Standardisation of Size-Based Indicators for Broadbill Swordfish in the Indian Ocean (original) (raw)
Information on the size distribution, for example mean length, in the catch can potentially be used as an indicator of swordfish stock status. This study looked at the standardisation of such indices particularly for spatial and seasonal effects. Standardization of size-based indices smoothed temporal trends that were evident in the nominal data, largely by accounting for the significant effect of area. Nominal peaks in the early and late 1990s were dampened, such that the standardized indices showed no overall temporal trend. GLMs indicated a strong effect of area on the size- based indices that predominated over the quarterly effects. This is to be expected from a species with size-based spatial segregation. The lack of a significant quarter effect was consistent with the lack of evidence of seasonal swordfish spawning or migrations. An increase in the inter-annual variability in the proportion of large fish since 1990 was a feature of the combined data. The increased variability ...
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