Shetland Waters Research Articles

Previously Undocumented Long-Finned Pilot Whale (Globicephala melas) Placental Expulsion in Coastal Waters of Shetland, United Kingdom

Previously Undocumented Long-Finned Pilot Whale (Globicephala melas) Placental Expulsion in Coastal Waters of Shetland, United Kingdom

The macro-and megabenthic fauna on the continental shelf of Prydz Bay, east Antarctica

Ten triangle trawls in Prydz Bay were collected from 97 m to 638 m. A total of 206 species of macro- and mega-benthos were identified, belonging to 9 phyla and 118 families, of which pycnogonids (41 species), gammarid amphipods (38 species) and echinoderms (36 species) were the most dominant groups. The species richness per station varied from 1 to 92. The abundance of macro- and mega-benthos (1 × 10−3-0.24 Ind./m2) was low, compared to that in the southeastern Weddell Sea (131–1.28 × 103 Ind./m2) and South Shetland waters (160–4.38 × 103 Ind./m2). The results were similar to the Amundsen Sea abundances (1.10 × 10−3-0.40 Ind./m2) at comparable depths and in the Antarctic deep sea. The macrobenthic community had 2 types, Sessile Suspension Feeders with Associated fauna - dominated by sponges (SSFA-SPO) and mobile deposit feeders, infauna and grazers - epifauna dominated (MOIN-EPI). The macrobenthic community in Prydz Bay showed a dispersed patchy distribution pattern which may result from the Antarctic water mass and iceberg scouring.

Identification of Environmental Factors that Influence the Upstream Migration of Sea Trout Salmo trutta in Shetland Waters

Migrating sea trout Salmo trutta L. in the waters of the Shetland Islands (UK) were once found in abundant numbers but they have been in decline since the mid-1980s. Therefore, it is becoming ever more critical to investigate sea trout behaviour with respect to the prevailing environmental conditions in the unique Shetland habitat so that we can determine how this prized and important species might be re-established to more sustainable levels. Here, during a period of four months (July to October) in 2015, environmental and fish catch rate data were collected for a small sample size of sea trout caught at six Shetland locations. We then looked for trends and correlations in the data that might help account for the migratory behaviour of the fish with respect to the environmental conditions at the time of capture. Our data showed that wind speed and pH correlated to the catch rate. However, no significant correlation was found between the water temperature, air temperature, barometric pressure, or humidity, and catch rate. Multivariate regression showed that wind speed and pH explained 26.3% of the variance in the catch rate. The sex ratio of the sea trout caught was skewed towards females at a ratio of 4.7 : 1.0 and the largest trout caught were all female. Recording biological data and understanding the migration patterns and behaviours of the remaining wild populations of sea trout are important for optimizing management plans to support current efforts to increase the numbers of this valuable anadromous species in Shetland waters.

Timing of hatching inAmmodytes marinus from Shetland waters and its significance to early growth and survivorship

The significance of hatch date for the growth and survival of the sandeel,Ammodytes marinus, was investigated using otolith microstructure. Hatch dates of 2 to 6 mo-old juvenileA. marinus caught near Shetland were compared between 1990 and 1992, during which period year-class strength varied by more than an order of magnitude. The hatch-date distribution of juveniles in the 1992 year-class was compared with that estimated directly from the abundance of newly emerged larvae on the spawning grounds. The extent of larval hatching periods in 1990 and 1991 was also estimated from continuous plankton-recorder data. There were significant differences in hatching periods between all three years, hatching in 1990 and 1992 being markedly earlier than the long-term mean peak in hatching indicated from archival data. Most individuals from the 1991 year-class attained a larger size by July than those in other year-classes, despite hatching later. Variation in individual growth rates both within and between year-classes indicated that there was a seasonal cycle of growth opportunity in all years investigated. The study suggests that the degree of coupling between hatching and the onset of spring secondary production may be an important contributory factor to year-class variability in this species.

Effects of oil-industry operations on the macrobenthos of Sullom Voe

SynopsisThe aims, methods and techniques of the macrobenthic monitoring programme in Sullom Voe and Orka Voe are described together with an analysis of the data obtained from surveys that began in 1978 and continue to the present. The distribution of the benthic macrofauna is discussed in relation to the sedimentological and hydrocarbon data obtained and compared with data from other Shetland waters. The macrofauna is considered to be typical of five of the six Facies used to describe the communities of the voes around Shetland. The possible effects of the terminal operations on the macrofauna are assessed and it is concluded that the disturbance noted to the macrofauna in Garths Voe, close to the diffuser at Calback Ness and in Orka Voe, essentially follows the same pattern seen in modifications to Shetland macrofauna that occurs where naturally occurring organic carbon enrichment exists.

The monitoring of breeding seabirds and eiders

Twenty-one species of seabirds breed regularly in Shetland, some of them in huge, spectacular, multi-species colonies on cliffs. The Sullom Voe Environmental Advisory Group Environmental Impact Statement (SVEAG 1976) provides a table showing the relative importance of seabird species in terms of Scotland and the British Isles. We have updated these data in the light of the Seabird Colony Register (Lloyd et al. 1991) and present data for seven species, vulnerable to oil pollution, in Table 1. It is clear that these populations are of national importance and indeed several are internationally important. Separately, an estimate was provided by SVEAG of the numbers of sea ducks and divers wintering in Shetland waters and updated estimates are given by Suddaby (1992) (Table 2). Chief among these is the eider duck (Somateria mollissima) which is apparently resident in Shetland throughout the year (Heubeck 1993a). In its Eighth Report, on Oil Pollution at Sea, the Royal Commission on Environmental Pollution (1981) recognised the vulnerability of seabirds to oil pollution and this was clearly a matter of concern in Shetland and elsewhere when the flow of enormous quantities of crude oil into Sullom Voe via undersea pipelines and out of Sullom Voe by large tankers became a reality. The risk to seabirds of oil pollution is well documented (Bourne 1968; RSPB 1979). Dunnet (1974, 1980, 1982, 1987) has reviewed the situation in relation to the North Sea oil industry.

Shetland beached bird surveys: national and European context

SynopsisA Shetland-wide beached bird survey was established in March 1979 and monthly surveys have continued since. This paper presents results from March 1979 to December 1992 during which time a total of 34 320 corpses of seabird and seaduck were found, of which 34023 (99.1%) were specifically identified. Corpses of guillemot (8911), fulmar (8707), kittiwake (4421), herring gull (2264), shag (1843) and great black-backed gull (1785) comprised 82.1% of the identified total, the remainder being made up of 31 other species. The relationship between the numbers of each species found, and their numbers and occurrence in Shetland waters is discussed. A total of 2781 corpses were judged to have been oiled before their deaths, of which 2732 (98.2%) were specifically identified. The six species most frequently found oiled were guillemot (1170 corpses), fulmar (543), kittiwake (184), razorbill (131), puffin (111) and shag (99).Variations in both the percentage of corpses found that were oiled, and the number of oiled corpses found per kilometre of beach surveyed, are examined and discussed. Comparison is made with results from beached bird surveys elsewhere in the British Isles and in other countries bordering the North Sea. In some species, notably the pelagic auks, there was considerable annual variation in the numbers of unoiled corpses found while in other species the number of unoiled corpses found changed more gradually over the 14 years. Reference is made to similar changes observed in other beached bird surveys and possible reasons for these changes are discussed.

The influence of food supply on the breeding ecology of Kittiwakes Rissa tridactyla in Shetland

We measured the breeding performance, body condition, time budgets and foraging ranges of Kittiwakes Rissa tridactyla at Sumburgh Head, Shetland, in two years of contrasting food availability. Kittiwakes in Shetland generally feed their young almost entirely on sandeels, and fisheries data indicated that stocks of sandeels in Shetland waters were at least ten times higher in 1991 than in 1990. Fledging success of Kittiwakes was nil in 1990 and 68% of eggs laid in 1991, although clutch‐size and hatching success were no different between years. Post‐hatching foraging trips in 1991 were of comparable duration to those recorded at other colonies in conditions of good food supply (2–3 h), while trips recorded during incubation or post‐hatching in 1990 were approximately three times longer on average than at corresponding stages of the breeding season in 1991. Radio‐tracking data indicated that adults generally stayed within 5 km of the colony in 1991 but flew more than 40 km from the colony on each trip in 1990. Eggs were apparently not left unattended in either year, despite the fact that this required adults to incubate for periods in excess of 44 h in 1990. The extent to which adults were able to increase trip durations, foraging ranges and incubation shift lengths between years, while maintaining hatching success, indicates the degree to which Kittiwakes are normally buffered against adverse feeding conditions during incubation. Reduced nest attendance and lower body‐condition of adults post‐hatching in 1990, in conjunction with complete post‐hatching breeding failure, indicate that adults were beyond the limits of their buffering capacity during chick‐rearing in 1990.

The effects of changes in food availability on the breeding ecology of great skuas Catharacta skua in Shetland

Great skuas on Foula, Shetland have responded to a decline in the availability of sandeels since the late 1970s by increasing the proportion of other items in their diets. This change is correlated with the annual recruitment of sandeels in Shetland waters. Since 1983 there has been a 10‐fold increase in predation by great skuas upon other seabirds, as Furness & Hislop (1981) suggested might occur in response to a low availability of sandeels. Changes in diet have been accompanied by a 50% reduction in adult territorial attendance as adults increased their foraging effort, such that between 1987 and 1989 breeding adults were probably working as hard as they were able to. Despite this, breeding success was less than 40% in 1987 and less than 15% in 1988 and 1989. The major cause of breeding failure was predation of unguarded chicks by adults from neighbouring territories. The willingness of adults to expose their chicks to high predation risk is probably maintained because of a positive correlation between chick pre‐fledging growth and post‐fledging survival, which is expressed up to the age of two years and which will place a strong pressure upon adults to feed their chicks as well as possible. The high expenditure of effort by adults in 1987 and 1988 did not affect the weights of those birds incubating eggs in 1988 and 1989, but there was a slight (3%) decrease in egg size between the late 1970s and the late 1980s. Changes in the age structure of the breeding population and the absence in 1989 of 28% of adults colour‐ringed during incubation in 1988 suggest an increase in the rate of egress since the 1970s. These changes probably represent an increase in the long‐term costs of reproduction to adults at this colony.

The fresh waters of Shetland: Chemical characteristics of running waters

The water chemistry of 48 streams on Shetland was determined as part of a synoptic survey of the islands during 1974. Principal component analysis identified three main contributors to stream chemistry: solid geology, drift geology (in the form of peat) and marine influence. The sites could be clustered by their chemistry according to these factors. The likely chemical characteristics of sites could be predicted from map analysis of altitude, solid and drift geology and oceanicity. There was little evidence of acidification of Shetland streams, but the peatiness of the water made acidification difficult to detect using the usual criteria. Most sites did show a reduction in alkalinity compared to a calculated value for non-aidified sites.

The fresh waters of Shetland

The fresh waters of Shetland

The fresh waters of Shetland: I. The strategy of a synoptic resource analysis

Abstract This account describes the strategy of a synoptic ecological survey of the fresh waters of Shetland — one of a series of regional studies in synoptic limnology. Desk analyses of the total freshwater resource show that there are 1596 standing waters and 3026 running waters on these geologically complex islands. Most of the waters are small and at low altitude: many are concentrated in certain areas. All waters are close to the sea. Multivariate analyses of map attributes for each water were used to divide the lochs and streams into groups which provided the strata from which 65 lochs and 54 streams were randomly selected for the field investigations described in other papers in this series.

The fresh waters of Shetland

The fresh waters of Shetland

The fresh waters of Shetland: II resources and distribution

Abstract A count of the total number of fresh waters in the Shetland Islands, as depicted on Ordnance Survey 1:63,360 scale maps, is given. Standing waters are classified by surface area and running waters by stream order value. Loch altitude and stream slope information is described, also their spatial distribution throughout the islands. The runoff characteristics of Shetland are discussed and a comparison of the numbers of fresh waters in Shetland is made with those in other areas of Great Britain.

Structures of Swarming and Dispersed Populations of Krill (Euphausia Superba) in Scotia Sea and South Shetland Waters During January-march 1981, Determined by Bongo Nets

ABSTRACT Through much of the Scotia Sea and near the South Shetland Islands during 24 January–-23 March 1981, the RV Melville made extensive bongo net collections of zooplankton, including krill, Euphausia superba. Length-frequency distributions of juvenile and adult krill are studied here. An eastern population in the Scotia Sea was distinguishable by a 35 mm, nonreproductive mode, and a western population by a 35 mm and 55 mm reproductive bimodal distribution. One swarm was encountered in each subregion. Most catches indicated relatively dispersed krill. Elsewhere, in the Bransfield Strait and near Elephant Island, population length-frequency structures were more complex, indicating mixtures of age groups of different origins. A midMarch swarm located acoustically in Bransfield Strait was dominated by Year-2 krill of 30–-45 mm, with a unique minor mode at 14-22 mm and a secondary mode centered upon 50–-53 mm adults. Around Elephant Island, two kinds of size distributions, largely separate in space, characterized generally abundant krill: (1) a 50-55 mm mode wherein adult males predominated, and (2) a modeless 30-50 mm range wherein females predominated. During 7-8 March, a dense swarm occupying 150 km2 consisted of two partially overlapping segments, each having one of the two length-frequency structures. Biomass of the swarm was estimated at 47,200 metric tons, based on bongo net samples. During 20-23 March, dominance by 50-55 mm males prevailed; swarms were then particularly associated with the 150-160 m bathymetric interval. Circumstantial evidence of selective effects of intensive trawling by an industrial fleet is seen in relatively low densities of Year-2 krill in places where trawling had taken place, resulting in domination by Year-3 krill. The possibility that the population in which 50-55 mm adults dominated is a natural result of advection is also considered, but not resolved.

The fresh waters of Shetland: Physical and morphometric characteristics of lochs

SUMMARY. 1. Basic physical and morphometric data are presented for sixty‐five lochs on the Shetland Islands. The interrelations between loch dimensions are comparable to those recorded elsewhere in Scotland, but the smaller lochs on Shetland tend to be somewhat shallower, and the large lochs somewhat deeper than usual.2. The results of a multivariate analysis show that most of the physical variables measured in the field are closely correlated with easily measured map attributes.

Seals in Shetland waters

SynopsisThe distribution and status of grey and common seals around Shetland is reviewed. Recent surveys have produced an accurate picture of the location of breeding sites, grey seals being found at discrete localities mainly in the north and west of the islands and common seals being distributed more widely throughout the archipelago. The population of grey seals is estimated at 3,500 animals and is considered to be relatively constant. The reliability of boat surveys for estimating common seal populations is discussed. It is concluded that the population of Shetland has increased in numbers following protective legislation and it is suggested that there has also been a change in hauling out behaviour. The current population consists of at least 4000 individuals.Grey seals do not appear to have been affected by oil developments at Sullom Voe so far, but common seal numbers in the Sullom Voe area have not increased at the same rate as elsewhere in Shetland, and the number of pups present has declined. It is suggested that these changes may have arisen as a result of the development of the oil terminal. Study methods which would enable the nature and causes of these changes to be identified are proposed.

Biogenic carbonate sediments on the Scottish continental shelf and on Rockall Bank

Biogenic carbonate sediments on the Scottish continental shelf and on Rockall Bank (northeast Atlantic) are largely composed (in the fraction > 2 mm) of bivalve fragments, serpulid tubes (attached forms and Ditrupa arietina), barnacle plates, and bryozoans. Other components include fragments from regular and irregular echinoids, and from articulate and inarticulate brachiopods. In inshore Shetland waters, barnacles and attached serpulids are the dominant components, while west of Orkney and west of the Outer Hebrides bivalves tend to be dominant. On the outer shelf the polychaete Ditrupa may be the dominant component. On Rockall Bank bryozoans are the dominant components in the shallow waters close to Rockall Island and on Bryony Bank. Elsewhere bivalves are generally the dominant component. Radiocarbon dating indicates that these shell gravels are of Holocene age. In broad general terms, the faunal composition of these gravels can be related to local living faunas.

A bowl-like object of aragonite-limestone from Shetland waters

A bowl-like object recovered from the sea-bed off Shetland at approximately 60° 30' N., 0° 55' W. under 110 to 120 m. of water, is of problematical nature. It is pale grey, approximately conical, 33 × 30 cm. at the open end, 26 cm. high, with a suggestion of a foot. It is composed of a porous silty or sandy, apparently sedimentary, micaceous aragonite-limestone, containing numerous heavy mineral grains. The wall, 2 to 4 cm. thick, is irregular, with protuberances mainly on the inside. There is a plentiful microfauna, and apart from one specimen of Coccolithus, of Cenomanian age, it is entirely post-Glacial, probably modern. Some other objects are briefly discussed which may be similar or have a bearing on the origin of the Shetland ‘bowl’. There is some evidence of recrystallisation and it is suggested that the object, deposited as a calcareous mud off a metamorphic terrain (which Shetland is), may be the relic of a solution pipe, perhaps related to the submergence of te nearby coast.

The plerocercoid of Gilquinia squali Fabricius, 1794

Unidentified helminth larvae in the eyes of the North Sea whiting, Gadus merlangus L., were recorded in an unpublished survey of parasites of gadoid fish by Dr Z. Kabata of the Marine Laboratory, Aberdeen, in 1957. Since then these larvae have been observed frequently and during the first 6 months of 1964 an effort was made to identify them. They proved to be the plerocercoids ofa trypanorhynch cestode.The plerocercoids are usually free in the aqueous or vitreous humour, but occasionally one is found attached to the lens. Very often both eyes of the same fish are infested, the largest number of larvae recorded from one eye being ten, from a fish taken in Shetland waters. The other eye of the same fish contained eight larvae.In several plerocercoids examined the proboscides were evaginated, thus enabling detailed drawings to be made of the armature at a magnification of × 900. A number of specimens were fixed in Gilson's fixative; transverse and longitudinal sections were cut and stained with Mallory's triple stain; whole mounts were stained with borax carmine.Early larval stages are completely undifferentiated; they develop, later, to the stage shown in Fig. 1. A plerocercoid with a fully developed scolex measures 3·5–8·0 mm long by 0·7–1·6 mm broad.The larva is composed mainly of faintly staining tissue resembling the parenchyma of adult cestodes. The scolex is withdrawn into a cavity, the receptaculum scolecis, in the anterior half of the plerocercoid. At the anterior extremity is a deep invagination from which, in early larval stages, the receptaculum scolecis begins to develop.