Blue whale body condition assessed over a 14-year period in the NE Pacific: annual variation and connection to measures of ocean productivity

Large marine mammals can serve as an indicator of the overall state of the environment due to their apex position in marine food webs and their functions as sentinels of change. Reductions in prey, driven by changes in environmental conditions can manifest in reduced fat stores that are visible on whales. We developed a non-invasive technique using photographs of blue whales taken on the US west coast from 2005-2018 (n=3,660) and scored body condition based on visible undulations from the vertebral processes and body shape. We analyzed patterns in the body condition of whales across years and their relation to oceanographic conditions. Females with calves had significantly poorer body conditions and calves had significantly better body conditions compared to other adult whales (Chi-Square, x(2 =) 170.36, df=6, p50% had poor body condition) coincides with the marine heat wave that affected the NE Pacific 2014-2016. A cumulative mixed model examining the relationship between body condition and environmental variables revealed that negative Pacific Decadal Oscillation and longer upwelling seasons correlated with better blue whale body condition, likely to be due to higher primary productivity and prey availability. This study indicates that with an adequate scoring method, photographs collected during boat based surveys can be used to effectively evaluate whale health in response to a changing ocean.info:eu-repo/semantics/publishedVersio

BLUE WHALE VISUAL AND ACOUSTIC ENCOUNTER RATES IN THE SOUTHERN CALIFORNIA BIGHT

The relationship between blue whale (Balaenoptera musculus) visual and acoustic encounter rates was quantitatively evaluated using hourly counts of detected whales during shipboard surveys off southern California. Encounter rates were estimated using temporal, geographic, and weather variables within a generalized additive model framework. Visual encounters (2.06 animals/h, CV = 0.10) varied with subregion, Julian day, time of day, and year. Acoustic encounters of whales producing pulsed A and tonal B call sequences (song; 0.65 animals/h, CV = 0.06) varied by Julian day, survey mode (transit or stationary), and subregion, and encounters of whales producing downswept (D) calls (0.41 animals/h, CV=0.09) varied by Julian day and the number of animals seen. Inclusion of Julian day in all models reflects the seasonal occurrence of blue whales off southern California; however, the seasonal peak in visual encounters and acoustic encounters of D calling whales (July–August) was offset from the peak in acoustic encounters of singing whales (August–September). The relationship between visual and acoustic encounter rates varied regionally, with significant differences in several northern regions. The number of whales heard D calling was positively related to the number of animals seen, whereas the number of singing whales was not related to visual encounter rate

2006 progress report on acoustic and visual monitoring for cetaceans along the outer Washington Coast

An acoustic and visual monitoring effort for cetaceans was initiated within the boundaries of the proposed expansion area for the Quinault Underwater Tracking Range in July 2004. Acoustic data collection consisted of recordings at a site on the continental shelf to the west of Cape Elizabeth and another in deep water within Quinault Canyon. An analysis plan for acoustic data is included. Results for 32 visual surveys are presented as tables and charts for pinnipeds, dolphins, porpoises, and whales. Time series of vocalizations detected in acoustic recordings are presented for killer whales, white-sided dolphins, Risso's dolphins, unclassified dolphins, humpback whales, and sperm whales. Visual sightings show clear differences in locations, reflecting preferred habitats as well as providing information on seasonal occurrence of some species. Preliminary comparison of acoustic and visual data sets reveals interesting patterns. For example, humpback whales are most commonly seen in summer and fall throughout the visual survey region, yet song and feeding calls of these whales are heard almost exclusively in fall and winter. First steps in the development of a predictive habitat model for cetaceans are described. Continued visual and acoustic data collection is recommended. Brief summaries of papers given at four scientific meetings are included

Patterns of cetacean sighting distribution in the Pacific Exclusive Economic Zone of Costa Rica based on data collected from 1979-2001

Nineteen species of cetaceans (families Balaenopteridae, Kogiidae, Physeteridae, Ziphiidae and Delphinidae) occur in the Costa Rican Pacific Exclusive Economic Zone (EEZ). Based on data recorded from the EEZ by the Southwest Fisheries Service Center, Cascadia Research Collective, and CIMAR between 1979- 2001, we mapped the distribution of 18 cetacean species. Our results suggest that the majority of the cetacean species use primarily oceanic waters, particularly those species within the families Balaenopteridae, Kogiidae, Physeteridae and Ziphiidae. Members of the family Delphinidae showed a wide variety of distribution patterns: seven species are widespread throughout the EEZ, four appear to be exclusively pelagic, and two are primarily coastal. Overall, three cetacean species appear to have populations concentrated in coastal waters: Stenella attenuata graffmani, Tursiops truncatus, and Megaptera novaeangliae. These three may be more susceptible to human activities due to the overlap of their ranges with fishery areas (tuna and artisanal fisheries), and an uncontrolled increase of touristic whale watching activities in several parts of their range. The distribution maps represent the first comprehensive representation of cetacean species that inhabit Costa Rican Pacific waters. They provide essential base-line information that may be used to initiate conservation and management efforts of the habitats where these animals reproduce and forage

Inter-annual and seasonal trends in cetacean distribution, density and abundance off southern California

The article of record as published may be located at https://doi.org/10.1016/j.dsr2.2014.10.008Funded by Naval Postgraduate SchoolTrends in cetacean density and distribution off southern California were assessed through visual line- transect surveys during thirty-seven California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from July 2004–November 2013. From sightings of the six most commonly encountered cetacean species, seasonal, annual and overall density estimates were calculated. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) were the most frequently sighted baleen whales with overall densities of 0.91/1000 km2 (CV 1⁄4 0.27), 2.73/ 1000 km2 (CV 1⁄4 0.19), and 1.17/1000 km2 (CV 1⁄4 0.21) respectively. Species specific density estimates, stratified by cruise, were analyzed using a generalized additive model to estimate long-term trends and correct for seasonal imbalances. Variances were estimated using a non-parametric bootstrap with one day of effort as the sampling unit. Blue whales were primarily observed during summer and fall while fin and humpback whales were observed year-round with peaks in density during summer and spring respectively. Short-beaked common dolphins (Delphinus delphis), Pacific white-sided dolphins (Lagen- orhynchus obliquidens) and Dall’s porpoise (Phocoenoidesdalli) were the most frequently encountered small cetaceans with overall densities of 705.83/1000 km2 (CV1⁄40.22), 51.98/1000 km2 (CV1⁄40.27), and 21.37/1000 km2 (CV 1⁄4 0.19) respectively. Seasonally, short-beaked common dolphins were most abun- dant in winter whereas Pacific white-sided dolphins and Dall’s porpoise were most abundant during spring. There were no significant long-term changes in blue whale, fin whale, humpback whale, short- beaked common dolphin or Dall’s porpoise densities while Pacific white-sided dolphins exhibited a significant decrease in density across the ten-year study. The results from this study were fundamentally consistent with earlier studies, but provide greater temporal and seasonal resolution.Funding was provided by the Chief of Naval Operations Environmental Readiness Division, the United States Navy’s Pacific Fleet, the Naval Postgraduate School Grant #N00244-11-1-027, and the Naval Facilities Engineering Command Living Marine Resources Pro- gramFunding was provided by the Chief of Naval Operations Environmental Readiness Division, the United States Navy’s Pacific Fleet, the Naval Postgraduate School Grant #N00244-11-1-027, and the Naval Facilities Engineering Command Living Marine Resources Pro- gra

Changes in blue whale survival and abundance in the Gulf of California

Understanding the drivers of population abundance and distribution is fundamental to ecology and key to informing conservation actions, particularly in endangered species like blue whales (Balaenoptera musculus). Historically, some Eastern North Pacific blue whales have aggregated in the Gulf of California (GoC) each winter. Using photo-identification data collected around Loreto Bay from 1984 to 2020, we analyzed 453 sightings histories using mark-recapture models. Estimated apparent survival (including permanent emigration) decreased from 0.991, 95% CI [0.977, 0.997] in 1985 to 0.889, 95% CI [0.807, 0.939] in 2019. The estimated number of whales using the study area declined from 96 whales, 95% CI [50, 254] in 2012 to 13 whales, 95% CIs [12, 23 and 12, 28] in 2018 and 2019. Abundance of the whole Eastern North Pacific population is slowly increasing, so our results likely reflect declining usage of the GoC. Linear models found a relationship between the number of whales in the GoC and the difference in sea surface temperature between the study area and the Costa Rica Dome wintering area, suggesting that environmental variation could explain variation in blue whale numbers in the GoC. These results highlight the importance of tracking population dynamics as changing environmental conditions affect the range and distribution of populations.Peer reviewe

Distribution and abundance of humpback whales (Megaptera novaeangliae) and other marine mammals off the northern Washington coast

We examined the summer distribution of marine mammals off the northern Washington coast based on six ship transect surveys conducted between 1995 and 2002, primarily from the NOAA ship McArthur. Additionally, small boat surveys were conducted in the same region between 1989 and 2002 to gather photographic identification data on humpback whales (Megaptera novaeangliae) and killer whales (Orcinus orca) to examine movements and population structure. In the six years of ship survey effort, 706 sightings of 15 marine mammal species were made. Humpback whales were the most common large cetacean species and were seen every year and a total of 232 sightings of 402 animals were recorded during ship surveys. Highest numbers were observed in 2002, when there were 79 sightings of 139 whales. Line-transect estimates for humpback whales indicated that about 100 humpback whales inhabited these waters each year between 1995 and 2000; in 2002, however, the estimate was 562 (CV= 0.21) whales. A total of 191 unique individuals were identified photographically and mark recapture estimates also indicated that the number of animals increased from under 100 to over 200 from 1995 to 2002. There was only limited interchange of humpback whales between this area and feeding areas off Oregon and California. Killer whales were also seen on every ship survey and represented all known ecotypes of the Pacific Northwest, including southern and northern residents, transients, and offshore-type killer whales. Dall’s porpoise (Phocoenoides dalli) were the most frequently sighted small cetacean; abundance was estimated at 181−291 individuals, except for 2002 when we observed dramatically higher numbers (876, CV= 0.30). Northern fur seals (Callorhinus ursinus) and elephant seals (Mirounga angustirostris) were the most common pinnipeds observed. There were clear habitat differences related to distance offshore and water depth for different species