Two allopatric forms of Bryde's whale off South Africa
01 Jan 1977-Iss: 1, pp 10-38
About: The article was published on 1977-01-01 and is currently open access. It has received 42 citations till now. The article focuses on the topics: Whale.
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TL;DR: Current data suggest that, of the various threats potentially affecting baleen whales, only entanglement in fishing gear and ship strikes may be significant at the population level, and then only in those populations which are already at critically low abundance.
Abstract: Most species of baleen whales were subject to intensive overexploitation by commercial whaling in this and previous centuries, and many populations were reduced to small fractions of their original sizes. Here, we review the status of baleen whale stocks, with an emphasis on those that are known or thought to be critically endangered. Current data suggest that, of the various threats potentially affecting baleen whales, only entanglement in fishing gear and ship strikes may be significant at the population level, and then only in those populations which are already at critically low abundance. The impact of some problems (vessel harassment, and commercial or aboriginal whaling) is at present probably minor. For others (contaminants, habitat degradation, disease), existing data either indicate no immediate cause for concern, or are insufficient to permit an assessment. While the prospect for many baleen whales appears good, there are notable exceptions; populations that are of greatest concern are those suffering from low abundance and associated problems, including (in some cases) anthropogenic mortality. These include: all Northern Right Whales Eubalaena glacialis, Bowhead Whales Balaena mysticetus of the Okhotsk Sea and various eastern Arctic populations, western Gray Whales Eschrichtius robustus, and probably many Blue Whale Balaenoptera musculus populations. We review the status of these populations and, where known, the issues potentially affecting their recovery. Although Humpback Whales Megaptera novaeangliae and Southern Right Whales Eubalaena australis were also heavily exploited by whaling, existing data indicate strong recovery in most studied populations of these species.
381 citations
TL;DR: The results suggest the existence of several recently diverged populations in the North Atlantic and Mediterranean Sea, possibly with some limited gene flow between adjacent populations, a population structure which is consistent with earlier population models proposed by Kellogg, Ingebrigtsen, and Sergeant.
Abstract: Samples were collected from 407 fin whales, Balaenoptera physalus, at four North Atlantic and one Mediterranean Sea summer feeding area as well as the Sea of Cortez in the Pacific Ocean. For each sample, the sex, the sequence of the first 288 nucleotides of the mitochondrial (mt) control region and the genotype at six microsatellite loci were determined. A significant degree of divergence was detected at all nuclear and mt loci between North Atlantic/Mediterranean Sea and the Sea of Cortez. However, the divergence time estimated from the mt sequences was substantially lower than the time elapsed since the rise of the Panama Isthmus, suggesting occasional gene flow between the North Pacific and North Atlantic ocean after the separation of the two oceans. Within the North Atlantic and Mediterranean Sea, significant levels of heterogeneity were observed in the mtDNA between the Mediterranean Sea, the eastern (Spain) and the western (the Gulf of Maine and the Gulf of St Lawrence) North Atlantic. Samples collected off West Greenland and Iceland could not be unequivocally assigned to either of the two areas. The homogeneity tests performed using the nuclear data revealed significant levels of divergence only between the Mediterranean Sea and the Gulf of St Lawrence or West Greenland. In conclusion, our results suggest the existence of several recently diverged populations in the North Atlantic and Mediterranean Sea, possibly with some limited gene flow between adjacent populations, a population structure which is consistent with earlier population models proposed by Kellogg, Ingebrigtsen, and Sergeant.
228 citations
TL;DR: A new species of Balaenoptera is described, characterized by its unique cranial morphology, its small number of baleen plates, and by its distant molecular relationships with all of its congeners.
Abstract: In the late 1970s eight Balaenoptera specimens of unknown identity were caught in the lower latitudinal Indo-Pacific waters by Japanese research whaling vessels1. The combination of the allozyme patterns and physical maturity of the eight specimens separated them from all acknowledged Balaenoptera species2. In September 1998 we collected a medium-sized baleen whale carcass on a coastal island in the Sea of Japan. This specimen and the previously collected eight specimens resembled Balaenoptera physalus (fin whale) in external appearance but were much smaller. Comparison of external morphology, osteology and mitochondrial DNA data grouped the nine specimens as a single species but separated them from all known baleen whale species. Therefore, here we describe a new species of Balaenoptera, which is characterized by its unique cranial morphology, its small number of baleen plates, and by its distant molecular relationships with all of its congeners. Our analyses also separated Balaenoptera brydei (Bryde's whale)3,4 and Balaenoptera edeni (Eden's whale)5 into two distinct species, raising the number of known living Balaenoptera species to eight.
165 citations
TL;DR: 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.
Abstract: 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 concen- trate in the Ligurian-Corsican-Provencal 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.
141 citations
TL;DR: This paper critically examines the nature and magnitude of the effects of these factors on organochlorine tissue loads in marine mammals and advice is provided about sampling and strategies for selection of variables that will improve the reliability of the comparisons between populations.
Abstract: ALEX AGUILAR* A-008, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92038 ABSTRACT Organochlorine pollutants are potentially useful for identifying discrete pop- ulations of marine mammals that overlap in geographic distribution However, many factors unrelated to geographical distribution may affect the chemical burden of individual animals or of entire population components even within a homogeneously distributed population These factors include, among others, nutritional state, sex, age, trophic level, distance of habitat from mainland and pollution source, excretion, metabolism, and tissue composition Sample storage and analytical methodology may also be an important source of variation These, and any other factors, must be identified and their effect ascertained before attempting any comparison between populations This paper critically examines the nature and magnitude of the effects of these factors on organochlorine tissue loads in marine mammals Pollutant concentrations can be strongly biased if carefully designed sampling regimes are not followed, but they are affected only moderately by sample treatment after collection Conversely, ratios between concentrations of compounds, such as the DDE/tDDT or the tDDT/PCB ratios, seem less dependent on sampling regime but more affected by storage, analytical procedures and ecological variations such as distance from pollutant source or trophic level Taking these effects into account, advice is provided about sampling and strategies for selection of variables that will improve the reliability of the comparisons between populations Key words: marine mammals, cetaceans, pinnipeds, pollutants, organochlorines, techniques, population discreteness, distribution, stock identity 1 Made while at the Southwest Fisheries Center, National Marine Fisheries Service, NOAA, Ia Jolla, California 92038, USA 2 Present address: Department of Zoology (Vertebrates), Faculty of Biology, University of Bar- celona, Barcelona 0807 1, Spain 242
107 citations