AFSC/NMML: Shore-based counts of the Eastern North Pacific gray whale stock from central California, 1967 - 2007

The National Marine Fisheries Service (NMFS) has conducted shore-based counts of the Eastern North Pacific stock of gray whales (Eschrichtius robustus) 26 years from 1967 to 2008 at Granite Canyon (or nearby at Yankee Point), 13 km south of Carmel, in central California. Convenient access to the Granite Canyon research station (owned by NOAA but operated by the State of California Department of Fish and Game) and the narrowness of the whales' migratory corridor in this area permitted an efficient counting process at this site. All counts were conducted during the 2-month southbound migration (mid-December to late February) rather than the protracted 3-month northbound migration. The routine nature of these counts and the consistency in research protocol lend themselves to inter-annual trend analyses. Research protocol has been based on single observers independently searching for whales and recording data on environmental conditions and the time, location, count, and direction of travel for each sighting. The counting system and observer performance has been tested through paired, independent observational effort; aerial surveys; thermal imagery; radio-tagging of whales; systematic observations through high-powered (25x) binoculars; and teams of observers tracking specific whale pods through the viewing area.

Shore-based counts of gray whales have provided the fundamental data used to establish the abundance of the Eastern North Pacific Stock of Gray Whales. These abundance estimates are applied to trends analyses to establish the health of the stock. Results from this study were the basis for removing this stock of whales from the list of Endangered and Threatened Wildlife, the first mammalian species to do so without going extinct. Similarly, results from the shore-based counts are used by the International Whaling Commission to estimate the health of the stock relative to whaling quotas used by the Chukotka Eskimos and Makah Indians.

Loaded by FGDC Metadata Uploader, batch 6252, 06-17-2015 19:01

The following FGDC sections are not currently supported in InPort, but were preserved and will be included in the FGDC export:

- Taxonomy (FGDC:taxonomy)

- Spatial Reference Information (FGDC:spref),

- Spatial Data Organization Information (FGDC:spdoinfo)

At this time data can be downloaded from the Alaska Fisheries Science Center website: http://www.afsc.noaa.gov/nmml/software/eranalysis.php

There are no legal restrictions on access to the data. They reside in public domain and can be freely distributed.

User must read and fully comprehend the metadata prior to use. User must acknowledge the Originator when using the data set as a source. User must share data products developed using the source data set with the Originator. Data should not be used beyond the limits of the source scale.

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Southbound gray whale surveys have been conducted over a 40 year period (1967-2007) and while the data collection process has been similar throughout that timeframe, as one might expect, there have been changes to the type and format of the data that were collected. The most notable change began during the 1987/88 survey and has been continued through the 2006/2007 survey. Prior to 1987, the data were collected with a single record that described the survey effort for a watch period. The effort record would contain up to 3 sets of environmental variables (Beaufort (windforce), wind direction and visibility) to record changes in those variables throughout the watch. Those same variables might also be recorded whenever gray whales were sighted. Data for sightings were recorded as separate records with a different format. Unfortunately, no times were recorded with the environment change except for a sighting. Thus, there was no way to know how much of the effort was associated with a particular set of conditions. This was changed in 1987 when the data were collected as an event log with a single data record for each event. The type of event for the record was defined by the field EFLAG which initially had values 1: begin watch, 2: environment change, 3: gray whale sighting, and 4: comment. The set of values for EFLAG has expanded in time. With this format, the time for each environment change was recorded so the amount of survey time under specific conditions (eg fair or better visibility) could be measured. In addition, during the 1987/88 survey and in each subsequent survey, during some or all of the survey, two independent observers searched at the same time to enable an assessment of the number of gray whales that were missed by a single observer. This is denoted by the EXPERIMENT field which was initially defined as 1 when a single observer was searching and 2 when two independent observers were searching. The list of values for this field has subsequently expanded to specify other activities such as observations from the 25x binoculars, podsize calibration, etc. Each observer was designated with a specific LOCATION (eg S for south shed, N for north shed) and each year one of the positions was chosen as the primary location. This has been S with the exception of the 2000/01 and 2001/02 surveys when it was N. The observer data from primary location is used to generate the abundance estimates with corrections for missed whales that are assessed using the simultaneous surveys conducted from the secondary location during some or all of the entire survey period. With the data format changing so dramatically it was necessary to store the data in different database tables. The data collected from 1967-1985, are stored in 2 tables (EffortPre1987 and ERSightingsPre1987) with the first being the data for survey effort and the second for gray whale sightings. The data collected from 1987 to the present is stored in the single table (AllRecentData) in the event log format as it was recorded on the datasheets in the field. Within these two periods, there were other changes in the format and data that were collected and to get them into a common format some changes had to be made to the data format and coding. For data collected from 1967-1987, the data were keypunched onto cards and often the changes were simply in the order or number of columns that were used for each data field. In other cases the coding might change for a field like travel direction or wind direction. Also, new data fields might be added or dropped through time. To accommodate these differences a common set of fields were chosen and values were re-coded (e.g., 1 to S, 2 to N for travel direction). If a data field was not recorded in a particular year, it was given the value of NA for each entry. Each of the original data definitions and formats for the various years can be examined with the following documents: GrayWhale.Format.1984-85.pdf,

The data for each of the surveys was checked for accuracy in some form when they were collected in the field for completeness and accuracy. Data collected from 1967-1988 were keypunched and presumably also validated with computer checks. Data collected during the 1992/93 and 1993/1994 surveys were entered into EXCEL spreadsheets and filtered with range checks and with computer code for analysis of the data. Data from 1995/96 and onward were entered directly into a database program with the most recent version being ERABUND (ERABUND Users_guide243.pdf). Each of the database programs would make sure valid data were entered and would perform completeness checks (e.g., each start watch contained a matching end watch). In the process of merging the data more complete QC procedures were conducted with all of the data and numerous errors and missing records were found in the data collected prior to 1987 and these were documented as described above. Far fewer errors were found in the more recent data but some corrections were made primarily with the EXPERIMENT field where some of the observers in the recent years confused the roles of EXPERIMENT and LOCATION. Some fields like ETIME (event time) and sighting times (STIME/NTIME) had not been checked for consistency so some errors like an ETIME of 7:00 with an STIME of 19:00 were corrected but they were not common. Also, some start/end watch records were incorrectly matched and this was discovered during the analysis process.

See descriptions of methods at http://www.afsc.noaa.gov/nmml/software/eranalysis.php

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