SGS Product & Process Certification - Marine Stewardship Council

short-term forecasts and setting TACs. However, the output can still be used to give sound
precautionary management advice in relation to stock status and sustainability. For example,
selectivity patterns in the UK fishery have already been used in simulations of increases in the
size at which bass are first exploited (due to a potential increase in MLS) to indicate the relative
magnitude of changes in yield to the various métiers and in the age structure of the underlying
bass population (M. Smith, Cefas, pers. comm.). The results were similar to and updated those
obtained by Pawson et al (2005), indicating that Y/R gains (and losses) with progressive
increases in the MLS (above 36 cm) were gear specific, but were likely to provide most benefit
to rod-and-line fisheries and least to trawl and net metiers.
3.3.3 Biological reference points
The common patterns in the recruitment time-series for sea bass ―stocks‖ in the North Sea,
English Channel, and along the west coast of England and Wales indicate that sea bass
populations around England and Wales are linked biologically (see Pickett et al., 2004) and/or
that recruitment is controlled by large-scale environmental patterns. It is known that warm or
cold summers and winters can have a considerable influence on the survival of 0-group bass
through their first year (Kelley, 1986), and that strong year classes are associated with higher
temperatures (Pawson, 1992; Pawson, 2008) rather than SSB. There is, therefore, no stockrecruit
relationship for bass that could be modelled, either to explain past or to predict future
recruitment patterns (Pawson et al., 2007b). The relative size of the spawning stock bears no
relationship to past recruitment over the period for which data are available (1984 – 2008),
which means that it has not been possible to set absolute or even relative reference points
based on stock-recruit considerations. There is, however, no sign of recruitment-overfishing,
and management decisions have been taken based on considerations of Y/R and MSY in
relation to exploitation patterns (essentially F-at-age, based on a good knowledge of biological
parameters and local fishing patterns).
3.3.4 Scientific background to management advice for sea bass
Research on the sea bass and its fisheries started in the 1970s, when recreational anglers in
particular began to be concerned for the future of the bass stocks around the coasts of
England, Wales and Ireland. What little was known of its biology was, nevertheless, sufficient
to indicate that protection of juveniles was bound to assist conservation of bass (Holden and
Williams, 1974). Though ICES established a study group in 2001 to respond to the European
Commission‘s request for information on sea bass fisheries, stock identity, assessment data
and conservation requirements in European waters (ICES, 2002), there was no assessment of
the size of the bass population - even in relative terms - and of its productivity and mortality
rates until 2003, and thus any restraint on exploitation (if this was necessary) could not be
justified on the basis of an analytical assessment.
In the UK, however, a scientific recommendation to increase the sea bass MLS above the then
current 26 cm (Holden and Williams, 1974) resulted in a dedicated research programme
initiated by Cefas in 1981, the publication of a summary of the results of which (Pawson and
Pickett, 1987) served as an aide memoir for forthcoming discussions and consultations on
management measures. This included a Y/R analyses that showed strong evidence of growthoverfishing
in many areas around English and Welsh coasts, owing to local fisheries targeting
3-5 year-old sea bass in and around harbours and estuaries. It was concluded that an MLS of
36 cm would satisfy the management objective of reducing growth-overfishing, whilst allowing
some important small-boat fisheries to remain viable.
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