Pacific oysters,Crassostrea gigas,established in Scotland

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Trophic status of rivers in the Forth catchment,Scotland

1. An increase in nutrient concentrations in fresh water may pose a threat to water quality, biodiversity, and the uses to which these resources are subject. Compared with standing waters, the trophic status of running water has been neglected with few studies describing the extent of eutrophication in rivers. 2. This paper uses a range of information, including chemical analysis, subjective measures of algal abundance, and professional assessments to describe the trophic status of rivers in the Forth catchment, central Scotland. The importance of ‘low level’ data for achieving a wide geographical cover is emphasized. 3. Information collected between 1985 and 1994, now held by the Scottish Environment Protection Agency, was used to create a river classification scheme which allows the definition of trophic status using data on soluble reactive phosphorus concentration and algal abundance. Two thirds of the 3250 km of river were classified, showing that 74% of the river length had low nutrient concentrations and were defined as oligotrophic or mesotrophic. 4. Diffuse sources of phosphorus were found to be the most important factor determining the trophic status of rivers, with 71% of the river length controlled by diffuse inputs and only 7% by point sources. The importance of point sources increased with eutrophication; however, even in the most enriched category, point sources were thought to dominate the supply of nutrients in only 34% of the river length. © 1997 John Wiley & Sons, Ltd.     

Dermocystidium from cultured eels, Anguilla anguilla L., in Scotland

Abstract. An outbreak of Dermocystidium infection in cultured eels, Anguilla anguilla L., from Scotland is described. The disease appeared in the winter months but did not cause significant mortalities or adversely affect the growth of the eels. Infected eels had large, elongate white cysts on the gills. The cysts consisted of a homogeneous layer of parasite origin surrounded by a fibrous capsule and hyper-plastic epithelium. Within the cysts were small spherical parasite cells with a densely staining central area and peripheral granular, vacuolated cytoplasm. The cell wall appeared to be broken down in many cases and the cells appeared degenerate. The cysts eventually collapsed and the cavity was filled with epidermal tissue.     

The status and ecology of reefs of Serpula vermicularis L. (Polychaeta: Serpulidae) in Scotland

1. The distribution and abundance of reefs of Serpula vermicularis was examined in Loch Creran, the only known remaining site of reefs of this species in Scotland. In view of the decline in populations elsewhere, the aims included assessment of the importance of the Scottish population in terms of conservation of the reef habitat and the establishment of a baseline against which future changes could be gauged. A further objective was to determine appropriate conservation management of the reefs by examining the influence of both natural and anthropogenic factors. 2. Reefs were largely restricted to a depth range of 1–13 m. Factors controlling the depth distribution are discussed. 3. Serpula vermicularis reefs colonized a variety of substrata, but predominantly grew on lamellibranch shells on a seabed of muddy sand. There was some evidence that reef abundance was influenced by the availability of suitable substrata. 4. A belt of scattered reefs fringed much of the coastline of the loch with profuse reef development at two sites, where reef coverage exceeded 10% of the seabed. In terms of total abundance of Serpula vermicularis reefs, Loch Creran represents the major world site for reef development. It is concluded that the reefs of Loch Creran are of significant nature conservation importance and grounds for the establishment of conservation management are discussed. 5. Reef development is apparently curtailed in areas of strong currents and high flushing rate. There is evidence that human activity has adversely influenced reef growth through the discharge of organic factory effluent and the physical disturbance caused by mooring ground tackle. Scallop dredging also represents a significant threat to the persistence of serpulid reefs. Methods of minimising damage to this rare and fragile feature are discussed. © 1998 John Wiley & Sons, Ltd.     

Mytilus species under rope culture in Scotland: implications for management

Mussel (Mytilus spp.) production is one of the most economically important aspects of global aquaculture and, in Scotland, production has increased from 262 t in 1986 to 4,219 t in 2006. Until recently, mussel production in Scotland was considered to be based exclusively on the blue mussel Mytilus edulis, the native species. In Europe, production is known to consist of M. edulis and M. galloprovincialis, while a third less profitable species M. trossulus occurs in the Baltic Sea, where it is unexploited. In Scotland, the sympatric occurrence of M. edulis, M. trossulus, M. galloprovincialis and their hybrids in cultivation in Loch Etive has recently been reported, with significant losses in production attributed to the presence of M. trossulus. Samples of mussels were taken at three depths from 10 rope-farm sites in Loch Etive. The distribution of the Mytilus species and their hybrids in Loch Etive was investigated using the Me 15/16 nuclear DNA locus for species and hybrid identification. All three species and their hybrids were detected and the data were in agreement with the Hardy–Weinberg model suggesting panmixia. Frequencies of M. galloprovincialis and its hybrids were very low. Overall, M. trossulus (37%) was found to be more common than M. edulis (30%) and 23% of the sampled mussels were M. trossulus × M. edulis hybrids. Species distribution did not correlate with year of settlement nor with salinities taken at the time of sampling. There were significant differences in species distribution due to site location and depth, with M. edulis being more frequent at 8 m depth and M. trossulus more common at shallower depths. These differences might be exploitable in management strategies for continuing production, for example to decrease the prevalence of M. trossulus at shellfish farms in favour of the more desirable M. edulis.     

A seasonal survey of surface water habitats within the River Spey basin,Scotland: major nutrient properties

• 1. Current monitoring strategies of governmental organizations tend to be focused on relatively large flowing and standing waters, and until recently those polluted by point sources. Consequently areas of high conservation interest tend to be understudied, and defining reference conditions, as required by current legislation, is difficult to achieve.
• 2. In order to address this imbalance, water samples have been collected and analysed once in each of four seasons during 2003 from 72 locations within a 100 km² area of the oligotrophic River Spey catchment in NE Scotland. The sampling design included examples of running water (headwater streams and the main rivers) and standing water (lochs, lochans, pools, ditches, backwaters, bogs). Altitude ranged from 220 to 980 m and incorporated a climatic regime from cool temperate to sub‐alpine. Each sampling campaign targeted low‐flow conditions to evaluate steady‐state nutrient concentrations.
• 3. Concentrations of the major soluble nutrients nitrogen and phosphorus demonstrated high spatial and temporal variability, with soluble organic and molybdate unreactive forms generally being dominant. Concentrations of ammonium‐N, nitrate‐N and soluble reactive phosphorus were extremely small, with 50% of samples falling below 8, 5 and 1 µg L^?1, respectively, during spring and summer.
• 4. Sampling sites were grouped either by water‐body type or by the properties of their immediate biophysical zone. Together these two groupings explained 33–38% of the variance in water chemistry. Certain changes were detectable across most habitats and biophysical zones.
• 5. A decline in the concentration of nitrate that occurred in reaches downstream from certain headwater streams draining the mountain areas indicated the potential for its within‐stream utilization. Inorganic N dynamics differed between small streams and large rivers.
• 6. Landscape‐scale patterns were recorded in spring and summer nutrient availability with inorganic N and P thresholds (arbitrarily defined) of 10 and 1 µg L^?1, respectively.

Copyright © 2006 John Wiley & Sons, Ltd.     

Amphibian conservation in Scotland: A review of threats and opportunities

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The status of the freshwater pearl mussel Margaritifera margaritifera Linn. in Scotland

1. One hundred and sixty rivers in Scotland with historical records of freshwater pearl mussel Margaritifera margaritifera were surveyed between 1996 and 1999 for the presence of the species. 2. M. margaritifera populations were classed as either ‘extinct’ (no mussels remaining), ‘not currently viable’ (ranging from only dead shells present to no juveniles present, regardless of the number of adults found), or ‘functional’ (at least one juvenile was found, regardless of the overall numbers of adults present). 3. M. margaritifera populations could be classed as ‘functional’ in only 52 rivers (34% of total surveyed) and in only 17 of these were juveniles below 20 mm (5 yrs old) present. Furthermore, in only 10 of these functional rivers were mussels also still considered either to be common or abundant and these included both large easterly‐flowing rivers and small western rivers and streams. 4. In approximately two‐thirds (101) of the 155 rivers occupied 100 years ago, M. margaritifera is now extinct or is about to become extinct. Furthermore, analysis indicates that the rate of mussel population extinction has accelerated since 1970, with a recent average of two mussel river extinctions per year. 5. The predominant threat to the mussel populations has undoubtedly been pearl fishing. This has been occurring at every river, even in the most remote northwest areas, where most of the ‘functional’ populations remain. Recent legislation has provided full protection to M. margaritifera, so that all pearl harvesting is now illegal. 6. Locally, river engineering and host salmonid stock decline poses a serious threat and eutrophication has already eliminated populations in southern and eastern Scotland. 7. In every part of its global range, M. margaritifera has declined substantially and is now either threatened with extinction or is highly vulnerable. Based on recent estimates from across the species range, it appears that Scotland now probably holds at least half of the world's remaining functional M. margaritifera populations. Copyright © 2000 John Wiley & Sons, Ltd.     

A life table for powan,Coregonus lavaretus (L.) in Loch Lomond,Scotland: A basis for conservation strategy

1. A static life table for Loch Lomond powan, Coregonus lavaretus (L.) has been constructed from data obtained during 1980–1988, as a basis for monitoring any changes in the population which may ensue from exploitation of the Loch. 2. Mortality was 99.95% during the first year of life, and adult mortality highest at 5–6 years. 3. Average fecundity was 20.7 ova mm^?1 fork length. 4. Mortality and fecundity have not changed in 25 years. 5. It is not yet possible to assess the effect of the recent introduction of ruffe, Gymnocephalus cernuus (L.) into Loch Lomond, but their effect on recruitment into the vulnerable 0–1 year-class may be critical.     

Haemogregavina sachai n.sp. from cultured turbot Scophthabnus maximus (L.) in Scotland

Abstract. A new species of pathogenic haemogregarine is described from farmed turbot ( Scophthalmus maximus L.) as Hamogregarina sachai and its life cycle is demonstrated in its final host. An intralexicocytic schizogony followed by an intraerythrocytic schizogony was observed. This appears to be only the second time that a complete life cycle in the vertebrate host has been described for a marine fish haemogregarine.     

The Spawning of Perch (Perca fluviatilis L.) in Loch Leven, Kinross, Scotland

Investigations were carried out in 1979 and 1980 into the location of spawning grounds of perch in Loch Leven, the comparative intensity of their use and the duration of the spawning period. Spawning was found to take place in depths of 1–5 m and there was an indication that depths around 3 m are preferred. Silt and mud apparently inhibit spawning on exposed shores down to 2.5 m although natural shelter probably ameliorates this. Macrophytic vegetation is rarely present at the preferred depths, therefore, artefacts and artificial substrates must be most frequently used. Spawning started about 25 April in a ‘mild’ spring and about 9 May in a ‘cold’ spring. The duration of the spawning period was 4–5 weeks. A double peak in spawning intensity was found in 1979 and, if valid, could indicate a division of spawning fish into two groups, possibly by age as the peaks were not associated with the location of spawning sites. Although spawning tended to be more intense on the southern shore and around one of the islands almost any part of the loch down to 5 m may be used.     

Grey heron, Ardea cinerea L., predation at cage fish farms in Argyll, western Scotland

Abstract. The aims of the present study were to determine the number and age structure of grey herons, Ardea cinerea L., visiting a large freshwater cage trout farm in a study area in Argyll, western Scotland and to quantify heron predation at the site. Heron abundance was assessed on sea loch shores, running and standing freshwater bodies and at the trout farm between September 1985 and August 1987. Herons visited the farm almost exclusively at night or during twilight periods and, as a consequence, were seen more often by farm staff in winter than in summer. Herons selected cages containing small trout (<300g) and removed them from cages by standing on the top nets and fishing through the mesh. Stock losses were of two kinds; trout were either eaten directly or were dropped by herons during manipulation, when characteristic wounds increased susceptibility to disease or made the fish unmarketable. Adult herons were more successful at feeding than first-years and although younger birds spent more time feeding their intake rates remained lower than those of adults in terms of their total time at the farm. Within a cage, smaller fish aggregated closer to the surface than larger ones and so were more vulnerable to heron predation. In many cases, a high proportion of the fish attacked by herons were blind and/or in poor condition. By recording only wounded fish, farm staff considerably underestimated their losses to herons. Nevertheless, attacks sometimes appeared serious to farmers. However, such losses were small compared with other forms of fish mortality and loss.     

The impact of land-claim on macrobenthos,fish and shorebirds on the forth estuary,eastern Scotland

1. The impact of land-claim on the intertidal areas of the Forth estuary, eastern Scotland is described. It is shown that in recent times almost 50% of the intertidal area has been destroyed for a variety of purposes, including agriculture, harbours and industrial development. 2. The loss of infaunal invertebrate biomass and production from the intertidal habitat has been calculated for each part of the estuary, and by summation for the whole estuary. The loss is discussed in relation to the total biomass and production, both intertidally and subtidally, of the estuary. It is shown that proportionately more biomass and production may have been lost than area. 3. The impact of land-claim on estuarine fish is calculated. Land-claim has removed 24% of the natural fish habitats in the Forth estuary, and thereby removed 40% of their food supply. 4. The impact of habitat loss on birds was observed for one area where observations continued throughout a period of land-claim. For individual bird species at Torry Bay, land-claim had consequences ranging from neutral to substantially negative. Significant declines were found for overwintering populations of dunlin and bar-tailed godwit. Comparisons of pre- and post-land-claim bird feeding usage of this area, showed that the impact of land-claim on local bird populations differed between species. The large scale loss of habitat on the Forth seems likely to have reduced the size of some shorebird populations which overwinter on the estuary. 5. It is concluded that when considering the impact of land-claim on estuaries that, as found in some previous studies, a simple consideration of area lost may be inadequate to describe the effects of land-claim, and the consequences for animals living within the estuary may differ considerably amongst themselves and from area to area.     

Observations on open-water densities of sea lice larvae in Loch Shieldaig, Western Scotland

Sea trout (Salmo trutta L.) stocks on the West Coast of Scotland and Ireland have decreased due to reduced survival during the marine phase of their life cycle. Lice‐infested sea trout returning to rivers could indicate that parasite burdens are contributing to the decline. Salmon farms represent a potential source of substantial quantities of sea lice, leading to a conjectured link between parasites on salmon fish farms and infestations on wild sea trout. To investigate the potential infective pressure on sea trout in Loch Shieldaig, offshore and sub‐littoral plankton samples were collected and analysed for sea lice nauplius and copepodid stages. During the plankton survey, numbers of sea lice on a fish farm in the loch reached a maximum in November 2001. Soon after, numbers of sea lice larvae peaked in open‐water samples and then in sub‐littoral samples. Nauplii were found adjacent to the farm and occurred less elsewhere. This study reports a concentration of sea lice larvae at the head of Loch Shieldaig and indicates a possible relationship between sea lice numbers on the fish farm and lice larvae densities in the open‐water of the loch and in the sub‐littoral zone.     

Distribution of genetic variation in brown trout, Salmo trutta L., in Scotland

Abstract. A total of 1680 brown trout, Salmo trutta L., from 63 different localities in Scotland were sampled and examined for 34 loci. Thirteen loci were polymorphic in one or more populations. The mean observed heterozygosity for wild populations ranged from 0.0 to 8-9% (x=4.5%) in the same range as previous studies on this species. Within drainage studies and gene diversity analysis confirms that a large proportion (33%) of total gene diversity was distributed between populations. The Ldh-5(100) allele was common in Scottish populations and its distribution would fit the hypothesis that this allele was indicative of an ancestral trout population in Scotland before the invasion of trout characterized by the Ldh-5(90) allele. The results have important implications for the management of the brown trout genetic resource.     

Trophic polymorphism among Arctic charr Salvelinus alpinus L., from Loch Ericht, Scotland

Abstract— This article examines the morphology and ecology of Arctic charr Salvelinus alpinus in Loch Ericht, Scotland, Gill netting revealed that two forms of charr existed within the loch, a pale form and a colored form. Multivariate analysis of nine size-corrected morphometric measurements of the head region revealed that pale and colored charr differed significantly in the size and shape of the head characteristics and that both groups were easily discriminated on the basis of these characteristics. Stomach contents showed that the colored form fed predominantly on zooplankton and the pale form mainly consumed benthic macro-invertebrates, with larger pale individuals consuming other fish. On the basis of diet and morphology, the terms planktivorous and piscivorous were adopted for the two forms respectively. Length at age also distinguished the two groups, with piscivorous charr being smaller than colored charr up to age 8+ then surpassing the maximum length attained by planktivorous charr at ages of 9+ and above. The results are discussed in relation to other instances of sympatric morphs of Arctic charr.     

Entry of adult Atlantic salmon into a tributary of the Aberdeenshire Dee,Scotland

Upstream counts of adult salmon in a tributary to the River Dee during autumn and winter were examined over a 13‐year period using an optical fish counter. Statistical analysis indicated that salmon were mainly primed to enter the tributary at a particular time of year, peaking at early December. However, environmental factors also had a large influence. Entry of salmon was initiated by high flow rates in the main stem of the River Dee. Increases in water level in the tributary itself were not needed to stimulate the entry of salmon. Moreover, a change in flow from 1 day to the next did not result in a response from salmon. Rather, they reacted only after more than a day of flow increase. There was no consistent threshold level of flow that triggered tributary entry. The upstream passage of salmon was reduced at low temperatures (below 3°C). The numbers of salmon migrating upstream showed a gradual increase as the temperatures increased up to 11°C, and then sharply decreased at higher temperatures. Female salmon migrated earlier by about 2 weeks on average than males. Increasingly, counters and traps are being installed on spawning tributaries to examine the state of salmon stocks. Caution should be exercised, however, in using upstream entry data from individual tributaries to provide an overall assessment of salmon abundance, as local conditions in the tributaries may affect the salmon counts in particular years.     

Modelling the impacts of removing seal predation from Atlantic salmon, Salmo salar, rivers in Scotland: a tool for targeting conflict resolution

Abstract  Bioenergetics were used to model the potential impacts on adult Atlantic salmon, Salmo salar L., stocks and rod fisheries of removing harbour seals, Phoca vitulina L., from three rivers of different scales in the Moray Firth, Scotland, viz: the Spey (large), Conon (medium) and Moriston (small). Overall, seals had the greatest impact on the Moriston, where removal of a single animal could increase cumulative catch by 17% during the fishing season. On the Conon and Spey the impacts were negligible, and resulted in increased catches of <1% annually. On all rivers eliminating seal predation had the greatest impact during the spring due to the smaller size of spring salmon sub-stocks. A generalised model of seal removal illustrated that stocks and catches increased by >33% in rivers with monthly rod catches ≤10 fish, but declined to <10% for rivers with catches >34 fish. The outputs of the models are qualitative, but provide a management tool for targeting action to resolve seal-salmon fishery conflict. Smaller salmon population units, and spring salmon sub-stocks and fisheries in particular, are most vulnerable to predation. The merit of this approach is discussed regarding the management of Special Areas of Conservation for salmon and seals.