As one of the largest growing food industries
globally, Aquaculture is a field that needs to adapt to become
more sustainable. Aquaculture is the practice of growing and
harvesting aquatic animals for human consumption. The practice
has become more controversial in the last decade with its rapid
growth. One way that is being explored to make aquaculture more
sustainable is bi-valve farming. Bivalves is a group of aquatic
creatures that includes mussels, clams, and oysters. They are
filter feeding organisms capable of filtering up to 50 gallons
of water a day per individual thereby increasing water clarity,
allowing sunlight to penetrate which in turn facilitates
seagrass growth and other organisms.
Shellfish cultivation and harvesting is an essential part of the
US and global seafood industry with an estimated value at $340
million in the US. In the past, bivalves were harvested by hand
initially as a subsistence farming product in shallow coastal
waters. Later on, they were retrieved using treading, short
rakes and hand operated rakes. While these methods are still
used, more efficient, less labor-intensive methods are being
researched in order to increase productivity and continue to
grow the practice of cultivating bivalves. These practices are
also improved in order to lessen the negative impact on the
surrounding environment. Essential aspects of shellfish
harvesting which have room for technological advancement may
include dredging, workboat conversions, and hatchery techniques
The Research & Development Tax Credit
Enacted in 1981, the now permanent Federal Research and
Development (R&D) Tax Credit allows a credit that typically
ranges from 4%-7% of eligible spending for new and improved
products and processes. Qualified research must meet the
following four criteria:
- Must be technological in nature
- Must be a component of the taxpayers business
- Must represent R&D in the experimental sense and
generally includes all such costs related to the development
or improvement of a product or process
- Must eliminate uncertainty through a process of
experimentation that considers one or more alternatives
Eligible costs include U.S. employee wages, cost of supplies
consumed in the R&D process, cost of pre-production testing,
U.S. contract research expenses, and certain costs associated
with developing a patent.
On December 18, 2015, President Obama signed the PATH Act,
making the R&D Tax Credit permanent. Beginning in 2016, the
R&D credit can be used to offset Alternative Minimum tax for
companies with revenue below $50MM and for the first time,
pre-profitable and pre-revenue startup businesses can obtain up
to $250,000 per year in payroll taxes and cash rebates.
Dredging is the process of harvesting various species which
reside in the seabed. More contemporary methods of on-bottom
shellfish cultivation include mechanical and hydraulic dredging.
Mechanical dredges scrape the seafloor with chain link bag towed
behind the workboat. This dredging method has become an industry
standard since the 1970s. Hydraulic dredges involve using
pressurized water to loosen the sediments and remove the clams
with a collection bag towed behind the workboat. In general, a
shellfish farmer only harvests a small portion of the field
annually in order to allow for growth in the unharvested areas.
Oyster dredging is generally done mechanically using dredges
comprising a steel frame with a serrated blade and a bag
attached to the frame to collect the harvest. Oysters reside in
areas with hard structures to attach to during the growth
process so the ground is made up of hard sediments. The teeth of
the blade penetrate the soft bottom directly removing oysters
from the substrate surface. These dredges have a considerable
amount of weight and must have a proper blade angle. The
efficiency of the mechanical dredge depends on the substrate
type and the size of the oysters. The catch rate can be improved
by passing over the same area multiple times. To collect
juvenile oysters, farmers employ hydraulic suction dredging. A
venturi dredge can be employed for the harvesting of oysters.
This dredge has chains designed to scare unwanted organisms from
the mouth of the dredge to limit the amount of bycatch. It is
also designed to remove a limited amount of sediment so as to
not permanently disturb the estuary.
Clam dredging was originally done using a mechanical “rocking
chair” dredge. Currently, farmers use hydraulic dredges to
liquefy the material caught in the mouth of the dredge. The
efficiency of these hydraulic dredges must be adapted based on
the sediments and is typically used on a muddy bottom. The
hydraulic dredge is designed with a wide blade and is towed
faster than a venturi dredge.
The effects of dredging on the environment vary based on the
design of the harvesting device and implementation. The
disturbance of habitats varies across a single harvested area.
These effects can be experimentally measured by conducting
experimental dredging and observing the response of the benthic
zone (the lowest area in a body of water). Experimental data
must be compared to preliminary data due to the existence of
site-specific factors. There is also the possibility of
comparing experimental data to a control site with similar
conditions. Researchers should also consider that the clam and
oyster environments are very high energy and tend to recover
quickly due to high levels of activity in the area.
The physical effects of shellfish dredging involve the effect on
the water quality due to the physical disruption of the benthic
substrate. Hydraulic dredges liquefy the substrate which causes
an increase in the amount of suspended sediments in the water
thereby increasing the water column turbidity. These suspended
sediments tend to extend 50 feet beyond the dredging zone.
The biological effects of shellfish tend to be species-specific
and is based on the biological characteristics and the physical
characteristics habitat. The movement of dredges or the
liquefication of sediments can cause benthic organisms to be
killed, removed, or crushed. The number of clams destroyed by
hydraulic dredges is directly related to the water pressure.
When the turbidity of the water column increases and suspended
particles increase, which can interfere with the respiratory and
feeding processes of some benthic organisms. In extreme cases
the turbidity can harm visual feeders and plankton. After the
initial harvest, there may also be a decrease in abundance of
organisms as well as the biodiversity of the habitat. This
effect is temporary as the species is replenished when farmers
incorporate hatcheries and shellfish cultures into their
activities. There is also the risk of damage or harm to by-catch
(unwanted fish and other marine life including different
species, incorrect sex, or juvenile).
The chemical effects include the alteration of the chemistry of
bottom sediments when the benthic organisms are disturbed.
Bivalves are organisms which filter the water in the ocean. As a
result of this property, removal or placement of these organisms
affect the chemical composition of the water. Dredging can
actually better the system metabolism, have an impact on the
water column processes, and facilitate trophic transfer.
Bivalves ingest and process suspended organisms redistributing
as biodeposition. This process can also influence the movement
of carbon, nitrogen, and phosphorus.
Increasing research in this area can be better for the
environment and increase the availability of shellfish in a
particular area. Shellfish harvesting is a major source of jobs
in a coastal community. Current cultivation methods can better
the potential of spawning, improve the utility of farming areas,
and allow more efficient movement of shellfish. These benefits
thereby increase profitability for shellfish farmers. Shellfish
aquaculture has the potential for meeting requirements of
environmental and social sustainability.
A large part of aquaculture is the conversion of workboats
to be equipped with the appropriate equipment for dredging and
harvesting. Aquaculture vessels require a significant amount of
research in order to design a vessel suitable to the harvested
environment and the type of harvesting that would ideal for that
species and habitat. Depending on the cultivation method,
farmers may choose to harvest using one of the following
Rock and Bag Culture
Oyster workboats are designed using aluminum vessels sized for
ease of accessing oyster parks with a shallow draft and a wide
deck for handling the oyster bags. Mussel barges also have a
shallow draft for easier access to the mussel parks with a wide
deck for large load capacity for mussels. Long-line culture
work-boats are designed with a flat bottom or shaped hull for
work in either mussel or oyster farms. Vessels over 12 meters
long are designed for longline farming and adapted according to
the species. There are combined mussel and oyster farming
workboats designed to be narrower than a barge with flat bottom
hull and a high load capacity from the double bottomed hull.
Aluminum wheel barges are designed with hydraulic wheels and can
be controlled using an autonomous hydraulic unit or on a
tractor. Some barges have hydraulic kickstands which provide an
increased level of stability.
Other vessels include a floating breeding pond. The floating
breeding pond is used to store shellfish to maintain the
condition of products prior to shipment. Launching trailers are
also incredibly important in farming and can be built according
to the size, load and other constraints. Flat trailers are used
for mussel boxes and oyster bags.
Sustainable Oyster Cultivation
In order to create a sustainable food source, farmers should
consider replenishing the population of oysters or any other
shellfish they may be harvesting. The different methods of
growing oysters include variations of on-bottom and off-bottom
growing methods. Bottom culturing is the most closely related to
the way that wild oysters are grown. This allows the oysters to
have access to nutrients they would have access to when growing
in the wild. The benefit of this method is the quality of shells
is stronger possibly due to the movement of water on the bottom.
However, this method falls short due to the amount of product
lost in the process due to suffocation or predators.
Off-bottom methods are used in order to overcome the
disadvantages of bottom culturing methods. One off-bottom method
is using a cage culture where the oysters are held and grown in
mesh bags inside of large cages to keep the oysters from
floating away or touching the bottom. Typically, they can be
used when the oysters are very young and not ready to planted on
the bottom. Rack-and-bag cultures is the use of mesh bags on a
steel rack where tides should be low enough to allow access to
the bags. Tray cultures can be used where space is limited since
the trays can be stacked. Floating culture is used to give the
oysters adequate exposure to waves in order to tumble them.
Suspended culture also takes advantage of the waves flipping and
tumbling the oysters while they are held in vertically suspended
mesh bags. These culture methods all rely on the varying
characteristics of their prospective habitats.
A shellfish hatchery is an essential part of the process for
growth of healthy juvenile shellfish for commercial use. One of
the most important elements of a successful hatchery is the
location. The ideal location is determined by the level of the
water supply. For example, oyster hatcheries require a
relatively high volume of clean sea water with salinities from
15 to 30 parts per thousand. Low salinity caused by incoming
waves of freshwater is harmful to oysters in the early stages.
Other aspects of the location to consider are the turbidity,
pollutants, boat traffic, and algae production.
The facilities for hatcheries can vary depending on the budget
and production need. Typically, a facility would have a separate
pump station to supply water for the facility from another
location. Dual water lines and pumps provide a system to
decrease the frequency of failed lines. The pumps are sized
based on the distance, height, and volume of water to be moved.
The water pumped into the hatchery can be first held in a tank
in order to decrease turbidity of the water supply or it can be
directly pumped into the hatchery. The water filtration and
treatment systems include a combination of sand filters,
cartridge filters, activated carbon, UV sterilization, and/or
The hatchery activities include water treatment, spawning,
larval care, feeding, and setting. Filtration can be done
mechanically or using UV treatment in order to remove unwanted
particles or organisms. Spawning is the first step in production
and can only happen with the water maintained at good condition.
For larval care, the tanks must be cleaned prior to placing
fertilized eggs. Larval care includes feeding algae, counting
the larvae, draining the tanks regularly, and restocking larvae
at their ideal density. It is crucial that the larvae are
transferred at the optimal level of maturation in order to
survive the conditions of the wild environment. This is just a
glimpse into the activities that go on at hatcheries. The
hatcheries play a vital role in breeding disease-resistant and
fast-growing shellfish to maintain the sustainability of the
shellfish harvesting industry.
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration (NOAA) is an
American agency which focuses on the conditions of the ocean and
other waters. A service of the NOAA is the National Marine
Fisheries Service (NMFS) who does research on commercial and
recreational fisheries and their habitat along with a goal of
protection and management of those fisheries.
Shellfish farming methods include a significant amount of
research and experimentation in order to increase and maintain
the sustainability of the practice. The industry will continue
to grow as the demand for shellfish farming increase. With the
benefit of an R&D tax credit, shellfish farming industries
can continue to innovate and strengthen the industry as a whole.