Habitat ModelingVisual and Acoustic Surveys

Cetacean visual and acoustic surveys during CalCOFI seasonal cruises in Southern California, 2004-2009: Baleen whales

Lisa M. Munger1, John A. Hildebrand1, Dominique L. Camacho2, Andrea M. Havron2, Melissa S. Soldevilla3, Sara M. Kerosky1, Gregory S. Campbell1, Annie B. Douglas4, and John Calambokidis4

1) Scripps Institution of Oceanography, 8635 Discovery Way, La Jolla, California 92093-0210, USA 3) Duke University Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, NC, 28516 USA

2) Spatial Ecosystems, PO Box 2774, Olympia, WA, 98507, USA 4) Cascadia Research Collective, 218 ½ W. 4th Ave., Olympia, WA 98501, USA

Humpback Whales (Megaptera novaeangliae)

Fin Whales (Balaenoptera physalus)

Blue Whales (Balaenoptera musculus)

Los Angeles

Acoustic

Los Angeles

Visual

Acknowledgments: We thank the many people who have made this research possible. Marine mammal observers and acousticians included Melissa Soldevilla, Robin Baird, Veronica Iriarte, Autumn Miller, Michael Smith, Ernesto Vasquez, Laura Morse, Karlina Merkens, Suzanne Yin, Nadia Rubio, Jessica Burtenshaw, Erin Oleson, E. Elizabeth Henderson, and Stephen Claussen, whose memory we honor. We also thank CalCOFI and SWFSC scientists Dave

Wolgast, Jim Wilkinson, Amy Hays, Dave Griffith, Grant Susner, and Robert Tombley; ship crew, research technicians, and MARFAC Staff. Funding and project management was provided by Frank Stone, Ernie Young, and Linda Petitpas at the Chief of Naval Operations, division N45, and Curt Collins at the Naval Post Graduate School.

Los Angeles

Acoustic

Los Angeles

Visual

Visual effort tracklines, 2004-2008

Los Angeles

Sonobuoy deployments, 2004-2008

Los Angeles

AcousticVisual

Los Angeles

Abundance Estimation

Sum

mer

200

5S

prin

g 20

05F

all 2

005

Win

ter 2

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Sea Surface Temp. Total Zooplankton Biomass

MethodsSURVEYS: Two trained marine mammal observers were posted on the bridge wings or flying bridge (depending on vessel) to scan for cetaceans using handheld 7-power binoculars, stand-mounted 25-power binoculars (“Big Eyes”) and naked eye. Visual observations were conducted during daylight hours while the ship was underway steaming at approximately 10 kn between stations. Acoustic surveys were also conducted during daylight and included a towed, high-bandwidth hydrophone array while underway to record odontocetes and low-bandwidth Navy sonobuoys deployed near sampling stations to record baleen whales.1

1. Soldevilla, M. S., Wiggins, S. M., Calambokidis, J., Douglas, A., Oleson, E. M., and Hildebrand, J. A. (2006). "Marine mammal monitoring and habitat investigations during CalCOFI surveys," California Cooperative Oceanic Fisheries Investigations Reports 47, 79-91.

DiscussionProbability of visual versus acoustic detection depends on conditions, detection range, and whale behavior (e.g.,

humpbacks less vocal when foraging, but sing during winter migration)Lower blue whale abundance in CalCOFI region 2004-2009: down to 23% of previous southern California estimate

for 1991-2005 (Barlow and Forney 2007) (Ncalcofi = 191, NB&F_socal= 842)Fin whale estimate comparable to Barlow and Forney (2007) (Ncalcofi = 338, NB&F_socal= 359)Humpback whale abundance in CalCOFI region order of magnitude greater than Barlow and Forney (2007); six times

greater if sightings north of 34.5º N excluded (Ncalcofi<34.5= 222, NB&F_socal= 34)Apparent recent decrease in blue whale density off southern California may be due to blue whales broadening foraging

distribution outside study area2

1. Barlow, J., and Forney, K. A. (2007). "Abundance and population density of cetaceans in the California Current ecosystem," Fishery Bulletin 105, 509-526.

2. Barlow, J., Calambokidis, J., and Forney, K. A. (2008). "Changes in blue whale and other cetacean distributions in the California Current Ecosystem: 1991-2008," in California Cooperative Oceanic Fisheries Investigations annual conference 2008: Troublesome Trends or Meandering Variability?, edited by J. Heine (San Diego, CA).

In-progress and future work:

• Develop and refine abundance estimates from visual and acoustic methods

• predictive habitat models potentially combining CalCOFI and other data sets (e.g. HARPs, gliders, biophysical moorings, satellite data)

• monitoring response to natural and anthropogenic variability

•Most frequently sighted baleen whale species: fin whales (n=86 sightings), humpbacks (n=52), and blue whales (n=45)

•Visual and acoustic detections reveal different spatial patterns, which vary with season and year

•Blue whales detected visually and acoustically in summer and fall only, both inshore and offshore

•Fin whales detected year-round visually & acoustically; inshore in spring, in & offshore summer through fall

•Humpback whales seen but not heard inshore in spring-fall; heard but not seen offshore in winter

•Probability of detecting animals visually versus acoustically varies depending on season and behavior

AbstractSeasonal and spatial distribution patterns of cetaceans in the Southern California Bight were assessed using visual and acousticsurveys during quarterly California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from summer 2004 - summer 2009. Acoustic surveys were conducted during daylight and included a towed hydrophone array while underway to record odontocetes and Navy sonobuoys deployed near sampling stations to record baleen whales. The most frequently sighted odontocete species were common dolphin (n=405 sightings), Dall’s porpoise (n=71), Pacific white-sided dolphin (n=56), bottlenose dolphin (n=33), Risso’s dolphin (n=30), and sperm whales (n=28). The most frequently sighted baleen whale species were fin whales (n=86sightings), humpbacks (n=52), and blue whales (n=45). Distribution varied seasonally for several species and was different for visual versus acoustic detections. Grey whales and Dall’s porpoise were sighted primarily in winter and spring, whereas blue whales were visually and acoustically detected in summer and fall only. Some species were detected (by either means) predominantly inshore (depth < 2000 m), including grey whales and Risso’s, bottlenose, and long-beaked common dolphins, whereas most sperm whale sightings and acoustic detections were offshore. Species detected both inshore and offshore included Dall’s porpoise, Pacific white-sided dolphins, short-beaked common dolphins, and blue and fin whales. Humpback whales were visually detected in spring through fall, primarily inshore, whereas they were acoustically detected offshore in winter and spring. Fin whales were only detected (by either means) inshore in spring, whereas during other seasons they were detected both inshore and offshore. These contrasting patterns suggest that the probability of detecting animals visually or acoustically varies depending on their seasonal distribution and behavioral state, e.g. foraging, migrating, and social or reproductive interaction. CalCOFI marine mammal surveys provide useful data for regional cetacean density estimates and seasonal and interannual comparisons thereof, as well as the ability to relate these observations to the 20+ oceanographic variables measured concurrently. As of 2009 these measurements include acoustic backscatter of cetacean prey items such as krill and fish. Understanding patterns of marine mammaloccurrence and habitat use is a critical factor in making informed management decisions regarding Naval exercises and other anthropogenic activities.

•Spring through fall sightings concentrated inshore, within cold waters and relatively greater zooplankton biomass•Colder SST potentially indicates conditions leading to zooplankton production (e.g., coastal upwelling in spring) or physical mechanisms that entrain/concentrate prey (e.g. currents, fronts, eddies)•Zooplankton biomass likely varies on finer spatial scales than sampled; underway echosounder added as of 2009

Blue Whales

Humpback Whales

Fin Whales

Unid. Large Whales

Winter (6093 km) Spring (7406 km) Summer (9365 km) Fall (7181 km)Species n Nb Nb CV n Nb Nb CV n Nb Nb CV n Nb Nb CVFin Whale 6 151 0.47 8 171 0.57 30 491 0.27 23 491 0.48Humpback Whale 5 158 0.46 13 338 0.47 35 690 0.71 15 387 0.37Unid Large Whale 27 351 0.30 14 147 0.35 48 394 0.28 40 430 0.30Humpback < 34.5 N, no trunc 6 174 0.51 10 244 0.60 4 73 0.58 13 303 0.45

Table 2. Bootstrap abundance estimates in CalCOFI region, post-stratified by season

Table 1. Abundance estimated using pooled data from CalCOFI cruises, summer 2004 – spring 2009. n = number of observations, avg gs= average group size, N = analytical abundance estimate, N CV = analytical coefficient of variation on N, Nb = bootstrap abundance estimate.

Species n avg gs N N CV Nb Nb CVNb

95% LCLNb

95% UCLDensity per 1000 km2

Blue Whale 37 1.2 191 0.31 200 0.29 104 325 1.06Fin Whale 67 1.6 338 0.30 343 0.25 190 528 1.87Humpback Whale 68 1.8 426 0.31 423 0.39 179 792 2.35Unid Large Whale 129 1.2 326 0.21 333 0.21 219 483 1.80Humpback < 34.5 N, no trunc 33 1.9 222 0.34 191 0.34 79 340 1.23

Figure 1. Probability of detection with distance from trackline, half-normal cosine model, sightings truncated beyond 2 km.

ABUNDANCE ESTIMATION: Distance 6.0 software was used to estimate abundance of three most common large whale species and unidentified large whales over the CalCOFI study area, approximated at 180,930 km2. See panel for further details.

HABITAT MODELING: Total zooplankton biomass (on station bongo nets), sea surface temperature (underway and station bottle data), and baleen whale sighting data were analyzed using ArcGIS 9.2 Geo-statistical Analyst. Coverages were created for zooplankton biomass using Inverse Distance Weighted interpolation and SST using Kriging with a second order polynomial to account for a NW temperature trend.

Study area ~ 180,930 km2, total effort = 30045 kmMean group size used (size-regression bias NS at α = 0.15)Multipliers: g(0) = 0.921, obtained from Barlow and Forney 2007 (no SE or df)Bootstrap variance: 1000 samples, unit of sampling = grouped same-day transects

Blue whale density est. for summer + fall, effort = 16546 kmHumpbacks and fin whales were post-stratified by season:•Density estimated for pooled data & for each stratum•Encounter rate estimated by stratum •Detection function estimated using pooled data•Cluster size estimated using pooled data

Study Region

Munger, L., D. Camacho, A. Havron, G. Campbell, A. Douglas, J. Calambokidis, and J. Hildebrand. In press. Baleen whale distribution relative to surface temperature and zooplankton abundance off southern California, 2004-2008. CalCOFI annual reports 50.