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.

https://www.int-res.com/articles/aei2010/1/q001p071.pdf

Escapes of fishes from Norwegian sea-cage aquaculture: causes, consequences and prevention.

Food production is responsible for a quarter of anthropogenic greenhouse gas (GHG) emissions globally. Marine fisheries are typically excluded from global assessments of GHGs or are generalized based on a limited number of case studies. Here we quantify fuel inputs and GHG emissions for the global fishing fleet from 1990–2011 and compare emissions from fisheries to those from agriculture and livestock production. We estimate that fisheries consumed 40 billion litres of fuel in 2011 and generated a total of 179 million tonnes of CO2-equivalent GHGs (4% of global food production). Emissions from the global fishing industry grew by 28% between 1990 and 2011, with little coinciding increase in production (average emissions per tonne landed grew by 21%). Growth in emissions was driven primarily by increased harvests from fuel-intensive crustacean fisheries. The environmental benefit of low-carbon fisheries could be further realized if a greater proportion of landings were directed to human consumption rather than industrial uses.

Fuel use and greenhouse gas emissions of world fisheries

http://publications.lib.chalmers.se/records/fulltext/232360/local_232360.pdf

How can the EU climate targets be met? A combined analysis of technological and demand-side changes in food and agriculture

Many native Atlantic salmon populations have been invaded by domesticated escapees for three decades or longer. However, thus far, the cumulative level of gene-flow that has occurred from farmed to wild salmon has not been reported for any native Atlantic salmon population. The aim of the present study was to investigate temporal genetic stability in native populations, and, quantify gene-flow from farmed salmon that caused genetic changes where they were observed. This was achieved by genotyping historical and contemporary samples from 20 populations covering all of Norway with recently identified single nucleotide polymorphism markers that are collectively diagnostic for farmed and wild salmon. These analyses were combined with analysis of farmed salmon and implementation of Approximate Bayesian computation based simulations. Five of the populations displayed statistically significant temporal genetic changes. All five of these populations became more similar to a pool of farmed fish with time, strongly suggesting introgression of farmed fish as the primary cause. The remaining 15 populations displayed weak or non-significant temporal genetic changes. Estimated introgression of farmed fish ranged from 2-47% per population using approximate Bayesian computation. Thus, some populations exhibited high degrees of farmed salmon introgression while others were more or less unaffected. The observed frequency of escapees in each population was moderately correlated with estimated introgression per population R2 = 0.47 P < 0.001. Genetic isolation by distance existed within the historical and contemporary data sets, however, the among-population level of divergence decreased with time. This is the first study to quantify cumulative introgression of farmed salmon in any native Atlantic salmon population. The estimations demonstrate that the level of introgression has been population-specific, and that the level of introgression is not solely predicted by the frequency of escapees observed in the population. However, some populations have been strongly admixed with farmed salmon, and these data provide policy makers with unique information to address this situation.

/pdf/atlantic-salmon-populations-invaded-by-farmed-escapees-3s3xq7kvnr.pdf

Atlantic salmon populations invaded by farmed escapees: quantifying genetic introgression with a Bayesian approach and SNPs.

In this article, the definition of sustainability is discussed, particularly in relation to the use of marine feed resources. The current review gives an overview of the development of Atlantic salmon (Salmo salar) aquaculture and how it has evolved due to changes in legal and management framework conditions. Atlantic salmon production is characterized with high utilization of nutrients, a high yield of production, and a large demand for rendered by-products. All of these factors compare favorably to production of most terrestrial farm animals. Historically, salmon feed has contained fishmeal and fish oil as the primary protein and fat source. Rising demand for feed ingredients has not increased pressure on forage fish resources. Rather, there has been an increased use of plant protein and fat sources. Increased utilization of plant ingredients may not be as sustainable as often claimed. Provided that marine harvest is carried out within legal frames, harvesting the marine ecosystem is a sustainable opera...

http://www.aquahana.com/wp-content/uploads/2015/10/2011RevFishSci2.pdf

Atlantic Salmon (Salmo salar): The “Super-Chicken” of the Sea?

Summary
Greenhouse gas emissions caused by food production are receiving increased attention worldwide. A problem with many studies is that they only consider one product; methodological differences also make it difficult to compare results across studies. Using a consistent methodology to ensure comparability, we quantified the carbon footprint of more than 20 Norwegian seafood products, including fresh and frozen, processed and unprocessed cod, haddock, saithe, herring, mackerel, farmed salmon, and farmed blue mussels. The previous finding that fuel use in fishing and feed production in aquaculture are key inputs was confirmed. Additional key aspects identified were refrigerants used on fishing vessels, product yield, and by-product use. Results also include that product form (fresh or frozen) only matters when freezing makes slower transportation possible. Processing before export was favorable due to the greater potential to use by-products and the reduced need for transportation. The most efficient seafood product was herring shipped frozen in bulk to Moscow at 0.7 kilograms CO2 equivalents per kilogram (kg CO2-eq/kg) edible product. At the other end we found fresh gutted salmon airfreighted to Tokyo at 14 kg CO2-eq/kg edible product. This wide range points to major differences between seafood products and room for considerable improvement within supply chains and in product choices. In fisheries, we found considerable variability between fishing methods used to land the same species, which indicates the importance of fisheries management favoring the most resource-efficient ways of fishing. Both production and consumption patterns matter, and a range of improvements could benefit the carbon performance of Norwegian seafood products.

The Carbon Footprint of Norwegian Seafood Products on the Global Seafood Market

The main goal of this PhD project was to develop a method for non-linear strength analysis of net structures applied in the aquaculture and fishing industries, e.g. net cages and trawls. The work focused on the aquaculture net cage, which was applied in experiments and analyses, and included research to establish knowledge within material properties and failure modes of traditional netting materials for aquaculture. It was chosen to focus on tensile properties and to study elastic and plastic behaviour, fracture, creep behaviour and cod bite damage. The project consisted of three main activities: tensile testing of netting materials, studies and testing of cod bite damage and resistance, and structural analysis of aquaculture net cages. Net cages are built as a system of ropes and netting. They are designed to transfer and carry all major forces through the ropes. Loads from current, waves, weights and handling induce forces in the net cage, which must be dimensioned to withstand this. Analyzing an aquaculture net cage is both complex and time consuming due to non-linear effects, detailed geometry and dynamic loads. The behaviour of the net cage is dominated by very large deformations and displacements, and materials with non-linear properties. There is a need for verified analysis methods and specific guidance on how to reduce the complexity of a net cage analysis. In order to perform a strength analysis of a net cage, it is crucial to know the material properties of the netting material. Traditionally, the material property of major interest for the aquaculture industry has been the tensile breaking strength of netting (mesh) and ropes, and comparatively little focus has been on their detailed stiffness properties and general behaviour prior to fracture. A new test method was established to determine the uniaxial tensile properties of knotless netting materials. It was applied on a variety of netting materials and stress-strain relations were developed. Data on temporary creep properties, recovery of strain post creep and post creep tensile properties of a selection of Raschel knitted netting materials was presented. Post creep tensile testing showed that the length and force at break were not significantly affected by the creep load history. Cod farmers have reported that cod interact with the cage netting through biting and thereby create wear and tear. The nature of the cod bite attack on traditional, multifilament netting materials was described based on studies of cod interaction with traditional knotless netting and resulting fracture damage on netting fibres. Field experiments were performed, subjecting panels of netting to cod bite in commercial cod cages. In addition, a test method was developed to simulate damage on traditional netting from cod bite, and a prototype bite-jig was designed and assembled. It was concluded that netting materials for cod aquaculture must be resistant to cod bite or be repellent or uninteresting for cod. A method for numerical analysis of net cages in constant uniform current was developed and verified for limited solidity, deformations and current velocities. Various new designs for aquaculture net cages were presented and compared to a traditional net cage with regard to stresses in the netting material and deformation of the net cage.

Ulf Winther

Papers

The Carbon Footprint of Norwegian Seafood Products on the Global Seafood Market

Technological solutions and operational measures to prevent escapes of Atlantic cod (Gadus morhua) from sea cages

Carbon footprint and energy use of Norwegian fisheries and seafood products

The Norwegian seafood industry – Importance for the national economy

Greenhouse gas emissions of Norwegian seafoods: From comprehensive to simplified assessment