J. P. McVey

Responsible marine aquaculture

With the expansion of the world aquaculture industry, there has been increasing concern over sustainability and environmental impact. This book addresses this topical issue, concentrating on marine aquaculture. Chapters have been developed from a meeting of the World Aquaculture Society, held in Florida in January 2001, although additional contributions have also been commissioned. There is a focus on: minimal net utilization of natural resources; the production of healthy products for food; appropriate regulations and policies; and there are case studies from various geographical settings, including North and Latin America, Asia and the Pacific.

Marine Mammals and Aquaculture: Conflicts and Potential Resolutions

Two main types of marine-based aquaculture come into potential conflict with marine mammals (and, in some areas, marine turtles and seabirds): (i) extensive raising of shellfish, such as oysters, mussels and shrimp; and (ii) intensive raising of finfish, such as salmon, sea bass and sea bream. The first takes up space in near-shore waters but does not generally require nets or cages that can entangle or otherwise hurt airbreathing vertebrates. It also does not require supplementary feeding, and therefore is not generally a major attractant for marine mammals and others. However, shellfish aquaculture puts extra nitrogen into the ecosystem, and can change local ecology where tidal and other flushing is minimal. It takes up extensive space in inlets, fjords and the like, and may compete for limited habitat access with foraging, resting, socializing and nurturant mammals. The intensive but generally more localized farming of finfish often requires supplementary feeding, and both the stock in holding pens and the feed serve as powerful attractants especially to pinnipeds (but toothed cetaceans, river and sea otters, marine turtles, and seabirds are often involved as well). As such, major problems are caused to the industry by destruction of gear and the target aquaculture species; and to the marine animals by shooting and other techniques, such as large-scale use of Acoustic Deterrent Devices (ADDs) and Acoustic Harassment Devices (AHDs). No technique has proved highly successful, and the widespread use of ADDs and AHDs is particularly problematic and largely untested. We recommend that owing to potential for entanglement, chemical and sound pollution, habitat loss or gross alteration, traffic, and changes in species interactions, all proposed development of marine aquaculture in nature should be subjected to initial evaluations and – as needed – scientific research relative to interactions between the food being raised by humans and the predators that attempt to take advantage of this. The loss of habitat to marine

Understanding the interaction of extractive and fed aquaculture using ecosystem modelling.

One of the most difficult tasks resource managers face is understanding the carrying capacity of coastal waters for aquaculture. Aquaculture, like many other human activities, can threaten coastal waters. Understanding eutrophication and the interaction of two different types of aquaculture is very important to the safe and effective management of coastal aquaculture. The first type of aquaculture, producing shrimp CAB International 2002. Responsible Marine Aquaculture (eds R.R. Stickney and J.P. McVey) 263 and finfish, depends on supplemental feeding and can contribute to eutrophication. The second type, involving bivalve molluscs and macroalgae, extracts plankton and nutrients from surrounding waters and can have a significant positive impact on moderately eutrophic waters. These species depend on the water’s basic productivity and will not grow effectively in water with low nutrient levels. Balancing extractive and fed aquaculture is of obvious importance to maximizing the safety and optimizing the carrying capacity of an embayment. Ecosystem modelling offers a three-dimensional physical, chemical and biological simulation that can help scientists and managers understand and predict the eutrophic impact of aquaculture for a specific embayment. Such a model is being explored in China in research sponsored by the Sino-US Living Marine Resources Panel. In this study, two projects are using the model to simulate the impact of aquaculture on Jiaozhou Bay, Shangdong Province, and on Xincun Lagoon, Hainan Province. Jiaozhou Bay is in the temperate zone adjacent to the Yellow Sea. There, a major port and industrial city, Qingdao, and scallop and shrimp aquaculture interact with the physical and biological components of the bay. The other modelled environment is very different. Xincun Lagoon is a small embayment (~22 km2) in southeastern Hainan Island adjacent to the South China Sea. Aquaculture in Xincun Bay includes 6500 fish pens (3 m × 3 m), 100 ha of shrimp ponds, pearl culture rafts and a new macroalgae culture operation that produced 3500 tonnes of Eucheuma in 1998–1999. The surrounding area has ~15,000 people and Xincun City is a major offshore fishing port (~500 vessels, > 10 m length) and Monkey Island Wildlife area with > 400,000 visitors annually. Extractive and fed aquaculture, along with the external activities, all have an impact on the carrying capacity of the bay for aquaculture. These two models show much promise for simulating local eutrophic conditions and for increasing the general understanding of the complex interactions of aquaculture and other human activities. Models that simulate the impact of aquaculture and other human activities and eventually predict carrying capacity should become useful tools for resource managers.