§ Mr. MorleyTo ask the Secretary of State for Scotland what progress has been made in identifying the cause of poor recruitment of sandeels in research into the Shetland sandeel population; and what evidence there is that this is due to natural factors operating in the first few months of life.
§ Mr. Michael ForsythSince poor recruitment to the Shetland sandeel population first occurred during a period of high spawning stock, it cannot be attributed to low egg production and must be the result of natural factors operating in the first few months of life. A research programme has been initiated to investigate the factors affecting the mortality and dispersal of larval and 0-group sandeels and the results of the first phase are currently being analysed.
427WThe seas around Shetland are known to comprise part of an hydrographic system which can greatly influence the larval dynamics for those fish species where adequate studies have been made—for example, herring. Studies have suggested that sandeel larval abundance in that area can be affected by changing hydrographic circumstances. In addition, studies in the north-west Atlantic suggest that where stocks of pelagic predators such as herring and mackerel were reduced then there was a congruent increase in the abundance of larval sandeels. Conversely, in the north-east Atlantic herring numbers have increased dramatically in the last decade. Herring are capable of being voracious predators of sandeel larvae and the overlapping distribution of the two stocks around Shetland may be relevant to sandeel recruitment dynamics.
§ Mr. MorleyTo ask the Secretary of State for Scotland how the distribution and abundance of 0-group, 1-group and breeding age sandeels in those areas of Shetland that have been studied in 1990, including Fair Isle, compare with surveys from previous years as revealed by research trawls; and if he will make a statement.
§ Mr. Michael ForsythTrawl survey data from fishing grounds around Shetland, including Fair Isle, can be used to give an indication of the relative abundance of 0-group, 1-group and breeding age (2+ group) sandeels. These data are summarised in the table.
Mean numbers of sandeel caught per 30-minute survey haul from grounds off Shetland, 1984 to 1990 Year Age 0 1 2+ 1984 891,898 47,592 48,198 1985 202,826 78,055 76,784 1986 683,044 56,653 36,878 1987 1— 1— 1— 1988 141,457 1,421 39,868 1989 863,181 9,283 11,974 1990 90,148 30,118 8,851 1 No survey in 1987. Preliminary analysis of the distribution of sandeels between the fishing grounds suggests that the distribution of 0-group fish in August 1990 was similar to that in preceding years and that the distribution of 0-group fish has changed little since the start of the surveys in 1984. Similarly, the distribution of 1-group fish is comparable to that in preceding years. The analysis suggests that the distribution of breeding age (2+) fish varies from year to year with little correlation in their distribution between years.
§ Mr. MorleyTo ask the Secretary of State for Scotland what are the main predators of 0, 1 and 2 group sandeels, respectively, in Shetland water; and what evidence Her Majesty's Government have for any changes in predation levels in the last 10 years.
428W
Deaths from Breast Cancer 1979–89, Males (1CD 91 175) and Female (ICD 91 174) Age 15–24 25–34 35–44 45–54 55–64 65+ Total 1979 Male 0 0 0 0 0 7 7 Female 0 17 73 217 261 608 1,176 1980 Male 0 0 0 0 0 3 3 Female 0 14 104 195 299 602 1,214
§ Mr. Michael ForsythThe main predators on these sandeels are seabirds, seals and fish. The limited data available on changes between years do not allow firm conclusions to be made.
§ Mr. MorleyTo ask the Secretary of State for Scotland if he will give the latest estimates for the level of recruitment for the Shetland sandeel stock for each year from 1984; what estimates were available for the same year in June 1988 and June 1989; and if he will make a statement.
§ Mr. Michael ForsythLevels of recruitment to the Shetland sandeel stock since 1984, as estimated by assessments made in the years 1988–90, are as follows:
Recruitment to Shetland sandeel stock, 1984–89 expressed as millions of 0-group on 1 July. Assessment 0-group recruits in year 1988 1989 1990 1984 29,188 27,065 21,212 1985 21,343 29,573 19,473 1986 19,451 48,955 24,924 1987 2,196 2,258 3,550 1988 20,750 1,273 6,440 1989 — 1— 25,327 1990 — — 1— 1 No estimate possible due to closure of fishery in second half of year. The assessments made in 1989 and 1990 used an improved method of analysis. In 1989 and possibly also in 1990, fishing was concentrated in areas where the older fish predominate, thus changing the exploitation pattern and disrupting the assessment. Also, and in recent years assessment has been inhibited by low fishing mortality in the Shetland sandeel stock.
§ Mr. MorleyTo ask the Secretary of State for Scotland what would be the current size of the Shetland sandeel spawning stock, according to current stock assessment models, had there been no fishing mortality since 1982.
§ Mr. Michael ForsythThere is a very wide number of possible models which might be used to predict spawning stock biomass in the absence of fishing mortality. A simple model which assumes recruitment in the absence of fishing is the same as that estimated to have occurred since 1982 predicts a spawning stock biomass for ages 2–5 of 23,600 tonnes in 1990.