Squid stock fluctuations and water temperature: temporal analysis of English Channel Loliginidae

1. Monthly series of abundance indexes for the English Channel squid stock, based on fishery statistics of the United Kingdom (1980-93) and France (19 86-96), were compared with water temperature data. The two objectives of th e study were to test empirical predictive models and to analyse the stock-e nvironment relationship at various time scales; both correlation and time-s eries statistical techniques were applied. Sea surface temperature (SST) sh owed inter-annual fluctuations and month-to-month auto-correlation in addit ion to the annual cycle. 2. Trends in squid landings and temperature at the annual scale were found to be related, whatever the statistical method used (moving averages, cumul ative functions or regression using averaged data). 3. Variable selection applied in a 'multi-month' model suggested that fishi ng season indexes could be predicted from temperatures observed in the prev ious winter. The link between mild winter conditions and cohort success in winter/spring spawning species suggested that early life survival (and/or g rowth) was involved. This empirical model is a first step in the developmen t of environment-predicted recruitment indexes useful for management advice . 4. Seasonal decomposition was performed on both the squid resource data and SST data in search of short-term relationships. In spite of the flexibilit y of the loliginid life-cycle, no significant relationship was found betwee n squid seasonally adjusted indexes and temperature anomalies in the previo us months. This underlined the conclusion that temperature effect on cohort success was not constant throughout the year.