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Murase, H., Nagashima, H., Yonezaki, S., Matsukura, R., and Kitakado, T. 2009. Application of a generalized additive model (GAM) to reveal relationships between environmental factors and distributions of pelagic fish and krill: a case study in Sendai Bay, Japan. – ICES Journal of Marine Science, 66: 1417–1424. A generalized additive model (GAM) was applied to fishery-survey data to reveal the influences of environmental factors on the distribution patterns of Japanese anchovy (Engraulis japonicus), sand lance (Ammodytes personatus), and krill (Euphausia pacifica). Echosounder and physical-oceanographic data were collected in Sendai Bay, Japan, in spring 2005. A hierarchical model was used with two spatial strata: (i) presence and absence of each species; and (ii) biomass density of each species, given its presence; and six environmental covariates (surface water temperature, salinity, and chlorophyll, and near-seabed water temperature, salinity, and depth). The results indicate non-linear responses of the two indices to the environmental covariates. In addition, the biomasses estimated by the GAMs were comparable with estimates based on conventional, stratified-random sampling for each species. GAMs are very useful for (i) investigating the effects of environmental factors on the distributions of biological organisms, and (ii) predicting the distributions of animal densities in unsurveyed areas.

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Fishing gear usage in small-scale coastal fisheries of Pelabuhanratu Bay, Indonesia was explained by two approaches: temporal fishing gear allocation analysis and adaptive responses of fishers to external factors, especially climate and abundance of target species. Gear usage, with the exception of hand lines and seine nets, was more intensive during the dry season than the rainy season. The decision to use seine nets was governed by seasonal variability in the abundance of Auxis thazard, Lacepe`de, and Trichiurus spp. to the catch. Sustainable management of fishing activities in Pelabuhanratu Bay requires proportional reductions in the use of lift nets and fixed gillnets across the seasons rather than gear specific effort reductions.fishing gear allocation, Indonesia, seasonal dynamics, small-scale coastal fisheries.