New Zealand sealion demographic data

Data for the estimation of the demographic parameters of New Zealand sea lion (such as survival, breeding success, etc.) are collected by tagging sea lion pups, and then recording subsequent resightings of tagged animals. Sea lion are tagged using plastic numbered flipper tags. In the past brands and micro chips have also been used to identify animals. This database contains data on the tagging and resighting of tagged individuals, from 1980. Data on the effort spent on searching for tagged animals, or on animals found without tags are not recorded here. Other work is also carried out dusring the Auckland Islands field season, such as counting the pups. These other data are not included. An overview of New Zealand sea lion biology, they issues they face, and current management is available in the sea lion species management plan.

Data collection

The majority of sightings data were collected by a series of research projects at the Auckland Islands. A detailed understanding of the field methods used is crucial to any meaningful analysis. Users of the data should be familiar with the annual field reports, and associated analyses, that can be found on the Conservation Services Programme publications webpages. The tagging and resighting work that was carried out in the 2011–12 season is summarised in a report by Louise Chilvers. Other sightings reported to the Department of Conservation are also included in the data.

The Department of Conservation encourages investigators conducting any analyses relevant to the understanding of commercial fishing impacts on New Zealand sea lions to report draft findings to the CSP Technical Working Group. For publications and details of meetings see the website of DOC CSP. A recent analysis of the demographic parameters os New Zealand sea lion using these data is available in a report by Darryl MacKenzie.

Data provenance

Data were provided in as spreadsheets. They were groomed to complete missing data, and to correct inconsistencies. A key grooming step was the creation of individual sea lion records, associated with a consistent set of tags, brandings and microchips. Other minor errors, such as incorrect dates, incorrect tag colours, and errors in sea lion locations were also corrected. A record was kept of all changes to the data. These changes are visible from individual sightings, by following the details link. A record of all updates is available as a CSV file.

Some additional text comments attached to sightings are not provided here, as they have not had personal information redacted. To access this content, contact the Conservation Services Programme (

Data licence

Data are made available for reuse by the Department of Conservation, under a creative commons attribution licence, following the recommendations of NZGOAL. This licence allows the data to be used for any other purpose and republished, provided only that attribution is given to the source. At the bottom of each page, a citation is given with a preferred format for referencing the data.


This database was developed by Finlay Thompson and Richard Mansfield of Dragonfly Science. We are grateful for the scientists, most recently Louise Chilvers, who run the tagging and resighting research, and who have collected these data. The development of this database was funded by the Department of Conservation's Conservation Services Programme project POP 2011/01, principally through a levy on the quota holders of SQU 6T fish stocks.


For information about the New Zealand sea lion tagging and resighting programme please contact the Conservation Services Programme ( To report problems with the website, or for queries about the data grooming and preparation, please contact Finlay Thompson (

Searching the sightings data

Filters are typed into the search box as a key, followed by a colon, followed by a value. For example season:2012 restricts the data to sightings that occurred during the 2011–12 field season. Filters that are applied will appear above the search box, and may be removed by clicking on the cross beside them. Recognised filter keys are listed below:

from: Finds sightings that occurred on or after a date given in YYYY-MM-DD format. For example: from:2002-02-02

to: Finds sightings that occurred on or before a date given in YYYY-MM-DD format. For example: to:2003-03-03

season: Finds sightings that occurred in a season from 1 July to 30 June. For example, entering season:2003 will set the from date to 2002-07-01 and the to date to 2003-06-30.

year: Finds sightings that occurred in a calendar year. For example, entering year:2003 will set the from date to 2003-01-01 and the to date to 2003-12-31.

month: Finds sightings that occurred in a calendar month. For example, entering month:2003-04 will set the from date to 2003-04-01 and the to date to 2003-04-30.

day: Finds sightings that occurred on the given day. For example, entering day:2003-04-05 will set both the from and to dates to 2003-04-05.

sealion: Finds sightings associated with a given sealion label. For example, sealion:20100117-M366.

tag: Finds sightings of any sealion which is associated with the given tag. This filter expects a colour, shape, and tag number, in that order, separated by colons. For example, tag:BB:C:M366 specifies the tag with the colour BB, the shape C, and number B366. Note that all sightings associated with sealions who have the tag are returned, even sightings which may have occurred after the tags were lost, or the animal was retagged. Codes that have been used for tag colours are B03, BB (blue); G05, GG (green); O06, OO (orange); P03, PP, PUR (purple); RR (red); WW (white); Y04, Y05, Y08, YY (yellow). Codes used for tag shape are R (Round) or C (Coffin).

Components of the tag search can be left out and replaced by a question mark. For example, to search for all tags with the number 4321, enter tag:?:?:4321.

Unknown digits in the tag number can also be given as a question mark, for example, tag:YY:R:123? finds all round tags with the colour YY and a number starting with "123"; tag:?:?:9?1? finds the tag numbers starting with 9 and with a 1 in the third position.

chip: Finds sightings of any sealion which is associated with the given chip number. For example, chip:00-0708-CE88. Note that all sightings associated with sealions known to have the chip are returned, even sightings in which the animal was identified by some other method. Unknown characters can be replaced with a question mark.

brand: Finds sightings of any sealion with a brand number. All sightings associated with sealions known to have the brand are returned, even when the animal was identified by some other method. Unknown digits can be replaced with a question mark.

location: Restricts the search to sightings at the given location, for example: location:SOUTH-EAST-POINT. Locations with more than 50 sightings are SANDY-BAY, DUNDAS, SOUTH-EAST-POINT, EAST-BAY, DERRY-CASTLE, DAVIS-POINT, TEAL-LAKE, FIG-8, ENDERBY, SNARES, SE-BEACH, PARADISE-POINT, TIAMA-COLONY, SANDY-BAY-CAMPBELL, BEEMAN, SE-PT-EAST-BAY, ROSE, NE-CAPE, TUCKER-COVE, LOOKOUT-BAY.

island: Restricts the search to sightings at the given island, for example: island:ENDERBY. Recognised values are ENDERBY, DUNDAS, CAMPBELL, AT-SEA, AUCKLAND, ADAMS, FIG-8, FRIDAY, MACQUARIE, ROSE, SHOE, SNARES, STEWART-ISLAND and SOUTH-ISLAND.

event: A filter of event:T, restricts the search to Tag, Tag(adult) and Retag events.

sex: Filters by sex, for example: sex:F. Valid values are 'M', 'F', and 'U' (for unknown).

Description of fields

Tag data

Tags: Tags are identified by codes for colour and shape, followed by a number.

Colour codes are two or three characters long, and describe the colour of the tag. The following colour codes are in use: B03, BB, G05, GG, O06, OO, P03, PP, PUR, RR, WW, Y04, Y05, Y08, YY.

Shape is either 'R' for round, or 'C' for coffin-shaped tags.

Tag numbers are either a four-digit number, an 'A' or 'B' followed by a four-digit number, or a single letter followed by a three-digit number.

An empty or greyed out tag field indicates that the animal was identified by brand, chip, or some other method.

Flipper tagged: L0,R0: No tags remaining. Animial identified by the brand, transponder chip, or natural markings.

L?,R?: The number of tags remaining is unknown, or was not recorded at the time of sighting.

L1,R1: Two tags recorded.

L1,R0: Left tag only.

L0,R1: Right tag only.

L1,R?: Left tag remaining, right flipper not seen.

L?,R1: Right tag remaining, left flipper not seen.

L0,R?: No left tag; right flipper not seen.

L?,R0: No right tag; left flipper not seen.

1 tag: One tag recorded. Not noted whether the tag was seen in the left or right flipper.

RECOV X1: Single tag recovered.

RECOV X2: Two tags recovered.

Chip data

From 1998–2002, and from 2010, implantable transponder chips were incorporated into the marking programme.

A chip number is a twelve character string beginning with "00-" (for example, 00-013F-002C), or a 15-digit string (for example, 956000007426867). If this field contains a chip number, it is either a marking event during which a chip was implanted, or a resighting where the animal was identified by the chip.

Other possible values in this field are:

NO CHIP FOUND: The animal was scanned, but no chip was found.

N: Either no chip was found, or the animal is believed not to have had a chip implanted.

Y: The animal has a chip, but the chip number was not recorded, and it is not known whether the chip was used to identify the animal.

If this field is empty, the animal was not scanned for a chip.

Brand data

A number in this field indicates either a marking event during which an animal was branded, or a resighting where the animal was identified by the brand number.

'Y' indicates that a brand was seen, but does not always mean that the brand was used to identify the animal.

If the field is empty, no brand was seen.

Event data

Tag: Marking event for an animal tagged or branded for the first time as a pup.

Tag (adult): Adult females tagged or branded for the first time as an adult (during the period 1998 to 2001).

Re-tag: Marking of an animal that has previously been tagged or branded as a pup or adult.

Resight: Sighting of a marked animal after the tagging event.

Resight (Chip): Resight of a marked animal using an implanted transponder chip to confirm identity.

Tag recovered: Recovery of tags from dead animals, or recovery of lost tags without an animal sighting.

Sealion data

If an animal has been identified for a particular sighting, this field will contain a sealion code. Clicking on the code will restrict your search to sightings of the same animal.

Sex data

The sex of the animal, either Female, Male, or Unknown. In most cases, Unknown relates to cases where the sex was not recorded at the time of tagging.

Age class data

The age class of the individual.

Pup: Animal in first year of life.

Yearling: One year old.

Immature: Male aged 2-5, or two year old female.

Subadult: A female old enough to breed (3-5 years), but not confirmed as having bred.

Adult: Males 6 years and older, femals 6 years and older, and females 3-5 years old confirmed to have pupped at an earlier age.

Unknown: Age class not recorded.

Status data

Behavioural information about the animal. The following descriptions are used:

New born or pup: New born or pup, possibly still with mother.

Yearling: Yearling.

Female, confirmed pupped: An adult female either seen nursing or giving birth during the breeding season.

Idle: No specific behaviour.

Territorial male: Adult harem-holding male.

Peripheral male: Non-territorial male, adjacent to breeding aggregation, challenging for access to females.

Yearling or 2 YO, suckling: Yearling or two year-old that is suckling from an adult female.

Pregnant female: Pregnant adult female. Code sometimes applied to an earlier sighting record when an adult female is subsequently confirmed to have pupped.

Tag recovered: Tags recovered, no longer attached to an animal.

Dead: Animal found dead.

Killed, commercial fishing: Animal killed in commercial fishing operation.

Adult female, confirmed no pup: Adult female did not produce a pup in the breeding season (at least three sightings of a female with no evidence of a pup present).

Moulting: Animal moulting.

Female, probably pupped: Female seen on three or more occasions including at least one sighting in the presence of a pup, but not seen giving birth or nursing the pup.

Female, pup died: Adult female whose pup died during the breeding season.

Female, nursing yearling: Adult female nursing previous season's offspring.

Female 3-5 YO, never pupped: Females aged 3-5 years seen during the breeding season that have not previously pupped.

Male, behaviour not recorded: Behaviour not recorded, or male not in close proximity to a breeding aggregation.

Female, < 3 sightings, no pup: Female with fewer than three sightings during a breeding season, with no pup present.