Temperature studies on a river system in north-east England

A comprehensive temperature survey of the River North Tyne and its major tributaries is described. The maximum summer temperature of the main river increased downstream, and then remained more or less constant in the middle and lower reaches, whereas the minimum continued to rise throughout the length of the river. This general pattern was unaltered by flow rate, except in regions of almost stationary water. Mean water temperatures were low in winter, rose to a peak in July, and then fell during the remainder of the year. Throughout the year, three significantly different mean daily temperature ranges were demonstrated. The rate of change of temperature also varied seasonally, being greatest during July. A study of the major tributaries revealed certain differences, and these are discussed, particularly in relation to the importance of width and shading on water temperature. In conclusion, suggestions have been made concerning the possible influence of Kielder Water on downstream river temperatures.     

Peculiarities of the parasitofauna of Atlantic salmon parr (Salmo salar L.), brown trout (Salmo truttae L.), and char (Salvelinus alpinus L.) in the Utsjoki River system (Northern Finland)

Data on the parasite diversity in Salmonidae fish parr from different parts of the Utsjoki River obtained during 1993-1995 and 2006-2007 are presented. Three fish species, Salmo salar L., S. truttae L., and Salvelinus alpinus L., were examined on the presence of helminthes. Twenty species of salmon parasites were found, the majority of which are the parasites with complicated life cycles. Infusorians C apriniana piscium, myxosporidia Chloromyxum januaricus and Myxobolus neurobius, metacercaria of the genera Diplostomum and Apatemon, and the nematode Raphidascaris acus larvae were the most numerous in salmon parasite fauna. Brown trout had the most number of specific parasite species, whereas char was infested by protozoan parasites only.     

The systematics of the genus Lates (Teleosti: Centropomidae) in Lake Albert, East Africa

The systematics of thc genus Lares Cuvier, 1828 in Lake Albert were examined. It is concluded that the inshore form, originally described as Lates albertianus Worthington, 1929 and subsequently as L. niloticus albertianus should be considered as a synonym of L. niloticus (Linné, 1762) but that the offshore form, Lates macrophthalmus Worthington, 1929, warrants full systematic status. It had been relegated to subspecific status, L. niloticus macrophthalmus .
The lectotype for L. macrophthalmus is selected and redescribed. A method by which the species could have evolved, based on suspected differences in partial pressures of oxygen at which the blood haemoglobins of the two species become saturated, and on desiccation of the lake in the Pleistocene period, is described.
The diagnostic value of allometry in distinguishing between the two species on a morphological basis is discussed, as is the distribution of the two species in Lake Albert.
The possible significance of interspecific differences in the shape of the caudal peduncle and caudal fin is considered.     

The systematics of the genus Lates (Teleosti: Centropomidae) in Lake Albert, East Africa

The systematics of thc genus Lares Cuvier, 1828 in Lake Albert were examined. It is concluded that the inshore form, originally described as Lates albertianus Worthington, 1929 and subsequently as L. niloticus albertianus should be considered as a synonym of L. niloticus (Linné, 1762) but that the offshore form, Lates macrophthalmus Worthington, 1929,warrants full systematic status. It had been relegated to subspecific status, L. niloticus macrophthalmus .
The lectotype for L. macrophthalmus is selected and redescribed. A method by which the species could have evolved, based on suspected differences in partial pressures of oxygen at whichthe blood haemoglobins of the two species become saturated, and on desiccation of the lake in the Pleistocene period, is described.
The diagnostic value of allometry in distinguishing between the two species on a morphologicalbasis is discussed, as is the distribution of the two species in Lake Albert.
The possible significance of interspecific differences in the shape of the caudal peduncle andcaudal fin is considered.     

Some physical and chemical effects of the Cow Green (Upper Teesdale) impoundment

SUMMARY. The paper describes observations on water temperature and dissolved oxygen in Cow Green reservoir and also changes caused by impoundment to temperature, chemistry, dissolved oxygen and the discharge regime of the River Tees immediately downstream of the dam.
Impoundment and river regulation have considerably smoothed-out fluctuations in discharge of the Tees and have ehminated the very low and very high discharges which were characteristic of the natural river.
Reservoir water levels show an annual pattern of draw-down during summer, refilling in autumn and overflow during winter and spring. Tliermal stratification of the reservoir occurs rarely and is generally of short duration. Water temperatures at mid-reservoir correspond closely to those of water discharged from the reservoir. The temperature regime in the river downstream is modified as follows:

• (1)

  reduction in amplitude of annual temperature fluctuations by 1–2°C,
• (2)

  marked reduction of diel fluctuations, (3) delay of the spring rise in water temperature by 20–50 days and of the autumn fall by 0–20 days. These temperature changes could reduce the annual maintenance ration of a 10 g brown trout ( Salmo trutta L.) by about 15% and delay the annual peak of metabolism by about 1 month. The effect upon growth rate of trout would be negligible.

Fluctuations in ionic content at the reservoir inflow are comparatively large and can be related approximately to river discharge. Fluctuations at the outflow are smaller and appear to be largely seasonal. Regulation has not appreciably altered the dissolved oxygen content of the River Tees.     

Occurrence of an adult Atlantic salmon in the River Rhône, France

A large salmonid was caught in the commercial fisheries in the River Rhône (Mediterranean basin, France). Using morphological criteria and DNA analysis, the fish has been identified as an adult Atlantic Salmon Salmo salar .     

Assessing the status of British wild brown trout, Salmo trutta, stocks: a pilot study utilizing data from game fisheries

SUMMARY. 1. This paper describes an analysis of results from a questionnaire (Giles, 1987) which requested information on the status of game fish stocks (especially wild brown trout Salmo trutta L.) from those Game Conservancy members who own or manage fisheries. Also included are data arising from fishery log book records which are used to indicate trends in brown trout catch per unit effort (CPUE) over past decades.
2. The key finding from questionnaire returns was the widespread reporting of apparent declines of wild brown trout stocks in a total of twenty-seven sites throughout Britain. The affected waters are geographically widespread from the south-west of England through southern and south-east England, south Wales, northern England and Scotland including the Western Isles. Suspected stock declines of migratory (sea) trout, salmon Salmo salar L. and grayling Thymallus thymallus L. were also reported. Where brown trout occur alone, a significantly higher proportion of questionnaire returns recorded a stock decline compared with fisheries containing both brown and rainbow trout Salmo gairdneri Richardson.
3. Trout catch records from a small selection of differing fishery types are presented and the value of such data in fish stock assessment is discussed.     

Atlantic salmon straying from the River Imsa

Mean estimated straying rate for Atlantic salmon Salmo salar L. leaving the River Imsa as smolts during 1976–1999 was 15% for hatchery fish and 6% for wild conspecifics. Hatchery Atlantic salmon selected for production traits during four or more generations strayed >50%. The straying rate was higher for Atlantic salmon staying 2 rather than 1 year at sea before attaining maturity. For spawning, 96% of the strays entered streams within 420 km from the River Imsa, and c . 80% entered streams within 60 km of the mouth of the River Imsa, whether the fish were wild or hatchery released. Within the 60 km zone, the number of strays caught in a river increased with the Atlantic salmon catch in that river, but there was no significant relationship between straying rate and water discharge or distance from the river to the River Imsa. The observed straying rate of hatchery Atlantic salmon decreased with increasing number of fish entering the River Imsa. Sexual maturation as parr did not influence the tendency to stray. The results suggest that the establishment of temporary zones, free of fish farms, outside important Atlantic salmon rivers by the fisheries authorities in Norway should be large, whole fjords, to be effective.     

Conservation and management of brown trout, Salmo trutta, in Scotland: an historical review and the future

SUMMARY. 1. Intensive research into the life history of brown trout started In 1948 when the Brown Trout Laboratory was opened in Pitlochry. Over the next 15 years significant contributions were made to the brown trout literature upon which the Laboratory based advice to landowners and anglers wanting to develop their fisheries. 2. Increasing pressure from the government for more work on Atlantic salmon tended to divert research funds and time away from brown trout investigations. The International Biological Programme's major study at Loch Leven from 1966 to 1972 ensured a continuing interest in trout in standing waters. Over this period little attention had been paid to trout in rivers. This changed when a number of investigations were started on the River Tweed by Edinburgh University. 3. A major constraint to brown trout conservation and management has been illegal fishing and lack of records on stocking activities and catches. The granting of Protection Orders under the Freshwater and Salmon Fisheries (Scotland) Act, 1976, has been a major incentive to increased interest in the improvement of trout fisheries. 4. Brown trout stocks have been reduced in certain areas due to the effects of afforestation, acidification, land drainage and farm wastes. Various remedial measures have been proposed and implemented. 5. To meet the increasing demands for trout fishing, many loch and reservoir fisheries are now stocked with rainbow trout in preference to brown trout. Attention should be paid to the interaction of these two species in both standing and in running waters., where fish farm escapees and inadvisable releases go unrecorded. 7. Research into the genetic effects on wild stocks from the liberation of large numbers of hatchery-reared brown trout has been lacking and probably many ‘pure’ indigenous stocks have been lost. More work in this field is essential. 8. Proposals are outlined for future brown trout research and recommendations are made for better management. Suggestions are also put forward for changes in the legislation to further protect Scottish brown trout stocks.     

Migrations of sea trout, Salmo trutta L., from the Vardnes river in northern Norway

During the periods 1956–1963 and 1967–1970 traps were operated to catch upstream- and downstream-migrating sea trout, Salmo trutta L. A total of 15 788 sea trout were tagged, using Carlin tags. The number of recaptures made in the traps was 4481, of which 1796 were recaptured more than once.
The distribution of the 2122 recaptures in the sea provides a picture of the sea-migration pattern. Of the sea recaptures, 52.8% were reported as within a distance of 3 km from the river mouth, compared to 0.7% more than 80 km away. All the different size-groups of sea trout were represented among both the long-distance and the short-distance migrants. The results of this study of sea trout migrations are discussed in relation to the published results for Atlantic salmon, Salmo salar L., and sea charr, Salvelinus alpinus (L.), from the same river.
The four highest values recorded for mean distance of daily travel away from the river were 20, 8, 8 and 6km day⁻¹ by smolts and 6, 6, 5 and 5km day⁻¹ by larger-sized sea trout.
Recaptures of tagged sea trout in rivers other than the Vardnes totalled 506, of which 306 had been tagged as smolts. The calculated minimum percentage of stray is 15.5%. The proportion of sea trout from the Vardnes river that actually spawn in other rivers is not known. No significant difference in length distribution was found between the sea trout caught in the Vardnes river and those caught in other rivers. An hypothesis concerning the selective advantages of straying by anadromous salmonids living in small rivers is discussed.     

A mosaic disease of cowpea (Vigna sinensis Endl.)

A mosaic disease of cowpea ( Vigna sinensis Endl.), prevalent in the bean-growing regions of China, is described.
The characteristic symptoms of the disease are conspicuous mosaic patterns, deformation and distortion of leaves and stunting of the plant.
The cowpea mosaic virus is transmitted by Aphis rumicis L., Macrosiphum pisi Kalt. and Aphis gossypii Glov. It is also transmitted by artificial juice inoculation. The virus is seed-bome. It withstands ageing m vitro for 3 days at 220 C. Its inactivation temperature is approximately 62° C. its tolerance to dilution is about 1: 3000.
Cowpea mosaic virus infects lima bean and Adzuki bean in addition to cowpea.
The relation of this virus to cowpea mosaic virus described by McLean and asparagus-bean mosaic virus described by Snyder is discussed.     

Migration of wild and hatchery reared smolts of Atlantic salmon, Salmo salar L., through lakes

In 1982 and 1983 descending wild Atlantic salmon smolts, Salmo salar L., were caught in a fish-trap at the mouth of the River Imsa. Together with hatchery-reared smolts of the River Imsa strain they were tagged and released at three different sites of the Imsa-Lutsi watercourse: in the Imsa River 1 km above the trap, and in two lakes, 3 and 11 km upstream of the trap. The recapture-rate in the fish-trap decreased with increased migration distance. The hatchery-reared smolts migrated downstream faster than wild smolts. Lake-released smolts were considerably delayed in their downstream migration compared to the river released smolts. The results are discussed in relation to environmental and physiological parameters.     

The importance of the littoral epiphyton as food for commercial fish in the recent African man-made lake, Nyumba ya Mungu reservoir, Tanzania

Nyumba ya Mungu reservoir is a man-made lake in the Kilimanjaro region of northern Tanzania. The commercial fisheries are principally based on the cichlids, Sarotherodon pangani Lowe, S. jipe Lowe, S. esculentus Graham, and Tilapia rendalli Boulenger.
Examination of gut contents revealed that the dominant species, S. pangani and S. jipe , fed on the epiphyton attached to the vegetation in the littoral zone, S. esculentus was a phytoplankton filter feeder, and T. rendalli consumed macrophytes and associated epiphytes.
A fish exclosure quantitatively demonstrated that the epiphyton community was appreciably depleted by the grazing of fish. After 35 days the mean epiphyton density on the submerged surfaces of Cyperus articulatus L. within the exclosure was 285 times 10³ individuals cm^-2 shoot, but only 181 times 10³ individuals cm^-2 shoot on grazed surfaces outside the exclosure. The differences were statistically significant, and corresponded to a difference in biomass of about 6.5 g organic dry weight m^-2 lake surface. Vertical profiles of periphyton density on Cyperus indicated that fish grazed mainly below a depth of 100 mm from the water surface.
The littoral epiphyton → commercial fish food chain, which may be unique, is considered to predominate in Nyumba ya Mungu, and is compared with the major food chains of commercial fish in some other African natural and man-made lakes.     

Wild adult hybrids of Salmo salar L. and Salmo trutta L.

Ovarian development was impaired in three adult Salmo salar L. × S. trutta L. hybrids identified among adult salmonids in Scottish fisheries. Species-specific variation at enzyme loci indicated that the fish were F1 hybrids and mitochondrial DNA analysis showed them to be the progeny of S. salar females.     

Timing of Atlantic salmon Salmo salar smolt migration predicts successful passage through a reservoir

Around 30% of Atlantic salmon Salmo salar smolts successfully survived passage through Loch Meig, a reservoir in the north of Scotland, en route to the sea. However, this survival rate was in turn dependent on the timing of migration, with the earliest migrants in the spring having the best chance of survival. This could have implication for fisheries management, since the estimation of smolt downstream survival may be influenced by which time period of the smolt run is analysed.     

Effects of brown trout (Salmo trutta L.) stocking and catch‐release practice on angling catches in the River South Rena in southeast Norway

Preserving of fish species and populations is important whether it is for exploitation or just for conservation. Management of fisheries aim to maintain fishable stocks that are attractive to anglers, and different means are performed. In this study from the River South Rena in southeastern Norway, conducted during 1991–2005, the effects of supportive stocking of hatchery reared brown trout (Salmo trutta L.) from 1996, and bag limit (BL) and catch‐release (CR) practice for the target species brown trout, from 2002, were explored. Effects of supplemental brown trout stocking was not noticeable, except from one year following a year of exceptional high number of stocked fish, actually 41% of the catches, whereas in the following years this proportion remained constant about 10%, and the catches remained high in 2003 and 2004, mainly due to increased angling success rate after BL‐CR introduction.     

Stocking experiments with 0 + and 1 + trout parr, Salmo trutta L., of wild and hatchery origin: 2. Post-stocking movements

Wild and hatchery-reared 8–12-month-old (5–8 cm) trout, Salmo truttu L., were stocked into tributaries of the River Gudená. Movements were examined by means of electrofishing. Overall dispersal and upstream movement were greater for wild trout than for domestic trout. Maximum distance of movement was 600 m upstream for both strains and 600 m downstream for wild trout, and 700 m for domestic trout. Upstream movement started within 2 months from stocking and continued for at least 4 months. Downstream movement during the first few days after stocking, was more pronounced for domestic trout than for wild trout.     

Reproductive investment of female brown trout, Salmo trutta L., in a stream and reservoir system in northern England

Within the basin of Cow Green reservoir, upper Teesdale, the brown trout, Salmo trutta L., spend their first two seasons in running water. After this some females remain resident and others migrate to Cow Green reservoir. A cohort of 1000 females at age 2 that remains resident in tributary streams will, during the lifetime of the cohort, lay, on average, 3·0 times as many eggs as a cohort which resides in the reservoir. This conclusion is apparently not consistent with the observation that most females take up reservoir residence.
Reservoir females have a higher growth rate (Walford constant k=0·61, c.f. 0·86 for stream residents) and shorter life expectancy ( M year⁻¹= 1·19, c.f. 0·56) than the stream residents. However, they are of larger average size than the stream residents, lay larger eggs (mean 0·074 g, c.f. 0·066 g) and bury them more deeply (mean depth 11·0 cm, c.f. 8·5 cm).     

AN ECOLOGICAL STUDY OF THE ENCHYTRAEID WORM POPULATION OF SEWAGE BACTERIA BEDS LABORATORY EXPERIMENTS

This paper records the results of the experimental phase of an ecological study of the enchytraeid population of the sewage beds of the Huddersfield Corporation. The sewage in this drainage area is heavily charged with chemical wastes which have a marked effect on the fauna. Enchytraeus albidus Henle was the dominant worm while Lumbricillus lineatus Mull., the common bacteria bed-worm, was relatively scarce. The ability of these two worms to complete their life cycles in the sewage before and after treatment in particular beds was examined.
The crude Huddersfield sewage proved toxic to both E. albidus and L. lineatus but the former was much more resistant. After treatment in the beds the degree of toxicity was much reduced and the final sewage was harmless to all stages of E. albidus but the eggs of L. lineatus were still unable to develop in it.
The eggs of both species were less resistant to the toxic substances than the young worms; the adults were most resistant. High temperatures lowered toxicity by reducing the duration of the more susceptible early stages.
There was no evidence of physiological adaptation of L. lineatus to conditions in the Huddersfield beds. Wastes from both the main chemical works in the drainage area were examined and shown to be toxic; the domestic sewage was non-toxic. Both the distillate and residue of one of the chemical wastes proved toxic, especially the latter.
The toxicity could be entirely removed from the treated sewage by standing it over activated carbon for a few hours, or permitting slow oxidation for some weeks. The eggs of L. lineatus were used for these tests.
The Huddersfield sewage was very acid from time to time and the acidity reached was sufficient to kill young worms and adults of both species. But this factor was not considered important in the beds owing to the persistent effects of the toxic sewage.