The Portuguese oyster (Crassostrea angulata) is an important fishery resource in Taiwan. This study investigated oyster cultures at two locations along the coast of Taisi Township from March 2012 to July 2014. The average recruitment density, measured once every two weeks, of the oyster larvae was 256.4 ± 236.6 individuals/shell (N = 62) at site A and 118.5 ± 140.2 individuals/shell (N = 39) at site B. The average adherence density of the barnacle larvae was 187.1 ± 251.2 individuals/shell (N = 60) at site A and 60.9 ± 112.5 individuals/shell (N = 37) at site B. In Taiwan, C. angulata spawned all year. The primary spawning season was from March to September. The primary of adherence spawning season of barnacles was from March to October. Rainfall was the major factor that influenced oyster C. angulata and barnacle settlement, the eigenvalue of PC1 was 1.83 and could explain 61.0%. There are two main culturing seasons that move oyster larvae from coast of Taisi to farms in other places: from March to May and from August to September. Although the oyster larvae are more abundant in spring, fishermen prefer harvesting the larvae in autumn to avoid the typhoon season (July-September).
The effects of benthic fish on stream benthic resources and communities have not been effectively studied in subtropical East Asia. This study examined the effects of the Acrossocheilus paradoxus benthic fish on benthic resources and communities in Jiaolong Creek, Central Taiwan. A cage experiment with a no-fish control and a fish treatment was used to study the effects of A. paradoxus on the mass of algae and detritus and on the density and community structure of algae and macroinvertebrates. Additional diets, nutrient excretion rates, and feeding scars of this fish were also examined. A. paradoxus fed primarily on algae and detritus. The fish treatment had lower chlorophyll a, phaeophytin a, and ash-free dry mass than the no-fish control. Areas of concentrated feeding scars by A. paradoxus had consistently lower chlorophyll a than adjacent non-feeding areas. The mean density of macroinvertebrates was lower in the fish treatment; however, the taxa richness and diversity were higher. Algal and macroinvertebrate communities differed between treatments. A. paradoxus altered the benthic resources and communities in this study.Abbreviations: AFDM, ash-free dry mass; ANOVA, analysis of variance; MRPP, multiple-response permutation procedure; NMDS, non-metric multidimensional scaling.
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