procedures for scientific diving. sources american academy of underwater sciences, proc. of...

Procedures ForScientific Diving

Sources

• American Academy of Underwater Sciences, Proc. of Scientific Diving Symposia, aaus.org.

• Haddock, S.H.D., Heine J.N. 2005. Scientific Blue-Water Diving. California Sea Grant Publ. No. T-057.

• Heine, J.N. 1999. Scientific Diving Techniques. Best Publishing Company, Flagstaff, AZ.

• Joiner, J.T. (ed.). 2001. NOAA Diving Manual - Diving for Science and Technology, Fourth Edition. Best Publishing Company, Flagstaff, AZ.

Objectives

• Upon completion of this module, the participant will be able to:

• Describe the general history of scientific diving• List ten environments in which scientific diving has been conducted • list the types and recommended design of diving slates• Describe three methods of locating a dive site• Describe methods to mark a site, both above and below the water• Describe ways for a diver to collect sediments• Describe ways for a diver to measure temperature, water motion,

light and sound• Discuss mapping for archaeology studies, including horizontal and

vertical offsets• Discuss the trilateration method of mapping• State how sediment is removed from archaeological sites

Objectives (cont)

• Upon completion of this module, the participant will be able to:– List the activities for biological research dives– List the major areas of biological research– Discuss quadrats and transect sampling– Describe the advantages of photography and

videography in biological sampling– Describe the tools and methods used for assessing

aquatic organisms

History of Scientific Diving• Modern scientific diving began in the US in 1949 at the

Scripps Institution of Oceanography• Scuba diving in support of science authorized at the

University of California in 1953• The first research published using scuba:

• Aleem, Anwar Abdel. 1956. Quantitative underwater study of benthic communities inhabiting kelp beds off California. Science 123:183.

• NOAA established the first National Undersea Laboratory at the West Indies lab

• The American Academy of Underwater Sciences was formed in 1977– Currently has more than 100 organizational members

Scientific diving has been conducted in a wide variety of

environments…• Coral reefs• Mangroves• Kelp forests• Rocky shores• Soft bottom habitats• Polar environments• Open ocean/blue

water environments

• Offshore platforms• Estuaries• Hot springs• Hypersaline

environments• Caves• Lakes• Rivers

…and been used in many different sciences

• Chemical• Geological• Biological

• Paleontological• Archaeological

Chemistry• Diving has been used to

support research such as determining the chemical ecology of invertebrates and collecting marine organisms for the extraction of chemical compounds

Divers may obtain core

samplesof rock and sediment or dig holes to

examine depositional

history

Scuba is very useful for visual identification of sediments – and for collecting representative and relatively undisturbed samples

Geology

Divers may perform a wide variety of tasks such as measuring various community structural parameters like fish counts, algal counts, macroinvertebrate counts, percent cover of benthic algae and invertebrates, etc…, or measuring physiological responses of organisms in natural environments

Biology

Divers recover fossils from the underwater realm…

Dinosaur fossils from the waters off the Isle of Wight

Paleontology

Diving is integral to the study of underwater archaeology

Excavation of 4th – 6th century AD

harbor site in Malta

Serçe Liman1 excavation - 11th Century Byzantine Shipwreck - Diver hovers above grid used to mark locations of artifacts

Serçe Limanl excavation – Diver raises fragile hull timber using a lifting box

Archaeology

Scientific Diving - General

• The diversity of disciplines involved in scientific diving, and the varied environments where this diving is performed, has necessitated the development of a wide variety of techniques for observing and sampling underwater

Recording Information - Slates

• Almost every scientific project requires that data be recorded underwater; slates are a simple tool for doing this

• The best material for a slate is a white polycarbonate or acrylic– This material is strong, waterproof, and negatively

buoyant– It will not corrode when exposed to salt water, and is

available in sheets, which can be easily cut to the desired size

Diver using slate to record organisms found in artificial reef


• Slate size and form may vary - large or small, single or multiple sheets, flat or curved to fit around the wrist


• For archaeology, it is recommended that the minimum dimensions of a slate should measure approximately 10 in x 12 in x ¼ in, to 12 in x 14 in x ¼ in

• Much smaller and the diver has inadequate space for detailed recording

• Larger slates are useful, but can be difficult to handle under certain conditions


• A wooden or mechanical pencil is attached to the slate by a string, cord, or rubber tubing

• Bic brand mechanical pencils have been found to work the best due to the hardness of the lead, but the mechanics of the pencil are not always reliable when repeatedly exposed to water

• Regardless of the pencil chosen, always carry at least one spare

• A pencil may be used to write directly on the plastic of a slate, or to write on material attached to a slate


• Underwater paper is available for use on slates (e.g., Xerox “Never-Tear”)

• Can be used in copiers and printers to duplicate data sheets

• Sheets can be secured to slate with binder clips, surgical tubing, or a wing-nut bar

Locating, Relocating, and Marking Sites

• Locating, relocating, and adequately marking a study site are critical

• Many methods may be employed– Compass bearings

• Use compass bearings towards readily identifiable objects on land

• For greater accuracy, use shore lineups, where pairs of objects that are in a straight line can be used to triangulate a position

– Disadvantage – shore markers may not always be visible


– Global Positioning Units (GPS)• Relatively inexpensive, portable, and

accurate• Can store multiple points (waypoints), give

the heading, distance, time to each waypoint from your present position and store multiple routes with many legs on each route

– Sonar (depth finders) • Tell water depth, or distance underwater to

structures


• Buoys– Perhaps the best and easiest method for relocating a site

from the surface– May be inexpensively made from plastic bottles– Torpedo shaped buoys minimize chances of

entanglement with kelp– May be connected to the bottom with chain, cable, or

lines– May be tied to structure on bottom – length of garden

hose may help to avoid chafing – or weighted on bottom– In sandy or soft-bottom areas, sand, earth, or fence

anchors can be screwed into the bottom – Disadvantages – take time to install correctly, and are

subject to loss from storms, theft, entanglement in boat propellers, or mauling by marine animals

• May also require a permit from a management agency


• Underwater marking – may be necessary once the surface location of a site is established

• May also require a permit from a management agency– Variety of items may be driven into the substrate

• Nails• Tent stakes• Rebar• Railroad spikes• Pitons

– Marking tags may be placed on these• Cable ties• Vinyl roll flagging tape• Pieces of PVC


• To properly mark an area, it may be necessary to drill holes – Star Drill – hammered in by hand

• The drill is held with pliers and is rotated slightly with each blow of the hammer

• Time consuming and tiring; not practical if large number of holes must be drilled


– Pneumatic drill or hammer – good for making numerous holes, especially in hard rock - or for more permanent fastening

• May be fitted to work off a scuba tank• Disadvantages:

– May use a great deal of air– Very loud– Require considerable maintenance after use

– Hydraulic systems • Advantages - Quieter and more efficient than

pneumatic tools• Disadvantages – More expensive – requires a link

with control station on surface


• Cement and epoxy may also be used to adhere items to the substrate– Generally work best on a clean substrate– May be packed into cracks, crevasses, or drilled holes– Marine putties or underwater patching compounds have been

used– A mixture of four parts Type II Portland cement and one part

molding plaster combined with seawater may be carried underwater in plastic bags

• This mixture can be packed into holes before placement of eyebolts or stakes

Geological Measurements and

Collections• Collection of sediments - Coring devices – useful for

stratigraphy determination or grain size analysis– A wide variety of corers are available:– Coffee can with plastic lid

• Remove bottom and replace with fine mesh screen• Insert corer into substrate and push lid under lip of corer to seal it

before removing• Very inexpensive

– Piston corer • May be constructed from PVC, designed to collect a complete and

undisturbed sample


Collections– Small Ekman grabs and box corers

May be manually inserted and tripped by divers, insuring proper and complete samples are collected

Geological Measurements and Collections

Box corers may be fitted with a slide hammer for driving into the sediment

• Some corers also have sliding doors – grooves along the open side of the corer guide the removable door down the open face once the corer is in place in the sediment

• This eliminates the need to excavate and expose the lower surface of the corer to install a lower plate before removing a sample from the sediment

Box corer filled with sediment

Slide hammer

Sliding door


Collections– Vibrocoring (vibracoring) – collecting

cores of unconsolidated material by driving a tube with a vibrating device (vibrohead)• Three types of vibrators:

– Pneumatic– Hydraulic– Electric

Pneumatic vibrocorers – can be made to work underwater with very few adjustments and don’t involve the use of electrical current. They work best in relatively shallow water because of increased air consumption at depth. They also require a cumbersome compressor, and the hose becomes an impediment in swift or choppy waters.

Hydraulic vibrocorers – Do not share depth limitations with pneumatic corers, but do require a hydraulic power plant and an umbilical hose.

Hydraulic corer

Electric vibracorers – are more efficient (have a better force/weight ratio) than other types, and do not require umbilical hoses or large compressors or power plants.


Collections• Heavy cores may be

brought to the surface with lift bags

Measuring Temperature

• Hand-held thermometer– Generally encased in stainless steel or

plastic

• Temperature data loggers– Long term– May be downloaded to computer after

retrieval or in situ• Fouling organisms may be issue – users often

wrap download connection points with tape or encase thermometer in PVC

Multiparameter Instruments

• Conductivity, Temperature, and Depth units (CTDs)– May measure other parameters such as

salinity, fluorescence, pH, turbidity and oxygen and may take water samples from different depths

– May be small enough for divers to swim with them underwater to collect discreet data from precise locations

CTD instrument underneath

Niskin Bottles for water

sample collection

Measuring Water Motion

• May be difficult and complex to measure– Plaster

• Blocks of plaster are weighed, affixed to some sort of framework and deployed

• The plaster dissolves in water – faster or slower depending on water velocity

• After recovery, the plaster is dried and weighed again; differences in weight give a relative measure of water motion

Plaster attached to cards (referred to as “Clod cards”). The one on the left has not been deployed – the other two have. Note the size difference


– Fluorescent dye • useful for determining current direction and

velocity - may be released and visually tracked and timed, or recorded on a video camera with a timer


• Current meters– Small hand-held flow meters

• Different rotor size for different water velocity ranges


• Current meters may also be attached:– Taut- line mooring – current meter is attached

to a line that is weighted, anchored, or fixed to a sand anchor in soft sediment• Under a strong current, however, the meter

will be deflected– Rigid mooring – will prevent deflection of

current meter• Inexpensive option: concrete block with four

out-riggers for stability, and a vertical pole with a swivel on top for the current meter

Rigidly moored current meter on tripod

Measuring Light

• A variety of light meters are available– Divers may use hand held light meters for

measuring light in precise locations– Light meters may also be deployed for long

periods of time in specific locations

Light meter collector

Diver uses handheld light meter to determine level of light reflected from coral

Sound

• Measuring sound underwater often requires the deployment of transducers (for transmitting sound) and hydrophones (for listening to sound emitted from both biological and physical sources) – these are sometimes quite large

Biologist using video and hydrophone to record fish sounds

Diver deploying transducer

Chemical Measurements

• May range from simply collecting water in a plastic container to using sophisticated collection techniques and analyzing devices

Van Dorn Bottle –May be mounted on scuba cylinders and tripped by diver at precise time and location to collect discrete water sample for analysis

Sediment oxygen demand chamber – may be positioned by divers at specific locations – used to measure sediment oxygen demand

Underwater Archaeology

• Underwater archeologists locate, draw, excavate, and recover material objects in order to better understand history and culture

• Divers are integral to this process

Archaeologyand Low Visibility

• Because many sites of archeological interest are located in coastal environments, estuaries, or rivers, a great deal of underwater archaeology takes place in locations with poor water visibility

Dredging during 1992 Maple Leaf expedition

Low Visibility - Measuring

• Clear ziplock plastic bags (“Brody Bags”) filled with water may be used to view measuring tapes in low visibility situations

• The bag is placed on the tape and a flashlight is used for illumination– The bag may be made more secure by applying

duct tape to the sealed portion of the bag

• Before recording measurements, it is always a good idea to have a diver swim the tape to ensure it is not snagged somewhere

Archaeology – Mapping

• Mapping is the process of representing the arrangement of objects in two- or three-dimensional space - this is done by taking measurements– Site maps are two dimensional plan views looking

down from above, using an X and Y coordinate system– The third dimension, or Z coordinate, provides depth

or elevation data (profile views use the Z coordinate to record cross sections that show the vertical components of a site)

A 2-dimensional and 3-dimensional coordinate system


• Establish a number of fixed points (datums) across the site – measurements are taken from these datums which are used as reference points

• An intact wreck may have only two datums – bow and stern

• Datums: • Must not move• Must be precisely located (if using more than one datum, and you

usually are, they must be precisely located in reference to each other in order for your site map to be accurate)

• Datums should be high enough not to be obstructed when taking measurements


• Fix a baseline (usually a tape or line marked in regular increments) between datums

• Baselines allow three things to be done:1) Mapping of features that fall under the baseline2) Making measurements away from the baseline3) Creating a mapping grid over the site

1)

2)

3)

Archaeology – Mapping – Horizontal Offsets

• Involves taking measurements at right angles to the baseline

• This method is best suited to document objects located near the baseline– The accuracy of this method relies on judging right

angles. A useful technique is to place the zero end of the tape on the point to be plotted and to move the other end along the datum line until the shortest distance is noted, thus giving a line perpendicular (i.e., 90 degrees) to the baseline

– Offsets must be taken in the horizontal plane

Archaeology – Mapping – Horizontal Offsets

1) Taking an offset measurement from the baseline to a target object; 2) Establishing a 90-degree right angle; and 3) Plotting the offset measurement on the site map

Archaeology – Mapping – Vertical Offsets

• Vertical offsets are generally taken from a level baseline. The baseline can be made level using a simple and inexpensive mason’s line level. A tape positioned close to, and parallel to, the baseline proper provides a reference for vertical measurements. Vertical measurements are taken from the level baseline, not the reference tape. A tape can not be adequately leveled. Vertical measurements can be taken by using a plumb bob and scaling rod dropped from the baseline along the reference tape to take measurements down to the object to be documented.

Archaeology – Mapping – Vertical Offsets

Diver recording vertical offset measurements from a horizontal baseline

Archaeology – Mapping - Trilateration

– Trilateration (or triangulation) involves using the sides of a triangle to map

Distance measurements are taken from fixed datum points 1 and 2 to the target to be surveyed; a third measurement is taken from datum point 3 for precision accuracy


• Distance measurements are taken from two datum points whose positions are known (Previous slide) to the target being mapped (for best results – datum points should surround the object). When plotted by hand, the intersection of these two distance lines (arcs centered on the datum points) locates the target point. For precision surveying a measurement from a third known point should be taken, as this will provide an immediate check. If an error is made using two measurements, the two arcs drawn as described above will nonetheless still usually intersect, but with three arcs plotted they cannot intersect unless accurately measured and drawn.


• Trilateration may also be done from the baseline

Distance measurements are taken from the baseline to four points along the mast labeled A, B, C, and D

Distance Line


• The angle of intersection for the distance lines is generally best kept between 60 and 120 degrees – not too obtuse or acute

• Advantages of Trilateration– Accurate over greater lengths than other types of

measurements

• Disadvantages of Trilateration– All measurements should be taken in a horizontal

plane (problematic given that most sites are uneven)– A commonly used method to deal with this is to

establish a horizontal line using a mason’s line level, and stretch a tape along the line; a plumb line can then be used to line up the object to be surveyed

Archaeology – Combining Trilateration and Vertical

Offsets• Mapping objects usually requires the use of

both trilateration and vertical offset techniques• Distance measurements are taken from two or

three fixed datum points to the target to be surveyed

• When plotted by hand, the intersection of these distance lines (arcs centered on the datum points) locates the target

• The measurements should be taken horizontally to ensure that a true distance is recorded

Archaeology – Combining Trilateration and Vertical

Offsets• To document the target’s vertical position, a plumb

bob (weighted tape measure or scaling rod) is dropped from the intersection of the datum measurements down to the surface of the target itself

• It is imperative for an accurate vertical measurement that the horizontal datum measurement lines are kept as level as possible

• Each target point measured should yield two (or three) distances from datum points and one vertical offset distance (see following slide)

Archaeology - Combining Trilateration and Vertical

Offsets

Object

Horizontal Measurement Line

Horizontal M

easurement Line

Baseline

Vert

i cal O

ffse

t d

ista

nce

Archaeology – Removing Sediment

• Tools such as trowels, shovels, brushes, etc… are impractical underwater

• Hand fan - can move loose sediments but is slow

Archaeology – Removing Sediment

• Water induction dredge (see diagram on following slide) - good for moving large amounts of sediment– It consists of a long tube with a bend at one end– High-pressure water (from a water pump) is

injected into the tube– The flow of water along this pipe causes an

induced suction at the working end

• A flexible tube may be added to the suction end to increase mobility of the dredge

Water Induction Dredge

Induction Dredging

Archaeology - Removing Sediment

• Airlift (see diagram on following slide) - also good for moving large amounts of sediment. Pressurized air is introduced into the bottom of a tube. As the air rises up the tube, it expands and this expansion causes suction at the lower end of the tube. The greater the volume of air and the greater the vertical rise from one end of the pipe to the other, the greater the suction (shallow water requires greater volume). Because the airlift is buoyant when in operation, the lower end will have to be anchored or weighted down.

Air compressor

Weighted induction tube

Airlift

Valve – allows diver to control airflow

Airlifts

Biological Research• Before the advent of scuba in the 1940s,

marine biologists relied solely on technologies such as trawls, dredges, grabs, and plankton nets for research– Somewhat akin to putting your hand into a dark sack

and pulling out an unknown sample

• These techniques made it:– Hard to sample specific areas– Hard to assess variability– Impossible to manipulate/ do controlled experiments

• Scuba made possible what was heretofore difficult or impossible

Biological Research• Activities of biologically oriented divers include:

– Observation – making raw or semi-processed recordings of biological phenomena (behavior, abundance, etc…)

• Counting, measuring, observing individuals etc…

– Collection – obtaining specimens (dead or alive) for examination/experimentation

• For observing behavior in lab, fecundity estimates, physiological experiments etc…

– Manipulation – altering the marine environment for a controlled experiment

• Territories, cages, outplants, etc…

Biological Research

• Major areas of underwater biological interest:– Ecology – the factors influencing the

distribution and abundance of organisms– Behavior – actions and responses of

organisms to stimulation– Physiology – internal functions of organisms

and their responses to internal and external influences

– Other fields – biochemistry, pharmacology, evolution

Biological Research- Observation

• Semi-processed observations – The diver makes counts or size measurements while underwater– Sampling Schemes

• Quadrats – used to intensively analyze a fixed area

• Transects –rectangles/strips used for measuring abundance in a set area

Biological Research - Quadrats

• Typically used for small, non-motile or slow moving organisms that are reasonably abundant within a manageable quadrat size– Size – typically 0.1 m2, 0.25 m2 , or

0.5 m2

– Construction – aluminum, welded rebar, or PVC pipe • Typically 4 sided, but 3 sided are good if

dealing with thick algal cover Quadrats

Diver using 3 sided quadrat – note transect line

Typical rectangular quadrats arrayed on a transect line

• Point contact quadrats (% cover)– Strung with lines creating squares

• Where the lines cross – record the species under that point

• Circular quadrats– Use a weight attached to a line – to circumscribe an area

• Effective in areas of high algal cover



• Random point contact– A weighted bar with a string of knots

tied to each end is dropped in a quadrat – Each species or group under the string,

or above it to a specified height, is recorded

Biological Research -Transects

• Typically used for larger, more mobile or less abundant organisms

• Materials – Fiberglass transect tapes– Nylon line marked with tape, heat shrink tubing, lead

sleeves– Permanent leaded core lines secured with anchors

• Transects may be laid ahead of survey - or distance of transect may be assessed after completion

A diver moves along a transect

Diver counting lobsters found within 2 m of a 150 m transect

Biological Research -Transects

• Determining the dimensions of a transect (length x width = area) is done by measuring, using a stiff rod, or estimation– The length and width of the transect must be

scaled according to the abundance and size of the organisms in question

• Observations can be biased by organisms that avoid divers or are attracted to them

• Timed observations:– Record the number of target individuals

passing by a specific point– Record the arrival of target species

Biological Research- Observation

• Raw Observations – Observations (e.g., counts, size) are recorded underwater and summary calculations (e.g., sums, means, densities) are done later

• Photoquadrats – Application – Most useful for documenting

the abundance of non-motile or slow-moving organisms

Photoquadrat images

Divers using photoquadrats – note framers made of PVC

Biological Research – Observation – Photo

Quadrats• Framers – Underwater framers allow reliable,

repeatable pictures. The framer usually supports the camera and flash and indicates the area being filmed– May be made from aluminum stock or even PVC

pipe– Often have scale bars to allow absolute

measurements to be made

• Strategies for analysis– Analyze digital images with computer programs for:

• Counts• Random point intercept (% cover)• Measurements of area

Biological Research – Observation – Underwater

Video• Most often used for documenting the abundance of

motile organisms• Methodology – video may be shot along a fixed

transect for a fixed amount of time• Concerns:

– Visibility must be measured– Some mobile organisms avoid divers, others are

attracted• Analysis:

– Analyze digital video with computer programs

Divers recording video along transect lines

Still from video transect – images may be quantified

Assessing Aquatic Populations

• Non-mobile organisms– Corers for soft sediments

• Coffee can corers– Cut off both ends – Drive into sediment– Put one lid on the top– Dig out one side and slip another lid on the other

opening– Good for large area samples

• Suction corer– Use 1 –2 inch internal diameter PVC tubing– Sharpen the edge– Drive into the sediment– Plug the exposed end with a rubber stopper– Pull the tube from the substrate, place into plastic bag


• Airlifts for hard-substrate organisms– Airlift design

• Typically a long PVC tube (4-8 inch internal diameter) connected to a separate air tank via a first stage and a low pressure port

• Air enters the tube near the opening and expands as it rises, creating suction at the opening

• A sample bag is attached to the far end– This bag must be secured to the end, but be easy to

release and seal

– Procedure• Mark out area with a quadrat• Go over the area quickly to remove loose material

and semi-mobile organisms• Scrape the surface with a wire brush


• Mobile organisms– Traps

• Baited and unbaited traps can be laid out and then recovered after a set period of time

– Slurp guns• Effective when capturing small fish or

invertebrates


– Spear guns/pole spears• Spear guns are effective for larger fish, multi prong

pole spears are more effective with smaller fish (easy to rearm if you miss)

– Hand nets• Made from seine material – rugged, but high drag

and slow• Made from gill net mesh – less rugged, but less

resistance and faster


• Anesthetics/Poisons– Poisons include Rotenone (root of South

American plant), pronox and chem fish– Anesthetics include

• MS-222 – dissolves in water• Quinaldine – dilute to 10% with EtOH or acetone or

isopropanol– Hard to get rid of smell

• Benzocaine• 2-phenozyethanol

– Mix a dye (flouroscene) so that the target area can be monitored

– Application• Place in plastic bag – puncture and squeeze• Place in several large syringes• Plastic squeeze bottle

Study Questions

• Use the following study questions to review some of the information presented in this self study module. When you are finished you can print out your study questions results.

Self-study Questions

Which of these tools are good for distance measurement in direct surveys?a. Ropesb. Linesc. Steel Taped. Vinyl measuring tapee. All of the above


Which type of camera lens can permit detailed photography to cover large areas?a. Wide-angleb. Short-anglec. Normal-angled. None of the above


This method of underwater survey is the acoustic equivalent of direct trilateration.a. Phase Measurementb. Acoustic Gridc. None of the above


What is the simplest method for recording data under water?a. Using a graphite pencilb. Using a white-double sided

plastic boardc. Using a lead pencild. A and B


The best equipment configuration for communications is a full-face mask equipped with a microphone.a. Trueb. False


Baseline studies must be designed without monitoring them at prescribed intervals.a. Trueb. False


What can the diver use to capture larger, less motile zooplankton?a. Plastic containersb. Netsc. Glass containersd. A and C


Can organism density and distribution be determined photographically without disturbing the aggregation?a. Yesb. No


Direct in situ observation of lobsters is the most effective way to study lobster ecology and behavior.a. Trueb. False


Which of these are basic tools that geologists should carry?a. Compassb. Depth gaugec. Rulerd. Noteboarde. All of the above


Which of these mapping methods can be used in water or on land, using plane tables?a. Peterson’s Wheel-Meter Tape

Methodb. Meter Tape Triangulation Methodc. Plane Table Triangulation Methodd. Dumas Measuring Frame Method


Does underwater surficial mapping require only identification of materials and features that compose the area?a. Yesb. No


During experimentation, which processes are explored in their interrelationships?a. Geologicalb. Biologicalc. Physicald. Chemicale. All of the above


During which phase does the most important aspect of the relocation process of instruments occur?a. Inspectionb. Deploymentc. Cleaningd. Recovery


Bulk water samples can be obtained by swirling large plastic bags through water until filled.a. Trueb. False


Which of these can be used for animal capture techniques?a. Netsb. Trawlsc. Seinesd. Grabse. Dredgesf. All of the above


Where is most scientific diving carried out?a. Deep watersb. Shallow watersc. Nearshore watersd. None of the above


Which of these is a method for tagging marine organisms?a. In situb. Electroshockedc. Captured and brought to the

surfaced. A and C

procedures for scientific diving. sources american academy of underwater sciences, proc. of...

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