River Exe Scale Reading Investigation. 6th Annual Report for the 1971 Season.

This is the 6th Annual Report of the Rive Exe Scale Reading Investigation for the 1971 Season by the Devon River Authority. The object of this investigation is to examine, by means of scale reading, the biology of age classes of the salmon population of the River Exe. It reviews the methods used for the collection of scales and examination of the materials. It shows the results of the survey and the number of scales studied from each of the various sea-age classes, time of running with distribution of the sea-age groups throughout the season, fish sizes and smolt ages at migration. All is summarized in tables, and figures are included showing weight distributions for each age classes and frequency distributions.

River Exe Scale Reading Investigation. 7th Annual Report for the 1972 season

This is the 7th Annual Report of the Rive Exe Scale Reading Investigation for the 1972 Season by the Devon River Authority. The object of this investigation is to examine, by means of scale reading, the biology of age classes of the salmon population of the River Exe. It reviews the methods used for the collection of scales and examination of the materials. It shows the results of the survey and the number of scales studied from each of the various sea-age classes, time of running with distribution of the sea-age groups throughout the season, fish sizes and smolt ages at migration. All is summarized in tables, and figures are included showing weight distributions for each age classes and frequency distributions.

Salmon Scale Reading Investigation 1972

This is the Salmon Scale Reading Investigation from 1972 by Cornwall River Authority. The object of this investigation is to examine, by means of scale reading, the biology of age classes of the salmon populations of the River Tamar, River Tavy, River Lynher, River Fowey, River Camel and River Plym. It contains for each river the numbers of caught salmon, number of scales received and which were unreadable and percentages in each age group separately for net and rod caught. Length and weight frequency distribution histograms have been plotted to show the size distribution of the various sea age group.

Rivers Taw and Torridge scale reading investigation. 8th annual report for the 1972 season

This is the Rivers Taw and Torridge scale reading investigation: the 8th annual report for the 1972 season produced by Devon River Authority in 1973. The object of the investigation is to examine by means of scale reading the biology of age classes of the salmon populations of the Rivers Taw and Torridge. The report is arranged in sections as previously and tables referred to in the report form an appendix. Scales were collected only from fish taken during the normal open season, which in 1972 was 1st April - 31st August. A weekly close time was in operation for the nets, a period of 60 hours from 6 p.m. on Friday evening to 6 a.m. on the following Monday. Thirty six licences for draft or seine nets were issued for the 1972 season and netsmen submitted samples of scales collected direct.

Underwater warp tension meter

A self-contained electronic solid-state instrument capable of measuring the tension between the different parts of a trawl net in operation, has been designed and developed for the measurement in the range 0 to 300 kg with an accuracy of ± 2 kg. The instrument is useful for measuring the resistance to motion of various accessories of a trawl net. It consists of an inductive type underwater tension transducer and an electronic indicating meter kept on board the vessel, both the units being connected by electric cable.

Portable electronic warp load meter

A portable type warp load meter has been developed for the use in fishing trawlers. The instrument enables to monitor the warp load in fishing trawlers accurately and easily without disturbing the routine fishing operations. The instrument can be used in several other places like cranes, bollard tests for marine engines, dry docks etc. especially when the operation has to be conducted easily without disturbing the load system. The information displayed in micro ammeter in the range 0 to 1000 kg can be fed to continuous recorders for detailed analysis and permanent records.

In situ temperature and salinity meter

Development of a portable self-contained electronic meter for on the spot determination of temperature and salinity is described. Instant and remote measurements of temperature and salinity of sea and estuarine waters in the range of 25-30°C and 30-35°C for temperature with an accuracy ± 0.05°C and 0-37‰ and 31-37‰ for salinity with an accuracy of ± 0.2‰ and ± 0.05‰ respectively are possible with the instrument. The temperature compensations of the salinity measurements are done manually with the help of temperature charts. The temperature and salinity measurements can be fed to continuous recorders.

Development of a torque meter for fishing vessels

The paper describes the development of an electronic instrument to measure the torque developed on the propeller shaft of fishing vessels at various speeds of the propeller. By measuring the torque, it is possible to determine the actual power transmitted from the engine gear-box unit to the propeller so that propeller efficiency can be evaluated and the optimum size of the propeller for a specific engine and vessel can be determined.