§ Lord Moranasked Her Majesty's Government:
What is the approximate annual mortality of O group Shetland sandeels attributable to (a) herring, (b) mackerel, (c) seals and (d) seabirds in each, or any of the last 10 years.
§ The Parliamentary Under-Secretary of State, Scottish Office (Lord Strathclyde)R. W. Furness (1990, Ibis, vol. 132, pp 205–217) estimated that during the period 1981 to 1983 the annual consumption of Shetland sandeels by seabirds was 47,000 tonnes, that140WA seals consumed 9,000 tonnes annually and that predatory fish accounted for 25,000 tonnes annually. A more recent estimate indicates that the biomass of sandeels eaten by seabirds in 1988 was 17,500 tonnes (Bailey et al 1991, ICES Marine Science Symposia 193 pp 209–216).
§ Lord Moranasked Her Majesty's Government:
How the abundance of (a) O group and (b) spawning age sandeels will be assessed for Shetland waters in the absence of data from the commercial fishery, which has remained closed this year; and whether such information will be sufficiently accurate to form the basis of future management decisions.
§ Lord StrathclydeThe Scottish Office Marine Laboratory has conducted surveys of sandeels at Shetland each August since 1984, with the exception of 1987. This has resulted in a time series of data which are independent of the commercial fishery and which can be used to provide indices of the abundance of O group and spawning age sandeels. These survey indices are sufficiently accurate to detect large scale changes in the population such as a recovery of the spawning stock. Any future management decisions are likely to be based on the results of these surveys as well as on any other relevant information on sandeel biology and abundance which may become available from other research work on sandeels at Shetland.
§ Lord Moranasked Her Majesty's Government:
Whether, in developing its models of sandeel populations in Shetland waters, an analysis has been carried out of the effects of variations in natural mortality on the estimates of (a) the abundance of O group fish, (b) spawning stock biomass, and (c) the stock recruitment relationship.
§ Lord StrathclydeThe models used in assessing the Shetland sandeel stock from commercial catch data assume a constant value of natural mortality at age. Adequate information is not available to allow account to be taken of actual variations in mortality. It is felt that the combination of information from surveys and models does however provide a satisfactory basis for fishery management decisions.