NOAA Technical Memorandum NMFS 

MAY 1986 

THE LIMITATIOINS OF FISH TRACKING SYSTEMS: 

ACOUSTIC AND SATELLITE TECHNIQUES. 

1. G. Priede 

N (3 A A-T M - N M F S-S W FC-6 1 

U.S. DE:PARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Southwest Fisheries Center 
NOAA Technical Memorandum NMFS 

The National Oceanic and Atmospheric Administration (NOAA), organized in 

1970, has evolved into an agency which establishes national policies and 

manages and conserves our oceanic, coastal, and atmospheric resources. An 

organizational element within NOAA, the Office of Fisheries is responsible for 

fisheries policy and the direction of the National Marine Fisheries Service 

(NMFS). 

In addition to its formal publications, the NMFS uses the NOAA Technical 

Memorandum series to issue informal scientific and technical publications when 

complete formal review and editorial processing are not appropriate or feasible. 

Documents within this series, however, reflect sound professional work and may 

be referenced in the formal scientific and technical literature. 
NOAA Technical Memorandum NMFS 

This TM series is used for docurnentatmn and timely communicahon of preliminary results. imterim reports. a 

speclal purpose information. and have not received complete formal revlew. editorial control. a detaled edding 

1 

z .? 

2 

a 

MAY 1986 

THE LIMITATIONS OF FISH TRACKING SYSTEMS: 

ACOUSTIC AND SATELLITE TECHNIQUES. 

1. G. Priede 

University of Aberdeen 

Department of Zoology 

Aberdeen AB9 2TN Scotland 

! 

NOAA-TM-NMFS-SWFC-6 1 

U.S. DEPARTMENT OF COMMERCE 

Malcolm Baldrige. Secretary 

National Oceanic and Atmospheric Administration 

Anthony J. Calio, Administrator 

National Marine Fisheries Service 

William G. Gordon. Assistant Administrator for Fisheries 
THE LlWlTATlONS OF FISH TRACKING SYSTEMS: 

ACOUSTIC AND SATELLITE TECHNIQUES 

I.G. Rledel 

I NTROWCT I ON 

The purpose of this paper is to consider the I imitations of tracking 

technology as appl led to the problem of tuna migrations. A number of 

workers have successful ly tracked tunas using acoustic transmitters 

attached to individual fish. This has provided much detailed behavioral 

Information, but long-term tracking beyond a day or two has proved 

difficult (Hunter et al. 1986). The I imitations of acoustic tracking 

technology wll I be assessed in the first part of this paper. In the second 

part the possi bil ity of using satel I ite locatable radio tags is discussed. 

Basic information has been col I ated to enabl e the non-engineer to interpret 

specif ications of qui pment. 

ACOUSTIC TRACKING 

The normal basic tracking system consists of a transmitter on the fish 

which em its pul ses which can be detected by a di rectional hydrophone 

mounted on a ship. The bearing of the fish relative to the ship can be 

determ I ned and an approxi mate est I mate of range 1 s obtai ned from si gnal 

level. Using such a system it is possible for a ship to follow a fish 

continual ly. Primary considerations regarding the transmitter are: 

1. range Over which the signal can be detected 

2. size 

3. life of the batteries. 

These are determined by the fol low ing engineering specif i c a t i o n s o f t h e 

transmi tter : 

1. source level 

2. frequency and range 

3. pul se rate and pul se I ength 

4. battery size and chemistry 

5. transmitter size 

6. tracki ng performance 

7. satel I ite tracking. 

'Department of Zoo1 ogy, University of Aberdeen, Ti I lydrone Avenue, Aberdeen 

AB9 ZTN, SCOTLAND 

'This review was presented during a technical workshop on existing and new 

technologies that could be employed to measure tuna movements. The workshop 

was one of a series of three on tuna movements held in 1985 which were 

Jointly sponsored by the Inter-American Tropical Tuna Commission and the 

Southwest Fisheries Center of the U.S. National Marine Fisheries Service. 

For further details regarding the workshops see Hunter et al 1986. 

1 
Source Level 

In underwater acoustics the source level of a transmitter is usually 

measured in terms of pressure detected by a hydrophone at a standard 

distance (1 m) from the source (Figure 11, e.g. 1 Newton/m* at 1 m = 1 

Pascal (Pa) at 1 m. Normal ly this is expressed in decl bels (dB), a ratio 

re1 ative to a standard reference pressure, The current international 

standard for underwafer acoustics is a reference pressure of 1 pPa. Thus 

Source Level (SL): 

SL = 20 log10 (p/po) (1) 

When po = 1 pPa Thus a manufacturer mlght 

specify the output source level of the transmitter as: 120 dB re 1 pa at 1 

m. Some manufacturers sti I I use 1 pbar as the reference pressure. 1 pbar 

= 0.1 Pa; to convert from Db re 1 ubar to Db re 1 pPa add 100 (Figure 1). 

and p = 1 Pa, then SL = 120 dB. 

100 

80 

60 

40 

20 

10 

Power Watts 

source level 

ref lpPaat lm 

Figure 1. Source levels and power outputs of underwater acoustic 

transm 1 tters. 

2 
The decibel notation is very convenient since all calculations 

regarding signal levels, attenuation, etc. can be carried out by simple 

addition or subtraction. Some manufacturers, however, stil I specify their 

equipment output power in watts. This has the advantage of being 

unam bi guous, avoi di ng the confusion ar i si ng i n deci bel notation resul ti ng 

from use of different reference pressures. To convert from watts acoustic 

power output (PI to source level dB re 1 pPa at 1 m, the fol lowing equation 

should be used: 

SL = 170.77 + 10 IOgloP 

Given a transmitter of known source level, it is possible to predict 

the range at which it can be detected. With a good-qual ity hydrophone and 

receiving system the practical I imit occurs when the signal cannot be 

distinguished above ambient sea noise, i.e. a signal-to-noise ratio of 0 dB 

(Stasko and Pincock 1977). Assuming the signal is emitted 

omnidirectional ly, the power generated spreads out sphertcal ly, leading to 

a fa1 I off in power with range in accordance with the inverse square law. 

The dB transmission loss (TL) due to spherical spreading is: 

where r = range in meters. Since log 2 is approximately 03 that gives a 6 

dB loss for every doubling in range or 20 dB for every decade increase. 

The 6 dB rule of thumb is quite accurate at short ranges. As range 

increases, however, transmission loss due to absorption in seawater becomes 

significant and Equation 3 must be modif led as follows: 

TL = 20 loglor + ar 10'3 ( 4) 

where u= absorption coefficient in dB per km. 

to allow for t h e f a c t that range (r) Is in meters and n Is in dB per km. 

The absorption coeff icient varies with temperature, sal ini ty, pressure and 

frequency. An important consideration from the point of view of acoustic 

transmitter design is that absorption is proportional to the square of 

f req uency . 

The low3 term is required 

Frequency and Range 

Figure 2 shows the relationship between absorption coefficient and 

frequency. In seawater there are important ionic relaxation effects which 

lead to discontinuities in the basic square law relatlonshlp. Figure3 

shows the ca I CUI ated transm i ssi on I osses at di f f erent f req uenci es as a 

function of range. Up to 100 m, loss follows the 20 dB rule; but up to 

1000 m, absorption losses become significant, especially at high 

f req uenci es. 

From the point of view of gaining maximum range with minimum power 

requirement the lowest possible frequency should be used. In the 

transmitter the signal is usual ly generated by a hollow cy1 indrical pieze 

ceramic transducer. Greatest efficiency is achieved if this is driven at 

its resonant frequency. The resonant frequency decreases w ith increase i n 

diameter. A popular size is 12.5 mm (1/2 inch) diameter which resonates at 

3 
100 

10 

1 .o 

0.1 1 

100 

Frequency khz 

1( 

15.5% 

1 

IO 

Figure 2. The relationship between absorption coefficient and temperature. 

4 
Figure 3. Transmission loss with range at different frequencies. 

about 75 kHz and 25.4 mm (1 inch) which resonates at 40 kHz. Figure 4 

shows the relationship between frequency and transducer diameter. The 

choice of frequency therefore immediately begins to define the size of the 

transmitter. Normal ly the transmitter Is a cy1 inder Just big enough to 

enclose the transducer and batteries are chosen of a diameter to match the 

transducer. 

Below 20 kHz the diameter is too large to be seriously considered for 

fish tags. In general frequencies between 30 kHz and 80 kHz are used, 

although In freshwater w ith lower absorption coeff icients 220 kHz has been 

successful ly used in very smal I transmitters (Young et al. 1972). Mitson 

and Storeton-West (1971) used a 300 kHz transmitter for tracking plaice at 

sea. This was a transponding fish tagy and the frequency was determined by 

the working frequency of the sector-scanning sonar with which it was used. 

The working range of this system was not more than about 500 m. 

It is possible to take advantage of low absorption characteristics at 

low frequencies in smai I transmitters by running a smal I transducer below 

resonant frequency. This is general ly ineff icienty and only low source 

levels can be achieved. Consideration perhaps should be given to 

al ternative transmitter geometriesy getting away from the long cy1 inder 

w ith the transducer al lgned coaxial Iy. 

5 
100 

E 

E 

& 

'E 

2 10 

+ 

v) 

C 

I1 

50 100 500 

Transducer Diameters 

1000 

I I II I I I II 

500 

E 

c 

a 

2 -100 

I 

50 

- 10 

Figure 4. Transmitter transducer diameter (hol I ow resonant PZT cy I i nder) 

in relation to frequency. 

Successful tracking depends on a good directlonal receiving 

hydrophone. The size of the hydrophone required also increases with 

decrease in frequency. Figure 4 gives the dimensions of a basic circular 

p i s t o n r e c e i v i n g element with a directivity index of 20 dB (Urick 1967). 

Larger di ameters give improved di rectiv lty, but the sl ope of the 

relatlonship remains the same. It can be seen that above 40 kHz it is easy 

to bu i I d compact I i ghtw ei ght hydrophones of appropr I ate performance, but 

below 20 ki-lz hydrophones become I arge and unw le1 dy, necessitatlng special 

mountings--preferably permanently fitted to the hul I of a ship-and with 

hydraul ic servo controls. Bel ow 10 kHz steerabl e dl rectional hydrophone 

technology really breaks down, and location would be carried out by 

measurement of time delays in some sort of spaced receiving array. 

A third consideration in choice of frequency is the Interference from 

animals and whether the acoustic signal wlll be detected by animals, 

including the fish to which t h e t r a n s m i t t e r is attached. Many fish can 

6 
detect and produce sounds at up to 10 kHt but most fish sounds are at low 

frequencies (Hawkins and Urquhart 1983). The usual fish tracking 

frequencies of 30 to 100 kHz are unlikely to affect fishes. Marine 

mammal SI however, can produce sounds at up to 100 kHz. I have I lstened to 

porpoises in the Bay of Panama apparently trying to communicate with a 75 

I<Hz transmitter bel ng used to track a sea snake. Unfortunately there is no 

useful acoustic frequency band in the sea which is not utilized by marine 

mammal s. 

The detected I eve1 (DL) of the signal Is determined by the source 

level and the transmission loss: 

The detection threshold at extreme range occurs when DL is equal to the 

noise level (NL). Thus information on ambient noise levels in the sea is 

required to predict range. Figure 5 shows typical noi se 1 eve1 s at the sea 

surface in deep-sea conditions (Urick 1967; Clay and Medwin 1977) for the 

frequencies of interest. Above 50 kHz noise is dominated by thermal noise 

w hi ch I ncreases w 1 th frequency at 6 dB per octave. Bel ow th i s frequency 

sea-surface noise, which decreases at about 6 dB per octavey is dominant. 

Thi s I ncreases I n accordance w ith w Ind speed and sea state as I ndi cated. 

Heavy rain can generate up to 80 dB below 30 kHz Ship noise can add about 

30 dB and general ly follows the -6 dB slope in re1 atlon to frequency. In 

coastal regions noise levels would typical ly be 10 dB above the levels 

indicated. There is a clear minimum In the noise spectrum In the 50 - 100 

kHz band. 

The noise level detected by a receiver depends on the bandw ldth over 

which it detects incoming energy. Data in Figure 5 are given in terms of 

spectrum level/Hz (SR). The noise level detected Is given by: 

NL = SPL + 10 lOg1oW (6) 

where W = bandwidth in Hz, e.g. for 1 kHz bandwidth: 

Omnidirectional hydrophones detect noise from al I around, and 

therefore require a higher signal level than a directional hydrophone in 

the same environment. This difference Is usual ly expressed as the 

directivity index, DI, which Is measured in dB and can be regarded as the 

hydrophone gain. The best directional hydrophones have a directivity index 

of about 30 dB. Detection threshold depends on numerous factors, including 

optimum bandw ldths and pulse lengthy as we1 I as hydrophone design. As a 

first approximation for a typical receiving set, equating noise level and 

signal level gives a good estimate of maximum range. On this basis maximum 

range at different source levels for 4 different frequencies is shown in 

Fi gure 6. 

Figure 6 shows that low frequencies are best for tracking at long 

ranges. However, also apparent is the fact that high-frequency 

transmitters are signif icantly better at short ranges. This is because at 

7 
100 

80 

60 

40 

20 

0 

10 

Heavy 

0'- 

00 

0 

I I II I 1 I I1 

50 100 

Frequency kHz 

500 1000 

Figure 5. hbient sea noise spectra. 

8 
E 

8 

2 

c 

- 

10 k 

1 

10 

// 

I I I I I I 

S.L. dB 

FIgure 6. Predicted ranges of different transmitters at different 

f r eq uenc i 8s. 

high frequencies there Is less noise and at short ranges absorption loss is 

not significant (Figure 3). This gives rise to an effect that is not 

widely appreciated: if two transmitters of equal source level are tested 

close to the ship the larger, low-frequency transmitter will be more 

diff lcul t to detect. The benefits of low frequency transmitters become 

apparent only at long ranges. No al lowance has been made for ship noise, 

but unl ess a very good hydrophone 1 nstal I ation 1 s used w ith a good 

acoustically transparent dome mounted on the right part of the hull, 

9 
performance of the low-frequency devices 'can be disappointing. At ranges 

of less than 1000 m there is probably no great benefit to be gained from 

use of frequencies below 50 kHz. 

Pulse Rate and Pulse Length 

To be trackable a pulse rate of about 1 M is necessary. A high pulse 

rate leads to excessive power consumption, but a pulse rate of much less 

than 1 Hz makes mobile tracking difficult. Pulse length Is typically set 

at 10 ms, giv Ing a duty cycl e of 1% at 1 Hz. Shorter pul se I engths can be 

used, but usual ly a higher source I eve1 is necessary to ensure detection. 

Battery Size and Chemistry 

In recent years I ithium batteries have resulted In major advances in 

energy density from 100 Wh/kg for zinc-carbon to over 200 Wh/kg for I ithium 

cel Is. Many different electrolytes are used, leading to a wide choice of 

I ithium cel Is. Examples are I ithium manganese dioxide, 210 Wh/kg at 2.7V 

(Duracel I), and I ithium thionyl chloride, 350 Wh/kg at 3.5V (SAFT). 

Construction of the cell can also lead to differingabil lties to sustain 

high currents, etc. (Attewel I 1985). No major further advance in energy 

density can be expected for primary cel I battery systems; there w I1 I be an 

evolution of I ithium systems to meet different speclf icatjons for different 

appl icati ons. 

Figure 7 gives the energy required at different source levels and 

transmitter I ife times at a 1% duty cycle. Any quiescent current is 

ignored and eff iciency of conversion of electrical to acoustic power is 

assumed to be 17%. A scale of battery sizes assuming 220 Wh/kg energy 

density Is inserted. There are liable to be non-linearities In practice, 

especial ly in the smal I er sizes. Casing takes up a I arger proportion of 

the weight in a smal I battery, and smal I batteries cannot del iver high 

currents easily even if the theoretical energy density is available. 

Transm i Iter S I ze 

Figure 8 gives information on transmitter dimensions in relation to 

I ife and source level. This is intended to give some indication of what to 

expect when requesting a given performance. There can be wide variation 

between different manufacturers and, particularly high-frequency 

transmitters (75 kHz) can be smal I er than indicated. The curves predict 

quite well the size of large transmitters but in small transmitters 

variations in package design can lead to vast differences In overall size. 

Given an existing transmitter the curves indicate quite well the rate of 

increase In size with life. The chart can only be used to indicate trends. 

Real Istic f ish transmitters do not achieve source levels In excess of 

170 dB. Cavitation problems I imit the maximum power it is possible to 

radiate from a smal I transducer; for example, for a 1 cm area, 166 dB is 

the I imit. Maximum efficiency is best achieved well below the cavitation 

I imit. A major source of variation is I ikely to be transmitter efficiency; 

if oscillators are carefully tuned to the resonant frequency of individual 

10 
10000 

1000 

f 

1 oc 

10 

1 .o 

0.1 

1 

- 100000 

- 10000 

- 1000 

- 100 

- 10 

- 1.0 

-0.1 

10 100 1000 

LIFE days 

Figure7. Energy required for 1% duty cycle at different transmitter 

source I eve1 s. 

11 
100000 

10000 

1000 

0 

5 

s 100 

10 

1 .o 

1 10 100 1000 

Life days 

A 

5 

8 

d 

E 

Y 

cv i 

E 

- lo00 

500 

- 100 

50 

- 10 

Figure 8, Approximate transmitter sizes for two different source levels dl3 

re 1 uPa at 1 m. 

transducers great improvement in eff iclency can be achieved. In series 

production this is not usually possible and transmitter frequency is set to 

a standard crystal frequency disregard1 ng I ndivldual transducer 

characteristics. There w 11 I8 therefore, be significant individual 

var I ati on I n transm i tter ef f ici enci es. 

12 
Tracki ng Perf omance 

To ensui . good tracking performance the system should be designed to 

provide good feedback on fish location to enable commands to be issued for 

maneuvering of the ship. Detection of bearing is usually not a problem. 

It i s, however, easy to loose contact with the fish as it moves rad1 a1 ly 

away from tne ship. A I-m fish moving at 5 body lengths per second can 

escape to 1000 m in 200 seconds (33 minutes), so an immediate response is 

necessary from the ship to keep in touch. 

Range Is usual ly detected by change in signal strength as the fish 

moves away. Figure 9 shows this effect at two favored tracking 

frequencies, using the data from Figure 3 plotted on a linear range scale. 

If it is assumed that a 10-dB change is required for detection at 400 m, 

then a 50 m change In range is required at 75 kHz. At 30 kHz much larger 

changes are necessary. Whi I e the I ow-frequency transmitter can be detected 

at 3000 m, it is difficult to interpret what is going on. The fish can 

move out of range without the operator being aware of the facf. until it is 

-too late or it can disappear Into shadow zones created by the thermocl i ne. 

For small fish the 30 kHz transmitter is probably too large. In 

1 arger f I sh there are benefits to be gai ned in terms of range, but tracking 

may remain difficult. Consideration should, therefore, be given to using 

transponding systems which would give range and bearing information. 

Greer-Walker et al. (1971) were able to track plaice at sea with a working 

range of only a few hundred meters using transponder fish tags in 

conjunction with a sector scanning sonar providing an instantaneous visual 

displ ay of fish location relative to the ship. A transpondlng system 

working at 30 kHz would g i v e t h e benef Its of long range but with vastly 

improved range resol ution. More extended tracking may then be possi bl e. 

A serious I Im it to I ong-term acoustic track1 ng Is crew fati Que. To 

achieve more than a few days continuous tracking requires immense 

dedication and perseverance on the part of the ship's crew. 

Satel I ite Tracking 

Priede (1984) first successfully tracked a fish by satel I ite using the 

ARGOS data col lection and location system carried on board NOAA sate! I ites. 

The species chosen, the baski ng shark (Cetorh I nus mimus), is ideal for 

satellite tracking since it has the habit of basking near the sea surface 

for long periods of time, and at an adult length of over 7 m is capable of 

carrying vbzp I arge transmitter packages. Locations were obtained whenever 

the animal was on or near the sea surface. An ARGOS transmitter was built 

into 7 kinyant package towed by the animal. Eventual ly this package broke 

loose and covtinuous locations by ARGOS (12 per day at latitude 57'") 

indicafed ?he last known location of the animal. 

The question immediately arises as to whether this technology can be 

adapted to bu 1 I d a ttp~p-uptr tag for tunas w hi ch would break loose after a 

predetermined time interval to give a single location. Implementation of 

such a pop-up tag using conventional VHF radio location Is discussed by 

Ne1 son and McKi bben (1 981 1. 

13 

.- 
E 

Q F 

I 

L 

E 

R 

I 

L 

0 0 

a0 0 

d 

sol BP 

6 

K 

0 

L 

YO 

b 

t 

14 
The principles of satell ite location systems are discussed fully by 

Prlede (1983, 1985) and success depends critical ly on a very stable 

transmitter oscl I I ator frequency. Radiated power is about 2 W w Ith a 

minimum message length of 360 ms emitted approximately every 60 seconds 

During one satel I lte overpass at least 4 messages spread over 420 s must be 

received by the satellite receiver. Studies on animal tracking in the past 

have been hampered by poor transmitter performance leading to up1 inks but 

subsequent rejection of messages for location calculations due to excessive 

frequency drift, etc. It Is possible, however, with careful design to 

match and exceed the mi nimum performance characteristics demanded by 

Serv 1 ce ARGOS. 

TX 

Since the successful track of a shark, work in Aberdeen has 

concentrated on real lzing small ARGOS transmitters for use on blrds (French 

1984, 1986). The smallest ARGOS certified transmitter 50 far has a volume 

of 85 cm3 for transmitter components and 33 cm3 for batteries with 8 days 

I ife. This is configured in a flat disc 100 mm In diameter for attachment 

to a bird. If this were reconfigured In a cylindrical package it would be 

the size indicated in Figure 10. 

battery 

ARGOS TRANSMITTER 

Figure 10. Probable size of a towed satel I Ite locatable radio tag using 

exi sting techno1 ogy. 

Gradual size reductions can be expected given signif icant investment 

In Mi n I-ARGOS PTT technology. Twepoi nt satel I I te tracking of the I arger 

tunas seems f easi bl e in the foreseeabl e future. 

15 
REFERENCES 

ATTEWELL, A. 

1985. Power sources. R Mitson (editor), Animal Telemetry in the 

Next Decade, p. 32-39, summaries of papers from a meeting he1 d at 

the Fi sheri es Laboratory, Low estof t, Engl and on 9-1 0 January 1985. 

CLAY, C.S. and H. EDWIN. 

1977. Acoustical Oceanography. Wiley and Sons, New York, 544 p. 

FRENCH, J. 

1984. Tracking birds. Argos News1 etter 19:ll-12. (Service Argos, 

Toul ouse) 

FRENCH, J 

1986. Satel I ite technology for tracking birds and sea mammals. Ph.D. 

Thesi s. University of Aberdeen, Scott and. 

GREER-WALKER, M. 8 R.B. MITSON, and T. STORETON-WEST. 

1971. Trial s with a transponding acoustic f i sh tag tracked w 1 th an 

el ectronic scanning sonar. Nature (Lond.) 299:1%-198. 

HAWKINS, A.D. and G.G. URBUHART. 

1983. Tracking f ish at sea. JA A.G. MacDonald and I.G. Priede 

(editors), Experimental Biology at Sea, p. 103-166. Academic 

Press, New York 

HUNTER, J.R. 9 A.W. ARGUE. W.H. BAYLIFF, A.E. DIZON, A FONTENEAU, 

D. GOODMAN, and G. SECKEL. 

future research. FA0 Fish. Tech. Pap. (In press) 

1986. The dynamics of tuna movements: an evaluation of past and 

MITSON, R. B. and T. J. STORETON-WEST. 

1971. A transpondi ng acoustic f ish tag. Radi o El ectron. Eng. 41 : 

483-489. 

NELSON, D.R. and J.N. McKIBBEN. 

1981. Timed-re1 ease, recoverabl e, ul trasonic/radi o transm ltters for 

tracking pelagic sharks. F.M. Long (editor), Proc. Third Inter. 

bnf. W i I dl. Biotel emetry, p. 90-1 04. ICWB, University of Wyoming, 

L ar am i e, Wy om i n g. 

PRIEDE, I.G. 

1983. Use of satellites in marine biology. J-,@ A.G. MacDonald and 

I.G. Priede (editors), Experimental Biology at Sea, p. 3-50.. 

Academ ic Press, New York 

PRIEDE, I.G. 

1984. A bask1 ng shark tracked by satel I ite together with simultaneous 

remote sensing. Fi sh. Res. (Amst.) 2: 201-216. 

16 
PRlEDE, I.G. 

1985. S~*F.I I ite systems and tracking of animals. h RB Mitsosl 

(edii-,:lr Animal Telemetry in the Next Decade, p. 51-56. Summaries 

of papers from a meeting he1 d at the Fisheries Laboratoryr 

Lowestoft, England on 9-10 January 1985. 

STASKOr A.B. and D.G. PINCOCK. 

1977. Review of underwater biotelemetryr with emphasis on ultrasonic 

techniques. J. Fi sh. Res. Bd. Canada 34:1261-1286. 

URiCK, R. J. 

1967. Pri nci pl es of Underwater Sound f OT Engi neers. McGraw-Hi I It New 

York, 384 p. 

YOUNG, A.H., P. TMLER, F.G.T. HOLLIDAY and A. MacFARLANE. 

1972. A smal I sonic tag for measurement of locomotor behaviour In 

fish. J. Fi sh Biol. 4: 57-65. 

17 
RECENT TECHNICAL MEMORANDUMS 

I 

Copies of this and other NOAA Technical Memorandums are available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22167. Paper copies vary in 

price. Microfiche copies cost $4.50. Recent issues of NOAA Technical Memorandums from the 

NMFS Southwest Fisheries Center are listed below: 

NOAA TM-NMFS SWFC 51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

Estimating dolphin juvenile survival rates from the proportion 

of calves nursing. 

T. POLACHECK 

(October 1984) 

Operational plan for NMFS albacore program. 

R.H. PARRISH, et al. 

(May 1985) 

AI bacore fishing and windspeed. 

P.N. SUND 

(June 1985) 

Proceedings of the workshop on the fate and impact 

of marine debris, 27-29, November 1985, Honolulu, Hawaii. 

R.S. SHOMURA and H.O. YOSHIDA (Editors) 

(August 1985) 

The Hawaiian Monk Seal and Green Turtle on Necker Island, 1983. 

R.J. MORROW and E.K. BUELNA 

(November 1 985) 

Proportions of species of dolphin in the eastern tropical Pacific. 

J. BARLOW and R.S. HOLT 

(January 1986) 

A budget simulation model for west coast albacore trollers. 

S.F. HERRICK and K.L. CARLSON 

(February 1986) 

The Hawaiian Monk Seal on Lisianski Island, 1983. 

T.C. JOHANOS and A.K.H. KAM 

(February 1986) 

Hawaiian Monk Seal observations and captive maintenance project 

at Kure Atoll, 1981. 

W.G. GILMARTIN, R.J. MORROW, and A.M. HOUTMAN 

(March 1986) 

Determining fish movements from an “archival” tag: 

precision of geographical positions made from a time series of 

swimming temperature and depth. 

P. SMITH and D. GOODMAN 

(May 1986)