NOAA Technical Memorandum NMFS 

AUGUST 1084 

HAWAIIAN MONK SEAL POPULATION 

RESEARCH, LISIANSKD ISLAND, 1982 

NOAA-TM-NMFS-SWFC- 47 

U.S. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Southwest Fisheries Center 
NOAA Technical Memorandum NMFS 

The National Oceanic and Atniospheric Administration (NOAA), organized in 1970, has evolved intoan 

agency which establishes national policies and manages and conserves our oceanic, coastal, and atniospheric 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 NOAATechnical 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 
ERRATA 

Schlexer, Fredrick V. "Diving patterns of the Hawaiian monk seal, 

Lisianski Island, 1982." U.S. Dep. Commer., NOAA Tech. Memo. NMFS, NOAATM-NMFS-SWFC-41. 

the dives was greater than 36 m." 

1984. 

Page 2, paragraph 3.--Delete sentence "The mean depth of 

Alcorn, Doris J. 

U.S. Dep. Commer.! NOAA Tech. Memo. NMFS, NOAA-TM-NMFS-SWFC-42. 

Replace page 32 with the attached. 

"The Hawaiian monk seal on Lapean Island: 1982." 
. 

32 

Appendix B.--Summary of Laysan Island censuses, 1982 (M = male, F = female, 

9 = sex unknown, W = weaned, N = nursing). 

Total 

In NonAdult Subadult Juvenile Pups 

Date M F 7 M F ? M F ? W N Observer1 molt pups Pups 

31172 -_ -_ __ 3/18 16 10 30 

3/21 19 15 20 

3/23 13 12 26 

3/26 17 23 26 

3/28 32 18 19 

3/30 30 16 22 

411 22 16 16 

413 25 15 22 

415 30 21 18 

418 34 21 15 

4/10 17 17 26 

4/12 43 20 15 

4/15 23 25 9 

4/17 32 27 14 

4/19 28 21 11 

4/23 20 18 17 

4/25 20 15 15 

4/27 28 24 11 

4/29 26 19 24 

511 25 21 7 

513 33 13 13 

515 31 26 11 

517 32 27 11 

519 20 26 2 

5/11 30 25 8 

5/13 14 28 3 

5/15 23 22 12 

5/17 28 23 10 

5/19 19 16 11 

5/21 21 23 8 

5/23 31 19 9 

5/25 20 17 12 

5/27 26 20 13 

5/29 26 25 4 

-- -- -- -- -- -- 0 5 AK, DA 

5 216 2512 16 DA 

6 3 5 5 8 11 1 8 AK,DA 

4 015 8415 19 DA 

7 5 12 4 7 8 1 8 AK,DA 

31310 64 8 18 DA 

3 10 7 3 4 3 1 7 AK,DA 

4 6 6 75 8 19 DA 

4 5 11 2 3 2 2 9 AK,DA 

11 6 10 9 3 11 2 9 DA 

8 5 12 3 2 4 3 9 AK,DA 

1 5 5 23 8 3 9 DA 

9 5 11 3 1 3 3 0 AK,DA 

8 710 52 5 3 1 DA 

8 16 21 4 3 1 AK,DA 

1314 6213 2 1 DA 

411 3 61 4 3 1 DA 

4 5 6 0 0 1 8 7 AK,DA 

4 7 2 31 4 7 9 DA 

7 9 6 40 6 8 9 AK,DA 

2 8 5 52 4 7 9 DA 

7 11 2 2 2 3 8 8 AK,DA 

46272569DA 

4 8 4 5 0 4 7 11 AK,DA 

3 8 5 51 6 511 DA 

1413 50 0 611 AK,DA 

3 7 4 43 4 711 DA 

2 710 50 1711 AK,DA 

12 6 34 7 812 DA 

5 0 12 7 3 2 11 7 AK, DA 

3 5 6 53 413 9 DA 

5 3 6 6 2 6 11 9 K,DA 

4 9 6 75 110 8 DA 

7 8 7 2 1 2 14 8 AK,DA 

6 8 0 32 4 710 DA 

0 92 5 

0 98 7 

0 92 9 

0 97 10 

0 109 9 

0 113 9 

0 98 8 

1 90 10 

1 89 11 

1 119 11 

3 104 12 

4 84 12 

4 110 13 

3 94 14 

3 95 14 

5 99 13 

5 84 14 

5 66 15 

5 84 16 

8 101 17 

6 79 16 

5 86 16 

5 94 15 

4 95 18 

3 76 16 

3 86 17 

3 70 18 

0 82 18 

4 84 20 

4 75 18 

4 78 22 

5 87 20 

3 81 18 

2 86 22 

5 78 17 
NOAA Technlcal Memorandum NMFS 

This TM series is used lor documentation and timely mmunicahon of prellrn~nary results. lmtahn reputo. OT 

spacial purpose inlormation. and have not received complete formal renew. editorial control. 01 demled edlhng 

AUGUST 1984 

HAWAIIAN MONK SEAL POPULATION 

RESEARCHv LlSlANSKl ISLAND, 1982 

H. Sheridan Stone 

Southwest Fisheries Center Honolulu Laboratory 

National Marine Fisheries Service, NOAA 

Honolulu, Hawaii 968 12 

NOAA-TM-NMFS-S WFC- 4 7 

U.S. DEPARTMENT OF COMMERCE 

Malcolm Baldrige. Secretary 

National Oceanic and Atmospheric Administration 

John V. Byrne. Administrator 

National Marine Fisheries Service 

William G. Gordon, Assistant Adminlstratoi for Fisheries 

'Present address : National Marine Fisheries Service, Southwest 

Region, 300 South Ferry Street, Terminal Island, CA 90731 
TABLE OF CONTENTS 

Page 

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

Area and methods ........................... 1 

Area .............................. 1 

Population marking ........................ 3 

Age classification ...................... 3 

Marks and application .................... 5 

Markrecording . e e. e . . . . e e e e . e e . e 5 

Monitoring and maintenance of a marked population . . b e e . 6 

Census methods .......................... 6 

Observers .......................... 6 

Timeofcensuses ....................... 6 

Census procedure ....................... 6 

Sex and age classification on census ............. 7 

Seal identification on census ................ 7 

Molt status on census .................... 8 

Multiple sighting8 ...................... 8 

Results and discussion ........................ 8 

Results of field methodology: Individual level a e e e e e e e . e 8 

Marking ........................... 8 

Postmolt re-marking ..................... 10 

Tag resighta ......................... 10 

Census ........................... 11 

Age classification ..................... 11 

Results of mark and census effort: Population level . . e e e 22 

Population defined by haul-out observations . e e . e e e e e 22 

Population defined by molting seals ............. 22 

Applicability of combined population criteria ........ 26 

Molt ............................. 6 

Population structure .................... 27 

Reproduction ........................ 27 

Mortality factors ........................ 28 

Death or disappearance ................... 28 

Entanglement in nets and debris ............... 29 

Interieland movement ....................... 29 

.ummary ................................ 30 

Literaturecited ........................... 32 

Injury ....................... ... 29 

Acknowledgments ............................ 31 
ABSTRACT 

The absolute number of animale in the Hawaiian monk seal, Monachus 

schauinslandi, population at Lisianski Island was determined by identifying 

individuals on the basis of applied bleach symbols and natural marks, and 

conducting 98 island censuses from 17 March to 14 September, and 26 October 

to 22 November 1982. The extensive data base obtained by these marking and 

census methods should provide specific quantitative information that may be 

useful in the interpretation of future census and population data from 

islands used by Hawaiian monk seals. The alternate day censuses provided 

data on temporal and spatial haul-out patterns for individual seals. Data 

were collected daily on pupping, weaning, molting, and other factors that 

may influence haul-out patterns. Injuries and deaths were documented. 

In addition to 28 pups of the year, 215 seals consisting of the following were identified; 18 male and 10 female juveniles, 24 male and 21 female 

subadults, and 101 male and 41 female adults. Only two of these seals (an 

adult female and adult male) were known to have moved to Lisianski Island 

from other islands during the study. 

disappeared and is presumed dead. 

adult females with dorsal wounds, and a shark-injured adult male. 

Three pups died, and a subadult female 

There were three serious injuries: two 
INTRODUCTION 

Direct counts of the Hawaiian monk seal, Monachus schauinslandi, over 

the last two and a half decades have indicated changes in abundance at all 

major islands in the Northwestern Hawaiian Islands (Johnson et al. 1982). 

The overall population trend has been a marked decline, but the counts are 

only an index of relative abundance. Until the late 1970'~~ constraints of 

time and logistics prevented standardization of census methodology among 

years or atolls. Tagging and marking data have been valuable in estimating 

reproductive rates and intervals, and in better understanding interisland 

movement (Kenyon and Rice 1960; Wirtz 1968; Johnson and Kridler 1983). But 

little current information is available on age- or sex-specific survival, 

and there are few detailed data on individual haul-out probabilities by 

sex, age class, or season with which to adjust census data for missed 

seals. Interisland movement appears to be low (Johnson et al. 19821, but 

its exact influence on parameters at the population level is unknown, and 

just how open or closed the subpopulations are has not been determined. 

To obtain more precise information on Hawaiian monk seal population 

dynamics, studies were conducted on Lisianski Island from 17 March to 14 

September and 26 October to 22 November 1982. 

tion study are described in this report. 

conducted by the Southwest Fisheries Center Honolulu Laboratory, National 

Marine Fisheries Service (NMFS) researchers at Lisianski on pup tagging 

evaluation, association behavior, restraint and instrumentation of seals, 

diving and haul-out patterns, and entanglement in debris will be reported 

elsewhere. 

The findings of this populaOther studies simultaneously 

Population studies on Lisianski Island in 1982 centered on marking all 

seals that hauled out and conducting a long series of frequent censuses of 

the entire island. The objectives were to obtain data for evaluating 

various population estimators, obtain an absolute count as a reference for 

the estimation techniques, and document detailed haul-out patterns of 

individuals and factors that affect them. Accomplishing these objectives 

will lead to standardized methods that may be applied in future years on 

more islands to accurately estimate monk seal populations and precisely 

monitor trends. 

AREA AND METHODS 

Area 

Lisianski Island (lat. 26"02'N, long. 174"OO'W) in the Hawaiian 

Archipelago (Fig. 1) is the single island on Neva Shoal, a large reef bank 

described in detail by Clapp and Wirtz (1975). 

projections of coral are awash at low tide, but usable seal haul-out sites 

more than a few dozen meters off Lisianski, and thus unobserved on census, 

are considered negligible. 

shoreline there is mostly continuous vegetative cover. 

low vegetation often obscures seals hauled up beyond the beach for the 

night or during windy, rainy, or cool weather. 

A few very small offshore 

Several meters or more inland from the 

This usually dense, 

This vegetation also 
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provided cover at times for observers to minimize likelihood of seal 

disturbance, in general, and, in particular, to avoid affecting haul-out 

patterns. 

Lisianski is about 240 km southeast of Pearl and Hemes Reef, which 

It is about 215 km west of Laysan Island, which has a 

is composed of several islets and supports a small seal population (Johnson et al. 1982). 

seal population apparently greater than Lisianski's. These are the two 

monk seal populations nearest Lisianski. 

The island perimeter was divided into 49 sectors of varying length, 

delineated as much as possible by long-term natural landmarks (Fig. 2). 

Population Marking 

Age Classification 

A seal to be marked was assigned an age class, then assigned a twodigit (pup) or three digit symbol from a series for that class. Marking 

emphasis initially was on adult females, especially those apparently pregnant, then on immature seals before they began molting, and finally on 

adult males. 

Seals were classified directly into their "age group" based on known 

age (pups-of-the-year, nursing, or weaned) or reproductive state (adult 

females with pups), or indirectly based on an estimated "age class." 

latter classification included three groups: 

This 

Juvenile: Short, slight seals from the length of a weaned pup (about 

138 cm) to 20-30 cm longer. Immature seals including 

yearlings, and perhaps younger seals, up to perhaps 3 

years (Johnson and Johnson 1981a). Distinguished from 

pups by thinness and pelage color. 

tiated into J1 or 52, where 52 is larger. 

Sometimes differenSubadult: Seals perceptibly longer than juveniles up to breeding 

size; less robust than adults, generally with lighter 

pelage. Immature seals likely from 3 or 4 to 5 or 6 

years. 

Adult: Reproductively active or breeding size seals at least as 

long as known breeders. Mature or probably mature seals. 

Adult females often have extensive back scars or wounds; 

adult males usually dark, including venter, and extensively scarred. 

Aging was primarily based on estimated seal length, but girth, pelage 

appearance, scarring, and behavior were sometimes used secondarily. This 

assignment of marked seals to estimated age classes was based on reassessment over time and consensus among observers involved in taking censuses. 
4 

N 

Ll 

Figure 2.--Lisianski Island perimeter divided into 49 sectors. 
5 

Marks and Application 

Seals were considered marked when identifiable by one or more natural 

or applied marks that met minimum criteria of distinctiveness and conspicuousness. Before new marks were applied seals were carefully examined for 

any existing bleach marks and for scars and pelage patterns. As more seals 

were marked, the necessity of careful examination for previous marks 

(bleach or scars) became increasingly important to minimize chances of 

double marking. For a few seals, scars extensive enough to be visible 

regardless of how the seal lay were used as the sole identifying mark. 

Scar identification was also used temporarily for unbleached females with 

pups, because lactating females were never bleached while they had nursing 

pups to avoid disturbance. Both groups were bleach marked soon after 

weaning, and an effort was made to reidentify the known mothers from their 

scars when they returned ashore. Half of the 26 weaned pups in 1982, 

randomly chosen as the weaned, were also double tagged on the hind flippers with green Templeg tags. 

The seals were marked with Lady Clairol Ultra Blue or Clairolite hair 

lightener, mixed with developer, with varying success under differing 

conditions. Woolite red or blue sheep marking paint was also used, and both 

colors could provide conspicuous marks, though they remained so for only up 

to 3 weeks. The fluid was squeezed from a plastic bottle onto the most 

dorsal aspect reachable, without actually touching the sleeping seal. 

Bleaching anterior parts of the flank was avoided since seals readily 

scratched these areas with a foreflipper, and then often rubbed the mouth 

and eye region with the same flipper. A single transverse rump line was 

also applied, girdling as much of the dorsal and lateral pelvic region as 

possible. This was valuable in recognizing a seal as "marked" even if its 

identifying number was not visible. 

Mark Recording 

Marks were carefully sketched on a card for each seal, along with 

other scars and natural pelage marks. Behavior at time of marking such as 

rolling and smearing bleach or entering into the sea was recorded. Updating and amending these cards, and photographing marked seals, were continuing processes to maintain a current file of known seals. 

When first resighted, a new bleach mark on a seal was noted as to its 

contrast against surrounding pelage and its legibility as a unique mark. If 

necessary, rebleaching was done to protect census data reliability. This 

was important to maintain the validity of the assumption that all marks 

present were seen, or at least to keep violations of the assumption to as 

few as possible. 

2Reference to trade names does not imply endorsement by the National 

Marine Fisheries Service, NOAA. 
6 

Monitoring and Maintaining a Marked Population 

Behavior and events influencing seal haul-out patterns and survival 

were monitored daily and during censuses. Dates of pupping, weaning, molt 

period, appearance of fresh wounds, and death were collected on a daily 

basis. These events affect probability of sighting a specific seal during 

a specific census, as well as the correlation of sighting in consecutive 

censuses. 

Molt 

Seals were monitored at least daily through their molt to record start 

and finish dates, percent molted by increments of 5%, and movements around 

the island, as well as to rebleach them. When about 70% or more molted, 

approachable sleeping seals were rebleached to maintain identity. 

Census Methods 

Census procedures were designed to take advantage of an extensive 

field stay and intensive marking and census effort in 1982. At the same 

time, a protocol was designed that could be repeated on other islands in 

shorter visits, so comparative analyses among islands and years would be 

valid. 

Observers 

From two to six field biologists were present on Lisianski from 1.7 

March to 14 September and from 26 October to 22 November 1982. 

areas were divided between two, or when present, three observers--the same 

three people as long as they remained on the island. This continuity of 

census takers served to minimize census duration and increase or maintain 

accuracy of identification and consistency in age-classing seals. The 

experience developed was important in minimizing disturbance of seals, 

especially lactating females, while ensuring standard census protocol. 

Census 

Time of Censuses 

Complete island censuses were taken every second day except when this 

pattern was broken on four occasions. When this 2-day interval between 

censuses was increased to 3 or 4 days in these exceptions, a new alternating day schedule was started. Eighty-five censuses were taken during 

spring through summer, and 13 in autumn. All were sequentially numbered, 1 

through 98. Censuses began at 1300 Honolulu time, when the number of seals 

hauled out was near its highest (Kenyon and Rice 1959; Butler and Udvardy 

1966; Johnson and Johnson 1981b1, and took 1-1/2 to 2-1/2 h. 

Census Procedure 

Each observer walked one part of the shoreline. Observers exchanged 

sections for each census, but a particular area was almost always walked in 

the same direction. 
7 

Census takers with binoculars moved along the berm above the beach 

while looking and listening for seals that may have been in vegetation 

ahead or inland of the census route. All seals that were hauled out 

completely enough to be inspected for identifying marks in a given seetor, 

while the observer was in that sector, were recorded there. That is, seals 

in the water, or that hauled out after the observer moved through that 

sector, or that only briefly hauled out in a sector ahead were not formally 

counted. (For other purposes the occurrence and identity of some of these 

seals may have been recorded, such as documenting seals "using" the island 

a given day but missed on census.) 

Seals that swam by but did not haul out were ignored, since the 

probability of such a seal being counted only once could not be determined. 

Such a probability was dependent on that seal's swimming direction relative 

to the directions of converging or diverging observers. This potential 

census error was minimized in two ways. Censuses were taken in as brief a 

time as possible to avoid movement effects, and multiple resights of known 

seals in different sectors were documented. 

Sex and Age Classification on Census 

Each observed seal was recorded by age class on each census. This 

procedure was meant to precede and be independent of the identification 

process, since awareness of a known seal's assigned age (see marking section) would influence any estimate of age and prevent understanding of 

observer bias or error. Conversely, comparison of an independent estimate 

with the assigned age after identification helped standardize age-classing 

between observers and observations. A concentrated effort to standardize 

age-classing among observers was made at the start of the season. 

The sex of seals was categorically recorded only when actually determined, or if the sex of a positively identified seal was known. When 

appearance, behavior, or limited ventral view strongly indicated a seal's 

sex, that conjecture may have been noted on census if no confirmation was 

made after a wait of up to 15 min. 

Seal Identification on Census 

Identity of a seal was recorded when enough of a mark was seen to 

positively identify it and eliminate all others. 

rapidly became more reliable and easier for observers as they developed 

skill and confidence in discerning marks and familiarity with scar patterns 

and with mark appearance, location, and orientation on individuals. Up to 

15 min may have been spent waiting for a seal to expose an aspect or show a 

better mark. 

accordingly be longer. 

The identification process 

If a group of seals was being observed, waiting time could 

If for any reason a seal could not be carefully and completely 

observed, or a mark not sufficiently read, this was noted (e.g., "left 

flank unseen," "too sandy"), the presence of any mark recorded, and what 

was seen of the mark sketched when possible. Each sketch of scars or 

partly seen marks was later compared with cards on file documenting marked 
seals similar to the age and sex of the unidentified seal. Determination 

of two of the three figures in a bleach mark was almost always sufficient 

to allow positive identification. If, after this, identification was etill 

inconclusive, the sketch was saved for future checking as file cards were 

amended or for confirmation when that seal was reeighted. 

Molt Status on Census 

Molting seals were noted, and percentage of total body area molted was 

estimated in 5% increments. Observer agreement on molt estimates was found 

through regular comparisons to be consistently within 10-15%; thus overall 

differences were negligible. Degree of molt was often secondarily useful 

in identifying seals, and recording these data was part of a daily effort 

to monitor molting seals. 

Multiple Sightings 

Known resights of a seal on a given census were handled in one of two 

ways: 1) any seal that hauled out two or more times within full view of a 

census taker was recorded only once, and 2) seals resighted farther away from 

their first appearance were tallied in as many sectors as they appeared. 

This was assumed to be the best way to allow adjustment and valid 

application of Lisianski census results, either by deleting resights for 

accuracy of 1982 data, or including them to make the data more directly 

comparable with data sets in which few or no seals were marked. Through 

the early part of our season, as more seals were marked, the recorded 

prevalence of multiple counting8 was expected to increase proportionately. 

RESULTS AND DISCUSSION 

Results of Field Methodology: Individual Level 

Marking 

The number of monk seals older than pups identified by scars or artificial marks on Lisianski this season totaled 215. Table 1 shows the 

breakdown by sex and assigned age class, including one late season immigrant adult male (No. 166). 

All juvenile females were marked by 29 May, and all malee by 4 June. 

All subadult females were marked by 2 June, males by 8 June. The last 

adult female, before the arrival of No. 165 from Laysan on 22 July, was 

marked on 3 June. The first 91 adult males were marked by 8 June, the last 

10 from 17 June to 10 August, until the initial appearance of No. 166 on 4 

September. 

Application of unique, conspicuous marks to the pelage of a sleeping 

monk seal is practical and can be effective for all sex and age groups. 

Paint has short-term usefulness, since it persists dependably for only 3 

weeks or less, but its consistent viscosity often makes it easier and 

quicker to apply than bleach and may be of some use as a temporary, usually 

quite conspicuous mark. 
9 

Table 1.--Lisianski Island 1982 monk seal population, showing all seals 

marked including two mortalities, based on estimated midsummer ages. 

Sex ratio 

male to 

Male Female Total female 

10 28 1.8: 1 

21 45 1.2:l 

2.5: 1 

2 

Juvenile '18 

Subadult 24 

Adult 101 441 142 

Total 143 72 215 

3 

'Number assumes that No. 539 = No. 545. 

2Number includes a mortality (No. Sol). 

3Number includes an immigrant (No. 166) and a mortality (No. 114). 

4Number includes an immigrant (No. 165). 

Bleach of both types gave variable, but for most purposes acceptable 

results. Care and consistency in mixing and applying bleach and monitoring 

the bleaching action were necessary. Accurately sketching final appearance 

helped make bleach marks effective in reidentifying monk seals. 

lighting, seal orientation, and current pelage condition (e.g, worn, sandy, 

wet) frequently made it difficult to perceive and read marks. However, 

inspection of a seal from various angles by an experienced observer was 

usually sufficient to discern and read a mark in reasonable time. 

Angle of 

A seal was not considered to be in the marked population unless its 

mark was definitely resighted by at least two observers and judged of adequate conspicuousness, because of the variable, uncertain marking results. 

This requirement obviated two potential sources of inflated, cumulative 

population counts or inflated mark resight estimates. First, seals 

actually part of a "discrete" Lisianski population given a mark that did 

not persist would have increased the number of marks thought to be in the 

population, especially when later unknowingly given a different mark. 

Second, "transient" seals marked while only temporarily using Lisianski 

would also have inflated the number of marked seals calculated to be 

llsampled" during a census. Faintly bleached seals were considered marked 

only after they had been rebleached with a more conspicuous mark. 

With respect to implications of transience or interisland movement, 11 

of 26 numbers applied but never entered into the marked population as 

unique seals were later determined to be on seals bearing different conspicuous numbers. That is, the 11 were marked twice, but with different 

numbers. (Date of marking remained as assigned from this conspicuous 

number.) Six of the remaining 15 applied numbers that were unaccounted for 

were on seals known to have become wet within 10 min of application, and on 

another seal the bleach was immediately smeared by the seal's rolling. 
10 

None of the eight remaining seals (seven males and one female) bad conspicuous scars that would have been recognized on resigbting. In contrast, 

there was no failure to resight a seal that had good diagnostic scars when 

marked. As discussed earlier, there is other circumstantial evidence to 

indicate these and other bleach marks were not placed on transient seals, 

i.e., seals returning to some other atoll subpopulation. 

Postmo It Re-Marking 

Each of 215 seals marked at Lisianski was first so identified before 

its molt. All but two of these were correctly rebleached either in the 

summer by following seals through molt or on our return in October with the 

aid of sketches and photographs. The exceptions were two small juvenile 

males, including one (513) that was not identified and most likely was 

never seen during October to November. 

was seen during the week before our departure in mid-September suggested he 

was probably about to begin the premolt "fast," or the period spent on or 

close to shore, a phase displayed by nearly all other molters. The other 

male (539) was bleach marked but not resighted after the mark was confirmed 

on 18 May. Although it was not conspicuously scarred, 539 matched the 

small size and sex of a molted juvenile male frequently seen in October and 

bleached with a new number, 545 (i.e., 539 and 545 may be the same animal). 

The frequency with which this seal 

All seals sighted in the autumn were either marked or, by 3 November, 

reidentified as known or probably known and then rebleached. Implications 

of these marking results at the population level are discussed later. 

Tag Resights 

Twelve pups tagged in 1982 still Rad both tags when last seen, which 

was September for one pup (023) and November for all others. 

lost a single tag early in the season, and was retagged, 

One pup (025) 

Two adult females bore single Monel metal tags placed on them at 

Lisianski earlier. Seal A1011 (bleach marked A771 was tagged as a pup in 

1971. Seal A86 (bleach marked 131) was tagged as a yearling in 1968. No 

other Lisianski seals were observed with metal tags. 

A subadult male that grew to a large subadult or small adult this 

season was identified from a large conspicuous net scar on his neck. 

constricting net was cut off in the spring of 1980 when the male was 

classed as a juvenile (Gilmartin'). 

The 

It was photographed gain on Lisianski during an island survey the spring of 1981 (Shallenberger f 1. 

3W. G. Gilmartin, Southwest Fisheries Center Honolulu Laboratory, 

National Marine Fisheries Service, NOAA, P. 0. Box 3830, Honolulu, HI 

96812 pers. commun., July 1982. 

the Interior, P. 0. Rox 50167, Honolulu, HI 96850, pers. commun., December 

1982. 

4R. J. Shallenberger, U.S. Fish and Wildlife Service, Department of 
Census 

The frequency of alternate day censuses from March to September and in 

November seemed an adequate sampling of seal haul-out activity to represent 

individual patterns (Table 2). Although the number of seals on shore 

reached a maximum by about noon, experience showed that not all seals 

"using" the island on a specific census day were ashore, or at least 

counted, in that census period, Some seals sighted the previous night or 

seen in early morning had entered the sea by mid to late morning. Three 

adult females were known to have done this on several census days. Other 

individuals not counted on census sometimes hauled up in late afternoon. 

These included a few molting animals. Occasionally some individuals swimming nearshore were identified but not seen hauled out during that census 

or day, or seals known to be molting were not seen ashore that day. 

fore, a single census should not be considered as a total count of all 

seals or known individuals hauling out that day. 

sex, or age biases in census data may exist due to this, though they are 

not understood. 

the long census series and contribute little to more identifiable sex and 

age related differences in haul-out frequency or duration. Conversely, 

documentation of multiple resights on censuses showed that almost all were 

adult males apparently engaged in searching beaches for mating purposes. 

ThereSome individual seal, 

However, any such biases are assumed to be negligible over 

As the proportion of the seal population marked steadily increased, 

observer expertise in detecting and reading marks also increased. Bleach 

marks on new pelage usually gave better contrast than those on premolt 

pelage. Thus, later censuses are most complete and detailed. 

On the average only 82 (38%) of the 215 known seals were present during 

any single spring and summer census. Census counts, excluding weaned and 

nursing pups, ranged from 58 to 108 (X = 82.0) for the 85 censuses 17 March 

to 12 September; including pups it ranged from 75 to 120 (X = 97.5). The 13 

counts for October-November averaged lower, ranging from 60 to 81 (Z = 68.8) 

excluding pups, and 69 to 95 (Z = 81.8) including pups. The autumn counts 

were lower because the seals are generally not present on Lisianski for 

reproductive activities or molting that time of year. 

Age Classification 

The preferred sequence of age estimation of a seal in census before 

identification and recognition of that seal's assigned age class was not 

always possible to maintain. 

census series, independence of these two events was complete enough to 

provide a good record of any observer biases or errors. 

But over a census and especially over the 

Four biases or errors in age classification were considered possible. 

Any such 

Interobserver differences could result from an observer consistently classing specific seals older or younger than another observer might. 

bias would have been constant. Midseason changes of one observer could 

have led to similar biases. Intraobserver inconsistency, or fluctuations 

in classifying the age of a specificasize of seal either among observations 

on a census or among censuses, would have caused errors rather than a 
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21 

constant bias. Intraobserver drift, an 

ence sizes for an age class, would also 

single direction. 

upward or downward trend in referhave led to errors, though in a 

These factors could be important in three ways. First, in interpretSources of potening any discernible seasonal change in age distribution of seals counted, 

any artifacts of observer variation must be discounted. 

tial variation included initial intraobserver adjustment and standardization efforts in early spring and a mostly unmarked population early on that 

gave little feedback toward aging consistency. Inconsistent aging initially would have implied fluctuations in age composition that were not 

real and "floating" sizes of each age class being sampled. This latter 

process would make questionable any comparison between early season censuses and later ones, when age class size was more fixed, as well as any 

mark resight estimates dependent on having "closed," or fixed, sex and age 

classes. 

Secondly, an increase in the independent age estimate of a known seal 

at some period in the season, from consistently in one class to consistently 

in the next greater, is an index of growth in that seal. If that is determined not to be part of a trend due to observer drift, then it may indicate 

a real change in age group structure. If growth from one age class to 

another over the season was found to be common enough, it must be considered 

in analyzing seasonal changes in age distribution among censuses. 

Finally, awareness of interobserver differences is useful in direct 

comparisons of census and age composition data from other observers at other 

islands and years. 

The concerted initial effort to develop and standardize age classification among all observers was continued until there was general understanding of criteria used and close agreement in aging. Concentration on this 

process quickly yielded consistent classification of age early in the census series. Spot comparison of independent age estimates among observers 

helped maintain this standardization. 

independent estimates on known seals with previously assigned ages also 

helped reinforce the procedure and reduce any tendency toward observer 

drift. 

On site intraobserver comparisons of 

No persistent biases in census taking were identified. The most 

common sources of any error seemed to be uncontrollable factors that would 

be encountered by and influence all observers, such as a seal being wet or 

lying in an unusual orientation, age estimates having to be made at a 

greater distance than usual, and adjusting aging criteria and estimates for 

postmolt seals to account for weight loss and pelage change. Therefore, 

I conclude, provisionally, that analyses of census data and comparisons 

among seals, groups, and seasons were not seriously influenced by obeerver 

variation. 
22 

Results of Mark and Census Effort: Population Level 

The 215 seals marked at Lisianski constitute a discrete, almost closed 

population or subpopulation, within the Northwestern Hawaiian Islands. An 

absolute count was accumulated through individually marking all seals 

before molt and documented by continuing census procedures and effort to 

collect haul-out data and maintain a totally marked population, Table 2 

shows sighting8 by census of individually marked seals including pups, 

grouped by sex and age class as classed at midsummer. Events observed on 

censuses such as marking, birth, weaning, death or disappearance, and molt 

are indicated. Table 3 lists totals by census for each sex and age category recorded. Two definitions of this population are discussed, one 

indirect and circumstantial, the other concise but less widely applicable, 

for two different purposes. 

Population Defined by Haul-Out Observations 

That all seals and only those seals that haul out with some minimum 

frequency on Lisianski define the population, and that a11 such seals were 

marked, and therefore the entire population was marked, is circular reasoning. The implicit assumption is that all seals in the population (such as 

those utilizing resources on Neva Shoal or contributing to reproduction) do 

haul out on land with some regularity. 

Fortunately, this tautology in practice seems applicable, and the 

assumptions valid. There is no evidence that any seals using local waters 

do not haul out, and virtually all available haul-out sites at Lisianski 

were readily visible. All marked seals were known to haul out before or 

after molt at times unassociated with this process, which appears to be the 

only obligatory haul-out time other than pupping. 

be marked in midsummer were frequently resighted thereafter. So their 

sequence of marking is not necessarily correlated with a low haul-out 

probability, and no link between bleach marking and increased haul-out 

frequency is known. Therefore, all seals resident in the waters around an 

atoll can be expected to haul out frequently enough to be marked, i.e., at 

least twice. What must be determined from census results is the best time 

and necessary length of field stay to accumulate and document population 

data with acceptable confidence and precision. 

Even the last seals to 

Population Defined By Molting Seals 

A biologically concise definition of the Lisianski population in 1982 

is those seals that molted there, plus seals known to have died before 

molting. All seals molt annually, spending much or all of that time 

ashore. All molting or recently molted seals were marked, and thus the 

entire population was marked. 

year, but is probably not applicable to other years. 

This definition can be justified for this 

All known resident seals (except for one that cannot be documented) 

molted between mid-April and early November, within the overall dates of 

our extended field season. Presumably, any seal actually resident in that 

population would have molted within this period. Individual molt periods 
23 

Table 3 .--Summary of Lisianski Island monk seal censuses, 1982 

(M = male, F = female, 7 = sex unknown). 

Pupe 

Adult Subadu 1 t JuveniP e Tot a1 Weaned Nursing Total 

Date no including 

Census 1982 M F ? M F ? M F ? pups MF?MF? PUPS 

1 3/19 22 14 18 3 1 7 6 3 4 78 -- -- -- I17 87 

2 3/23 30 14 12 2 6 4 3 5 4 80 2 -- -- 215 90 

3 3/25 24 12 4 4 1 8 -- 3 2 58 3 2 -- 6 69 -- -- 

4 3/27 31 17 11 7 5 5 4 2 1 83 4 -- -- 323 95 

5 3/29 24 14 24 6 3 6 2 2 1 82 4 -- -- 222 92 

6 

7 

9 

10 

a 

3318 7 5 2 3 6 5 3 82 

251411 9 4 5 2 3 5 78 

351811 2 6 8 5 3 4 92 

3611 9 4 7 6 6 4 3 86 

3215 6 7 4 7 5 3 4 83 

5 1 -- 4 3 -- 

5 -- -- 3 3 -- 

5 2 -- 4 2 -- 

3 1 -- 4 2 -- 

4 2 -- 4 2 -- 

95 

89 

105 

96 

95 

4/10 

4/10 

4/14 

4/17 

4/19 

11 

12 

13 

14 

15 

311414 5 2 7 3 3 1 80 

3320 411 4 2 6 3 1 84 

221610 7 7 4 4 12 73 

3217 8 9 4 4 2 2 2 80 

3819 7 4 2 4 3 3 1 81 

5 2 -- 4 1 -- 

5 3 -- 5 1 -- 

5 3 -- 5 2 -- 

5 3 --* 5 2 -- 

5 2 -- 4 2.-- 

92 

98 

88 

95 

94 

16 

17 

19 

20 

ia 

4/21 

4/23 

4/25 

4/27 

4/29 

291411 7 2 6 5 2 1 76 

2420 7 6 611 5 3 1 83 

2919 8 14 4 6 2-- 73 

2918 8 7 5 19 3 2 82 

2618 6 5 9 4 3 2 P 74 

7 3 -- 4 3 -- 

4 4 -- 

5 3 -- 3 4 -- 

6 2 -- 4 4 -- 

5 2 -- 4 4 -- 

6 -- -- 

93 

97 

88 

96 

89 

21 

22 

23 

24 

25 

3320 9 7 3 15-- 1 79 

3518 7 8 5 2 3 6-- 84 

31 19 6 13 4 2 6 2 -- 83 

221420 4 8 2 3 3 1 77 

28 21 15 4 6 2 7 2 -- 85 

9 3 -- 3 3 -- 

9 3 -- 3 5 -- 

9 3 -- 3 4 -- 

8 4 -- 3 4 -- 

9 4 -- 4 4 -- 

97 

104 

102 

96 

106 

26 

27 

28 

29 

30 

5/11 

5/14 

5/16 

5/18 

5/20 

242015 9 5 2 2 2 1 80 

26 15 14 6 4 -- 2.2 1 70 

31 21 9 11 3 5 5 2 -- 87 

33 21 5 10 6 -- 5 7 -- 87 

34 17 5 8 3 -- 4 4 -- 75 

9 3 -- 5 4 -- 

8 2 -- 5 3 -- 

7 4 -- 5 3 -- 

7 5 -- 5 4 -- 

8 4 -- 6 3 -- 

99 

88 

106 

108 

96 

31 

32 

33 

34 

35 

5/22 

5/24 

5/26 

5/28 

5/30 

26 17 1 7 4 -- 4 5 -- 64 

31 18 4 8 7 -- 7 4 -- 79 

41 17 5 10 10 -- 2 2 -- 87 

36 20 3 13 11 -- 9 5 -- 97 

43 24 -- 12 10 -- 9 4 -- 102 

8 5 15 4-- 

9 4 -- 5 4 -- 

9 6 -- 5 3 -- 

8 6 -- 4 3 -- 

8 6 -- 4 3 -- 

87 

101 

110 

118 

123 
24 

Table 3 .--Continued. 

Pups 

Adu 1 t Subadult Juvenile Total Weaned Nursing Total 

Date -- no including 

Census 1982 M F ? M F ? M F ? pups MF?MF? PUPS 

36 

37 

38 

39 

40 

41 21 -- 12 9 -- 6 4 -- 93 

32 21 -- 13 9 -- 7 3 -- 85 

31 20 1 10 10 -- 4 4 -- 80 

36 19 -- 15 12 -- 7 5 -- 94 

29 17 -- lo lo -- 7 4 -- 77 

7 6 -- 4 4 -- 114 

8 6 -- 4 4 -- 107 

9 7 -- 1 3 -- 100 

8 8 -- 3 2 -- 115 

lo 7 -- 3 2 -- 99 

41 

42 

43 

44 

45 

6/12 

6/14 

6/16 

6/18 

6/ 20 

27 19 -- 12 lo -- 7 5 -- 80 

40 18 -- 14 10 -- 8 4 -- 94 

35 16 -- 11 9 -- 8 4 -- 83 

27 20 -- 8 10 -- 7 5 -- 77 

29 18 -- 11 lo -- 8 6 -- 82 

8 8 -- 3 2 -- 101 

9 7 -- 3 2 -- 115 

9 7 -- 3 2 -- 104 

9 6 -- 2 1 -- 95 

7 7 -- 1 2 -- 99 

46 

47 

48 

49 

50 

6/22 

6/24 

6/26 

6/28 

712 

34 16 -- 7 13 -- 3 4 -- 77 

22 20 -- 8 13 -- 5 3 -- 71 

26 15 -- 10 13 -- 5 3 -- 72 

23 24 -- 10 13 -- 7 2 -- 79 

27 19 -- 9 11 -- 8 2 -- 76 

9 6 -- 1 3 -- 96 

8 6 -- 1 3 -- 89 

3 -- 90 

3 -- 96 g 5 -- -- 

2 -- 93 

9 6 -- -- 

9 6 -- -- 

51 

52 

53 

54 

55 

714 25 15 -- 9 18 -- 4 2 -- 65 

716 23 14 -- 10 14 -- 6 5 -- 72 

718 32 23 -- 13 13 1 6 3 -- 91 

7/10 32 14 -- lo lo -- 5 6 -- 77 

7/12 32 12 -- 12 13 -- 3 4 -- 76 

83 

90 

106 

92 

90 

56 

57 

58 

59 

60 

7/14 25 14 -- 8 10 -- 5 4 -- 66 

7/18 24 13 -- 11 lo -- 5 3 -- 66 

7/20 41 14 -- 10 6 -- 4 1 -- 76 

71 

7/16 33 14 -- 11 8 -- 3 5 -- 74 

7/22 33 15 1 13 4 -- 5 -- -- 

11 7 -- -- 1 -- 

10 6 -- -- 1 -- 

8 6 -- -- 1 -- 

7 8 -- -- 1 -- 

1 -- 7 7 -- -- 

85 

91 

81 

92 

86 

61 

52 

63 

64 

65 

7/24 29 12 -- 10 6 -- 4 2 -- 63 

69 

68 

7/30 39 11 -- 8 4 18 1-- 72 

811 38 14 -- 9 3 -- 5 1 -- 70 

7/26 32 12 -- 11 7 -- 7 -- -- 

7/28 39 11 -- 9 3 -- 6 -_ -- 

75 

84 

82 

90 

79 

813 39 17 -- 7 8 -- 4 3 -- 78 

8/5 54 15 -- 8 6 -- 10 2 -- 95 

817 51 9 -- 8 4 -- 6 5 -- 83 

819 52 10 -- 10 8 -- 7 2 -- 89 

8/11 56 13 -- lo 2 -- 6 3 -- 90 

66 

67 

68 

69 

70 

89 

107 

95 

103 

100 
25 

Table 3 .--Continued. 

Adult Subadult Juvenile Total Weaned Nursing Total 

Date no including 

Census 1982 M F ? M F ? M F ? pups MF?MF? PUPS 

71 8/13 

72 8/15 

73 8/ 17 

74 8/19 

75 8/21 

58 4 

62 10 

61 8 

62 12 

70 12 

83 

96 

43 

31 

54 

34 

53 

32 

24 

63 

80 

95 

81 

84 

100 

94 

105 

90 

96 

111 

76 8/ 23 

77 8/25 

78 8/27 

79 8/31 

80 9/2 

65 12 

66 10 

68 6 

66 10 

69 9 

62 

66 

82 

86 

75 

32 

41 

35 

51 

92 

90 

93 

92 

96 

101 

1 04 

104 

103 

1 06 

110 

81 9/4 

82 9/6 

83 9/8 

84 9/10 

85 9/12 

69 12 

65 11 

66 9 

72 8 

63 7 

56 

85 

64 

97 

84 

54 

95 

93 

84 

10 2 

92 

103 

97 

108 

94 

104 

115 

111 

120 

101 

86 10/27 

87 10/29 

88 10/31 

89 11/2 

90 11/4 

27 12 

39 9 

36 9 

38 13 

46 8 

56 

86 

79 

76 

97 

73 

95 

10 8 

73 

92 

60 

76 

79 

74 

81 

69 

89 

95 

89 

94 

91 11/6 

92 11/8 

93 11/10 

94 11/12 

95 11/14 

38 7 

36 10 

29 8 

31 9 

25 7 

84 

65 

11 8 

99 

79 

61 

52 

11 5 

44 

53 

65 

67 

73 

68 

61 

80 

81 

88 

78 

72 

72 

78 

78 

57 -------- 

47 -------- 

96 11/16 35 5 -- 4 5 -- 6 3 -- 60 

97 11/18 32 7 -- 9 5 -- 8 1 -- 63 

98 11/19 31 11 -- 7 lo -- 6 1 -- 67 

6 9 ..- -- -- -- 
26 

were usually well defined, and ranged from as little as 5 or 6 days, to 12 

days, and occasionally longer. All marked seals molting during our actual 

presence were seen molting on several or more days. 

during our presence to have gone unmarked was extremely unlikely. 

For any seal molting 

Fourteen marked seals were not seen molting, either before 14 September or after 25 October. 

during our absence. Twelve were definitely reidentified after they molted, 

and one equivocally (545 may equal 539). 

close to molting when we left in September. All unbleached seals seen on 

our return in October-November could be accounted for from these 14. 

All of these molted presumably on Lisianski 

The last (513) may have been 

Each seal marked in 1982 was generally marked at least a week before 

its molt. Thus molting apparently did not cause seals that rarely hauled 

out otherwise to come ashore. Postrnolt seals of all groups were commonly 

seen; there were few or no immediate and prolonged returns to sea. That an 

unknown seal would have hauled out, undergone a week or more of premolt 

"fast" characteristic of most seals, molted for 8 days or more, returned to 

sea, all between 13 September and 26 October, and not be identified by 22 

November, seems unlikely. Thus all evidence indicates that all resident 

seals molted at Lisianski and that all were marked. 

Applicability of Combined Population Criteria 

The molt criterion discussed above cannot be consistently applied for 

defining island subpopulations in future years. Molting seals have been 

sighted in every month (Gilmartin footnote 3) and seasonal distribution of 

molt in the different sex and age groups can vary from island to island. 

Field seasons will most likely not last as long as this year's extended 

coverage on Lisianski, much less for complete years. But since molt distribution of the population fell within our field dates this year, this 

criterion is verification that a totally marked population based on timespecific haul-out patterns can be accumulated. In future seasons, seals 

that are seen to molt can be used as a sample of their sex and age group. 

If marking a seal can be documented as temporally independent of molt, and 

if all those seals starting molt are known sealss these representative 

samples can be a good indicator that most or all of their particular sex 

and age groups have been marked. 

Finally, the one or two apparent exceptions to these criteria for 

defining and counting a population actually clarify the definitions while 

showing their limitations. These exceptions are the two documented 

incidents of immigration, more fully discussed under interisland movement 

later. Adult female 165, the last female marked, almost certainly was seen 

and marked on her first appearance at Lisianski on 22 July. Her haul-out 

probability before was virtually zero because she was known to be lactating 

on Laysan much of that time. She was recognized only because a biologist 

on Laysan had sketched and photographed her extensive scars. Otherwise, 

her long prior absence would have severely weakened an assumption of similar haul-out probability and likelihood of marking. Thus, although seal 

165 molted on Lisianski (and appeared to undergo estrus there), and by this 

criterion was considered part of the Lisianski population, we know merely 
27 

by chance that she contributed reproductively to the Laysan population in 

1982. And, therefore, potential limitations in defining populations due to 

interisland movement are demonstrated, as is the potential importance of 

this phenomenon generally. 

Adult male No. 166, the last male marked, possessed several distinctive scars and natural light pelage spots and was very likely identified 

the first time it hauled out on 4 September at Lisianski. This situation 

also could necessitate consideration of greater haul-out probabilities in 

identifying all seals in a subpopulation or in documenting an estimate. 

That seal 166 is not in the resident population may seem a semantic argument and a way to fit seals into formal definitions, but the biological 

aspects are important. He was emaciated and possessed barnacles and dense 

algal growth in his pelage, indicating he had been at sea a long time, 

apparently without feeding much on Neva Shoal, or elsewhere. 

only unmolted seal on Lisianski by 22 November, and this delay, as well as 

perhaps his inclination to remain near Lisianski from early September 

through November, may have depended directly on his nutrition or health. 

He first appeared after all breeding for the year seemed long over, and his 

functional residence in the Lisianski population can best be determined in 

future seasons from resight data. 

He was the 

Population Structure 

Table 1 shows the monk seal population at Lisianski in 1982 (less pups) 

by sex and age. 

turity to adulthood even if juveniles and subadults are pooled to increase 

sample size and minimize aging discrepancies. 

effects of this skewed ratio in favor of males are fully understood. 

The ratio of males to females increases greatly from imaNeither the causes nor the 

Reproduction 

At least 28 pups were born in 1982: 16 males, 11 females, and 1 of 

undetermined sex. The sex of the latter could not be determined because it 

was found as a deteriorated carcass with remnants of black natal pelage in 

March. The mother (A201 had sustained 

a large, deep back wound, of the type known to be inflicted by adult malee, 

about 1 or 2 weeks before parturition. Twenty-two of the mothers were 

known, but two females that weaned pups a few days after our arrival were 

never successfully reidentified from scars sketched before they left. One 

of the two tagged females (No. 131, tag No. A861 pupped this year and in 

1980; the other (No. A77, tag No. A10111 did not pup in this 1982 season. 

Assuming the 40 classified adult females (excluding No. 165) constituted 

the actual adult female group this pupping season, at least 70% pupped, and 

65% (26) weaned. 

1964 and 1965 from 78 tagged adult females on Kure Atoll (Wirtz 1968). 

There, only 44 (56%) pupped in that 2-year period. On Laysan Island, 56 

identifiable adult females were seen in 1977, when 55% pupped, and 1978, 

when 50% pupped (Johnson and Johnson 1981b); 79% pupped in that 2-year 

period. 

tion of females. But size differences between females classed a8 adult and 

subadult on Liaianski seemed consistently clear-cut. If anything, the 

One male pup died at or near birth. 

This pupping rate is high compared with about 38% for 

Part of the variation may be due to difference in age classifica- 
28 

inclusion as adult of two females (A18 and SO51 that seemed slightly 

smaller than most parturient females would underestimate the pupping rate 

if these two were not sexually mature or were just maturing but nonparous. 

Identification of parturient females in 1983 on Lisianski should give a 

more complete estimate of definitely mature females from which to calculate 

productivity rates. 

Mortality Factors 

Death or Disappearance 

Besides the two perinatal deaths, three other deaths and a possible 

disappearance were documented. Male pup 021 was killed 19 June, most 

likely by one or more adult males, since D male was attending the carcass 

in the surf of a small cove where males were observed pursuing pups at 

other times. No gross external nor any gross internal injuries were 

present. 

Male pup 023, one of the three oldest pups, was last seen 8 September 

when about 7 months old. From 26 October through 22 November, in addition 

to censuses, daily tallies were made of all marked seals seen, thus undoubtedly he was absent this entire period. Several other small juveniles were 

absent longer than this at various times. Some such juveniles could well 

have been less than a year old, since births have been recorded in every 

month (Gilmartin footnote 3) and 5- to 6-month-old pups were increasingly 

classified as juveniles on census. 

occasionally not sighted for 3 to 4 weeks, albeit on a less frequent census 

schedule (Johnson and Johnson 1981b). 

Om Laysan, 4- to 7-month-old pups were 

Most of the skin and much of the blubber from the back of subadult 

female SO1 were missing when she was first seen 21 March. 

ically seen ashore until 17 April, and the wound looked much the same. 

disappeared and probably died because of her severe wound and emaciated 

condition. 

She was periodShe 

The cause is most likely attributable to biting by adult males. 

The two lactating females (originally A02 and A131 whose scars were 

sketched but who were not reidentified after weaning are assumed to have 

been marked with another number rather than to have disappeared. 

it is at least plausible that postweaning estrus instigated wounding by 

adult males (Johnson and Johnson 1981b). This could have contributed, 

along with postlactating emaciation, to death or to greater susceptibility 

to shark predation. 

after being marked this season, and twice, several males were seen nearshore vigorously pursuing or biting another adult--at least one, a female. 

A fourth female had a healing but still open wound when first identified in 

March, and two more still had small healing spots in the middle of large 

dorsal scars. 

received them before pupping this year. 

However, 

Three adult females received large, open back wounds 

Two of these four females that had open wounds actually 

Adult male 114 died on 13 July after being physically restrained 

for attachment of a dive recorder. Necropsy showed no obvious cause of 

death, but microscopic histopathology revealed several chronic ailments 
debilitating the seal. 

sively worn or broken, but longitudinal sectioning (Hofman 1975) of these 

revealed no countable laminae. 

Two of the 10 foreflipper nails were not excesIn jury 

Evidence of shark attack was also seen. A healthy appearing adult 

male (A951 when marked, sustained severe shark bites on the right fore and 

hind flippers and pelvic region in early summer. He lost enough weight 

that ribs and vertebrae were clearly visible at later resights, then slowly 

began regaining weight and healing by midsummer. In late October, he had 

sloughed some injured hind flipper tissue and exposed phalangeal bone and 

was still healing. Seal A95 was one of the last three adult males molting 

then. At least three other adult males bore scars suggesting prior wounds 

at least this severe. But no immature seals had large, obvious shark 

inflicted scars, implying these smaller seals do not readily escape and 

recover from shark attack (Wirtz 1968). 

Entanglement in Nets and Debris 

A final documented cause of potential death this season was fishing 

Four weaned pups this year (Henderson 1984) were cut 

The subadult male (S21) with the 

gear entanglement. 

from tightly encircling masses of net. 

recognizable neck scar had been found as a juvenile with tightly encircling 

line and a deep, septic neck wound. No adults had identifiable net scars, 

nor any subadults but the one above. 

entangle themselves and usually do not survive (Fiscus et al. 1978; Andre 

and Ittner 1980). 

Apparently younger seals tend to 

A juvenile female (522) had a transverse scar across the bridge of the 

nose possibly due to entanglement. Another pup had a plastic band tightly 

stuck on her snout that we pulled off, and at least four other small seals 

had a plastic ring, bucket, or shredded bag loosely and temporarily aroupd 

their necks. So, fishing gear is not the only debris that is a problem 

source. This curiosity and attraction to lost or discarded nets, lines, 

and other debris, on land and in water were commonly observed, most often 

among immature seals (cf. Fiscus et al. 1978). These anecdotal observations suggest that entanglement can be a frequent and fatal problem that 

may be selective for young seals. 

Interisland Movement 

Only two movements to Lisianski were documented this season, and no 

emigration was documented. A large, extensively scarred female first 

appeared 22 July and was identified by sketches and photographs taken at 

Laysan Island. This seal (No. 165) had weaned a pup on Laysan in late June 

this year. Once at Lisianski, she continued to haul out periodically and 

went through apparent estrus when she was attended by an adult male. She 

molted there and was rebleached, and was then resighted several times 

through November. 
30 

On 4 September, an emaciated adult male (No. 166) with distinctive 

natural pelage marks and scars appeared ashore. 

with algae, and seven live gooseneck barnacles, Lepas spp., ranging in 

estimated capitulum length from a few millimeters to a centimeter, were 

attached to his dorsal pelvic hair, indicating a long period at sea. Johnson and Johnson (1978) described three such observations of barnacles. 

They noted an adult male on Laysan in 1977 that returned from a 4-month 

absence with gooseneck barnacles on his pelage. 

from the Laysan seal after 2 days ashore, and from No. 166 after a similar 

period. An adult female, not seen on Laysan from 6 June to 9 August 1977, 

reappeared with all parts of the body covered with barnacles, which disappeared 6 days after resighting. 

male was seen at Mar0 Reef with barnacles on the head and neck (Coleman5). 

Seal No. 166 had not been seen before on Lisianski in 1982, but thereafter 

including November was commonly seen. He regained weight but did not molt, 

and molt did not appear imminent by 12 November. Recognition of these two 

seals (No. 165 and No. 166) in a future season will further clarify subpopulation discreteness and age specific tendencies to move. 

His pelage was quite green 

The barnacles were gone 

And in mid-August an adult thought to be a 

Lack of evidence for more extensive interisland movement during this 

1982 field season was apparent. Researchers on Eaysan from March through 

June did not see any marked seals from Lisianski. From 29 April to l1 May, 

2-6 July, and 27-31 October no marked seals from Lisianski were seen at 

Pearl and Hermes Reef. Conversely, although at least 37 different seals 

were marked on Pearl and Hermes Reef during these visits, and some probably 

re-marked after molting, no marked seals from there were seen at Lisianski. 

Some bleach marks were not seen in their entirety and therefore could not 

be read, but it is extremely unlikely that any of these were on seals from 

Pearl and Hermes Reef and were not seen again later and fully identified. 

Seal censuses were also being regularly carried out at French Frigate 

Shoals, and some bleaching was done and censuses taken at Kure Atoll simultaneously with most of our field season. Again, no interisland movement 

was documented through these activities. 

The subpopulations may then be discrete by short-term measures even 

though seals from Lisianski were frequently at sea long enough to move to 

and from other atolls or banks. Understanding the role of interisland 

movement would be valuable in short-term population marking and estimation, 

and in long-term investigation of dispersal and population trends or shifts 

of the entire species. 

SUMMARY 

The Hawaiian monk seal population utilizing Lisianski Island was 

counted and studied by marking seals and taking complete island censuses 

5 R. Coleman, U.S. Fish and Wildlife Service, Honolulu, notation from 

cruise log, Mar0 Reef, 6 August 1977. 
31 

from 17 March to 14 September and 26 October to 22 November 1982. 

used and preliminary results obtained included: 

Methods 

1. 

2. 

3. 

4. 

5. 

60 

Individually marking sleeping seals using commercial bleach, plus 

some reliance on natural scars and marks, is a feasible technique 

for identifying all sex and age classes. This method provides 

little risk of disturbing the seals. During lactation females and 

pups were not bleached, to avoid any such risk. 

Two hundred fifteen monk seals other than recent pups were 

marked, sexed and subjectively classified by age as juvenile (18 

males and 10 females), subadult (24 males and 21 females), and 

adult (101 males and 41 females). 

female that moved from Laysan Island and one male that very 

likely moved from another unknown island. 

"resident" and perhaps almost discrete population in terms of 

population dynamics was defined. 

The adults included one parous 

Thus for 1 year a 

At least 28 pups were produced by 40 adult females, and 26 

weaned. 

reported rates of monk seals at other islands. 

This 70% reproductive rate is very high compared with 

Natural deaths included two pups that died near birth, a weaned pup 

apparently killed by an adult male, and a subadult female with a 

severe back wound probably inflicted by adult males. 

wounds were observed on several adult females including a high 

proportion of extensive, healed, dorsal scars. One adult male died 

after human restraint and was found to have,been chronically ill. 

Similar back 

Besides deaths due to adult male aggression, perhaps related to the 

very skewed sex ratio, entanglement in fishing net and debris was 

observed to be a potential cause of death particularly among young 

seals, including a significant proportion of weaned pups. Data on 

shark wounding indicated that they also may cause deaths particularly among young seals. 

The series of every second day censuses provided extensive, 

detailed records on individually known seals. Analyses of these 

data should provide insight into sex-, age-, and seaeon-specific 

baul-out patterns and sighting probabilities, as well as any 

influence on these patterns, of such biological events as reproduction, molting, and injury. 

useful as a basis for understanding population discreteness and 

interisland migration, planning and conducting future population 

assessments at other islands, and monitoring trends in population 

eize, structure, and productivity. 

This quantitative information may be 

ACKNOWLEDGMENTS 

The U.8 Pirb and Wildlife Service personnel, especially John,Andre and 

other8 on Tern Island provided a continual, essential communication link. 
32 

Capt. Edward Shallenberger of the FV Feresa and Capt. R. Dahleen of the RV 

Easy Rider, and their crews gave energetic close support of field operations 

and insight into the history of recent activity in the Northwestern Hawaiian 

Islands. Clark Winchell and Don Siniff, University of Minnesota, critically 

reviewed drafts of the manuscript, 

LITERATURE CITED 

Andre, J. B., and R. Ittner. 

1980. Hawaiian monk seal entangled in fishing net. 'Elepaio 

41(6) :51 . Butler, G. D. and M. D. F. Udvardy. 

1966. Basking behavior of the Hawaiian monk seal on Laysan Island. 

J. Wildl. Manage. 30:627-628. 

Clapp, R. B,, and W. 0. Wirtz, 11. 

1975. The natural history of Lisianski Island, Northwestern Hawaiian 

Islands. Atoll Res. Bull. 186:l-196. 

Fiscus, C. H., A. M. Johnson, and K. W. Kenyon. 

1978, Hawaiian monk seal (Monachus schauinslandi) survey of the 

Northwestern Hawaiian Islands, July, 1978. Processed Rep., 26 p. 

Mar, Mammal Biol. Lab., Northwest Fish. Cent., Natl, Mar. Fish. 

Serv., NOAA, Seattle, WA 98112. 

Henderson, J. R. 

1984. Encounters of Hawaiian monk seal with fishing gear at 

Lisianski Island, 1982. Mar. Fish. Rev. 46(7-9). 

Hofman, R. J. 

1975. Distribution patterns and population structure of Antarctic 

seals. Ph. D. Thesis, Univ. Minnesota, 155 p. 

Johnson, A. M., R. L, DeLong, C. H. Fiscus, and K. W, Kenyon. 

1982. Population status of the Hawaiian monk seal (Monachus 

schauinslandi), 1978. J. Mammal. 63:414-421. 

Johnson, A. M., and E. Kridler. 

1983. Interisland movement of Hawaiian monk seals. 'Elepaio 

44( 5) :43-45 . Johnson, B. W. and P. A. Johnson. 

1978. The Hawaiian monk seal on Laysan Island: 1977. Final report 

submitted to U.S. Marine Mammal Commission, Wash., D.C. Contract 

MMTAC 009. Available U.S. Dep, Commer., Natl. Tech. Inf. Serv., 

Springfield, VA 22161, as PB-285-428, 36 p. 

1981a. Estimating the Hawaiian monk seal population in Laysan 

Island. Final report submitted to U.S. Marine Mammal Commission, 

Wash., D.C. Contract MM1533701-4, 29 p. 
33 

Johnson, B. W. and P. A. Johnson. 

1981b. The Hawaiian monk seal on Laysan, 1978. Final report 

submitted to U.S. Marine Mammal Commission, Wash., D.C. Contract 

MM8AC 008. Available U.S. Dep. Commer., Natl. Tech. Inf. Serv., 

Springfield, VA 22161, as PB-82-109661, 17 p. 

Kenyon, K. W., and D. W. Rice. 

1959. Life history of the Hawaiian monk seal. Pac. Sci. 13:215-252. 

1960. Population dynamics of the Hawaiian monk seal. 9, Mammal. 

41 :376-385. 

Wirtz, W. O., 11. 

1968. Reproduction, growth and development, and juvenile mortality 

in the Hawaiian monk seal. J. Mammal. 49:229-238. 
RECENT TECHNICAL MEMORANDUMS 

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. Microflshe copies cost $3.50. Recent issues of NOAA Technical memorandums from the 

NMFS Southwest Fisheries Center are listed below: 

NOAA TM-NMFS SWFC 37 “Report of the workshop on long-range planning for the 

North Pacific albacore fishery.” 

D. J. MACKETT, Editor 

(November 1983) 

Distribution of four dolphins (Stenella spp. and Delphinus 

delphis) In the eastern tropical Pacific, with an annotated 

catalog of data sources. 

W. F. PERRIN, M. D. SCOTT, G. J. WALKER, F. M. RALSTON 

and D. W. K. AU 

(December 1983) 

Annotated references to techniques capable of assessing the 

roles of cephalopods in the eastern tropical Pacific Ocean, 

with emphasis on pelagic squids. 

J. 8. HEDGEPETH 

(December 1983) 

Summary of environmental and fishing Information, on Guam 

and the commonwealth of the Northern Mariana Islands: 

Historical background, description of the Islands, and review 

of the climate, oceanography, and submarlne topography. 

L. G. ELDREDGE 

(December 1983) 

Diving patterns of the Hawaiian Monk Seal, Lisianski island, 

1982. 

F. V. SCHLEXER 

(February 1984) 

“The Hawaiian Monk Seal of Laysan Island: 1982” 

D. J. ALCORN 

(April 1984) 

38 

39 

40 

41 

42 

43 Atlas of airborne sea surface temperature observations In 

nearshore California waters, 1980-1983. 

P.N. SUND 

(July 1984) 

Potential Impact of deep seabed mining on the larvae of 

tunas and billfishes. 

W.M. MATSUMOTO 

(July 1984) 

Sampling commercial rockfish landings in California. 

A.R. SEN 

(July 1984) 

Histopathological manual for monitoring health of striped 

bass in relation to pollutant burdens. 

J.A. WHIPPLE, M. JUNG, R.B. MacFARLANE and R. FiSCHER 

(August 1984) 

44 

45 

46