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.
The responses of habitat and fish communities to extreme hydrological and habitat disturbance in typhoon-prone mountain streams are not studied much. Such landscape–climate settings may provide a unique opportunity for fish to evolve without special habitat adaptation and involve different assembly rules compared to temperate regions. This study aimed to compare fish communities and habitat factors before and after the typhoon season and to test the influences of various aspects of habitat on fish assemblages between seasons. Fish and habitats were surveyed at 30 wadable stream sites in March and December 2010 in tropical southern Taiwan. Habitat variables differed between the pre-typhoon and post-typhoon seasons. Higher species richness and the total number of fish caught in the pre-typhoon season indicated fast recovery. Benthic fish were more vulnerable to typhoon disturbances than sub-benthic fish. Contrary to the original hypothesis, fish communities were more strongly related to physical habitats than water quality and riparian conditions. In addition, consistently high fish variance explained by habitat measures in the dry seasons indicated that environmental filtering predominated. Dominant fish species were related to main habitat gradients, characterized by low species richness but high beta-diversity. Our findings provide implications for fish conservation in typhoon-prone mountain streams.
Coastal wetlands have been gradually developed by aquaculture and other anthropogenic infrastructure, reducing the habitat for water birds. The traditional operation of shallow-pond milkfish (Chanos chanos) aquaculture in Taiwan may provide a model for aquaculture production that operates in harmony with overwintering water birds. The goal of this study was to test whether experimental water drawdown of aquaculture ponds, following the seasonal, traditional milkfish aquaculture, can create resource pulses that attract water birds in Tainan City in southern Taiwan. This experiment tested four types of aquaculture with potential for application: wild fish, no-feed tilapia, milkfish, and tilapia with feed. Ponds were surveyed every other day for water depth and water birds at least 37 times in four winters after water drawdown. In general, drawdown ponds created resource pulses that attracted higher feeding bird densities and numbers of species than control ponds in all aquaculture types. Milkfish ponds often had higher water birds in each year. Deep waders were sometimes the most abundant guild in the control, whereas shorebirds, shallow and deep waders were often higher in the drawdown treatment. Bird densities and numbers of species were correlated with water level, benthic biomass and water Chl a, but not with tilapia biomass. Species, such as Black-faced Spoonbills (Platalea minor), responded to water levels with the exception of Little Egrets (Egretta garzetta). The operation of seasonal, traditional shallow-pond milkfish aquaculture is suitable for foraging of water birds during the winter migratory bird season.
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