equated the use of vaccinations in fish farms with the use of antibiotics on livestock, two practices which could have negative consequences but are nonetheless not analogous (vaccines train the animal’s immune system to fight off pathogens whereas antibiotics directly fight the pathogens and therefore are much more likely lead to the evolution of resistant pathogens). The problem with these gaffs is that often guests either miss them or politely ignore them, allowing Lopate to potentially mislead his audience. Although it is valuable to have the media be curious, it takes an informed journalist to guide his audience through technical topics.