Fishing about and about fishing

MARINE FISH FARMING: PROBLEMS AND REMEDIES

 

Expansion. Marine farming is in the process of accelerating expansion worldwide. While the wild fish landings might’ve reached their maximum, it is quite possible that in a couple of decades the fish farming harvest would exceed them. It is only a matter of time, before additional hundreds of thousands of tonnes of fish grown in cages and saltwater ponds hit the world’s fish markets. All the more that the proliferating humanity is hungry for fish and its fish buying power keeps increasing.     

 

Problems. Lately, coastal cage farming is finding itself, much because of its impact on coastal ecosystems and capture fisheries, and on the socio-cultural fabric of fishing communities, under a growing pressure of environmental groups and fishing interests and of the ensuing restrictions and regulation. 

In spite of its promise, rather than increasing the overall food supply for a mushrooming human population, marine fish farming is mainly producing expensive species like salmon, tuna and shellfish directed at the more affluent consumer. 

Parasites and diseases spreading in the densely stocked fish cages and coastal marine ponds are often causing mass mortalities and great financial losses to the fish farming industry, while escapees from cages may carry them also to the vulnerable wild populations. According to some reports, each year around two million farmed fish escape in the Atlantic. Fishermen and environmentalists worry also of their interbreeding with wild stocks of the same and related species. 

Residual feed and bio-products pollute protected waters causing increased turbidity, and over shallow bottom - desertification. Complaints on the part of bathers and the tourist industry have forced some cage farms to transfer their operation ashore.

 

Farming planktivorous, herbivorous and omnivorous freshwater fish like grey mullet, tilapia, carp and catfish, and molluscs, like oysters and mussels is environmentally sounder. But the money is in carnivores, like tuna, salmon and cod. The need to feed them with small whole fish or fishmeal depletes populations of wild fish that serve as raw material. Raising one kg of a carnivorous fish requires fishmeal made of 3-4 kg of wild fish, which makes the fish-farming industry depending on the limited resources of “industrial” fish and competing with wild carnivores over this resource.

The U.S. administration to reduce a large fishery products import/export deficit is planning development and expansion of its floating fish farms offshore, quintupling fish farming yields by 2025. It intends to divide the 3 to 200 miles zone, which is under its federal control, into privatized sectors with renewable leases good for 10 years. It is generally assumed that if the fish farms are placed well offshore, oceanic currents would dilute and dispose of the pollution they produce, but not all agree..

The conflict is on and raging, and in view of the evident necessity of further expansion of marine farming, people are looking at technology. Unsurprisingly, some rather futuristic ideas have popped up.

 

Ocean drifters.  A team at the Massachusetts Institute of Technology is designing a giant motorized cage remotely operated, which is supposed to be carried by ocean currents, in a controllable manner. The idea is to keep  cages drifting within a limited area or along a desired path, so that they can be filled with fingerlings, for example in Florida, and drift in the Gulf Stream for nine months to reach Europe with a market-sized crop. The MIT’s drifter-cages would be fitted with low-power hydraulics or electric self propulsion to allow them to remain within the current and stay away from bad weather. Not being anchored over a fixed spot, there’ll be little benthic impacts.

 

Closed, integrated systems. Another promising development is integrated aquaculture, for example growing seaweed, salmon and mussels in one installation. The seaweed and mussels consume some of the waste from the salmon. This may be further integrated in a water-saving closed system where the fish are fed and produce nutrient rich waste. Solid fish waste is removed to feed, for example, worms bred for bait. The water with dissolved nutrient waste may then be piped to feed water-filtering shellfish and plants and then returned to the fish breeding section. Such system can be almost fully closed with very little additional water needed and no waste released. 

 

Sea ranching. Fisheries and Fishbreeding in Israel, a quarterly, published by the Israeli Fish Farmers Association in cooperation with the Department of Fisheries, (isimon@shaham.moag.gov.il. - www.amd.org.il), printed in its No 1, 2007, p.1058-1063, an article by B. Zion et al.: “Technologies for fish growers” (in Hebrew with English abstract). In their article a group of Israeli fish farmers and aquaculturists put forth an idea of fish ranching, which they call “virtual cage technology for farming of fish”. 

 

They propose to train juvenile fish in hatcheries to associate acoustic and visual signals with food. Trained fish are released to the sea to grow in nature, however, to perpetuate their response to the signals they’re fed periodically from floating platforms. At harvest time the acquired response would attract the fish to collection sites to be trapped and harvested selectively using a computerised vision system. 

 

The technology involved offers an alternative to cage farms and is almost neutral environmentally. It should be beneficial to fishermen and consumers, and may complement coastal cage culture and in some places replace it. This methodology would save investment in expensive offshore cage floating growth and service installations and feeding technology, and would require less running expenses for servicing and trained labour. 

 

Since the Israelis have already obtained good results in training fish to respond to signals and are moving to more advanced stages of their study, they hope to achieve both technical and economic feasibility.

 

No doubt, they’ll have to work only with fishes that tend to stay in one locality, grow fast enough in nature, and have a good value on the market. All this sounds quite futuristic, but hadn’t much of our present technologies sounded futuristic some decades ago?