Abstract
The escape of fish from aquaculture is perceived as a threat to wild fish populations. The escapes problem is largely caused by technical and operational failures of fish farming equipment. In Norway, 3.93 million Atlantic salmon Salmo salar, 0.98 million rainbow trout Oncorhynchus mykiss and 1.05 million Atlantic cod Gadus morhua escaped from 2001 to 2009. Salmonids primarily escape after structural failures of containment equipment, while a far greater percentage of cod than salmon escape through holes in the nets. Correlative evidence suggests that after the Norwegian technical standard (NS 9415) for sea-cage farms took effect in 2004, the total number of escaped Atlantic salmon declined from >600 000 (2001 to 2006) to <200 000 fish yr -1 (2007 to 2009), despite the total number of salmon held in sea-cages increasing by 44% during this period. No similar decrease in escaped cod has occurred, suggesting that other measures, such as improved netting materials for sea-cages, are required. In addition to escaping as juveniles or adults, cod may reproduce in sea- cages, and thus fertilised eggs escape to the environment. The ecological effects of 'escape through spawning' are unclear, and methods to inhibit escape by this mechanism are being explored. To pre- vent escapes of juvenile and adult fish as sea-cage aquaculture industries develop, we recommend that policy-makers implement a 5 component strategy: (1) establish mandatory reporting of all escape incidents; (2) establish a mechanism to analyse and learn from the mandatory reporting; (3) conduct mandatory, rapid, technical assessments to determine the causes of escape incidents involving more than 10 000 fish; (4) introduce a technical standard for sea-cage aquaculture equipment coupled with an independent mechanism to enforce the standard; and (5) conduct mandatory training of fish farm staff in escape-critical operations and techniques.
Highlights
Definition of escapes from aquacultureEscapes of fish from sea-cage aquaculture have typically been thought of as referring to juvenile and adult fish
Such escapes have been reported for almost all species presently cultured around the world, including Atlantic salmon Salmo salar, Atlantic cod Gadus morhua, rainbow trout Oncorhynchus mykiss, Arctic charr Salvelinus alpinus, halibut Hippoglossus hippoglossus, sea bream Sparus aurata, sea bass Dicentrachus labrax, meagre Angyrosomus regius and kingfish Seriola lalandi (e.g. Soto et al 2001, Naylor et al 2005, Gillanders & Joyce 2005, Moe et al 2007a, Toledo Guedes et al 2009)
As most of the research and development on the escapes issue over the past 2 decades has been related to the Norwegian fish farming industry, we use Norway as a case study to describe the development and implementation of measures to deal with escapes
Summary
Escapes of fish from sea-cage aquaculture have typically been thought of as referring to juvenile and adult fish. Such escapes have been reported for almost all species presently cultured around the world, including Atlantic salmon Salmo salar, Atlantic cod Gadus morhua, rainbow trout Oncorhynchus mykiss, Arctic charr Salvelinus alpinus, halibut Hippoglossus hippoglossus, sea bream Sparus aurata, sea bass Dicentrachus labrax, meagre Angyrosomus regius and kingfish Seriola lalandi (e.g. Soto et al 2001, Naylor et al 2005, Gillanders & Joyce 2005, Moe et al 2007a, Toledo Guedes et al 2009). Aquacult Environ Interact 1: 71–83, 2010 cage facilities, or so-called ‘escape through spawning’ (Jørstad et al 2008) This phenomenon has forced a redefinition of the term ‘escapes from aquaculture’ to include the escapement of fertilised eggs into the wider marine environment
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