This study applies a translog cost function model to analyze the culture costs and the use of input factors among three groups of hard clam farmer households in Yunlin County, Taiwan, with different survival rates (low-intermediate, intermediate-high, and high). The study found that farmer household production in the three observed groups all exhibited economies of scale and could significantly expand the scale of production to lower the average cost. For farmer households with high survival rates, production cost could be reduced by 2.16% by a 10% increase in output.Moreover, the study shows that the survival rate-cost interaction values of farmer households in the intermediate-high and low-intermediate survival rate clusters were negative. Therefore, any increase in the survival rate could help lower the culture cost of farmer households. For low-intermediate farmers, the survival rate-cost interaction value was the most negative; any increase in the survival rate by 10% J World Aquacult Soc. 2020;51:139-158. wileyonlinelibrary.com/journal/jwas 139 would decrease the cost per hectare by NT$23,424. For high survival-rate households, seeding and capital were substitutes, and seeding and feed were complements. As such, farmers would reduce the use of seeding factors when increasing the use of capital and decreasing the use of feed. K E Y W O R D S economies of scale, elasticity of substitution, Meretrix meretrix, price and cost elasticities, survival rate, translog cost function 1 | INTRODUCTION The hard clam, Meretrix meretrix (L.), is an important commercial aquaculture species in Asia (Ho & Zheng, 1994; Jayabal & Kalyani, 1986). In Taiwan, it has the highest production output among all cultured shellfish species. The main cultured hard clam areas are mostly in counties and cities in western Taiwan, such as Changhua, Yunlin, Chiayi, and Tainan. In 2017, total hard clam production in Taiwan was approximately 52,062 m.t. Yunlin County has the highest production among all counties and cities in Taiwan, which reached 33,024 m.t. in 2017 and accounted for approximately 65% of the total production in Taiwan. The output value of the primarily family-run hard clam production in Yunlin County was close to NT$2.7 billion.In general, the cultured scale in Yunlin is relatively small, and its production cost often high. The size of culture ponds typically ranges from 1 to 3 ha with a unit production of approximately 11-15 m.t./ha, and a stocking density of approximately 1-1.6 million individuals/ha (Kuo, 2005). However, given the deterioration of the culture environment, climate change, and the high culture density, the production of cultured hard clams declined rapidly to 22,309 m.t. in 2016 with an output value of NT$1.1 billion. Moreover, a survey by Huang et al. (2018) shows that the survival rate of cultured hard clams in Yunlin County has declined from 70% to approximately 50% in recent years. Hard clam farmers have been advised to moderately reduce the stocking density of hard clams to enhance their survival and inc...