OPEN-BOAT WHALING ON THE STRAITS OF GIBRALTAR GROUND AND ADJACENT WATERS

Logbooks ( n = 317) from whaling expeditions made in the North Atlantic during the 19th century were examined to investigate activity in the Gibraltar Straits grounds. At least forty expeditions of whaling vessels from European and American ports visited the area. In all cases the main target was the sperm whale, but pilot whales, dolphins, sea turtles, and even a blue whale were also taken. Whaling effort concentrated on the Atlantic side of the Straits; only two expeditions ventured into the Mediterranean Sea, obtaining negligible catches. The whaling season extended during spring and summer and peaked in June–July. This seasonality appeared not to be governed by changes in whale density but by the trade winds necessary to sail southward or westward to cross the Atlantic. Searching effort continued while trying out, but the rate of sighting cetaceans was about half that of searching periods. However, the rate of sighting or capturing a sperm whale remained unchanged during processing, probably because the gregarious habits of the species produced clumping of catches. For every whale secured, 1.31 whales were struck. After correcting for struck but lost whales and for "gammed" vessels, the minimum number of removals of sperm whales during 1862–1889 is estimated at 237.     

The forgotten whale: a bibliometric analysis and literature review of the North Atlantic sei whale Balaenoptera borealis

• 1 A bibliometric analysis of the literature on the sei whale Balaenoptera borealis is presented. Research output on the species is quantified and compared with research on four other whale species. The results show a significant increase in research for all species except the sei whale. Research output is characterized chronologically and by oceanic basin.
• 2 The species' distribution, movements, stock structure, feeding, reproduction, abundance, acoustics, mortality and threats are reviewed for the North Atlantic, and the review is complemented with previously unpublished data.
• 3 Knowledge on the distribution and movements of the sei whale in the North Atlantic is still mainly derived from whaling records. Movement patterns and winter distribution are not clear. Surveys in some known summering areas show that the species has changed its distribution in parts of its previously known range.
• 4 With the present information, it is impossible to determine whether or not the North Atlantic sei whale population is subdivided into biological units. Abundance estimates are fragmentary and cover a restricted part of the summering habitat.
• 5 In the North Atlantic, sei whales seem to be stenophagous, feeding almost exclusively on calanoid copepods and euphausiids. On feeding grounds, they are associated with oceanic frontal systems, but how they find and explore these structures has not been fully investigated.
• 6 The available data on vital rates are based on whaling‐derived studies and are 25 years old or older. Despite increasing human and environmentally induced pressures, there are no current estimates for mortality and population trends.
• 7 Current research needs include the clear definition of stock units, reliable abundance estimates, studies of distribution and migration that incorporate the identification of wintering areas, acquisition of up‐to‐date data on reproduction and mortality, and investigations into the consequences of environmental changes for the species.

     

RELATIVE ABUNDANCE OF LARGE WHALES AROUND SOUTH GEORGIA (1979–1998)1

To assess large-whale stocks following the cessation of land-based South Georgia whaling in 1965, we report three independent sighting databases: a cruise in 1997, observations from Bird Island (NW of South Georgia) between 1979 and 1998, and mariner sightings between 1992 and 1997. All species were rare, with sightings of southern right whales being the most common event. Two right whales photographed off South Georgia matched animals known from Peninsula Valdés, Argentina, a population known to be growing at 7%per annum. In contrast, blue and fin whales appeared to be less abundant. A single blue whale mother-calf pair was observed off the Shag Rocks in February 1997. Extirpation of animals from this particular feeding ground is the most likely reason for ongoing low numbers of all species. Other factors may include competition for krill by traditional predators such as penguins and seals and more recently by humans, an unusually high rate of natural mortality, habitat change such as alteration in sea ice coverage, and/or the impact of ongoing whaling. The history of this critical area of large-whale habitat and this report demonstrate the need for improved, consistent longterm monitoring of population trends for these depleted stocks.     

What saved the whales? An economic analysis of 20th century whaling

Catches of whales show a historically cyclical pattern, with catches declining as stocks of the financially most attractive species fell, but expanding as substitute species were caught. Total combined catch peaked in the early 1960s and fell thereafter to the current regulated levels. While it is widely thought that international whaling agreements account for the current stable stock levels, economic analysis reveals that market forces leading to reduced catch were already in place well before the agreements took hold. To some extent, therefore, catches were destined to decline as whale products ceased to be commercially attractive on a large scale. Using econometric analysis, the paper shows the various forces at work: declining stocks, the rise of substitute products, internationally increasing environmentalism, and rising incomes. Of these forces, stock decreases, which resulted in high unit catch costs, and income growth, which reduced rather than increased demand, were the most important factors, with regulation following, rather than leading, catch changes.     

Insights into the population structure of blue whales in the Eastern North Pacific from recent sightings and photographic identification

Blue whales were widely distributed in the North Pacific prior to the primary period of modern commercial whaling in the early 1900s. Despite concentrations of blue whale catches off British Columbia and in the Gulf of Alaska, there had been few documented sightings in these areas since whaling for blue whales ended in 1965. In contrast, large concentrations of blue whales have been documented off California and Baja California and in the eastern tropical Pacific since the 1970s, but it was not known if these animals were part of the same population that previously ranged into Alaskan waters. We document 15 blue whale sightings off British Columbia and in the Gulf of Alaska made since 1997, and use identification photographs to show that whales in these areas are currently part of the California feeding population. We speculate that this may represent a return to a migration pattern that has existed for earlier periods for eastern North Pacific blue whale population. One possible explanation for a shift in blue whale use is changes in prey driven by changes in oceanographic conditions, including the Pacific Decadal Oscillation (PDO), which coincides with some of the observed shifts in blue whale occurrence.     

From the southern right whale hunting decline to the humpback whaling expansion: a review of whale catch records in the tropical western South Atlantic Ocean

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The world's smallest whale population?

The North Pacific right whale (Eubalaena japonica) was heavily exploited by both nineteenth century whaling and recent (1960s) illegal Soviet catches. Today, the species remains extremely rare especially in the eastern North Pacific. Here, we use photographic and genotype data to calculate the first mark–recapture estimates of abundance for right whales in the Bering Sea and Aleutian Islands. The estimates were very similar: photographic = 31 (95% CL 23–54), genotyping = 28 (95% CL 24–42). We also estimated the population contains eight females (95% CL 7–18) and 20 males (95% CL 17–37). Although these estimates may relate to a Bering Sea subpopulation, other data suggest that the total eastern North Pacific population is unlikely to be much larger. Its precarious status today—the world''s smallest whale population for which an abundance estimate exists—is a direct consequence of uncontrolled and illegal whaling, and highlights the past failure of international management to prevent such abuses.     

Historic and current habitat use by North Pacific right whales Eubalaena japonica in the Bering Sea and Gulf of Alaska

1. To help define areas and ecological parameters critical to the survival and recovery of the remnant population of North Pacific right whales, habitat use was investigated by examining all available sighting and catch records in the south-eastern Bering Sea (SEBS) and Gulf of Alaska (GOA) over the past two centuries. 2. Based on re-analyses of commercial whaling records, search effort, and resultant catches and sightings, waters of the: (i) SEBS slope and shelf, (ii) eastern Aleutian Islands and (iii) GOA slope and abyssal plain were important habitat for North Pacific right whales through the late 1960s. 3. Since 1980, the only area where right whales have been seen consistently is on the SEBS middle shelf. However, acoustic detections and single sightings have been reported in all other regions except the SEBS slope and oceanic GOA (areas where little, if any, acoustic and visual effort has occurred). 4. Sightings since 1979 were in waters < 200 m deep which may simply reflect the paucity of search effort elsewhere. From the commercial whaling era to the late 1960s, right whales were commonly seen in waters > 2000 m deep, indicating that their distribution is not restricted to shallow continental shelves. 5. North Pacific right whale sightings through the centuries have been associated with a variety of oceanic features, and there is little in common in the bathymetry of these regions. These whales appear to have a greater pelagic distribution than that observed in the North Atlantic, which may be related to the availability of larger copepods across the SEBS and GOA.     

Modern whaling in Britain and the north-east Atlantic Ocean

Modern whaling, using an explosive harpoon fired from a steam catcher-boat to kill the fast-swimming rorquals, began from shore whaling stations in northern Norway in the 1860s. It spread to Iceland, the Faeroe Islands and Spitsbergen, before reaching the British Isles in 1903.
Whaling took place from four stations in the Shetland Islands, one in the Outer Hebrides, and two in Ireland, before the First World War. Fin whales were the main species caught but Blue, Humpback, Sei, Right, Sperm and Bottle-nosed whales were also taken. Four stations re-opened in 1920, but from 1923 onwards only two continued to operate and whaling ceased in 1929, though the Hebridean station worked again for two seasons in 1950–1951.
The species composition of catches at the Hebridean and Irish stations was very similar and different from that of the stations in the Shetland Islands where few Blue whales and Right whales were taken. There is evidence that Fin whales were being overfished on the Shetland Islands whaling grounds at an early date, and that Blue whales and Right whales, but not Fin whales, declined in numbers on the Hebridean grounds.
The history of modern whaling in the north-east North Atlantic region as a whole indicates that the stocks of Blue, Humpback and Right whales were not large enough to support continuous whaling on the scale which took place there. The development of whaling since 1945 supports the view that there are separate populations of Fin whales in the region. The numbers of this species have declined on the whaling grounds of the Faeroe Islands and western Norway, and possibly also of north Norway, but not on the Icelandic grounds where there is no evidence of overfishing.     

Evaluation of the productivity of walleye pollock generations in the northern Sea of Okhotsk

Based on data on the abundances of various age groups in the northern Sea of Okhotsk in 1984–2008, the productivity of 33 generations of walleye pollock born between 1975 and 2007 was evaluated in two ways. The first approach allowed a retrospective estimation by abundance of the first nine one-year age groups, and the second one was a perspective estimation using the abundance index of the nearest recruitment—3- and 4-year-olds—that enabled us to evaluate the productivity of a generation before it enters into spawning and commercial stocks. These productivity estimates were compared to the data of annual catches and the dynamics of spawning stock for many years. A high value of walleye pollock stock was shown to be supported by several productive and highly productive generations, a medium value—by one productive and one moderately productive or by two moderately productive generations, and a low value—by one productive, or moderately productive, and low productive generations. In addition, overall mortality rates were calculated for generations with various productivity levels. The greatest variability of mortality rates was observed in immature walleye pollock; the maximum mortality rate was typical for the recruitment of highly abundant generations, and the minimum, for the least abundant ones. The lowest mortality was recorded at the age of mass maturation. Mature individuals of generations with various productivity levels showed insignificant differences in overall mortality rates.     

Pre-whaling genetic diversity and population ecology in eastern Pacific gray whales: insights from ancient DNA and stable isotopes

Commercial whaling decimated many whale populations, including the eastern Pacific gray whale, but little is known about how population dynamics or ecology differed prior to these removals. Of particular interest is the possibility of a large population decline prior to whaling, as such a decline could explain the ~5-fold difference between genetic estimates of prior abundance and estimates based on historical records. We analyzed genetic (mitochondrial control region) and isotopic information from modern and prehistoric gray whales using serial coalescent simulations and Bayesian skyline analyses to test for a pre-whaling decline and to examine prehistoric genetic diversity, population dynamics and ecology. Simulations demonstrate that significant genetic differences observed between ancient and modern samples could be caused by a large, recent population bottleneck, roughly concurrent with commercial whaling. Stable isotopes show minimal differences between modern and ancient gray whale foraging ecology. Using rejection-based Approximate Bayesian Computation, we estimate the size of the population bottleneck at its minimum abundance and the pre-bottleneck abundance. Our results agree with previous genetic studies suggesting the historical size of the eastern gray whale population was roughly three to five times its current size.     

Characterization of 25 microsatellite loci in bowhead whales (Balaena mysticetus)

Bowhead whales (Balaena mysticetus) experienced a severe demographic population bottleneck caused by commercial whaling that ceased in 1914. Aboriginal subsistence whale harvests have continued and are managed by the International Whaling Commission. In an effort to provide management advice for bowhead whales, 25 microsatellite loci were isolated from genomic DNA libraries. This panel of markers will be utilized to analyse stock structure hypotheses of current bowhead whale populations.     

Seasonal and Geographic Variation of Southern Blue Whale Subspecies in the Indian Ocean

Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp) are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four “acoustic populations” occur. Three of these are pygmy blue whale (B.m. brevicauda) populations while the fourth is the Antarctic blue whale (B.m. intermedia). Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important habitat for blue whales. Presently little is known about the seasonal movements and degree of overlap of these four populations, particularly in the central Indian Ocean. We examined the geographic and seasonal occurrence of different blue whale acoustic populations using one year of passive acoustic recording from three sites located at different latitudes in the Indian Ocean. The vocalizations of the different blue whale subspecies and acoustic populations were recorded seasonally in different regions. For some call types and locations, there was spatial and temporal overlap, particularly between Antarctic and different pygmy blue whale acoustic populations. Except on the southernmost hydrophone, all three pygmy blue whale acoustic populations were found at different sites or during different seasons, which further suggests that these populations are generally geographically distinct. This unusual blue whale diversity in sub-Antarctic and sub-tropical waters indicates the importance of the area for blue whales in these former whaling grounds.     

Spatial patterns of humpback whale (Megaptera novaeangliae) sightings and survey effort: Insight into North Atlantic population structure

Understanding the population structure of a species is critical to its effective management and conservation. The humpback whale ( Megaptera novaeangliae ) has been the target of numerous research projects in several ocean basins, but no clear picture of its population structure has emerged. In the North Atlantic Ocean, genetic analyses and photo-identification movements have shown significant heterogeneity among the summer feeding grounds. Building on this knowledge, we test the hypothesis that the feeding grounds represent distinct populations by analyzing the spatial pattern of summer humpback whale sightings and survey effort. Controlling for the spatial pattern of effort, sightings are clustered, with peaks at radial distances of 300 km, 600 km, and 1,500 km. These results provide insight into the spatial extent of the summer population structure of humpback whales in the North Atlantic Ocean. Fine-scale clustering at distances of 300 km and 600 km is compatible with multiple populations consisting of the Gulf of Maine, eastern Canada, western Greenland, and Iceland. Broad-scale clustering at distances of 1,500 km may represent divisions between the western and eastern North Atlantic populations. These results provide spatial bounds to the feeding grounds of humpback whales and emphasize their distinct nature as management units.     

Global distribution of fin whales Balaenoptera physalus in the post‐whaling era (1980–2012)

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Evaluation of pulse fishing for the walleye, Stizostedion vitreum vitreum, in Henderson Lake, Ontario

A total of 3226 walleye were removed from Henderson Lake, Ontario over 3 years (1980–2), causing the stock to collapse. This removal tested the applicability of 'pulse' fishing as a management alternative, and also provided an opportunity to determine which population characteristics might be monitored to serve as predictors of stock collapse in this species.
Following initial exploitation, increased length at age occurred only within younger age-lasses. To use this response as a predictor, one must first obtain pre-exploitation length-at-age data through using the proper gear to sample small fish. Abrosov's mean age to mean age at maturity index may also forewarn of stress (1.2 critical t value for Henderson Lake), but poor recruitment usually invalidates this index, since the lower angling vulnerability of large fish biases mean age calculations. While annual production estimates were a good indicator of the collapse, their determination required much effort. Petersen population estimates produced much more realistic estimates of population size than Schumacher–Eschmeyer estimates, but both estimates not only require much effort but also are influenced by changes in recruitment.
Poor predictors of the walleye collapse included: catch-per-unit-effort data, which, while giving some idea of fish density, were not good indices of exploitation stress; condition factors, which were not correlated to fish abundance; fecundity increases, which suffered far too much of a retarded response in Henderson Lake to serve as a predictor of stock collapse. The inability to determine accurately sex ratios of measure recruitment made these parameters unless.
At least over the short term, neither northern pike nor white sucker populations have increased following the walleye collapse. As yet, walleye have not returned to their former abundance, so the operational usefulness of 'pulse' fishing remains an unknown.     

Increasing abundance of bowhead whales in West Greenland

In April 2006, a dedicated survey of bowhead whales (Balaena mysticetus) was conducted on the former whaling ground in West Greenland to determine the current wintering population abundance. This effort included a double platform aerial survey design, satellite tracking of the movements of nine whales, and estimation of high-resolution surface time from 14 whales instrumented with time-depth recorders. Bowhead whales were estimated to spend an average of 24% (cv=0.03) of the time at or above 2m depth, the maximum depth at which they can be seen on the trackline. This resulted in a fully corrected abundance estimate of 1229 (95% CI: 495-2939) bowhead whales when the availability factor was applied and sightings missed by observers were corrected. This surprisingly large population estimate is puzzling given that the change in abundance cannot be explained by a recent or rapid growth in population size. One possible explanation is that the population, which demonstrates high age and sex segregation, has recently attained a certain threshold size elsewhere, and a higher abundance of mature females appears on the winter and spring feeding ground in West Greenland. This in combination with the latest severe reduction in sea ice facilitating access to coastal areas might explain the surprising increase in bowhead whale abundance in West Greenland.     

Two Intense Decades of 19th Century Whaling Precipitated Rapid Decline of Right Whales around New Zealand and East Australia

Right whales (Eubalaena spp.) were the focus of worldwide whaling activities from the 16^th to the 20^th century. During the first part of the 19^th century, the southern right whale (E. australis) was heavily exploited on whaling grounds around New Zealand (NZ) and east Australia (EA). Here we build upon previous estimates of the total catch of NZ and EA right whales by improving and combining estimates from four different fisheries. Two fisheries have previously been considered: shore-based whaling in bays and ship-based whaling offshore. These were both improved by comparison with primary sources and the American offshore whaling catch record was improved by using a sample of logbooks to produce a more accurate catch record in terms of location and species composition. Two fisheries had not been previously integrated into the NZ and EA catch series: ship-based whaling in bays and whaling in the 20^th century. To investigate the previously unaddressed problem of offshore whalers operating in bays, we identified a subset of vessels likely to be operating in bays and read available extant logbooks. This allowed us to estimate the total likely catch from bay-whaling by offshore whalers from the number of vessels seasons and whales killed per season: it ranged from 2,989 to 4,652 whales. The revised total estimate of 53,000 to 58,000 southern right whales killed is a considerable increase on the previous estimate of 26,000, partly because it applies fishery-specific estimates of struck and loss rates. Over 80% of kills were taken between 1830 and 1849, indicating a brief and intensive fishery that resulted in the commercial extinction of southern right whales in NZ and EA in just two decades. This conforms to the global trend of increasingly intense and destructive southern right whale fisheries over time.     

Hybridization of Southern Hemisphere blue whale subspecies and a sympatric area off Antarctica: impacts of whaling or climate change?

Understanding the degree of genetic exchange between subspecies and populations is vital for the appropriate management of endangered species. Blue whales (Balaenoptera musculus) have two recognized Southern Hemisphere subspecies that show differences in geographic distribution, morphology, vocalizations and genetics. During the austral summer feeding season, the Antarctic blue whale (B. m. intermedia) is found in polar waters and the pygmy blue whale (B. m. brevicauda) in temperate waters. Here, we genetically analyzed samples collected during the feeding season to report on several cases of hybridization between the two recognized blue whale Southern Hemisphere subspecies in a previously unconfirmed sympatric area off Antarctica. This means the pygmy blue whales using waters off Antarctica may migrate and then breed during the austral winter with the Antarctic subspecies. Alternatively, the subspecies may interbreed off Antarctica outside the expected austral winter breeding season. The genetically estimated recent migration rates from the pygmy to Antarctic subspecies were greater than estimates of evolutionary migration rates and previous estimates based on morphology of whaling catches. This discrepancy may be due to differences in the methods or an increase in the proportion of pygmy blue whales off Antarctica within the last four decades. Potential causes for the latter are whaling, anthropogenic climate change or a combination of these and may have led to hybridization between the subspecies. Our findings challenge the current knowledge about the breeding behaviour of the world's largest animal and provide key information that can be incorporated into management and conservation practices for this endangered species.