New Developments in Ultrasonic Fish Tracking

SynopsisA range of small, long-life ultrasonic fish tags is described and their use illustrated with an improved system of fixed hydrophone tracking stations. A boat-mounted hydrophone system giving bearing and range estimations for use in open-water fish tracking is described together with a portable handheld unit for simple location of tagged fish in rivers, etc. Typical results based on intensive use of these systems are given.

The Distribution and Prevalence of Infectious Pancreatic Necrosis Virus in Wild Fish in Loch Awe

SYNOPSISA 3-year survey of wild fish in Loch Awe and the surrounding watershed has shown a restricted distribution and low prevalence of infection with infectious pancreatic necrosis virus. No signs of clinical disease were observed in infected fish. The restricted distribution close to a rainbow trout farm is consistent with the virus originating from this farm, where virus infected stocks have been found each year since 1971. The continuing low prevalence is also consistent with virus in wild fish resulting from the spread of infection from the farm. If infection is spreading between wild fish, it is slow within the time scale of the survey. The possible mechanisms of transmission of infection from the farm to wild fish are discussed.

Genetic Improvement in Salmonids

There is considerable interest in the cultivation of salmonids in several countries. In Norway it is now a question of rate of expansion rather than a question of whether this industry will develop or not. Interest is turning more and more towards sea farming based on Atlantic salmon rather than on rainbow trout.One of the most important economic factors in fish fanning is the producing ability of the fish. It is essential for the future expansion of fish farming that one develops a more productive animal which is better adapted to captivity.

Rumen Micro-organisms in Red Deer, Hill Sheep and Reindeer in the Scottish Highlands

SynopsisThe micro-organisms in rumen samples from Red deer, hill sheep and reindeer grazing their natural pastures in the Scottish Highlands were examined at different seasons over a number of years. The total counts of bacteria and protozoa varied with the season, and were lowest in winter when fermentative activity was also at its lowest.As is usual in roughage-fed ruminants, viable counts were only a very small proportion of the total counts. The reindeer rumens had the highest concentrations of bacteria.There were no consistent differences in the types of bacteria between seasons, but although there were no bacteria peculiar to any animal species the balance of predominant types varied between the species. The principal types of bacteria were similar to those found in domesticated ruminants. The numbers of protozoa in the Red deer were higher than those in the sheep, and the concentrations in reindeer were higher than those generally reported for domesticated cattle or sheep. A number of species of protozoa were found in each animal and the predominant species differed in the different animals.

Salmon Farming—An Industrial Research Approach

SYNOPSISThis paper describes an industrial research approach to fish farming and illustrates where appropriate how it differs from the research strategy employed by universities and governmental bodies. To illustrate this the Unilever experience of the establishment of salmon farming from a research concept to a production and marketing operation is discussed in detail. Three separate phases in the process of establishing industrial fish farming were undertaken and were entitled ‘Biological, Technological and Commercial’. The research programme involved in each of these phases is described in detail.The salmon farming cycle which was arrived at after the biological phase is described in detail. The technological phase involved the translation of this biological phase into a viable farming operation. This enabled a computerised cost model of the salmon farming process to be built. This identified the six or seven crucial areas which had to be improved if the enterprise was to be profitable—the commercial phase.To demonstrate the way the nature of the research programme has changed during the period 1968–76 a graph is given showing the main discipline involved in each year and how these have changed over that period.

Production of Larval Tanypodinae (Insecta: Chironomidae) in the Mud at Loch Leven, Kinross

SynopsisLife histories and production of the five common species of Tanypodinae (Pentaneura monilis, Procladius simplicistilus, P. crassinervis, P. choreus and Psilotanypus rufovittatus) in the mud at Loch Leven were measured from March 1971 to March 1972. The methods used to identify each species of larva are described. All were univoltine except Pentaneura monilis which had two generations per year, but the seasonal patterns of the life cycles were different. The average density of third and fourth instar Tanypodinae was 3100/m2 and densities of individual species exceeded 2500/m2 for short periods in Procladius crassinervis and P. choreus. Net annual dry weight production by this subfamily was 2·6 g/m2(57 kJ/m2), with individual species ranging from 1·1 g/m2 (P. crassinervis) to 0·16 g/m2 (Pentaneura monilis). These results are discussed briefly and compared with production estimates for other zoobenthos.

Recent Technical Advances in Marine Flatfish Farming

SYNOPSISProgress in the development of marine flatfish farming suggests that, for two species, commercial viability is becoming a real possibility.Dover sole can be reared in tanks on shore supplied with warmed water from the cooling of coastal power stations. Turbot can be reared likewise, or in cages floating in the sea.The main area in which problems remain is in the controlled production of juveniles in hatcheries on shore, but recent progress has been good.There is a good potential in the UK for marine fish farming, with probable sites available for an annual output of all species of up to around 50,000 tonnes p.a. At this level, or even at 25% of this level, the requirement for the catching of fish as farm fodder would become significant to the fishing industry.This paper describes only those aspects of progress or outstanding problems which, in the author's opinion, are of major significance in economic terms.