was estimated at 36.1 million tons with a value of US$37.9 billion (FAO 2012).
Nearly all ocean farming is conducted inshore, in contrast to offshore aquaculture
that is still in its infancy. Offshore aquaculture may be defined as taking place in
areas of the open ocean exposed to significant wind and wave action, and where
there is a requirement for equipment and servicing vessels to survive and operate in
severe sea conditions from time to time (Drumm 2010).
There is an obvious, demand-driven need to develop offshore aquaculture
throughout the world. However, one of the most difficult obstacles to overcome is
finding locations for new aquaculture farms. Because of the difficulties associated
with inshore locations, it is assumed that most new aquaculture activities will be
developed offshore in the Exclusive Economic Zone (3–200 miles) where there are
fewer conflicts with existing user groups, and less risk of pollution. The high energy
(winds and waves) of such exposed locations, however, present significant technical
challenges in the design, testing and construction of aquaculture systems that are
capable of surviving in these areas. In addition to these technical challenges, there
are many biological, regulatory, social and economic problems to be solved.
Despite, drivers at local and global levels provide impetus for aquaculture to
move to these unprotected waters of the open sea. There are issues of competition
for space with other users, problems with water quality, and oftentimes there is a
negative public perception of aquaculture’s environmental and aesthetic impacts
(Kapetsky et al. 2013). Some of these conflicting issues are also common to the
offshore wind energy and oil industry. The oil/gas industry has a long history of
installed facilities in offshore locations. The recent pressure to reduce carbon
dioxide emissions has additionally leveraged the worldwide planning and installation of offshore wind energy converters. Countries bordering the North and Baltic
Sea with limited accessibility of inland building sites such as Denmark, Great
Britain or Germany started exploring offshore wind energy feasibility in the end of
the eighties (Hau and von Renouard 2006). High energy cost and natural disasters
facilitated this development. It is thus natural to assess if foundation structures
(piles, tripods, jackets) of existing or licensed wind energy sites could be co-used
for additional economic activities such as offshore aquaculture.
Aquaculture migration towards offshore sites has undergone substantial progress
in the last two decades. This progress was leveraged by advances in numerical and
physical modelling of various fish cages or long line arrangements as well as by
technological developments and prototype sites. In order to design an open ocean
aquaculture test site near the south of the Isles of Shoals, New Hampshire a
numerical model was used by Tsukrov et al. (2000) to optimize the structure. Finite
element analysis was applied to study the performance of surface and submerged
constructions and a simplified formulation for the simulation of the nets is presented. An improved formulation was presented by Tsukrov et al. (2003) offering a
consistent net element which is generally capable to model fluid action and net
inertia of fishing nets and allows to simulate environmental loadings originating
from currents, waves or other mechanical impacts. Motivated by the impact of
storm-waves to aquaculture facilities, a lump-mass method was used to study to the
3 Technological Approaches to Longline- and Cage-Based …
73
Nearly all ocean farming is conducted inshore, in contrast to offshore aquaculture
that is still in its infancy. Offshore aquaculture may be defined as taking place in
areas of the open ocean exposed to significant wind and wave action, and where
there is a requirement for equipment and servicing vessels to survive and operate in
severe sea conditions from time to time (Drumm 2010).
There is an obvious, demand-driven need to develop offshore aquaculture
throughout the world. However, one of the most difficult obstacles to overcome is
finding locations for new aquaculture farms. Because of the difficulties associated
with inshore locations, it is assumed that most new aquaculture activities will be
developed offshore in the Exclusive Economic Zone (3–200 miles) where there are
fewer conflicts with existing user groups, and less risk of pollution. The high energy
(winds and waves) of such exposed locations, however, present significant technical
challenges in the design, testing and construction of aquaculture systems that are
capable of surviving in these areas. In addition to these technical challenges, there
are many biological, regulatory, social and economic problems to be solved.
Despite, drivers at local and global levels provide impetus for aquaculture to
move to these unprotected waters of the open sea. There are issues of competition
for space with other users, problems with water quality, and oftentimes there is a
negative public perception of aquaculture’s environmental and aesthetic impacts
(Kapetsky et al. 2013). Some of these conflicting issues are also common to the
offshore wind energy and oil industry. The oil/gas industry has a long history of
installed facilities in offshore locations. The recent pressure to reduce carbon
dioxide emissions has additionally leveraged the worldwide planning and installation of offshore wind energy converters. Countries bordering the North and Baltic
Sea with limited accessibility of inland building sites such as Denmark, Great
Britain or Germany started exploring offshore wind energy feasibility in the end of
the eighties (Hau and von Renouard 2006). High energy cost and natural disasters
facilitated this development. It is thus natural to assess if foundation structures
(piles, tripods, jackets) of existing or licensed wind energy sites could be co-used
for additional economic activities such as offshore aquaculture.
Aquaculture migration towards offshore sites has undergone substantial progress
in the last two decades. This progress was leveraged by advances in numerical and
physical modelling of various fish cages or long line arrangements as well as by
technological developments and prototype sites. In order to design an open ocean
aquaculture test site near the south of the Isles of Shoals, New Hampshire a
numerical model was used by Tsukrov et al. (2000) to optimize the structure. Finite
element analysis was applied to study the performance of surface and submerged
constructions and a simplified formulation for the simulation of the nets is presented. An improved formulation was presented by Tsukrov et al. (2003) offering a
consistent net element which is generally capable to model fluid action and net
inertia of fishing nets and allows to simulate environmental loadings originating
from currents, waves or other mechanical impacts. Motivated by the impact of
storm-waves to aquaculture facilities, a lump-mass method was used to study to the
3 Technological Approaches to Longline- and Cage-Based …
73