We evaluated harbor porpoise (Phocoena phocoena (Linnaeus, 1758)) strandings in the Salish Sea to determine calving seasonality (1980–2015). A total of 443 strandings were analyzed, of which 134 were ...calves and 53 were neonates. Stranded calves were reported every month, but peaked in July, August, and September. Based on fetal size and an estimated fetal growth rate of 80 mm/month, mean (±SD) conception date (and range) was back-calculated to 11 October ± 30 days (16 August – 31 December) and was later than in most other studies. Using mean (±SD) length at birth (80 ± 5.8 cm), gestation was estimated to be approximately 10.8 months. Estimated birthing period was 16 July – 27 November, with a mean (±SD) birth date of 10 September (±30.7 days) and a birth length of 80.0 cm. Estimated pregnancy rate (0.28–0.29) is lower than reported in other areas and is likely an underestimate due to missed early embryos, poor postmortem condition of a large proportion of the stranded adult females, and potential biases related to the animals that strand and are available. This study of harbor porpoise reproduction and calving in the Salish Sea is the first assessment of calving seasonality for this species in the northeast Pacific Ocean.
Satellite tags were attached to 10 sperm whales Physeter macrocephalus (1 whale was tagged in 2 different years) to determine the movements of sperm whales involved in removal of sablefish from ...longline fishing gear in the Gulf of Alaska (GOA). Tags transmitted from 3 to 34 d (median = 22) in 2007 and 7 to 158 d (median = 45) in 2009. Seven whales stayed in the GOA; all were associating with fishing vessels along the slope. Two whales headed south in June shortly after being tagged; one reached the inner third of the Sea of Cortez; the other's last location was offshore Mexico at 14 degree N. A third whale stayed in the GOA until October and then headed south, reaching central Baja, Mexico, 158 d after tagging. The whales that travelled to lower latitudes followed no pattern in timing of departure, and at least 2 had different destinations. All whales passed through the California Current without stopping and did not travel to Hawaii; both are areas with known concentrations of sperm whales. Whales travelled faster when south of 56 degree N than when foraging in the GOA (median rate of median horizontal movement = 5.4 range:4.1 to 5.5 and 1.3 range:0.6 to 2.5 km h super(-1), respectively). Tagged sperm whales primarily travelled over the slope, but one spent considerable time over the ocean basin. Information on the timing and movement patterns of sperm whales may provide a means for fishermen to avoid fishing at whale hot spots, potentially reducing interactions between whales and fishermen.
During the last 3 decades, tagging technology has been used to study different aspects of cetacean ecology. Tags implanted in animal's blubber, muscle and surrounding tissue have produced successful ...results, providing information on long-term movements. However, apart from the reports of 'divots' (depressions) and swelling at the tag sites in re-sighted large whales, little has been published about the long-term effects of tagging. Based on sighting history databases of photo-identified blue whales, we monitored the wound site of a satellite tag on an adult female blue whale over a period of 16 yr (1995 to 2011). This report describes the swelling reaction to a broken subdermal attachment from a tag designed early in the evolution of large whale tagging. The tag attachment remained embedded for a decade (much longer than expected), and may have affected the female's reproductive success during this period. The whale's calving history showed a total of 3 calves; 2 were prior to, and one ocurred after, the swelling period (1999 to 2007). We demonstrate the value of long-term monitoring programs in evaluating tag impacts, especially on endangered species.
Whale flukeprints are an often observed, but poorly understood, phenomenon. Used by whale researchers to locate whales, flukeprints refer to a strikingly smooth oval-shaped water patch which forms ...behind a swimming or diving whale on the surface of the ocean and persists up to several minutes. In this paper we provide a description of hydrodynamic theory and related experiments explaining the creation and evolution of these “whale footprints.” The theory explains that the motion of the fluke provides a mechanism for shedding of vortex rings which subsequently creates a breakwater that damps the short wavelength capillary waves. The theory also suggests that the role of natural surfactants are of secondary importance in the early formation of these prints.
Knowledge of reproduction in baleen whales such as the blue whale Balaenoptera musculus is still limited. Here, we combined the sighting histories of 24 yr of reproductively active female blue whales ...from the United States (US) west coast and the Gulf of California (GoC), Mexico. The latter region is a nursing ground for some of the blue whales that feed off the US west coast during the summer months. We report here that females show site fidelity to the GoC even when not lactating. The mean calving interval based on consecutive sighting histories was 2.57 yr. Two female calves returned with their own offspring after 11 and 13 yr, indicating an apparent age of first parturition of >10 yr. While 60% of females identified in the GoC were also sighted off the US west coast, only 30% of the females from the latter area were seen in the GoC. Thus only a part of the US Californian population migrates to the GoC, suggesting the existence of additional calving and nursing grounds for this population. Despite the presence of killer whales, female blue whales presumably migrate to the GoC to benefit from high prey abundance. The lack of documented births in the GoC may indicate that female blue whales choose open, pelagic waters for calving and move to the GoC when the calves are older.
The harbor seal (Phoca vitulina) can serve as a useful indicator of food web contamination by persistent organic pollutants (POPs) because of its high trophic level, wide distribution in temperate ...coastal waters of the Northern Hemisphere, and relative ease of capture. In 1996 through 1997, we live‐captured 60 harbor seal pups from three regions, spanning remote (Queen Charlotte Strait, BC, Canada), moderately industrialized (Strait of Georgia, BC, Canada), and heavily industrialized (Puget Sound, WA, USA) marine basins straddling the Canada‐United States border. Biopsy samples of blubber were taken and analyzed for congener‐specific polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐p‐dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) by using high‐resolution gas chromatography‐high‐resolution mass spectrometry. Harbor seals in Puget Sound were heavily contaminated with PCBs, whereas seals from the Strait of Georgia had relatively high concentrations of PCDDs and PCDFs. Pattern evaluation and principal components analysis suggested that proximity to sources influenced the mixture to which seals were exposed, with those inhabiting more remote areas being exposed to lighter PCB congeners (those with lower Henry's law constant and KOW) that disperse more readily through atmospheric and other processes. Total toxic equivalents to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin for the PCBs, PCDDs, and PCDFs suggest that Puget Sound seals are at greatest risk for adverse health effects, and that PCBs represent the class of dioxinlike contaminants of greatest concern at all sites.
Humpback whales
Megaptera novaeangliae
typically fast for several months in low-latitude breeding areas. Here we report on persistent feeding events during 5 wintering seasons between 2013 and 2020 ...in a known upwelling region of Banderas Bay of the mainland Mexico breeding area. In total, there were 76 unique feeding events documented (group size = 1 to ~100 individuals), involving 201 photo-identified whales, of which 18 were documented feeding in multiple years. The most prolific years of documented feeding in 2017 and 2018 (based on number of reports/individuals photo-identified feeding) followed the strongest marine heatwave ever recorded in the North Pacific. Whales documented feeding in Banderas Bay had significantly shorter mean sighting histories (2.3 yr) than a non-feeding sample (8.7 yr) and were reported to be of small size, suggesting they were predominantly younger whales. Most high-latitude recaptures of Banderas Bay feeding whales were in more northern North Pacific feeding grounds (50.8% were resighted in Russia, Alaska, and northern British Colombia, Canada). A binomial general linear model revealed a significant relationship between the probability of whales feeding in Banderas Bay and sea surface temperature (SST). Specifically, feeding consistently occurred in years of lower than average winter SST (<25°C), associated with La Niña years of the El Niño Southern Oscillation (ENSO). We conclude that feeding of humpback whales is now a predictable occurrence in the upwelling region of Banderas Bay in years that ENSO fluctuations lead to lower regional SST. The magnitude of several years of low-latitude feeding events reported here was likely influenced by climate change induced marine heatwaves that occurred during the study period.
The population structure of variation in a nuclear actin intron and the control region of mitochondrial DNA is described for humpback whales from eight regions in the North Pacific Ocean: central ...California, Baja Peninsula, nearshore Mexico (Bahia Banderas), offshore Mexico (Socorro Island), southeastern Alaska, central Alaska (Prince Williams Sound), Hawaii and Japan (Ogasawara Islands). Primary mtDNA haplotypes and intron alleles were identified using selected restriction fragment length polymorphisms of target sequences amplified by the polymerase chain reaction (PCR–RFLP). There was little evidence of heterogeneity in the frequencies of mtDNA haplotypes or actin intron alleles due to the year or sex composition of the sample. However, frequencies of four mtDNA haplotypes showed marked regional differences in their distributions (ΦST = 0.277; P < 0.001; n = 205 individuals) while the two alleles showed significant, but less marked, regional differences (ΦST = 0.033; P < 0.013; n = 400 chromosomes). An hierarchical analysis of variance in frequencies of haplotypes and alleles supported the grouping of six regions into a central and eastern stock with further partitioning of variance among regions within stocks for haplotypes but not for alleles. Based on available genetic and demographic evidence, the southeastern Alaska and central California feeding grounds were selected for additional analyses of nuclear differentiation using allelic variation at four microsatellite loci. All four loci showed significant differences in allele frequencies (overall FST = 0.043; P < 0.001; average n = 139 chromosomes per locus), indicating at least partial reproductive isolation between the two regions as well as the segregation of mtDNA lineages. Although the two feeding grounds were not panmictic for nuclear or mitochondrial loci, estimates of long‐term migration rates suggested that male‐mediated gene flow was several‐fold greater than female gene flow. These results include and extend the range and sample size of previously published work, providing additional evidence for the significance of genetic management units within oceanic populations of humpback whales.
Phocid herpesvirus-1 (PhHV-1, subfamily Alphaherpesvirinae) was isolated from harbor seals (Phoca vitulina vitulina) in the Netherlands in 1985, and was subsequently identified in Pacific harbor ...seals (Phoca vitulina richardsi) from California, USA in the 1990s. PhHV-1–associated pathology was first recognized in harbor seal carcasses submitted to a veterinary diagnostic laboratory in Abbotsford, British Columbia, Canada in 2000, and 63 cases were identified by 2008. A review of these cases indicated that PhHV-1–associated disease is widespread in harbor seals in the wild and within rehabilitation facilities in the coastal northeastern Pacific (including British Columbia, Canada, and Washington, USA). Morbidity and mortality occurred primarily in neonatal and weanling seal pups, and was due to PhHV-1 alone, or in combination with other disease processes. All cases occurred between July and October, corresponding to the pupping and weaning seasons in this area. Although previous publications have described the prevalence of antibody to PhHV-1 in harbor seals from British Columbia, Canada and Washington, USA this is the first study to focus on the epidemiology and pathology of the virus in this region.
Hunting during the last 200 years reduced many populations of mysticete whales to near extinction. To evaluate potential genetic bottlenecks in these exploited populations, we examined mitochondrial ...DNA control region sequences from 90 individual humpback whales (Megaptera novaeangliae) representing six subpopulations in three ocean basins. Comparisons of relative nucleotide and nucleotype diversity reveal an abundance of genetic variation in all but one of the oceanic subpopulations. Phylogenetic reconstruction of nucleotypes and analysis of maternal gene flow show that current genetic variation is not due to postexploitation migration between oceans but is a relic of past population variability. Calibration of the rate of control region evolution across three families of whales suggests that existing humpback whale lineages are of ancient origin. Preservation of preexploitation variation in humpback whales may be attributed to their long life-span and overlapping generations and to an effective, though perhaps not timely, international prohibition against hunting.
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