Fin Whale Population Research Articles

Should I stay or should I go? Modelling year‐round habitat suitability and drivers of residency for fin whales in the California Current

AbstractAimUnderstanding the spatial ecology of endangered species is crucial to predicting habitat use at scales relevant to conservation and management. Here, we aim to model the influence of biophysical conditions on habitat suitability for endangered fin whales Balaenoptera physalus, with a view to informing management in a heavily impacted ocean region.LocationWe satellite‐tracked the movements of 67 fin whales through the California Current System (CCS), a dynamic eastern boundary upwelling ecosystem in the Northeast Pacific.MethodsWe use a multi‐scale modelling framework to elucidate biophysical influences on habitat suitability for fin whales in the CCS. Using generalized additive mixed models, we quantify the influence of a suite of remotely sensed variables on broadscale patterns of occupancy and present the first year‐round, high‐resolution predictions of seasonal habitat suitability. Further, we model the influence of contemporaneous biophysical conditions on individual‐level residence times in high‐use habitat.ResultsWe present evidence of year‐round habitat suitability in the southern California Current System, robust to interannual variability, establishing that North Pacific fin whales do not follow the canonical baleen whale migration model. Within the high‐use habitat in the Southern California Bight (SCB), individual‐level residency in localized areas (n = 16 for >30 days; n = 4 for >6 months) was associated with warm, shallow, nearshore waters (>18°C, <500 m), with cool waters (14–15°C) occurring over complex seafloor topographies and with convergent (sub)mesoscale structures at the surface.Main ConclusionsBiophysical conditions in the southern CCS generate productive foraging habitats that can support the fin whale population year‐round and allow for extended periods of residency in localized areas. High‐use habitats for fin whales are colocated with areas of intense human use, including international shipping routes and a major naval training range. Seasonal habitat suitability maps presented here could inform the management of anthropogenic threats to endangered baleen whales in this globally significant biodiversity hotspot.

Okhotsk Finwhale (Balaenoptera physalus) Modern Distribution and Abundance

Population of finwhales in north part of Pacific was exposed to excessive commercial pressure and was almost completely eliminated. Information about finwhales in the Sea of Okhotsk after ending is very poor. Observation of whales in the Okhotsk Sea was performed in June, July 2014 and April 2015 from ships travel to a research polygon, carrying out the following records: date, location of animal, species and number, their movement in relation to the vessel, the visual distance from the vessel to the whale, the intensity of their movements. In late June 2014, 40 individuals in 26 groups of finwhales were taken into account. On average, 10.12 individuals per 100 nautical miles of counting route are calculated. On 27 July 2014 during motion along the coast of eastern Sakhalin, we accounted 14 finwhales in 6 groups in total. On 27 July 2014, during motion along the coast of eastern Sakhalin, we accounted 14 finwhales in 6 groups in total of which are 3.55 groups and 8.28 individuals per 100 nautical miles of accounting route on average. The synthesis of the available literature information and own data shows 2- to 3-fold increase in the number of finwhales in the Sea of Okhotsk in last decades. Such a significant number of finwhales in Okhotsk Sea did not register any initial period of whaling or in the period of its development.

Annual Acoustic Presence of Fin Whale (Balaenoptera physalus) Offshore Eastern Sicily, Central Mediterranean Sea.

In recent years, an increasing number of surveys have definitively confirmed the seasonal presence of fin whales (Balaenoptera physalus) in highly productive regions of the Mediterranean Sea. Despite this, very little is yet known about the routes that the species seasonally follows within the Mediterranean basin and, particularly, in the Ionian area. The present study assesses for the first time fin whale acoustic presence offshore Eastern Sicily (Ionian Sea), throughout the processing of about 10 months of continuous acoustic monitoring. The recording of fin whale vocalizations was made possible by the cabled deep-sea multidisciplinary observatory, “NEMO-SN1”, deployed 25 km off the Catania harbor at a depth of about 2,100 meters. NEMO-SN1 is an operational node of the European Multidisciplinary Seafloor and water-column Observatory (EMSO) Research Infrastructure. The observatory was equipped with a low-frequency hydrophone (bandwidth: 0.05 Hz–1 kHz, sampling rate: 2 kHz) which continuously acquired data from July 2012 to May 2013. About 7,200 hours of acoustic data were analyzed by means of spectrogram display. Calls with the typical structure and patterns associated to the Mediterranean fin whale population were identified and monitored in the area for the first time. Furthermore, a background noise analysis within the fin whale communication frequency band (17.9–22.5 Hz) was conducted to investigate possible detection-masking effects. The study confirms the hypothesis that fin whales are present in the Ionian Sea throughout all seasons, with peaks in call detection rate during spring and summer months. The analysis also demonstrates that calls were more frequently detected in low background noise conditions. Further analysis will be performed to understand whether observed levels of noise limit the acoustic detection of the fin whales vocalizations, or whether the animals vocalize less in the presence of high background noise.

A preliminary model of iron fertilisation by baleen whales and Antarctic krill in the Southern Ocean: Sensitivity of primary productivity estimates to parameter uncertainty

Large marine animals may play a crucial role in storing and recycling bioavailable iron in surface waters by consuming iron-rich prey and subsequent defecation of iron that is excess to their requirements. This biological recycling of iron could enhance primary productivity in iron-limited waters. However, quantifying the effects of marine animals on ocean primary productivity remains challenging because of a limited understanding of the key biogeochemical processes involved. In this paper, we develop a preliminary model that explores these uncertainties and examines the potential effects of historical populations of blue, fin and humpback whales, and the biomass of Antarctic krill required to support the whale populations, on primary productivity in the Southern Ocean.Our results suggest that, despite conservative estimates for key processes in our model, pre-exploitation populations of blue whales and, to a lesser extent fin and humpback whales, could have contributed to iron recycling, resulting in enhanced phytoplankton production in iron-limited Southern Ocean waters. Iron-rich defecation by un-exploited whale populations in the Southern Ocean, and the biomass Antarctic krill required to support them, could have resulted in a contribution to primary productivity of between 1.5×10−4 to 23.4gCm−2yr−1 (blue whales), 1.4×10−4 to 13.9gCm−2yr−1 (fin whales), and 2.4×10−5 to 1.7gCm−2yr−1 (humpback whales). However, only when all parameter estimates are at their upper limits does there appear to be this significant role for whales in enhancing primary productivity, and thus we need to assess the likelihood of these values arising.The high degree of uncertainty around the magnitude of these increases in primary productivity is mainly due to our limited quantitative understanding of key biogeochemical processes. To reduce uncertainty regarding the effect of whales on Southern Ocean primary productivity, future research will need to refine our understanding of five influential model parameters: iron content in krill; krill consumption rates by whales; persistence of whale faecal iron in the photic zone; bioavailability of this retained iron; and the carbon-to-iron ratio of phytoplankton.

Fin whale MDH-1 and MPI allozyme variation is not reflected in the corresponding DNA sequences.

The appeal of genetic inference methods to assess population genetic structure and guide management efforts is grounded in the correlation between the genetic similarity and gene flow among populations. Effects of such gene flow are typically genomewide; however, some loci may appear as outliers, displaying above or below average genetic divergence relative to the genomewide level. Above average population, genetic divergence may be due to divergent selection as a result of local adaptation. Consequently, substantial efforts have been directed toward such outlying loci in order to identify traits subject to local adaptation. Here, we report the results of an investigation into the molecular basis of the substantial degree of genetic divergence previously reported at allozyme loci among North Atlantic fin whale (Balaenoptera physalus) populations. We sequenced the exons encoding for the two most divergent allozyme loci (MDH-1 and MPI) and failed to detect any nonsynonymous substitutions. Following extensive error checking and analysis of additional bioinformatic and morphological data, we hypothesize that the observed allozyme polymorphisms may reflect phenotypic plasticity at the cellular level, perhaps as a response to nutritional stress. While such plasticity is intriguing in itself, and of fundamental evolutionary interest, our key finding is that the observed allozyme variation does not appear to be a result of genetic drift, migration, or selection on the MDH-1 and MPI exons themselves, stressing the importance of interpreting allozyme data with caution. As for North Atlantic fin whale population structure, our findings support the low levels of differentiation found in previous analyses of DNA nucleotide loci.

Fin whale tracks recorded by a seismic network on the Juan de Fuca Ridge, Northeast Pacific Ocean

Fin whale calls recorded from 2003 to 2004 by a seafloor seismic network on the Endeavour segment of the Juan de Fuca Ridge were analyzed to determine tracks and calling patterns. Over 150 tracks were obtained with a total duration of ~800 h and swimming speeds from 1 to 12 km/h. The dominant inter-pulse interval (IPI) is 24 s and the IPI patterns define 4 categories: a 25 s single IPI and 24/30 s dual IPI produced by single calling whales, a 24/13 s dual IPI interpreted as two calling whales, and an irregular IPI interpreted as groups of calling whales. There are also tracks in which the IPI switches between categories. Call rates vary seasonally with all the tracks between August and April. From August to October tracks are dominated by the irregular IPI and are predominantly headed to the northwest, suggesting that a portion of the fin whale population does not migrate south in the fall. The other IPI categories occur primarily from November to March. These tracks have slower swimming speeds, tend to meander, and are predominantly to the south. The distribution of fin whales around the network is non-random with more calls near the network and to the east and north.

Krill feeding on sediment in the Gulf of Maine (North Atlantic)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 455:157-172 (2012) - DOI: https://doi.org/10.3354/meps09632 Krill feeding on sediment in the Gulf of Maine (North Atlantic) Alison C. Cleary*, Edward G. Durbin, Tatiana A. Rynearson University of Rhode Island, Graduate School of Oceanography, Narragansett, Rhode Island, 02882, USA *Email: acleary@gso.uri.edu ABSTRACT: Krill are key members of many marine ecosystems, serving as a critical trophic link between microscopic organisms and large predators such as whales, fish, and seabirds. Krill feeding is thus important to ecosystem carbon cycling. Traditional approaches to determining in-situ krill feeding require a priori assumptions, and may have prey-type detection biases. We took a DNA-based approach to measuring in-situ feeding by northern krill Meganyctiphanes norvegica. The diversity of prey consumed by M. norvegica in situ was analyzed for 80 krill at 8 stations throughout the Gulf of Maine (North Atlantic) using peptide nucleic acid mediated polymerase chain reaction (PNA-PCR) clone library sequencing of 18S rDNA. Relative abundance of the 2 most common prey types was measured with quantitative PCR (qPCR) in the guts of 16 krill. The 245 prey sequences recovered from krill gut contents included copepods, salps, phytoplankton, and a poorly known organism found to be sediment associated. Calanus finmarchicus and the sediment-associated organism were found most commonly, at 7 and 8 stations, respectively, and their 18S rDNA was present in nearly equal quantities in individual krill guts. M. norvegica, like most krill, are typically considered planktivorous; thus krill feeding on sediment organisms represents an unrecognized pathway for carbon flow from the sediment to the pelagic. Calculations suggest that this unrecognized pathway could potentially bring over 100000 t of carbon annually back into the Gulf of Maine pelagic ecosystem, equivalent to 4% of annual primary production, or the energy demands of 80% of the region’s fin whale population. KEY WORDS: Meganyctiphanes norvegica · Gut contents · 18S rDNA · Benthic−pelagic coupling · PNA-PCR Full text in pdf format PreviousNextCite this article as: Cleary AC, Durbin EG, Rynearson TA (2012) Krill feeding on sediment in the Gulf of Maine (North Atlantic). Mar Ecol Prog Ser 455:157-172. https://doi.org/10.3354/meps09632 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 455. Online publication date: May 30, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Dolphin Morbillivirus and Toxoplasma gondii coinfection in a Mediterranean fin whale (Balaenoptera physalus)

BackgroundAlthough Morbillivirus and Toxoplasma gondii have emerged as important pathogens for several cetaceans populations over the last 20 years, they have never been identified together in a Mysticete. In particular, morbilliviral infection has been never described in the Mediterranean fin whale population.Case presentationOn January 2011 an adult male of fin whale (Balaenoptera physalus) stranded along the Tyrrhenian coastline of Italy. During necropsy, tissue samples from heart, skeletal muscle, mesenteric lymph nodes, liver, spleen, lung, and kidney were collected and subsequently analyzed for Morbillivirus and Toxoplasma gondii by microscopic and molecular methods. Following the detailed necropsy carried out on this whale, molecular analysis revealed, for the first time, the simultaneous presence of a Dolphin Morbillivirus (DMV) and T. gondii infection coexisting with each other, along with high organochlorine pollutant concentrations, with special reference to DDT.ConclusionThis report, besides confirming the possibility for Mysticetes to be infected with DMV, highlights the risk of toxoplasmosis in sea water for mammals, already immunodepressed by concurrent factors as infections and environmental contaminants.

Acoustics as a tool in sub-species and population identification for endangered fin whales, Balaenoptera physalus

Identification of “stocks” (sub-species and independent populations) is important for understanding and mitigating potential sources of human-caused mortality. This is especially critical for endangered and protected species, such as the large whales. Stock identification for whales has typically been based on ecology, life history, morphology, and genetics. However, for many species, acoustic differences in whale call types may indicate population or sub-species structure. The potential role of acoustics in identifying species and sub-species has been identified in numerous publications; however, this role has yet to be realized for large whales. In an effort to include acoustic data in this process, we are contributing to current efforts to update the status of endangered fin whales, Balaenoptera physalus, in the North Pacific. An analysis of North Pacific fin whale populations based on identification of “song” provides hypotheses that can be tested with genetics. Strengths and limitations of acoustic methods will be presented, as will the potential for collaboration on the scale of ocean basins.

Fin whale (Balaenoptera physalus) population identity in the western Mediterranean Sea

AbstractArchival bottom‐mounted audio recorders were deployed in nine different areas of the western Mediterranean Sea, Strait of Gibraltar, and adjacent North Atlantic waters during 2006–2009 to study fin whale (Balaenoptera physalus) seasonal presence and population structure. Analysis of 29,822 recording hours revealed typical long, patterned sequences of 20 Hz notes (here called “song”), back‐beats, 135–140 Hz notes, and downsweeps. Acoustic parameters (internote interval, note duration, frequency range, center and peak frequencies) were statistically compared among songs and song notes recorded in all areas. Fin whale singers producing songs attributable to the northeastern North Atlantic subpopulation were detected crossing the Strait of Gibraltar and wintering in the southwestern Mediterranean Sea (Alboran basin), while songs attributed to the Mediterranean were detected in the northwest Mediterranean basin. These results suggest that the northeastern North Atlantic fin whale distribution extends into the southwest Mediterranean basin, and spatial and temporal overlap may exist between this subpopulation and the Mediterranean subpopulation. This new interpretation of the fin whale population structure in the western Mediterranean Sea has important ecological and conservation implications. The conventionally accepted distribution ranges of northeastern North Atlantic and Mediterranean fin whale subpopulations should be reconsidered in light of the results from this study.

Life‐history tables of the Mediterranean fin whale from stranding data

AbstractThe conservation of long‐lived species requires extensive, in‐depth knowledge of their population structure and vital rates. In this paper we examine the structure of the Mediterranean fin whale (Balaenoptera physalus) population based on the available mortality figures from European stranding network databases compiled over the past 22 years. Such data has enabled us to lay out a first life‐history (mortality) table of the population using a simple age‐structured demographic model with three life‐tables: calf, immature and mature. Our results reveal a high mortality rate in the first stage of life (77% per year), which decreases during the immature stage and falls further during the mature adult stage. In addition, we have calculated the corresponding life expectancies at birth (e0), at entry in the immature stage (e1) and at maturity (e2) under different hypotheses on survival at the maximum age of 90 years (s90) ranging between 0.1 and 3% of newborns still alive. The life expectancy at birth (e0) at the lower bound of the chosen range (s90 = 0.001) is about 6 years, entry in the immature stage (e1) is 8.2 years, and entry in the mature stage (e2) is about 15.6 years. This large increase is the consequence of the higher mortality in the first two stages compared with the mature one. The life expectancies are 10.1, 14.3, and 37.8 years for s90 at the upper bound of the chosen range (s90 = 0.03). The resulting population intrinsic growth rates (r) ranged between −1.3. and +1.7 per year. High juvenile mortality patterns imply that the stationary reproductive value (the number of female offspring produced by each female after a given age x) at the start of maturity reaches a value about seven times higher than at birth. Only optimistically high survival patterns of older individuals would allow positive intrinsic growth rates, thereby enhancing the chances of the population survival.

Where do the Chukchi Sea fin whales come from? Looking for answers in the structure of songs recorded in the Bering Sea and Western North Pacific.

Fin whales are common throughout the North Pacific and have recently been detected acoustically as far north as the northeastern Chukchi Sea. Non‐acoustic evidence suggests that North Pacific fin whales are segregated into two populations wintering along the Asian and North American coast with at least some animals intermingling in the summer in the Bering Sea‐Aleutian Islands area. Male fin whales produce regionally distinctive songs which are likely indicative of population structure. In this study we evaluated the relationship of fin whales recorded in the northeastern Chukchi (2007 and 2009) and southeastern Bering (2007–2008) seas by comparing the structure of their song. Additionally, we investigated whether fin whales detected in these areas could be part of an Asian population by comparing their songs to those recorded near the Emperor Seamounts in the western North Pacific (2007). The results will be discussed in light of the current knowledge on North Pacific fin whale population structure.

Distribution and movements of fin whales in the North Pacific Ocean

ABSTRACT We summarize fin whale Balaenoptera physalus catch statistics, sighting data, mark recoveries and acoustics data. The annual cycle of most populations of fin whales had been thought to entail regular migrations between high‐latitude summer feeding grounds and lower‐latitude winter grounds. Here we present evidence of more complex and varied movement patterns. During summer, fin whales range from the Chukchi Sea south to 35 °N on the Sanriku coast of Honshu, to the Subarctic Boundary (ca. 42 °N) in the western and central Pacific, and to 32 °N off the coast of California. Catches show concentrations in seven areas which we refer to as ‘grounds’, representing productive feeding areas. During winter months, whales have been documented over a wide area from 60 °N south to 23 °N. Coastal whalers took them regularly in all winter months around Korea and Japan and they have been seen regularly in winter off southern California and northern Baja California. There are also numerous fin whale sightings and acoustic detections north of 40 °N during winter months. Calves are born during the winter, but there is little evidence for distinct calving areas. Whales implanted with Discovery‐type marks were killed in whaling operations, and location data from 198 marked whales demonstrate local site fidelity, consistent movements within and between the main summer grounds and long migrations from low‐latitude winter grounds to high‐latitude summer grounds. The distributional data agree with immunogenetic and marking findings which suggest that the migratory population segregates into at least two demes with separate winter mating grounds: a western ground off the coast of Asia and an eastern one off the American coast. Members of the two demes probably mingle in the Bering Sea/Aleutian Islands area. Prior research had suggested that there were at least two non‐migratory stocks of fin whale: one in the East China Sea and another in the Gulf of California. There is equivocal evidence for the existence of additional non‐migratory groups in the Sanriku‐Hokkaido area off Japan and possibly the northern Sea of Japan, but this is based on small sample sizes.

Molecular species identification of historical whale remains from South Georgia

The island of South Georgia is located at the southern extreme of the South Atlantic Ocean, on the edge of the Southern Ocean that surrounds Antarctica. Intensive commercial whaling at South Georgia began in 1904, when the first land-based whaling station was built in Grytviken (54°17′S, 36°30′W). Five other shore stations were eventually built: Ocean Harbour (54°20′S, 36°16′W), Leith Harbour (54°08′S, 36°41′W), Husvik Harbour (54°18′S, 36°71′W), Stromness Harbour (54°90′S, 36°41′W), and Prince Olav Harbour (54°40′S, 36°90′W). Another site, Godthul (54°17′S, 36°17′W), was used as a protected anchorage for floating factories. By 1965, when shore-based whaling activity ceased, over 175,000 whales had been processed on the island (Moore et al. 1999). The once abundant stocks of baleen whales in the Antarctic had at that time been reduced to about a third of their former sizes (Laws 1977). When considering blue (Balaenoptera musculus), fin (B. physalus), sei (B. borealis), and humpback (Megaptera novaeangliae) whales together, the average population size was reduced to ca. 18% (Laws 1977). Humpback and blue whales experienced the most severe bottlenecks, having been reduced to about 3% and 5% of the estimated initial populations, respectively. According to more recent estimates, even 80%–95% of the pristine populations of humpback, blue, and fin whales have been killed (Baker and Clapham 2002). For the blue whales depletion to even less than 1% of the pre-exploitation population size has been reported (Branch et al. 2004, 2007). Currently, knowledge about the recovery from the bottlenecks and current population sizes, structures, and migration patterns are important issues in the conservation of Southern Hemisphere baleen whales. In this context, insight into historical population structures would be of great value.

MHC DQB-1 Polymorphism in the Gulf of California Fin Whale (Balaenoptera physalus) Population

One of the most isolated populations of fin whales occurs in the Gulf of California (GOC) with 400-800 individuals. This population shows reduced neutral genetic variation in comparison to the North Pacific population and thus might also display limited adaptive polymorphism. We sampled 36 fin whales from the GOC and assessed genetic variation at exon 2 of the major histocompatibility complex class II DQB-1 genes responsible for eliciting immune responses. Three divergent alleles were found with higher nonsynonymous than synonymous substitution rates within the peptide-binding region positions as well as the likely retention of ancient alleles, indicating that positive selection has shaped diversity in this species. Limited levels of nonneutral polymorphism, in addition to previously described low levels of neutral polymorphism, are consistent with the results of previous studies on vertebrate populations that have remained small and demographically stable for a very long time. Such low genetic variation in the GOC fin whales could be explained by 2 demographic scenarios: an ancient isolated population with limited gene flow or a more recent founder event after the last glacial maximum with very restricted gene flow.

Blue and fin whale call source levels and propagation range in the Southern Ocean

Blue (Balaenoptera musculus) and fin whales (B. physalus) produce high-intensity, low-frequency calls, which probably function for communication during mating and feeding. The source levels of blue and fin whale calls off the Western Antarctic Peninsula were calculated using recordings made with calibrated, bottom-moored hydrophones. Blue whales were located up to a range of 200 km using hyperbolic localization and time difference of arrival. The distance to fin whales, estimated using multipath arrivals of their calls, was up to 56 km. The error in range measurements was 3.8 km using hyperbolic localization, and 3.4 km using multipath arrivals. Both species produced high-intensity calls; the average blue whale call source level was 189+/-3 dB re:1 microPa-1 m over 25-29 Hz, and the average fin whale call source level was 189+/-4 dB re:1 microPa-1 m over 15-28 Hz. Blue and fin whale populations in the Southern Ocean have remained at low numbers for decades since they became protected; using source level and detection range from passive acoustic recordings can help in calculating the relative density of calling whales.

Mediterranean fin whales at risk from fatal ship strikes

This paper reviews and analyzes ship collision records for the relatively isolated population of fin whales in the Mediterranean Sea from 1972 to 2001. Out of 287 carcasses, 46 individuals (16.0%) were certainly killed by boats. The minimum mean annual fatal collision rate increased from 1 to 1.7 whales/year from the 1970s to the 1990s. Fatal strike events (82.2%) were reported in or adjacent to the Pelagos Sanctuary, characterized by high levels of traffic and whale concentrations. Among 383 photo-identified whales, 9 (2.4%) had marks that were attributed to a ship impact. The reported rates are unusually high for baleen whales. The high likelihood of unreported fatal strikes combined with other anthropogenic threats suggests an urgent need for a comprehensive, basin-wide conservation strategy, including ship strike mitigation requirements, like real-time monitoring of whale presence and distribution to re-locate ferry routes to areas of lower cetacean density, and reducing ship speed in high cetacean density areas.

The fin whale Balaenoptera physalus (L. 1758) in the Mediterranean Sea

ABSTRACT 1. The ecology and status of fin whales Balaenoptera physalus in the Mediterranean Sea is reviewed. The species’ presence, morphology, distribution, movements, population structure, ecology and behaviour in this semi‐enclosed marine region are summarized, and the review is complemented with original, previously unpublished data. 2. Although the total size of the fin whale population in the Mediterranean is unknown, an estimate for a portion of the western basin, where most of the whales are known to live, was approximately 3500 individuals. High whale densities, comparable to those found in rich oceanic habitats, were found in well‐defined areas of high productivity. Most whales concentrate in the Ligurian‐Corsican‐Provençal Basin, where their presence is particularly noticeable during summer; however, neither their movement patterns throughout the region nor their seasonal cycle are clear. 3. Based on genetic studies, fin whales from the Mediterranean Sea are distinct from North Atlantic conspecifics, and may constitute a resident population, separate from those of the North Atlantic, despite the species’ historical presence in the Strait of Gibraltar. Fin whales are known to calve in the Mediterranean, with births peaking in November but occurring at lower rates throughout the year. They feed primarily on krill Meganyctiphanes norvegica which they capture by diving to depths in excess of 470 m. It is suggested that the extensive vertical migratory behaviour of its main prey may have influenced the social ecology of this population. 4. Known causes of mortality and threats, including collisions with vessels, entanglement in fishing gear, deliberate killing, disturbance, pollution and disease, are listed and discussed in view of the implementation of appropriate conservation measures to ensure the species’ survival in the region.

DIETS OF FIN, SEI, AND SPERM WHALES IN BRITISH COLUMBIA: AN ANALYSIS OF COMMERCIAL WHALING RECORDS, 1963–1967

AbstractDiets of fin (Balaenoptera physalus), sei (Balaenoptera borealis), and sperm whales (Physeter macrocephalus) were estimated from the stomach contents of individuals killed along the British Columbia coast from 1963 to 1967. The dominant prey types of fin whales were euphausiids, with minor contributions from copepods and fish. Sei whale stomachs contained primarily copepods in three years, whereas euphausiids or a variety of fish dominated the diet in the other two years. Sperm whales consumed primarily North Pacific giant squid (Moroteuthis robusta), but secondary prey differed between males and females. Female sperm whales frequently consumed ragfish (Icosteus spp.) and other fish, whereas the male diet also contained rockfish (Sebastes spp.). The high abundance of euphausiids along the British Columbia coast likely contributed to the presence of a summer resident population of fin whales. The high abundance of large copepods farther north probably influenced the migration of sei whales through the offshore waters of British Columbia. Sperm whale stomach contents differed by sex reflecting location and possibly breeding behaviors.

Genetic identification of a small and highly isolated population of fin whales (Balaenoptera physalus) in the Sea of Cortez, Mexico

For many years, researchers have speculatedthat fin whales are year-round residents in theSea of Cortez (= Gulf of California). Previouswork by Berube and co-workers has shownthat the degree of genetic diversity among finwhales in the Sea of Cortez at nuclear andmitochondrial loci is highly reduced. However,the relatively unobstructed connection with theNorth Pacific Ocean argues that Sea of Cortezfin whales are part of a much larger easternNorth Pacific population given the extensivemigratory ranges observed in fin whales andbaleen whales in general. The low degree ofgenetic variation might thus simply be due tohistoric fluctuations in the effectivepopulation size of an eastern North Pacificpopulation. In order to test if the reducedgenetic variation detected among fin whales inthe Sea of Cortez is due to small populationsize or a past bottleneck in an otherwise largeeastern North Pacific population, we analyzedthe geographic distribution of geneticvariation at a single mitochondrial (controlregion) and 16 nuclear loci in samplescollected from fin whales in the eastern NorthPacific (n = 12) as well as the Sea of Cortez(n = 77). Our results showed that fin whalesobserved in the Sea of Cortez constitute ahighly isolated and thus evolutionary uniquepopulation, which warrants special conservationmeasures given the current low estimate ofabundance of approximately 400 individuals.