ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00195.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractAn analysis is carried out of all documented sightings of cetaceans in British waters between 1950–1975, received by the Cetacean Group. Two major problems which must be taken into account in such an analysis are difficulties of specific identification and bias from uneven coverage.The results show that porpoises are present in coastal waters for much of the year. The pattern of movements for this species is rather confused. Most dolphin species show peak numbers in summer, earliest in the north of Britain and later further south. Risso's dolphins may enter British waters rather earlier in spring than other species. Killer whales occur off the west coast of Britain and Ireland mainly between June‐September. Pilot whales are seen in North Britain at most times of the year but otherwise enter British waters along the west coast in spring. Bottle‐nosed whales and the larger whale species, including the Rorquals, are found only on the north and west coasts in summer and early autumn. For all species, herd size increases at the same time as increase in the numbers of sightings reported. Different species have different herd sizes with the largest occurring amongst porpoise and all dolphin species except Risso's dolphin, and the smallest amongst the large whale species. Herds may be accompanied by young individuals in spring‐late summer, depending on the

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00196.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractRecords of Cetacea stranded on the British coasts have been maintained in the British Museum (Natural History) since they were started in 1913. Investigations have now been made into the possibility of trends of developments in these strandings. The data have been arranged in groups appertaining to 5‐year periods for all species combined, round the entire British coastline, also in relation to the coast on which the animals were stranded. For this purpose the coast of Great Britain has been divided into three separate areas. In addition, three species have been selected and treated separately to demonstrate the different trends.The frequency of strandings appear to be correlated with the abundance of food fish, this in turn being related to the planktonic and nutritional values of the sea. There are one or two exceptions to this hypothesis, and it is suggested that there may be a correlation between an increase in strandings and a high mortality rate due to a lack of food fis

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00197.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractModern 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

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00198.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00199.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe history of whaling is very largely one of repeated over‐exploitation of the various whale stocks which became available through discovery or technological advance. Modern whaling has similarly caused considerable reductions in the numbers of some species in the major whaling grounds.Stock assessment methods are based on catch and effort statistics, biological information including age and reproductive status, marking and sightings records.Catch effort data have to be used with caution, because of changes in species preference, shifts in the whaling grounds and national fleet variations. With allowance made for these factors, cumulative catches adjusted for recruitment can be used to estimate the initial stock number. Changes in stock density after known catches also lead to abundance estimates. Logarithmic regression of age composition data are used to find the total mortality rates. The natural mortality can be estimated from early season catches in a fishery or pre‐fishery year classes caught more recently; fishing mortality is found by subtraction, which again leads to abundance estimates. Mathematical approaches incorporating recruitment estimates from actual age composition data and theoretical population models have been employed. Additional estimates come from mark release‐recapture experiments and direct sightings counts from whaling vessels and research ships. The latter are the only means of estimating the protected species.The yields which the various stocks can sustain are calculated from direct observations and theoretical considerations of the changes in recruitment, largely due to increased pregnancy rates and the lower ages at sexual maturity which occur in exploited stocks.The results of all the available analyses have been compared and combined to produce the population estimates and yields tabulated. The object of whale management is to bring all stocks to the levels providing the maximum or optimum sustainable yields. These are defined in terms of numbers at the moment, but may be expressed as biomass in the f

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00200.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractDespite the difficulties of exact observations at sea, it is clear that there are variations in the composition of herds even within the same species. In general, mixing of species is not unusual in herds, whether feeding or in transit, though smaller animals may consort with others of their own size and show fear of larger ones. Baleen whales or even ships may be accompanied by dolphins while in movement, and some species will remain with a stationary vessel while others go past. We have no evidence whether this relates to the relative size of cetacean or vessel, or anything other than the normal behaviour of the species under herding conditions.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00201.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1976.tb00202.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY