Cetaceans in British waters

Most information on the distribution, movements and ecology of cetaceans in the N.E. Atlantic have come from whale catches mainly in the early part of this century, and from strandings records collected by the British Museum (Nat. Hist.). With the formation of the Cetacean Group in 1973, a scheme for recording live cetaceans at sea was started. This paper summarizes the results of about two thousand sightings involving nearly 25,000 individual animals between the years 1958– 1978 (but mainly from the last 10 years), and relates them to existing information collected from other sources. Difficulties of identification and potential sources of bias are discussed. Most large cetaceans are present in British waters as part of a latitudinal feeding migration whereas smaller species may be present in the N.E. Atlantic throughout the year with movements being mainly of an offshore-inshore nature. Some species are clearly very rare probably as a result of over-exploitation in the last century and early part of this century. These include the Right whale, Blue whale and probably Humpback whale. Other species are rarely recorded because their usual range is some distance from British waters. These include narwhal and White whale (from Arctic waters), Pygmy sperm whale, smaller beaked whales and Euphrosyne dolphin (from warm temperate to tropical waters). The Harbour porpoise is by far the most common and widespread species in British waters, occurring mainly in inshore waters, although it has apparently declined in certain regions (e.g. Southern North Sea, English Channel, Irish Sea) in recent years probably as a result of pollution, disturbance and/or over-exploitation of food resources. Bottle-nosed and Risso's dolphins are also widely distributed close to the coast, although the latter is restricted to the west and south coasts and the former is associated particularly with some large estuaries. Common dolphins are relatively abundant and widespread, and are more pelagic than the previous three species. White-sided dolphins have a mainly pelagic distribution centred on the Northern North Sea whilst the White-sided dolphin has a wider distribution which includes all the western seaboard. Of larger cetaceans, the Killer whale is relatively common particularly on the west coasts and the Pilot whale is locally and seasonally abundant at the north and south ends of Britain and Ireland where they probably represent distinct populations. The Bottlenose whale, Minke, Fin and Sei whales are confined to the west and north coasts, all but the Minke whale having a primarily pelagic distribution. Sperm whales although increasingly commonly stranded on British coasts, are rarely sighted in inshore waters. The west coast of Britain and Ireland are the most important regions for cetaceans whereas the Southern North Sea has the smallest number although in previous decades numbers were probably higher. Most cetacean species occur mainly in the summer months, particularly August and September, although some species, e.g. White-sided Dolphin, Pilot whale and Minke whale show peaks later in the year. A number of species show secondary spring peaks, e.g. Bottle-nosed and Common dolphins, Risso's dolphins, and Pilot whales. Present evidence suggests that only the large whales exhibit definite latitudinal migrations, all other species being resident at high latitudes although they may show offshore-inshore or possibly small latitudinal movements. Many of the movements indicated from the present analysis can be linked to the seasonal changes in food availability and to the timing and geographical location of breeding, and these are described in detail. Many concentrations of a particular cetacean species occur regularly in the same area year after year and these may often be related to spawning concentrations of a particular fish species. Variations in herd size are noted between species and within species at different times of the year. These are related to aggregations associated with feeding, breeding, and long-distance movements winch will vary according to the biology and ecology of different cetacean species.     

Trends in the strandings of Cetacea on the British Coasts 1913-72

Records 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 fish.     

The recapture of British salmon in Irish waters

In the years 1972 to 1974, inclusive, a total of 50 salmon originally tagged as smolts in British rivers were recaptured in Irish waters. Although it is not possible to give precise reasons for these changes, some factors can be largely eliminated. The results do, however, indicate that salmon and grilse derived from British rivers occur in Irish inshore waters to a greater extent than was generally accepted.     

An analysis of maternal deaths in British Columbia: 1963 to 1970

There were 132 maternal deaths in British Columbia in the years 1963 to 1970. The mean maternal mortality rate for these eight years was 0.317. Sixty of these deaths (45.5%) were due to direct obstetrical causes. Indirect and nonrelated deaths accounted for 21.2 and 33.3% of the total, respectively. The most common causes of direct obstetrical deaths were hemorrhage, infection and vascular accidents, in that order; pre-eclampsia ranked a distant fourth. Ninety-five percent of direct obstetrical deaths were probably avoidable. Approximately 27% of all direct obstetrical deaths were abortion-related. Hemorrhage continues to be a major problem, in particular among the native Indian women of the province.If further reduction in maternal mortality is to be achieved, obstetrical hemorrhage must be better managed and deaths due to abortions reduced. Future studies should reveal if the liberalized abortion laws will assist in the realization of the latter goal.     

The distribution of the crayfish, Austropotamobius pallipes, in British waters

SUMMARY. The distribution of Austropotamobius pallipes , the only freshwater crayfish indigenous to the British Isles, is examined using over 300 records collected since 1970. The majority of records are for England where crayfish are found in areas associated with base-rich easily weathered substrata. Waters containing crayfish tend to be in the pH range 7–9, with calcium levels above 5 mg l⁻¹. Crayfish are found in a wide variety of habitats ranging from deep water-filled quarries with a soft substratum to shallow fast-flowing streams.     

Recent strandings and sightings of whale sharks in South Africa

Available information on whale shark strandings around the coast of South Africa during the period 1984–1995 was collated. Stranded animals ranged in size from 3–11 m TL, most were immature and the sex ratio was even. Aerial observations and sightings by divers indicate that whale sharks are most abundant in South African waters during the austral summer and autumn months. This revised version was published online in July 2006 with corrections to the Cover Date.     

The role of temperature and cannibalism in interannual recruitment variation of bass in British waters

Between-year variation in bass Dicentrarchus labrax year-class strength in southern British waters is investigated. Mean spring-summer seawater temperature in the year of birth was significantly positively correlated with both the level of summer recruitment of the 0 + group to the estuarine nurseries and subsequent recruitment of III + fish to the adult population. Spectral analysis of the temperature-compensated time series showed that a statistically significant proportion of the variation not attributable to temperature was periodic at 0–33 cycles year⁻¹. Therefore, a simple, three-parameter model, combining a linear relationship between temperature and abundance and a second-order autoregressive model can be used to describe and predict variation in relative adult YCS. Bass remain for their first 3 years within their estuarine nursery areas. As I + fish were observed in Southampton water to cannibalize the 0 + group, it is suggested that strong year-classes suppress recruitment for the next 2 years even if the temperature is suitable to promote a strong year-class. Cyclic variation in recruitment caused by intraspecific interactions, particularly cannibalism, may be a feature of other marine fish that use estuaries as nursery areas.     

Morphological analysis of threeInia (Cetacea: Iniidae) populations from Colombia and Bolivia

We present new morphological data on three Colombian and BolivianInia populations. Analysis of morphometric data strongly suggests thatInia are sexually dimorphic, with males smaller for several variables and more heterogeneous than females. Our morphological data supported that Colombian Amazon males had the greatest total body length as well as greatest fluke values (tip to tip) compared to the males from the Orinoco and Bolivia Rivers. There were also significant differences in females among populations. The two Colombian groups (Amazon and Orinoco basin) presented greater total body length than the Bolivian array, while distance from jaw tip to tip of dorsal fin was greater in the Orinoco basin females than in the other two populations. A Canonic Population Analysis showed that the confidence intervals of the Colombian Amazon and Orinoco males were partially superposed. However, the Bolivian male sample was remarkably differing from these two populations. Two long standing debates exist in the systematic literature onInia: (1) the number of extant species (one,Inia geoffrensis, or twoI. geoffrensis andI. boliviensis) and (2) the number of extant subspecies ofI. geoffrensis (I. geoffrensis geoffrensis, I. geoffrensis humboldtiana andI. geoffrensis boliviensis). Using recent collections of both molecular and morphometric data, we suggest the existence of two distinct species ofInia with no subspecific distinction amongI. geoffrensis populations.     

Incomplete lineage sorting impacts the inference of macroevolutionary regimes from molecular phylogenies when concatenation is employed: An analysis based on Cetacea

Interest in methods that estimate speciation and extinction rates from molecular phylogenies has increased over the last decade. The application of such methods requires reliable estimates of tree topology and node ages, which are frequently obtained using standard phylogenetic inference combining concatenated loci and molecular dating. However, this practice disregards population‐level processes that generate gene tree/species tree discordance. We evaluated the impact of employing concatenation and coalescent‐based phylogeny inference in recovering the correct macroevolutionary regime using simulated data based on the well‐established diversification rate shift of delphinids in Cetacea. We found that under scenarios of strong incomplete lineage sorting, macroevolutionary analysis of phylogenies inferred by concatenating loci failed to recover the delphinid diversification shift, while the coalescent‐based tree consistently retrieved the correct rate regime. We suggest that ignoring microevolutionary processes reduces the power of methods that estimate macroevolutionary regimes from molecular data.