OIL-TO-MEAL RATIOS OF PELAGIC FISH TAKEN FROM THE NORTHERN AND THE SOUTHERN BENGUELA SYSTEMS - SEASONAL PATTERNS AND TEMPORAL TRENDS, 1951-1993

The oil content of pelagic fish can be regarded as an environmental in dex which may help to predict recruitment. The present study provides a descriptive and statistical evaluation of monthly oil-to-meal ratios of pelagic fish landings processed at different ports of both the nor thern and southern Benguela systems, i.e. two in Namibia, four on Sout h Africa's west coast, and one on the South Coast. These time-series, and an aggregate of four western Cape ports, are described and analyse d statistically for seasonality, temporal trends and coherence between ports, covering the period since 1950/51. The seasonal signal was imp ortant at all ports, explaining about 25% of the variance and having a n amplitude of about 45% in relation to average. Both percentages were higher in the earlier part of the time-series. A significant negative trend was also apparent at all ports over the whole time-series, but it was manifested most strongly from 1980 to 1993. A model producing y ear-factors identified outliers in the time-series and these often coi ncided with known environmental anomalies. Also, cross-correlation sho wed highly significant coherence in the data from the northern and the southern Benguela but less coherence between the southern Benguela an d the adjacent South Coast. The extent to which the oil data reflect e nvironmental factors as opposed to fishing and technological factors i s discussed, and some associations with recruitment patterns are noted .