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One species of shrimp and sixteen species of brachyuran crabs are parasitized by rhizocephalans in Taiwanese waters. Ten of the crabs have never before been recorded as hosts of rhizocephalans. Eight species of rhizocephalans occur in Taiwan. Four species, Diplothylacus taiwanensis, D. calappae, Sacculina scutigera and S. docleae are new to science. The paper records the first example of simultaneous infection of the same host individual by two rhizocephalan species, and provides further evidence of successive moulting of the external mantle cuticle in several species of sacculinids.

Using the hard clam farms in Yunlin, Taiwan as examples, this study analyzes the effects of culture area, stocking density, and shrimp and fish polyculture on the cost efficiency (CE) of hard clam farming. A data envelopment analysis (DEA) is used to estimate the farms' technical efficiency (TE), allocative efficiency (AE), and CE values. The findings show that the mean TE, AE, and CE values of hard clam farms are 0.74, 0.57, and 0.43, respectively. The TE value is higher than the AE value, which indicates that cost inefficiency is mainly attributable to poor AE. Tobit regression results suggest that there are positive relationships between CE and both culture area and operator experience. Hard clam stocking density and age of the operators have negative effects on CE. Hard clam culture areas larger than 2 ha and a stocking density of 1.1-1.2 million hard clams per hectare have higher CEs than smaller culture areas and smaller or larger stocking densities. The use of sand shrimp, white shrimp, kuruma shrimp, and grass shrimp for polyculture and the use of milkfish and silver sea bream for polyculture are both associated with high CEs.The hard clam is one of the main types of shellfish cultured in Taiwan, and its output is highest among cultured shellfish. With an output of 34,755 MT in 2013, Yunlin County is the primary producer of hard clams in Taiwan: Yunlin contains the largest culture area in Taiwan, produces almost 60% of Taiwan's hard clam supply and yields output values as high as 77.25 million USD. Hard clam cultivation has become a 1 Correspondence to: jmlee866@yahoo.com.tw main source of income for the fishermen of Yunlin County.In the past, most Yunlin hard clam farms relied on monoculture. However, the growth of hard clam output has resulted in decreases in the price of hard clams in recent years. Consequently, farms must continuously increase the cost efficiency (CE) of hard clam culture to reduce costs and increase profits. improves the ecosystem balance of the culture ponds by reducing the quantity and precipitates of organic matter in the culture ponds (Smith 1985;Smith and Piedrahita 1988;Shpigel and Blaylock 1991;Yokoyama et al. 2002;Nhan 2007;Martinez-Porchas et al. 2010). Taiwan's hard clam farms primarily co-culture hard clams with milkfish, grass shrimp, sand shrimp, white shrimp, and kuruma shrimp. Recent increases in the demand for shrimp have increased the price of shrimp, which has prompted hard clam farms to increase the quantity of shrimp species in polyculture operations.Previous studies have successively researched the culture growth rate, culture environment factors, and disease control for the polyculture of shrimp, fish, and mollusk species (McLarney 1976;Costa-Pierce et al. 1984;Lui 1989;Zhang and Wang 1990;Lui et al. 1992;Chang et al. 1994;Yu et al. 1996;Handå et al. 2012). The polyculture of freshwater prawns and fishes is feasible in the USA (Buck et al. 1981;Costa-Pierce et al. 1984;Bessa Junior et al. 2012), and shrimp ponds have been used in the USA to overwinter c...

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