Procedures for Conducting Underwater Searches for 

Invasive Mussels (Dreissena sp.)

Open-File Report 2010–1308

Prepared in cooperation with the U.S. Fish and Wildlife Service

U.S. Department of the Interior

U.S. Geological Survey

Procedures for Conducting Underwater Searches for 

Invasive Mussels (Dreissena sp.)

By Noah Adams 

Prepared in cooperation with the U.S. Fish and Wildlife Service

Open-File Report 2010–1308

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its 

natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov 

or call 1-888-ASK-USGS.

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visit http://www.usgs.gov/pubprod

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Suggested citation:

Adams, Noah, 2010, Procedures for conducting underwater searches for invasive mussels (Dreissena sp.): U.S. 

Geological Survey Open-File Report 2010-1308, 44 p.

.

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endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Introduction.................................................................................................................................................................... 1

Background ................................................................................................................................................................... 2

How Mussels Move from Place to Place.................................................................................................................... 2

The Importance of Preventing the Spread of Invasive Mussels ................................................................................. 3

Dive Practices................................................................................................................................................................ 8

Advanced Preparation ............................................................................................................................................... 8

Dive Planning............................................................................................................................................................. 9

Communication with Divers.......................................................................................................................................11

The Buddy System....................................................................................................................................................12

Identifying Mussels Underwater....................................................................................................................................12

What Divers Are Searching For ................................................................................................................................12

What Divers Are Not Searching For..........................................................................................................................15

Defining the Search Area..............................................................................................................................................16

Methods for Searching..................................................................................................................................................17

General Considerations ............................................................................................................................................17

Arc Search Method ...................................................................................................................................................17

Circle Search Method ...............................................................................................................................................18

Jackstay Search Method...........................................................................................................................................20

Dock Search Method ................................................................................................................................................23

Collecting Information about the Search Area ..............................................................................................................24

Assessing the Probability of Detecting Mussels ...........................................................................................................24

Collecting Mussel Samples...........................................................................................................................................25

Decontamination of Equipment.....................................................................................................................................29

Acknowledgments ........................................................................................................................................................30

References Cited..........................................................................................................................................................30

Appendix 1 – Example of USGS Diving Reciprocity Form............................................................................................31

Appendix 2 – Sample Check Lists ................................................................................................................................33

Appendix 3 – Sample Data Sheets...............................................................................................................................38

Appendix 4 – USGS Decontamination Procedure. .......................................................................................................42

Appendix 5 – Lock-Out/Tag-Out Procedures................................................................................................................44

Figures

Figure 1. Photograph of two types of artificial settlement substrate used to monitor for adult mussels........................ 2

Figure 2. Diagram of the life cycle of dreissenid mussels ............................................................................................ 3

Figure 3. Photograph showing a zebra mussel and the byssal threads they use to attach to substrates..................... 3

Figure 4. Photograph showing zebra mussels attached to a native clam..................................................................... 4

Figure 5. Photograph showing zebra mussels attached to crayfish ............................................................................. 4

Figure 6. Photograph of a water intake in Lake Mead, Nevada, with dreissenid mussel colony .................................. 5

Figure 7. Photograph of a pipe that has been cut in half to show how the mussels can clog pipes ............................. 6

Figure 8. Photograph of mussel colony on hull of recreational boat from Lake Mead, Nevada.................................... 6

Figure 9. Photograph of mussels on out-drive of recreational boat.............................................................................. 7

Figure 10. Photograph showing mussels on substrate in near-shore environment...................................................... 7

Figure 11. Photograph showing mussels covering a beach in Great Lakes, Michigan................................................. 8

Figure 12. Photograph showing dive operations ........................................................................................................ 10

Figure 13. Photograph showing the range of sizes of adult mussels ......................................................................... 13
iv

Figure 14. Photograph of the two species of mussel commonly referred to as zebra mussels .................................. 13

Figure 15. Photograph showing variation in the striped pattern of the shells of zebra mussels ................................. 14

Figure 16. Photograph showing mussels attached to a rock...................................................................................... 14

Figure 17. Photograph showing differences between Asian clams and dreissenid mussels...................................... 15

Figure 18. Photograph showing a colony of dreissenid mussels................................................................................ 16

Figure 19. Drawing showing a standard arch sampling method................................................................................. 18

Figure 20. Drawing showing a standard circle search method................................................................................... 19

Figure 21. Photograph showing two pivot devices ..................................................................................................... 20

Figure 22. Drawing showing components of a jackstay search system. .................................................................... 21

Figure 23. Drawing showing how a jackstay system can be used to search the area next to a dock......................... 22

Figure 24. Drawing showing progression of moving a jackstay system during a search............................................ 22

Figure 25. Drawing showing one method for searching a dock for mussels .............................................................. 23

Figure 26. Photograph of thumbtacks and container used to pre-seed the search area............................................ 25

Figure 27. Photograph of a diver's slate..................................................................................................................... 26

Figure 28. Photograph showing preserved samples of mussels ................................................................................ 27

Figure 29. Examples of marker buoys that can be used to identify where samples were collected. .......................... 27

Figure 30. Example of a tally counter......................................................................................................................... 28

Figure 31. Example of underwater video equipment.................................................................................................. 29

Figure 32. Photograph of a typical SCUBA Buoyancy Control (BC) vest................................................................... 44

Tables

Table 1. A simple method for tender and diver to communicate.......................................................................... 11

Table 2. Differences between Asian clams and dreissenid mussels.................................................................... 15

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.31 meter (m)

mile (mi) 1.61 kilometer (km)

mile, nautical (nmi) 1.85 kilometer (km)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8.
1

Procedures for Conducting Underwater Searches 

for Invasive Mussels (Dreissena sp.)

By Noah Adams

Introduction

Zebra mussels (Dreissena polymorpha) were first detected in the Great Lakes in 

1988. They were likely transported as larvae or young adults inside the ballast tanks of 

large ocean-going ships originating from Europe. Since their introduction, they have 

spread throughout the Eastern, Midwestern, and Southern United States. In 2007, Quagga

mussels (Dreissena rostriformis bugensis) were found in the Western United States in 

Lake Mead, Nevada; part of the Lower Colorado River Basin. State and Federal 

managers are concerned that the mussels (hereafter referred to as dreissenid mussels or 

mussels) will continue to spread to the Columbia River Basin and have a major impact on 

the region’s ecosystem, water delivery infrastructure, hydroelectric projects, and the 

economy.

The transport and use of recreational watercraft throughout the Western United 

States could easily result in spreading mussels to the Columbia River Basin. The number 

of recreational watercraft using Lake Mead can range from 350 to 3,500 a day (Bryan 

Moore, National Park Service, oral commun., June 21, 2008). Because recreational 

watercrafts are readily moved around and mussels may survive for a period of time when 

they are out of the water, there is a high potential to spread mussels from Lake Mead to 

other waterways in the Western United States. Efforts are being made to prevent the 

spread of mussels; however, there is great concern that these efforts will not be 100 

percent successful.

When prevention efforts fail, early detection of mussels may provide an 

opportunity to implement rapid response management actions to minimize the impact.

Control and eradication efforts are more likely to be successful if they are implemented 

when the density of mussels is low and the area of infestation is small. Once the

population grows and becomes established, the mussels are extremely difficult, if not 

impossible, to control. Although chemicals may be used to kill the mussels, the chemicals 

that are currently available also can kill other aquatic life.

Early implementation of containment and eradication efforts requires getting 

reliable information to confirm the location of the infestation. One way to get this 

information is through the use of properly trained SCUBA divers. This document 

provides SCUBA divers with the necessary information to conduct underwater searchers 

for mussels. However, using SCUBA divers to search for mussels over a large 

geographic area is relatively expensive and inefficient. Early detection monitoring 

methods can be used to optimize the use of SCUBA divers.
2

Early detection monitoring can be accomplished by collecting water samples or 

deploying artificial settlement substrates (fig. 1). Water samples are used to look for freeswimming larval mussels (called veligers). Because the veligers cannot be identified with 

the naked eye, the water samples are sent to a laboratory where they are examined under 

a microscope and/or analyzed using molecular techniques to detect veligers. To detect the 

presences of adult mussels, artificial substrates are deployed and periodically retrieved to 

determine if mussels have settled on the substrate. If veligers or adults are identified, 

SCUBA divers can be deployed to confirm the presence of mussels.

Figure 1. Photograph of two types of artificial settlement substrate used to monitor for adult 

mussels. (Photograph courtesy of Bryan Moore, National Park Service, Lake Mead, 

Nevada.)

Background 

The majority of divers that will be called on to conduct searches for mussels will 

likely have limited information on what they will be looking for. The following section 

provides basic information about mussels and a brief discussion on the importance of 

preventing the spread of invasive mussels.

How Mussels Move from Place to Place

Dreissenid mussels have two basic life history stages. The stage most people are 

familiar with is the settled adult stage. The other stage is the larval stage known as the 

veliger. The diagram in figure 2 shows the life cycle of the mussels. Adults produce eggs 

and sperm that are released into the water where fertilization occurs. The fertilized eggs 

develop into veligers that are subsequently transported by water currents. As the veligers 

develop and grow larger, they become less buoyant and sink to the bottom. Once on the 

bottom, the juvenile mussels attach to substrates (i.e., rocks, wood, and metal) and 
3

continue to grow into adults. As adults, they reproduce by releasing eggs and sperm into 

the water and the cycle is repeated. Once the adults settle, they can move around by 

detaching the thread-like material (called byssal threads; fig. 3) that holds them in place 

and float with the water current, or they can use their muscular foot to pull themselves 

along.

Figure 2. Diagram of the life cycle of dreissenid mussels.

Figure 3. Photograph showing a zebra mussel and the byssal threads they use to attach to 

substrates. (Photograph courtesy of Great Lakes Sea Grant Network, Exotic Species 

Library, Ohio Sea Grant project.)

The Importance of Preventing the Spread of Invasive Mussels

Impact on Aquatic Ecosystems

Mussels can have a significant impact on the aquatic ecosystem. A healthy

ecological food web in lakes and reservoirs is highly dependent on the availability of 

microscopic organisms in the water. These organisms are the food for other larger 

organisms which in turn are food for even larger animals, like fish. When invasive 
4

mussels infest a lake, they filter the water and feed on the microscopic organisms, thereby

depleting the availability of food for other organisms. 

Impact on Native Mussels

In addition to consuming food that native animals depend on, mussels can attach 

themselves to other animals (figs. 4 and 5). This behavior, known as bio-fouling, can 

result in serious damage to native mussel and shellfish populations. When multiple

mussels attach to the body of another animal, it can cause the animal to exert more effort 

to accomplish the normal activities necessary to survive. This increased effort can make it 

difficult to search for and capture food, more difficult to maintain their body temperature, 

and make the native animals more susceptible to parasites and disease.

Figure 4. Photograph showing zebra mussels attached to a native clam. (Photograph courtesy 

of David Jude, Center for Great Lakes Aquatic Sciences.)

Figure 5. Photograph showing zebra mussels attached to crayfish. (Photograph courtesy of 

GLSGN Exotic Species Library, Ontario Ministry of Natural Resources.)
5

Impact to Human Health 

Because mussels are filter feeders, they can rapidly accumulate pollutants in their 

tissues. Some studies have shown that the level of toxins in mussels is 300,000 times 

greater than the concentrations of the toxins in the environment (Benson, 2010). These 

toxic chemicals can be passed to humans when they consume the meat of fish and 

waterfowl that feed on mussels.

Impact on Water-Related Structures

Mussels will attach to most hard surfaces and prefer locations where flowing 

water makes food and nutrients readily available. Water intake structures, like those used 

for power and municipal water treatment plants, provide an ideal environment for 

mussels (figs. 6 and 7). As the population grows, the mussels can clog the intakes and 

pipes and cause a significant reduction in pumping capabilities which could lead to a 

complete shutdown of the facility. The power industry has spent billions of dollars trying 

to eradicate mussel populations at hydroelectric facilities. The extensive infrastructure 

associated with hydropower and irrigated agriculture in the Columbia River Basin is 

particularly vulnerable to mussel infestations.

Figure 6. Photograph of a water intake in Lake Mead, Nevada, with dreissenid mussel colony.

(Photograph courtesy of Bryan Moore, National Park Service, Lake Mead, Nevada.)
6

Figure 7. Photograph of a pipe that has been cut in half to show how the mussels can clog 

pipes. (Photograph courtesy of Don Schloesser, Great Lakes Science Center.)

Impact on Recreational Activities

Mussels can negatively affect the performance of recreational watercraft. When

large numbers of mussels attach to the underside of a watercraft, the hull is no longer 

smooth. The increased roughness of the hull causes the engine to work harder to push the 

craft through the water (fig. 8). Attached mussels also can cause engines to overheat if 

they clog the cooling water inlets (fig. 9). 

Swimmers, SCUBA divers, and people wading along the shoreline can be injured 

if mussels are attached to rocks, docks, and/or other structures. Mussels have shells with 

extremely sharp edges that can seriously injure unprotected skin and can cause damage to 

SCUBA equipment (figs. 10 and 11). In addition, SCUBA equipment must be 

decontaminated after diving in water that is infested with mussels to prevent spreading 

them to other locations. Chemical and hot water decontamination methods can damage 

SCUBA equipment. Lastly, mussel colonies can quickly obscure and degrade shipwrecks 

and the underwater landscape, thereby detracting from the allure of popular dive 

locations.

Figure 8. Photograph of mussel colony on hull of recreational boat from Lake Mead, Nevada.

(Photograph courtesy of Bryan Moore, National Park Service, Lake Mead, Nevada.)
7

Figure 9. Photograph of mussels on out-drive of recreational boat. (Photograph courtesy of 

Bryan Moore, National Park Service, Lake Mead, Nevada.)

Figure 10. Photograph showing mussels on substrate in near-shore environment. (Photograph

courtesy of the San Benito County Water District, California.)
8

Figure 11. Photograph showing mussels covering a beach in Great Lakes, Michigan. 

(Photograph courtesy of Stephen Stewart, Michigan Sea Grant project.)

Dive Practices

Good dive practices are critical to conducting safe and efficient searches for 

mussels. A rudimentary overview of good diving practices is presented below and is 

followed by detailed information about how to search for and collect mussels. Some of 

the methods and procedures presented are beyond the skill level of a newly certified, 

novice diver. It is the responsibility of the person overseeing the diving operations to 

determine if the divers are certified through a nationally recognized SCUBA-training 

organization and are capable of safely performing the activities necessary for conducting 

the searches.

Advanced Preparation 

The request to conduct a search for mussels will likely be urgent and may only 

allow a day or two to prepare for activities at the dive site. Advanced training is 

recommended to prepare the divers to conduct the search in a timely, professional, and 

safe manner. A list of divers that complete advanced training should be maintained to 

simplify organizing and deploying a dive team when a request is made to conduct a 

search for mussels.

Divers asked to participate in a search will likely be members of various Federal, 

State, and local agencies. When divers from different agencies dive together, there are 

questions of liability that need to be addressed. One of the most important issues to 

consider is one of mutual competency. When a diver is put into a situation that is beyond 

their competency level, it can endanger all the divers on the mission. To prevent this from 

happening, the U.S. Geological Survey (USGS) requires divers from other agencies to 
9

meet minimum competency requirements before they can participate in multi-agency 

dive teams. Other Federal, State, and local agencies may have similar requirements.

Competency can be established in advance of diving operations by completing a 

reciprocity agreement. An example of a reciprocity agreement used by USGS is included 

in appendix 1. Establishing the reciprocity agreements between agencies is essential to 

allowing divers from different agencies to dive together and this information must be 

shared between agencies and reviewed and approved by the agencies Dive Safety 

Officers (DSO). Information that must be submitted for review includes dive logs, dive 

certification levels, number of dives in the last year, and results of last physical exam. In 

some cases, the DSO may request a diver to complete a “check-out competency dive” 

with the DSO or their designee. 

Completing reciprocity agreements takes time, and should be done in advance of 

any potential request that requires divers from multiple agencies to work together. If 

reciprocity agreements are not in place before a search is conducted, divers from different 

agencies should not work together on the same team or dive in the same search area. 

Coordination between agency dive teams operating in the same geographic area can 

occur to prevent unnecessary duplication of effort.

Having agency divers working with non-agency diver is possible; however, there 

are some additional considerations that should be addressed. Typically, divers that are 

members of agency dive teams have met minimum standards that are above those needed 

for basic SCUBA certification. Additionally, most agency divers are covered under 

Workers’ Compensation in the event of an injury. When non-agency divers are involved, 

it may not be clear who will cover medical expenses in the event of an accident. These 

issues must be addressed before non-agency divers are involved in searches for mussels 

with agency dive teams. 

Dive Planning

Any time multiple divers are part of a search, it is necessary to identify roles and 

responsibilities (fig. 12). A Dive Operations Coordinator, often referred to as a Dive 

Master or Dive Team Leader, should be identified. In addition, an onsite Safety Officer

should be identified. When personnel are limited, the Dive Operations Coordinator can 

also serve as the onsite Safety Officer. The roles and responsibilities of the Dive 

Operations Coordinator and onsite Safety Officer are shown below.
10

Figure 12. Photograph showing dive operations. Designated Dive Operations Coordinator 

shown on shore in colored hat, and/or a Safety Officer shown on shore helping divers with 

their gear. When multiple divers are used during a search, it is highly recommended that a 

Dive Operations Coordinator and/or an onsite Safety Officer assist the divers.

Dive Operations Coordinator

• Write a dive plan as required by the host agency.

• Coordinate pre-dive logistics to ensure that necessary equipment will be onsite 

(see appendix 2 for sample check lists).

• Establish reciprocity agreements and ensure documents are on file (see appendix 

1 for example forms).

• Coordinate with the requesting agency’s liaison to define the search area.

• Define search method and ensure that necessary equipment is onsite.

• Coordinate with divers to complete the search in a step-by-step fashion.

• Document environmental variables (see appendix 3 for sample data sheets).

• Document mussel samples collected by diver and transfer custody of samples to 

requesting agency (see appendix 3 for sample data sheets).

• Pre-seed the search area to assess effectiveness of the search (procedures for 

seeding a search area are discussed later in this document).

• Conduct pre-dive briefing including objectives, emergency procedures, and 

potential hazards.

• Conduct post-dive debriefing.

• Coordinate and document decontamination of dive equipment (see appendix 4 for 

decontamination protocol).
11

• Interact with the Press (Dive Operations Coordinator could be the primary person 

responsible for interacting with members of the Press. However, the agency 

responsible for the search may identify a person to serve as the public information 

officer. In this case, inquiries from members of the Press should be directed to 

that person.)

Onsite Safety Officer

• Assist divers with preparation of personal SCUBA equipment.

• Evaluate and monitor divers to determine if they are able to meet the requirements 

of the dive.

• Deploy and retrieve dive flags.

• Conduct pre- and post-dive checks with divers (see appendix 2 for sample check 

lists).

• Track entry and exit times of divers and monitor depths and tank pressures.

• Coordinate with surface support personnel to monitor the activities of multiple 

diver teams working in the search area.

• Interact with the public to keep the search area clear of unauthorized personnel.

This could include keeping the surrounding area clear of unauthorized boaters.

• Work with the Dive Operations Coordinator to rotate dive teams into the search 

area in a timely and efficient manner.

• Assist Dive Operations Coordinator with decontamination of equipment.

Communication with Divers

Some search methods require communication between the divers and surface 

support personnel. Several of the search methods involve using a long rope attached to 

the diver and running back to a surface support person. The surface support person 

responsible for working with the diver at the other end of the rope is often referred to as 

the tender. The simplest way for divers and tenders to communicate is by pulling on the 

rope, often referred to as the tender line. Many different ways to communicate using line 

signals have been developed and no single way is necessarily better than another. A good 

communication system between tender and diver need only be easy to remember and 

easy to interpret. Table 1 outlines a simple way for the tender and diver to communicate 

using a tender line.

Table 1. A simple method for tender and diver to communicate.

Number of pulls on 

the line

Tender pulled the 

line to tell/ask diver:

Diver pulled the line 

to tell tender:

1 pull Are you OK? I am OK

2 pulls You need to change direction I am changing direction

3 pulls You need to surface I found something, stand by

4 pulls or more Danger! Surface immediately! I am in trouble! Send help!
12

Wireless communication equipment is another way for the tender and diver to talk 

to one another. Verbal communication between divers and surface personnel can increase 

the safety of the divers and eliminates the need to communicate using a tender line. The 

downside to using wireless technology is the cost to purchase the equipment to outfit the 

tender and diver ($3,000 to $5,000 dollars) and the additional training that might be 

needed to use the equipment.

The Buddy System

Regardless of the search method used, all methods should be conducted using the 

buddy system. The buddy system requires two divers to conduct the search while 

maintaining visual contact with one another. Each diver watches for anything that may 

impact the safety of the other diver. This can include helping each other monitor tank 

pressure to prevent running out of air and preventing each other from getting tangled in 

fishing line, ropes, or other debris. Some divers claim that the buddy system can present 

more dangers than diving solo. They argue that capable divers are often forced into 

dangerous situations by less-capable divers. However, most circumstances that can 

potentially endanger the divers are unexpected and often impossible to predict. Although

an experienced diver can avoid more dangers than a less-capable diver, having a second 

diver during the search can provide assistance when something unexpected happens. In 

addition to implementing the buddy system, all search teams should have a backup diver 

(often referred to as a 90 percent diver) who has all their gear on and is ready to dive in a 

minutes’ notice in the event of an emergency.

Identifying Mussels Underwater

What Divers Are Searching For

Searching for mussels will be new to most divers. Although many divers have 

experience searching for items underwater, few will have experience looking for 

something as small as mussels (fig. 13). There are two species of mussel the diver will be 

looking for: zebra mussel (Dreissena polymorpha) and Quagga mussel (Dreissena 

rostriformis bugensis). They are collectively referred to as zebra mussels because of the 

characteristic zebra-like striped pattern on the shell (figs. 14 and 15). Because the striped 

pattern can be highly variable among individuals and difficult to identify in some cases, it 

should not be the only characteristic used to confirm the identity of the species.

When mussels are first introduced they often attach to the undersides of rocks 

(fig. 16), and in cracks and crevices of docks. As a result, divers must methodically 

examine all cracks and crevices to be confident they did a thorough job looking for 

mussels. To help increase the likelihood of finding mussels, divers should use a flashlight 

to examine dark crevices in rocks and other structures. If the search is being conducted in 

very turbid water and visibility is extremely low (that is, less than a couple of inches),

divers can use a plastic bag filled with clear water to improve their ability to see the 

mussels. To use this method, the water-filled bag is placed over the top of the item that 

the diver is trying to identify. The diver then shines their flashlight through the side of the 

bag while pressing their dive mask against the bag. This allows the diver to view the 

object through the clear water inside the bag. After mussels become established and their 
13

population density increases, they are very easy to find. If mussels are found, the diver 

will need to collect a sample. Procedures for collecting and preserving samples are 

discussed later in this document. 

Figure 13. Photograph showing the range of sizes of adult mussels. (Photograph courtesy of 

San Benito County Water District.)

Figure 14. Photograph of the two species of mussel commonly referred to as zebra mussels. 

The specimen in the top photograph is a zebra mussel and the specimen in the bottom of 

the photograph is a quagga mussel. (Photograph courtesy of U.S. Geological Survey.)
14

Figure 15. Photograph showing variation in the striped pattern of the shells of zebra mussels. 

(Photograph courtesy of U.S. Geological Survey.)

Figure 16. Photograph showing mussels attached to a rock. When mussels are first introduced 

in an area, it is common to find them tucked under the edge of rocks and in cracks and 

crevices of docks. (Photograph courtesy of Bryan Moore, Lake Mead National Park 

Service.)
15

What Divers Are Not Searching For

There are several native and non-native freshwater mussels and clams that could 

be present during a search for dreissenid mussels. One such species is the Asian clam

(Corbicula fluminea). Asian clams are native to Southeast Asia and were first reported on 

the West Coast of the United States in the 1930s. Since then, Asian clams have spread to 

more than 39 States including the Pacific Northwest. It is relatively easy to tell the 

difference between Asian clams and dreissenid mussels. Some of the key differences 

between these two species are outlined in table 2 and displayed in figure 17. Nedeauand 

(2009) provides a more complete description of the freshwater mussels and clams that are 

present in the Pacific Northwest. 

If a specimen is found during a search and the diver is not certain which species it 

is, the agency responsible for overseeing the search may request the diver to collect a 

sample so it can be identified by an expert. However, there are several species of mussels 

and clams that are protected under the Endangered Species Act (ESA) because their 

populations are threatened or endangered. Divers should not collect specimens unless the 

agency overseeing the search has the necessary authorization and permits.

Table 2. Differences between Asian clams and dreissenid mussels.

Figure 17. Photograph showing differences between Asian clams and dreissenid mussels. The 

two specimens in the left of the photograph are Asian clams. The specimen to the left of the 

penny is a dreissenid mussel. The horizontal line under the specimen in the left of the 

photograph is 1 inch in length. 

Asian clam Dreissenid Mussel

Generally larger than dreissenid mussels Generally smaller than Asian clams

Found on the bottom in the mud Found attached to structures

Light green/light brown colored shells Dark stripes on a light colored shell

Distinctive ridges on shells Smooth shells

Symmetrical shell Shell skewed to one side
16

Defining the Search Area

Areas that are accessible without using divers should be searched before divers 

are deployed. If the purpose of the search is simply to confirm the presence of mussels, 

the shoreline and above water portions of docks can be searched for discarded shells.

Rodents and birds that prey on mussels will use these areas to feed and often leave the 

shells behind. Similarly, a person in waders can easily search the shallow shoreline areas.

If visibility is poor, rocks can be removed and inspected for attached mussels. Searching 

in shallow water and on docks and beaches for discarded shells can be done before the 

dive team is called to the site. Similarly, artificial settlement substrate, as discussed 

earlier, can be used to monitor an area for the presences of adult mussels before divers 

are deployed to search the area. However, artificial substrate monitoring is not 100

percent effective and should not be the only method used to monitor for the presence of 

adult mussels.

The feeding habits of the mussels can be used to prioritize which areas should be 

searched first. Because mussels are filter feeders (fig. 18), they require a constant supply 

of nutrient rich water to survive and reproduce. Water intake pipes offer an ideal habitat 

for mussels and should be searched first. However, severe injury or death can occur if a 

diver becomes impinged on an intake pipe. Therefore, searching intake pipes requires 

coordination with the operator of the intake to establish proper lock-out/tag-out 

procedures (appendix 5). Procedures must be in place to prevent the accidental operation 

of the intake while divers are in the area.

Figure 18. Photograph showing a colony of dreissenid mussels. The mussels filter the water for 

food and nutrients. Note that their shells are open and their tube-like siphon is extended to 

pull water into their digestive system. (Photograph courtesy of Marc Blouin, U.S. Geological 

Survey.)
17

Methods for Searching

The size of the search area, complexity of the structures that need to be searched, 

and the environmental characteristics of the search area are factors that determine which 

search method to use. The following section discusses some general considerations 

regardless of the specific search method and then outlines a few basic search methods 

that can be use under a variety of conditions.

General Considerations

If the search area is large and multiple divers will be used simultaneously, a Dive 

Operations Coordinator and an onsite Safety Officer should be designated. It is 

potentially dangerous to have multiple dive teams in the water simultaneously without 

having adequate surface support personnel to record the entry and exits of multiple dive 

teams and to ensure all safety procedures are being followed.

Safety of the divers is the primary concern when conducting searches. Divers 

need to keep safety at the forefront of their thoughts at all times. The more that is asked 

of a diver, the harder this is to accomplish. To limit what is asked of the divers, and to 

increase the probability of finding mussels, divers should only be asked to identify and 

collect invasive mussels during a search. If divers are asked to identify other species, like 

fish and other native clams or mussels, the probability of finding invasive mussels will 

decrease. Studies show that the more items a person is asked to include in the search, the 

lower the efficacy is for any single item (Henke, 1998). If there is interest in identifying 

other species within the search area, they should be searched for on subsequent dives, not 

the initial search for invasive mussels.

Regardless of the methods used to search for mussels, divers can increase the 

probability of finding mussels by keeping in mind that mussels need a substrate to attach 

to and they prefer settling in areas that have a continuous flow of nutrient rich water. 

With this in mind, divers can spend less time searching sandy or muddy areas and more 

time searching rocks and other structures. 

Water current should always be considered when selecting and implementing a 

search method. When water velocity is less than 2 knots, a tender line can be used to 

guide the search and ensure that the divers are not inadvertently missing areas while they 

work against the current to maintain a search pattern. The search should progress into the 

current when possible so that sediment displaced by the divers is carried by the current 

into the area that has already been searched, not into the area that has yet to be searched.

Conducting searches in water currents greater than 2 knots is not recommended unless 

the divers have had specific training and experience.

Arc Search Method

This method is good for searching shorelines or the area next to docks and boat 

ramps. Using this method, the diver searches along consecutive arcs that increase in size 

until the area of interest has been covered. A rope attached to the diver is used by a tender 

on shore to help guide the diver during the search. After completing an arc, the tender 

signals the diver to change directions. The tender lets out additional line and the diver 

changes direction, takes up the slack in the line, and proceeds on the next arc. At the end 

of the arc, the sequence is repeated and additional arcs are searched. The amount of line 
18

let out by the tender will determine the spacing between the arcs. The spacing between 

the arcs is in turn determined by the clarity of the water. In relatively clear water with 

visibility greater than 3 ft, a diver can adequately search an area 5 ft wide when looking 

for something as small as mussels. If each of the two divers in the buddy team can 

adequately search a 5-ft wide area, the distance between the arcs can be 10 ft. When 

water visibility is less than 3 ft, each diver may only be able to adequately search a 2- to 

3- ft wide area so the distance between the arcs should only be 4–6 ft wide. Multiple 

diver/tender teams can be used concurrently to cover a large area. If this is the case, the 

arcs need to overlap between the teams to ensure a complete search of the area (fig. 19).

Advantages

Simple and easy to use.

Minimal amount of equipment needed.

Disadvantages

Submerged logs, large boulders, and other debris can tangle tender line.

Difficult to switch divers in the middle of the pattern.

Figure 19. Drawing showing a standard arch sampling method. The area shown in gray 

represents the area that is not searched if the arcs are not overlapped.

Circle Search Method

The circle search method is similar to the arch search method and can be used to 

search open water sites like the area under floating docks. In this method, no tender is 

necessary. Instead, the divers control the distance between consecutive circles by letting 

out line that is connected to an anchor. Before beginning the first circle, the diver places a 

small, highly visible marker on the bottom. The diver knows when they have completed 

the first circle when the marker is re-located. The diver then picks up the marker, lets out 

more line, sets the marker down, and proceeds to search along the next circle in the 

pattern. This process is repeated until the entire area of interest is searched (fig. 20).

Compass bearings can be used as an alternative to placing a marker on the bottom of the 

search area to determine when the circle is completed. To use this method, a compass 

bearing is taken at the beginning of the circle. When the same bearing is achieved at the 
19

end of the circle, the dive team moves to the next position to begin the next circle in the 

search pattern and a new compass bearing is taken. As was the case in the arc search 

method, the distance between circles is determined by the clarity of the water. It is best to 

have an anchor equipped with a mechanism that allows the line to move freely in a circle 

(fig. 21). If this is not part of the anchor design, the rope will get tangled around the 

anchor attachment point.

Advantages

Simple and easy to use.

Minimal amount of equipment needed, but anchor attachment point must move freely to 

prevent tangling.

No surface tender is needed to guide the diver.

Disadvantages

Submerged logs, large boulders, and other debris can tangle the line.

When multiple divers are used, this pattern must be overlapped to avoid missing areas.

Difficult to switch divers in the middle of the pattern.

Figure 20. Drawing showing a standard circle search method.
20

Figure 21. Photograph showing two pivot devices. One of these can be set on the bottom of a 

search area and used to guide the divers during the search when the circle or arc search 

methods are used. A rope is attached to the ring on the side of the pivot. The ring is welded 

to a sleeve that spins freely around the pivot, thereby preventing the rope from tangling 

during the search. A surface float and line can be attached to the ring at the top of the pivot 

and used as an accent/decent line. (Photograph courtesy of Carl Johansen, Assistant Team 

Leader, Sheriff’s Diver Rescue and Recovery Team, Stevenson, Washington.)

Jackstay Search Method

This method is very effective for searching areas for small objects, like mussels.

The word “jackstay” in nautical terms is used to describe a rail of wood or iron stretching

along a yard of a vessel, to which the sails are fastened. When used to describe a search 

method, it is used to describe a rope stretched between two anchors. Figures 22 and 23

show the components that make up the jackstay system and how this system is commonly 

deployed. The system consists of two ascent/decent lines that connect surface buoys with 

the bottom anchors. The bottom anchors are connected to one another with a line, called 

the search line, which the divers use as a reference point during the search.

To conduct a search using this method, divers start at one anchor and search along 

the search line until they reach the second anchor. The second anchor is then move 

laterally along the substrate. The distance the anchor is moved depends on the clarity of 

the water and the size of the object divers are searched for. When searching for mussels, 

the anchor might be moved laterally one arms-length. Once this anchor is moved, the 

divers change direction and search back to the first anchor. The first anchor is then 

moved laterally one arms-length in the same direction the second anchor was moved and 

the divers search along the search line back to the second anchor. The anchors are moved 

laterally in this step-wise fashion until the area is completely searched. Figure 24 shows

how moving the anchors in this manner creates a search pattern that overlaps itself 

several times. The overlapping search pattern makes this method very effective at finding 
21

small items. As effective as it is, many dive teams do not use it because it requires more 

equipment and time to set up and it can be confusing to implement unless divers have 

been trained in advance. However, the thoroughness of this search method may be worth 

the time it takes to train the divers and outfit them with the necessary equipment. 

Advantages

Underwater debris does not interfere with the search. The search line can lie over the top 

of these obstacles.

Thorough search pattern in open water environment.

Surface buoy can be used by surface support staff to track the progress of the search.

Easy to switch divers in the middle of the search.

Disadvantages

More difficult to use and may require advanced training.

More equipment needed.

Time consuming.

This method results in the divers swimming through the same area multiple times. As a 

result, sediment can be stirred up by the divers and obscure the search area.

Figure 22. Drawing showing components of a jackstay search system.
22

Figure 23. Drawing showing how a jackstay system can be used to search the area next to a 

dock.

Figure 24. Drawing showing progression of moving a jackstay system during a search. The 

gray area represents the area that is being searched during each evolution of the pattern.

Note the significant amount of overlap in the pattern using this system.
23

Dock Search Method

When searching docks for mussels, any water current should be used to the 

advantage of the diver to facilitate moving sediment away from the search area, not into 

areas that have not yet been searched. The series of images in figure 25 shows one 

approach to searching a dock. It is best to start at the deepest end of the dock and move to 

the shallow end because the divers will inevitably stir up sediment when they are 

searching the shallow area. To search large areas, multiple divers can be deployed 

simultaneously. In this case, individual teams should be briefed on the starting and 

stopping points to ensure areas are not excluded from the search.

Figure 25. Drawing showing one method for searching a dock for mussels. Note that the dock 

is searched in a manner that allows the flow of water to carry sediment displaced by the 

divers away from the search area.
24

Collecting Information about the Search Area

It is important to document information about the search environment. The 

requesting agency will need this information when reporting the results of the search and 

it can be useful for tracking the potential spread of invasive mussels. Below is a list of 

common information to collect during the search. Sample data sheets for recording this 

information are included in appendix 3.

Water temperature

Substrate characteristics

Air temperature

Weather conditions

Current

Visibility

Other species present during the search (i.e., fish, Asian clams, etc.)

Assessing the Probability of Detecting Mussels

Regardless of the search method used, it is helpful to have some measure of how 

successful the search was. A common way to estimate what the probability of detecting 

mussels was is to pre-seed the search area with items that are the same size, or smaller, 

than the item being searched for. When looking for mussels, one option is to seed the area 

with thumbtacks, which closely mimic a settled adult dreissenid mussel. The thumbtacks 

can be easily used to seed structures such as docks and can be placed under rocks or into 

submerged wood on the bottom. The number of thumbtacks used depends on the size of 

the search area. For example, a dock that is 50 ft long might be seeded with 10 

thumbtacks on the dock and 5–10 thumbtacks on the surrounding substrate in the vicinity 

of the dock. Divers conducting the search should know that seed items have been 

deployed, but the number of items and their locations should not be revealed.

After the search is completed, the number of thumbtacks found and their locations 

can be used to estimate the probability of detecting mussels in the search area. For 

example, if 8 of the 10 thumbtacks on the dock were found, but only 2 of the 10 

thumbtacks on the surrounding substrate were found, this would indicate that a relatively 

thorough search of the dock was accomplished (80 percent), but the surrounding area was 

not searched as well (20 percent). This information can be used to deploy additional 

divers in areas that were not adequately covered.

The thumbtacks should be numbered and their locations should be sketched on a 

site map (see appendix 3 for a data sheet that can be used to record the site map). This 

will allow any unfound thumbtacks to be recovered after the search and allow the divers

to record the identification number of the thumbtack on their slate along with a brief 

description of where it was collected. Figure 26 shows the numbered thumbtacks and a 

container that can be used to collect them. The container should have a wide mouth to 

make it easy for the divers to open and close under water. The containers should be filled 

with water from the search area before the divers take them underwater. This will prevent 

the containers from floating towards the surface during the search. It is very important 

that the water used to fill the container is dumped back into the search area if the 

container was not used to collect samples. The empty container must be included in the 
25

equipment that is decontaminated after the dive. If the search area is infested with 

mussels, the water that is used to fill the containers can have microscopic veligers in it. If 

this water is transported to a different area, it can spread the infestation of mussels.

Figure 26. Photograph of thumbtacks and container used to pre-seed the search area. Tacks 

can be used to estimate how efficient the search efforts were.

Seeding the site can provide useful information about how well the area was 

searched. However, it requires additional time and resources to implement and may not 

be feasible under all circumstances.

Collecting Mussel Samples

If divers find mussels, they should collect samples for verification. In anticipation 

of collecting samples, divers should be equipped with a mesh bag with several collection 

containers. Figure 27 shows a photograph of a small, wide-mouth container that is easy 

for divers to use. The containers need to be numbered before the dive. If a mussel is 

found, the diver can place it in one of the numbered containers and record information 

about where the sample was taken. Figure 27 shows an example of a slate that can be

used to record the information. The slate has several writing surfaces in a compact design 

that is secured to the diver’s wrist. 
26

Figure 27. Photograph of a diver's slate. These can be used to record information during a 

search for mussels.

Plastic freezer bags with a zipper locking mechanism can be used instead of 

plastic sample bottles. Like the sample bottles, the plastic bags can be numbered prior to 

diving. The advantage of using plastic bags is that they take up very little space and are 

not buoyant so they do not need to be filled with water before diving. The disadvantage 

of using plastic bags is that some divers find it difficult to manipulate the zipper 

mechanism while wearing gloves. Furthermore, bags can burst when they are used to 

transport samples of water and mussels from the dive site to a laboratory.

Regardless of the type of sample container used, the diver needs to record

minimum information about where the sample was collected. The diver should use an 

underwater slate to record a brief description of the location of where the sample was 

collected along with water depth and temperature. After the diver is out of the water, 

these notes are transferred to a label that is attached to the sample container (see appendix 

3 for example of labels). After the container is labeled, the sample needs to be preserved 

for transportation to a laboratory for identification. To preserve the sample, the water is 

removed and replaced with a 70 percent isopropyl alcohol solution. Most of the over-thecounter alcohol that is available at drug stores is 70 percent isopropyl alcohol. When 

using alcohol to preserve samples, it is important to remember that it is flammable and 

the necessary precautions need to be implemented to prevent accidental fires. In addition, 

alcohol that is inadvertently spilled on the label will dissolve the ink if a standard pen is 

used. Permanent ink or pencil should be used to label all samples.

Another way to collect samples is to remove small rocks, sticks, or other substrate 

that the mussels are attached to. Figure 28 shows some examples of items that were 

removed during a survey in Lake Mead, Nevada. If this method is used, the items should 

be placed in a container with 70 percent isopropyl alcohol to preserve the mussels. If this 

is not possible, the sample can be allowed to air dry for an hour or two, and then heavily 
27

coated with a clear polyurethane or varnish. The items shown in figure 28 were coated 

with Minwax® water-based polyacrylic protective finish. The coating will prevent the 

mussels from falling off of the sample. If the mussels are allowed to sit out of the water 

for longer than an hour, they will die and fall off.

Figure 28. Photograph showing preserved samples of mussels. These items were removed 

during a mussel survey and then coated with Minwax® water-based polyacrylic protective 

finish.

When samples are taken in the open water environment, it is best to place a 

marker buoy at the sample location to provide a reference point. There are many suitable 

surface marker buoys available and the one that works best is the one that the divers are 

most familiar with. Figure 29 shows some examples of marker buoys.

Figure 29. Examples of marker buoys that can be used to identify where samples were 

collected.

Depending on the level of infestation, it might be necessary to count the number 

of mussels seen by each diver. If this is the case, one simple way to accomplish this is to 

outfit the divers with tally counters. Several models exist that are inexpensive, made of 

plastic, and can be used underwater (fig. 30). The divers should be instructed to collect 

several mussel samples for verification and count all mussels seen during the survey 

using the tally counter. The need to count the number of mussels seen by the diver will be 
28

determined by the agency overseeing the search. If the objective of the search is to simply 

verify that mussels are present in the area, it is not necessary to count them. However, 

divers may be asked to count the number of mussels seen during the search so the agency 

overseeing the mission can have a general idea of the number of mussels in the area.

Figure 30. Example of a tally counter. Divers can use these to record the number of mussels 

seen during a search.

In addition to counting mussels and obtaining a few adult mussels for verification, 

documenting other observations about the mussel population can be very useful to 

managers trying to develop a strategy to contain the infestation. Divers should note the 

variation in the size of the mussels, if the mussels appear in clumps or as solitary 

individuals, the presence of mussels that appear dead, and the presence of empty mussel 

shells in the search area. One way to determine if a mussel is dead is to touch the mussel

while the shell is open. If the mussel does not close its shells after being touched, it is 

likely dead.

Underwater photography can be a useful way to document the presence of 

mussels and gather useful information about the characteristics of the population (fig.

31). However, underwater photography should not be the only way to verify the presence 

of mussels and samples should still be collected during the initial search. Although

capturing quality photographs of underwater specimens can be difficult, technological 

advances in video equipment has made it easier. Most cameras are capable of capturing 

images in relatively low visibility conditions. If divers use underwater photography

equipment, they should place a ruler or other common object in the field of view to serve 

as a reference and reflect the scale of the objects that are being photographed.
29

Figure 31. Example of underwater video equipment. Photograph can be used to document the 

presence of mussels during a search.

Regardless of the sampling method, divers need to know that transferring invasive 

species without a permit is a crime in many States and can result in penalties and fines.

Divers need to work with their State and Federal agencies to obtain authorization to keep 

a mussel as a souvenir.

Decontamination of Equipment

It is very important to decontaminate all equipment that was used during a search 

for mussels. Although adult mussels are relatively easy to see on dive equipment, the 

larval stage (called veligers) is only visible using a microscope. The larva can live 

anywhere water can pool. The inside of the diver’s buoyancy compensator (BC) is a good 

example (fig. 32). Appendix 4 outlines the methods used by USGS divers to 

decontaminate equipment. Another source of information for decontamination of 

equipment and boats can be found at the California Department of Fish and Game

website (www.dfg.ca.gov/invasives/quaggamussel). Decontamination of equipment 

should be overseen by someone familiar with the process.

Figure 32. Photograph of a typical SCUBA Buoyancy Control (BC) vest. Extra diligence needs 

to be applied to properly decontaminate the internal bladder of the BC to prevent the spread 

of mussels.
30

Acknowledgments

The author would like to thank the following people for their assistance during the 

preparation of this document and their review and comments on early drafts: Bryan 

Moore, National Park Service, Lake Mead, Nevada; Marc Blouin, USGS, National Dive 

Safety Program Manager; Arne Gonser, Sergeant, Skamania County Sheriff’s Office;

Scott Smith, USGS Ecology Section Chief; Paul Heimowitz, USFWS Aquatic Invasive 

Species and Research Coordinator; Dennis Otsuka, Metropolitan Water District of 

Southern California; Dan Marelli, Scientific Diving International; Dave Lamb, Lake 

Ecologist, Coeur d’Alene Tribe. The author also is grateful to Matthew Sholtis, Lynn 

Casal, Nick Swyers, Rachel Reagan, Dena Gadomski, and Dennis Rondorf at the 

Columbia River Research Laboratory for their assistance in providing material for this 

document and editorial review. 

References Cited

Benson, A.J., Richerson, M.M., and Maynard, E., 2010, Dreissena rostriformis bugensis.

U.S. Geological Survey database, accessed November 9, 2010, at

http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=95.

California Department of Fish and Game, no date, Invasive Speices Program: California 

Department of Fish and Game database, accessed October 18, 2010, at 

http://www.dfg.ca.gov/invasives/quaggamussel/

Henke, S.E., 1998, The effect of multiple search items and item abundance on efficiency

of human searches: Journal of Herpetology, v. 32, p. 112-115.

Nedeau, E.J., Smith, A.K., Stone, Jen, and Jepsen, Sarina, 2009, Freshwater mussels of 

the Pacific Northwest, Second Edition: The Xerces Society for Invertebrate 

Conservation, 52 p., accessed October 15, 2010, at http://www.xerces.org/wpcontent/uploads/2009/06/pnw_mussel_guide_2nd_edition.pdf.

U.S. Geological Survey, 2009, Nonindiginous Aquatic Species Program (NAS): U.S. 

Geological Survey database, accessed October 18, 2010, at 

http://nas.er.usgs.gov/taxgroup/mollusks/zebramussel/.
31

Appendix 1 – Example of USGS Diving Reciprocity Form.

REQUEST FOR DIVING RECIPROCITY FORM

VERIFICATION OF DIVER TRAINING AND EXPERIENCE

A scientific diver, who is currently authorized to dive for the USGS and meets the 

requirements for scientific diving of another host organization, may apply to the USGS 

Diving Safety Board (DSB) or the Diving Safety Officer (DSO) to be considered for 

diving reciprocity as a visiting diver. Upon review of the diver’s credentials, records, and 

justification, the DSB/DSO may grant approval for diving reciprocity with the host 

organization. The visiting bureau diver will meet or exceed all requirements and comply 

with the diving regulations of the host organization’s Diving Safety Manual unless 

previously arranged by both of the organization’s Diving Safety (Control) Boards.

The host organization has the right to approve or deny this request and may 

require, at a minimum, a checkout dive with the Diving Safety Officer (DSO) or designee 

of the host organization. If the request is denied, the host organization should notify the 

DSO of the visiting diver the reason for the denial. The DSO for the visiting scientific 

diver has confirmed the following information:

(Date – mm/dd/yyyy)

_______ Written scientific diving examination

_______ Last diving medical examination. Expiration date: _______

_______ Most recent checkout dive

_______ SCUBA regulator/equipment service/test

_______ CPR training (Agency): ______. Expiration date: ______

_______Oxygen administration (Agency): ______. Expiration date: ______

_______First aid for diving (Agency): ______. Expiration date: ______

_______Date of last Dive

Number of dives completed within previous 12 months? __

Depth certification: ____

Are there any restrictions? __Yes __ No

If yes, explain: 
32

Please check any pertinent specialty certifications:

__Dry suit __Divemaster __Altitude

__Nitrox __Instructor __Ice/Polar

__Mixed gas __EMT __Cave

__Closed circuit __Dive Accident Management __Night

__Saturation __Chamber operator __Other (Specify)

__Decompression __Lifesaving

Name of Diver: _____________ Emergency Information: (To notify in an emergency)

Name: __________ Relationship: ____________________

Telephone: (work) ___________ (home) ____________

Address: _______________________________________________________________

This is to verify that the above individual, ____________ (insert diver’s name) is currently 

authorized to dive for the U.S. Geological Survey and meets the requirements set fort for diving 

with the host organization: ________.

Diving Safety Officer: ________________________________ _________________

(Signature) (Date)

 ________________________________ _________________

(Print) (Telephone)

________________________________ _________________

(FAX) (E-mail)
33

Appendix 2 – Sample Check Lists

The following sheets are included in this document as examples that can be used during 

searches for mussels.
34

PRE-DIVE EQUIPMENT 

CHECKLIST

Date __________ Time ________ 

Location____________________________________________________________ 

Name and contact information of 

 person overseeing dive operations ____________________________________

What each diver should bring:

o Buoyancy Compensator (BC)

o Regulators

o Weight Belt/Integrated Weights

o Dive Harness

o Mask

o Fins

o Snorkel

o Exposure Suit (Wet or Dry Suit)

o Tanks

o Hood and Gloves

o Flashlights (at least two)

o Extra Batteries for Flashlights

o Mesh Collection Bag

o Cutting Devices (Scissors and Knife)

o Underwater Writing Slate

o Food and Water

o Life Jacket
35

Additional equipment that the dive coordinator/dive master needs to bring:

o Diver emergency oxygen kit, first aid kit, and backboard.

o Dive flags

o Means of communication (that is, radio, cellular telephone, satellite telephone)

o Camera

o Data sheets

o Sample containers and 70 percent isopropyl alcohol for preserving samples

o Items to pre-seed the search area 

o Equipment for conducting search patterns

o Ropes

o Floats

o Anchors

o Decontamination equipment

o Lockout/tag out supplies (see appendix 5)

o If boats will be used in the search, the Dive Operations Coordinator needs to ensure that the boat 

operators are aware of the special consideration when divers are in the water, ensure proper 

communications between the dive teams and boat operators, and ensure the boats are properly 

decontaminated after the search is complete.
36

PRE-DIVE CHECKLIST

Date __________ Time ________ 

Location____________________________________________________________ 

Name and contact information of 

 person conducting pre-dive check _____________________________________

o Define dive mission, objectives, and goals 

o Ensure that all divers are qualified by having the proper training and experience to safely 

complete the required tasks

o Explain dive site boundaries

o Review dive conditions: Wind, currents, waves, and visibility

o Specific hazards of the dive site: Marine life (animals and plants), caves, currents, 

wrecks, other vessels.

o Evaluate and discuss potential for entrapment, entanglement, or other physical or 

mechanical hazards

o Evaluate and discuss potential for bottom obstructions or dangerous bottom conditions

o Evaluate and discuss potential for strong currents, low visibility, thermoclines, and 

surges

o Evaluate and discuss potential for contamination or exposure to pollution (such as, 

petroleum products or biological and chemical hazards)

o Review procedures for water entry and exit, and location of descent/ascent and float lines

o Dive buddies paired up and review “Buddy Check”

o Buoyancy – BC is functional and partially inflated for entry

o Weights – Weight type (integrated or belt) and release is free for access

o Releases – All clips, Velcro, buckles, and tank straps are secured

o Air – Air is on and flow is tested. Note volume of air in tank 

o Final assessment. Is your buddy physically and mentally ready for the tasks?

o Do you know your buddy’s gear? Backup regulator, weight release method, and cutting 

devices

o Maximum depth and bottom time, minimal “return to surface” tanks pressure

o Procedures if separated from dive group or surfaced and caught in a current

o Review hand signals

o Diver emergency and recall procedures

o Oxygen kit, first aid kit, and backboard on site

o Ensure appropriate dive flags are prominently displayed

o Means of communication (radio, cellular telephone, landline telephone, Satellite phone)
37

POST-DIVE CHECKLIST

Date __________ Time ________ 

Location____________________________________________________________ 

Name and contact information of 

 person conducting post-dive check _____________________________________

o All divers safely out of water

o Dive team buddies stay together for a minimum of 1 hour to monitor post-dive condition

o Strike dive flags

o Recover and stow all support equipment

o Transfer samples to agency representative

o Ensure that all dive equipment is thoroughly cleaned and properly stowed.

o Conduct a dive debrief with all divers

o Identify problems experienced during the dive

o Lessons learned for future missions

o Data and specimens documented and turned over to appropriate person

o Monitor divers for signs and symptoms of pressure-related illnesses or injuries

o Remind divers to seek medical attention if they experience dive related injury symptoms after 

leaving the dive site
38

Appendix 3 – Sample Data Sheets

The following information contains examples of data sheets that can aid in documenting searches for 

mussels.
39

Date________ Time______

Your Name_________________ Location________________

Dive #_________

Note

Sketch of Search area 

Site Map Data sheet
40

Documenting Environmental Data of Dive Site

Location________________________________________________________________

Date_________________________ Time_______________________

Collected by (name and contact information) 

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Water temperature (specify oC or oF ) _______________________________________

Substrate characteristics

(bedrock – hard) (bedrock – shale) (boulder - immovable, generally over 1 meter in diameter) 

(cobble - movable), (silt/mud)

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Air temperature _________________________________________________________

Weather conditions

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Current

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Visibility

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Other notes (species present fish etc). 

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________
41

Label for sample containers

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________

Mussel Sample

Location:_____________________________________________

Date:_____________ Collected By:_______________________

Depth Range:__________________________________________

Substrate:_____________________________________________

Water Temperature:_____________________________________

Preservative:___________________________________________

Comments:____________________________________________
42

Appendix 4 – USGS Decontamination Procedure.

STANDARD OPERATING PROCEDURES

U. S. Geological Survey

Great Lakes Science Center

1451 Green Road, Ann Arbor, MI 48105

Revised September 19, 2002

A procedure for the decontamination of SCUBA diving equipment and underwater gear after 

diving in waters containing zebra mussels (Dreissena polymorpha) and other exotic species of 

Dreissenid.

This Standard Operating Procedure (SOP) is intended to provide a step-by-step procedure for the 

decontamination of SCUBA diving equipment after its use in waters infested with zebra mussels.

Current information regarding geographic areas of zebra mussel infestations is available from the U.S. 

Geological Survey (2009) Non-indigenous Aquatic Species (NAS) website

(http://nas.er.usgs.gov/taxgroup/mollusks/zebramussel/).

Overview:

In order to avoid the spread of zebra mussels to non-infested waters via SCUBA diving equipment and 

underwater sampling gear, a protocol must be designed and implemented.

Responsibility:

All USGS procedures for the decontamination of SCUBA equipment will strictly adhere to and follow 

all USGS requirements. All USGS authorized divers will be responsible their dive gear and underwater 

equipment.

Wetsuits and Drysuits

Dive Gear and Equipment:

Buoyancy Compensators

Tanks (including boots and protective mesh)

Regulators and gauges

Mask, Fins, Snorkel

Cameras and video equipment

Sampling devices
43

Procedures:

(1) All dive gear and equipment used in zebra mussel infested waters should be inspected for the 

presence of adult zebra mussels. If found, adult zebra mussels should be removed, dried (or killed using 

another effective method) and disposed of in a manner that prevents introduction into local waters. All 

dive gear must be washed thoroughly by soaking in warm, soapy water and rinsing in warm, chlorinated 

tap water. Water temperatures greater than 110 °F have been found to be effective for killing larval 

zebra mussels, however, water temperatures greater than 120°F should not be used as it may damage 

certain temperature–sensitive dive gear and void some manufacturer’s warranties. Acidic or basic 

solutions (including vinegar or bleach) also should not be used as they may compromise the integrity of 

thermoplastic materials. Buoyancy compensators must be flushed internally with warm tap water and 

dried completely using standard procedures as recommended by the manufacturer. Commercial dive 

gear cleaners, such as wetsuit shampoos, may be used in the decontamination process. Drains in 

washing facilities must be attached to a source for wastewater treatment (municipal sewer) and must not 

discharge into external waters.

(2) All dive gear and equipment must be completely dry for at least 24 hours before use in waters where 

there is no zebra mussel infestation. Note: wetsuit seams should be closely inspected to insure that the 

material is completely dry.

Contact information:

Marc A. Blouin

Fishery Research Biologist / Diving Safety Officer

mblouin@usgs.gov

U.S. Geological Survey

Great Lakes Science Center

1451 Green Road, Ann Arbor, MI 48105

734-994-8780 fax

734-214-7248 work
44

Appendix 5 – Lock-Out/Tag-Out Procedures

This is a brief overview of basic lock-out/tag-out procedure. The purpose of this overview is to 

familiarize the members of the search team with the basic steps for preventing the accidental operation 

of equipment that could injure SCUBA divers during an underwater search.

When SCUBA diving near dams, power plants, pumping plants, or diversion structures with 

mechanical or electrical features that could pose a hazard to divers, a technical representative 

responsible for the operation of the equipment must be present or in direct communication to assist the 

divers.

During the pre-dive briefing, the dive operations coordinator will inform all divers about the 

potential hazards and the procedures that will be implemented to prevent the accidental operation of 

equipment in the dive area.

The technical representative will identify the electrical and/or physical control points for 

energizing the feature that is to be tagged out. For example, this could be an electrical breaker for 

controlling a pump that draws water through an intake pipe and/or a valve that controls the flow of 

water through a pipe or other water conveyance structure.

A physical lock and appropriate warning tag will be fastened to the control point. Basic lockout/tag-out kits are available from numerous vendors that are specifically designed for this purpose (fig.

3-1). After the lock and tag have been secured, both the technical representative and the dive operations 

coordinator will sign the tag indicating that the proper procedures have been conducted and it is safe for 

divers to enter the area. 

After dive operations are complete, the technical representative and the dive operations 

coordinator must mutually agree that it is safe to remove the lock and tag, thereby releasing the control 

point for normal operations. The dive operations coordinator and the technical representative must both 

be present to remove the lock and tag. No other person or persons have the authority to release the 

control point for normal operations.

Figure 3-1. Examples of tags (left) and lock-out/tag-out kits (right) that are used to prevent the operation of 

hazardous equipment while divers are in the water.
Publishing support provided by the U.S. Geological Survey

Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the 

Director, Western Fisheries Research Center

U.S. Geological Survey, 6505 NE 65th Street

Seattle, Washington 98115

http://wfrc.usgs.gov/
Adams—Procedures for Conducting Underwater Searches for Invasive Mussels (Dreissena sp.)—Open-File Report 2010–1308