Biofouling in marine aquaculture is a specific problem where both the target culture species and/or infrastructure are exposed to a diverse array of fouling organisms, with significant production impacts. In shellfish aquaculture the key impact is the direct fouling of stock causing physical damage, mechanical interference, biological competition and environmental modification, while infrastructure is also impacted. In contrast, the key impact in finfish aquaculture is the fouling of infrastructure which restricts water exchange, increases disease risk and causes deformation of cages and structures. Consequently, the economic costs associated with biofouling control are substantial. Conservative estimates are consistently between 5–10% of production costs (equivalent to US$ 1.5 to 3 billion yr−1), illustrating the need for effective mitigation methods and technologies. The control of biofouling in aquaculture is achieved through the avoidance of natural recruitment, physical removal and the use of antifoulants. However, the continued rise and expansion of the aquaculture industry and the increasingly stringent legislation for biocides in food production necessitates the development of innovative antifouling strategies. These must meet environmental, societal, and economic benchmarks while effectively preventing the settlement and growth of resilient multi-species consortia of biofouling organisms.

https://www.tandfonline.com/doi/pdf/10.1080/08927014.2012.700478

The impact and control of biofouling in marine aquaculture: a review

Human populations have been concentrated along and exploiting the coastal zones for millennia. Of regions with the highest human impacts on the oceans (Halpern et al. 2008), 6 of the top 10 have recently experienced blooms or problems with jellies. I review the time lines of human population growth and their effects on the coastal environment. I explore evidence suggesting that human activities—specifically, seafood harvest, eutrophication, hard substrate additions, transport of nonindigenous species, aquaculture, and climate change—may benefit jelly populations. Direct evidence is lacking for most of these factors; however, numerous correlations show abundant jellies in areas with warm temperatures and low forage fish populations. Jelly populations fluctuate in ∼10- and ∼20-year cycles in concert with solar and climate cycles. Global warming will provide a rising baseline against which climate cycles will cause fluctuations in jelly populations. The probable acceleration of anthropogenic effects may lead...

Jellyfish and Ctenophore Blooms Coincide with Human Proliferations and Environmental Perturbations

Aquaculture is the fastest-growing farmed food sector and will soon become the primary source of fish and shellfish for human diets. In contrast to crop and livestock production, aquaculture production is derived from numerous, exceptionally diverse species that are typically in the early stages of domestication. Genetic improvement of production traits via well-designed, managed breeding programmes has great potential to help meet the rising seafood demand driven by human population growth. Supported by continuous advances in sequencing and bioinformatics, genomics is increasingly being applied across the broad range of aquaculture species and at all stages of the domestication process to optimize selective breeding. In the future, combining genomic selection with biotechnological innovations, such as genome editing and surrogate broodstock technologies, may further expedite genetic improvement in aquaculture.

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Harnessing genomics to fast-track genetic improvement in aquaculture.

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.

Jellyfish (Cnidaria, Scyphozoa) blooms appear to be increasing in both intensity and frequency in many coastal areas worldwide, due to multiple hypothesized anthropogenic stressors. Here, we propose that the proliferation of artificial structures – associated with (1) the exponential growth in shipping, aquaculture, and other coastal industries, and (2) coastal protection (collectively, “ocean sprawl”) – provides habitat for jellyfish polyps and may be an important driver of the global increase in jellyfish blooms. However, the habitat of the benthic polyps that commonly result in coastal jellyfish blooms has remained elusive, limiting our understanding of the drivers of these blooms. Support for the hypothesized role of ocean sprawl in promoting jellyfish blooms is provided by observations and experimental evidence demonstrating that jellyfish larvae settle in large numbers on artificial structures in coastal waters and develop into dense concentrations of jellyfish-producing polyps.

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Is global ocean sprawl a cause of jellyfish blooms

Precision fish farming: A new framework to improve production in aquaculture

The development of biofouling, particularly the hydroid Ectopleura larynx, on commercial salmon cage nets in Mid-Norway

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.

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

The effects of colour and copper on the settlement of the hydroid Ectopleura larynx on aquaculture nets in Norway

The accumulation of biofouling organisms on farm infrastructure is an on-going problem for the global salmon aquaculture industry. Most salmon farmers in production regions worldwide undertake regular in situ net cleaning using specialised high-pressure washing rigs. Generally, the material removed from the net during cleaning is discharged into the surrounding environment. This 'cleaning waste' consists predominantly of biofouling organisms (intact and fragmented), but may also contain fish pathogens and antifouling coating particles containing bio- cides. The suspension, dispersal and deposition of this material are associated with a range of potential risks that can be grouped into 4 main categories: (1) health or disease risks (e.g. direct damage to sensitive tissues upon contact with cleaning waste, and facilitation of infection by patho gens); (2) deposition and pollution risks (impact on benthic communities around farms through deposition of organic material and antifouling biocides); (3) invasive species risks (localised dispersal of non-indigenous propagules and fragments); and (4) biofouling exacerbation (e.g. 'self-seeding' of downstream production cages). Here, we describe and discuss these 4 potential risks associated with in situ cleaning and present an agenda and research priorities to better understand and manage these risks.

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Leif Magne Sunde

Papers

Precision fish farming: A new framework to improve production in aquaculture

The development of biofouling, particularly the hydroid Ectopleura larynx, on commercial salmon cage nets in Mid-Norway

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

The effects of colour and copper on the settlement of the hydroid Ectopleura larynx on aquaculture nets in Norway

Potential environmental risks associated with biofouling management in salmon aquaculture