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Page 1 - The data collection

PISCES has the largest inshore fish and crustacean abundance time series for a whole estuarine community available in the world. PISCES undertakes regular monitoring of the populations in the Severn estuary for the Environment Agency, British Energy and EDF. The purpose of this study is to build a long-term database of the abundance of fish and crustaceans in the region. The monitoring was started in October 1980 and monthly samples are still being collected.

The data set now comprises monthly abundance estimates for about 80 species of fish and 25 species of macro-crustaceans for a 35-year period. These data are used for a number of purposes including:
  • The monitoring of the abundance of rare and threatened fish such as the twaite shad.
  • Long-term monitoring of the effects of power station intakes.
  • Studies on the population dynamics of important estuarine species.
  • Studies on migration, recruitment and growth.
  • Predator-prey dynamics.
  • The study of climatic change.

Read the report of data from 2000 - 2001 or download more recent reports.

These data are available to teachers and researchers via the Dynamica software package. PISCES are pleased to quote for environmental studies for the Bristol Channel region. Using our extensive data we have produced reports for Bristol Ports, tidal barrage proposals and produced numerous scientific papers. Please contact us if you would like to use our data.

Data collection
Quantitative sampling commenced in 1980 when 24 h surveys of the diel pattern of capture were undertaken in October and November. From these surveys it was concluded that samples collected during daylight were representative of the 24-h catch. Regular monthly quantitative sampling at Hinkley Point started in January 1981 and is continuing. The total volume of water sampled over each visit is 324,000 m3. This volume has not varied over the entire period of study and is independent of environmental conditions.

To standardize for the tidal influence, all sampling dates are chosen for tides halfway between springs and neaps, with sampling commencing at high water (normally about 12.00 hrs). The fish and crustaceans are collected hourly from two screens for a 6 h period, identified to species and the number of individuals recorded. Water temperature and salinity are recorded monthly. Since 1987 the captured fish are weighed and their standard length measured. The filter screens have a square mesh of 10 mm thus small fish and crustaceans may not be retained. Long and thin fish such as pipefish or eels are more likely to be lost than wide fish such as flatfish. The adults of all inshore British species will be retained to some extent.

Read the report of data from 2000 - 2001 or download more recent reports.

Further information on our power plant-related work is available on our Power Station Effects website.

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