Boat Surveys for Whale Abundance
Boat surveys are conducted to document seasonal trends in gray whale abundance and to estimate the minimum number of gray whales within the primary gray whale winter aggregation and breeding lagoons along the Pacific coast of Baja California. Each survey utilizes a hand-held Global Position System (GPS) device to follow a predetermined survey track line that passes through the deep-water areas utilized by gray whales in each lagoon. Observer and sighting protocols are specified for each lagoon's unique characteristics and are used to record whales' counts along each track line. This method allows comparison within-year survey counts along identical survey tracks in each lagoon area, and for comparison with historical counts from previous years.
Whale counts are conducted from 7-8-m long outboard-powered boats (Pangas) at a speed of 11-km/hr. Speed and course along the track line are continuously verified using a hand-held GPS. This survey speed minimized the likelihood that whales (which typically travel at 7 to 9-km/hr) do not move ahead of the survey boat and are counted more than once. It also allows observers sufficient time to detect surfacing whales along the track line.
Foreach survey, two pairs of observers (one pair searching to the left and one pair searching to the right sides of the boat) note the number of whales seen they pass abeam of the survey boat, thereby documenting the number and distribution of whale sightings along the track line. A fifth person records each sighting on printed survey forms, noting: the time of each sighing, the number of whales in each group, their direction of movement, and whether they are single whales or female-calf pairs.
Boat surveys in Laguna San Ignacio began in the winter of 2006 and continue to the present. Each survey follows a 30-km long GPS track line that begins at the north end of Isla Garzas in the northernmost end of the lagoon (North End Basin) to the west end of Isla Ana at Punta Holcombe at the lagoon entrance. The survey track line is divided into five "zones" or segments to record the whales' distribution within the lagoon. Whales in the "North End Basin" (north of the survey track line) are counted from the center of this area by observers searching in 360-degrees around the stationary boat.
Gray whales in the Bahía Magdalena lagoon complex include three different areas where gray whales gather in winter: Canal de Santo Domingo in the north from Boca la Soledad south to La Florida; in Bahía Magdalena's center region, west and southwest areas; and in Bahía Almejas in the south from a point in the center of the bay south of Puerto el Dátil north to the north-east of Puerto Cortés on Isla Santa Margarita.
Examples of the seasonal numbers of gray whales in Laguna San Ignacio from 2016 to 2026.
Single whales’ abundance counts comparison in Laguna San Ignacio (2016 to 2026).
Survey counts of female-calf pairs, comparison in Laguna San Ignacio (2016 to 2026).
Weekly abundance counts in Laguna San Ignacio and in the Bahía Magdalena lagoon complex for the current year are shown on our "Weekly Gray Whale Abundance" counts page: Link below...