中国沿岸小型鲸类误捕情况的调查

报道了１９９４ ～１９９５ 年对中国沿岸小型鲸类误捕情况的调查结果．调查表明,有误捕记录的小型鲸类主要有５ 种,即江豚（ Ｎｅｏｐｈｏｃａｅｎａ ｐｈｏｃａｅｎｏｉｄｅｓ） 、长喙真海豚（ Ｄｅｌｐｈｉｎｕｓ ｃａｐｅｎｓｉｓ） 、瓶鼻海豚（ Ｔｕｒｓｉｏｐｓｔｒｕｎｃａｔｕｓ） 、点斑原海豚（Ｓｔｅｎｅｌｌａ ａｔｔｅｎｕａｔａ） 和伪虎鲸（ Ｐｓｅｕｄｏｒｃａ ｃｒａｓｓｉｄｅｎｓ） ,其中以江豚的误捕率最高．１９９４ 年在山东、浙江、福建、广东、海南省和广西壮族自治区沿岸渔业误捕的小型鲸类约３０４５ ±２１２０ 头,其中江豚的误捕量约２１３２ ±１４８４ 头．误捕小型鲸类的渔具主要有拖网、刺网和张网．中国沿岸没有专门捕鲸的渔业方式．误捕的小型鲸类在沿岸居民的生活中不占重要地位,它们大部分被丢弃或廉价出售．目前尚不知道误捕对中国水域小型鲸种群影响的程度,但可能是造成数量下降原因之一．     

ELECTROPHYSIOLOGICAL MEASURES OF AUDITORY PROCESSING IN ODONTOCETES

ABSTRACT

The preponderance of our knowledge concerning hearing in the Cetacea has come from psychophysical studies. The most widely used alternative to psychophysical studies are neurophysiological studies utilizing auditory evoked potentials (AEPs). Due in part to the hypertrophy of auditory structures exhibited by the Cetacea, AEPs are highly robust and rapidly and easily obtained. Moreover, because AEPs reflect the synchronized activity of large neuronal assemblies, they offer a high level window onto auditory processing and allow for across-species comparison of responses.

Recent studies utilizing AEP techniques have demonstrated that the cetaceans have extremely high temporal resolution with integration times in the order of 300 msec. Remarkably, these animals also exhibit extremely sharp frequency tuning with auditory filters having Q10 of 20–30.     

PYGMY SPERM WHALES KOGIA BREVICEPS IN THE NORTHEAST ATLANTIC: NEW INFORMATION ON STOMACH CONTENTS AND STRANDINGS

Little is known about the feeding ecology of pygmy sperm whales ( Kogia breviceps ) in the Northeast Atlantic. Results are presented on the stomach contents of five whales stranded on the Galician coast (NW Spain) between 1995 and 2002 and seven whales stranded on the French Atlantic coast between 1984 and 2001. These results are compared with those obtained from the stomach contents of two pygmy sperm whales (a pregnant female and her calf ) stranded on the Scottish (UK) coast in 1999, the first records of the species in Scotland. In 13 out of 14 cases, food remains consisted almost entirely of cephalopod beaks, although some crustacean and fish remains were also present. In all the Spanish specimens, the identified prey were oceanic species: the cephalopods Histioteuthis reversa , H. bonnellii , Todarodes sagittatus , the viperfish Chauliodus sloani , and the giant mysid Gnatophausia sp. The same cephalopod species were found in the stomachs of the whales stranded in Scotland, although both whales had also consumed neritic cephalopod species such as Rossia macrosoma and other sepiolids. In the French specimens, almost all prey identified were oceanic cephalopods ( H. reversa , Brachioteuthis riseii , T. sagittatus , Taonius pavo , etc. ), but remains of crustaceans and a neritic squid ( Loligo forbesi ) were also found. One whale from France had eaten mainly Henslow's swimming crab ( Polybius henslowi ). Results from the present study are consistent with those found by other authors in the Azores and the Canary Islands in that pygmy sperm whales appear to be mainly teuthophagous, with histioteuthid squids forming an important part of the diet. Strandings records suggest that occurrence of pygmy sperm whales in the NE Atlantic may be seasonal, with most strandings occurring in autumn and winter.     

Gray whale Eschrichtius robustus population and stock identity

• 1 In response to conservation and management concerns about gray whale Eschrichtius robustus population and stock structure, we provide an overview of the life history and ecology of gray whales as a context for discussion of population and stock structure within the species. Historically eastern and western North Pacific gray whales were managed separately because: (i) their ranges do not overlap; (ii) genetic analyses indicate that the two populations are significantly different; and (iii) eastern gray whales have increased in abundance over the past century while western gray whales have not.
• 2 Here, we review gray whale migration timing and segregation, feeding and prey species, and reproduction and reproductive behaviour. For the eastern and western gray whale, we review their distribution, history of exploitation, abundance and current status, although most of what is known is founded on the better studied eastern gray whale and only implied for the lesser known western gray whale. Methods to investigate population and stock identity are reviewed including genetics, morphology, chemical signatures, carbon isotopes, parasites, photographic identification and trends in abundance.
• 3 While the evidence indicates that there is at least some degree of mixing within each of the gray whale populations, no stocks or sub‐stocks can be defined. Population structure is not evident in nuclear data, and because selection occurs primarily on the nuclear genome, it is unlikely that there is structuring within each population that could result in evolutionary differences. For western gray whales, there are insufficient data to assess the plausibility of stock structure within the population, owing to its extremely depleted state. Research on eastern gray whales has focused mostly on documenting changes in abundance, feeding biology and behaviour, and suggests separate breeding groups to be unlikely. Both males and females are promiscuous breeders lending little opportunity for the nuclear genome to be anything other than well mixed as is suggested by the high haplotypic diversity of the eastern population.
• 4 The available data strongly indicate that western gray whales represent a population geographically isolated from eastern gray whales and therefore that the western and eastern populations should be treated as separate management units.

     

Tetranucleotide microsatellite loci from the striped dolphin (Stenella coeruleoalba Meyen, 1833)

Five tetranucleotide microsatellite loci were isolated from the striped dolphin (Stenella coeruleoalba). Characterization of these loci revealed between three and 11 alleles at each locus and observed heterozygosity ranged from 0.192 to 0.775. All sets of primers amplified homologous loci when tested on four related species and showed polymorphisms in most locus–species combinations. A sixth microsatellite, which appeared to be monomorphic in the striped dolphin, was also shown to be polymorphic in three related species.     

THE EVOLUTIONARY HISTORY OF CETACEAN BRAIN AND BODY SIZE

Cetaceans rival primates in brain size relative to body size and include species with the largest brains and biggest bodies to have ever evolved. Cetaceans are remarkably diverse, varying in both phenotypes by several orders of magnitude, with notable differences between the two extant suborders, Mysticeti and Odontoceti. We analyzed the evolutionary history of brain and body mass, and relative brain size measured by the encephalization quotient (EQ), using a data set of extinct and extant taxa to capture temporal variation in the mode and direction of evolution. Our results suggest that cetacean brain and body mass evolved under strong directional trends to increase through time, but decreases in EQ were widespread. Mysticetes have significantly lower EQs than odontocetes due to a shift in brain:body allometry following the divergence of the suborders, caused by rapid increases in body mass in Mysticeti and a period of body mass reduction in Odontoceti. The pattern in Cetacea contrasts with that in primates, which experienced strong trends to increase brain mass and relative brain size, but not body mass. We discuss what these analyses reveal about the convergent evolution of large brains, and highlight that until recently the most encephalized mammals were odontocetes, not primates.     

Isolation by environmental distance in mobile marine species: molecular ecology of franciscana dolphins at their southern range

The assessment of population structure is a valuable tool for studying the ecology of endangered species and drafting conservation strategies. As we enhance our understanding about the structuring of natural populations, it becomes important that we also understand the processes behind these patterns. However, there are few rigorous assessments of the influence of environmental factors on genetic patterns in mobile marine species. Given their dispersal capabilities and localized habitat preferences, coastal cetaceans are adequate study species for evaluating environmental effects on marine population structure. The franciscana dolphin, a rare coastal cetacean endemic to the Western South Atlantic, was studied to examine these issues. We analysed genetic data from the mitochondrial DNA and 12 microsatellite markers for 275 franciscana samples utilizing frequency‐based, maximum‐likelihood and Bayesian algorithms to assess population structure and migration patterns. This information was combined with 10 years of remote sensing environmental data (chlorophyll concentration, water turbidity and surface temperature). Our analyses show the occurrence of genetically isolated populations within Argentina, in areas that are environmentally distinct. Combined evidence of genetic and environmental structure suggests that isolation by distance and a process here termed isolation by environmental distance can explain the observed correlations. Our approach elucidated important ecological and conservation aspects of franciscana dolphins, and has the potential to increase our understanding of ecological processes influencing genetic patterns in other marine species.     

A simple new algorithm to filter marine mammal Argos locations

During recent decades satellite telemetry using the Argos system has been used extensively to track many species of marine mammals. However, the aquatic behavior of most of these species results in a high number of locations with low or unknown accuracy. Argos data are often filtered to reduce the noise produced by these locations, typically by removing data points requiring unrealistic swimming speeds. Unfortunately, this method excludes a considerable number of good‐quality locations that have high traveling speeds that are the result of two locations being taken very close in time. We present an alternative algorithm, based on swimming speed, distance between successive locations, and turning angles. This new filter was tested on 67 tracks from nine different marine mammal species: ringed, bearded, gray, harbor, southern elephant, and Antarctic fur seals, walruses, belugas, and narwhals. The algorithm removed similar percentages of low‐quality locations (Argos location classes [LC] B and A) compared to a filter based solely on swimming speed, but preserved significantly higher percentages of good‐quality positions (mean ± SE% of locations removed was 4.1 ± 0.8%vs. 12.6 ± 1.2% for LC 3; 6.8 ± 0.6%vs. 15.7 ± 0.9% for LC 2; and 11.4 ± 0.7%vs. 21.0 ± 0.9% for LC 1). The new filter was also more effective at removing unlikely, conspicuous deviations from the track's path, resulting in fewer locations being registered on land and a significant reduction in home range size, when using the Minimum Convex Polygon method, which is sensitive to outliers.     

Body mass and food intake in captive,breeding bottlenose dolphins,Tursiops truncatus

Body mass (BM) was recorded regularly during pregnancy in four female Indian Ocean bottlenose dolphins (Tursiops truncatus). Daily food intakes were recorded for each animal before and after parturition. BM increase occurred variably between 2 and 5 months of gestation, and at parturition mass increases averaged 41.2% of initial prepregnancy mass. Changes in mass can thus be used as an early indicator of pregnancy. During the 12 months of pregnancy, no significant changes occurred in the amount of food ingested compared with previous years. Daily food intake during lactation (X = 13.2 kg, 8% of BM) proved significantly higher (P < 0.001) than during pregnancy (X = 8.7 kg, 5.2% of BM).